Epidemiology of babesiosis and anaplasmosis in South and Central America.

Babesiosis (Babesia bovis and Babesia bigemina) and anaplasmosis (Anaplasma marginale) affect native cattle from Uruguay and northern Argentina to Guatemala. The distribution of Babesia follows the dissemination of the tick vector. Seroepidemiological studies showed that enzootic instability exist in herds in several areas of the region. However, clinical cases occurred less frequently than expected. The babesial tick infection rate is related to the vector abundance which in turn is regulated by climate. Bos indicus cattle, because of tick resistance, are less likely to be infected by the vector. This can result in herd instability, but clinically is partly compensated by the resistance of Bos indicus and their crosses to babesiosis. Excessive use of acaricides and rotational grazing appears to be related to outbreaks of babesiosis especially in dairy cattle. Factors involved in the epidemiology and transmission of anaplasmosis are not well defined. The role of ticks, haematophagous diptera, iatrogenic and intrauterine transmissions needs to be investigated under local conditions. Therefore, the knowledge of this disease is meager. Utilization of biotechnological methods may help in obtaining information on Babesia-Boophilus-Bos relationship and on the transmission of A. marginale.