Theses and Dissertations Collection

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Prevalence, mean intensity and pathology of ectoparasite infections in nile tilapia (oreochromis niloticus) in aquaculture production systems in Morogoro urban and rural areas, Tanzania
(Sokoine University of Agriculture, 2008) Mtenga, Coletha Mathew
A cross sectional study was carried out between September 2007 to September 2008 in order to investigate the prevalence, mean intensities and pathology of ectoparasite infections on the gills and skin of Nile tilapia (Qreochromis niloticns) in selected ponds in urban and rural areas of Morogoro, Tanzania. Pond area, fish size and water quality were also determined. On-farm oral interviews using structured questionnaire were carried out on each farm involved in the study to establish management practices. Two types of ectoparasite namely: Trichodina species and Monogeneans were identified. Trichodina spp were more prevalent (P < 0.001) than Monogeneans. Gills were the most affected organs than skins with a high number of parasites as well as pathological damage to the tissues (P < 0.001). Main pathological lesions observed on the gills were hyperplasia, sloughing and necrosis of the lamellar epithelium, clubbing and fusion of secondary lamellae. The physico-chemical parameters of water in the ponds and management practices were different from one another in the study area; however, there was no strong correlation between water quality and parasite prevalence and mean intensities of the parasites. Prevalence and mean intensities of parasites in fish varied in different ponds with some ponds having very high prevalence and mean intensity and others with very low. This might be explained by the different management systems based on the knowledge the farmers had on fish husbandry and different weather conditions in the study area. There were significantly higher parasite infections in fish in the urban than in the rural areas (P< 0.05). The overall prevalence in the study area was 68% and on average the mean intensity was 5.3. The ectoparasites seem to pose a threat to the aquaculture industry in Morogoro urban and rural areas as observed in this study. To rescue the situation, educational intervention and further research on tilapia parasitic diseases is needed. Farmers have to be trained on proper husbandry and good management practices of fish farming. There is also a need for the government to promote aquaculture as the country has a great potential for it.
Studies on the effects of trypanosoma congolense infection on the reproductive function of the ram
(University of Glasgow, 1993-12) Mutayoba, Benezeth Mugyabuso
This thesis describes a series of studies carried out in Scottish blackface rams experimentally infected with Trypanosoma congolense stabilates 57/10 and 57/11 (originally imported from ILRAD, Kenya as ILRAD 1180) with the primary aim of determining the effects of infection on the function of the hypothalamo-pituitary-gonadal axis. The studies also investigated the possibility that pyrexia is responsible for inducing gonadal endocrine and exocrine dysfunctions in infected animals. In addition the effect of infection on the function of the hypothalamo-pituitary-adrenal (HPA) axis was assessed in order to determine whether reproductive dysfunction generally seen during trypanosomiasis is related to stress caused by the infection. Chapter I comprises an introduction and a literature review on trypanosome- induced reproductive dysfunctions with emphasis on pyrexia and changes in the HPA axis. Chapter II describes the two experiments carried out in rams infected with T. congolense and the general materials and methods used in these studies. Chapter III describes the effects of infection on semen characteristics and pathology of various reproductive organs such as the testis, cauda epididymis, prostate and pituitary gland. It was found that T. congolense induced a progressive deterioration of semen quality in terms of an increased percentage of abnormal spermatozoa in the ejaculate. Progressive non-inflammatory degenerative changes were observed in the testis and prostate gland. The cauda epididymis showed varying degrees of decreased sperm reserve. Trypanosome-induced pyrexia led to an elevation of scrotal temperature in infected rams, suggesting that the changes in the gonads could have been due to increased testicular temperature. Indeed, similar changes were observed in the semen and gonads of uninfected rams following artificial elevation of testicular temperature by scrotal insulation. The pituitary gland showed changes associated with increased basophilic degranulation in infected rams. Changes in plasma concentrations of reproductive hormones in the same rams are described in Chapter IV. It was observed that soon after the onset of parasitaemia, which occurred within 1-2 weeks of infection, plasma testosterone concentration declined and levels remained low throughout the infection period. This reduction in plasma testosterone concentration was associated with a progressive and marked decline in testosterone pulse amplitude and testosterone secretion after injection of gonadotrophin-releasing hormone (GnRH) was also depressed throughout the infection period. By four weeks after infection, declining plasma testosterone concentration was accompanied by a significant increase in plasma luteinizing hormone (LH) pulse amplitude and increased pituitary responsiveness (LH secretion) to exogenous GnRH. As the infection progressed up to 8 weeks, the plasma LH concentration declined. This could not be associated with some aspects of gonadal steroid feedback as similar LH changes were observed in infected rams which had been castrated. Neither was the decline in plasma LH concentration caused by the inability of the pituitary gland to secrete and release LH as secretion of LH in response to exogenous GnRH was not impaired throughout the infection period. It was therefore concluded that the decline in plasma LH concentration after 8 weeks of infection was possibly induced by a progressive impairment of the ability of the hypothalamus to synthesize and/or release GnRH. Gonadal steroidogenesis in infected rams was investigated in the in vitro experiments described in Chapter V. This work showed that the alteration in plasma testosterone concentration following infection was associated with a decline in Leydig cell steroidogenesis, possibly mediated by increased testicular temperature affecting testosterone biosynthetic enzymes. However, by 4 weeks after infection, reduced plasma testosterone in infected animals was exacerbated by the impaired ability of the testes to release testosterone into the circulation resulting in a significant increase in intratesticular testosterone content. A similar increase was also observed in scrotal- insulated rams and it was therefore suggested that changes in intratesticular testosterone in infected rams at 4 weeks of infection was associated with a trypanosome-induced increase in testicular temperature perhaps through an effect on testicular blood flow. The effects of T. congolense infection on the function of the HPA axis in rams and the relationship between this and the changes in the hypothalamo-pituitary-gonadal axis are described in Chapter VI. The onset of parasitaemia stimulated a significant increase in plasma cortisol concentration which was followed within 3-6 week of infection by a decline in plasma cortisol levels and a reduced ability of the pituitary to secrete adrenocorticotrophin hormone (ACTH) after injection of corticotrophin-releasing hormone (CRH). Thereafter, the activity of the HPA axis was increased in step with the fluctuating parasitaemia. CRH stimulation of the HPA axis had no effect on LH secretion but reduced the plasma concentration of testosterone indicating the possible aggravation of T. congolense-induced reproductive disorders by stress-induced cortisol. The general discussion and conclusions drawn from all the experiments are. presented in Chapter VII. It can be concluded that T. congolense causes a very profound dysfunction of the hypothalamo-pituitary-gonadal axis in rams through actions at various sites. These effects may be partly associated with trypanosome-induced pyrexia and are exacerbated by increased plasma cortisol concentrations resulting from the activation of the HPA axis.
Porcine cysticercosis in Angonia district, North-Western Mozambique: epidemiology and evaluation of the effectiveness and efficiency of oxfendazole treatment
(Sokoine University of Agriculture, 2010) Junior, Alberto Pondja
A research was conducted to investigate the epidemiology of porcine cysticercosis in Angonia district, Mozambique, and to evaluate the effectiveness and efficiency of oxfendazole (OFZ) for the treatment of porcine cysticercosis. Prevalence and risk factors associated with porcine cysticercosis were determined in a cross-sectional survey conducted in 11 randomly selected villages. Out of 661 pigs screened, porcine cysticercosis was diagnosed in 12.7% and 34.9% by lingual examination and Ag-ELISA, respectively. Increasing age (OR = 1.63; 95% CI: 1.13, 2.37) and free-range pig husbandry system (OR = 3.81; 95% CI: 2.08, 7.06) were significant risk factors associated with the disease. The incidence of porcine cysticercosis was determined in a study conducted in 4 endemic villages. A total of 108 piglets were tested repeatedly for porcine cysticercosis (by Ag-ELISA) at 4, 9 and 12 months of age. The incidence rate of porcine cysticercosis increased significantly from 3.8 cases per 100 pig-months in the first period (between 4 and 9 months of age) to 19.3 cases per 100 pig-months in the second period (between 9 and 12 months of age). The effectiveness and efficiency of 30mg/kg dose of OFZ for the treatment of porcine cysticercosis were evaluated in a randomized control trial that involved 216 piglets. Fifty four piglets were treated at 4 months of age (OFZ-T1), other 54 piglets treated at 9 months (OFZ-T2) and matched with 108 controls. Baseline prevalence (by Ag-ELISA) was similar among the study groups. At 12 months of age, infections were found in 66.7% controls, 21.4% OFZ-T1 and 9.1% of the OFZ-T2 pigs. There was a significant risk reduction for cysticercosis if pigs were treated either at 4 months (OR = 0.14; 95% CI: 0.06, 0.34) or 9 months of age (OR = 0.05; 95% CI: 0.01, 0.15). Treating pigs with OFZ resulted in positive incremental net benefits. Porcine cysticercosis is endemic in Angonia district. Oxfendazole treatment is cost-effective, and combined with health education programs would have a significant contribution to the control of Taenia solium transmission. Further studies are needed to fine-tune the use of OFZ into a more practical field control tool for porcine cysticercosis.
