Browsing by Author "Mgode, G."
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Item Active tuberculosis detection by pouched rats in 2014: more than 2,000 new patients found in two countries(2016 Society for the Experimental Analysis of Behavior, 2016) Poling, A.; Beyene, N.; Valverde, E.; Mulder, C.; Cox, C.; Mgode, G.; Edwards, T. L.Tuberculosis (TB) is a major problem in poor countries because sensitive diagnostic tools are unavail- able. In 2014, our pouched rats evaluated sputum from 21,600 Tanzanians and 9,048 Mozambicans whose sputum had previously been evaluated by microscopy, the standard diagnostic for TB. Evalua- tion by the rats revealed 1,412 new patients with active TB in Tanzania and 645 new patients in Mozambique, increases of 39% and 53%, respectively, when compared to detections by microscopy alone. These results provide further support for the applied use of scent-detecting rats.Item The pattern of reproduction in the mole-rat Heliophobius from Tanzania: do not refrain during the long rains!(NRC Research Press, 2016) Ngalameno, M. K.; Bastos, A. D. S.; Mgode, G.; Bennett, N. C.The genus Heliophobius Peters, 1846 comprises at least six cryptic, topotypical species in the Heliophobius argenteocinereus Peters, 1846 species complex. The current study investigated the breeding patterns of a wild-caught population from Tanzania where the putative species Heliophobius argenteocinereus emini Noack, 1894 resides. Individuals were collected on a monthly basis for an entire calendar year. Assessment of fœtus presence, gonadal histology, reproductive-tract morphometrics in combination with gonadal steroid (plasma progesterone and œstradiol-17 in females and testosterone in males) measurements and field observations revealed that rainfall is important for the onset of breeding. The results further confirmed that breeding is limited to a single, yearly reproductive event synchronised to the long rainfall pattern. The distinct breeding peak in July is associated with an elevation in gonadal mass, increase in concentrations of reproductive hormones, and presence of Graafian follicles and corpora lutea in the ovaries of females. These reproductive parameters coincided with the end of the long rainfall period, whereas presence of young in the maternal burrow system corresponded with the start of the short rainfall of East Africa. These findings confirm Heliophobius has a single breeding opportunity each year, and this species is therefore vulnerable to any changes that may impact their climatically attuned breeding patterns.Item Rapid molecular evolution of pain insensitivity in multiple African rodents(Science sciencemag, 2019-05-31) Eigenbrod, O.; Debus, K. Y.; Reznick, J.; Bennett, N. C.; Sánchez-Carranza, O.; Omerbašić, D.; Hart, D. W.; Barker, A. J.; Zhong, W.; Lutermann, H.; Katandukila, J. V.; Mgode, G.; Park, T. J.; Lewin, G. R.Noxious substances, called algogens, cause pain and are used as defensive weapons by plants and stinging insects. We identified four previously unknown instances of algogen-insensitivity by screening eight African rodent species related to the naked mole-rat with the painful substances capsaicin, acid (hydrogen chloride, pH 3.5), and allyl isothiocyanate (AITC). Using RNA sequencing, we traced the emergence of sequence variants in transduction channels, like transient receptor potential channel TRPA1 and voltage-gated sodium channel Na v 1.7, that accompany algogen insensitivity. In addition, the AITC-insensitive highveld mole-rat exhibited overexpression of the leak channel NALCN (sodium leak channel, nonselective), ablating AITC detection by nociceptors. These molecular changes likely rendered highveld mole-rats immune to the stings of the Natal droptail ant. Our study reveals how evolution can be used as a discovery tool to find molecular mechanisms that shut down pain.Item The role of rodents and small carnivores in plague endemicity in Tanzania(2005-12) Kilonzo, B.; Mhina, J.; Sabuni, C.; Mgode, G.Between 1974 and 2003, blood samples were collected from wild and commensal rodents, and wild and domestic small carnivores in selected villages of seven districts in Tanzania that have experienced human plague outbreaks and seven districts that have not experienced any outbreak of the disease. The samples were tested for antibodies against Yersinia pestis Fraction I antigen, using passive haemagglutination (PHA) or ELISA tests. Of the 3354 rodents and 558 small carnivores from the plague infected districts, 122 (3.6%) rodents (captured in Mbulu and Lushoto districts) were plague positive; 29 (5.2%) small carnivores from Mbulu, Arumeru, Hai and Lushoto districts were plague positive, 28 of these were domestic dogs (Canis familiaris). PCR tests showed that 17.5% of 211 rodents tested from Lushoto contained Y. pestis DNA. In the non-infected districts, 1545 rodents and 171 domestic dogs were tested. 