Trichinosis is an acute infection caused by roundworms. Characteristic symptoms are a variety of allergic reactions and severe muscle pain. Edematous syndrome and fever are often observed. Diagnosis of trichinosis includes serological techniques and detection of the pathogen in biopsies of the affected muscle tissue. Etiotropic methods of treatment involve the use of anthelmintic drugs, symptomatic therapy should be aimed at relieving allergic reactions and edema, detoxification, correction of protein and electrolyte disorders.
ICD 10
B75 Trichinosis
General information
Trichinosis has been known since ancient times, but the pathogen itself was first described in 1835 by English student Paget and pathologist Owen. The mechanism of infection was first characterized in 1846 by the American biologist Leidy. Helminthiasis is widespread everywhere except Australia, especially in pig-breeding areas. Risk groups are veterinarians, pig breeders, hunters, slaughterhouse and meat processing plant workers, cooks, middle-aged men and women. The seasonality of the disease is year-round, there is an increase in the number of cases in the winter-autumn period, which may correlate with the slaughter of livestock and hunting.
Causes
The causative agent of the disease is the roundworm Trichinella, the most common species are T. spiralis, T. nativa, T. nelson, T. pseudospiralis. The life cycle of the parasite does not imply the presence of a human body, so people for trichinella are a biological dead end. The source of infection are pigs, wild boars, rats, moose, seals, bears, belugas and other animals (more than 100 species have been described). A feature of the helminth development is the use of a single host as both intermediate and permanent.
The path of infection is alimentary, associated with the consumption of raw, poorly cooked or fried, smoked and salted meat, lard. Circulation in nature is provided by predator-prey relationships, scavengers, rodents eating infected meat is common among households, pigs, in turn, can eat the corpses of rats. Mature individuals of trichinella live in the intestine, the larvae are encapsulated in the muscles, being transported there through the bloodstream system.
Pathogenesis
When trichinella larvae that are in infected meat enter the human intestine, they are released from the shell and ripen to the size of adults. There is a dependence of the survival rate of trapped larvae on their age and the characteristics of the intestinal microflora. Helminths are viviparous, so larvae that hatch up to several thousand per day can almost immediately penetrate through the intestinal wall into the mesenteric lymph nodes, then into the systemic bloodstream and spread throughout the body.
The favorite localization is striated muscles (except for the heart), which may be due to their abundant blood supply. Inside the muscle, the larva is covered with a capsule after 4-8 weeks and within six months after ingestion begins to calcify, becoming completely calcified after 5-7 years from the moment of infection and maintaining viability for a decade. The most frequent places of accumulation are the legs of the diaphragm and the tongue. In other organs, the larvae die.
Trichinosis symptoms
The incubation period averages 10-15 days, can decrease to five and increase to 60 days. The disease begins acutely against the background of full health with chills, insomnia, body aches, weakness, hallucinations, an increase in body temperature to 39 ° C or more, or subfebrility (no higher than 38 ° C), persisting for more than one month. Patients may have signs of digestive tract disorders: loose stools, vomiting, nausea. In the first week of the disease, swelling of the face and eyelids, conjunctivitis are noted; in severe cases, the swelling descends lower. On the skin of patients with trichinosis, rashes in the form of itchy spots and bumps are often found, hemorrhages are less often visible.
Muscle pains increase in proportion to fever, starting from the lower extremities and reaching the intercostal, masticatory, oculomotor and other muscles. In addition to myalgia, progressive myasthenia gravis occurs, which is regarded as a life-threatening condition, since when the respiratory muscles are affected, it can cause the inability to breathe independently. Patients often cannot find a comfortable position, movement is limited by bed, eating and drinking water is almost impossible without assistance. When the respiratory tract is affected, there is a cough with sputum, sometimes hemoptysis.
Complications
The main complications of trichinosis, usually occurring within 3-5 weeks of the disease, are myocarditis, pneumonia and abdominal syndrome, less often meningoencephalitis. The lesions are associated with the pathological effect of trichinella and their waste products on the walls of blood vessels, which leads to nonspecific vasculitis, the formation of widespread granulomatosis in the brain and spinal cord. The consequence of these processes can be acute cardiac and respiratory failure, paralysis, paresis, thrombohemorrhagic syndrome, infectious and toxic shock and increasing encephalopathy.
