Vaccinating Goats Against Worms
Researchers have been experimenting with vaccines that prevent worm infection in goats for several years. Dr. Jim Miller, parasitologist at Louisiana State University, has been kind enough to provide
information and understanding of this concept. Dr. Miller worked with Dr. David Smith from 2000-2005 testing these "hidden gut" antigens made into vaccine form on goats and sheep at Louisiana State University.
The antigens (proteins) used in the vaccine are extracted from the hidden gut of Haemonchus contortus, the barberpole stomach worm. To do this, a lot of worms must be obtained, and that requires a large number of goats. Because it is so time consuming, it is also very costly. These antigens cause an immune response where antibodies are produced and circulate in the goat's blood. When the worm sucks the goat's blood, the antibodies attack the gut proteins in the worm, either killing the worm or making it so "uncomfortable" that it is expelled from the goat's body.
Sounds like a great idea, doesn't it? Well, it is -- but here is the drawback. Most vaccines are made with antigens (proteins) that are normally exposed to the goat's immune system during infection. When
the goat is vaccinated for the first time, the immune system is primed to recognize and attack when reinfection occurs. Such a response is called anamnestic because it recognizes and responds to reinfection with a primed immune system. A hidden gut vaccine does not cause an anamnestic response because the antigens are "hidden" in the worm gut and are not normally exposed to
the goat's immune system to induce immunity when goat is reinfected.
Therefore, a hidden gut vaccine has to be given repeatedly (three or four times, about four weeks apart) to keep antibody levels high enough to produce any long-term immunity to the worm. While the concept of a hidden gut worm vaccine sounds good, currently it is too costly to produce for the small population of goats and sheep in the USA.
This article was used with permission from the author, Suzanne W. Gasparotto of Onion Creek Ranch, Texas. This and many other articles on caprine health and wellness, herd management and breeding, etc. can be found at her website tennesseemeatgoats.com. Suzanne can be reached and is usually happy to discuss her thoughts.
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