Study on congenitally acquired Plasmodium Falciparum infection in neonates in Muheza district, Tanzania
(Sokoine University of Agriculture, 2006) Mwangoka, Grace Wynn
The study aimed to determine if infants diagnosed with malaria parasites in the age below three months acquire the infection congenitally from their mothers through the placenta. Placenta blood, cord blood samples and blood from infants born of mothers diagnosed with placental malaria by blood smear and presented clinical malaria below three months of age were examined by PCR amplification, PCR-RFLP and sequenced. Prevalence of Plasmodium falciparum by PCR in the placenta and cord were 9.2% and 65%, respectively and 18 (19.1%) of infants born from mothers diagnosed with placental malaria developed clinical malaria below three months of age. Placental blood and cord blood sample, and placental blood and blood samples of infants below three months that shared the same band size by PCR and fragments size by PCR-RFLP were considered to be genetically related. Though sequencing results confirm differently that, sharing band size and fragments size between samples does not confirm that the parasites are genetically related. Six pairs (40%) out of 14 pairs of placental blood and cord blood samples that shared band size and fragments size, after sequencing were genetically unrelated while eight pairs (60%) were genetically related which is an indication of transplacental transmission of malaria parasites to the cord. One pair (14.3%) of sequenced placental blood samples and blood samples of infants below three months were genetically related. This showed that the malaria parasite that crossed from the placenta to the infants through the cord caused congenital malaria. Over three-fourths (79.8%) of newborn infants delivered from mothers with placental malaria were below normal gestation age and 14.9% of newborn infants had low birth weights. Some 42.5% of primigravidae were found to be parasitized with P.falciparum in the placental. A higher proportional of infants from primigravid were frequently infected with malaria while infants from multigravid observed to acquire malaria infection early in life. Placental malaria, which leads to cord malaria, observed to significantly decrease (P <0.001) as gravid increases.
Prevalence, risk factors and genetic relatedness among thermophilic campylobacters from humans and chickens using rapd-pcr in Morogoro, Tanzania
(Sokoine University of Agriculture, 2009) Chuma, Idrissa Shomari
jejuni and 5% of C. coli were100% similar. Conclusively, zoonotic thermophilic Campylobacter infections existed between humans and chickens in Morogoro municipality. Besides chickens, the role played by other domestic and wild animals in transmitting thermophilic Campylobacter infections to humans particularly children, should be closely examined. jejuni and 5% of C. coli were
Attitudes towards animals and their welfare among cattle keepers in Morogoro and coast region in Tanzania
(Sokoine University of Agriculture, 2014) Burashi, Wilbert Vitus Joseph
Investigation of knowledge on essential needs of animals, reactions of cattle keepers towards farm and other domestic animals with the aim of determining attitudes and perceptions towards animals and their welfare in Tanzania. Comparison was done between traditional and peri-urban backyard dairy cattle keepers. Primary and secondary data was collected through questionnaires, focus group discussion and on site observation. The findings show that in both groups, awareness on animals’ welfare was recognized but they differed in aspects like disease prevention, input associated with welfare and attitudes towards handling and treatment of farm animals. However, the way cattle, dogs and cats were treated seems to differ between peri-urban and traditional cattle keepers. Poor treatment of cattle was observed in traditional group especially on aspects of dipping, vaccination, deworming and additional feeds such as concentrates, fodder and water supply. Low level of education, poor knowledge and little exposure on animal welfare were the key factors for the bad treatment of animals. Comparatively, cattle were cared more than dogs and cats in both sectors because of economic benefits. Therefore, due to the importance accumulated from the livestock sector to the economy of individual farmers and the country, the welfare of animals need to be advocated with all efforts. Good trained professionals working to reduce animal suffering should implement animal welfare laws, policies and practices. Educational campaign, seminars and workshops should be used to promote animal welfare issues. The Ministry of livestock and fisheries must take this as an important issue for good products of animals and for the benefit of the country.
Ultrastructural study of brain with experimental cowdria ruminantium infection (heartwater)
(1991) Mwamengele, George L. M.
Heartwater is an infectious, vector-borne, non-contagious disease of ruminants caused by Cowdria ruminantium. The etiologic agent is an obligate, intracellular parasite infecting phagocytic cells and, particularly, vascular endothelium. Transmission is effected by a three- host tick of the genus Amblyomma. Clinically, the disease is characterized by fever and signs of central nervous system disorder. There is general agreement on a deranged transport mechanism across the vascular wall as the basis for the development of morphologic lesions and clinical signs, but the actual mechanism of damage is poorly understood. Previous ultrastructural studies are few and have mainly been concerned with the parasite itself. The present morphologic study of the cerebral microvasculature is an attempt to elucidate the pathogenesis of the central nervous system changes. Five, clinically healthy, adult, Danish goats were used to establish the optimal procedure for perfusion fixation of the brain and, at the same time, to serve as normal controls. The animals were put under general anesthesia with pentobarbitone intravenously at 25 mg/kg and placed in dorsal recumbency. Following dissection of the ventral neck region intubation was performed and carotid arteries were isolated. Heparin (1250 i.u./kg) was injected and perfusion done through one of the carotid arteries using 3% phosphate-buffered glutaraldehy de solution at pH 7.4 and 500 mOsm. The best perfusion results were achieved with the tank placed 1.5 m above the heart. The brain was removed and 1 mm3 samples were diced from the best fixed areas of the cerebral and cerebellar cortices and further fixed i 3% glutaraldehyde solution. Some of the samples were routinely processed and stained for transmission electron microscopy. In an attempt to improve fixation and enhance demonstration of cellular membranes and other structures, other samples were subjected to alternative processing and staining regimes including reduced osmium tetroxide, ruthenium red, tannic acid, and uranyl block staining. On balance, however, these regimes did not produce entirely satisfactory results and were therefore omitted in the experimental studies. Corresponding pieces of brain tissue were post-fixed in 10% neutral, buffered formalin and routinely processed for light microscopy. A complete necropsy was performed and various tissues were taken and similarly processed for light microscopy. Fourteen Tanzanian blended goats were experimentally infected by intravenous inoculation with the Ball 3 strain of Cowdria ruminantium. Following an incubation period of about 2 weeks the animals developed temperatures up to 41.7°C. Other clinical signs included bleating, loss of appetite, loss of body condition, listlessness, abdominal respiration, stupor, head tremors and ataxia. In 2 goats, fits, opisthotonus, paddling movements and lateral recumbency were also observed. When temperatures started to drop the animals were killed and subjected to the same procedures as the controls. Necropsy revealed mild hydropericardium (2-13 ml) and splenomegaly in all 14 goats. Other, inconstant findings were urine retention in bladder, subepi- or subendocardial petechiae and flabbiness of the heart. In areas of incomplete perfusion leptomeninges appeared hyperemic. Light microscopically, Cowdria organisms were found in vascular endothelium of the brain in 8 goats. Focal perivascular mononuclear cell infiltrations, sometimes extending into the adjacent neuropil, were present in the brains of 12 animals. More extensive mononuclear cell infiltrations, occasionally with a few eosinophils, were in the leptomeninges of 11 goats. Focal mononuclear cell infiltrations were also found, although variably, in pulmonary and renal interstitium and in subepi- and subendocardial locations. All experimental animals ex hibited moderate hyperplasia of splenic lymphoid tissue. The only ultrastructural change of parasitized endothelial cells was compression and displacement of cytoplasm and organelles by membrane-bound colonies of Cowdria organisms. Perivascular accumulations of cells, consisting of macrophages, lymphocytes and occasional plasma cells, were invariably associated with non-parasitized segments of capillaries or venules. Often intravascular mononuclear cells were seen adhering to the endothelium with portions of their cytoplasm dipping into the endothelial cell membrane or interposed between the endothelial cell and the basement membrane. Large, spherical, electron-dense inclusions, often several in the same cell, were found in pericytes, both in control and experimental animals but with a notably higher incidence in the latter. Similar inclusions as well as smaller inclusions with the features of lipofuscin were seen in perivascular macrophages. An additional and unique type of cytoplasmic inclusion was encountered in perivascular macrophages. These inclusions presented as aggregations of irregularly round, membrane bound particles, 0.25-0.4 /zm in diameter, in some cases with an internal structure remini scent of partly degraded mitochondria. However, the aggregations were not convincingly enclosed within membranes as would be expected in case of autophagocytosis. Another, hypothetical, interpretation is that they represent abortive stages of Cowdria ruminantium attempting to develop extravascularly and that possibly cell-mediated immunity, developed during and after the incubation period, limits this second cycle within the host and results in the perivascular mononuclear cell infiltrations observed. The findings in this study suggest the possibility of a direct involvement of circulating monocytes in the pathogenesis of the brain lesions. Such cells may carry and shield the antigen through the vessel wall into extravascular sites since no signs of vasculitis or abnormal vascular permeability were found, making it unlikely that soluble antigens are involved. The finding of a morphologically intact endothelium and vessel wall, even under perfusion conditions, also casts doubt on a possible role of vasoactive substances in the development of the lesions. If and when permeability changes of the brain microvasculature occur, they apparently represent a later development of an inflammatory process rather than a primary mechanism in the pathogenesis of cerebral heartwater.
