Objective—To determine the impact of antimicrobial-containing semen extender on the growth of Taylorella equigenitalis in semen culture-positive for contagious equine metritis (CEM) and the development of CEM after artificial insemination with CEM-positive semen extended with antimicrobial-containing semen extender.
Animals—21 mature mares free of CEM, 1 mature stallion experimentally infected with CEM, and semen from a stallion naturally infected with CEM.
Procedures—CEM-positive semen was incubated in semen extender with and without antimicrobials (amikacin [final concentration, 1 g/L] and penicillin G potassium [0.63 g/L]) followed by determination of the number of colony-forming units of T equigenitalis. Mares were inseminated with raw, extended, or cryopreserved semen culture-positive for T equigenitalis and observed for clinical signs of CEM. Samples for bacterial culture were obtained from the uterus, clitoral sinuses, and clitoral fossa of mares 7, 14, and 21 days after artificial insemination.
Results—Antimicrobial-containing semen extender significantly reduced the number of colony-forming units of T equigenitalis in CEM-positive semen. Artificial insemination with raw CEM-positive semen resulted in clinical signs of CEM, whereas artificial insemination with extended or cryopreserved CEM-positive semen did not result in clinical signs of CEM.
Conclusions and Clinical Relevance—Antimicrobial-containing semen extender significantly reduced the risk of dissemination of CEM. The inclusion of amikacin (1 g/L) and penicillin G potassium (0.63 g/L) in extended semen reduced the transmission of CEM from stallions to mares during artificial insemination, which may result in altered dissemination of the disease.
Objective—To compare growth characteristics of
strains of equine arteritis virus (EAV) of differing virulence
to horses in rabbit kidney (RK)-13 cells and
equine endothelial cells (EECs) cultured from the pulmonary
artery of a foal.
Sample Population—13 strains of EAV, including 11
field isolates of differing virulence to horses; the highly
virulent, horse-adapted Bucyrus strain; and the
modified-live virus (MLV) vaccine derived from it.
Procedure—The growth characteristics of the 13
strains were compared in EECs and RK-13 cells. Viral
nucleoprotein expression, cytopathogenicity, and
plaque size were compared to determine whether
growth characteristics of the 13 strains were predictive
of their virulence to horses.
Results—Cytopathogenicity, viral nucleoprotein
expression, and plaque size induced by all 13 viruses
were similar in RK-13 cells, whereas virulent strains of
EAV caused significantly larger plaques in EECs than
did the avirulent strains of EAV. Paradoxically, the
highly attenuated MLV vaccine and 1 field isolate of
EAV caused plaques in EECs that were larger than
those caused by any of the other viruses, and
sequence analysis confirmed the field isolate of EAV
to be indistinguishable from the MLV vaccine.
Conclusions and Clinical Relevance—With the
notable exception of the MLV vaccine, growth of the
various strains of EAV in EECs was predictive of their
individual virulence to horses. Thus, EECs provide a
relevant and useful model to further characterize
determinants of virulence and attenuation amongst
strains of EAV. (Am J Vet Res 2003;64:779–784)
Objective—To determine whether it is safe to vaccinate pregnant or postpartum mares with a commercial modified-live virus vaccine against equine viral arteritis (EVA).
Design—Randomized controlled study.
Animals—73 mares and their foals.
Procedures—Mares were vaccinated during mid gestation, during late gestation, or 2 or 3 days after parturition with a commercial modified-live virus vaccine or were not vaccinated. Foaling outcomes were recorded, and serum, blood, milk, and nasopharyngeal samples were obtained.
Results—All mares vaccinated during mid gestation foaled without any problems; 21 of 22 mares in this group had antibody titers against EAV at the time of foaling. Of the 19 mares vaccinated during late gestation, 3 aborted; antibody titers against EAV were detected in 13 of 15 mares from which serum was obtained at the time of foaling. All postparturient vaccinates were seronegative at foaling; all of them seroconverted after vaccination. No adverse effects were detected in any of their foals.
Conclusions and Clinical Relevance—When faced with a substantial risk of natural exposure to EAV, it would appear to be safe to vaccinate healthy pregnant mares up to 3 months before foaling and during the immediate postpartum period. Vaccinating mares during the last 2 months of gestation was associated with a risk of abortion; this risk must be weighed against the much greater risk of widespread abortions in unprotected populations of pregnant mares naturally infected with EAV.