Page 65 - The Veterinary Care of the Horse

• corticosteroids to reduce the inflammation of the gut.

VetBooks.ir Treatment of young animals not showing signs but sharing the same grazing has to be done

with care. Removal of adult worms from the gut lumen may stimulate large numbers of
larvae to emerge from the gut wall at once and actually trigger the onset of severe and

possibly fatal diarrhoea. These horses should be closely monitored after being wormed and
treated at once if diarrhoea develops. Some severely affected animals recover over a 2–3
month period but the mortality rate can be as high as 50%.

LARGE STRONGYLES (LARGE REDWORM) e.g. Strongylus vulgaris

Adult size and colour 1.4 – 2.5 cm ( in), red in colour (Figure 2.16).

Figure 2.16 Large strongyles

Life Cycle The adult worms of St. vulgaris live in the large intestine, attached to the gut wall.

Here they cause damage leading to blood and protein loss. They also release chemicals which
affect the normal movement of the gut. The adult worms lay eggs which pass out on to the

pasture in the faeces. Infective larvae develop from the eggs and when these are ingested,
they burrow through the gut wall, into the intestinal arteries. They cause inflammation within
the blood vessels and the formation of blood clots which can cause loss of the normal blood