Estudo epidemiológico da tristeza parasitária bovina no Estado da Paraíba.

Abstract

This thesis contains three articles on the epidemiology of tick fever in the semiarid region of Paraíba. The first chapter is an article that describes the occurrence of outbreaks of tick fever in the semiarid region of Paraiba, 18 of anaplasmosis by Anaplasma marginale, two of babesiosis by Babesia bigemina, two by unidentified Babesia and two by mixed infection with Anaplasma marginale and Babesia sp. The outbreaks were concentrated at the end of the rainy season and early dry season each year. Twenty two occurred in adult cattle and two in of calves of approximately 11 months-old. Two outbreaks occurred in Nelore cattle, one in Gir, and the remaining 21 occurred in animals of the Holstein or Brown Swiss breeds or crosses of these breeds with Zebu cattle. In the second chapter we investigated the seroprevalence of A. marginale, B. bigemina, B. bovis and T. vivax in cattle, as well as the risk factors for these infections. The presence of antibodies in the serum of animals was detected by indirect immunofluorescence (IFA), using specific antigens. Mean values for farm seroprevalence was 15.0% (0-75%) for A. marginale, 9.5% (0-40%) for B. bigemina, and 26.9% (0 to 73.7%) for B. bovis. In the third chapter the incidence of natural infection by A. marginale, B. bovis and B. bigemina in calves was monitored each 14 days from one to 12 months-old in 5 farms in the semiarid region of Paraíba. By polymerase chain reaction (PCR), the incidence of A. marginale infections were 0%, 83.3%, 85.7%, 100%, and 100%. The incidence of B. bigemina infections were 12.5% and 85.7% in two farms. Infection with B. bovis was observed only in one farm with incidence of 42.8%. By the detection of antibodies by the IFA the incidence of infections by A. marginale in 5 farms were, respectively, 0%, 50%, 42.8%, 14.3% and 28.6%. Seropositivity to B. bigemina and B. bovis was found in only two farms, with incidences of 57.1% and 71.4%, respectively. It is concluded that the semiarid region of Paraíba is of enzootic instability for tick fever.