Studies on the development and chemotherapy of larvae of Parascaris equorum (Nematoda: Ascaridoidea) in experimentally and naturally infected foals.

The study investigates the development of Parascaris equorum larvae in foals, both naturally and experimentally infected, detailing the timeline of their migration and reproductive maturity. It also explores the effectiveness of specific treatments in reducing larval numbers and delaying the appearance of eggs in feces.

Parascaris equorum Larvae Development

• This research tracked the life cycle of Parascaris equorum eggs in foals. The life cycle began with infection, either experimental or natural, into a host system that was free of prior infection.
• The migration process of the larvae was followed closely. It was observed that upon infection, the larvae move through the liver and lungs, a process that takes between 14-17 days.
• The maturation or gametogenesis of the larvae, when they become prepared for sexual reproduction, was also tracked and found to span from 79-110 days.

Chemotherapy and Its Efficacy

• A range of treatment methods were explored for their effectiveness in both reducing the overall quantity of P. equorum larvae present in the intestines of the foals and in delaying the appearance of P. equorum eggs in the feces of the foals post-treatment.
• Treatments included levamisole at a dose of 8 mg/kg, a mixture of levamisole at the same dosage combined with piperazine at 88 mg/kg, and dl-tetramisole at a dosage of 10 mg/kg.
• The effects of these treatments were quite successful, providing encouraging results in both reducing the number of these parasites present during postmortem examination and in delaying the appearance of eggs in the feces beyond the timeframes observed in untreated subjects.

Use of Dichlorvos and Trichlorfon

• The experiment also tested the efficacy of dichlorvos and trichlorfon at various doses. Administered at dosages of 10 mg/kg, 20 mg/kg, 30 mg/kg, and 40 mg/kg respectively, treatments using either dichlorvos or trichlorfon were found to be ineffective when given at or before the 14th day after infective eggs were administered.
• However, the gel formulation of dichlorvos presented vastly different results. This formulation, dosed at 20 mg/kg and administered between 17-28 days following the infection, was completely effective in eradicating larvae from the small intestines.

This study holds significant implications for future therapy for P. equorum-infected animals and showcases the effectiveness of particular treatments at different phases of the parasite’s life cycle.