Molecular epidemiology of bovine tuberculosis in indigenous cattle and selected wild animals in livestock wildlife interface in Mikumi-selous ecosystem, Tanzania
(Sokoine University of Agriculture, 2016) Mwakapuja, Richard Simon
Bovine tuberculosis is a chronic infectious disease that affects the health of livestock, humans and wild animals in Tanzania and worldwide. In Tanzania, the majority of livestock are indigenous and are kept under extensive management system. High number of the livestock are reared in livestock-wildlife interface areas where there is sharing of pasture and water among different animal species. Such ecological environment can easily enhance the spread of multi-species pathogens such as M. bovis. Spread of M. bovis depends on spatial-temporal variation of animals within population, population dynamics and movement of pathogens within population. The present study aimed at investigating the burden, spatial distribution, clustering and genetic relatedness of pathogenic Mycobacteria in indigenous cattle and wild animals in Mikumi-Selous ecosystem. The single intradermal comparative tuberculin test (SICTT), gamma interferon (ylFN) and BovidTB Stat-Pak assays were applied to test M. bovis infection in live animals. Tissue samples from dead animals were cultured and isolates were identified using the Mycogenus and Deletion methods. Genotypic relatedness was determined using Spoligotyping. A total of 1288 live cattle, 89 slaughtered cattle, 63 African buffaloes (Syncerus caffer) and 35 hunter-killed wild animals of 17 different species were tested. The prevalence of M. bovis infection in cattle was 3.7% and 7.8% (n=1288) using a cut- off for positivity of 4 mm and 2 mm, respectively. Significant large M. bovis infection clusters was located across Msolwa, Mfilisi, Mikumi and Msongozi villages and round Wami and Mkondoa rivers near Mikumi National Park (p=0.02) in Kilosa district. Low clusters were found in Ulanga district (p=0.03). Mycobacterium bovis was isolated from 11.2% (n—89) of cattle samples. No Mycobacteria isolate was found in wild animals samples. Three spoligotypes were identified, namely SB 1467, SB013.3 and SB2190. Spoligotype SB 1467 was the most dominant and was reported for the first time in Tanzania. Spoligotype SB2190 was novel isolate. Spoligotypes SB 1467 and SB2190 were genetically related by 96.9% while SB2190 and SBO133 were related by 59.4%. The agreement between the tests was established using Cohen’s kappa statistic to evaluate the agreement and form the basis for evaluation and comparison between S1CTT, ylFN and BovidTB Stat- Pak. Cohen’s kappa coefficient (k) agreement between ylFN and BovidTB Stat-Pak in African buffaloes was 0.14 while the agreement between SICTT and ylFN and between SICTT and BovidTB Stat-Pak in indigenous cattle was 0.5 and 0.21, respectively. The agreement between the tests ranged from poor (k=O.I4) to moderate (k=0.5). This study, for the first time established the spatial distribution of AL bovis infection and identified AL bovis infection clusters and a novel AL bovis spoligotype. A structured questionnaire was used to capture information from livestock farmers on knowledge and awareness related to tuberculosis transmission and the associated risk factors in animals and humans. About 21% (n=148) of livestock farmers were aware of existence of AL bovis infection in livestock. There was significant difference (p<0.001) between farmers with knowledge on M. bovis infection transmission in animals and humans and those without the knowledge. These findings can be applied to guide cost-effective surveillance and interventions strategies in control of bovine tuberculosis in Tanzania.
Epidemiological studies on bovine parasitic otitis
(Sokoine University of Agriculture, 1998) Shayo, Elizabeth Tabu Elikana
Experimental infection with Rhabditis bovis, Pseudomonas aeruginosa and Actinomyces pyogenes was carried out on fifty-three male weaner calves. The calves were inoculated into their ears with seven different combinations of suspensions of Rh. bovis, P. aeruginosa and A. pyogenes, the eighth group (control) was inoculated with phosphate buffered saline (PBS). Twenty-five calves (47.2%) developed mild to severe clinical manifestations in-groups inoculated with the nematode and the bacteria. Calves inoculated with the bacteria alone and the control did not develop clinical manifestations. There was significant difference (P<0.05) in responses between groups one, two, three and four which were inoculated with bacteria and nematode and those inoculated with bacteria alone and the control group. The responses were not significantly different (P>0.05) between groups five, six, and seven which were inoculated with bacteria alone and the control group. Histopathological studies revealed polymorphonuclear cell infiltration, thickening and desquamation of the epithelium of the aural canal. In this study, Rh. bovis was shown to be a primary pathogen although histologically there was no evidence of the involvement of the nematode. Bacteria exacerbated the clinical effects only in the presence of the nematode. Studies on the roles of dips and spray races in the transmission of the nematode Rh. bovis were carried out by subjecting 20 healthy cattle to dipping, 20 to spraying using Steladone®, and 20 to a topical application with Ectopor® SA 020 (Ciba - Geigy Limited Switzerland) as controls. No animal in all three groups contracted the disease. The dip wash and mud from the footbath and in the collecting pens were examined for the presence of nematodes. Nematodes were isolated from manure from night pens in only one farm and one dip and none from the footbath and collecting pens. Dip tanks were established as temporary reservoir of the nematode only during dipping and nematodes were introduced mainly through ears of infected animals. The prevalence of P. aeruginosa and A. pyogenes in the ears of clinically healthy cattle and those clinically affected with bovine parasitic otitis was established by bacteriological examination of 652 samples from diseased animals and 410 from non diseased animals. Prevalence rates of 1.5% in diseased ears and 5.1% in non-diseased ears for P. aeruginosa and 4.9% and 2.5% in diseased and non-diseased ears for A. pyogenes respectively were determined. From this study, it has been found that severe clinical disease of bovine parasitic otitis is significantly associated with A pyogenes (OR=1.27) while P. aeruginosa has a “sparing” effect (OR=0.27) Further studies on the role of flies on the transmission of bovine parasitic otitis are required.
