Thorny-Headed Worms

Thorny-headed worms, or spiny-headed worms (Acanthocephala), a small group of organisms in terms of species number, considered by some zoologists as an independent type of the animal kingdom, and by others as a class of the roundworm type. Characteristics of S. They are dioecious. They lack any trace of digestive organs. They lead a parasitic way of life. At the anterior end of the body there is a special organ-the proboscis, armed with rows of hooks (with the exception of the genus Apororhynchus Shipley, 1900). The proboscis can be retracted into the depth of a special proboscis sheath and protruded outward. In the male there are two testes, a group of prostate glands, and bursaco-pulatrix with a penis, located at the posterior end of the body. In the female, two ovaries are present only in young age: soon they break up into groups of egg cells floating freely in the body cavity (so-called floating ovaries). Fertilization and maturation of eggs and their envelopment in typical shells occur here. The eggs are characterized by the following features: they are always surrounded by three shells, of which the inner one, enclosing the embryo, is the most delicate; the outer shell is either very delicate and elastic or, conversely, hard; the middle shell most often has various kinds of depressions on both poles. The biology of S. is characterized by the presence of intermediate hosts, which are as a rule arthropods-insects or crustaceans. Man is not an obligatory host for any of the S. species; all described cases of human infection with S. depended on the accidental or experimental swallowing of intermediate hosts-insects infected with larval forms of these worms. In the list of human thorny-headed worms, 3 species of S are listed: Moniliformis moniliformis (Bremser, 1811), Macracanthorhynchus hirudinaceus (Pallas, 1781), and Echinorhynchus hominis (Lambl, 1859). Moniliformis moniliformis is a typical parasite of rodents. The male reaches 40-86 mm in length, the female 70-240 mm. A characteristic feature is the presence of numerous ring-shaped thickenings on the body, giving the parasite a bead-like appearance. The proboscis is armed with 12-16 longitudinal rows of hooks, with 10-12 hooks in each. Mature eggs reach 0.109-0.137 mm in length and 0.057-0.063 mm in width. Intermediate hosts are the cockroach Periplaneta americana and the beetle Blaps mucronatus. In humans, this parasite was detected 3 times. Callandruccio in 1888 performed an autoinfection experiment on himself, swallowing several larvae of this thorny-headed worm from the body cavity of the beetle Blaps mucronatus. After 3 weeks, the experimenter developed acute abdominal pain, diarrhea, and great weakness; after 5 weeks, S. eggs appeared in the excretions; in the seventh week, the pain became so aggravated that peritonitis could be assumed to have begun. After taking a large dose of male fern, 53 adult S. were expelled from the patient, after which everything gradually returned to normal. Macracanthorhynchus hirudinaceus is a large worm, an obligatory parasite of pigs and wild boars, reaching a length of 100-150 mm (male) and 300-650 mm (female). On the proboscis there are 12 longitudinal rows of hooks with 3 hooks in each. Eggs reach 0.08-0.10 mm in length and 0.051-0.056 mm in width. Intermediate hosts are the May beetles (Melolontha melolontha) and the rose chafers (Cetonia aurata). The first author to indicate the parasitism of this S. in humans was Lindeman (1867), who reported that this parasite "often" (?) occurs among the Volga peasants. No other authors besides Lindeman, claiming the ability of Macracanthorhynchus hirudinaceus to parasitize in humans, existed until recently, but in 1921, during the examination of 1,236 human coprological samples in Brazil, eggs of this S. were found twice [Gavião Gonzaga, cited by Brumpt (1927)]. If the diagnosis of the Brazilian researcher is correct, his cases should be considered the first and only ones proving the ability of M. hirudinaceus to parasitize in humans. In 1929, Karibov, while examining 409 people in Tiflis, found in one patient in the feces an egg measuring 0.0994 in length and 0.0528 mm in width; inside the embryo with hooks was clearly visible. The author diagnosed this egg as belonging to Macracanthorhynchus hirudinaceus. At the same time, he adds that "repeated examinations of the feces for this helminth gave a negative result." Thus, this case also cannot be considered reliable. The literature contains a note that by Lambl (1859) in the intestine of a boy who died from leukemia, a thorny-headed worm-Echinorhynchus hominis-was found. This parasite is described so inaccurately that it is impossible to determine its position in the taxonomy, so in recent years helminthology completely ignores this case as unverifiable.