Natural transplacental infection of dairy calves with bovine immunodeficiency virus and estimation of effect on neonatal health.
Many experimental infection studies with bovine immunodeficiency virus (BIV) have been conducted, but neither virus transmission under natural conditions nor longitudinal clinical effects of naturally occurring infections in non-experimental populations are well explored. We tested the hypotheses that BIV is transmitted across the placenta during gestation and that intragestionally infected calves are at increased risk of neonatal disease. A cohort of 59 dairy cows on one farm were enrolled at parturition and the BIV serostatus of the cows and their pre-colostral calves determined with an indirect fluorescent-antibody assay. Moreover, the enrolled calves were monitored thrice weekly for specific clinical signs through the duration of the 30 day neonatal period and the occurrence of clinical signs analyzed for association with calf pre-colostral BIV serostatus and dam BIV serostatus. Confounding due to calf passive immunity and season of birth were also explored. Forty percent of seropositive cows (14/35) gave birth to seropositive calves but no seropositive calves (0/19) were born to seronegative dams (estimated relative risk 16, 95% exact confidence interval 2.6-5.8 x 10(29)). Calf pre-colostral BIV serostatus was not associated with the occurrence or frequency of clinical signs--but dam BIV serostatus was associated with the odds of occurrence of calf hyperthermia and with the frequency of occurrence of calf hyperthermia and hyperventilatory events. This study is inconclusive about the effects of prenatal BIV infection on neonatal health--but it does provide evidence for the natural occurrence of transplacental BIV infection.
Scholl
D T
DT
Department of Epidemiology and Community Health, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803, USA. echdts@lsu.edu
Truax
R E
RE
Baptista
J M
JM
Ingawa
K
K
Orr
K A
KA
O'Reilly
K L
KL
Jenny
B F
BF
D000818:Animals; D000831:Animals, Newborn / Q000276:immunology; D002417:Cattle; D015331:Cohort Studies; D003612:Dairying; D005260:Female; D006304:Health Status; D016087:Immunodeficiency Virus, Bovine; D018445:Infectious Disease Transmission, Vertical / Q000662:veterinary*; D016180:Lentivirus Infections / Q000635:transmission / Q000662:veterinary*; D008431:Maternal-Fetal Exchange; D011247:Pregnancy