Trichinosis in humans

Trichinellosis – one of the varieties of helminthiasis. The disease is caused by ingestion of a small parasite belonging to the class of nematodes. Sexually mature Trichinella lays its larvae in the human intestine, and after that, the larvae enter the muscles with blood flow, and remain there in a dormant state. At 3-4 weeks from the onset of infection, the larvae develop and become covered with a capsule. The causative agent of the disease is a round worm up to 0,5 mm long, taking the form of a spiral.

The prevalence of trichinosis

Trichinosis in humans belongs to the category of biohelminthiasis, as it is caused by parasitic worms – Trichinella. The disease is diagnosed in both animals and humans. The main types of animals most often affected by trichinosis are: wolf, fox, bear, badger, wild boar. Domestic pigs are also susceptible to this type of helminthiasis. This usually happens when pigs are free-grazing, when it becomes available for them to eat the meat of dead animals and small rodents.

Reasons for the prevalence of trichinosis:

• The good adaptability of the pathogen to high and low temperatures provided him with living in many climatic zones;

• The human body is extremely susceptible to this disease;

• Group outbreaks of helminthiasis are not uncommon among members of the same team or one family who have consumed meat with Trichinella;

• Repeated cases of infection occur due to unstable immunity formed after the initial invasion.

Trichinella mutate, new forms of nematodes appear that do not form a capsule, as well as species that parasitize birds.

Methods of infection with trichinosis

Trichinella enters the human body by mouth, when eating infected meat. Parasites in meat die during heat treatment, so undercooked, cured and raw meat carries the main risk. Infected pork, seal meat, bear meat, and wild boar meat are especially dangerous.

The development of trichinosis in the human body after infection:

The first signs and symptoms of trichinosis

Trichinosis in humans does not cause visible physical harm to the body. There are no changes in muscle tissue. Harm to health is caused by the proteins that make up the body of the parasite. They are very powerful allergens, foreign substances. The strongest allergic reaction caused by them leads to damage to blood vessels and joints.

The incubation period of trichinosis. It lasts from 5 to 30 days, more often – 10-25 days. There are no symptoms of the disease. There is a pattern – the more severe the form of helminthiasis, the longer the latent (hidden) period.

Period in full swing. A long period of symptom development indicates the development of a severe form of trichinosis.

Mild and moderate form – symptoms:

• Hyperthermia. The temperature rises slightly, more than 37°C, the daily amplitude varies within 1°C.

• Swelling on the body and limbs. Its cause is an allergic reaction to the introduction of a foreign protein. A characteristic symptom is the “frog face” of the patient.

• Muscular pains in the upper and lower extremities, muscles of the back, neck, eyes, pharynx, peritoneum. Intense pains begin in the calf muscles, affect the cervical and chewing. The pain is aggravated by palpation and movement. They can begin to disturb the patient from 1-3 days of the introduction of the parasite into the body. The early appearance of muscle pain is a sign of a severe form of trichinosis.

Rash on the skin. It has different forms:

1. In the form of allergic urticaria – pink blisters of various sizes, turning pale when pressed;

2. Itchy blisters raised above the surface of the skin (urticaria);

3. Groups of plaques merging with each other (papular rash).

Complications in severe forms of trichinosis:

• Meningoencephalitis is an inflammation of the lining of the brain.

• Inflammation of the lungs (eosinophilic pneumonia). The disease is caused by an increased concentration in the lung tissue of eosinophils – products of an allergic reaction. Perhaps the development of pleurisy, the appearance of symptoms of bronchial asthma.

• Myocarditis is inflammation of the myocardium due to allergies and an overreaction of the immune system. More often than other complications becomes the cause of death of patients.

• Nephritis is inflammation of the kidney tissue.

• Hepatitis is inflammation of the liver.

• Intense pain sensations in the muscles lead to partial or complete impairment of mobility.

Mortality in severe form of the disease is 10-30% of the total number of patients. The most frequent period of occurrence of deaths is 4-8 weeks from the onset of infection. With milder forms, after 5-6 weeks, patients recover.

Symptoms of trichinosis depending on the stage of the disease

The manifestation of trichinosis at an early stage of the lesion depends on the concentration of parasites in the body. Further development of the disease depends on the spread of larvae in the muscles and the state of the patient’s immune system. The most severe complications of helminthiasis are associated with an inadequate response of the body to the introduction of a foreign protein into the body, and not to the activity of Trichinella and their larvae.

