Theses and Dissertations Collection

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    Epidemiological investigation of Peste des petits ruminants in selected regions of Tanzania
    (Sokoine University of Agriculture, 2021) Kgotlele, Tebogo
    Peste des petits ruminants (PPR), one of the most economically important disease of small ruminants has been earmarked for eradication following the successful global eradication of rinderpest. The disease is caused by peste des petits ruminants virus (PPRV). For eradication to be successful, the different PPR situations and contexts in each region and country must be well understood and reflected upon. In this study, the objective was to conduct an epidemiological assessment of the spread and persistency of PPR in selected areas of Tanzania with focus on distribution of antibodies to PPRV, PPRV genetic diversity and identification of practices by small stock farmers in response to this disease. The study was carried out using samples collected between 2013 to 2016. Sera samples were collected from clinically healthy sheep and goats for detection of antibodies to PPRV, together with blood, swabs and tissues for detection of the virus using molecular assays. A questionnaire was also administered in order to collect demographic characteristics, knowledge and practices relating to this disease from small ruminant farmers during sample collection. The overall true seroprevalences from samples collected in 2013 and 2015 was 27% (n = 3838) and for samples collected in 2016 was 30% (n = 328). Seroprevalences for samples collected in 2013, 2015 and 2016 show that the disease is continuing to spread in the country as seropositivity was observed in regions where previously no disease had been reported. Presence of the virus was found in samples collected in Morogoro and Arusha regions in 2016. Molecular characterization of the virus clustered them into two lineages, II and III. This confirmed presence of two lineages circulating in animals from the same herd, adding another dimension into the complexity of the disease in Tanzania. Other findings were confirmation of co-infections with Mycoplasma capricolum subspecies capripneumoniae, Pasteurella multocida and Capripoxvirus which cause similar clinical signs to PPR, complicating clinical diagnosis but emphasizing the importance of laboratory confirmation. Small ruminant farmers’ knowledge by regions on the disease occurrence was found to be high in Arusha region (northern Tanzania) and low in Morogoro region (eastern Tanzania), corresponding with the seroprevalences observed from samples collected in 2013, 2015 and 2016 in the said regions. Risk practices identified during outbreaks included trading of live animals, use of veterinary drugs and unattendance to sick animals. These risk practices could facilitate the spread of the disease in the country especially as the disease is transmitted through contact with infected animals. In conclusion, this study has revealed that PPR continues to spread within Tanzania as evidenced by antibodies to PPRV detected in areas that previously did not have the disease. Presence of two PPRV lineages shows the ability of lineages to co-circulate in an endemic area as well as in the presence of co-infections with other diseases in the local herd. Overall, there is poor knowledge by small ruminant farmers in the study areas that may be contributing to the spread of PPR. It is therefore recommended that annual vaccinations be carried out after well designed participatory surveillances are conducted to improve the herd immunity to levels that can contain the spread of PPR as a control measure. These vaccinations should take into consideration the geographical distribution of PPR in Tanzania so as to create buffer zones to stop further spread to areas with low or no disease, within and in neighboring countries. Genetic diversity of the virus strains circulating in the country should be further investigated by whole genome sequencing and how they compare to other strains. To prioritize on small ruminant farmer’s knowledge on the disease and emphasize how their participatory disease surveillance can help with the ultimate goal of eradicating PPR in Tanzania, regionally and globally.
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    Epidemiology and host genetic factors associated with bancroftian filariasis in endemic communities of North eastern Tanzania
    (Sokoine University of Agriculture, 2017) Mshana, H. J.
    Tanzania started a countrywide lymphatic filariasis elimination programme in 2000 adopting the mass drug administration (MDA) strategy. The drugs used for the MDA programme are a combination of ivermectin and albendazole. Clinically, the initial stages of lymphatic filariasis present as an acute febrile conditions with adenolymphangitis (ADL). Later on the disease is characterized by development of scrotal swelling (hydrocele) and swelling of the legs (lymphoedema) which gradually lead to elephantoid oedema. There is limited information on the current epidemiological trend of infections in areas where MDA implementation is ongoing and the immunological markers for early diagnosis of the disease have not been identified. The present study aimed at assessing the current status of bancroftian filariasis infection rate and morbidity in areas where MDA has been administered for over eight rounds as well as the clinical disease presentation and possible human genetic factors associated with disease development. The study was a cross-sectional descriptive study involving 472 individuals (>18 years) from endemic communities in Tanga region in north-eastern Tanzania where MDA has been implemented. Clinical data, socio-demographic survey and circulating filarial antigen (CFA) test was conducted using questionnaire and immuno chromatographic card test according to the manufacturer’s instructions respectively. A total of 76 individuals were tested for the presence or absence of a 23 nucleotide deletion within the 5’ untranslated region of toll like receptor 2 using allele specific real time -polymerase chain reaction (qPCR). A total of 472 individuals were screened: 307/472 (65.1%) of which were males while 165/472 (34.9%) were females. Of those, 272 were recruited for the study of which 87.86% were males and 12.14% were females. The proportion of CFA was 5.51%, that of hydrocoele was 73.2%, and that of lymphoedema was 16.0%. The proportion of hydrocoele combined with lymphoedema was 5.5%. The proportion of individuals with deletions in their toll like receptor 2 gene was 36.7 %. However, the presence of this deletion within the the TLR 2 gene was not statistically significantly associated with clinical outcome of the disease (P0.05). Our findings demonstrate a considerable low burden in filarial infection. However, there is clear evidence of ongoing transmission despite the 8 rounds of MDA. It is unlikely that the annual MDA would eliminate filarial transmission. The evidence of the presence of TLR 2 deletion genotypes in the 5’ untranslated region was found in individuals who reside in the endemic villages of Tanga region, North Eastern Tanzania, highlighting the potential for the susceptibility of bancroftian filariasis infection. These findings should inform the design of additional strategies to accelerate lymphatic filariasis control and elimination.
