Page 73 - The Veterinary Care of the Horse

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Figure 2.22 Heavy infestation of bots in a horse’s stomach – seen at post mortem

Clinical signs Some horses are very bothered by the adult flies and will run round the field to

escape them. Bots rarely cause clinical signs in the horse unless they are present in very large
numbers when they occasionally cause significant gastric ulceration, perforation and death.

Control Where possible, eggs should be removed from horses on a daily basis. Autumn or
early winter treatment with moxidectin or ivermectin will kill the larvae present in the mouth

and stomach.

Gasterophilus percorum has recently been found in the UK for the first time. It differs from
the other bot species by laying eggs on the pasture. These are eaten by the horse, and the

larvae attach to the soft palate. Symptoms include coughing and difficulty eating. It is
possible that this parasite which is common in some parts of Europe may be seen more
commonly in the UK in future, possibly the result of global warming.

LUNGWORM – Dictyocaulus arnfieldi

Adult size and colour Slender white worms up to 8 cm (3 in) long.

Life cycle The adult worms live in the bronchi of infected donkeys. They lay eggs which are