Agricultural Research Service (ARS) scientists have discovered that a common swine vaccine used to fight disease is significantly compromised when a concurrent parasite infection is present.

The discovery was made by researchers at the ARS Diet, Genomics and Immunology Laboratory in Beltsville, MD. ARS microbiologist Joseph Urban collaborated with Nina Steenhard of the Institute for Veterinary Disease Biology at the University of Copenhagen in Denmark.

In the study, 36 pigs raised on a pathogen-free farm were split into four groups and studied for about three months, to compare three treated groups with an untreated group.

The three groups included pigs that had been continuously exposed to a common worm infection; pigs that were exposed to the same worm infection but vaccinated for Mycoplasmal pneumonia at Week three; and a worm-free group that was similarly vaccinated against mycoplasma at Week three.

All pigs were infected with live mycoplasma bacteria via aerosol four weeks after vaccine was administered. Another four weeks later, the tissues of all pigs were evaluated.

All worm-free, vaccinated pigs infected with mycoplasma developed vaccine-derived antibodies. But only 78% of the vaccinated pigs that had been worm infected developed serum antibodies. The other 22% were considered vaccine failures.

The worm-infected pigs also had a higher percentage of lung infections than non-worm-infected pigs after vaccination and exposure to mycoplasma bacteria.

Researchers conclude the findings confirm the importance of parasite control during vaccination.