The application of a combination of diagnostic tests for bovine trypanosomosis is vital for an effective control of the disease

Abstract

Four hundred thirty two cattle in 9 farms in the Coast and Dar Es Salaam regions of Tanzania were bled at different periods from March 2006 to January 2007 and specimens prepared for parasitological (buffy coat technique - BCT, blood slide examination) and serological (Antigen, Antibody, PCR ELISAs and LAMP Test) screening for presence of trypanosomes. Alongside this, 1.0 ml of EDTA blood of test animals with packed cell volume (PCV) values less than 25 was inoculated into 20 g mouse for possible detection of trypanosomes in low parasitaemic infections; were followed-up for 60 days. Four cattle were detected positive for pathogenic trypanosomes, notably Trypanosoma vivax in three cattle by blood slide examination and BCT, and T. congolense (one case) by mouse inoculation. Serological screening is not yet completed. 90.3% of animals sampled had PCV values above 25, while 42 cattle (9.7%) had PCV values below 25. Low PCV values in adult cattle in trypanosomosis-endemic areas suggest presence of trypanosome infections. Subsequent trypanocidal drug treatment of five parasitologically negative cattle with PCV of 15, 16, 18, 20 and 22 resulted into improved PCV values of ≥25 ≤27 by Day 30 after treatment with diminazene aceturate 7.0mg per kg body weight. Mouse inoculation was discriminately done on blood of parasitologically negative cattle with PCV values below 25. One pair of mice became positive for T. congolense on Day 43 and 47 of inoculation. Although results from more sensitive diagnostic tests are not yet available, the individual parasitological tests (blood slide, BCT, mouse inoculation) and trypanocidal drug treatment of low PCV-BCT-negative adult cattle have shown complementarities to one another; each option has place in perfecting trypanosomosis diagnosis for an improved control of the disease.