Paragonimus westermani ichunensis and paragonimosis in the south of the Russian Far East: yesterday, today and tomorrow

Paragonimosis is a severe parasitic disease, which causative agent (on the territory of Russia, trematode Paragonimus westermani ichunensis Chung, Hsu et Kao, 1978) circulates in the south of the Far East. Two forms of paragonimosis are known: pulmonary and muscular (larval) with clinical manifestations like diseases of a different etiology, mimicking the symptoms of malignant tumors, and in cases of late diagnosis and improper treatment, leading to death. Long-term studies of the ecology and biology of the parasite, as well as monitoring the incidence among residents of the southern Far East of Russia made it possible to analyze the situation with paragonimosis in the designated region. Based on the available data, until the mid-1990s, natural sites of disease were found almost everywhere in the river basins inhabited by mollusks of the genus Parajuga and crayfish of the genus Cambaroides as parasite intermediate hosts. During this period, according to official information, the population invasion rate reached 6%. Then, as a result of the mass extinction of freshwater crayfish, the population of P. westermani ichunensis was on the brink of survival, and from that moment on, the number of diagnosed cases of paragonimosis in the inhabitants of the region began to decline, down to zero in recent years. Currently, the population of crayfish Cambaroides is reviving and a case of P. westermani ichunensis infestation of a tiger cub has been recorded, which indicates the population restoration of the parasite itself. This indicates the functioning resumption of the Paragonimus sp. infection centers in the south of the Russian Far East. It is necessary to be prepared for the possibility of an exponential growth in the number of infected animals with such a developmentтof events. Due to the complexity of the disease diagnosing and the lack of certain knowledge about the parasite biology among the majority of medical workers, it is necessary to be ready to low detection rate among the region population.