Factors associated with seroprevalence of bovine anaplasmosis in Texas.

Bovine anaplasmosis (BA), caused by Anaplasma marginale, is an economically important tick-borne disease of cattle in the United States (U.S.) and worldwide. Anecdotally, Veterinary Feed Directive prescriptions in the southeastern U.S. are written mostly for treatment/prevention of BA. However, there are no recent temporal seroprevalence estimates of BA in Texas (TX). Thus, this study was aimed at determining the seroprevalence of and factors associated with BA in TX. Data were obtained from an active slaughter survey (n = 215) performed between August and December 2014 as well as from reviewing Texas A&M Veterinary Medical Diagnostic Laboratories (TVMDLs) records of specimens submitted for BA testing from January 2002 to June 2012 (n = 15,460). Irrespective of the assay used, the overall apparent seroprevalence of BA in TX between 2002 and 2012 was 15.91% (95% CI: 15.34 - 16.50%) and the yearly increase in seroprevalence followed a significant trend (P < .0001). With cELISA, the apparent seroprevalence of BA was 13.49% (95% CI: 9.56 - 18.7%) and 13.02% (95% CI: 9.74 - 17.18%) for the slaughter survey and TVMDLs records between October and December 2011, respectively. Whereas the estimated true seroprevalence for the same period was 12.35% (95% CI: 8.04 - 18.05%) and 12.78% (95% CI: 9.19 - 17.30%), respectively. Factors associated with positive BA results were age, breed, diagnostic assay used, year and quarter of the year the specimens were submitted. The odds of the outcome were 1.5 times as high when cattle were adults (vs juvenile). In comparison to other breeds, the odds of the outcome were 11.57, 7.16, and 2.5 times higher in Hereford, Angus, and mixed breeds, respectively. When compared to 2003, the odds of the diagnosis of BA was approximately 2 times as high in 2010 but 3 times as high in 2002, 2005, and 2011 and approximately 4 times as high in 2006 and 2007. In comparison to the duration from October to December, the odds of the outcome were approximately 1.5 as high from January to March and from July to September durations. Counties with specimen submissions for BA testing had a significantly greater cattle population (p = .0061) and number of cattle farms (p < .001) than counties without specimen submissions. Subsequent prevention and control measures for BA should target these factors and should prioritize on counties with higher cattle population in the eastern part of TX. Furthermore, TVMDLs records appear sufficient for the surveillance of BA in TX.

Factors associated with Seroprevalence of Anaplasma marginale in Kentucky cattle.

Bovine anaplasmosis (BA) is tick-borne disease of cattle caused by Anaplasma marginale and it remains an economically important disease in the United States (U.S.). We have anecdotal information that Veterinary Feed Directive prescriptions in Kentucky (KY) are written most often for treatment and prevention of BA. However, there are no recent prevalence estimates of this disease in KY. Thus, this study was aimed at determining the seroprevalence of and factors associated with BA in KY. Data were obtained from an active slaughter survey (n = 232) performed between May and July 2013 as well as from reviewing The University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) records of specimens submitted for BA testing from 2002-2012 (n = 2,573). With competitive ELISA, the apparent prevalence of BA in KY was 10.78% (95% CI: 7.41-15.42%) and 11.58% (95% CI: 10.31-12.98%) for the slaughter survey and laboratory records, respectively. Whereas the estimated true prevalence was 9.44% (95% CI: 5.65-14.48%) and 10.3% (95% CI: 8.92-11.8%), respectively. From the laboratory records, factors associated with positive BA results were age, breed, whether specimens were submitted singularly or as a group, year and quarter of the year the specimens were submitted. The odds of the outcome were 5 times as high when cattle were adults (vs juvenile) and almost 4 times as high when specimens were submitted singularly (vs group). In comparison to Holstein breed, the odds of the outcome were 3.5 and 2.5 times higher in Angus and mixed breeds, respectively. The odds of a diagnosis of BA varied in an undulating pattern by year of sample submission. When compared to 2011, the odds of a diagnosis of BA was approximately 3 times as high in 2005, 2008, and 2009 and approximately 5 times as high in 2004, 2006, and 2012. In comparison to the duration from January to March, the odds of the outcome were almost 20 times as high from July to September but 10 times as high from October to December durations. Counties with specimen submissions for BA testing had a significantly greater cattle population and number of cattle farms than counties without specimen submissions. Future prevention and control measures for BA should target these factors and should be weighted more on counties with higher cattle population. Furthermore, current records from the UKVDL appear sufficient for the surveillance of BA in KY.