Effects of repeated Strongylus vulgaris inoculations and concurrent ivermectin treatments on mesenteric arterial lesions in pony foals.

The research article investigates the effects of continuous Strongylus vulgaris (a widespread equine parasite) inoculations and parallel ivermectin treatments on the mesenteric arterial lesions in pony foals. The study indicates that ivermectin can effectively minimize parasite numbers and resultant arterial damage, and does not enhance lesions linked to verminous arteritis or instigate unique lesion formations on repeated execution of arterial larvae.

Study Methodology

• The researchers tested on 10 pony foals raised under parasite-free conditions. Eight of these foals were orally inoculated with 50 infective larvae of the Strongylus vulgaris parasite weekly for four weeks. Unfortunately, one foal died due to acute verminous arteritis. The inoculations continued on seven foals at two-week intervals for another 20 weeks.
• Of these seven, three were treated with ivermectin in an oral paste formulation during the 8th, 16th, and 24th weeks of the experiment, while the other four were not treated at all. Ivermectin is an antiparasitic medication widely used in veterinary medicine.
• Lastly, two foals that were neither inoculated nor treated served as controls for comparing the effects.

Findings and Results

• After the first ivermectin treatment, the treated foals had fewer days with spiked rectal temperatures (an indicator of inflammation or infection) compared to untreated foals.
• Ivermectin treatment showcased no adverse clinical effects on the foals, signifying safety and tolerability of the drug in pony foals.
• Post three weeks of the last ivermectin treatment (week 24), foals were euthanized and necropsied for thorough examination. The autopsy reports confirmed the effective reduction of the arterial larval and adult intestinal parasites by a full 100% in the treated foals.
• On the contrary, S. vulgaris larvae or adult parasites were recovered from all four untreated foals. Interestingly, one among these four did not have either arterial larvae or active arterial lesions, which suggested that this individual developed a resistance against the parasite.
• Significant gross and histopathological lesions, typical of chronic S. vulgaris infection, were discovered in the three untreated foals with arterial larvae. However, the repeated destruction of intra-arterial S. vulgaris fourth-stage larvae in ivermectin-treated foals neither augmented the verminous arteritis-related lesions nor triggered any unique lesions.