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

item HAIRGROVE, THOMAS - Texas A&M University
item SCHROEDER, MEGAN - Texas A&M University
item BUDKE, CHRISTINE - Texas A&M University
item RODGERS, SANDY - Texas A&M University
item CHUNG, CHUNGWON - Texas A&M University
item Ueti, Massaro
item BOUNPHENG, MANGKEY - Texas A&M University

Submitted to: Preventive Veterinary Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2015
Publication Date: 2/16/2015
Citation: Hairgrove, T., Schroeder, M.E., Budke, C.M., Rodgers, S., Chung, C., Ueti, M.W., Bounpheng, M.A. 2015. Molecular and serological in-herd prevalence of Anaplasma marginale infection in Texas cattle. Preventive Veterinary Medicine. doi: 10.1016/j.prevetmed.2015.02.006.

Interpretive Summary: Bovine anaplasmosis is a tick transmitted disease caused by the bacterium Anaplasma marginale. Once cattle recover from the initial infection, they remain infected for life. Knowledge of infection prevalence and geographic distribution is important in disease control. The objective of this study was to assess A. marginale prevalence in Texas cattle herds. Since cattle can serve as a source of transmission, information regarding infection prevalence is beneficial for the development of control strategies to prevent A. marginale transmission.

Technical Abstract: Bovine anaplasmosis is an infectious, non-contagious disease caused by the rickettsial pathogen Anaplasma marginale (A. marginale). 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 naïve cattle are comingled. Knowledge of infection prevalence and spatial distribution is important in disease management. The objective of this study was to assess A. marginale 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 A. marginale infection up to 15 days before cELISA, providing empirical data to support the interpretation of herd prevalence results. Herds with the 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 A. marginale infection prevalence study for Texas cattle using two diagnostic methods. Since cattle are the most important reservoir host for A. marginale 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.