Prevention of Rhodococcus equi pneumonia of foals using two different inactivated vaccines.

This research focused on preventing Rhodococcus equi pneumonia, a disease that affects foals, by administering two distinct inactivated aluminium salt adsorbed vaccines on three stud farms. Results revealed foals born to immunized mares had significantly improved health outcomes compared to a control group, suggesting vaccination is crucial for preventing cases of R. equi pneumonia.

Research Context

• The study was conducted to assess ways of preventing Rhodococcus equi pneumonia, a disease commonly affecting young foals. Researchers used two distinct kinds of inactivated vaccines for the experiment; the first contained a mixture of R. equi strain and equine herpesvirus 2 (EHV-2), while the second contained only the R. equi strain.
• The investigation was conducted on three different stud farms, providing a diverse set of environments for the research.

Procedure and Methodology

• The methodology involved administering vaccines to both pregnant mares and their foals.
• The mares received two doses of vaccines intramuscularly at six and two weeks before parturition. Their foals were vaccinated on two or three occasions when they reached 3, 5 or 7 weeks old.
• Efficacy of the vaccines was evaluated based on observable clinical signs, serological response (as measured by indirect haemagglutination and virus neutralization tests), and culture of R. equi from sick or dead foals.

Key Findings

• No clinical cases or deaths due to R. equi pneumonia were noted among the foals born to vaccinated mares on two of the three stud farms where the R. equi and EHV-2 mixed vaccine was used. However, among the non-vaccinated control foals, cases of R. equi pneumonia were registered, with some even being fatal.
• On the stud where the vaccine containing only the R. equi strain was applied, all vaccinated foals remained healthy, though there were instances of the disease among the control foals.
• R. equi strains were identified in the lung tissue of all the foals that succumbed to the condition.
• Antibody levels against R. equi and EHV-2 were minimal in the early weeks following vaccination, but began to increase gradually from the fifth week, peaking by the ninth week.

Conclusion

• The conclusion of the research suggests that the use of repeated vaccinations among young foals was more effective in preventing R. equi than vaccination of the mares. The findings indicate that vaccination schedules and methodologies can significantly influence the health outcomes of foals, potentially preventing the occurrence of R. equi pneumonia.