MOLECULAR DETECTION AND SEROPREVALENCE OF Ehrlichia sp. IN DAIRY CATTLE FROM BRAZIL’S WESTERN AMAZON REGION

Abstract

Ehrlichia minasensis, a novel species of Ehrlichia that is closely related to E. canis, is known to infect cattle and deer in Canada. This rickettsial bacterium was isolated from Rhipicephalus (Boophilus) microplus ticks and from dairy and beef cattle in southeast and midwestern Brazil, respectively. The purpose of this study was to determine the seroprevalence and perform molecular detection of Ehrlichia sp. in dairy cattle in the northern region of Brazil. The study was conducted in the municipality of Ji-Paraná, located in the state of Rondônia in the western Brazilian Amazon region. Blood and serum samples were obtained between the dates September 2012 and November 2013 from dairy cows (≥ 24 months old) in 64 farms. The blood samples were subjected to polymerase chain reaction (PCR) to amplify a fragment of the Ehrlichia sp. dsb gene, and the levels of Ehrlichia sp. antibodies were measured by the immunofluorescence assay (IFA). A total of 15 of 610 (2.45%; 95% CI: 1.04-3.86%) blood samples tested positive for ehrlichial infection based on the detection of the Ehrlichia sp. dsb gene. Sequencing of PCR amplicons from samples confirmed that the amplified partial dsb gene (~295 base pairs) sequence represented E. minasensis. Anti-Ehrlichia sp. antibodies were detected in 178 cows (53.96%; 95% CI: 46.63–61.29%). Endpoint titers ranged from 40 to 5,120. However, positive results derived from this assay should be interpreted with caution. Among the variables analyzed using IFA, the number of cows aged 24 months or greater was statistically significant (p = 0.0103), and hers of approximately 51-100 cows were more likely to be infected with Ehrlichia sp. Although the animals do not show clinical disease, the chronic character of the infection can lead to decrease in productivity.