Activity of organophosphorus compounds against oral stages of gasterophilus intestinalis and Gasterophilus nasalis.

The research article examines the effectiveness of different organophosphorus compounds in controlling larvae of Gasterophilus intestinalis and Gasterophilus nasalis in the mouth tissue of horses and ponies. These larvae infections were both naturally acquired and experimentally induced.

Methodology and Compounds Tested

The researchers conducted controlled tests using the following organophosphorus compounds: dichlorvos, trichlorfon, trichlorfon butonate, and carbon disulfide. These compounds are known for their activity against parasites, particularly bots. The tests were executed under two conditions: experimental parasitisms in pony foals and naturally acquired parasitisms in horses.

• Doses of each compound were delivered differently: Some were given on the feed, and some were administered via a stomach tube or intraorally.
• For instance, a resin-pellet formulation of dichlorvos was administered on the feed of pony foals at the dosage level of 37 mg/kg. In contrast, a gel formulation of dichlorvos was given intraorally to horses at the dose level of 36 mg/kg.
• Furthermore, various forms of trichlorfon and trichlorfon butonate were delivered either on the feed or intragastrically.
• Liquid carbon disulfide, on the other hand, was administered to horses via a stomach tube at the dosage level of 2.4 ml/45.45 kg body weight.

Research Findings

Detailed observations and results were reported on the efficacy of the tested compounds against the Gasterophilus larvae.

• All the organophosphorus compounds tested, except carbon disulfide, demonstrated 100% efficacy against the larvae in the experimentally induced infections in pony foals.
• The treatments included dichlorvos given on the feed, two forms of trichlorfon administered via a stomach tube, another form of trichlorfon given on the feed, and trichlorfon butonate given intragastrically.
• Against naturally acquired infections in horses, only the dichlorvos gel showed significant efficacy, while carbon disulfide was ineffective.

Conclusions and Implications

The findings suggest a potential use of organophosphorus compounds, particularly dichlorvos and trichlorfon, in controlling Gasterophilus larvae infestations in horses and ponies. It shows the importance of the form and the route of delivery of the compounds in its efficacy. Further research may explore other compounds and methodologies to control these parasitic infestations.