Abstract
The changes in nematode cholinesterase (ChE) activities were examined in relation to the development of resistance in (1) a flock of young grazing sheep, (2) grazing and penned sheep treated with dexamethasone and (3) penned sheep receiving a single mixed infection. Nematodes from grazing sheep with high faecal egg counts (FECs) had higher ChE activities than those from sheep with low FECs. Female nematodes tended to have higher ChE activities than males, and ChE activities in both tended to decline with increasing age of the sheep. The decline in female Trichostrongylus colubriformis ChE activity was associated with a decline in both worm length and in utero egg count. No decline in nematode ChE activity was observed when grazing sheep were treated with dexamethasone. ChE activity of T. colubriformis established in immunosuppressed penned sheep declined 10–20 fold 8 weeks after cessation of treatment. Nematode burdens in the small intestine and abomasum of grazing sheep were significantly correlated, and in individual species they were also correlated with ChE activities. The development of resistance in sheep and the elimination of adult nematode burdens is discussed in relation to gastrointestinal mucosal globule leucocyte numbers, mucus antiparasite activity and the impairment of nematode metabolic function.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.