Verification of ineffectual activity of ivermectin against adult Onchocerca spp in the ligamentum nuchae of horses.
Abstract: Ivermectin paste formulation (200 micrograms/kg) was administered orally to 27 horses (13 Thoroughbreds and 14 of mixed breeding) to evaluate activity against adult Onchocerca spp in the ligamentum nuchae. Ages, known or estimated, of the horses ranged from 1 to 22 years. Single or multiple doses (1 to 5) of the drug were given to each horse. When multiple doses were administered, the intervals between treatments ranged from 7 to 92 days. At 27 to 171 days after initial treatment (single dose or first of multiple doses), the horses were killed. Some of the horses treated more than once were killed as soon as 7 days after the last treatment. At necropsy, Onchocerca spp were found in the ligamentum nuchae of 24 (89%) of the 27 horses. All of the specimens were pieces of worms, apparently adult, which appeared to be alive. The only noninfected horses were 2 to 3 years old. In 18 (75%) of the 24 infected horses, microfilariae, most being obviously viable, were found in the worm specimens or ligamentum nuchae.
Publication Date: 1988-07-01 PubMed ID: 3421544
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- Journal Article
Summary
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This research study tested the effectiveness of Ivermectin, a commonly used drug, against adult Onchocerca species which is a parasitic worm in horses, revealing that the treatment was ineffective.
Research Methodology
- The research was conducted on a total of 27 horses, 13 of which were Thoroughbreds and 14 were of mixed breeding.
- The horses ranged in age from 1 year to 22 years, with some ages being estimated.
- The treatment involved administering the horses with a specific formulation of Ivermectin, orally at a dosage strength of 200 micrograms per kilogram.
- Each horse was given single or up to 5 doses of the drug, with the intervals between multiple treatments ranging between 7 to 92 days.
- The horses were killed anywhere between 27 to 171 days after the initial treatment. Some horses treated with multiple doses were killed as soon as 7 days after their last dose.
Research Findings
- The necropsy results showed that 24 out of the 27 horses (89%) had Onchocerca species in the ligamentum nuchae, which is a ligament in the neck of the horse.
- All of the specimens collected were pieces of worms thought to be adults and were still alive, indicating that Ivermectin didn’t kill the worms.
- The only horses not to be infected were found to be between 2 to 3 years old.
- Moreover, in 18 of these infected horses (75%), microfilariae (the larval stage of the parasite) that seemed viable were found either in the worm specimens or the ligamentum nuchae, indicating that the Ivermectin had also been unsuccessful in killing the larvae within the hosts.
Implications of the Research
- This study provides critical insights on the ineffectual activity of Ivermectin. It illuminates the need for further research to find a more effective treatment to eradicate adult Onchocerca species and its larvae in horses.
- These findings are substantial because Onchocerca species is hazardous and may lead to serious health issues in horses if not eradicated, including various skin diseases and possibly blindness.
Cite This Article
APA
Lyons ET, Drudge JH, Tolliver SC.
(1988).
Verification of ineffectual activity of ivermectin against adult Onchocerca spp in the ligamentum nuchae of horses.
Am J Vet Res, 49(7), 983-985.
Publication
Researcher Affiliations
- Department of Veterinary Science, College of Agriculture, University of Kentucky, Lexington 40546-0099.
MeSH Terms
- Animals
- Female
- Horse Diseases / drug therapy
- Horses / parasitology
- Ivermectin / therapeutic use
- Ligaments / parasitology
- Male
- Onchocerca / drug effects
- Onchocerciasis / drug therapy
- Onchocerciasis / veterinary
Citations
This article has been cited 3 times.- Brown KA, Johnson AL, Bender SJ, Nolan TJ, Pfisterer B, Slack J, Willis E, Rule EK. Onchocerca sp. in an imported Zangersheide gelding causing suspensory ligament desmitis. J Vet Intern Med 2023 Mar;37(2):735-739.
- Heneberg P, Casero M. Recent large-scale philophthalmosis outbreak in Portugal: inefficacy of common antihelminthic agents. Parasit Vectors 2022 May 12;15(1):167.
- Duke BO, Pacqué MC, Muñoz B, Greene BM, Taylor HR. Viability of adult Onchocerca volvulus after six 2-weekly doses of ivermectin. Bull World Health Organ 1991;69(2):163-8.
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