Fenbendazole in equids: further controlled tests with emphasis on activity of multiple doses against naturally occurring infections of migratory large strongyles.

The research article discusses two experiments conducted to assess the effectiveness of a dosage regimen of fenbendazole (FBZ) paste against infections of migrating Strongylus vulgaris and S edentatus in horses. The results showed successful killing of the parasites in treated animals.

Research Objectives and Design

• The study aimed to evaluate the efficacy of a fenbendazole (FBZ) paste dosage regimen (10 mg/kg, once daily for 5 days) against naturally occurring worm infections in equids, particularly horses.
• Two controlled tests, labeled as experiment D and E, were performed. In both tests, horses were either treated with the FBZ paste or left untreated to serve as controls.
• Eight pony yearlings were used in experiment D and six horse weanlings in experiment E. Experiment D had four treated and four untreated ponies, while experiment E had three treated and three untreated horses.
• The study also collected data on other internal parasites affecting the horses’ gastrointestinal tract and eyes in experiment E.

Data Collection and Analysis

• Intervals between the treatment and necropsy (autopsy of the horses) were 42 or 52 days for experiment D, and 52 or 53 days for experiment E. During this period, the animals were kept on pasture.
• The efficacy of the fenbendazole treatment was inferred from the number of live 4th-stage and 5th-stage S edentatus in both treated and untreated animals. The average number of each stage in the treated and untreated animals was calculated for both experiments.

Key Findings

• The study concluded that the fenbendazole treatment was efficacious in killing retroperitoneal forms of S edentatus in the ventral abdominal wall.
• In both experiments, treated animals had fewer live 4th-stage and 5th-stage S edentatus compared to untreated animals.
• In addition, fragments of dead S edentatus were found in nodules within the treated animals in both experiments, but not in the untreated ones. The consistency of these retroperitoneal lesions also indicated the effectiveness of the fenbendazole treatment.

Conclusion

• The study shows that the dosage regimen of fenbendazole paste is effective in treating infections by S edentatus, a common parasitic worm in horses. This finding could further inform equine veterinary care and worm control strategies.