Performance of grazing crossbred cattle supplemented with minerals: calcium, phosphorus and zinc
(Sokoine University of Agriculture, 2001) Phiri, Elliot Chikula Jailos Henderson
A study was conducted from 1997 to 1999 in Iringa region, Tanzania in order to evaluate the mineral status and performance of grazing crossbred dairy cattle as affected by season and nature of mineral supplementation. Initially concentration of calcium, (Ca), phosphorus (P) and zinc (Zn) in soil, grass pasture and blood plasma were measured. Seasonal effect was apparent (P< 0.05) in soil and pasture mineral concentration. Soil calcium (4.46 - 5.67 me /100g), was adequate during the dry and the rainy season. Soil phosphorus (P< 0.05) was low during the rainy season and high in the dry season (11.9 - 14.8 vs 28.1 - 31.8 ppm) whereas zinc (0.81 - 1.02 ppm) was deficient in both seasons. Pasture Ca (0.33 - 0.39%) and P (0.25 - 0.34%), were adequate whereas Zn (21.2 - 25.2 ppm) was inadequate for the sampled periods. Blood plasma Ca (<2.20 mmol/1), inorganic phosphate (< 1.28 mmol/1) and Zn (<12.2 pmol/1) were marginal to normal values in the sampled dairy cattle. Other minerals in the soil and grass pasture were also analysed. Sodium (Na) (0.31 - 0.37 me /100g), potassium (K) (0.36 - 0.42 me /100g), iron (Fe) (76.4 - 101 ppm) and copper (Cu) (1.38 -2.24 ppm) were adequate during the dry and the rainy seasons. However, magnesium (Mg) (0.99 - 1.57 me /100g) was deficient in both seasons. Pasture K (2.05 - 2.67%), Na (0.21- 0.23%) and Fe (154 - 190 ppm) were adequate whereas Mg (0.15 -0.17%) and Cu (2.53 - 4.57 ppm) were inadequate in the sampled periods. In an attempt to quantify the requirement for supplementation of Ca, P and Zn forty eight dairy cows in their first, second and third parity were allocated to eight groups, comprising six cows based on breed, parity, stage of lactation and milk yield. Group 1 was control group receiving no mineral supplement; group 2 (Ca) received 10 g of Ca in the form of calcium carbonate (CaCCh); group 3 (P), received 8 g of P in the form of sodium monophosphate (Na2HPC>4.2H2O) and group 4 (Zn) received 400 mg of Zn in the form of zinc oxide (ZnO). The rest of the groups received a combination of Ca and P or Zn or both. Animals were drenched with the minerals daily as of May 1997 to March 1999. Performance was evaluated in terms of cow’s health status, milk yield and reproductive performance and by measurement of blood parameters and metabolites which affect health, energy and protein balance before supplementation started and thereafter at every two month intervals. Significant differences (P< 0.05) were observed between groups in terms of performance. Low plasma Ca, Pi and Zn were more prevalent in the dry season (P < 0.05) especially in the month of July and during calving period in the month of March. None of the Ca, P and Zn formulations were able to rectify the low plasma Ca observed during these periods, however, Ca supplementation in the form of CaCCh. improved tissue P and Zn status. Diy season supplementation with concentrates, hay and fresh forage improved plasma Ca, Pi and Zn concentrations. Cows supplemented with Ca in the form of CaCOj only were superior (P< 0.05) in terms of body condition, less cases of mastitis and anaplasmosis, short calving interval (< 365 days) and high milk yield with high fat and protein content compared to the other groups. General health status, live weight gain, body condition score were affected negatively with P supplementation in the form of Na2HPO4.2H2O alone. Supplementation with Ca/Zn in dairy cows maintained copper balance, however, the other formulations resulted in reduction in copper balance. Supplementation of P/Zn maintained stable levels of blood selenium concentration during both the dry and rainy season. Calcium and Zn supplementation reduced the blood selenium concentration in the rainy season. Since incidences of low plasma Ca, Pi and Zn occurred during the dry season, supplementation with concentrate, hay and fresh forage during the dry season should be encouraged to the farmer and other farmers with similar problems for better metabolism of Ca, P and Zn. However caution should be taken with type and the amount of Ca, P and Zn fed to the animals to avoid interactions between these elements other minerals like Cu and Se. Since P requirements for tropical grazing cattle is not known with certainty, further research on P requirements in grazing crossbred cows is recommended. Magnesium and Cu were inadequate in forage, supplementation of these minerals in the diet was recommended. The effects of Ca, P and Zn supplementation on Cu and Sc balance need more research in order to quantify the effects and understand the mineral interaction mechanisms involved.
Prevalence, epidemiology, and virulence of Pasteurella multocida and related organisms obtained from poultry and their animal contacts
(The Royal Veterinary and Agricultural University, 2000) Muhairwa, Amandus Pachificus
This thesis is divided into two sections. The first section presents six reviewing chapters in relation to work performed and a chapter detailing conclusions from the study. The second part contains four papers referred to as Appendix 1-1V, which detail the work in the thesis. The articles I and II present prevalence and epidemiological investigations of P. multocida in commercial poultry flocks in Denmark, and free range village chickens and their contact animals in Tanzania. Article 111 discusses phenotypic, molecular and epidemiological investigations of Pasteurella species obtained from Tanzania. The last article presents the study on correlation between serum resistance, outer-membrane proteins and virulence of P. multocida. The prevalence of P. multocida carriers in the flocks with a history of fowl cholera was shown to be significantly higher than that of the flocks without a history of fowl cholera in commercial flocks in Denmark (Appendix I). These findings underline the importance of surviving birds in the epidemiology of fowl cholera. The carriers in flocks without history of fowl cholera were also demonstrated, but their role in fowl cholera is still uncertain. All three subspecies of P. multocida, namely ssp. Multocida, ssp. septica and ssp. gallicida were demonstrated, but the subspecies gallicida was obtained exclusively from Pekin ducks from a farm with a history of fowl cholera. A single clone affected each of the investigated flocks, but some clones appealed in more than a single flock. Investigations into strains of P. multocida from one of the farms in four consecutive outbreaks demonstrated a different clone in each outbreak. This indicates that outbreaks are clonal, and the disease can be eliminated from the infected farms. Isolation of P. multocida from the cloacal mucosa of earners was reported for the first time, however, the significance of cloacal earners in spreading infection is not known. Occurrence of P. multocida and related species in free ranging chickens and ducks, dogs and pigs (Appendix II) was investigated in three subclimatic zones; hot, warm viand cool, in rural Morogoro district, Tanzania. The strains obtained included P. multocida ssp. multocida from chickens, ducks, cats and dogs, /< multocida ssp. septica from dogs and cats, gallinarum from a duck, P. canis and P. dagmatis from dogs, and P. slomatis from dogs and cats. Other strains included organisms with uncertain taxonomic affiliation named taxon 16, and unclassified strains with Pasteurella like features. P. multocida was obtained from two chickens (2%) and 11 ducks (22%) of warm zone. No isolates were obtained from poultry in the remaining zones. Cats had the highest prevalence of P. multocida ssp. multocida, while P. canis and taxon 16 were predominant in dogs. Mouse inoculation was more sensitive in etecting P. multocida ssp. multocida than blood agar and selective medium. Direct culture on blood agar recovered most of the other Pasteurella spp.. These findings demonstrated the existence of P. multocida carriers in the free ranging village poultry, cats and dogs, and underline the potential of exchange of strains between the different animal species. Surveillance of diseases in free ranging village chickens to gauge the clinical importance of fowl cholera and other diseases was recommended. One hundred and forty-three Pasteurella spp. strains and ten unclassified strains obtained from free ranging poultry, dogs and cats were investigated by extended phenotypic characterization (Appendix III). One hundred and forty-nine of these strains were selected for further studies using ribotyping and REA-typing to evaluate the role of dogs and cats in P. multocida transmission to poultry. Seven and six-type strains were included for comparison in phenotyping and genotyping, respectively. Eleven clusters and six unclustered strains were revealed by phenotyping. Ribotyping outlined twelve clusters and six unclustered strains. A correlation between clusters obtained by phenotyping and ribotyping was demonstrated which indicated that a genetic basis exists for clusters outlined by quantitative evaluation of phenotypic data. Similarities and differences in hosts, phenotype, ribotype, and zone of isolation were demonstrated among Pasteurella strains investigated. Isolates of P. multocida from ducks were shown to be clonal by both phenotyping and ribotyping. These strains were identical to one of the chicken strains. REA-typing, however, showed that the chicken strain was different underlining that exchange of clones of P. multocida viibetween avian species seems to be rarely happening under village conditions. Management practices in the villages suggest the potential for exchange of P. multocida between poultry and animals kept in contact. Tire present findings, however, did not indicate that clones of P. multocida are widely exchanged between poultry and other animal species even though close contact exists. In the present investigation, exchange of clones of P. multocida was only demonstrated among animals belonging to the same species. Caution is drawn to the use of ribotyping alone for epidemiological typing and tracing of P. multocida. The present results also underline the importance of proper phenotyping in the identification of P. multocida and related species. Serum resistance of P. multocida in the sera from chickens, turkeys, ducks and pigs was determined and correlated with in-vitro and in-vivo outer-membrane proteins expression and virulence in chickens. Eighty-seven field strains of Pastcurella and nine reference strains representing different clones were grown in sera from chickens, ducks, turkeys and pigs. Serum activity of each strain was measured by changes in the optical density of the serum after inoculation and incubation at 41 °C for chicken, turkey and duck serum and 39 "C for pig serum. The strains were classified into High serum resistant (R), moderate serum resistance (M), and serum sensitive (S) by comparing with strains of known serum activity. Strains of identical genotype by Restriction endonuclease analysis were found to have identical growth curves and the same maximum OD values, when cultured in serum from the same host species. Turkey serum was shown to be less inhibitory to a wide range of P. multocida strains than chicken, duck and pig sera. Serum resistant strains were demonstrated among avian as well as mammalian strains, with the proportion of serum resistant strains being higher in fowl cholera outbreak strains than in non-outbreak avian strains. A range of minor and major outer-membrane proteins were common among the selected serum resistant and serum sensitive strains, when cultured in BHI, in-vivo and in chicken serum. However, no specific OMP expressed in vitro or in vivo was consistent with serum resistance or sensitivity among the strains investigated. Although most severe lesions in experimentally infected chickens were produced by a serum resistant strain, lesions were also found in chickens infected by scrum sensitive strains, indicating the involvement of multiple factors in the virulence of P. multocida. Further investigations on scrum resistance should also relate other host and bacterial factors responsible development of fowl cholera.