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    Risks of enteropathogen infection in humans and cattle associated with manure management in urban and peri-urban areas of Morogoro, Tanzania
    (Sokoine University of Agriculture, 2014) Lupindu, Athumani Msalale
    Urban population growth has created an increase in demand for food including those of animal origin. In response to ample market, urban and peri-urban livestock farming has expanded both in the number of livestock and the number of households engaged in livestock keeping. As a result, human-animal interaction has increased and concurrent increase in manure production within the same land space has increased human-manure-environment contact. The present study was aimed at investigating cattle and manure management practices and associated risks of manure-borne enteropathogen infection to humans and animals and environmental contamination in urban and peri-urban settings of Morogoro, Tanzania. One hundred and nineteen smallholder dairy cattle keeping households from urban and peri-urban areas of Morogoro municipal, Morogoro rural and Mvomero districts were randomly selected for the study. To each cattle keeping household, a non-cattle keeping neighbor from within a radius of 100m was selected and a pair formed a cluster. Administration of structured questionnaires to cattle keepers and non-cattle keepers, together with observations was used to collect information about cattle and manure management practices. Individual fecal samples were collected from all cattle present at the household registered for the study. Stool samples from individuals from cattle keeping households and non-cattle keeping neighbors as well as soil and water samples were collected for the purpose of isolating zoonotic Salmonella spp., non-sorbitol fermenting diarrheagenic E. coli and non-pathogenic commensal E. coli strains. In total, there were 446 cattle fecal, 201 stool, 201 soil and 201 water samples for bacteria isolation. Zoonotic Salmonella species were isolated on Salmonella-Shigella agar and characterized by biochemical and standard serological methods. Diarrheagenic E. coli were isolated from sorbitol MacConkey agar and characterized by conventional biochemical, serological and antimicrobial susceptibility tests and molecular methods such as PCR and DNA hybridization. The non-pathogenic E. coli isolated from MacConkey agar were screened for double resistance for ampicillin and tetracycline using Petri film Select E. coli count plate and later analysed for genetic relatedness by Pulsed Field Gel Electrophoresis (PFGE). Logistic regression was used to quantify the risks for transmission of E. coli between cattle, humans, water and soil based on PFGE results. It was revealed that cattle from different herds were allowed to mix and there was indiscriminate defecation during grazing. Manure collection, conveyance and disposal resulted into direct human contact with manure and manure was disposed off within and around residential areas either as fresh or composted. The prevalence of shiga toxin-producing E. coli (STEC) O157:H7 in cattle was 0.9% (95% CI: 0.29 –237 2.15) while the prevalence of all STEC strains in cattle was 1.6% (95% CI: 0.69 – 3.08). The overall prevalence of diarrheagenic E. coli in cattle was 2.2% (95% CI: 0.99 – 3.67) and 0.5% (95% CI: 0.025 – 2.44) in water sources. This shows that cattle remain potential source of pathogenic E. coli to humans and environment. Among the non-sorbitol fermenting E. coli isolates, one Extended Spectrum Beta Lactamase (ESBL)-producing isolate showed the Multilocus Sequence Typing (MLST) type ST131 that causes antimicrobial-resistant infections in humans. Zoonotic Salmonella strains such as Salmonella amager, S. kentucky and S. weltevreden were isolated from humans and cattle. Overall, four samples out of 1046 (0.38%) were positive, while the prevalences of Salmonella in humans and cattle were 1% and 0.45% respectively. Isolation of S. amager in asymptomatic human subject shows that, the pathogen that was previously reported to cause gastroenteritis outbreak in humans, may have lost its virulence characteristics but still exists within the human population. There was transmission of E. coli between cattle, humans, soil and water within and between clusters due to manure management. Out of 44 clusters from which ampicillin and tetracycline resistant E. coli were isolated, 16 clusters (36%) had at least one isolate that was 100% identical to another isolate but from another source within the same epidemiological unit. Cattle (OR=19.2, CI: 2.04-179.8) and manure (OR=0.4, CI: 0.17-0.89) management practices were the risk factors for E. coli transmission between cattle, humans, soil and water. Cattle and manure management practices in urban and peri-urban areas of Morogoro put humans and animals at risk of infection with pathogens including E. coli O157:H7 and ESBL producing ST131 strains while contaminating the environment. Therefore, there is a need for formulation and enforcement of manure management guidelines that safeguide human, animals and the environment.