Exmoor Ponies in Conservation Newsletter

Issue 2 Article 3


Tapeworm is not usually thought to be the most problematic parasite in equines, although this year their presence in large numbers contributed to the death of one of our ponies. Dunlin 14/21 suffered severe and fatal spasmodic colic in April, after a winter grazing on Gait Barrows. He had looked well until a week before the attack when he started to look 'tucked up'. and was brought home. The P.M. revealed a very heavy tape-worm infestation, despite our worming programme which included tape-worm dosage last autumn of a double Strongid P. Rather upset at the loss of a good pony and puzzled also, we contacted Pfizer. They commented as follows:- 'As soon as adult tapeworms are killed after worming, numbers start to slowly increase again as orbatid mites, the intermediate host to the equine tapeworm, are ingested during grazing; it takes only six to ten weeks for an adult tapeworm to develop after a mite has been swallowed. Eventually, the horse will once again have mature tapeworms in the gastrointestinal tract, which are then killed off with the next double dose of Strongid P. It would appear that your pony was reinfected with large numbers of tapeworms in the time between receiving the autumn double dose and his death in the spring. The most likely explanation for this is that the areas grazed by the pony have extremely high levels of orbatid mites.'

'Unfortunately (faecal analysis ) poses some practical difficulties; cost is the obvious one, but the need for multi samples is another, counts can vary between individuals and from day to day and may not necessarily correlate with the number of adult worms. The alternative would be to consider additional double doses of pyrantel during the year. There have been no reports of resistance of Anoplocephala perfoliata to pyrantel embonate (Strongid Ps active ingredient).'

Subsequent worming revealed that all the other ponies had tapeworm too. Why such large numbers of orbatid mites on the grass? Could it be another effect of the trend for warmer wetter climatic conditions? Comments welcome.

What do you mean, the pony's got worms?

A free booklet 'A Practical Guide to Worming Horses' is available from Pfizer Ltd, Sandwich, Kent CT123 9NJ. - worth having.

by Margaret Mackintosh