Prevalence and antimicrobial susceptibility profiles of campylobacter coli isolated from broilers and layers in Mwanza and Arusha, Tanzania
(Sokoine university of agriculture, 2022) Nshama, Rosemary P
Campylobacteriosis is an emerging zoonotic disease which poses threat to both human health and animal productivity. Recent emergence of Campylobacter resistance to antimicrobial agents that are commonly used and recommended by the World Health Organization (WHO) for treating human gastroenteritis has been reported from different countries worldwide. Globally, chickens are one of the major sources of animal proteins and are the primary reservoirs of Campylobacter spp. Antimicrobials are being added to chicken feeds in low doses in order to accelerate their growth that can lead to development of antimicrobial resistant Campylobacter strains within chicken gut. When chicken products are consumed, antimicrobial resistant (AMR) Campylobacter strains can be transferred to humans. In this study surveillance was conducted on antimicrobial resistant Campylobacter isolated from broiler and layer chickens from Mwanza and Arusha regions in Tanzania. Antimicrobial resistance data were generated in a cross- sectional study which was carried out using a total of 402 cloaca swabs collected from apparently health broilers (202) and layers (200) in Arusha and Mwanza regions. Collected samples were enriched into Bolton broth supplemented with 5% laked horse blood. Enriched samples were cultured onto blood agar by filtration method using a 0.45μm nitrocellulose membrane. Screening of colonies was based on colony characteristics and Gram staining. Presumptive Campylobacter colonies were then sub- cultured onto Muller Hinton (MH) agar supplemented with 5% laked horse blood for purification of isolates. DNA was extracted from isolated colonies by boiling method while Multiplex PCR was used for genus and species confirmation with specific primers. All isolates were subjected to susceptibility test by disc diffusion method against six antimicrobials including ciprofloxacin, tetracycline, nalidixic acid, gentamycin, ampicillin and erythromycin. Antimicrobial susceptibility results were interpreted as Susceptible (S), Intermediate (I) or resistant (R) using the Clinical Laboratory Standard Institute (CLSI) cut-off values, and isolates that were resistant to three or more of antimicrobial classes were considered to be multidrug resistant (MDR). Out of 402 samples and from Mwanza and Arusha 31(7.71%) were positive for Campylobacter isolates in layers (13/200) and broilers18/202). All 31 bacterial isolates were confirmed to be C. coli spp. In Mwanza, the overall prevalence of C. coli was 6.5% (13/200), and by chicken type the values were 6% (6/100) and 7% (7/100) for broilers and layers, respectively. In Arusha, the overall prevalence of C. coli was 8.9% (18/202), and prevalence values by chicken breed were 10.8% (11/102) and 7% (7/100) for broilers and layers respectively. Antimicrobial results indicated that 6.5% (2/31) of all isolates were susceptible to all antimicrobials used in the study. The highest proportion of antimicrobial resistance was observed for ampicillin (80.6%), followed by nalidixic acid (16.1%), and tetracycline (9.7%). The lowest resistance was observed for gentamycin (3.2%). Four out of thirty-one (12.9%) isolates were MDR to four different antimicrobials tested each with different patterns. Campylobacter coli was the only specie isolated from cloaca swabs of chicken with the overall prevalence of 7.71%. The isolates were resistance to at least one antimicrobial agent with ciprofloxacin showing a significant difference (p-value=0.049%) in AMR prevalence among chicken types which was higher in broilers than in layers and four of the isolates were MDR with different resistance patterns. Results from this study show that emerging foodborne MDR is a threat to human and surveillance is required to establish supportive data that will be used in formulation of country regulations and policy regarding the use of antimicrobials in both human and veterinary medicine.
Occurrence and characteristics of A. vibacterium paragallinarum in Uganda
(Sokoine University of Agriculture, 2006) Byarugaba, Denis Karuhize
Investigations were conducted to establish the occurrence and characteristics of Avibacterium paragallinarum in Uganda. Seven hundred and ten bacteriological and serum samples (642 from healthy birds and 68 from chickens with coryza-like signs) were collected from chickens and turkeys for isolation of bacteria and demonstration of antibodies. Isolates were characterised by phenotypic (scrotyping, biotyping and antimicrobial susceptibility) and genotypic methods (enterobacterial repetitive intergenic sequence based polymerase chain reaction, ERIC-PCR and distribution of resistance genes). The potential role of gallinaceous birds in transmission of A.paragallinarum was evaluated experimentally and the efficacy of a commercial vaccine against the disease was assessed. Only five isolates were recovered and all were serotype C and NAD-dependent. Overall seropositivity was 40.5%, with 18%, 0.5% and 22 % against serotypes A, B and C, respectively. No antibodies were demonstrated in turkey sera. Multidrug resistance was demonstrated in three isolates and resistance genes for sulphamethoxazole (sn/2), ampicillin (blaTEM), tetracycline (tetC and tetA) and streptomycin (strA) were demonstrated. Only antimicrobial resistance markers differentiated isolates according to their epidemiological background. Commercial and local chickens were equally susceptible to challenge while turkeys and guinea fowls showed transient mild signs and did not transmit infection neither did they pick infection from infected chickens. The isolates were resistant in normal chicken scrum at both 3 and 6 hours of incubation but resistant at 3 hours and sensitive at 6 six hours in turkey and guinefowl sera. The susceptibility of the isolates in serum correlated with their pathogenicity in the different poultry. No carrier status was demonstrated in this study using PCR and culture. Vaccinated birds were partially protected. This is the first report of isolation and characterisation of A. paragallinarum from Uganda. Resistance genes in A. paragallinarum are also reported for the first time. Studies based on a wider collection of isolates would be important to elucidate the mechanisms behind their persistence in carrier chickens and the potential exchange of resistance genes among respiratory tract pathogens.
