Cases of reduced cyathostomin egg-reappearance period and failure of Parascaris equorum egg count reduction following ivermectin treatment as well as survey on pyrantel efficacy on German horse farms.
Abstract: In 2003 and 2004, on a total of 63 different German horse farms, a survey using the faecal egg count reduction (FECR) test was performed to investigate the efficacy of ivermectin (IVM, Ivomec) and pyrantel (PYR, Banminth) treatment against gastro-intestinal nematodes in a total of 767 horses. IVM treatment resulted in 100% reduction of the cyathostomin egg production 14 and 21 days post-treatment (d.p.t.) on 37 farms. On the remaining five farms, the mean faecal egg count reduction ranged between 97.7 and 99.9%. The mean cyathostomin FECR following PYR treatment ranged between 92.2 and 100% on the 25 farms tested. Therefore, based on the 90% FECR threshold suggested for detection of anthelmintic resistance in horses, neither IVM nor PYR anthelmintic resistance was detected. However, if the thresholds recommended for the detection of resistance in small ruminants were applied, on one and four farms signs of reduced IVM and PYR efficacy, respectively, were observed. In 2005, to further investigate these findings, the cyathostomin egg-reappearance period (ERP) following IVM treatment was examined on six selected farms, two of which were found to show less than 99.8% FECR in the previous survey. On these two latter farms, the ERP was less than 5 weeks, while on the other four it was at least 8 weeks. Earlier investigations described IVM cyathostomin ERP of at least 9 weeks. The efficacy of IVM to reduce Parascaris equorum egg excretion was also studied. On one farm in 2 consecutive years, IVM treatment did not lead to a significant reduction in P. equorum faecal egg counts in one and five young horses, respectively.
Publication Date: 2006-11-16 PubMed ID: 17112667DOI: 10.1016/j.vetpar.2006.09.036Google Scholar: Lookup
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Summary
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The study investigated the effectiveness of ivermectin (IVM) and pyrantel (PYR) in treating gastrointestinal nematodes in horses on 63 German farms. The research found that in some cases, the period for cyathostomin egg re-emergence after IVM treatment was less than previously reported and in some instances, IVM treatment didn’t significantly reduce Parascaris equorum egg counts.
Research Methods and Findings
- The researchers conducted a survey in 2003 and 2004 using the faecal egg count reduction (FECR) test on different German horse farms to determine the efficacy of ivermectin (IVM) and pyrantel (PYR) treatments against gastro-intestinal nematodes in horses.
- The FECR test measures the number of eggs in the droppings before and after treatment to determine and quantify the effect of the drug.
- IVM treatment resulted in 100% reduction of the cyathostomin egg production 14 and 21 days post-treatment on 37 farms. On the remaining five farms, the average faecal egg count reduction ranged between 97.7% and 99.9%.
- The mean cyathostomin FECR following PYR treatment ranged between 92.2% and 100% on the 25 farms tested.
- Based on the 90% FECR threshold suggested for detecting anthelmintic resistence in horses, neither IVM or PYR anthelmintic resistance was detected.
Noteworthy Exceptions Detected
- However, applying the thresholds recommended for detecting resistance in small ruminants, signs of reduced IVM and PYR efficacy were observed on one and four farms respectively.
- To confirm these findings, cyathostomin egg-reappearance period (ERP) following IVM treatment was examined on six selected farms. On two farms where less than 99.8% FECR was previously observed, the ERP was less than 5 weeks, which is shorter than previous reports of at least 9 weeks.
- Moreover, on one farm, IVM treatment didn’t significantly decrease Parascaris equorum faecal egg counts in young horses over two consecutive years.
Implications of the Findings
- The reduced IVM efficacy suggest possible anthelmintic resistance, which can adversely affect treatment outcomes and horse health.
- The observed reduced ERP implies accelerated re-infestation following treatment, potentially undermining the long-term efficacy of IVM treatments for cyathostomin.
- The ineffective IVM treatment for P. equorum eggs shed highlights potential treatment failure for this parasite.
Cite This Article
APA
von Samson-Himmelstjerna G, Fritzen B, Demeler J, Schürmann S, Rohn K, Schnieder T, Epe C.
(2006).
Cases of reduced cyathostomin egg-reappearance period and failure of Parascaris equorum egg count reduction following ivermectin treatment as well as survey on pyrantel efficacy on German horse farms.
Vet Parasitol, 144(1-2), 74-80.
https://doi.org/10.1016/j.vetpar.2006.09.036 Publication
Researcher Affiliations
- Institute for Parasitology, University of Veterinary Medicine, Buenteweg 17, 30559 Hannover, Germany. gvsamson@tiho-hannover.de
MeSH Terms
- Animals
- Antiparasitic Agents / pharmacology
- Ascaridida Infections / drug therapy
- Ascaridida Infections / veterinary
- Ascaridoidea / drug effects
- Ascaridoidea / growth & development
- Drug Resistance
- Female
- Germany
- Horse Diseases / drug therapy
- Horses
- Ivermectin / pharmacology
- Male
- Parasite Egg Count / veterinary
- Pyrantel / pharmacology
- Strongyle Infections, Equine / drug therapy
- Strongyloidea / drug effects
- Strongyloidea / growth & development
- Time Factors
- Treatment Outcome
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