Quantification, risk factors, and health impact of natural congenital infection with bovine viral diarrhea virus in dairy calves.
OBJECTIVE
To estimate risk and identify risk factors for congenital infection with bovine viral diarrhea virus (BVDV) not resulting in persistent infection and examine effect of congenital infection on health of dairy calves.


METHODS
466 calves.


METHODS
Calves from 2 intensively managed drylot dairies with different vaccination programs and endemic BVDV infection were sampled before ingesting colostrum and tested with their dams for BVDV and BVDV serum-neutralizing antibodies. Records of treatments and death up to 10 months of age were obtained from calf ranch or dairy personnel. Risk factors for congenital infection, including dam parity and BVDV titer, were examined by use of logistic regression analysis. Effect of congenital infection on morbidity and mortality rates was examined by use of survival analysis methods.


RESULTS
Fetal infection was identified in 10.1% of calves, of which 0.5% had persistent infection and 9.6% had congenital infection. Although dependent on herd, congenital infection was associated with high BVDV type 2 titers in dams at calving and with multiparous dams. Calves with congenital infection had 2-fold higher risk of a severe illness, compared with calves without congenital infection.


CONCLUSIONS
The unexpectedly high proportion of apparently healthy calves found to be congenitally infected provided an estimate of the amount of fetal infection via exposure of dams and thus virus transmission in the herds. Findings indicate that congenital infection with BVDV may have a negative impact on calf health, with subsequent impact on herd health.
Muñoz-Zanzi
Claudia A
CA
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Hietala
Sharon K
SK
Thurmond
Mark C
MC
Johnson
Wesley O
WO
D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000276:immunology / Q000503:physiopathology* / Q000635:transmission*; D002417:Cattle; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology / Q000302:isolation & purification*; D005260:Female; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary*; D008297:Male; D011247:Pregnancy; D016016:Proportional Hazards Models; D012307:Risk Factors
D000914:Antibodies, Viral