title: Effect of congenitally acquired Neospora caninum infection on risk of abortion and subsequent abortions in dairy cattle.
abstract: OBJECTIVE
  To estimate the extent to which abortion risk in dairy cattle during subsequent pregnancies was associated with congenitally-acquired Neospora caninum infection and previous abortions.
  
  
  METHODS
  468 Holstein cattle.
  
  
  METHODS
  Newborn heifer calves were tested for evidence of congenital infection attributable to N caninum and examined repeatedly until the completion of their second lactation for serologic status and evidence of abortion.
  
  
  RESULTS
  Compared with noninfected cows, congenitally infected cows had a 7.4-fold higher risk of abortion during their initial pregnancy and a 1.7-fold higher risk of aborting the first pregnancy during their first lactation. During the first pregnancy of their second lactation, congenitally infected cows that had aborted previously had a 5.6-fold higher risk of abortion, compared with cows that had not previously aborted and that were seronegative. The fetal risk period for N caninum-associated death began sooner and extended later during the initial pregnancy compared with subsequent pregnancies.
  
  
  CONCLUSIONS
  Congenitally acquired N caninum infection can cause a substantial number of abortions during the initial pregnancy of heifers, with abortion risk attributable to N caninum decreasing in subsequent pregnancies, possibly because of selective culling. Subsequent abortions can be expected in congenitally infected cows that have aborted previously.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616-8734, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Thurmond
authors.forename: S K
authors.initials: SK
authors.lastname: Hietala
mesh_terms: D000034:Abortion, Veterinary / Q000453:epidemiology* / Q000209:etiology; D000818:Animals; D002140:California / Q000453:epidemiology; D002417:Cattle; D002418:Cattle Diseases / Q000151:congenital / Q000453:epidemiology* / Q000209:etiology; D003048:Coccidiosis / Q000150:complications / Q000151:congenital / Q000662:veterinary*; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D005260:Female; D008431:Maternal-Fetal Exchange; D018688:Neospora / Q000276:immunology / Q000302:isolation & purification; D011247:Pregnancy; D015597:Pregnancy Complications, Parasitic / Q000453:epidemiology / Q000276:immunology / Q000662:veterinary*; D015995:Prevalence; D012307:Risk Factors