Fascioliasis in cattle in Louisiana: development of a system to predict disease risk by climate, using the Thornthwaite water budget.
A system correlating climate with the annual risk of fascioliasis in cattle in central Louisiana was developed, using the Thornthwaite water budget and a 6-year data base that included records on herd prevalence rates, transmission to fluke-free sentinel calves, and snail population dynamics. The system developed was compared with modifications of the wet-day and Mt forecasting systems previously developed for use in the oceanic climate zone of western Europe. The wet-day system correlated poorly with transmission data, whereas the Mt and Thornthwaite water budget-derived systems correctly ranked 5 of the 6 years in terms of annual numbers of flukes transmitted to sentinel calves. Compared with the Mt system, the water budget-based system more closely correlated with transmission data, on the basis of statistical regression analysis. The water budget system was calculated by use of a microcomputer software program, and provided a means of measuring the effect of moisture stress and flooding in snail habitats that serve as foci of transmission of Fasciola hepatica to cattle on pastures.
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000469:parasitology* / Q000635:transmission; D002980:Climate; D005210:Fasciola hepatica; D005211:Fascioliasis / Q000453:epidemiology / Q000635:transmission / Q000662:veterinary*; D008145:Louisiana; D008297:Male; D012306:Risk; D012908:Snails / Q000469:parasitology; D014881:Water Supply