What is Hymenolepidosis?
Hymenolepidosis is a chronic parasitic disease that develops when parasitic in the human intestine of the tapeworm Hymenolepis nana, or dwarf chain.
Hymenolepidosis is common almost everywhere, but most widely among the population of the southern climatic zones. It is widely distributed in Latin America, North Africa, Italy, Iran, Pakistan, Afghanistan, in the countries of the near abroad – Central Asia, Kazakhstan, Moldova, Azerbaijan, Georgia, Armenia, Russia – in the North Caucasus, in Tomsk, Amur and others. areas. In Ukraine, it is registered everywhere, more often in the southern regions, i.e., areas of a more dry and hot climate, where ascariasis is relatively rare. These areas are unfavorable for the spread of ascariasis – a natural endemic invasion.
In the foci of ascariasis, hymenolepiasis almost never occurs. The lack of frequent combination of these invasions in humans is explained by the presence of relative antagonism in these helminths, which is due to the peculiarities of the host intestinal microflora, the composition of which varies depending on the type of helminth and the intensity of invasion.
Hymenolepiasis affects predominantly urban populations. More often, children of 4–14 years of age are ill, which is explained by the insufficient upbringing of their hygienic skills, as well as the peculiarities of age immunity.
The foci of hymenolepiasis are formed in preschool institutions, schools, boarding schools, orphanages, microchip in families. The level of infestation depends on sanitary conditions, crowding, and social difficulties. It has been established that these foci and micro-foci arise and transform “persistent” where there are infested with pinworms. This is due to the fact that the eggs of the dwarf chain when scratching the perianal area (itch) contaminate the fingers, this contributes to autoinvasion, as well as infection of others.
The source of infection is an invasive person. Rodents are of secondary importance – rats, mice that are susceptible to H. nana, and are also widely infested by a close species – H.fraterna – a dwarf chain of rodents. Infection of a person with it can occur only if the larvae of certain insects, their intermediate hosts, are accidentally swallowed.
Children have the greatest epidemiological significance as sources of invasion, as well as relevant professional groups of people: food workers, personnel of children’s institutions, etc.
Hymenolepidosis is characterized by a fecal-oral transmission mechanism. The main factors of transmission of the invasion are dirty hands, household items (toys, dishes, pots, door handles, etc.), food products. Dwarf chain eggs can get into the mouth with dust, soil, water, and food products can be brought in by flies.
At room temperature, N. dad’s eggs remain viable for 1–2 days, 3–4 hours on the fingers, in conditions of constant humidity, and in water for 3–4 weeks. Temperature + 60 ° С kills all eggs in 15 minutes, at –3 ° С they die in 35-40 minutes. Drying and the sun’s rays affect eggs.
Causes of Hymenolepidosis
The causative agent, the dwarf chain Hymenolepis nana (Siebold, 1852; Blanchard, 1891), belongs to the order Cyclophyllidea, the family Hymelnolepididae, the genus Hymenolepis. It was first discovered in Egypt (Cairo), in Russia it has been known since 1890 (St. Petersburg).
The dwarf tapeworm is a small whitish cestode 1.5–3 cm long (rarely up to 4.5–5 cm) with a maximum width of the segment 0.7–0.9 mm. Like all cestodes, it has a head (scolex), neck and segmented strobila.
The globular or somewhat elongated scolex is armed with four suckers and a short retractable proboscis with one row of chitinous hooks, the number of which varies from 20 to 24 – 30. Thin neck – the growth zone turns into a ribbon-like body (strobila) of the parasite, consisting of segments (proglottids), the number of which amounts to 200 – 300.
Genital system hermaphroditic type. In the immature segments, 3 globular testicles are clearly expressed. The ovary is located between the testes in the form of a dense elongated formation, which is adjacent to the zheltochnik blade. Genital openings open on one side of the strobila in each segment.
In mature segments, only the uterus filled with eggs is preserved; 140 to 180 eggs are contained in each segment.
Although the dwarf tapeworm, like other members of the Cyclophyllidea order, has a closed uterus, it, like the mature segment itself, is so tender that already separated mature segments in the intestine are destroyed and therefore the helminth eggs are constantly excreted with the fecal masses of the infested.
