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Trichinosis - Overview
Last reviewed: 23.04.2024
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Trichinellosis (Latin trichinellosis) is helminthiasis caused by parasitizing nematodes of the genus Trichinella in the human body. Characterized by acute course, fever, pain in the muscles, edema, high eosinophilia and various allergic manifestations.
ICD-10 code
Q75. Trichinosis.
Epidemiology of trichinosis
The source of the causative agent of infection for humans are domesticated and wild animals affected by Trichinella. The mechanism of infection is oral. A person becomes infected when eating meat contaminated with trichinella: more pork, less meat of wild animals (bear, wild boar, badger, walrus, etc.).
Trichinosis is a natural focal biogelmintosis. Clear boundaries between natural and synanthropic foci in many cases can not be carried out, since it is possible to exchange pathogens between wild and domestic animals. There are more than 100 species of mammals known to be hosts of Trichinella. The causative agent circulates between carnivores (brown and polar bears, dogs, cats, cunyas), facultative carnivorous animals (boar, reindeer, elk) and rodents (rats, voles, lemmings, etc.). It is also possible to infect pinnipeds (walrus, seal) and cetaceans (beluga). Circulation of trichinella in nature is mainly through predation and eating of carrion. Encapsulated larvae of Trichinella show viability and infectiousness within 4 months after complete decomposition of the corpse of the invaded animal.
The synanthropic foci are secondary. Circulation of the pathogen in them usually goes along the chain "domestic pig-rat-domestic pig". In the circulation of trichinella, a person does not participate, since in the cycle of helminth development becomes a biological dead end. The incidence of trichinosis is often of a group nature.
The distribution of trichinosis among humans corresponds to that of animals. In nature, among mammals, trichinosis is recorded everywhere, except for Australia. The incidence of human beings varies considerably by region. In Russia, synanthropic trichinosis is common in temperate northern, temperate and southern zones, in the south of the Far East, and in Kamchatka. The main areas of trichinosis, where the infection is associated with the consumption of meat of wild animals, are Magadan, Kamchatka, Krasnoyarsk, Sakha and Khabarovsk. Foci of mixed type with the circulation of the pathogen between the synanthropic (pig, cat, dog) and wild (boar, bear, rodents) animals are found in the North Caucasus.
[What causes trichinosis?
Trichinosis is caused by round worms of the family Trichinellidae, which includes two species - Trichinella spiralis with three varieties (T. Spiralis, T. S. Nativa, T. S. Nelsoni) and Trichinella pseudospiralis. In the pathology of the population of Ukraine, the most important are the T. S. Spiralis and G. S. Nativa. Trichinella s. Spiralis is ubiquitous, parasitic in domestic pigs, pathogenic to humans. Trichinella s. Nativa occurs in the northern hemisphere, parasitizes wild mammals, is extremely resistant to cold, pathogenic to humans. Trichinella s. Nelsoni lives in Equatorial Africa, parasitizes wild mammals. Slightly pathogenic for humans. Trichinella pseudospiralis is ubiquitous, parasitic in birds and wild mammals. Pathogenicity for humans is not proven.
Trichinella - small nematodes with a cylindrical colorless body, covered with a transparent cuticle of a ringed structure. The length of the unfertilized female is 1.5-1.8 mm, fertilized - up to 4.4 mm, the mature male is about 1.2-2 mm, the diameter of the helminths is less than 0.5 mm. Unlike other nematodes, trichinella are viviparous helminths. Their larvae, young Trichinella, have a rod-shaped shape, length up to OD mm; After 18-20 days of development, the larva lengthens to 0.7-1.0 mm.
Pathogenesis of trichinosis
At the heart of the pathogenesis of trichinosis is the sensitization of the organism to helminth antigens, manifested in varying degrees in the intestinal, migratory and muscular stages of invasion. By the end of the first week after infection, predominantly in the small intestine, females of Trichinella, immersed in the mucosa, are found around which a local catarrhal-hemorrhagic inflammatory reaction develops. In severe invasion, ulcerative necrotic lesions of the intestinal mucosa are observed. Adult individuals of the helminth isolate immunosuppressive substances that suppress a violent inflammatory reaction, which facilitates the migration of larvae. In the jejunum the kinin system is activated. Other hormones that cause functional disorders, pain syndrome. Metabolites of migrating larvae, products released after their death, are antigens that have sensitizing, enzymatic and toxic properties. As a result, severe allergic reactions develop with blood vessel damage, coagulation disorders, tissue edema, increased secretory activity of the mucous membranes.
What are the symptoms of trichinosis?
Trichinosis has an incubation period that lasts 10-25 days, but sometimes it can range from 5-8 days to 6 weeks. When infected in synanthropic foci (after consuming infected meat from domestic pigs), there is an inverse relationship between the duration of the incubation period and the severity of the course of the disease: the shorter the incubation period, the heavier the symptoms of trichinosis, and vice versa. When infecting in natural foci, this pattern is usually not noted.
Depending on the nature of the clinical course, trichinosis has the following forms: asymptomatic, abortive, mild, moderate and severe.
How is trichinosis diagnosed?
During outbreaks and group diseases in the presence of typical symptoms in patients, the diagnosis of "trichinosis" does not cause difficulties.
It is necessary to establish a common source of infection and, if possible, to conduct a study of food residues (meat or meat products) for the presence of Trichinella larvae. Difficulties arise in the diagnosis of sporadic cases. In such situations, a significant epidemiological history.
In the absence of data on the source of infection, sometimes muscle biopsy (deltoid or gastrocnemius in bedridden patients or long back muscles in walking patients) is sometimes used: a piece of muscle tissue weighing 1 g is examined under a microscope at a small magnification for the presence of Trichinella larvae.
What do need to examine?
How to examine?
What tests are needed?
How is trichinosis treated?
Antiparasitic treatment of trichinosis is aimed at destruction of intestinal trichinella, suppression of larvae production, violation of encapsulation process and growth of death of muscle trichinella. Trichinosis is treated with albendazole and mebendazole.
Albendazole is prescribed inside after meals 400 mg twice a day for patients with a body weight of 60 kg or more or 15 mg / kg per day in two doses to patients with a body weight of less than 60 kg. Duration of treatment is 14 days.
What is the prognosis of trichinosis?
Trichinosis has a favorable prognosis with a mild and moderate form of invasion. Perhaps a brief resumption of certain clinical manifestations: myalgia, moderate edema, eosinophilia in blood tests. In severe form with complications, trichinosis has a serious prognosis: with late diagnosis and delayed antiparasitic treatment, a lethal outcome is possible: in malignant course it can occur already in the first days of the disease.