Parasite diversity and anthelmintic resistance in two herds of horses.
Abstract: Diversity of parasite populations was compared between two herds of horses, one a regularly treated herd the other a feral herd which has bad no anthelmintic treatment for at least 25 years. Eggs obtained from fecal samples of both herds were tested for anthelmintic resistance by use of an in-vitro larval hatch/development assay (LDA), DrenchRite. A fecal egg reduction test was also performed with the domesticated herd using fenbendazole, pyrantel pamoate and ivermectin. Cyathostomes were the predominant group of worms present in both herds. Trichostrongylus axei was seen in both herds, but Strongylus equinus, Strongylus vulgaris, Gyalocephalus capitatus, Poteriostomum spp. and Strongyloides westeri were only found in the feral horses. Larvae of Strongylus edentatus were found in a single domesticated horse. Fecal egg reduction tests with the domesticated herd showed a 32% egg count reduction for fenbendazole, a 93% reduction with pyrantel, and a 99% reduction with ivermectin. From the LDA, anthelmintic resistance was evaluated by determining the resistance ratio of the domesticated herd compared with the feral herd. For benzimidazoles in the domesticated herd, 45% of the cyathostome population was 9.4 times more tolerant than the feral herd's parasite population. The parasite population in the domesticated herd was 1.5 times more tolerant to Levamisole, and 1.7 times more tolerant to the benzimidazole/levamisole combination than the parasite population within the feral herd. 9% of the parasite population in the domesticated herd was 90 times more tolerant to avermectins than the feral herd's parasite population, even though a subpopulation of worms in the feral herd were tolerant to low concentrations of avermectins despite never being previously exposed to this class of anthelmintic.
Publication Date: 1999-09-15 PubMed ID: 10485366DOI: 10.1016/s0304-4017(99)00100-4Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study focuses on comparing the diversity of parasite populations and their resistance to deworming drugs in two groups of horses, one domesticated and regularly treated for parasites, and the other a wild herd that has not received any antiparasitic treatment for over 25 years.
Methodology
- Parasite eggs were collected from fecal samples of both domesticated and feral horses.
- The eggs were subjected to an in-vitro larval hatch/development assay (LDA), DrenchRite, to test for resistance to deworming drugs.
- A fecal egg reduction test was also performed on the domesticated horses using three different drugs: fenbendazole, pyrantel pamoate, and ivermectin.
Findings
- Cyathostomes, common parasitic worms, were found in both herds. Trichostrongylus axei were also present in both herds.
- Five types of parasites (Strongylus equinus, Strongylus vulgaris, Gyalocephalus capitatus, Poteriostomum spp. and Strongyloides westeri) were only found in the feral horses.
- Larvae of Strongylus edentatus were found in only one domesticated horse.
Levels of Drug Resistance
- Fecal egg reduction tests demonstrated differing levels of effectiveness for the three drugs tested: fenbendazole showed a 32% egg count reduction, pyrantel showed a 93% reduction, and ivermectin showed a 99% reduction.
- Resistance to the deworming drugs was evaluated by comparing the resistance ratio of the domesticated herd to that of the feral herd.
- In the domesticated herd, 45% of the cyathostome population was 9.4 times more resistant to benzimidazoles than the feral herd’s parasites.
- The domesticated herd’s parasites were 1.5 times more resistant to Levamisole and 1.7 times more resistant to a benzimidazole/levamisole combination than the feral herd’s parasites.
- A small portion (9%) of the parasites from the domesticated herd was 90 times more resistant to avermectins, a class of deworming drugs, compared to those in the feral herd.
- Interestingly, it was observed that some worms from the feral herd showed some level of tolerance to low concentrations of avermectins despite never having been previously exposed to this class of drugs.
Conclusion
- The research indicates that parasites in domesticated herds, which are regularly treated with deworming drugs, have developed a significant level of resistance to these drugs. This resistance is noticeably higher compared to parasites in the feral herd that had not previously been exposed to these drugs.
- The study also provides valuable data on the effectiveness of different deworming drugs, which may help in the effective management of parasitic diseases in horses.
Cite This Article
APA
Young KE, Garza V, Snowden K, Dobson RJ, Powell D, Craig TM.
(1999).
Parasite diversity and anthelmintic resistance in two herds of horses.
Vet Parasitol, 85(2-3), 205-225.
https://doi.org/10.1016/s0304-4017(99)00100-4 Publication
Researcher Affiliations
- Department of Veterinary Pathobiology, Texas A and M University, College Station 77843, USA.
MeSH Terms
- Animals
- Animals, Domestic
- Animals, Wild
- Anthelmintics / pharmacology
- Anthelmintics / therapeutic use
- Drug Resistance
- Feces / parasitology
- Female
- Fenbendazole / therapeutic use
- Horse Diseases / drug therapy
- Horse Diseases / parasitology
- Horses
- Ivermectin / therapeutic use
- Larva
- Ovum
- Pyrantel Pamoate / therapeutic use
- Species Specificity
- Strongylida Infections / drug therapy
- Strongylida Infections / veterinary
- Strongyloidea / classification
- Strongyloidea / drug effects
Citations
This article has been cited 3 times.- Zanet S, Battisti E, Labate F, Oberto F, Ferroglio E. Reduced Efficacy of Fenbendazole and Pyrantel Pamoate Treatments against Intestinal Nematodes of Stud and Performance Horses.. Vet Sci 2021 Mar 5;8(3).
- Jenkins E, Backwell AL, Bellaw J, Colpitts J, Liboiron A, McRuer D, Medill S, Parker S, Shury T, Smith M, Tschritter C, Wagner B, Poissant J, McLoughlin P. Not playing by the rules: Unusual patterns in the epidemiology of parasites in a natural population of feral horses (Equus caballus) on Sable Island, Canada.. Int J Parasitol Parasites Wildl 2020 Apr;11:183-190.
- Alley WS, van Oortmarssen GJ, Boatin BA, Nagelkerke NJ, Plaisier AP, Remme JH, Lazdins J, Borsboom GJ, Habbema JD. Macrofilaricides and onchocerciasis control, mathematical modelling of the prospects for elimination.. BMC Public Health 2001;1:12.
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