Trichinosis - Symptoms

The incubation period of trichinellosis lasts on average 10-25 days, but can range 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 clinical course, and vice versa. When infected in natural foci, such a pattern is usually not observed.

Depending on the nature of the clinical course, the following forms of trichinellosis are distinguished: asymptomatic, abortive, mild, moderate and severe.

The first symptoms of trichinosis in the form of nausea, vomiting, loose stools, and abdominal pain in some patients appear in the days following consumption of contaminated meat and can last from several days to 6 weeks.

In the asymptomatic form, the only manifestation may be blood eosinophilia. The abortive form is characterized by short-term (lasting 1-2 days) clinical manifestations.

The main symptoms of trichinosis are fever, muscle pain, myasthenia, edema, and hypereosinophilia of the blood.

Fever of a remittent, constant or irregular type. Depending on the degree of invasion, elevated body temperature in patients persists from several days to 2 weeks or longer. In some patients, subfebrile temperature persists for several months.

Edema syndrome appears and increases rather quickly - within 1-5 days. In mild and moderate forms of the disease, edema persists for 1-2 (rarely up to 3) weeks; in severe cases, edema syndrome develops more slowly, but persists longer and can recur. As a rule, periorbital edema appears first, accompanied by conjunctivitis and then spreading to the face. In severe cases, edema spreads to the neck, trunk, and limbs (an unfavorable prognostic sign). Patients with trichinosis have maculopapular rashes on the skin, sometimes acquiring a hemorrhagic character, subconjunctival and subungual hemorrhages.

Muscle syndrome manifests itself as myalgia, which in severe cases becomes generalized and is accompanied by myasthenia. Pain appears first in the muscles of the limbs, then in other muscle groups, including chewing, tongue and pharynx, intercostal, and oculomotor. In the late stage of trichinosis, muscle contractures may develop, leading to immobilization of the patient.

When the lungs are affected, developing during the first 2 weeks of the disease, a cough is observed, sometimes with blood in the sputum, signs of bronchitis, and “flying” infiltrates in the lungs are detected on X-ray images.

In the peripheral blood, eosinophilia and leukocytosis usually increase from the 14th day, hypoproteinemia is characteristic (decreased albumin content), the level of potassium and calcium is reduced, and the activity of enzymes (creatinine phosphokinase, aspartate aminotransferase, etc.) in the blood serum is increased. Eosinophilia reaches its maximum values in the 2nd-4th week and can remain at a level of 10-15% for 2-3 months or longer. There is a certain relationship between the level of eosinophilia and the severity of clinical signs of trichinellosis. In patients with a severe course, eosinophilia in the peripheral blood may be insignificant or even absent.

Mild trichinellosis is characterized by a slight increase in body temperature (up to 38 °C), swelling of the eyelids, mild pain in the muscles of the extremities and low eosinophilia.

Moderate trichinellosis is characterized by an incubation period of about 2-3 weeks, acute onset with fever up to 39 °C for 1-2 weeks, facial edema, moderate pain in the muscles of the extremities, leukocytosis of 9-14x10 ⁹ /l and eosinophilia of 20-25% and higher.

Severe trichinellosis is characterized by a short incubation period (less than 2 weeks), prolonged high temperature for at least 2 weeks, generalized edema, which is largely due to accelerated protein catabolism and hypoproteinemia, myalgia with muscle contractures and complete immobility of the patient. The hemogram shows hyperleukocytosis (up to 20x10 ⁹ /l), hypereosinophilia (up to 50% and higher), however, in extremely severe cases, eosinophilia may be absent or insignificant (a poor prognostic sign). Dyspeptic and abdominal pain syndrome are common, and hepatomegaly occurs in more than 50% of patients.

The total duration of manifest forms of the disease, depending on the severity of the course, ranges from 1-2 to 5-6 weeks. The recovery period for severe trichinellosis can be 6 months or more. Symptoms of trichinellosis such as muscle pain and facial swelling can periodically recur, accompanied by fever and other symptoms. Relapses are easier than the primary disease.

Mortality and causes of death

The severity of trichinellosis and its outcome largely depend on organ damage developing in the 3rd-4th week of the disease; one of the most serious of these is myocarditis. With its development, tachycardia, hypotension, possible heart rhythm disturbances, and heart failure may occur. The borders of the heart are expanded, and diffuse myocardial damage and sometimes coronary disorders are detected on the ECG. Myocarditis in trichinellosis is one of the main causes of death occurring in the period from the 4th to the 8th week of the disease. The next cause of death after myocarditis is lung damage. In moderate to severe cases, signs of bronchitis and "flying" infiltrates in the lungs are clinically and radiologically detected. In severe cases, pulmonary damage may have the appearance of lobar pneumonia with the appearance of serous effusion in the pleural cavity. Pulmonary edema is possible, which is also facilitated by the development of cardiovascular insufficiency. A secondary bacterial infection may occur. CNS damage is manifested by headache, drowsiness, sometimes delirium, signs of meningism associated with edematous syndrome. In later stages, severe disorders are recorded, such as polyneuritis, acute anterior poliomyelitis, severe pseudoparalytic myasthenia (myasthenia gravis), meningitis, encephalitis with the development of psychosis, local paresis or paralysis, coma. Mortality in the absence of adequate treatment can reach 50%.