ABSTRACT
The prevalence of Babesia bovis antibodies was estimated by using an ELISA (98% sensitivity and 95% specificity). Sera were obtained from 165 calves (mean age and standard deviation: 9.7 +/- 2.7 months) from an area in Argentina known to be unfavourable for the development of the vector tick, Boophilus microplus. The area comprised about 300,000 ha used for cattle breeding. The cattle population of 55,000 included 12,000 cattle under 1 year of age. Cattle were maintained mainly on natural grasses in communal lands. The true prevalence of antibodies to Babesia bovis was 12.2% with a confidence interval of 7.6% to 18.2%, and an inoculation rate (h; daily probability of infection) of 0.0004. This confidence interval has its lower boundary in the area of endemic stability due to low h of Babesia bovis by the vector tick and the upper limit in the area of endemic instability. This type of analysis could help to decide the implementation of preventive measures (e.g. vaccination) rationally, even in remote areas (such as the one of the present study) with an extensive cattle industry.
