Risk of abortion associated with Neospora caninum during different lactations and evidence of congenital transmission in dairy cows.
OBJECTIVE
To examine the relationship between exposure to Neospora caninum and abortion in dairy cows during their first, second, third, and fourth or later lactations and to establish the main mode of transmission in female calves from birth until their first pregnancy was terminated by abortion or parturition.


METHODS
Prospective observational study.


METHODS
460 Holstein cows and 79 female calves.


METHODS
Cows were classified as seropositive or seronegative to N caninum within 7 days after calving; incidence of abortion was compared between groups during different lactations. Blood samples were collected from female calves before ingestion of colostrum and every 6 months until their first pregnancy was terminated by abortion or parturition; number of seropositive calves was compared between seropositive and seronegative dams.


RESULTS
During the first pregnancy of their second lactation, risk of abortion for seropositive cows was 2.8 times that of seronegative cows. Among 10 calves born to seropositive cows, 4 were classified as seropositive at birth and thereafter. Among 69 calves born to seronegative cows, all were classified as seronegative at birth; 67 calves remained seronegative thereafter.


CONCLUSIONS
Exposure to N caninum alone was not significantly associated with abortion in cows during the first, third, and fourth or later lactations. Seropositive cows that have aborted previously may have subsequent abortions attributable to N caninum. Congenital infection was the main mode of N caninum transmission in a cohort of female calves.
Hernandez
Jorge
J
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0136, USA.
Risco
Carlos
C
Donovan
Arthur
A
D000034:Abortion, Veterinary / Q000453:epidemiology / Q000469:parasitology*; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000469:parasitology* / Q000635:transmission; D003048:Coccidiosis / Q000150:complications / Q000453:epidemiology / Q000635:transmission / Q000662:veterinary*; D015331:Cohort Studies; D005260:Female; D005431:Florida / Q000453:epidemiology; D015994:Incidence; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary*; D007774:Lactation; D008431:Maternal-Fetal Exchange; D018688:Neospora / Q000276:immunology*; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000662:veterinary*; D011446:Prospective Studies; D012307:Risk Factors; D016036:Seroepidemiologic Studies
D000913:Antibodies, Protozoan