Browsing by Author "Nthiwa, Daniel, M."

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    Association between land use change and exposure to zoonotic pathogens – Evidence from selected case studies in Africa.
    (Elsevier, 2018-09) Bett, B.; Ngwili, N.; Nthiwa, Daniel, M.; Alonso, S.
    The demand for food and other ecosystem services have risen in the recent past in many parts of the world due to increasing human population. This has promoted agricultural intensification and increased extraction of natural resources particularly in the sub-Saharan Africa where people derive livelihoods from their local environments. These developments invariably influence transmission patterns (positively or negatively) for a wide range of infectious diseases. In this paper, three case studies from East and southern Africa are used to demonstrate linkages between land use change and risk of exposure to zoonotic diseases. They identify two common processes that influence disease risk including (i) modification of vector, pathogen and host niches, and (ii) changes in reservoir host population distribution. Potential ways of managing disease risks in each case are also discussed.
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    Incidence of Brucella infection in various livestock species raised under the pastoral production system in Isiolo County, Kenya
    (BMC, 2021-10) Njeru, Josiah; Nthiwa, Daniel, M.; Akoko, James; Oyas, Harry; Bett, Bernard
    Background: We implemented a longitudinal study to determine the incidence of Brucella infection in cattle, camels, sheep and goats that were being raised in a pastoral area in Isiolo County, Kenya. An initial cross-sectional survey was implemented to identify unexposed animals for follow up; that survey used 141 camels, 216 cattle, 208 sheep and 161 goats. Sera from these animals were screened for Brucella spp. using the Rose Bengal Plate test (RBPT), a modiied RBPT, and an indirect multispecies Enzyme Linked Immunosorbent Assay (iELISA). Results of RBPT and iELISA were interpreted in parallel to determine seroprevalence. A total of 30 camels, 31 cattle, 22 sheep and 32 goats that were seronegative by all the above tests were recruited in a subsequent longitudinal study for follow up. These animals were followed for 12 months and tested for anti-Brucella antibodies using iELISA. Seroconversion among these animals was deined by a positive iELISA test following a negative iELISA result in the previous sampling period. All seropositive samples were further tested using real-time PCR-based assays to identify Brucella species. These analyses targeted the alkB and BMEI1162 genes for B. abortus, and B. melitensis, respectively. Data from the longitudinal study were analysed using Cox proportional hazards model that accounted for within-herds clustering of Brucella infections. Results: The overall incidence rate of Brucella infection was 0.024 (95% conidence interval [CI]: 0.014–0.037) cases per animal-months at risk. Brucella infection incidence in camels, cattle, goats and sheep were 0.053 (0.022–0.104), 0.028 (0.010–0.061), 0.013 (0.003–0.036) and 0.006 (0.0002–0.034) cases per animal-month at risk, respectively. The incidence rate of Brucella infection among females and males were 0.020 (0.009–0.036) and 0.016 (0.004–0.091), respectively. Real-time PCR analyses showed that B. abortus was more prevalent than B. melitensis in the area. Results of multivariable Cox regression analysis identiied species (camels and cattle) as an important predictor of Brucella spp. exposure in animals. Conclusions: This study estimated an overall brucellosis incidence of 0.024 cases per animal-months at risk with camels and cattle having higher incidence than sheep and goats. These results will inform surveillance studies in the area.