DEHELMINTHIZATION

DEHELMINTHIZATION (from Latin de - negative particle, and Greek helmins - parasitic worm), "the sum of measures having as their task either the removal, resp. expulsion, of parasitic worms from the host organism when they are located in organs communicating with the external environment, or the killing of helminths within the body of the host when they parasitize in closed cavities and tissues" (Skryabin). Skryabin divides dehelmintization into three categories: diagnostic, therapeutic, and preventive. These categories are characterized by the following features: I. Diagnostic dehelmintization has as its task the expulsion of parasitic worms to establish an accurate diagnosis of the invasion; it is applied in cases where ordinary helminthological research methods (helminthooscopy, helminthoscopy, etc.) prove powerless, which may be due to the following factors. 1. Anatomical-biological features of certain parasitic worms are the reason that their eggs enter the fecal masses only in exceptional cases. Thus, most cestodes have a closed uterus, and their eggs can enter the feces only when the segments decompose inside the host's intestine; pinworms (Enterobius vermicularis), although they have an open uterus, usually expel their eggs outside the host's body around the anus. With these types of parasitic worms, dehelmintization for diagnostic purposes gives much more accurate results than the coprological analysis method. 2. The imperfection of helminthooscopy methods (research for helminth eggs) leads to the fact that often, despite the presence of eggs in a given portion of feces, they still cannot be found. Moreover, there may indeed be no eggs in the feces if only males, larvae, or immature females inhabit the human intestine. In all these cases, diagnostic dehelmintization also gives more accurate results than examining feces for the presence of parasite eggs. II. Therapeutic dehelmintization aims to eliminate disorders caused by parasitic worms. III. Preventive dehelmintization aims to protect other beings and their environment (water, soil, etc.) from infection. Thus, a) freeing a person from Taenia solium protects pigs (as well as the patient himself) from cysticercosis, and consequently prevents human infection with Taenia solium and Cysticercus cellulosae; b) freeing a dog from the mature echinococcus living in its intestine protects humans (as well as all domestic animals) from infection with the larval form of this parasite, which can settle in any organ (mainly the liver); c) dehelmintizing people infected with Hymenolepis nana and Enterobius vermicularis prevents the possibility of both constant reinvasion of the patient himself and infection of those around him; d) freeing people from Ascaris and Trichocephalus prevents contamination of water and soil with the eggs of these parasites, and consequently infection of other people with these eggs; e) dehelmintizing the population of certain regions or enterprises in cases of ankylostomiasis and necatoriasis prevents the introduction of ankylostomes into mines and fields. Preventive dehelmintization is only beginning to develop, but in the future it is destined to play a huge role in the health improvement of the population. Even now, thanks to mass and mandatory dehelmintization in cases of ankylostomiasis and necatoriasis, it has been possible to improve a number of regions in Europe and other parts of the world (see Ankylostoma). Principles of dehelmintization. Whatever category dehelmintization belongs to and whatever type of parasitic worms of the gastrointestinal tract are to be expelled, the following basic principles must be observed to achieve the best results: 1. Preparatory treatment. Since intestinal parasitic worms are surrounded by intestinal contents that protect the parasites from the effects of anthelmintic agents, it is necessary to prescribe a liquid diet one or two days before treatment, and give a laxative the evening before. 2. Specific treatment. Since all anthelmintics are poisons not only for the parasite but also for the host, it is necessary to choose agents that are relatively poorly absorbed by the intestine. The chosen agent should, as far as possible, act specifically on the particular, accurately diagnosed parasite. When establishing the dose, it is necessary to take into account not only the age but also the general condition of the patient. It is necessary to exclude everything that serves as a contraindication to the administration of a particular drug (see also Anthelmintic agents). 3. Concluding treatment. Whether the parasites are killed or only stunned, it is necessary to expel from the body both the parasites themselves and the excess anthelmintic taken as soon as possible. Therefore, 2-3 hours after the specific medication, it is necessary to prescribe a strong laxative. Evaluation of the method. The success of the applied method should be judged not only by the patient's well-being but also on the basis of laboratory control data, two or even three times. The first control is performed no earlier than the action of the drug on the parasites ceases. It is known that parasites may not secrete eggs only because they are still in a state of stunning, and one might mistakenly take the delay in their egg secretion for the absence of parasites; therefore, the first control should be carried out approximately one week after treatment. The last control should be performed no later than the period during which adult parasites can develop from eggs that entered the host after treatment. The development period varies for different parasites: for Hymenolepis and Enterobius about 2 weeks, for Trichocephalus - 4 weeks or more, for large tapeworms - 2-3 months, for Ascaris - 2¹'₂ months, etc. It should be borne in mind that the development period depends not only on the zoological species of the parasite but also varies considerably depending on climatic (temperature, humidity) influences.