Evaluation of pyrantel pamoate, nitramisole and avermectin B1a against migrating Strongylus vulgaris larvae.

The research article is a study investigating the effectiveness of three drugs, namely pyrantel pamoate, nitramisole, and avermectin B1a, in combating larvae of the parasitic worm Strongylus vulgaris in ponies.

Introduction and Background

• Strongylus vulgaris is a parasitic worm that poses a significant health risk to horses and ponies. Its larvae migrate inside the host, causing severe complications, including arteritis and thrombosis of the major abdominal arteries.
• The researchers conducted trials to evaluate three drugs – pyrantel pamoate (already commercially available), and two newer anthelmintics, nitramisole and avermectin B1a (not yet commercially available).

Methods

• Young ponies were reared in isolation and remained worm-free until six to 14 weeks of age. They were then infected with 2000 or 2500 infective S. vulgaris larvae as a part of the study.
• After the infection, the ponies were monitored daily for clinical signs such as increased body temperature, and reduced appetite. The experiment lasted for 28 days post-infection.
• All three drugs were administered on day 7 after the infection. An additional dose of pyrantel pamoate was given on the 8th day as well.
• Nitramisole and pyrantel pamoate were administered using a stomach tube, while avermectin B1a was given via subcutaneous injection.

Results and Findings

• The administration of the drugs did not result in any toxic reactions in the ponies. However, they all brought about a reduction in body temperature and increased appetite, indicating a clinical cure.
• Ponies that didn’t receive any treatment showed persistent elevated temperatures and loss of appetite. These ponies also displayed a variety of symptoms such as lethargy, depression, recumbency, and colic, with the majority dying within two to three weeks post-infection.
• Post-mortem examinations of untreated ponies showed considerable adhesions involving the abdominal organs, necrosis of the ileum and cecum (parts of the large intestine), and severe arteritis and thrombosis.
• While pyrantel pamoate was able to effect a clinical cure, it didn’t achieve a radical cure (complete eradication of the larvae). Ponies treated with pyrantel pamoate still exhibited arteritis and thrombosis.
• On the other hand, nitramisole and avermectin B1a were effective in achieving both the clinical and radical cure, displaying their potential as effective treatments for S. vulgaris infections in ponies.