Molecular and serological in-herd prevalence of Anaplasma marginale infection in Texas cattle

Bovine anaplasmosis is an infectious, non-contagious disease caused by the rickettsial pathogen Anaplasma marginate (Anaplasma marginate). The organism has a global distribution and infects erythrocytes, resulting in anemia, jaundice, fever, abortions and death. Once infected, animals remain carriers for life. The carrier status provides immunity to clinical disease, but is problematic if infected and naive cattle are comingled. Knowledge of infection prevalence and spatial distribution is important in disease management. The objective of this study was to assess Anaplasma marginate infection in-herd prevalence in Texas cattle using both molecular and serological methods. Blood samples from 11 cattle herds within Texas were collected and analyzed by reverse transcription quantitative real-time PCR (RT-qPCR) and a commercial competitive enzyme-linked immunosorbent assay (cELISA). Samples from experimentally infected animals were also analyzed and RT-qPCR detected Anaplasma marginate infection up to 15 days before cELISA, providing empirical data to support the interpretation of herd prevalence results. Herds with high prevalence were located in the north Texas Rolling Plains and west Trans-Pecos Desert, with RT-qPCR prevalence as high as 82% and cELISA prevalence as high as 88%. Overall prevalence was significantly higher in cattle in north and west Texas compared to cattle in east Texas (p < 0.0001 for prevalence based on both RT-qPCR and cELISA). The overall RT-qPCR and cELISA results exhibited 90% agreement (kappa = 0.79) and provide the first Anaplasma marginate infection prevalence study for Texas cattle using two diagnostic methods. Since cattle are the most important reservoir host for Anaplasma marginate and can serve as a source of infection for tick and mechanical transmission, information on infection prevalence is beneficial in the development of prevention and control strategies. (C) 2015 Elsevier B.V. All rights reserved.