Seroprevalence and molecular detection of Anaplasma marginale infected beef herds in Georgia, USA

Abstract

The objective of the study was to conduct and compare serop­revalence and molecular detection of Anaplasma marginale-in­fected beef herds in Georgia, and to identify herd risk factors associated with A. marginale-positive herds. Herd informa­tion from the beef operations was collected from the sampled herds through a questionnaire to determine practices that may affect the risk of herd infections with A. marginale. Blood samples were collected from 1,059 adult beef cattle (≥ 2 years) from 33 herds. Overall, 8.12% of cattle and 42% of herds were cELISA antibody-positive. Seventy-seven percent of plasma samples from a subset of corresponding seropositive samples (n = 73) were PCR positive. All of the 406 seronegative samples were negative by PCR. There was almost perfect agreement by Cohen’s kappa statistics between PCR and cELISA (k = 0.85). Survey response rate was 100%. Surprisingly, 27% of the pro­ducer respondents had not heard of anaplasmosis. Survey also revealed that many producers had management procedures at their operations that could potentially cause mechanical transmission of A. marginale. About 55% of respondents did not always disin­fect tools between animals and 88% of the operations used the same needle to inject more than one animal. Over 80% of the producer respondents had brought in new cattle onto their op­erations in the last 3 years from the time of this study. Given the 8% seroprevalence in Georgia beef cattle and the reported survey findings from this study, educational programs on ef­fective preventive management practices to control bovine anaplasmosis is warranted.