Test systems for diagnostics of parasitic diseases
PCR tests for the diagnosis of helminthiasis and protozoan invasions allow for the highly accurate detection of parasite DNA, including roundworms, flatworms, and protozoa, which is especially important when microscopic diagnostics are difficult and early detection of infection is necessary.
Helminthiasis and protozoal infestations
Helminth-protozoan infections are very common; approximately 350 parasitic pathogens are known. In Russia, 1.5–2 million cases of parasitic diseases are registered annually, with children accounting for 80% of these cases.
Helminths that parasitize humans belong to two types:
- roundworms (class Nematoda);
- flatworms (class Cestoidea, or tapeworms); and class Trematoda (flukes).
Based on the transmission mechanism and the parasite's life cycle, helminthiases are divided into two groups:
- geohelminthiases (eggs/larvae) of the pathogen are excreted from the infected person's body in the feces into the environment, where they mature to the invasive stage. The source of infection can be contaminated soil, water, food, or household items. This subtype of helminthiases includes ascariasis, trichuriasis, hookworm infection, strongyloidiasis, and others. Infection occurs through poor personal hygiene (primarily through dirty hands), when the eggs/larval forms of the parasite enter the soil with the feces of an infected person and from there into the body of a new host.
- biohelminthiases (in addition to the definitive host, in which the helminths reach sexual maturity, the causative agents of biohelminthiases require an intermediate/additional host for the development of the larval stages). This type includes diphyllobothriasis, taeniasis, echinococcosis, opisthorchiasis, filariasis, trichinosis, and others. Infection occurs through the consumption of undercooked contaminated meat, lightly salted/raw fish, or contaminated raw water.
The pathogenic effect of helminths on the host is due to the antigenic action of the parasites, as well as the action of enzymes (hyaluronidase, collagenase, cholinesterase, peptidases) secreted by migrating larvae. Clinical manifestations of helminthiasis are characterized by general allergic reactions (urticaria, allergic rhinitis, etc.), dysproteinosis, and, if prolonged, severe degenerative processes. In chronic cases, in addition to the sensitizing effect of parasites, mechanical damage (damage to the intestinal mucosa by the helminth's fixation apparatus, obstruction of bile flow due to the development of echinococcal cysts) can also have a significant impact.
Protozoal infections are diseases caused by single-celled protozoa. According to current data, approximately 50 species of protozoa can pose a danger to humans. Protozoa can be transmitted to humans through insect bites, food, and sexual contact. The most significant, due to their high prevalence, are amebiasis, toxoplasmosis, leishmaniasis, giardiasis, and trichomoniasis. Protozoa are parasitic and affect various organs and tissues—the circulatory system, intestines, central nervous system, liver, lungs, etc.—and cause allergic reactions.
Diagnosis of helminthiasis and protozoan infestations is based on a combination of laboratory and instrumental tests. Laboratory diagnostics include clinical and biochemical blood tests, microscopic examination of biological samples (feces, blood, urine, bile, duodenal contents, sputum, etc.), serological methods (IFA, RNGA, ELISA), and molecular diagnostic methods (PCR diagnostics for detecting helminth and protozoan DNA). PCR is particularly important for identifying pathogens such as Lamblia intestinalis and Blastocystis hominis, which are often difficult to diagnose microscopically.