EPIDEMIOLOGY OF TROPICAL THEILERIOSIS (THEILERIA-ANNULATA INFECTION OF CATTLE) IN AN ENDEMIC REGION OF TUNISIA - CHARACTERIZATION OF ENDEMICITY STATES

A serological survey on tropical theileriosis was conducted on a sampl e of 54 farms in a region within the semi-arid bioclimatic zone of Tun isia. Screening of cattle sera at a dilution of 1/160 using the indire ct immunofluorescent antibody test with the schizont antigen of Theile ria annulata, revealed the presence of animals with positive sera in 9 2.15% of the sampled farms. The exposure of calves to infection in the first season was shown to be significantly lower than in older cattle . Three endemic situations were identified based on the serological pr ofiles of herds and the incidence and age distribution of disease case s. Endemic stability was observed in farms showing a sere-prevalence o f 100% in calves at first disease season. Low endemic instability was recognized by a sere-prevalence of 100% in cattle of four theileriosis seasons or more and by the incidence of the highest disease levels in cattle at their second and third theileriosis season, High endemic in stability was identified on the basis of low sere-prevalence rates and the occurrence of the highest disease incidence in cattle at fourth t heileriosis season or more.