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Sub-optimal efficacy of ivermectin against Parascaris equorum in foals on three Thoroughbred stud farms in the Manawatu region of New Zealand.
Abstract: To ascertain whether resistance was present in Parascaris equorum to the macrocyclic lactone anthelmintic ivermectin, using faecal egg count reduction tests. Methods: Thirty-nine foals aged between 11 and 28 weeks on three Thoroughbred stud farms (Farms A; n=20, B; n=5 and C; n=14) were treated with ivermectin (Day 0) and faecal egg counts (FEC) were monitored before and for 21 (Farms A and B) or 14 (Farm C) days after treatment. On Farms A and B, the foals were treated with a macrocyclic lactone/benzimidazole/praziquantel combination on Day 21 and FEC assessed on Day 35. The three farms were all in the Manawatu region in the southern half of New Zealand's North Island. Results: Of the 39 foals, 15 were not shedding P. equorum eggs on the day they were treated with ivermectin, but all 15 did so post-treatment. The FEC on Farms A and B showed no evidence of a reduction at any time between Day 7 and 21; egg output increased steadily over this period. Following combination treatment FEC were reduced by 94% on farm A and 100% on Farm B. On Farm C, there was a 69% reduction in P. equorum FEC on Day 14. Twelve of the 14 foals on Farm C were shedding strongylid eggs on Day 0 and on Day 14 FEC were reduced by 84%. Conclusions: Without comparison to untreated control animals, these results do not allow a reliable estimation of the exact level of efficacy of ivermectin against P. equorum, but they nevertheless show that, within the farms studied, ivermectin no longer achieved a complete kill of egg-laying adults and that foals treated with this drug may continue to shed considerable numbers of eggs after treatment. The results also indicate that ivermectin had sub-optimal efficacy against strongylid nematodes on one of the farms.
Publication Date: 2013-10-24 PubMed ID: 24151853DOI: 10.1080/00480169.2013.843146Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research study investigates the effectiveness of a parasite treatment drug, ivermectin, against a parasitic worm, Parascaris equorum, infesting young horses on three farms in New Zealand. The results imply that ivermectin may not be thoroughly effective in eliminating the worm.
Research Methodology
- The research was conducted on a total of 39 foals (young horses), aged between 11 and 28 weeks, across three Thoroughbred stud farms (Farm A, B, and C) located in the Manawatu region of New Zealand.
- The researchers administered the drug ivermectin to the foals and monitored the faecal egg counts (FEC) for a certain period post-treatment. The FEC was measured pre-treatment and 21 days post-treatment for Farms A and B while for Farm C, it was measured 14 days post-treatment.
- On Farms A and B, the researchers applied an additional treatment on Day 21 comprising a combination of macrocyclic lactone, benzimidazole, and praziquantel drugs.
Results
- All 15 of the 39 foals that were not shedding P. equorum eggs pre-treatment started shedding post-treatment.
- From day 7 to 21, the FEC increased steadily, showing no evidence of reduction on Farms A and B.
- After the combination treatment was administered on Day 21, there was a 94% reduction in FEC on Farm A and a full 100% reduction on Farm B.
- On Farm C, a 69% reduction in P. equorum FEC was observed on Day 14.
- Twelve out of 14 foals on Farm C were initially shedding strongylid eggs, which was reduced by 84% after the treatment.
Conclusion
- The results of the study show that ivermectin may not fully eliminate the shedding of P. equorum eggs in foals, hence its efficiency is questioned.
- Furthermore, the efficacy of ivermectin against strongylid nematodes, another type of worm parasite, was found to be sub-optimal on one of the farms.
- However, as there was a lack of untreated control animals for comparison, the exact level of efficacy of ivermectin remains unclear.
Cite This Article
APA
Bishop RM, Scott I, Gee EK, Rogers CW, Pomroy WE, Mayhew IG.
(2013).
Sub-optimal efficacy of ivermectin against Parascaris equorum in foals on three Thoroughbred stud farms in the Manawatu region of New Zealand.
N Z Vet J, 62(2), 91-95.
https://doi.org/10.1080/00480169.2013.843146 Publication
Researcher Affiliations
- a Institute of Veterinary, Animal and Biomedical Sciences , Massey University , Private Bag 11222, Palmerston North 4442 , New Zealand.
MeSH Terms
- Animals
- Antiparasitic Agents / pharmacology
- Antiparasitic Agents / therapeutic use
- Ascaridida Infections / drug therapy
- Ascaridida Infections / epidemiology
- Ascaridida Infections / veterinary
- Ascaridoidea / drug effects
- Feces / parasitology
- Horse Diseases / drug therapy
- Horse Diseases / epidemiology
- Horses
- Ivermectin / pharmacology
- Ivermectin / therapeutic use
- New Zealand / epidemiology
Citations
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