Vaccine for Rhodococcus equi to be Tested in Germany

A vaccine for Rhodococcus equi, the common bacteria that affects foals, often causing severe infections, pneumonia, and sometimes death, is in the final stages of development. Intervet/Schering-Plough Animal Health (ISPAH) said on Jan. 27 that a candidate vaccine for R. equi would be tested in a field trial in Germany in the near future.

The bacteria R. equi is a major problem on U.S. breeding farms, as it causes pneumonia and other infections in foals ages 3 weeks to 5 months. Treatment for affected foals is time consuming and costly, and about 30% of affected foals die as a result of the pneumonia or infections. Researchers are still working to develop control and prevention strategies.

René Aerts, MSc, PhD, vice president of global biologicals research and development at ISPAH, said in a press release that the availability of a safe and effective vaccine against R. equi would have several benefits: "The advantage for the animals would be that they are protected against suffering from a severe and potentially fatal disease. In addition, for horse owners and breeders disease prevention would avoid significant economic losses. Finally, the availability of a safe and efficacious vaccine would lead to a reduction of antibiotics prescription in animals."

"We've all been working towards immunization against Rhodococcus equi pneumonia in foals, since this is the best way to control the infection," said John F. Prescott, MA, VetMB, PhD, professor in the department of pathobiology at the University of Guelph's Ontario Veterinary College. "It has been a challenging problem because of the difficulty of protecting very young foals, by just 2 or 3 weeks of age, against a tough pathogen that lives inside phagocytic cells (a type of white blood cell that engulfs/ingests bacterial invaders) in the lung.

"I understand that the trials have performed very well at the experimental infection level," he added. "However, the final proof will be well-conducted field studies in young foals. We're all keeping our fingers crossed for these studies, hoping they go well."

According to the press release, the field trials will "be executed under strict biosafety measures as required by German and European Union legislation." The first phase of the study will compare the number of R. equi infections in two groups of foals (one treated with the vaccine and one untreated).

A vaccine for R. equi, if successful, would be a welcome addition to the breeding community, Prescott added. "This vaccine would be widely welcomed by horse breeders," he said. "Our current approach using antibiotics is doomed to failure in the long term, because most bacteria become resistant to antibiotics over time."

About the Author

Erica Larson, News Editor

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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