An epidemiological study of natural in utero infection with bovine leukemia virus.

The purpose of this study was to examine rates of natural in utero infection with bovine leukemia virus for association with breed, sex, dam age, dam parity and time of maternal seroconversion. Analyses conducted for breed and sex, dam age and parity and time of maternal seroconversion were the FUNCAT procedure for categorical data, Wilcoxon Rank Sums test and Fisher's exact test, respectively. A total of 223 calves born between July 1979, and September 1980, to cows infected with bovine leukemia virus in the University of Florida Dairy Research Unit herd were tested for detectable bovine leukemia virus antibodies prior to the consumption of colostrum. Sera were tested for antibodies by agar-gel immunodiffusion and radioimmunoprecipitation using the glycoprotein-51 antigen. In a group of 125 calves in which in utero infection could be confirmed through serological follow-up (group A), eight calves (6.4%) had precolostral bovine leukemia virus antibodies. For all 223 calves (group B), 18 (8.1%) had detectable bovine leukemia virus antibodies. For calves in group A, no associations were detected between precolostral bovine leukemia virus antibodies and breed (p = 0.66), dam age (p = 0.86), dam parity (p = 0.83), or time of maternal seroconversion to bovine leukemia virus (p = 0.50). However, precolostral bovine leukemia virus antibodies were found in 17.4% of the males and 3.6% of the females in group A (p = 0.11) and in 12.4% of the males and 3.6% of the females in group B (p = 0.04).