01-03-1994
Article by:
Sabrina L. Swenson, DVM, PhD; Howard T. Hill, DVM, PhD; Jeff J. Zimmerman, DVM, PhD; Lawrence E. Evans, DVM, PhD Robert W. Wills, MS, DVM; Kyoung-Jin Yoon, DVM, MS; Kent J.
Six gilts were artificially inseminated (Al) with extended semen from a boar free of porcine reproductive and respiratory syndrome (PRRS) virus infection. One week later, the same boar was inoculated intranasally with PRRS virus. Seven days after inoculation, the boar was used to Al an additional five gilts. All 11 gilts were bred 3 days in a row using freshly collected and extended semen on each of the 3 days. Gilts were bled on a weekly basis until they were euthanized. Serum samples were tested for the presence of PRRS virus antibodies by the indirect-fluorescent antibody (IFA) test and for the presence of PRRS virus using virus isolation on porcine alveolar macrophages. Due to the cytotoxic nature of semen for continuous cell lines, a swine bioassay was used to confirm the presence of PRRS virus in the semen. The boar was euthanized on day 21 postchallenge. The control gilts were euthanized on day 40 and the gilts exposed to PRRS virus-contaminated semen were euthanized on day 34 following the first insemination. Reproductive tract tissues were collected for virus isolation and histopathologic examination.
No clinical signs of PRRS were noted in the 11 gilts. The boar was depressed and anorexic for several days following challenge, but was physically normal by the time of collection 7 days postchallenge. Sperm motility and morphology were within normal acceptable limits for Al. Virus was detected in undiluted aliquots of semen collected on days 7 and 8 post-challenge, but not in the four samples collected prior to challenge or in the semen collected on days 9, 14, or 21 post-challenge. At the time of euthanasia, four of six control gilts were pregnant and one of five gilts inseminated with PRRS virus-contaminated semen was pregnant. None of the gilts seroconverted on the IFA test and virus was not isolated from the serum or reproductive tracts. Virus was not isolated from the reproductive tract of the boar. No histopathologic lesions were noted in the reproductive tracts of the gilts or boar.
There was no significant difference in the pregnancy rates between the control and virus-exposed gilts. Transmission of PRRS virus through virus-contaminated semen was not detected based on development of PRRS virus antibodies, virus isolation from serum, or virus isolation from reproductive tracts.
