Prevalence of Neospora caninum and persistent infection with bovine viral diarrhea virus in dairy-breed steers in a feedlot.
OBJECTIVE
To determine the prevalence and effect of Neospora caninum infection and persistent infection (PI) with bovine viral diarrhea virus (BVDV) on weight gain, morbidity, and mortality rate in dairy-breed steer calves located on a feedlot in California.


METHODS
Prospective cohort observational study.


METHODS
900 dairy-breed steer calves in 2 pens.


METHODS
The 3- to 4-month-old calves were evaluated for serum antibodies against N caninum and infection with BVDV at entry to the feedlot. Five months later, sera were again analyzed for anti-N caninum antibodies; calves that were determined to have BVDV infection initially were retested to evaluate PI status. Average daily gain, morbidity, and deaths were recorded for all calves.


RESULTS
Among 900 calves, prevalence of N caninum infection was 16.7% (95% confidence interval, 14.3% to 19.3%); prevalence of BVDV-associated PI was 0.2% (95% confidence interval, 0.03% to 0.9%). Morbidity rate and time to first illness were not significantly different between calves that were seropositive or seronegative for N caninum. At the second sample collection, weight and average daily gain of calves that were seropositive for N caninum was less than that of seronegative steers in 1 pen, whereas these measures did not differ between groups in the other pen. Statistical power was insufficient to evaluate the effect of BVDV PI on any outcome measurement.


CONCLUSIONS
Although N caninum serostatus had no significant effect on morbidity rate, some seropositive calves had reduced growth, compared with seronegative calves, 5 months after entry to the feedlot.
Hoar
Bruce R
BR
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
McQuarry
Alana C
AC
Hietala
Sharon K
SK
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D000913:Antibodies, Protozoan / Q000097:blood; D000914:Antibodies, Viral / Q000097:blood; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000453:epidemiology* / Q000401:mortality; D002417:Cattle / Q000254:growth & development*; D002418:Cattle Diseases / Q000453:epidemiology* / Q000401:mortality; D003048:Coccidiosis / Q000453:epidemiology / Q000401:mortality / Q000662:veterinary*; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology; D008297:Male; D018688:Neospora / Q000276:immunology; D016036:Seroepidemiologic Studies; D015430:Weight Gain
D000913:Antibodies, Protozoan; D000914:Antibodies, Viral