Researchers Study Factors that Regulate
Vaccination Efficiency By
Rosalie Marion Bliss
August 28, 2009
Using vaccination to induce a robust immune response has been an
effective strategy for managing infectious diseases in humans and animals for
more than a century. Now, Agricultural
Research Service (ARS) scientists and colleagues have found that a
concurrent parasite infection significantly compromises the effectiveness of a
commonly administered vaccine in swine.
The study was conducted by researchers at the ARS
Genomics and Immunology Laboratory in Beltsville, Md., led by
Urban, working with Nina Steenhard of the Institute for Veterinary Disease
Biology at the University of Copenhagen
in Denmark. ARS is the chief intramural scientific research agency of the
U.S. Department of
For the study, 36 pigs raised on a pathogen-free farm were divided
into four groups and studied for nearly three months. The researchers wanted to
compare health indicators among three groups compared with an untreated control
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 against Mycoplasma hyopneumoniae bacteria at week three; and
a worm-free group that was similarly vaccinated against the bacteria at week
All pigs were infected with live M. hyopneumoniae bacteria via
aerosol four weeks after the vaccine injections were administered. Another four
weeks later, the tissue of all pigs were evaluated.
All worm-free, vaccinated pigs infected with M.
hyopneumoniae tested 100 percent positive for vaccine-derived
antibodies, meaning they presented an optimal serum response. But only 78
percent of the vaccinated pigs that had been worm infected developed serum
antibodies. The other 22 percent were considered vaccine failures.
The worm-infected pigs also had a higher percentage of lung pathology
than their non-worm- infected counterparts after vaccination and subsequent
These findings are an indicator of the importance of parasite control
during vaccination. The next step is to conduct further field studies in
environments where animals are susceptible to both worm and bacterial
infection, according to authors.
The study has been accepted for publication in the journal Vaccine.