Venereal infection of mares by equine arteritis virus and use of killed vaccine against the infection.

The researchers studied the venereal infection of horses by the Equine Arteritis Virus (EAV), and the impact of a killed vaccine designed to combat this infection and observed its clinical implications among the infected mares.

Introduction and Methodology

• The study focused on understanding the venereal infection caused by Equine Arteritis Virus (EAV) amongst mares. Seven mares were artificially infected with EAV by inoculating them with greater than 8 million plaque-forming units (PFU) of viral suspension through their cervix after treatment with prostaglandin and oestradiol.
• The researchers used a lesser dose of less or equal to 800,000 PFU (Plaque Forming Units) to infect another group of eight mares as a control.
• As a part of a vaccination test, four mares were immunized with a killed vaccine for Equine Viral Arteritis (EVA)

Observations and Findings

• Infection was confirmed in all seven mares with higher dose inoculation, whereas only five out of eight mares were found infected when given the lesser dose.
• All the mares showing clinical signs developed Serum neutralizing antibodies, which are immune system proteins that neutralize the pathogen’s effect. There was indication of weak antibody detection in one seemingly healthy mare that was inoculated with 800,000 PFU.
• The presence of EAV was evident not only in the buffy coat (layer of white blood cells and platelets) but also within the nasal swabs of the infected mares.
• The isolation of the virus was frequently discovered in the body tissues of the mares up until day 12 post-inoculation, but rarely after day 12 within reproductive tissues.
• The virus was detected for the longest duration in the splenic and deep inguinal lymph nodes, followed by the spleen and internal iliac lymph nodes.

Impact of the Killed Vaccine

• The four mares that were immunized with the killed EVA vaccine showed no clinical signs of disease after being later infected with EAV.
• Virus presence was observed from the buffy coats of three of these vaccinated mares and within the nasal swab of one of them, but the virus was not found in the rest.

This study indicates that venereal infection with EAV in mares can be effectively prevented using the killed EVA vaccine, while further suggesting that the virus mainly persists in the splenic and lymph node regions until 12 days post-inoculation.