Efficacy of ivermectin against Onchocerca cervicalis microfilarial dermatitis in horses.
Abstract: Forty horses having microfilariae of Onchocerca cervicalis in association with dermatitis, alopecia, and pruritus on the ventral midline were given a single IM injection of 0.2 mg of ivermectin/kg of body weight (June to August 1981). Microfilarial counts in the 40 horses ranged from 18 to 42,446 microfilariae/skin snip on the day of treatment, and histopathologic examination of these skin sections indicated a chronic eosinophilic dermatitis. Numerous microfilariae were in the dermis, but there was no consistent relationship between the presence of microfilariae and the severity of the inflammatory reaction. In all 40 horses, skin snips taken 4 to 33 days after treatment were negative for microfilariae, and a marked clinical improvement occurred 2 to 3 weeks after treatment, when the lesion was replaced by healthy skin and new hair. Twenty-four hours after treatment, an edematous reaction occurred on the lower portion of the abdomen of 4 (10%) horses and within the area of the lesion in 6 (15% horses). The reactions disappeared within 24 to 72 hours, irrespective of whether horses were treated with corticosteroids. When further skin samples were taken from 15 horses 4 to 9 months later, 9 of them were free of microfilariae and the 6 others had only low counts (17 to 97). An additional 7 infected horses, treated when there was little chance of reinfection (November to December 1981), were all free of microfilariae at 6 to 10 days and 4 to 5 months after treatment. The marked clinical improvement in all horses after disappearance of microfilariae from the dermis indicates that microfilariae are involved in the cause and pathogenesis of the dermatitis.
Publication Date: 1983-06-01 PubMed ID: 6688162
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study investigates the effectiveness of the drug ivermectin in treating a condition known as microfilarial dermatitis in horses, which is caused by the Onchocerca cervicalis parasite.
Research Methodology
- The research involved forty horses suffering from microfilarial dermatitis. This is a skin condition accompanied by hair loss and itchiness, caused by the microfilaria of the parasite Onchocerca cervicalis.
- An in-depth examination of the affected horses revealed the presence of microfilariae ranging from 18 to 42,446 per skin snip, leading to a chronic inflammatory response known as eosinophilic dermatitis.
- Each horse was treated with a single intramuscular injection of 0.2 mg of ivermectin per kg of body weight. This treatment took place between June and August 1981.
Results Post-Treatment
- The treatment showed promising results, with all horses tested proving negative for microfilaria between 4 and 33 days post-treatment.
- There was a significant clinical improvement in the horses’ condition 2 to 3 weeks following the treatment. The skin lesions healed, replaced by healthy skin and new hair growth.
- In some cases (10% of horses), swelling occurred in the lower abdomen. In 15% of horses, the area of the prior lesion experienced swelling. These side effects disappeared within 24 to 72 hours, regardless of whether horses were treated additionally with corticosteroids.
Follow-Up Results
- Further skin samples were taken from 15 horses 4 to 9 months after treatment. 60% of these horses remained free of microfilariae, while the remaining 40% showed very low counts (17 to 97).
- Another group of 7 horses that were treated when there was less chance of reinfection (during the months of November and December 1981) were all free of microfilariae 6 to 10 days and again 4 to 5 months after treatment.
Conclusion
- The study concluded that ivermectin posed an effective treatment for microfilarial dermatitis caused by Onchocerca cervicalis in horses.
- Additionally, the recovery of the horses post-treatment and the disappearance of microfilariae from the dermis indicate that microfilariae play an essential role in the cause and development of the dermatitis.
Cite This Article
APA
Herd RP, Donham JC.
(1983).
Efficacy of ivermectin against Onchocerca cervicalis microfilarial dermatitis in horses.
Am J Vet Res, 44(6), 1102-1105.
Publication
Researcher Affiliations
MeSH Terms
- Animals
- Anthelmintics / therapeutic use
- Dermatitis / drug therapy
- Dermatitis / veterinary
- Filaricides / therapeutic use
- Horse Diseases / drug therapy
- Horse Diseases / pathology
- Horses
- Ivermectin
- Lactones / therapeutic use
- Microfilariae / isolation & purification
- Onchocerca / isolation & purification
- Onchocerciasis / drug therapy
- Onchocerciasis / pathology
- Onchocerciasis / veterinary
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