Symptoms of trichinosis in humans can be similar to manifestations of myositis, allergies, and infectious diseases. This picture leads to the fact that the patient is unaware of the appearance of helminthiasis in him.

Symptoms of trichinosis in children

To infect a child, it is enough to eat a small piece of meat with trichinella weighing 10-15 g, which has not undergone a full heat treatment. The latent period lasts from 5 to 45 days. The shorter this period, the more severe the disease in the child.

1. Symptoms at an early stage. It lasts 7-14 days, after recovery, minor symptoms are noted for 7-10 days.

   • Hyperthermia up to 38,5°C:

   • Slight puffiness of the face;

   • mild muscle pain;

   • Edema of the eyelids;

   • An increase in the concentration of eosinophils by 10-12%.

2. Symptoms are in the moderate stage. The acute period lasts up to 3 weeks, rehabilitation – 2-3 weeks after recovery.

   • Hyperthermia up to 40°C, antipyretic drugs reduce it by no more than 1°C;

   • Pain in the muscles, joints, abdomen and throat;

   • Skin rash;

   • swelling of the face;

   • The results of a general blood test: ESR increased (above 17 mm/h), leukocytes increased (up to 8,8 10⁹/l), the concentration of eosinophils increased to 25-40%.

3. Symptoms are at a severe stage. It is treated in the infectious diseases department of the hospital, without therapy the child may die.

   • Hyperthermia up to 41°C;

   • Enlargement of the liver and spleen;

   • CNS disorders: delirium, agitation, epileptic seizures;

   • Attacks of severe pain in the abdomen;

   • diarrhea, nausea, vomiting;

   • Severe muscle pain, complicated by convulsions;

   • Subcutaneous hemorrhages and rash;

   • Indicators of the general blood test: Leukocytes up to 30-40×10⁹/l; ESR up to 50-60 mm/h; concentration of eosinophils up to 80 – 90%;

   • Cylinders and proteins in the urine.

Treatment of trichinosis in children is carried out with anthelmintic drugs (Thiabendazole, Vermox) in accordance with the body weight and age of the child.

Drugs for the symptomatic treatment of trichinosis:

• Ibuprofen, Paracetamol – to reduce fever, relieve pain;

• Tsetrin, Loratadin – antihistamines to reduce intoxication and allergy manifestations;

• Papaverine, No-shpa – antispasmodics to reduce pain;

• Vitamins of groups C and B to improve immunity.

Rehabilitation after a disease is carried out with the help of massage sessions, baths with sea salt and medicinal herbs, a complex of therapeutic exercises.

Diagnosis of trichinellosis

General blood analysis. With trichinosis in humans, the content of eosinophils, a type of leukocyte, increases significantly in the blood. The concentration of white blood cells most often increases with severe allergic reactions, including allergies that accompany trichinosis.

Changes in the composition of the blood, diagnosed with trichinosis:

• The number of eosinophils reaches from 50 to 80% of the total number of leukocytes;

• An increase in the concentration of leukocytes is a sign of the activation of immunity and the presence of an inflammatory process in the body.

These symptoms appear immediately after infection, persist 2-3 months after recovery.

Serological diagnosis. An analysis of the reaction of blood to the attachment of antigens obtained from nematode larvae is carried out. Antibodies to them are formed as a reaction to the introduction of helminths.

Types of serological diagnostics:

Intravenous allergy test. It is carried out to provoke an allergic reaction in response to the introduction of a trichinosis antigen. A portion of the antigen solution is injected under the skin. The presence of the disease is diagnosed by the appearance of hyperemia and redness at the injection site. This method can diagnose trichinosis as early as 2 weeks of nematode infection. A positive result of an allergic test persists for 5-10 years.

Muscle biopsy. It is carried out in the absence of a positive result from other research methods. Under a microscope, the biomaterial obtained with a needle from the patient’s muscle is studied.

Study of the meat of sick animals. With a multiple increase, the meat of the animal, the alleged source of infection, is examined. Using a microscope, capsules with larvae are found in the tissues of a sick animal.

Treatment of trichinellosis

Anthelmintic drugs (treatment aimed at combating the causative agent of the disease):

• during the first three days; 100 mg 3 times a day;

• next 10 days; 500 mg 3 times a day.

