Ehrlichia sp. in dairy cattle from Bahia, Brazil: high seropositivity rates and molecular confirmation of Ehrlichia minasensis.

Abstract

Background: Ehrlichia spp. are obligate intracytoplasmic Gram-negative tickborne bacteria from the Anaplasmataceae family. Ehrlichiosis is considered an emerging disease in humans and animals. Studies on bovine ehrlichiosis are scarce in Northeastern Brazil. Therefore, the objectives of this work were to determine the frequency of antibodies anti-Ehrlichia sp. in dairy cattle herds in the Feira de Santana microregion, Bahia, and to confirm infection through PCR and nucleotide sequencing in selected seropositive animals.

Results: Blood samples were collected from 256 clinically healthy adult cattle from four dairy farms. Plasma from each animal was tested for Ehrlichia sp. using an indirect immunofluorescence antibody test (IFAT) and a 1:40 cutoff. Of the 256 tested samples, 249 (97.26%) were seropositive for Ehrlichia sp. Forty blood samples (10 from each farm) from IFAT-positive cattle were examined by a PCR for Ehrlichia sp. and resulted in 13 infected animals; DNA samples from six PCR-positive cows were sequenced and matched 100% with Ehrlichia minasensis.

Conclusions: The results represent the first serological and molecular evidence of E. minasensis in cattle from Bahia state and northeastern Brazil. Despite the limited number of tested cattle, the high frequency of seropositive animals in four farms suggests that Ehrlichia sp. is widely disseminated in the studied microregion. Considering that the infected cattle were asymptomatic, it is possible that they developed protective immunity against Ehrlichia sp.