The Effect of Repeated Anthelmintic Treatment with Phenothiazine on the Faecal Egg Counts of Housed Horses, with Some Observations on the Life Cycle of Trichonema spp. in the Horse

Abstract

It was found that in six aged horses after treatment with 30 grammes of phenothiazine the faecal egg count fell to zero but had returned to a high level after some live or six weeks. Examination of the faeces at the time of treatment showed that many worms were eliminated. Repetition of the treatment several times produced a similar result on each occasion, but there was a tendency for the egg count not to rise so high as it was before treatment, for fewer worms to be eliminated at each treatment, and for the time before the egg count reached a high level after treatment to lengthen with each successive treatment. Many treatments had to be given over a period of some three years before the egg counts of the horses were reduced permanently to a low level. Post-mortem examination of three of the horses at this stage showed their worm burdens to be low.