Assessment of semen quality parameters of three Tanzanian native chickens
(Sokoine University of Agriculture, 2022) Luvanga, Julius Donatus
Tanzania has a total chicken population of approximately 92.8 million, of which about 42.7 million are native breeds (Gallus gallus domesticus) and 50.1 million are exotic breeds kept primarily for commercial purposes. The poultry industry plays an important role in terms of food security, source of income, and meeting economic and social obligations for the household, especially for poor families. Despite their importance, research on improving productivity of the native chicken’s strains is lacking. Therefore, the present study assessed semen quality parameters of freshly collected semen of three different native chicken ecotypes; Ching’wekwe, Kuchi and Morogoro-medium and also investigated the effect of synthetic Gonadotropin releasing hormone (GnRH) on semen quality parameters of Tanzanian native chickens. For assessment of semen quality, twelve roosters (four from each ecotype) with two age groups (11-15 and 24-28 months) were used as semen donors and a total of 192 semen samples were collected from 12 roosters (four from each ecotype) using the abdominal massage technique at weekly interval for four consecutive months. Evaluation of the effect of GnRH treatment on semen quality parameters in three ecotypes of Tanzanian native chickens was performed; where a total of thirty-six mature cockerels from Tanzanian native chicken ecotypes were used. Thirty cockerels (ten from each ecotype) were intramuscularly injected with 0.2 ml of GnRH (Factrel®) once in a week for five consecutive weeks while six (two from each ecotype) were used as a control group only receiving normal saline solution. Semen was collected at weekly interval by abdominal massage technique starting immediately after last GnRH injection for five consecutive weeks. Semen characteristics of individual samples were evaluated. For assessment of semen parameters, volume, pH, sperm motility, sperm concentration, proportion of spermatozoa with normal morphology and proportion of live spermatozoa among the ecotypes varied from 0.42±0.04 to 0.52±0.03mL, 7.01±0.00 to 7.02±0.00, 72.81±1.27 to 76.63±1.35%, 3.90±0.98 to 4.12±1.96 x 10 9 /mL, 86.16±0.55 to 89.38±0.80% and 88.06±1.13 to 90.97±0.81% respectively. However, only the variations in proportion of spermatozoa with normal morphology and proportion of live spermatozoa among the ecotypes were significant (P<0.05). The semen volume, pH, sperm motility, sperm concentration, proportion of spermatozoa with normal morphology and proportion of live spermatozoa among the two age groups varied from 0.44±0.03 to 0.52±0.03mL, 7.01±0.00 to 7.02±0.00, 73.88±1.13 to75.92±0.99%, 3.80±0.45 to 4.28±0.32 x 10 9 /mL, 87.02±0.58 to 88.15±0.64%, 88.27±0.77 to 89.83±0.77% respectively. Nevertheless, only the variations in semen volume among the two age groups were significant (P<0.05). The Pearson correlation coefficients between semen volume and other semen quality characteristics were mostly low to medium with positive values ranging from 0.01-0.51 between semen volume and sperm motility and between morphological normal spermatozoa and proportion of live spermatozoa, respectively. Regarding the effect of GnRH on semen quality, semen parameters increased significantly (p<0.05) between control and treatment groups; including semen volume (0.48±0.02 mL versus 0.55±0.02 mL), sperm motility (74.90±0.76% against 80.02±0.30%), concentration (4.04±0.18 × 10 9 /mL versus 4.80±0.14 × 10 9 /mL), proportion of morphological normal spermatozoa (87.58±0.43% versus 91.25±0.3%) and proportion of live spermatozoa (89.05±0.55% against 91.65±0.31%) but semen pH did not change between control and treatment groups. It can be concluded that although there is minimal variation in semen quality among ecotypes and age groups, all the ecotypes might still be used in breeding purposes to maintain native chickens and semen quality parameters can be improved by injecting GnRH to cockerels and therefore increasing productivity in the poultry industry.
Characterization of the reef-associated elasmobranchs fishery in Tanzania mainland
(Sokoine University of Agriculture, 2022) Rugabela, Rutaihwa Patrick
In Tanzania, coral reef-associated elasmobranchii fisheries are among the most important as they contribute significantly in small-scale subsistence (artisanal) category in some cases representing the major income for many coastal communities. Tanzania's marine fisheries sector, especially in coral reefs’ associated elasmobrachs is constrained by lack of data on fish stocks, fishing effort, and level of exploitation. This study was conducted so as to characterize the catch composition for elasmobranchs in the selected hotspot landing sites in Tanzania mainland. Elasmobranchs landings from artisanal fisheries were observed from February to July, 2020 in the selected landing site. A total of 391 individuals of rays and sharks were recorded at the selected landing sites in Tanzania mainland during this study. The landed elasmobranch catches belonged to four families of Dasyatidae, Myliobatidae, Carcharhinidae and Sphyrinidae. At least eight species of elasmobranchs were recorded in this study. Species from Dasyatidae family dominated the total fish catch. The landed fish species were of small and medium size (cm), all immature. The occurrence of immature fish in the catch is an indicator of fishing overexploitation to take place along the Tanzania mainland coastline.
Design of synthetic human gut microbiota ecosystem model for screening potential prebiotics from phytochemicals
(Sokoine University of Agriculture, 2022) Mabwi, Humphrey Andalo
The human gut microbiota (GM) is a complex and diverse microbial population that is integral to health maintenance. Mechanistic studies of human GM are limited due to its complexity with of over 1,000 species of microorganisms. In this regard, synthetic microbial communities with reduced complexity could be an alternative for GM studies. The main objective of this study was to establish synthetic gut microbial communities for screening of phytochemicals beneficial to gut flora important in the discovery of novel GM therapies. Specifically, this study sought to: (i) investigate conditions for establishment of synthetic gut microbial ecosystem, (ii) determine whether synthetic gut microbial ecosystems can demonstrate prebiotic nature of phytochemicals, and lastly (iii) validate synthetic in vitro gut microbial communities with an in vivo mice study. Firstly, GM key stone species were obtained from Korean Collection for Type Cultures (KCTC) and American Type Culture Collection (ATCC). Next, a suitable medium for re-creation of synthetic microbial communities was sought amongst Chopped Meat Carbohydrate (CMC), Bryant and Burkey (BB), Tryptic Soy Agar (TSA), Brain Heart Infusion (BHI), Reinforced Clostridium Medium (RCM), and Gifu Anaerobic Medium (GAM). Majority of bacteria could grow well in GAM, and therefore GAM medium was selected for this study. Mucin glycans were supplemented in GAM at 2g/L or 4g/L then investigated if they could simulate synthetic GM ecosystem. Specific genera like Bacteroides, Akkermansia, and Clostridium grew significantly faster in mucin-supplemented GAM (p< 0.05, n=3). The synthetic gut microbial community were then assembled and co-cultured in mucin supplemented GAM followed by microbial community profiling and short-chain fatty acids quantitation. Co- culture results showed that mucin stimulated beneficial bacteria such as Collinsella, Bifidobacterium, Ruminococcus, and Lactobacillus compared to gut opportunistic pathogens like Escherichia. Nevertheless, acetate proportion was higher in the mucin-supplemented consortia (p < 0.05, p < 0.001, n=9) and this was highly related with microbial composition in this group. However, some bacteria were not represented in this set-up and this could be attributed to the lack of a real mucosal layer that could be a niche and also a carbon source for bacteria. In this regard, mucosal layer was incorporated using mucin agar-gel. Upon analysis, specific bacterial genera like Roseburia, Bifidobacterium, Lactobacillus, and Collinsella were able to colonize well in the solid mucin-agar component, while Enterococcus, Veilonella, and Clostridium dominated in the liquid part (p < 0.05, p< 0.01, n=5). Metabolic functional prediction in the two experimental setups showed that predicted functional pathways were highly related to microbial composition. The second study applied synthetic microbial communities cultivated in a mucosal simulated environment to test effects of anthraquinone (phytochemical) on top essential gut bacteria. A growing body of research shows that phytochemicals in plants can affect the composition of the GM. As a result, the GM is a good candidate for nutritional interventions aimed at improving health. The anthraquinones examined in this study include emodin, obtusifolin, obtusin, aurantio- obtusin, chryso-obtusin, Gluco-aurantio-obtusin, and Gluco-obtusifolin. Single bacterial isolates were cultivated with these compounds at 100 mM and growth was measured at OD 600 for 18 to 24 h at 37 °C. Results showed emodin to stimulate beneficial bacteria including Akkermansia, Clostridium, Roseburia, and Ruminococcus but inhibited major gut enterotypes (Bacteroides and Prevotella) which are associated with gut inflammation. Emodin also preserved high levels of beneficial anti-inflammatory gut bacteria isolates such as Roseburia and Faecalibacterium while again inhibiting Bacteroides and Prevotella in co- cultivation. To validate the synthetic microbial communities’ co-cultivation and its application in GM-phytochemicals studies, an in vivo study was performed. Mice were randomly divided into three groups: normal group, low emodin (10 mg·kg -1 ) group, and high emodin (50 mg·kg -1 ) group. Emodin was administered by oral gavage for one week followed by sample harvesting and microbial community profiling. Emodin stimulated the anti-inflammatory bacteria Roseburia in co-culture as in mono-culture and Faecalibacterium in co-culture, these bacteria were not detected in vivo, but emodin stimulated Clostridium and Ruminococcus in vivo (which are related to Roseburia and Faecalibacterium). Nevertheless, emodin also induced anti-inflammatory immune cells, which may correlate with its impact on specific gut bacteria in vivo. Gut ecosystem simulation is an advance to mechanically understand the role of the GM in health and diseases necessary in developing innovative GM-phytochemicals therapies. In conclusion, this study has demonstrated that single bacteria culture, synthetic gut ecosystem and in vivo mice experiment can be used for diverse microbiome research since they showed consistent results for major GM changes. I recommend use of synthetic GM ecosystem model in rapid identification of phytochemicals of therapeutic significance.