Eggs have an ellipsoid-spherical shape, they are transparent, colorless, slightly opalescent, 36 – 43 x 45 – 53 microns in size. Inside the egg there is an oncosphere of size 25 – 29 x 18 – 20 microns with three pairs of germinal hooks. From the poles of the oncosphere depart thin filaments refracting light – filaments holding the oncosphere in the center of the egg. Mature eggs are found from the 98th to the 100th segment.
Pathogenesis during Hymenolepidosis
The life cycle of the pathogen.
The biology of the dwarf chain is rather peculiar, because the development of helminth occurs in the organism of one host, which first serves as an intermediate host for the parasite, and then becomes final. However, the possibility of the development of helminths and with the participation of an intermediate host in the quality of some insects – fleas and meal beetles is not excluded.
The main owner of the dwarf chain is man.
A person becomes infected by ingesting N. nana eggs, which pass through the stomach and enter the upper small intestine. Here the oncosphere is actively released from the egg by the active movements of embryonic hooks and is embedded in the villus or in the thickness of the solitary follicle of the lower third of the small intestine, where the invasion tissue phase occurs when man is an intermediate owner. Passing successive stages of development (megalospheres, metamers), the oncosphere in 6-8 days turns into a cysticcercoid. Cysticercoids can also develop in lymphoid follicles, i.e., where the oncospheres penetrate, as well as in other organs: the liver, mesenteric lymph nodes. After 5-8 days, as a result of the destruction of the villi, cysticercoids fall into the intestinal lumen. It is impossible to exclude the possible active release of cysticercoids from the villi. This ends the tissue phase of development and begins intestinal, when a person is the final host for the helminth. Cysticercoid, having a finished scolex, is fixed to the mucosa of the small intestine with the help of suckers and hooks. The process of strobilization begins, which lasts on average up to 2 weeks. Thus, the formation of an adult individual from the moment of infection is completed in 3 weeks.
The duration of the parasitization of a single generation of dwarf chains does not exceed 2 months.
However, with hymenolepiasis, it is possible to re-infection both from the outside as a result of re-swallowing eggs, and due to intraintestinal autosuperinase. This is the cause of prolonged and intense invasions.
Autosuperinvaziya – the process of intra-intestinal invasion of the villi by oncospheres, released from eggs, released into the lumen of the intestine with the destruction of mature segments. It is observed in 10 – 17.5% of experimental animals, most often weakened, aggravated by other infections, ectoparasites, and also on a deficient diet with vitamin deficiencies, etc. An important factor determining the likelihood and frequency of repeated infections is superinvasive immunity, the intensity of which varies over a wide range and depends on many factors (age, intensity of primary infection, comorbidities, constitutional features, etc.). In some cases (mostly with age) spontaneous self-release from invasion is observed.
In addition to the villi, cysticercoids can develop in other organs and tissues – in the liver, solitary intestinal follicles, in the mesenteric lymph nodes, which was established in experimental animals. However, in these tissues, the larvae do not further develop and, being preserved, may be the cause of chronic allergies associated with the hymenolepiasis described by B. A. Astafyev in children who died suddenly from traumatic brain injuries.
The invasive eggs of H. nana enter the human body by oral route. In the development of helminth there are two phases: tissue and intestinal. During tissue oncosphere, and then cysticercoid, the villi and the intestines are destroyed. Adults when they are fixed with suckers, rubbed with a ribbed strobila cause mechanical damage. Irritation of the nerve receptors of the mucous membrane of the small intestine leads to the appearance of viscero-visceral pathological reflexes, and then to dysfunction of the stomach, liver and other organs. As a result of damage to the mucous membrane, inoculation of the secondary microbial flora in the small intestine, inflammation develops, enzymatic processes are disturbed, and dysbacteriosis develops, which is 4.5 times more often registered in children invaded by N. paаa.
In the pathogenesis of tissue, and then in the intestinal phase of invasion, allergen-toxic effects of the waste products of the larvae, sexually mature helminths, and also the decay products of the host tissues matter. The manifestations of chronic allergies include eosinophilia, allergic skin rashes, and asthmoid states, confirmed by pathological changes in the organs of H. nana infested people who died suddenly from other causes.
