Risk of babesiosis and anaplasmosis in different ecological zones of SantaCruz Department, Bolivia

A cross-sectional study was done of seroprevalence of Babesia bigemina, B. bovis, and Anaplasma marginale in cattle from eastern Bolivia, to character ize the risk of tick-borne disease in three ecological zones. Nineteen farm s were sampled in the subtropical humid zone, 13 in the dry subtropical zon e and nine in the lower western valleys of the Andean massif. The enzyme-li nked immunosorbent assay was used. All three pathogens were widespread. For B. bovis, seroprevalences were high (75-78%) in the two subtropical zones which thus had low risk of disease from this infection; but the western val leys were endemically unstable with higher risk. For B bigemina, seropreval ences were lower (24-57%) in the two subtropical zones and thus these areas were endemically unstable for disease from this infection. However, the se roprevalence of B. bigemina in the western valleys was too low (13%) for ri sk of disease in susceptible cattle to be considered high. For A. marginale , the seroprevalences in the two subtropical zones were low (19-32%) and ve ry low (6%) in the western valleys suggesting all these zones were endemica lly unstable for anaplasmosis. Data for individual farms were analysed for risk of both forms of babesiosis; this showed low risk of disease in the su btropical humid zone, higher risk in the dry subtropical zone and variable risk in the western valleys. (C) 2000 Elsevier Science B.V. All rights rese rved.