The whole complex of pathological effects of the parasite on the host depends on many factors: the type of the parasite, its virulence, population, habitat, developmental biology, and the physiological state of the host. The mere concept of physiological state of the host includes a number of factors that may affect the development and influence of pathogenic parasite on the body, for example, the immune status of the organism, age, type of feeding, and housing.
Virulence (degree of pathogenicity) of the parasite plays great importance in the relationship parasite-host. Virulence depends on the infection properties of the parasite and the susceptibility of the infected host. The virulence of the parasites can be enhanced as the temperature increases. For example, ado- Lescar Fasciola, grown at 22-23°C, cause acute fascioliasis in rabbits; grown at 15-17°C resulted in only chronic disease.
Pathogenic effects on the animal caused by infection with the parasite can be divided into several groups: mechanical, allergic, toxic, trophic, and inoculator-like.
The mechanical effect of the parasite on the host organism is conditioned to its habitat and biology of development. It is clear that the helminth localization in the intestinal lumen is less palpable than in the liver or the brain. Moreover, one should consider the migration of larvae (ascaris) on ascarid or non-ascarid type. Mechanical impact of mites during parasite on the skin of cattle is less pronounced than the migration of the larvae of subcutaneous gadfly in the thickness of the skin and musculature of infected animals. Localization of large bubbles of Echinococcus in parenchymal organs of animals or Dirofilariasis in heart ventricles and atria causes atrophy not only of parts, but the whole body.
Allergic effects of parasites lies in the fact that during the life they excrete metabolic products, secretion and excretion, which primarily have the properties of allergens. Helminth allergens are complex compounds. Under their influence, there is an allergic reaction in the body of infected animals.
The toxic effects of parasitic organisms in general are studied poorly. Until now nobody has been able to allocate toxins in helminths. However, during chronic helminths as a result of metabolic disorders patients often have toxicosis. Patients also have deteriorating general condition, decreased appetite, the function of the gastrointestinal channel is upset, the number of red blood cells reduces, as well as hemoglobin.
The whole complex of pathological effects of the parasite on the host depends on many factors: the type of the parasite, its virulence, population, habitat, developmental biology, and the physiological state of the host.