Variations in seroprevalence and host factors for bovine anaplasmosis in Illinois.

摘要

The modified card agglutination test (MCAT) was used to detect antibodies to Anaplasma marginale in 4994 serum samples from market cattle taken through the Brucellosis Eradication Program in Illinois between 1 April and 31 May 1986. 6.4% of samplesreacted positively to the MCAT. The statewide prevalence estimate was between 7.1% and 10.7% when corrected for sampling distribution and test sensitivity and specificity. Cows were considered to be at decreased risk relative to male cattle in lower-prevalence areas, but the risk was similar in higher-prevalence areas. In both higher- and lower-prevalence areas, the risk of seropositivity increased from 1 year of age onwards, but the rate of increase of risk with age was greater in the higher-prevalenceareas. Calves, however, had higher seroprevalence levels than 1- to 2-year-old animals. The risk was highest for Angus and Angus X Hereford cattle. Dairy cattle showed a decreased risk of seropositivity in the whole sample, but not when the analyses were stratified by prevalence level as there were higher concentrations of dairy cattle in areas with lower prevalence levels.