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ONE SEASON OF PASTURE EXPOSURE FAILS TO INDUCE A PROTECTIVE RESISTANCE TO CYATHOSTOMES BUT INCREASES NUMBERS OF HYPOBIOTIC THIRD-STAGE LARVAE

ONE SEASON OF PASTURE EXPOSURE FAILS TO INDUCE A PROTECTIVE RESISTANCE TO CYATHOSTOMES BUT... The development of acquired resistance to cyathostome challenge after 1 season's exposure to a cyathostome-contaminated pasture was investigated using 17 parasite-naive ponies, which were 2–3 yr of age. These were divided into 3 groups: 1 to graze a cyathostome-contaminated pasture for 4 mo (exposed ponies), 1 to graze a “clean” pasture not previously grazed by parasitized animals (nonexposed ponies), and 1 group to remain in the barn under helminth-free conditions (parasite-free ponies). After pasture exposure all ponies were housed in stalls in the barn and dewormed with ivermectin (200 μg/kg) and oxibendazole (100 mg/kg), a treatment that eliminated most cyathostomes encysted in the mucosa as well as all luminal parasites, on the basis of necropsies of 5 animals, after 17 days. Remaining ponies were challenged with 100,000 cyathostome-infective third-stage larvae (L 3 ) per os 3 wk after anthelmintic treatment. Necropsies were performed 7 wk after the challenge. Total cyathostome burdens (luminal plus encysted stages) were not significantly different among any of the groups. However, a significantly higher percentage of hypobiotic early L 3 (EL 3 ) and a lower percentage of adults were found in exposed ponies. This observation supports the hypothesis that resistance acquired through exposure promotes cyathostome hypobiosis. This increase in EL 3 in exposed ponies was associated with a significant increase in weight of cecum and ventral colon biopsies. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Parasitology Allen Press

ONE SEASON OF PASTURE EXPOSURE FAILS TO INDUCE A PROTECTIVE RESISTANCE TO CYATHOSTOMES BUT INCREASES NUMBERS OF HYPOBIOTIC THIRD-STAGE LARVAE

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Publisher
Allen Press
Copyright
American Society of Parasitologists
Subject
IMMUNOLOGY
ISSN
0022-3395
eISSN
1937-2345
DOI
10.1645/0022-3395%282002%29088%5B0678:OSOPEF%5D2.0.CO%3B2
Publisher site
See Article on Publisher Site

Abstract

The development of acquired resistance to cyathostome challenge after 1 season's exposure to a cyathostome-contaminated pasture was investigated using 17 parasite-naive ponies, which were 2–3 yr of age. These were divided into 3 groups: 1 to graze a cyathostome-contaminated pasture for 4 mo (exposed ponies), 1 to graze a “clean” pasture not previously grazed by parasitized animals (nonexposed ponies), and 1 group to remain in the barn under helminth-free conditions (parasite-free ponies). After pasture exposure all ponies were housed in stalls in the barn and dewormed with ivermectin (200 μg/kg) and oxibendazole (100 mg/kg), a treatment that eliminated most cyathostomes encysted in the mucosa as well as all luminal parasites, on the basis of necropsies of 5 animals, after 17 days. Remaining ponies were challenged with 100,000 cyathostome-infective third-stage larvae (L 3 ) per os 3 wk after anthelmintic treatment. Necropsies were performed 7 wk after the challenge. Total cyathostome burdens (luminal plus encysted stages) were not significantly different among any of the groups. However, a significantly higher percentage of hypobiotic early L 3 (EL 3 ) and a lower percentage of adults were found in exposed ponies. This observation supports the hypothesis that resistance acquired through exposure promotes cyathostome hypobiosis. This increase in EL 3 in exposed ponies was associated with a significant increase in weight of cecum and ventral colon biopsies.

Journal

Journal of ParasitologyAllen Press

Published: Aug 1, 2002

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