11 (0.7%) of the rodents (captured in Monduli, Chunya and Masasi districts) were plague-positive. In Masasi district, 10.4% (7/67) of the rodents and 43.6% (17/39) of the dogs were positive for anti-Y. pestis IgG. It was concluded that wild and commensal rodents as well as wild and domestic small carnivores play a potential role as reservoirs and/or carriers of sylvatic plague in Tanzania, and that the disease exists in areas where human plague outbreaks have not occurred before. In order to update the distribution of the disease it is proposed that further epidemiological surveillance activities are established.Item Tuberculosis detection by pouched rats: Opportunities for reinforcement under low-prevalence conditions(2017 Elsevier B.V, 2017) Edwards, T. L.; Ellis, H.; Watkins, E. E.; Mulder, C.; Mgode, G.; Cox, C.; Poling, A.Giant African pouched rats (Cricetomys ansorgei) have been employed successfully in two operational tuberculosis-detection projects in which they sniff sputum samples from symptomatic individuals who have visited tuberculosis clinics. The prevalence of pulmonary tuberculosis in this population is high, approximately 20% in the regions where the rats have been used. If the rats are to be used to screen individuals from lower- prevalence populations, their performance under such conditions must first be evaluated. In this study, the prevalence of tuberculosis-positive samples presented to eight pouched rats was reduced to approximately 5%, and the percentage of known-positive samples included as opportunities for reinforcement was varied in sequence from 10 to 8, 6, 4, 2, 4, and 2. Liquid food reinforcers were delivered for identification responses to known-positive samples and at no other time. The rats’ accuracy was clinically and statistically significantly lower at 2% than at the other values. These results indicate that the rats can perform well in low-prevalence scenarios but, if they are used under the conditions of the present study, at least 4% of the samples presented to them must be opportunities for reinforcement.Item Tuberculosis diagnostic technology: an African solution ... think rats(AOSIS, 2017-03-31) Mulder, C.; Mgode, G.; Reid, S. E.Introduction Tuberculosis has now gained ranking alongside HIV as one of the two leading causes of death from infectious diseases worldwide. 1 In 2014, it was estimated that 1.5 million people died as a result of and 9.6 million fell ill with tuberculosis. 1 Despite these alarming figures, efforts to reduce the annual tuberculosis incidence rate over the last decade have resulted in only a meagre 1.5% decline. 1 In order to reach the ambitious targets of the Sustainable Development Goals by 2030 of reducing tuberculosis deaths by 90%, reducing the tuberculosis incidence rate by 90%, and ensuring that no tuberculosis-affected family is facing catastrophic costs due to tuberculosis, a paradigm shift is urgently needed. 1 Recently, a series of papers was published in The Lancet on how to eliminate tuberculosis, suggesting repacking current interventions into a comprehensive control strategy. 2 The World Health Organization End TB Strategy supports this and also emphasises the need for better adoption and rapid uptake of new tools to diagnose tuberculosis earlier, the systematic screening of high-risk populations, and the effective and rapid roll-out of these strategies in highly-affected countries. 3 However, the practicality of achieving these components remains challenging because of the lack of a rapid, simple, accurate and affordable point-of-care diagnostic and screening algorithm that can be scaled-up to screen large numbers of individuals. Nevertheless, achievement of these goals is necessary and must catalyse the development of new interventions in Africa, for Africa, the continent with the highest tuberculosis mortality and morbidity rates.Item Using giant african pouched rats to detect human tuberculosis: a review(2015) Poling, A; Mahoney, A; Beyene, N; Mgode, G.; Weetjens, B; Cox, c; Durgin2, ADespite its characteristically low sensitivity, sputum smear microscopy remains the standard for diagnosing tuberculosis (TB) in resource-poor countries. In an attempt to develop an alternative or adjunct to microscopy, researchers have recently examined the ability of pouched rats to detect TB-positive human sputum samples and the microbiological variables that affect their detection. Ten published studies, reviewed herein, suggest that the rats are able to detect the specific odor of Mycobacterium tuberculosis, which causes TB, and can substantially increase new-case detections when used for second-line TB screening following microscopy. Further research is needed to ascertain the rats' ability to detect TB in children and in HIV-positive patients, to detect TB when used for first-line screening, and to be useful in broad-scale applications where costeffectiveness is a major consideration.Item Using giant african pouched rats to detect human tuberculosis: A review(Pan African Medical Journal, 2015-08-31) Poling, A.; Mahoney, A.; Beyene, N.; Mgode, G.; Weetjens, B.; Cox, C.; Durgin, A.Despite its characteristically low sensitivity, sputum smear microscopy remains the standard for diagnosing tuberculosis (TB) in resource-poor countries. In an attempt to develop an alternative or adjunct to microscopy, researchers have recently examined the ability of pouched rats to detect TB-positive human sputum samples and the microbiological variables that affect their detection. Ten published studies, reviewed herein, suggest that the rats are able to detect the specific odor of Mycobacterium tuberculosis , which causes TB, and can substantially increase new-case detections when used for second-line TB screening following microscopy. Further research is needed to ascertain the rats' ability to detect TB in children and in HIV-positive patients, to detect TB when used for first-line screening, and to be useful in broad-scale applications where cost- effectiveness is a major consideration.