Bovine anaplasmosis prevalence in northern Veracruz state, Mexico.

In order to learn more about the presence of bovine anaplasmosis in northern Veracruz state, México, paired blood and serum samples from 368 cattle were subjected to polymerase chain reaction (PCR) and complement-fixation test (CFt). The overall prevalence of Anaplasma marginale by PCR was 69.2% and seroprevalence by CFt 54.6%. Age-specific prevalence was calculated for each test. Sixty-eight percent of animals from 0 to 3 months of age already were infected (PCR-positive), compared to only 42.4% positive by serology. CFt results suggested that presence of antibody increases with age up to 18 to 36 months, decreasing thereafter. Presence of the rickettsia seems to follow the same early pattern but with a new increase in animals 36 months or older. Serology results provided a biased picture of the true prevalence of anaplasmosis. Calculated specificity and sensitivity (63.5% and 68.2%) for CFt using PCR values as true values, appear very low and unreliable. The data generated by DNA-based surveys seem more appropriate to help design and implement control or eradication programs for bovine anaplasmosis.