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Mechanisms underlying resistance to nematode infection
M J Stear1, S Strain, S C Bishop
1Glasgow University Veterinary School, UK. m.j.stear@vet.gla.ac.uk
International Journal for Parasitology
|February 27, 1999
Summary
Genetic variation in lamb fecal egg count is acquired, not innate. It stems from differences in worm length and fecundity, not worm numbers, influenced by immune responses and worm density.
Area of Science:
- Veterinary Parasitology
- Immunology
- Animal Genetics
Background:
- Faecal egg count (FEC) in lambs infected with Ostertagia circumcinta shows significant variation.
- Understanding the sources of this variation is crucial for parasite control strategies.
Purpose of the Study:
- To investigate the genetic basis of FEC variation in lambs.
- To determine the relationship between FEC, worm burden, worm length, and fecundity.
- To identify factors influencing worm length in lambs.
Main Methods:
- Analysis of natural Ostertagia circumcinta infections in lambs.
- Measurement of faecal egg counts, worm burdens, and worm lengths.
- Assessment of local IgA immune responses against fourth-stage larvae.
Main Results:
- Genetic variation in FEC is acquired, not innate, in lambs.
- Worm length, not worm burden, is the primary driver of FEC variation.
- FEC variation is linked to genetic differences in worm length and fecundity.
- Lambs' immune response (IgA strength and specificity) and worm density influence worm length.
Conclusions:
- FEC variation in lambs is primarily due to acquired differences in worm length and fecundity, modulated by immune factors.
- Mature sheep may possess regulatory mechanisms for worm fecundity and numbers, unlike lambs.
- Targeting immune responses and managing worm density could influence parasite establishment and egg output in lambs.