Helminthofauna

Helminthofauna of humans, i.e., that fauna of parasitic worms which is characteristic of humans, is extremely diverse. In humans, 134 species of parasitic worms have been recorded, belonging to all four of their classes (Nematoda-71 species; Cestoda-32; Trematoda-29; Acanthocephala-2) and capable of parasitizing in all possible combinations. Each representative of human helminths has its own localization (see Human Helminthiases). The number of individuals of one species that can infect a human can range from one to tens of thousands. The number of different species of parasitic worms in one individual can range within a few units. The character of the human helminthofauna, both in qualitative terms and in terms of invasion intensity, can vary depending on the most diverse conditions. Thus, the influence of geographical factors is of great importance. A whole series of parasitic worms are found exclusively in tropical and subtropical countries, because their development in the larval stage requires certain conditions of temperature, humidity, and others characteristic of these countries, or occurs in an intermediate host - in some insect, etc., found only in this locality. Such are, for example, representatives of the genus Schistosoma, Paragonimus, various threadworms, hookworms, and others. The ethnographic factor can also exert a tremendous influence on the helminthofauna of the population. Thus, for example, peoples whose lifestyle features include eating raw or semi-raw beef are massively infected with unarmed tapeworm (or beef tapeworm); the extremely widespread distribution of this parasite exists in the Autonomous Bashkir SSR, among some peoples of the Caucasus, Siberia (Oiratia), and others. Age and sex also influence the helminthofauna of humans. Thus, although no age, including intrauterine life, guarantees a person against the possibility of helminth invasion, however, children older than infancy and adolescents are most frequently infected. Finally, the helminthofaunistic status of the population of any given area can vary among different population groups depending on professional factors. Thus, in temperate countries, hookworms are parasites of miners, because their larvae, developing on the earth's surface in tropical and subtropical countries, in temperate countries can develop only in the depths of mines, where the conditions of temperature, humidity, etc. approach those of warm countries. The USSR is insufficiently investigated in helminthofaunistic terms, and the helminthofauna of humans in some regions, for example, the entire northern part of the Siberian Krai, Yakutia, and some others, is almost completely unknown. In the central zone of the European part of the Union, roundworms predominate. In first place is the pinworm; infection with this parasite, as in all other areas, is very high and reaches 100% among many population groups. The next two most common species are the ascarid and whipworm. The frequency of finding ascarids varies in different points of the central zone and among different population groups from a few percent to 80%, and perhaps more. Whipworm shows less sharp fluctuations (about 20% for Moscow). Representatives of the family Trichostrongylidae are less frequently encountered, trichinella is encountered, about the distribution of which in this and other areas there is a very weak representation. Among cestodes, in first place is the dwarf tapeworm (in Moscow, about 3% of children are infected with it). The beef tapeworm is less frequently encountered, and even less frequently - the pork tapeworm, which also occurs in larval form (a number of cases of cysticercosis of the eyes, brain, muscles are known). Among larval forms of cestodes, echinococcus is not uncommon. The broad tapeworm is rare in this area, and it is possible that it is generally an import from the Baltic states and the north, where it is widely distributed. Among trematodes, Fasciola hepatica (Ivanovo-Voznesensk) and Dicrocoelium lanceatum (Ivanovo-Voznesensk, Moscow, Tver, Penza, Sverdlovsk) have been identified. The northern part of the European part of the USSR appears to be poorly investigated, however, there the character of the human helminthofauna is apparently somewhat different. Besides pinworms, the broad tapeworm has a sharp predominance over other forms in the north (Arkhangelsk Province). Among some population groups, ascarids are encountered, while whipworm is apparently completely or almost completely absent. In Belarus, besides the usual species characteristic of the central region, which are spread here in an even higher percentage, trichinella has significant distribution, giving in some points intense foci of trichinosis infection. Transcaucasia, repeating all forms of the central region, is characterized by an extremely high percentage of invasion, its intensity, and, in addition, by some species characteristic of warm countries. Thus, the percentage of ascarid invasion in Transcaucasia is 70 and higher, of whipworm - from 70 to 100, Trichostrongylidae (for Armenia) - 20.2 (among some population groups - up to 52); beef tapeworm in some localities - up to 60. Among parasites characteristic of warm countries, hookworms have extremely widespread distribution - Ancylostoma duodenale and Necator americanus, mainly the latter. The percentage of invasion with them of the population of the Black Sea coast of the Caucasus exceeds 90 in some points. In various points, there are a few cases of Strongyloides stercoralis. Very little is known about the invasion of the northern coasts of the Black and Azov Seas. However, hookworms are apparently not encountered there, except for imported cases. The percentage of whipworm invasion, and perhaps ascarid as well, approaches that in the Caucasus. In the helminthofauna of Siberia, if we exclude pinworms, roundworms recede to a second place, and the beef tapeworm has a sharp predominance over other species (in some regions almost universal infection). The distribution of the dwarf tapeworm is apparently approximately the same as in the European part of the USSR. As for the ascarid and whipworm, which predominate in the latter, the percentage of their distribution in Siberia usually ranges from a few tenths of a percent to a few units. Extremely characteristic for the Siberian Krai is the Siberian fluke (Opisthorchis felineus), which has wide distribution in the basins of Siberian rivers. The Far East was investigated in helminthofaunistic terms in the summer of 1923 by the 60th Union Helminthological Expedition. The helminthofauna of humans in Central Asia is also different from that of other regions. Of nematodes, excluding pinworm, in first place is the whipworm (10%), occupying in terms of distribution an intermediate position between the European part of the USSR and the Siberian Krai. Ascarid, as in the Siberian Krai, is rarely encountered. In Turkmenistan, foci of hookworm have been registered. In one point in Uzbekistan, namely in Old Bukhara, the guinea worm, a parasite of human subcutaneous tissue, not found anywhere else in the USSR, is quite widely distributed. Among tapeworms among the native population, carriers of the beef tapeworm are often encountered. The dwarf tapeworm is distributed here even more frequently than in other regions of the USSR (6%). In Turkestan, trematodes are encountered in humans; besides Fasciola hepatica and Dicrocoelium lanceatum, cases of Fasciola gigantica and Fasciolopsis buski have been described there. As for other countries of the globe, the pinworm is extremely widespread everywhere. To a greater or lesser degree, ascarid, whipworm, beef tapeworm, and pork tapeworm are cosmopolitan; the last two, and especially the pork tapeworm, are less frequently encountered. Hookworm and necator are among the most common parasites of the tropics and subtropics, infecting almost the entire population in some regions. There, the Bancroftian filaria - Wuchereria bancrofti (Japan, China, Indochina, Australia, America, Egypt) - is also a very widespread parasite, not found in the USSR. Some blood flukes of warm countries have very great importance due to their wide distribution and the severe clinical picture they cause. Thus, Schistosoma haematobium is very widespread in Africa and Asia Minor, and partly Schistosoma mansoni, which is a very common parasite in America. In China and Japan, Schistosoma japonicum is widespread, and there also the intestinal fluke - Clonorchis sinensis and the pulmonary fluke - Paragonimus are found.

where 5389 is the number examined; signs in parentheses: in the numerator - Trichocephalus trichiurus was found in 22.8%, Ascaris lumbricoides - 3.9%, Hymenolepis nana - 1.6%, Taenia saginata - 0.7%; 27.7 is the percentage of helminth units and 25.5 is the percentage of infection; 12 is the number of species found. Charushin (1928) proposed a modification of the 'GCI' of Skryabin-Schultz and some new indices: of deworming and control of deworming.