Parapoxvirus ovis (iPPVO) and Propionibacterium acnes (P.acnes) are currently used in equine medicine as immune-modulators for prophylactic treatment or adjunct to conventional therapy in order to improve immune defences, to prevent or treat infectious diseases. Their mode of action relies on a non-antigen-specific interaction with the innate and/or adaptive immune responses. iPPVO stimulates and regulates cytokine secretion by a number of leucocytes, while P. acnes acts primarily through activation of macrophages.
The review, conducted by Romain Paillot of the Animal Health Trust, Centre for Preventive Medicine, Newmarket, examined current scientific literature and reports on the use of immune-modulators in horses, particularly for the prevention or treatment of equine respiratory disease.
Stress factors such as weaning, transport and co-mingling predispose horses to infection and increase susceptibility to respiratory pathogens such as Streptococcus zoopidemicus and EHV-1/4. In the past 15 years iPPVO has been tested against several equine infectious respiratory diseases.
The review examined the results of studies on the beneficial use of iPPVO to limit the severity of respiratory infectious diseases in young horses, one of which evaluated the use of iPPVO for protection in yearlings exposed by contact challenge to EHV-1 or EHV-42,3,4. Yearlings treated with iPPVO were co-mingled with horses experimentally infected with EHV-1 and the trial was repeated with horses infected with EHV-4. Horses treated with iPPVO showed a 40% reduction in disease severity in the EHV-1 study and a 61% reduction in the EHV-4 study.
Further studies showed significantly increased frequency of recovery in horses with clinical signs of respiratory disease that had been treated with P. acnes. The decrease in disease severity was also significantly improved in the treated groups5,6.
Romain Palliot concludes: “Non-specific immune-modulators such as iPPVO or P. acnes may not provide protection against direct infection or transmission of respiratory pathogens but they seem to contribute to the reduction of the disease severity, subsequently reducing the frequency of complications and improving the rate of recovery.”
1. Palliot R, 2013. A systematic review of the immune-modulators Parapoxvirus and Propionibacterium acnes for the prevention of respiratory disease and other infections in the horse. Veterinary Immunology and Immunopathology
2. Lindner, A., von Wittke, P., Thein, P., Strube, W., 1993. Effect of a paramunity inducer on the incidence of diseases and the plasma cortisol content in Thoroughbred foals before and after weaning. Tierarztl. Prax. 21, 47-50.
3. Ziebell, K.L., Kretzdorn, D., Auer, S., Failing, K., Schmeer, N., 1997. The use of baypamun N in crowding-associated infectious respiratory disease: efficacy of baypamun N (freeze dried product) in 2-week-old veal calves. Zentralbl Veterinarmed B 44, 415-424.
4. Donecker,JM & Holland Re. Efficacy of the immunomodulator Zylexis in horses challenged with equine herpes virus 2005. Pfizer Zylexis Technical Bulletin V3
5. Evans, D.R. Brent Rollins, J., Huff, G.K., Hartgrove, T.B., Van Kampen, K.R., 1988. Inactivated Propionibacterium acnes (immunoregulin) as adjunct to conventional therapy in the treatment of equine respiratory diseases. Equine Pract. 10, 17-21.
6. Vail, C.D., Nestved, A., Brent Rollins, J., Huff, G.K., Hartgrove, T.B., Evans, D.R., Clapper, J.J., Van Kampen, K.R., Peters, B.A., Hay, C.A., 1990. Adjunct treatment of equne respiratory disease complex (ERDC) with the Propionibacterium acnes, immunostimulant, EqStim. Equine Vet. Sci. 10, 399-403.
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