“I get a lot of herd health calls from producers asking what to vaccinate for,” says Christine Navarre, Louisiana State University Extension veterinarian. “I won’t even talk about vaccination until we’ve addressed parasite control and nutrition. Without managing those two issues, they may not get all they can out of a vaccination programme.”

Dr Navarre is not alone in her concern. Parasites are listed by the University of California-Davis School of Veterinary Medicine as one of the common causes of vaccine failure.

“Studies have shown that parasite loads can reduce an animal’s ability to produce a strong humoral and cell-mediated immune response to antigens, such as vaccines,”says Frank Hurtig, director, Merial Veterinary Services. “A healthy immune response is necessary for vaccines to be effective. Parasites can hinder that process.”

Some of this reduced immune function may be attributed to parasites causing increased stress and malnutrition.