Neospora caninum seroprevalence and associated risk factors in beef cattlein the northwestern United States

A Neospora caninum seroprevalence and risk factor survey of 2585 cows was c onducted in 55 beef cow-calf herds herds located in five northwestern state s of the USA. Blood samples were collected by private veterinary practition ers and management practices were surveyed using a mail questionnaire. Prod ucers were randomly selected from those that employed these veterinarians t o perform annual herd pregnancy examinations. Questions were asked about an imal management, grazing and feeding, immunization and record keeping pract ices. Blood was collected from a systematically selected sample of cows in each herd, and age, origin, and pregnancy status were recorded. Blood sampl es were analyzed for antibodies against N. caninum antigen using a monoclon al antibody-based competitive inhibition (CI) ELISA. Overall seroprevalence was 24% and within herd seroprevalence ranged from 3 to 67% with a median of 19%. Within herd seroprevalence and mean inhibition percentage were diff erent between the five states. Herds that managed their cows on range for s um mer grazing had lower seroprevalence than those that did not, while incr eased seroprevalence was associated with higher winter stocking density. Co ws less than 3 years of age had higher CI ELISA. inhibition percent values than cows greater than 6 years of age. No relationship was noted between se rologic status and individual cow origin (purchased or raised), or pregnanc y status at the time of sampling. (C) 2000 Elsevier Science B.V. All rights reserved.