Effects of heavy metals on bacterial growth, biochemical properties and antimicrobial susceptibility
(Sokoine University of Agriculture, 2022) Ngwewa, Faith
Heavy metals are metallic elements that occur naturally and have high atomic weights and densities that are five times greater than the density of water. Several studies have demonstrated that metal contamination in natural environments could have an important role in the development and spread of antimicrobial resistance. This is of particular concern, considering that heavy metals usually occur at higher levels than pharmaceutically produced antimicrobials. Also, the bio-accumulative and non-biodegradable nature of heavy metals may result in long- term antimicrobial resistance selection pressure. Therefore, this study assessed the effects of Copper, Cobalt, Cadmium, Zinc and Lead salts on growth, biochemical properties and antimicrobial susceptibility of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus to commonly used antimicrobials. The selected bacteria were exposed to varying concentrations of the heavy metal salts ranging from 1 ppm to 1 000 ppm after which growth was measured using a spectrophotometer. The effect on biochemical properties and antimicrobial susceptibility were also tested by the use of conventional biochemical tests and Kirby-Bauer disk diffusion methods, respectively. Different heavy metals affected the growth of each individual microorganism differently. Despite that, the growth of E. coli, P. aeruginosa and S. aureus was observed to be inversely proportional to the concentrations of the heavy metals used. Following exposure to heavy metals, E. coli and S. aureus showed no changes in their biochemical properties but P. aeruginosa gave a positive urease result contrary to the control. E. coli developed resistance to Levofloxacin, Meropenem and Tetracycline while S. aureus to Azithromycin and Gentamicin and P. aeruginosa developed resistance only to Meropenem. These results confirm the adverse effects of heavy metals on bacterial growth and reveals that heavy metals can cause changes in some biochemical properties of bacteria that produce any of these properties under stressful growing conditions. This research also supports the findings that heavy metals enhance the development of antimicrobial resistance in otherwise antimicrobial sensitive strains of bacteria. This study therefore, gives insight into the likely state of the proliferation of heavy metal induced biochemical properties and antimicrobial resistance in heavy metal contaminated areas.
Innovative approaches to brucellosis diagnosis
(Sokoine University of Agriculture, 2022) Lukambagire, Abdulhamid Settenda
Brucellosis is an endemic zoonotic disease of public health importance in many low- and middle-income countries. The main zoonotic species implicated in human infection however are Brucella melitensis, B. abortus and B. suis infecting over 500,000 humans annually worldwide. Brucellosis also causes production and reproductive losses in livestock globally estimated at about two billion USD annually. Brucellosis is listed as one of six priority zoonoses in Tanzania, where the national One Health strategic plan highlights gaps in current surveillance data needed for the burden estimation of human brucellosis and robust tools for the identification of the species of Brucella infecting animals. This study evaluated the current practices for diagnosing brucellosis based on a retrospective survey of records at health facilities in Arusha Region, northern Tanzania. Patterns of brucellosis testing, brucellosis positivity and test reagent management were evaluated using generalized, linear mixed-effects, regression models, with two main outcomes of interest: brucellosis testing practice and brucellosis test positivity variation compared to the facility type, ownership, ownership, month and year of data collection as explanatory variables. Brucella species exposure was estimated using real-time, quantitative polymerase chain reaction assays for the detection and speciation of Brucella in blood clots from cattle, goats and sheep in northern Tanzania. The association between animal level characteristics and the results of performance of the Rose Bengal test in this livestock population was evaluated by logistic regression modeling and cross-tabulation. Finally, the performance and costs of serological assays used for human brucellosis in northern Tanzania were evaluated and compared to internationally recommended reference tests. Significant associations were observed between the probability of brucellosis testing and the year and ownership of the facility where testing was done. The probability of brucellosis testing per month was significantly associated with an interaction between privately owned facilities and the year in which testing was done. The proportion of individuals classified as positive was significantly associated with the type of health facility and the district. Four commercial Febrile Brucella agglutination tests (FBATs), sourced from private distributors, were used with variable protocols to test for brucellosis in all the study health facilities. In the detection of Brucella spp. from blood clots, fifty- eight (11.6%) of the livestock samples were positive for Brucella spp. Brucella abortus (31.0%) and B. melitensis (38.0%) were detected in samples originating from all three livestock species sampled. However, there was poor agreement (K = 0.102) between the results of the qPCR and the RBT in the livestock population tested. The performance and cost evaluation of frontline serological tests for human brucellosis identified the RBT as the test with highest accuracy (97.7%, CI; 94.7–99.3) and the lowest per-sample cost ($0.69 – $0.79 USD). Comparatively, the often-used FBAT kits had low diagnostic accuracy and higher per-test costs than the RBT. In addition to the variable protocols for testing, the widespread use of poorly performing FBATs limits the inferences that can be made about the epidemiology of human brucellosis in northern Tanzania. The qPCR assays applied to blood clots detected Brucella spp. in cattle, goats and sheep on the ranch in Kagera Region. Brucella abortus and B. melitensis were each detected in all the samples from cattle, goat and sheep that were positive by the Brucella spp. and species-specific qPCR assays. The widely used commercial FBATs performed poorly and cost more than the RBT. The findings from this study highlight areas of focus to achieve improved quality of testing and surveillance of brucellosis at health facilities in Tanzania. Applied to scale, the uniform application of the RBT in health facilities, with quick and accurate reporting of test results and the exploitation of blood clots for Brucella genus detection are approaches that, applied complementarily to brucellosis diagnosis, could ultimately facilitate the formulation of strategies for prevention and control of this priority disease in many-resource limited settings in sub-Saharan Africa.
Antibiotic resistance and virulence profiles of staphylococcus aureus and escherichia coli from rodents, humans and chicken coexisting in Karatu, Tanzania.
(Sokoine University of Agriculture, 2022) Sonola, V. S.
