Critical tests with polymethylenepiperazine (PMP) against parasites of the horse.

This study investigates the efficacy of polymethylenepiperazine (PMP), a drug, in treating various parasitic infections in horses, observing the effect on different types of worms and the optimal dosage for effective treatment.

Study Design and Procedure

• The researchers administered polymethylenepiperazine (PMP) to five horses at varying dose levels (either 21, 51 or 106 mg per Ib. body-weight), to study its effectiveness against different parasitic worms.
• The horses were observed for clearance of worms post-treatment and then autopsied four days after treatment.
• Another set of eight horses were also subjected to critical testing, with dosages given ranging from 5 to 13 mg. per Ib.
• The drug’s effectiveness was finally tested on 21 horses at a dosage of 40 mg. per Ib. to understand its effect on one specific type of parasites (Strongylus vulgaris).

Main Findings

• All dosages resulted in the clearance of ascarids (a type of roundworm).
• The drug was less successful against oxyurids (pinworms) as many immature worms were found during autopsy.
• About 85% of small strongyles (intestinal worms) were removed with dosages of 21 mg per Ib. and above.
• Strongylus vulgaris (bloodworms) was cleared in about 50% of the horses with 51 mg per Ib. dosage and above.
• However, PMP was found to be inactive against several other worm species, including S. edentatus, Trichostrongylus axei, Habronema muscae, and Strongyloides westeri.
• In the second set of eight horses, 100% efficiency against Parascaris equorum (equine roundworm) was observed at a minimum dosage of 10 mg. per Ib.
• Limited and inconsistent efficacy was noticed against Oxyuris equi (equine pinworm).
• This dosage level, when given via a stomach tube, was also effective against small strongyles, but was less effective when given in feed.
• In the final non-critical tests on 21 horses, 40 mg per Ib. dosage was needed for significant removal of Strongylus vulgaris.

Conclusions

• The study suggests that PMP can be effective in treating certain types of parasitic infections in horses at varying dose levels
• However, its effect on different worms varies considerably, with some types not affected at all by the drug.