Epidemiologic aspects of an outbreak of Trypanosoma vivax in a dairy cattle herd in Minas Gerais state, Brazil.

The aim of this study was to assess the epidemiological situation of bovine trypanosomiasis caused by Trypanosoma vivax in a dairy cattle herd from Igarapé, Minas Gerais state, Brazil. The herd was monitored from September 2007 to February 2009 by sampling blood for determination of packed cell volume (PCV), microhaematocrit centrifugation test of parasitaemia (MHCT), serology (IFA), morphological identification of T. vivax and molecular diagnosis by polymerase chain reaction (PCR). During all the experimental period, 25 animals were MHCT and PCR positive, considering that in each sample collection a mean of 70 animals was evaluated. The morphometric characteristics of trypomastigote forms confirmed the infection by T. vivax. The seroprevalence ranged from 7.4% in September 2007 to 48% in February 2009, and the highest incidence observed could be correlated with an increased population of Stomoxys calcitrans flies in that region. Anaemia was the most important change found in infected animals, which showed lower averages of PCV than parasitologically negative animals (p<0.0001). Infected individuals showed lower averages of PCV than parasitologically negative animals (p<0.0001), indicating higher anaemia in the former compared with the latter group.