Antimicrobial resistance (AMR) is a rapidly growing multifaceted problem which threatens global security, public health and the economy. Currently, about 700 000 humans worldwide lose lives annually due to AMR infections that are difficult to treat which are also associated with higher health care costs, elongated time spent in hospitals and increased animal production costs. This study was conducted in Karatu district, northern Tanzania, to investigate antibiotic resistance and virulence profiles of Staphylococcus aureus and Escherichia coli isolated from humans, rodents, chicken and soil in households. Interaction of rodents with humans and livestock in households’ environment has frequently been reported in Karatu, facilitating wide spread of resistant bacterial infections among different hosts in the community. The main objective of this study was to determine the antibiotic resistance and virulence profiles of Staphylococcus aureus and Escherichia coli isolated from rodents, chicken, humans and their surrounding environment in Karatu District. S. aureus were isolated from 284 human nasal swabs, 101 rodents’ deep pharyngeal swabs, 286 chicken cloaca swabs and 285 household soil samples. Specimens were plated into Mannitol Salt Agar (Oxoid, Basingstoke, UK) and incubated aerobically at 37 °C for 24 h. Presumptive colonies of S. aureus were subjected to Gram staining, catalase, deoxyribonuclease (DNAse) and coagulase tests for identification. Antibiotic susceptibility testing (AST) was performed by using Kirby-Bauer disc diffusion method on Mueller-Hinton Agar (Oxoid, Basingstoke, UK). The antibiotics tested were tetracycline (30 μg), erythromycin (15 μg), gentamicin (10 μg), ciprofloxacin (5 μg), iii clindamycin (2 μg) and amoxicillin-clavulanate (20 μg/10 μg). S. aureus strain American Type Culture Collection (ATCC) 25923 was used as a standard organism. Results were interpreted according to Clinical and Laboratory Standard Institute (CLSI) guideline of 2020. The samples used for E. coli isolation included 288 chicken cloaca swabs, 281 human stool, 101 rodents’ intestinal contents and 290 household soils. The specimens were plated onto MacConkey agar (Oxoid Ltd., Detroid, Michigan, USA) and incubated aerobically at 37 ºC for 24 h. Presumptive E. coli colonies were subjected to motility test and later indole, methyl red, Voges-Proskauer and citrate utilization (IMViC) tests for identification. E. coli strain ATCC 29522 was used as a reference organism. AST was performed by using Kirby-Bauer disc diffusion method on Mueller-Hinton Agar plates (Oxoid, Basingstoke, UK). The antibiotics tested were; tetracycline (30 μg), imipenem (10 μg), gentamicin (10 μg), ciprofloxacin (5 μg) cefotaxime (30 μg) and amoxicillin clavulanate (20 μg/10 μg). The results were interpreted by using CLSI (2020) guideline. Results of this investigation revealed high frequencies of isolation for S. aureus and E. coli in rodents, humans, and chicken and soil samples. For S. aureus, the isolation frequencies were 52.1%, 66.5%, 74.3% and 24.5% in samples from chicken, human, rodent and soil, respectively. The isolation frequencies of E. coli from chicken, humans, rodents and soil were 81.6 %, 86.5 %, 80.2 % and 31.0 %, respectively. Based on AST phenotypic results, S. aureus isolates displayed resistance to clindamycin (51%), erythromycin (50.9%) and tetracycline (62.5%) while E. coli isolates showed high resistance against tetracycline (73.7%), imipenem (79.8%) and cefotaxime (79.7%). MDR E. coli (n=50) and S. aureus (n=57) isolates that exhibited high levels of phenotypic resistance to various classes of antibiotics were subjected to molecular analysis using iv multiplex polymerase chain reaction (PCR) technique to detect presence of antibiotic resistance (ARGs) and virulence genes (VGs). ARGs detected in MDR E. coli were; blaTEM (46%), blaCTX-M (26%), blaSHV (22%), tetA (46%), tetB (14%), qnrA (24%), qnrB (8%), blaOXA-48 (12%) and blaKPC (6%) while VGs detected included; ompA (72%), traT (26%), east (18%), bfp (10%), eae (2%) and stx-1 (4%). For MDR S. aureus, ARGs were; tetK (31.6%), tetL (8.9%), ermC (1.8%) and mecA (28.1%) while VGs detected were; clfB (10.5%), coa (14.0%), clfA (1.8%), hlg (1.8%), ebpS (3.5%), fnbB (3.5%), luk-PV (10.5%) and tst (1.8%). Positive and negative correlations between resistance and virulence genes were observed. For MDR E. coli, positive correlations were found between blaTEM and traT genes (r=0.51) and qnrB and bfp genes (r=0.63), while negative correlations were found between blaOXA-48 and ompA (r= -0.05), blaSHV and traT (r=-0.44) and tetA and east (r=-0.10). For S. aureus, positive correlations were found between resistance (ermC) and clfA (r=0.57), hlg (r=1.00) and clfB (r=0.43), tetK and clfB (r=0.39); tetK and coa (r=0.36). The principal component analysis (PCA) results for S. aureus showed that, resistance genes (tetK and mecA) and virulence determinants (clfB, coa and luk-PV) were common in all sample sources. The PCA also revealed that, MDR E. coli and S. aureus isolates from rodents and chicken had more ARGs and VGs compared to isolates from soil and humans. Besides, MDR E. coli isolates harboured traT, east, eae, stx-1, bfp and ompA genes indicating ability of isolates to cause various infections. Based on findings, this study documents high levels of antimicrobial resistance including MDR in E. coli and S. aureus isolated from chicken, humans, rodents and soil samples in Karatu, northern Tanzania. According to PCA results, E. coli isolates from rodents had more ARGs and VGs while for S. aureus these genes were found more in rodents and soil v environment implying that both subjects are potential reservoirs and can be sources of transmission. The increased prevalence of both resistance and virulence genes in the isolates suggests the ability of the pathogens to cause infections that are difficult to treat. Comprehensive one health interventions, are urgently needed and should include improving; i) improving hygiene and control of rodents in household environments. ii) Future studies should base on adequate understanding of the human-livestock environment interphase using well-designed genomic studies such as whole genomic sequencing (WGS) which provides a comprehensive picture on the pattern and magnitude of AMR and virulence genes spread. The advances and accessibility of genomic sequencing and analytical methods are essential in improving our understanding of AMR transmission dynamics at the human-livestock/animal-environment interface. Genomic studies should be coupled with behavioural, epidemiological, clinical and modelling using One Health approaches. This will ensure that the key drivers of resistance and virulence transmission between human-livestock-environment are accurately identified and the most appropriate interventions adopted. It is important to understand the importance of each component of the human-livestock/animal-environment. A One Health approach should be deployed to ensure involvement of relevant multisectoral and multidisciplinary to attain an optimal public health and ensure a safe environment.
Risk factors and economic implications of African swine fever in the pig value chain in Songwe and Ruvuma Regions, Tanzania
(Sokoine university of agriculture, 2022) Ngosomwile, Ntuli
African Swine Fever (ASF) is a highly contagious hemorrhagic disease of domestic and wild pigs. The disease has economic consequences not only to food security and people’s livelihoods but also on international trade as its occurrence and prevalence may result in trade restrictions. Given direct and indirect losses attributable to the disease, an understanding of risk factors associated with its outbreaks and economic implications of the disease on pig value chain actors is of paramount importance. This study was conducted with the aim to providing information in these respects. The study employed value chain approach to determine risks factors and the economic implications of ASF in Songwe and Ruvuma regions of Tanzania. Primary data were collected using structured questionnaires, and semi structured key informant’s guide. Observation was used to assess structure, facilities and practice within chains. Data were analyzed using Statistical Package for Social Sciences (SPSS) whereby descriptive statistics were computed and logistic regression analysis performed. Spreadsheet model and Gross Margin were used to determine financial losses associated with ASF. The findings show that main actors were pig producers, assemblers, wholesalers, rural and urban retailers. Unknown stock source (30%), poor husbandry such as free ranging (5%), poor management of waste products (73%) and poor handling of feed (73%) were risk practices in the production node. Transportation nodes operated under high risk due to frequent movements and pick-ups of ≥ 30 pigs per trip. Risk factors associated with ASF outbreak in Songwe region were sharing of boars (P < 0.01, OR= 7.05 and CI equipment (P < 0.04, OR= 4.14 and CI OR= 3.08 and CI =1.78; 28.00) and sharing of farm 95% =1.07; 16.09). Presence of bush pigs (P < 0.01, 95% =1.33; 7.14) and visitors access to farm (P < 0.01, OR= 2.38 and CI 95% =1.23; 4.61) were positively correlated with ASF outbreak in Ruvuma region. During 95% ASF outbreaks, high mortality occurred in piglets (31%) and in adult sows estimated at 9%. The estimated direct losses on pig producers were about 119 615 883 TZS in Ruvuma and 165 785 000 TZS in Songwe. Indirect losses on traders due to trade restrictions were estimated at 5 665 000 TZS in Songwe and 18 799 350 TZS in Ruvuma. Therefore, there is a need to improve good husbandry, marketing infrastructures and formation of pig business associations to improve pig value chain structure and organization. There is also a need for strengthening veterinary services on routine disease surveillance and training on disease risk manifestation for early detection, reporting and disease control. The research findings reported in this study provide an insight on sources and economic implications of the disease in affected areas which is very useful in prevention to other areas in Tanzania which are potential for ASF outbreaks.

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