Strongylus vulgaris

Introduction

Strongylus vulgaris is a clinically important parasite of the family Strongyloidea. It causes verminous arteritis and was a very common cause of colic in horses. Its prevalence has been on the decrease since the use of wormers containing ivermectin.

Scientific Classification

Kingdom	Animalia
Phylum	Nematoda
Class	Chromadorea
Order	Rhabditida
Family	Strongylidae
Genus	Strongylus
Species	S. vulgaris

Hosts

Horses and donkeys.

Identification

The adult worms are dark red. The male has a well developed buccal capsule. Both the male and the female worms have rounded teeth, which enable them to hold onto the intestinal mucosa.

The eggs are 100μm x 50μm.

Life cycle

The S. vulgaris eggs are shed in the faeces. Under optimal conditions of high humidity and temperatures over 10 degrees, the eggs will transform into rhabditiform L1 larvae within a few days.

They then transform into L2, and subsequently L3 without leaving the parasite envelope. L3 are ingested by the host when feeding on pasture. L3 enter the small intestine, where they shed their envelope, and then begin migration across the mucosal surface, where they transform into L4.

L4 reach the arterioles of the intestine. Around 2 weeks after the eggs were first ingested they reach the colic and caecal arteries, and then finally the cranial mesenteric artery.

L4 then transforms into the immature adult and returns to the L1 via the blood vessels. Here they form nodules on the wall of the caecum, and occasionally the colon, and are then released into the lumen.

The prepatent period for S. vulgaris is 6-7 months.