Diagnostics
The diagnosis of trichinosis is carried out during the consultation of an infectious disease specialist. In some cases, an examination by a therapist, dermatologist and other specialists is indicated. The most common diagnostic methods for confirming trichinosis are the following instrumental and laboratory tests:
- Physical examination. During an objective examination, facial edema, paraorbital fiber, conjunctival hyperemia, maculopapular rash on the body attract attention. Patients hardly make arbitrary movements, sometimes muscle contractures are formed. Dry diffuse wheezing may be heard in the lungs during auscultation. Half of the patients have hepatomegaly.
- Laboratory tests. One of the leading signs of trichinosis is leukocytosis and eosinophilia (20-60%) in the blood test with maximum values at 2-4 weeks of illness. Biochemical parameters are distinguished by an increase in ALT and AST activity, hypergammaglobulinemia, a decrease in total protein and electrolytes of hypoalbuminemia. Charcot-Leyden crystals can be found in sputum.
- Identification of infectious agents. Serological diagnostics (ELISA) becomes informative from the 3rd week of the disease, studies in paired serums with an interval of 10-14 days are required. The diagnostic titer is considered to be 1:100 or more. In rare cases, no earlier than 9-10 days of the disease, microscopy of muscle tissue biopsies is performed, in which pathogens are detected.
- Instrumental techniques. Ultrasound examination of joints, soft tissues and abdominal organs is recommended for the purpose of differential diagnosis. ECG, ECHO-CS in patients with trichinosis is necessary to exclude myocarditis. Chest radiography is prescribed according to indications, in case of lung damage, “volatile” infiltrates can be determined.
Differential diagnosis of trichinosis is carried out with leptospirosis, which is characterized mainly by jaundice and bleeding. Pathology is also differentiated with hemorrhagic fever with renal syndrome, typical symptoms of which are dysuric phenomena on the background of hemorrhages; ascariasis, in the clinic of which a combination of gastrointestinal and respiratory tract lesions is often found; visceral toxocarosis occurring with lymphadenopathy; Quincke’s edema and edema with renal insufficiency.
Trichinosis treatment
Patients with moderate and severe forms of the disease need inpatient treatment. With increasing signs of respiratory failure, manifestations of myocarditis, patients are in the intensive care unit. Bed rest is recommended for up to 3-4 days of absence of elevated body temperature with relieved pain syndrome. Nutrition of patients with trichinosis has no specific restrictions, it is recommended to adhere to a sparing diet with a sufficient amount of protein. The water regime is subject to correction associated with edematous syndrome, the exclusion of alcohol, carbonated drinks, coffee, tea is required.
Etiotropic drugs (albendazole, mebendazole, tiabendazole) are necessarily included in the treatment regimen of trichinosis. Symptomatic treatment is aimed at relieving edematous (furosemide, dichlotiazide), and allergic (indomethacin, desloratadine) components of the disease, detoxification (chlosol, glucose-salt solutions), desensitization (chloride, calcium gluconate). According to the indications, hormonal agents (prednisone, dexamethasone) are used, hypoproteinemia is corrected (albumin, freshly frozen plasma). The possibility of using rituximab as an alternative to glucocorticosteroids is being investigated.
Prognosis and prevention
The prognosis for mild and moderate course is favorable. Recovery occurs in 5-6 weeks, the average mortality rate does not exceed 5%. In severe forms, prolonged convalescence is possible (for 6 months) with residual asthenization, myalgia, and persistent muscle contractures. The use of glucocorticosteroids disrupts the formation of capsules in larvae, therefore, with their long intake, a prolonged course and relapses of the disease are possible.
A vaccine against trichinosis is currently not developed. Prevention consists in strict sanitary and veterinary control of meat products from pork and other types of meat, trichinelloscopy at meat processing plants and slaughterhouses. Careful temperature treatment of meat is mandatory, it is necessary to avoid eating raw meat of wild animals and pigs. It is impossible to feed offal from slaughterhouses to predators, to bury animal carcasses after skinning.