NEW METHODS FOR THE DIAGNOSIS OF BABESIA-BIGEMINA INFECTION

Accurate diagnosis of Babesia bigemina infection, an economically impo rtant tick-transmitted protozoan parasite of cattle, is essential in t he management of disease control and in epidemiological studies. The c urrently used methods of diagnosis are blood smear examination and ser ological tests which include agglutination and immunofluorescence test s. These tests have been used in the fild but because they lack sensit ivity and specificity, newer and improved methods of diagnosis are bei ng developed. The quantitative buffy coat (QBC) method, using microhae matocrit tubes and acridine orange staining allows rapid and quicker d iagnosis of B. bigemina and other blood parasites compared to light mi croscopic examination of stained smears. Parasite specific monoclonal antibodies have been used in antigen/antibody capture enzymelinked imm unosorbent assays with greater sensitivity and specificity than previo usly described serological tests. Similarly, DNA probes, derived from a repetitive sequence of the B. bigemina genome, offer a method of det ecting very small numbers of parasites which are undetectable by conve ntional microscopy. An extrachromosonal DNA element, present in all th e tick-borne protozoan parasites so far tested, provides an accurate m eans of differentiating mixed parasite populations in infected animals . These improved methods will greatly facilitate epidemiological studi es.