EVALUATION OF A COLORIMETRIC BABESIA-BIGEMINA-DNA PROBE WITHIN AN EPIDEMIOLOGIC SURVEY

An epidemiological survey was conducted in southeast Mexico, in an eff ort to establish the serological reactivity and carrier status to Babe sia bigemina of an indigenous cattle population. The prevalence was ob tained through the Indirect Fluorescent Antibody Test (IFAT), using an in vitro culture-derived B. bigemina antigen. A specific, digoxigenin -coupled, approximately 6 Kb B. bigemina-DNA probe (BBDP), was used to indicate the presence of the parasite. Serum samples from 925 animals of all ages, were obtained within the three regions (I, II, III) of t he state of Yucatan and tested by IFAT In addition, whole blood sample s drawn from 13 6 of the same animals of region II were analyzed using the BBDP. Positive IFAT (IFAT+) reactions were observed in 531 sera f or a 57% overall prevalence. Regional values were: I = 157+ (56%), II = 266+ (68%) and III 108+ (42%). Only 32 (23%) of the blood samples te sted with BBDP showed distinctive hybridization signal, in contrast wi th 100 (73%) IFAT+ animals. The response distribution for IFAT vs. BBD P was: +/+ 23, +/- 77, -/+ 9 and -/- 2 7 respectively. It was found th at the analytical sensitivity of BBDP appears to be low for its utiliz ation in widespread epidemiological surveys. It was considered, howeve r, that the colorimetric probe might be useful to safely detect transm ission prone carriers, since it is able to detect parasitemias as low as 0.001%.