Anti-Gnrh Vaccination Of Stallions Shedding Equine Arteritis Virus In Their Semen: A Field Study

Stallions are natural reservoirs of equine arteritis virus (EAV) in their semen, representing a potential source of outbreaks. The carrier-state is testosterone-dependent, and clears spontaneously in 4 to 40% stallions. Reduction of testosterone secretion may be obtained with the anti-GnRH vaccine Equity. In this report. 16 naturally infected stallions excreting EAV in their semen were vaccinated twice with the vaccine Equity (TM) and monitored irregularly under field conditions for EAV viral load in their semen and plasmatic testosterone concentration. The results are indicated in months (M) after the first vaccine injection. Testosterone concentrations decreased from 1.7 to 0.2 ng/mL (P<0.002) after 3M. The EAV viral load decreased from 3.2 x10(9) to 1.1 x10(6) RNA copy/mL of semen (P<0.001) after 5M. One stallion died at 7M for other reason. At M3-10, 12/15 stallions ceased to shed the virus in their semen. At M510, 9/15 stallions had plasmatic testosterone concentrations of >= 0.5 ng/mL but the 6 others showed a persistently low testosterone concentration (<= 0.3 ng/mL). Of the 14 stallions that were expected to recover their reproductive activity at the time of the next breeding season (More