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Trichinellosis - Overview
Last reviewed: 05.07.2025
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Trichinellosis (Latin: trichinellosis) is a helminthiasis caused by nematodes of the genus Trichinella that parasitize the human body. It is characterized by an acute course, fever, muscle pain, edema, high eosinophilia and various allergic manifestations.
ICD-10 code
B75. Trichinellosis.
Epidemiology of trichinosis
The source of the infectious agent for humans are domestic and wild animals infected with trichinella. The mechanism of infection is oral. A person becomes infected by eating meat infested with trichinella: more often pork, less often the meat of wild animals (bear, wild boar, badger, walrus, etc.).
Trichinellosis is a natural focal biohelminthiasis. In many cases, it is impossible to draw clear boundaries between natural and synanthropic foci, since the pathogen can be exchanged between wild and domestic animals. More than 100 mammal species are known to be hosts of Trichinella. The pathogen circulates between predators (brown and polar bears, canines, cats, mustelids), facultative carnivorous ungulates (wild boar, reindeer, elk) and rodents (rats, voles, lemmings, etc.). Infection of pinnipeds (walrus, seal) and cetaceans (beluga whale) is also possible. Trichinella circulation in nature is carried out mainly through predation and eating carrion. Encapsulated Trichinella larvae remain viable and infectious for 4 months after the complete decomposition of the infected animal's body.
Synanthropic foci are secondary. The circulation of the pathogen in them usually follows the chain "domestic pig-rat-domestic pig". Humans do not participate in the circulation of trichinella, since they become a biological dead end in the helminth's development cycle. Trichinellosis is often a group disease.
The distribution area of trichinellosis among humans corresponds to that among animals. In nature, trichinellosis is recorded everywhere among mammals, with the exception of Australia. The incidence of humans varies significantly by region of the world. In Russia, synanthropic trichinellosis is common in the moderate northern, moderate and southern zones, in the south of the Far East, and Kamchatka. The main areas of trichinellosis, where infection is associated with the consumption of wild animal meat, are the Magadan and Kamchatka regions, Krasnoyarsk Krai, the Sakha Republic and Khabarovsk Krai. Mixed-type foci with the circulation of the pathogen between synanthropic (pig, cat, dog) and wild (boar, bear, rodents) animals are found in the North Caucasus.
[ What causes trichinosis?
Trichinellosis is caused by roundworms of the Trichinellidae family, which includes two species - Trichinella spiralis with three varieties (T. s. spiralis, T. s. nativa, T. s. nelsoni) and Trichinella pseudospiralis. In the pathology of the population of Ukraine, T. s. spiralis and G. s. nativa are of greatest importance. Trichinella s. spiralis is widespread, parasitizes domestic pigs, and is pathogenic for humans. Trichinella s. nativa is found in the northern hemisphere, parasitizes wild mammals, is extremely resistant to cold, and is pathogenic for humans. Trichinella s. nelsoni lives in Equatorial Africa, parasitizes wild mammals. is low pathogenic for humans. Trichinella pseudospiralis is widespread, parasitizes birds and wild mammals. Pathogenicity for humans has not been proven.
Trichinella are small nematodes with a cylindrical colorless body covered with a transparent ringed cuticle. The length of an unfertilized female is 1.5-1.8 mm, fertilized - up to 4.4 mm, sexually mature male - 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 form, up to 10 mm in length; after 18-20 days of development, the larva lengthens to 0.7-1.0 mm.
Pathogenesis of trichinosis
The pathogenesis of trichinellosis is based on the sensitization of the organism to helminth antigens, which manifests itself to varying degrees in the intestinal, migratory and muscular stages of invasion. By the end of the first week after infection, female trichinella are found mainly in the small intestine, immersed in the mucous membrane, around which a local catarrhal-hemorrhagic inflammatory reaction develops. In severe invasion, ulcerative-necrotic damage to the intestinal mucosa is observed. Adult helminths secrete immunosuppressive substances that suppress the violent inflammatory reaction, which promotes 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 with sensitizing, enzymatic and toxic properties. As a result, severe allergic reactions develop with damage to blood vessels, coagulation disorders, tissue edema, and increased secretory activity of the mucous membranes.
What are the symptoms of trichinosis?
Trichinellosis has an incubation period of 10-25 days, but sometimes it can be from 5-8 days to 6 weeks. When infected in synanthropic foci (after eating infected meat of domestic pigs), there is an inverse relationship between the duration of the incubation period and the severity of the disease: the shorter the incubation period, the more severe the symptoms of trichinellosis, and vice versa. When infected in natural foci, such a pattern is usually not observed.
Depending on the nature of the clinical course, trichinellosis 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 trichinellosis does not cause difficulties.
It is necessary to establish a common source of infection and, if possible, to examine food remains (meat or meat products) for the presence of trichinella larvae. Difficulties arise in diagnosing sporadic cases. In such situations, the epidemiological anamnesis is of great importance.
In the absence of data on the source of infection, a muscle biopsy is sometimes used (deltoid or gastrocnemius in bedridden patients or long back muscle in ambulatory patients): a piece of muscle tissue weighing 1 g is examined under a microscope at low 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 trichinellosis is aimed at destroying intestinal trichinella, stopping the production of larvae, disrupting the encapsulation process and increasing the death rate of muscle trichinella. Trichinellosis is treated with albendazole and mebendazole.
Albendazole is prescribed orally after meals at 400 mg twice a day for patients weighing 60 kg or more, or at 15 mg/kg per day in two doses for patients weighing less than 60 kg. The duration of treatment is 14 days.
What is the prognosis for trichinosis?
Trichinellosis has a favorable prognosis in mild and moderate forms of invasion. A short-term resumption of some clinical manifestations is possible: myalgia, moderate edema, eosinophilia in blood tests. In severe forms with complications, trichinellosis has a serious prognosis: with late diagnosis and delayed antiparasitic treatment, a fatal outcome is possible: in the case of a malignant course, it can occur already in the first days of the disease.