WORM  VACCINE

Researchers have been experimenting with vaccines that prevent worm infection in goats for several years. Dr. Jim Miller, DVM, retired parasitologist (Louisiana State University), has been kind enough to provide information and understanding of this concept.

Dr. Miller worked with Dr. David Smith (Moredun Research Institute, Scotland) testing these "hidden gut" antigens made into vaccine form on goats and sheep. Subsequently, Dr. Smith moved his vaccine program to Australia where he refined the process to produce a vaccine called Barbervax, which is commercially available in Australia, the United Kingdom and South Africa.

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 animals. Because it is so time consuming, it is also very costly. These antigens elicit 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 the goat is reinfected.

Therefore, a hidden gut vaccine needs to be given annually three or four times (3-4 weeks apart) to keep antibody levels high enough to produce any long-term immunity to the worm.

Unfortunately, limited availability of Barbervax and regulatory constraints prevent development and approval in the USA.

Suzanne W. Gasparotto, ONION CREEK RANCH, Briggs, Texas 10.4.26

The author, Suzanne Gasparotto, hereby grants to local goat publications and club newsletters, permission to reprint articles published on the Onion Creek Ranch website under these conditions: THE ARTICLE MUST BE REPRODUCED IN ITS ENTIRETY AND THE AUTHOR'S NAME, ADDRESS, AND CONTACT INFORMATION MUST BE INCLUDED AT THE BEGINNING OF THE REPRINT. We would appreciate notification from any clubs or publications when the articles are used. (A copy of the newsletter or publication would also be a welcome addition to our growing library of goat related information!)

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