Ultrastructural aspects of feeding and secretion-excretion by the equine parasite Strongylus vulgaris.

This research paper examines the origins of the immunogenic secretory-excretory product of the equine parasite Strongylus vulgaris and their impact on the horse host, involving the use of microscopy to observe how deep into the equine’s intestine the parasite attaches.

Attachment Mechanism of Strongylus vulgaris

• The study shows that the parasite attaches superficially to the horse’s caecum, a pouch located where the large intestine begins. Specifically, it leaves an oval-shaped area from where the epithelial cells, which line the interior of the bowel, are absent.
• It is noted that this layer of attachment does not extend so deep as to reach the muscularis mucosa layer of the equine intestine. The muscularis mucosa layer is a thin layer of muscle found beneath the intestinal mucosa which lends the mucous membrane of the intestine its tone and helps with absorption and secretion of mucus. Thus, implication being that while the parasites do damage the epithelial cells, they don’t penetrate deep enough to affect the muscularis mucosa.

Feeding Mechanism of Strongylus vulgaris

• The study highlights how the parasite feeds on the host’s tissues. The digestion of the ingested plug of tissue, comprising epithelial cells, blood cells, and mucous, was observed under microscopy.

Internal Structures of Strongylus vulgaris

• The paper describes the parasite’s internal floating cells, coelomocytes, and membranous structures that interact with the digestive, excretory, and reproductive systems and the somatic muscles, all found within the pseudocoelom, a fluid-filled body cavity of the parasite. The disclosure of these structures gives a clearer understanding of the functional features of the parasite’s internal mechanisms, which includes digestion, excretion, reproduction, and movement.

Secretory-Excretory System of Strongylus vulgaris

• The research also reveals the structure of the secretory-excretory system of the parasite. This system is made up of two ventrally-located glands, joined to tubular elements. These glands are responsible for synthesizing granules of various sizes and densities which may be part of the secretory-excretory product (ESP).
• The revelation of the secretory-excretory mechanism of Strongylus vulgaris, the ESP likely plays an essential role in producing immunogenic responses in the host and may also assist in protection or survival of the parasite within the host animal.