Symptoms of Hymenolepidosis
The clinical picture of hymenolepiasis varies greatly, differing both in the presence or predominance of certain symptoms and in the degree of their severity. In 1/3 of the patients subclinical course of invasion is noted.
By the nature of the symptomatology, 3 syndromes are distinguished: pain, dyspeptic and asthenoneurotic, since the digestive and nervous systems are primarily affected.
The main complaints of patients: abdominal pain, loss of appetite, nausea, unstable chair, malaise, weakness, fatigue, irritability, headache.
Intensive invasions, as a rule, more severe manifestations occur: severe paroxysmal abdominal pain, frequent vomiting, dizziness, seizures, fainting, memory loss, low-grade fever, insomnia, etc. general asthenia, mild anemia, eosinophilia.
In children who often suffer from hymenolepiasis, weight loss, convulsions without loss of consciousness, more pronounced anemia, leukopenia, lymphocytosis, monocytopenia join the main complaints of loss of appetite, thirst, memory loss.
Diagnosis of Hymenolepidosis
Diagnosis of hymenolepiasis is based on the detection of eggs in the feces. The effectiveness of the main coprological methods of Kalantaryan, Fulleborn and Kato (with the study of three strokes of 50 mg) is about the same, but the latter is simpler.
Due to the cyclical release of eggs, depending on the intensity of invasion, the most effective 3-fold study with an interval of 5 days (92 -100% detection).
The preliminary (on the eve) prescription of fenasal (0.5 -1.0) followed by the administration of purgen increases the detectability by 40 – 47%.
Treatment of Hymenolepidosis
For deworming (expelling worms) used Fenasal. The drug is prescribed in a daily dose: adults 2-3g (8-12 tablets); for children under 2 years old 0.5 g (2 tablets), from 2 to 5 years 1 g (4 tablets), from 5 to 12 years 1.5 g (6 tablets) over 12 years 2 – 3 g (8 – 12 tablets). The daily dose of fenasal is divided into 4 doses and taken every 2 hours (10, 12, 14 and 16 hours). Food is taken at 8, 13 and 18 h. Fenasal is taken for 4 days, then a break of 4-7 days is taken. After the break, repeat the treatment. A control study of feces is carried out 15 days after the end of treatment and subsequently monthly.
On the eve and on the days of treatment, a slab-free diet with restriction of coarse food rich in fiber is recommended. During treatment and 3-4 days after it is over, the patient should take a shower and change clothes every day.
One month after the main course, one cycle of anti-relapse treatment is performed. In the intervals between de-worming cycles, there is a fortifying treatment – taking multivitamin preparations.
Prevention of Hymenolepidosis
The fight against hymenolepiasis includes a complex of treatment-and-prophylactic and sanitary-hygienic measures. Therapeutic and prophylactic measures are aimed at identifying and neutralizing the source of invasion. These include:
- identification of infested, which is carried out by a coprological examination of children and staff of preschool childcare institutions, students in grades 0-4 – once a year; catering workers and equivalent groups visiting swimming pools – upon admission; inpatients (children’s hospitals, infectious diseases, gastroenterological departments) upon admission and for clinical reasons; survey of contact with the definition of its volume, multiplicity and timing of the recommendations of the Sanitary and Epidemiological Service;
- rehabilitation of all identified invasions with suspension for the period of treatment from attending preschool institutions, schools; from work – persons employed in catering;
- dispensary observation.
The rupture of the transmission mechanism is provided by a complex of sanitary and hygienic measures. An important place among them is occupied by such careful conduct of wet cleaning of premises, disinfection of bedding of household items, toys, night pots, door handles of taps of washbasins, etc. using boiling water, hot iron, soap and cresol mixture, etc.
In the complex of sanitary and hygienic preventive measures, an important place belongs to the hygienic training of children (as well as parents) and the inculcation of hygienic skills in them: washing hands before eating, after using the toilet, removing the habit of nail biting, taking fingers, toys, pencils in the mouth, etc.