The pathogenesis and control of strongyle infection in the horse

The migratory route of infective Strongylus vulgaris larvae was determined: penetration of small and large intestine into the lumina of submucosal arteries, migration up the arterial tree, reaching the cranial mesenteric site by three weeks, where the larvae develop to the mature 4th stage. After 3-4 months they exsheath and the young adults migrate down the arteries towards the intestines, to the limit of arterial narrowing, from where they rupture from nodules into the lumen of the intestine. The prepatent period is about 6 months. The clinical syndrome was similar to, but less severe than that recorded in the literature. The most significant haematological changes were an early, sharp rise in WBC, increased neutrophil:lymphocyte ratio, and eosinophilia. Marked, progressive increase of total serum proteins as result of betaglobulins occurred. The rate of albumin catabolism was higher in infected horses and red cell survival was reduced. In field studies, it was shown that foals turned out to grass in spring can be infected both by overwintering larvae and by their untreated dams, the latter being by far the more important source of infection.