Experimental transmission of bovine leukosis virus by simulated rectal palpation.

Eight six-month-old Holstein male calves were experimentally inoculated by rectal palpation with whole blood from a donor seropositive to bovine leukosis virus. The inoculation consisted of the deposition of 2 ml of whole blood on a disposable obstetrical sleeve followed by a 30 second rectal palpation to simulate the process of pregnancy detection or artificial insemination. This procedure was repeated at weekly intervals for three consecutive weeks. All eight calves developed antibodies to bovine leukosis virus within five weeks after the initial palpation. The presence of the virus was demonstrated in the peripheral blood leucocytes of all eight calves at nine weeks. These results indicated that routine rectal palpation may be an effective mode of spread of bovine leukosis virus in susceptible cattle.