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Theileria parva epidemics: a case study in eastern Zambia
M Billiouw1, J Vercruysse, T Marcotty
1Department of Animal Health, Institute of Tropical Medicine, Antwerpen, Belgium.
Veterinary Parasitology
|June 20, 2002
Summary
East Coast fever (ECF) epidemics in Zambia are driven by tick transmission, with cattle population size being a key factor. ECF is often underestimated, impacting financial costs and requiring targeted vaccination strategies.
Area of Science:
- Veterinary Epidemiology
- Tropical Animal Health
Background:
- East Coast fever (ECF) is a significant cattle disease in eastern Zambia.
- Understanding ECF transmission dynamics is crucial for effective control.
Purpose of the Study:
- To monitor ECF epidemic dynamics in sentinel cattle herds.
- To analyze the impact of tick populations and cattle susceptibility on disease spread.
- To evaluate ECF monitoring tools and propose optimal vaccination timing.
Main Methods:
- Clinical and serological monitoring of sentinel herds (1994-2000).
- Detailed counts of Rhipicephalus appendiculatus ticks.
- Analysis of disease incidence, case-fatality, and financial costs.
Main Results:
- ECF incidence peaks in rainy and dry seasons, driven by nymph-to-adult tick transmission.
- Adult tick waves and susceptible cattle populations are critical for epidemics.
- Case-fatality ratio estimated at 60%, with underestimation of ECF mortality.
- Direct financial cost estimated at $6/animal/year.
- Maternal antibody prevalence proposed as an alternative monitoring tool.
Conclusions:
- ECF occurrence and mortality are systematically underestimated.
- Vaccination campaigns should target periods of low adult tick abundance (July-October).
- Traditional seroprevalence surveys may be less effective than monitoring maternal antibodies.