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ARS Home » Research » Publications at this Location » Publication #95416
Title: DIAGNOSTIC, IMMUNOLOGIC AND GENETIC ASPECTS OF NEMATODE PARASITISM IN CATTLE

Author
item Gasbarre, Louis

Submitted to: American Association of Veterinary Parasitologists Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/24/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Gastrointestinal (GI) nematode infections remain a source of significant economic loss to American cattle producers. Reasons include: 1) an incomplete understanding of the interactions between the parasites and the host immune system, 2) lack of information concerning the role of host genes in determining resistance/susceptibility, and 3) limited tools for assessing parasite burdens in cattle. Studies indicate most cattle exhibi effective protective immune responses after a relatively brief exposure to the parasites. The exception is Osteragia ostertagi. Ostertagia is an extraordinarily strong stimulator of the immune system, but this stimulation does not result in protection from reinfection. Instead immunity is manifested by a reduction in egg output by the parasites. The weak protective immunity is not a result of the parasite residing in the abomasum, but instead may involve active evasion of the immune response by the parasite. Although most cattle become immune to GI nematodes with sufficient time and exposure, a small percentage remain susceptible to the parasites. A major factor controlling this susceptibility is the genetic makeup of the host. Studies indicate that the use of certain sires in a breeding program can increase the odds of producing susceptible calves by 15-20 fold. Because these susceptible animals produce eggs at high rates, these animals are very importnt for parasite transmission. Studies of the immunogenetics of GI nematode infections show that commonly used methods to measure parasite burdens in cattle are inaccurate in quantifying Ostertagia. This is a result of an inherent lower fecundity of Ostertagia and limiting of egg output by the immune system. Ostertagia infection can be underestimated in cattle w/history of previous exposure to the parasite.