Browsing by Author "Travis, Dominic A."

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    Environmental Determinants Influencing Anthrax Distribution in Queen Elizabeth Protected Area, Western Uganda
    (Plos one, 2020) Driciru, Margaret; Rwego, Innocent B.; Ndimuligo, Sood A.; Travis, Dominic A.; Mwakapeje, Elibariki R.; Asiimwe, Benon; Ayebare, Samuel; Pelican, Katharine
    Bacillus anthracis, the bacteria that causes anthrax, a disease that primarily affects herbivorous animals, is a soil borne endospore-forming microbe. Environmental distribution of viable spores determines risky landscapes for herbivore exposure and subsequent anthrax outbreaks. Spore survival and longevity depends on suitable conditions in its environment. Anthrax is endemic in Queen Elizabeth Protected Area in western Uganda. Periodic historical outbreaks with significant wildlife losses date to 1950s, but B. anthracis ecological niche in the ecosystem is poorly understood. This study used the Maximum Entropy modeling algorithm method to predict suitable niche and environmental conditions that may support anthrax distribution and spore survival. Model inputs comprised 471 presence-only anthrax occurrence data from park management records of 1956–2010, and 11 predictor variables derived from the World Climatic and Africa Soil Grids online resources, selected considering the ecology of anthrax. The findings revealed predicted suitable niche favoring survival and distribution of anthrax spores as a narrow-restricted corridor within the study area, defined by hot-dry climatic conditions with alkaline soils rich in potassium and calcium. A mean test AUC of 0.94 and predicted probability of 0.93 for anthrax presence were registered. The five most important predictor variables that accounted for 93.8% of model variability were annual precipitation (70.1%), exchangeable potassium (12.6%), annual mean temperature (4.3%), soil pH (3.7%) and calcium (3.1%). The predicted suitable soil properties likely originate from existing sedimentary calcareous gypsum rocks. This has implications for long-term presence of B. anthracis spores and might explain the long history of anthrax experienced in the area. However, occurrence of suitable niche as a restricted hot zone offers opportunities for targeted anthrax surveillance, response and establishment of monitoring strategies in QEPA.
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    Leptospira Seroprevalence and Risk Factors in Health Centre Patients in Hoima District, Western Uganda
    (PLoS Neglected Tropical Diseases, 2016) Dreyfus, Anou; Dyal, Jonathan W.; Pearson, Raewynne; Kankya, Clovice; Kajura, Charles; Alinaitwe, Lordrick; Kakooza, Steven; Pelican, Katharine M.; Travis, Dominic A.; Mahero, Michael; Boulware, David R.; Mugisha, Lawrence
    The burden of human leptospirosis in Uganda is unknown. We estimated the seroprevalence of Leptospira antibodies, probable acute/recent leptospirosis, and risk factors for seropositivity in humans in rural Western Uganda. Methodology and Principal Findings 359 non-pregnant adults visiting the Kikuube and Kigorobya Health Centers were sequentially recruited during March and April 2014. A health history survey and serum were collected from consented participants. Overall, 69% reported having fever in the past year, with 49% reporting malaria, 14% malaria relapse, 6% typhoid fever, 3% brucellosis, and 0% leptospirosis. We tested sera by microscopic agglutination test (MAT) against eight Leptospira serovars representing seven serogroups. Leptospira seroprevalence was 35% (126/ 359; 95%CI 30.2–40.3%) defined as MAT titer 1:100 for any serovar. The highest prevalence was against L. borgpetersenii Nigeria (serogroup Pyrogenes) at 19.8%(71/359; 95% CI 15.9–24.4%). The prevalence of probable recent leptospirosis (MAT titer 1:800) was 1.9% (95%CI 0.9–4.2%) and uniquely related to serovar Nigeria (serogroup Pyrogenes). Probable recent leptospirosis was associated with having self-reported malaria within the past year (p = 0.048). Higher risk activities included skinning cattle (n = 6) with 12.3 higher odds (95%CI 1.4–108.6; p = 0.024) of Leptospira seropositivity compared with those who had not. Participants living in close proximity to monkeys (n = 229) had 1.92 higher odds (95%CI 1.2–3.1; p = 0.009) of seropositivity compared with participants without monkeys nearby. Conclusions/Significance The 35% prevalence of Leptospira antibodies suggests that exposure to leptospirosis is common in rural Uganda, in particular the Nigeria serovar (Pyrogenes serogroup). Leptospirosis should be a diagnostic consideration in febrile illness and “smear-negative malaria” in rural East Africa.
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    Spatio-temporal Epidemiology of Anthrax in Hippopotamus Amphibious in Queen Elizabeth Protected Area, Uganda
    (PLoS One, 2018) Driciru, Margaret; Rwego, Innocent B.; Asiimwe, Benon; Travis, Dominic A.; Alvarez, Julio; VanderWaal, Kimberly; Pelican, Katharine
    Anthrax is a zoonotic disease primarily of herbivores, caused by Bacillus anthracis, a bacterium with diverse geographical and global distribution. Globally, livestock outbreaks have declined but in Africa significant outbreaks continue to occur with most countries still categorized as enzootic, hyper endemic or sporadic. Uganda experiences sporadic human and livestock cases. Severe large-scale outbreaks occur periodically in hippos (Hippopotamus amphibious) at Queen Elizabeth Protected Area, where in 2004/2005 and 2010 anthrax killed 437 hippos. Ecological drivers of these outbreaks and potential of hippos to maintain anthrax in the ecosystem remain unknown. This study aimed to describe spatio-temporal patterns of anthrax among hippos; examine significant trends associated with case distributions; and generate hypotheses for investigation of ecological drivers of anthrax.Spatio-temporal patterns of 317 hippo cases in 2004/5 and 137 in 2010 were analyzed. QGIS was used to examine case distributions; Spearman’s nonparametric tests to determine correlations between cases and at-risk hippo populations; permutation models of the spatial scan statistics to examine spatio-temporal clustering of cases; directional tests to determine directionality in epidemic movements; and standard epidemic curves to determine patterns of epidemic propagation.Results showed hippopotamus cases extensively distributed along water shorelines with strong positive correlations (p<0.01) between cases and at-risk populations. Significant (p<0.001) spatio-temporal clustering of cases occurred throughout the epidemics, pointing towards a defined source. Significant directional epidemic spread was detected along water flow gradient (206.6°) in 2004/5 and against flow gradient (20.4°) in 2010. Temporal distributions showed clustered pulsed epidemic waves.These findings suggest mixed point-source propagated pattern of epidemic spread amongst hippos and points to likelihood of indirect spread of anthrax spores between hippos mediated by their social behaviour, forces of water flow, and persistent presence of infectious carcasses amidst schools. This information sheds light on the epidemiology of anthrax in highly social wildlife, can help drive insight into disease control, wildlife conservation, and tourism management, but highlights the need for analytical and longitudinal studies aimed at clarifying the hypotheses.