Children under 7 years old: 25 mg of the drug 3 times a day. Children aged 7; 9 years: 3 times a day, 50 mg. Older than 10 years:

• during the first three days; 100 mg 2-3 times a day;

• then for 10 days, 500 mg 3 times a day.

Take after meals. (;Complete reference book of an infectious disease specialist; edited by DMN, prof., corresponding member of RAE and REA Eliseeva Yu.Yu.,; Eksmo;, 2007)

Treatment of symptoms of trichinosis

The high probability of death, the frequent transition of the disease to a severe form, a large number of complications are good reasons for treating trichinosis exclusively in a hospital setting. Despite this, from 10 to 30% of cases are fatal.

For patients who have received severe muscle damage, careful care is needed, as the patients are completely immobilized and bedridden. To restore mobility, patients are rehabilitated using massage and physiotherapy methods.

Symptomatic treatment of trichinosis in humans is supplemented with vitamin therapy, drugs to stimulate blood circulation, to protect the liver and brain (if these organs are affected).

Prevention of trichinellosis

Measures to prevent trichinosis:

• Meat (especially pork) must be cooked at a high temperature – at least 74°C inside the piece of meat for at least 15 seconds. Under such conditions, Trichinella larvae will surely die if they have not yet become covered with a calcified capsule. Otherwise, the larvae will not suffer even with such heating. The larvae have time to become covered with a capsule during a long course of the disease in an animal – a carrier of Trichinella.

• An effective way to kill Trichinella is freezing for 20 days at -15°C, or holding for three days at -20°C.

• When breeding pigs, they should not be allowed to freely graze to prevent animals from eating infected carrion. It is necessary to regularly destroy rats in the place of residence of animals and in the courtyard of the farm.

• Especially dangerous is the consumption of meat of wild animals infected with trichinosis. The species of nematodes that parasitize in the muscles of bears, badgers and seals differ markedly from Trichinella pigs. They do not die even with prolonged freezing. Long-term thermal culinary treatment of such meat is required. The meat of wild birds can also be dangerous in this regard.

Mass measures to prevent outbreaks of trichinosis

Rospotrebnadzor conducts systematic monitoring of the conditions of keeping animals intended for breeding for meat. The sale of meat is not carried out without testing it for trichinosis. Such control is carried out in the market and in specialized stores. The safety of meat sold in places of spontaneous trade is not guaranteed.

How to test meat for trichinosis?

Trichinella larvae are found in many animal species. Meat used for human consumption must necessarily undergo epidemic control. The most dangerous types of meat are pork, bear meat, wild boar meat.

The appearance of infected meat practically does not differ from the meat of a healthy carcass. The concentration of Trichinella in the affected tissue reaches 200 pieces per 1 gram. Examination of meat is carried out in the laboratory using a microscope. After analysis, a special stamp is placed on the carcass.

Where can I test for trichinosis?

In the sanitary and epidemiological station or in the veterinary laboratory of the food market, samples are taken from the animal carcass. Samples of no more than 5 g are taken from areas of increased blood supply: masticatory muscles, tongue, intercostal muscles, diaphragm.

There is no control of the veterinary laboratory in spontaneous markets, during the mass slaughter of livestock, when eating hunting trophies. Unfortunately, trichinella can be found in 30% of meat that is considered fit for food. Prevention of infection – careful cooking of meat. This is especially true when eating game in areas endemic for trichinosis.

How to cook meat to exclude infection with trichinosis?

The larva of Trichinella in the thickness of the muscle tissue can be reliably protected from damage by the capsule. This does not make it less dangerous, it also increases the protection of the parasite from extreme temperatures for it. Hunters who have got game, and villagers who grow and butcher pork in their backyard, do not always test it for trichinosis. Proper cooking of meat can prevent the disease.

The main thing is to reach a temperature of 80 ° C for 15 minutes throughout the entire thickness of the piece.

The best way to cook meat:

• Boiling for 2,5 hours meat, cut into pieces no more than 8 cm thick;

• Frying and stewing meat for 1,5 hours (pieces should not be thicker than 2,5 cm);

• Salo is allowed to use only in melted form.

Dangerous meat products:

• Homemade and raw smoked sausages;

• Meat frozen at insufficiently low temperature;

• Minced meat dishes;

• Raw lard and meat;

• Beefsteaks with blood;

• Baked ham;

• Smoked and dried meat.