Efficacy of a Parapoxvirus ovis-based immunomodulator against equine herpesvirus type 1 and Streptococcus equi equi infections in horses.

The research paper presents an investigation into the effectiveness of the Zylexis® immunomodulator, made from an inactivated strain of Parapoxvirus ovis (iPPVO), in treating horses infected with equine herpesvirus type 1 (EHV-1) and Streptococcus equi equi infections.

Study Design and Procedure

• The researchers put together a group of horses to assess the performance of iPPVO. Eleven horses were treated with iPPVO while twelve served as control subjects. Additionally, six other horses were infected with EHV-1 and thereafter mixed with the horses under study.
• The researchers administered doses of iPPVO on Days -2, 0 and 7 of the study, with Day 0 being the day before the EHV-1-infected horses were mixed with the study horses.

Findings and Conclusions

• After administering iPPVO, the researchers observed less nasal discharge, less lymph node enlargement, lesser EHV-1 shedding and lower rectal temperatures in the treated group compared to the control group.
• Similarly, treated horses presented fewer large lymph nodes on Days 17 and 19, lower jaw swelling on Day 3, and lower rectal temperatures on Days 12 and 13 compared to the control group. Symptoms such as difficulty breathing, depression, and anorexia were only recorded in the control group, not in the iPPVO-treated group.
• After the EHV-1 challenge, seven of the eleven iPPVO-treated horses still shed the virus, but the viral quantity shed on Days 11 through 16 was considerably lower compared to the control group.
• All horses got rid of the S. equi bacteria; however, the percentage of horses with positive bacteria detection was lower in the iPPVO-treated group than in the control group from Day 14 to Day 28, with the difference becoming significant on Day 24.
• Administration of Zylexis® produced no injection site reactions or adverse events, thus deemed safe. The treatment also helped reduce the clinical signs and virus shedding related to both EHV-1 and S. equi infections.