New research scheduled for publication in an upcoming issue of the journal Veterinary Parasitology, which showed heavy infections of stomach worms in sheep caused those animals to become deficient in protective white blood cells, raises the perpetual question this time of year in cattle health: How are worm infections affecting my vaccine performance?
A study last year in the Journal of Animal Science, led by parasitologists at Colorado State, noted similar studies in cattle have shown parasitic infestation can release a flood of signaling proteins that help jumpstart and communicate the immune system’s response to infection. That stimulation of the system could interfere with the immune response to foreign bodies, including those purposefully introduced through vaccination. Studies from 20 years ago have shown animals with parasitic infections do have altered cell-mediated immune responses to antigens other than those produced by the parasite—such as vaccines—and worm infections can in fact suppress the immune response to vaccine, making them potentially less effective. One very specific study from 2006, for instance, directly showed gastrointestinal worms in lab mice limited the response and effectiveness of a malaria vaccine given the mice.
Because cattle deworming is often delayed until the same run through the chute in which calves are vaccinated, the Colorado State researchers noted, that immune-response scenario begs the question: Is delayed deworming affecting how well calves respond to vaccine components, and eventually to disease challenge?
The Colorado State study gathered 33 Holstein bull calves from a local dairy before they were given any colostrum, which might have confused the experiment by introducing immune-system antibodies. After weaning and feeding to three months old, they were all purposely infected at five separate times with the two most important cattle worms, brown stomachworms and intestinal worms. The calves were then divided into three different treatment groups:
- Dewormed two weeks before being vaccinated with a typical modified-live four-way respiratory vaccine
- Dewormed at the same time they were given the respiratory vaccine
- Vaccinated without being dewormed at all.
On day 53 after vaccination, all calves were purposely infected with a strain of the virus that causes IBR, and then all calves were followed for fever and level of key immune-system response in their blood.
The bottom line: Overall, the study results suggest that deworming at the same time as vaccination, at least in this case, didn’t do any harm. Deworming did reduce worm burdens, as you’d expect, although it didn’t make any difference in animal performance—which, the researchers caution, you shouldn’t read too much into since the animals were individually penned and exposed to worm burdens differently than they would be in the real world. All animals developed circulating antibodies to the BVD, IBR, and PI3 components of the vaccine, regardless of timing of the deworming. The levels of immune bodies that indicate a cellular immune response were also similar, regardless of whether calves were dewormed before or at the same time as vaccination.
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