The purpose of the research is studying microstructural changes in the process of adaptation of components during the formation of the “parasite–host” system by the example of Paramphistomum cervi (Zeder, 1790) parasitizing in the small intestine of spontaneously infected sheep. Materials and methods. Peculiarities of changes in the microstructure of the small intestine in the “parasite–host” system were studied using parasitization of P. cervi in the intestines of sheep using well-known histological methods. Pieces of tissue of the small intestine of sheep with P. cervi, after being preserved in 70% alcohol, were processed according to the generally accepted histological procedure and embedded in paraffin. Sections 5–7 μm in thickness were stained with histological stains and examined under a light microscope. Results and discussion. Microstructural analysis of the characteristics of the relationship in the "parasite–host" system showed that the mucous membrane of the small intestine of sheep in the presence of P. cervi looks sharply thickened. Swelling of the epithelium of villi and crypts, its vacuolization and albuminoid degeneration were found. In some places, proliferation of the epithelial layer of the mucous membrane was detected, due to which epithelial hyperplasia is observed, in some cases turning into metaplasia. Proliferation and hyperplasia (metaplasia) in the endostation of the host in the presence of the parasite contribute to: 1. stability of the parasite-host system and the participation of trematodes in trophism; 2. determination of the clinical and morphological picture of trematodose; 3. predicting the effects of this pathology on the host. Adhesion in the microstructural complex “trematode tegument – epithelial tissue of the villi of the small intestine” in ovine paramphistomosis at the contact level of two glycocalyx layers – the tegument of P. cervi and the surface of the epithelial cells of the villi of the host’s intestine, as well as single histological staining of the sites of contact between the parasite and the host as a result of mixing the components of the trematode tegument and the tissue of the host’s small intestine with deep adhesion indicate the established mutual relations between the components of a single system "parasite–host".
Adaptation of the Relationship in the "Parasite–Host" System with Parasitism Paramphistomum сervi in the Small Intestine of Sheeps