title: Disaggregating Tropical Disease Prevalence by Climatic and Vegetative Zones within Tropical West Africa.
abstract: Tropical infectious disease prevalence is dependent on many socio-cultural determinants. However, rainfall and temperature frequently underlie overall prevalence, particularly for vector-borne diseases. As a result these diseases have increased prevalence in tropical as compared to temperate regions. Specific to tropical Africa, the tendency to incorrectly infer that tropical diseases are uniformly prevalent has been partially overcome with solid epidemiologic data. This finer resolution data is important in multiple contexts, including understanding risk, predictive value in disease diagnosis, and population immunity. We hypothesized that within the context of a tropical climate, vector-borne pathogen prevalence would significantly differ according to zonal differences in rainfall, temperature, relative humidity and vegetation condition. We then determined if these environmental data were predictive of pathogen prevalence. First we determined the prevalence of three major pathogens of cattle, Anaplasma marginale, Babesia bigemina and Theileria spp, in the three vegetation zones where cattle are predominantly raised in Ghana: Guinea savannah, semi-deciduous forest, and coastal savannah. The prevalence of A. marginale was 63%, 26% for Theileria spp and 2% for B. bigemina. A. marginale and Theileria spp. were significantly more prevalent in the coastal savannah as compared to either the Guinea savanna or the semi-deciduous forest, supporting acceptance of the first hypothesis. To test the predictive power of environmental variables, the data over a three year period were considered in best subsets multiple linear regression models predicting prevalence of each pathogen. Corrected Akaike Information Criteria (AICc) were assigned to the alternative models to compare their utility. Competitive models for each response were averaged using AICc weights. Rainfall was most predictive of pathogen prevalence, and EVI also contributed to A. marginale and B. bigemina prevalence. These findings support the utility of environmental data for understanding vector-borne disease epidemiology on a regional level within a tropical environment.
authors.affiliation: Animal Research Institute, The Council for Scientific and Industrial Research (CSIR), Frafraha, Accra, Ghana.
authors.forename: Carl S
authors.initials: CS
authors.lastname: Beckley
authors.affiliation: Department of Animal Science, College of Basic and Applied Sciences, University of Ghana, Legon, Ghana.
authors.forename: Salisu
authors.initials: S
authors.lastname: Shaban
authors.affiliation: Program in Vector-Borne Diseases, Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, United States of America.|Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, United States of America.
authors.forename: Guy H
authors.initials: GH
authors.lastname: Palmer
authors.affiliation: Rocky Mountain Research Station, Forest Service, U.S. Department of Agriculture, Moscow, ID, United States of America.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Hudak
authors.affiliation: Animal Disease Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Pullman, WA, United States of America.|Program in Vector-Borne Diseases, Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, United States of America.|Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, United States of America.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Noh
authors.affiliation: Department of Animal Science, College of Basic and Applied Sciences, University of Ghana, Legon, Ghana.|Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, United States of America.
authors.forename: James E
authors.initials: JE
authors.lastname: Futse
mesh_terms: D000354:Africa, Western / Q000453:epidemiology; D000818:Animals; D001947:Breeding; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000469:parasitology / Q000635:transmission; D005843:Geography; D065948:Grassland; D006813:Humidity; D016014:Linear Models; D060885:Multiplex Polymerase Chain Reaction; D015995:Prevalence; D011891:Rain; D018401:Sample Size; D013696:Temperature; D013987:Ticks / Q000502:physiology; D014329:Tropical Climate