Cambendazole for strongyle control in a pony band: selection of a drug-resistant population of small strongyles and teratologic implications.
Abstract: Cambendazole (CBZ) treatments (20 mg/kg) given at 8-week intervals were used for parasite control in a breeding band of ponies (n = 33 to 43) during the period July 1974 to August 1978. Pre- and posttreatment worm egg counts on feces were used to evaluate efficacy of treatments after every 2nd treatment interval by monitoring changes in strongyle egg counts. Initially, effective reductions (expressed as 92% to 96% fewer worm eggs) were lessened to 70% by the 9th treatment (18 months) and to 28% by the 12th treatment, and thereafter, they fluctuated between 0% and 38%. Critical tests on animals culled during the 3rd year revealed that (i) large strongyles (Strongylus vulgaris and S edentatus) were efficaciously removed, (ii) 5 species of small strongyles (Cyathostomum catinatus, Cyathostomum coronatum, Cylicocyclus nassatus, Cylicostephanus longibursatus, and Cylicostephanus minutus) exhibited some degree of resistance, and (iii) 11 species of small strongyles from 6 genera, including the 3 already named, were highly susceptible. Cylicostephanus minutus, in this population exhibited benzimidazole resistance for the first time, whereas Cylicostephanus goldi, previously recognized as resistant in other populations (B and C) in Kentucky, was susceptible to CBZ. A 2-fold increase in the drug-dose rate did not increase efficacy against the CBZ-resistant species of small strongyles, but a 4-fold increase small stronglyles, efficaciously removed 93% of the resistant small strongyles. Foaling rates in the brood band ranged between 38% and 61% for the 5 seasons. Three deformed foals occurred--1 in 1976 and 2 in 1977--among the total of 83 births. Present data did not evidence a probable week of early gestation for possible insult of the fetus by CBZ treatment.
Publication Date: 1983-01-01 PubMed ID: 6824213
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- Journal Article
Summary
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This research article presents a study examining the effectiveness of the drug Cambendazole (CBZ) for controlling strongyles, a type of parasitic worm, in ponies, as well as its potential impact on foal development. Over a four-year period, researchers found that CBZ could initially eliminate 92-96% of worm eggs, but this efficacy decreased over time, with certain species of small strongyles developing resistance.
Research Objectives and Methodology
- The primary objective of the study was to understand the effectiveness of CBZ in controlling strongyles concentration in ponies over a four-year period (1974 to 1978).
- A secondary objective was to explore the potential impacts of CBZ on foal gestation and development.
- CBZ was administered to a group of ponies every eight weeks, with worm egg counts in feces used to measure the effectiveness of the treatment.
Findings on the Effectiveness of Cambendazole
- The treatment was initially very effective, resulting in a reduction of strongyles eggs by 92-96%.
- However, the effectiveness of the drug decreased over time. By the ninth treatment, 18 months into the research, it dropped to 70%. At the 12th treatment, the rate of reduction was only 28%, and it fluctuated between 0% and 38% thereafter.
- When exploring the effectiveness against specific types of strongyles, the researchers found that the drug was successful in eliminating large strongyles species. However, they noticed resistance in five species of small strongyles.
- Interestingly, more drug-dose did not increase efficacy against the CBZ-resistant species of small strongyles, but a 4-fold increase small strongyles was found to remove 93% of the resistant small strongyles.
Implications on Foal Development
- The research team also tracked foaling rates during the study, which fluctuated between 38% and 61%.
- They observed three cases of deformed foals born during the study period; however, they were unable to establish a clear link between these deformations and the CBZ treatment periods.
Summary
- The research reveals that while initial uses of CBZ drastically reduces the strongyle parasite population in ponies, continued usage results in a decrease in the drug’s efficacy due to the development of resistance in certain species of small strongyles.
- Concerning foal gestation and birth, the findings suggest that CBZ usage does not necessarily affect foaling rates, and while deformations were observed, a concrete causative link to CBZ was not established.
Cite This Article
APA
Drudge JH, Lyons ET, Swerczek TW, Tolliver SC.
(1983).
Cambendazole for strongyle control in a pony band: selection of a drug-resistant population of small strongyles and teratologic implications.
Am J Vet Res, 44(1), 110-114.
Publication
Researcher Affiliations
MeSH Terms
- Abnormalities, Drug-Induced / epidemiology
- Abnormalities, Drug-Induced / veterinary
- Animals
- Benzimidazoles / pharmacology
- Cambendazole / adverse effects
- Cambendazole / pharmacology
- Cambendazole / therapeutic use
- Drug Resistance
- Female
- Horse Diseases / chemically induced
- Horse Diseases / epidemiology
- Horses
- Male
- Parasite Egg Count / veterinary
- Reproduction / drug effects
- Species Specificity
- Strongyle Infections, Equine / drug therapy
- Strongyle Infections, Equine / parasitology
- Strongyloidea / drug effects
Citations
This article has been cited 2 times.- Bellaw JL, Nielsen MK. Meta-analysis of cyathostomin species-specific prevalence and relative abundance in domestic horses from 1975-2020: emphasis on geographical region and specimen collection method. Parasit Vectors 2020 Oct 12;13(1):509.
- Lyons E. Population-S benzimidazole- and tetrahydropyrimidine-resistant small strongyles in a pony herd in Kentucky (1977-1999): effects of anthelmintic treatment on the parasites as determined in critical tests. Parasitol Res 2003 Nov;91(5):407-11.
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