Vaccination of horses with Lyme vaccines for dogs induces short-lasting antibody responses.

The research paper discusses a study where horses are vaccinated with canine Lyme vaccines to protect against Lyme disease, but it produces only short-lived and often low antibody responses. Multiple trials were conducted to assess antibodies against specific Lyme bacteria proteins, test impact of vaccine dose, analyze the effect of double dosing, and compare different vaccine administration methods.

Experiment on Lyme Vaccines for Horses

• The paper is centered around the lack of approved Lyme vaccines for horses leading veterinarians to use canine vaccines. Because there’s insufficient data on this off-label use, the researchers conducted several trials to understand its efficacy better.
• The researchers analyzed the serum of horses with a history of vaccination with canine Lyme vaccines. They found low and often short-lasting antibody responses, suggesting the vaccines were not producing a strong or long-lasting immunity in horses.

Experimental Vaccine Trials

• In the first trial, antibody responses to three canine vaccines were tested in Lyme bacteria-naïve horses. Only one vaccine induced antibodies against OspC, a protein associated with Lyme disease. However, the response to all three vaccines was low and lasted less than 16 weeks.
• The second trial determined the impact of the vaccine dose using the OspA/OspC inducing bacterin vaccine in horses. A larger dose resulted in greater antibody values; however, the response quickly declined, regardless of dose size.
• The third trial involved horses receiving two doses of a recombinant OspA vaccine. The researchers observed that environmental exposure or previous vaccination enhanced the response duration to 20 weeks, which was still not considerably long.
• In the final trial, they compared the antibody responses prompted by intramuscular and subcutaneous administration of the recombinant OspA vaccine. They found that the method of administration did not influence the immune response significantly.

Conclusions of the Study

• The research concluded that commercial Lyme vaccines intended for dogs only provoke temporary antibody responses in horses, which are often also of low magnitude.
• It warns against the assumption that horses will automatically be protected from B. burgdorferi infection (Lyme disease) by vaccinating them with Lyme vaccines for dogs.