Date of Award:

1992

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Animal, Dairy, and Veterinary Sciences

Advisor/Chair:

M. Keven Jackson

Abstract

A diagnostic test for bovine leukosis was developed using the polymerase chain reaction (PCR) to amplify a 375 base pair region in the gag gene of the proviral genome.

Blood samples were collected from 3 adult Holstein cows shown to be infected with bovine leukosis virus (BLV) by the agar-gel immunodiffusion (AGID) technique. The 3 samples were mixed and the composite blood was used to inoculate 10 cows. Five of the cows were inoculated with 0.1 ml of blood, and the other cows were inoculated with 1 ml of blood. Five of the cows were negative for BLV by AGID and PCR on the day of inoculation, and the other five cows were positive for BLV on the day of inoculation.

The 10 cows were bled on day 1 (day 0 being the day of inoculation) and day 7 post-inoculation, and every 2 weeks subsequently until 3 months post-inoculation. Samples were stored until the end of the study, at which time the AGID and PCR tests were performed.

Three cows became AGID-positive 3 weeks post-inoculation, and two cows seroconverted 5 weeks post-inoculation. The time of seroconversion did not correlate with the volume of viral inoculum. In comparison, the PCR consistently detected infection sooner than the AGID: by day 7 post-inoculation all 5 cows were BLV-positive as determined with the PCR test, and remained positive until the end of the study.

The results indicate that under the experimental conditions, bovine leukemia virus infection in cattle can be detected as much as 2 to 4 weeks earlier by PCR than by AGID.

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