Trichinosis - Causes, symptoms and treatment. MF.
Trichinosis is one of the serious parasitological diseases of a person with the presence of natural foci and quite frequent registration in many countries of the world, as well as in Russia. The acute development of the disease and the possible severe consequences of trichinosis are extremely relevant in the context of parasitology.
Trichinosis is helminthiosis with natural focal distribution caused by nematodes of the genus Trichinella, characterized by acute course with the presence of a specific "tetrad of signs", capable of leading to loss of ability to work and even death.
Foci of trichinosis correspond to the spread of natural reservoirs( bears, wild boars, badgers and others) and are recorded in the USA, Germany, Poland, Ukraine, Belarus, the Baltic countries. In Russia, the greatest activity is registered in Khabarovsk, the Krasnoyarsk Territory, the Magadan Region, the Krasnodar Territory. There are also synanthropic( urban) foci of trichinosis, where the reservoir can be domestic animals - dogs, cats, pigs, and rodents.
Trichinosis, scheme of epidemic spread
Pathogen of trichinosis
Trichinella spiralis ( female Trichinella 1.5-1.8 mm, and fertilized - up to 4.4 mm, male about 2 mm).In nature, there are 4 species of Trichinella: T. spiralis, T. nativa, T. nelson, T. pseudospiralis. These small, even thread-like helminths, have a rounded body and narrowed ends.
Trichinella
Capable of forming around itself capsules that have good protective functions. Encapsulated larvae are resistant to both high temperatures and freezing. Withstand boiling for about 3 hours. Encapsulated larvae die during heat treatment of meat at least 80º for about 4 hours. Smoking and salting of meat on encapsulated larvae have no effect.
Trichinosis, encapsulated larva
The cycle of development of Trichinella is rather peculiar. The same organism is for Trichinella both the main and intermediate host. They enter the human body with the meat of animals infected with muscle trichinella( this is the larval stage).Larvae are released from the capsule and within 1-1.5 days reach the stage of the intestinal Trichinella( directly on the mucosa of the intestinal wall).
During the period of parasitization in the human intestine( about 42 - 56 days), one female lays about 1500 larvae. Through the mucous membrane of the intestine they penetrate into the lymphatic system, then into the blood and are carried throughout the body. Five to eight days after infection, the larvae enter the skeletal striated muscles( almost all organs except the heart) - more often the tongue, forearm, diaphragm, intercostal, deltoid, gastrocnemius muscles. Further, they secrete hyaluronidase, penetrate the sarcolemma of the muscle fiber, where they are encapsulated( the functions of the capsule are nutrient, protective).
After 6 months begins calcification of the capsule, which lasts about 2 years. At this stage, the development of helminth ends. In capsules, the larvae remain viable for 25 years or more.
Immunity after a trichinosis has been lifelong, but non-sterile( there are antibodies in the blood that protect against repeated infection, but encapsulated larvae remain in the tissues).
Causes of trichinosis
The wild animals - wild boars, badgers, brown and white bears, fox, nutria, marine mammals - whales, seals, etc., are the reservoir of infestation and the source of parasitosis for humans in natural foci, and in the settlements, pets are pigs, dogs.
Trichinosis, sources of infection
The infection mechanism is nutritional, and the path is - food. A person becomes infected by eating insufficiently thermally processed contaminated meat. Transfer factors can be pork sausages, homemade fat, lard, ham, bacon, brisket and others.
Susceptibility to trichinosis is quite high. It is enough about 10 g of infected meat to start the invasion. Often fall ill with whole groups or families after a feast, a hunting meal.
Seasonality for trichinellosis is more often autumn and winter( with the use of natural foci, hunting period), in urban centers - autumn( slaughter of pigs).
A brief description of the development of human trichinosis
Two phases are distinguished in the development of parasitosis.
1) phase of allergic manifestations of ( lasts 2-3 weeks after infection) - sensitization of
( allergic reorganization) of the organism occurs with the products of vital activity and death of helminths. Developed allergic reactions with vascular damage and coagulation disorders due to the introduction of trichinella larvae into the musculature( allergic myositis occurs in the muscles).
In the muscles around the larvae a protective granulation shaft is formed - a capsule is formed, which prevents the entry of helminth antigens into the human body. Under the influence of immunosuppressive drugs( for example, hormonal drugs), as well as with excessive activity of the immune system( with massive invasion), this process may be disrupted. There is an allergic myositis and mass death of larvae in muscles, as well as in organs - nodular infiltrates are formed from lymphoid elements, plasma cells, eosinophils.
2) The phase of organ damage ( from 3-4 weeks after invasion), which is associated with the arrival of larvae in the
organs and the development of systemic vasculitis in them.
Trichinella in muscle tissue
Clinical forms and symptoms of trichinosis
The incubation period( from the time of infection to the appearance of the first symptoms of the disease) is 10 to 25 days, but can be shortened to a week( in massive invasions) and extend to 45 days( for mild forms).
Trichinosis can be acute and chronic.
The severity of the flow of acute trichinosis is subdivided into heavy, medium and light forms. There may be atypical( with unusual clinic and symptoms) forms of trichinosis, which include the erased and asymptomatic.
Acute trichinosis
During the illness, the following are distinguished:
is an acute period involving the phase of allergic manifestations and the phase of organ damage,
is the period of convalescence( recovery).
Trichinosis is characterized by a characteristic tetrad character:
1) fever,
2) edematous
syndrome 3) muscle pain,
4) high eosinophilia in the blood.
The onset of the disease is acute, a high fever appears from the first day of the illness.
1) fever is more often remitting or incorrect. Within a few days, the temperature of the
rises to 40º, keeps at the same level for several days, then also lytically decreases. Some patients have a subfebrile condition( temperature up to 37º), which can last several months. In mild forms, the temperature may not rise. Fever is a manifestation of general intoxication( weakness, chills, headaches, nausea).
2) One of the permanent signs of trichinosis is edema of the eyelids and face combined with conjunctivitis ( because of this feature trichinosis was called "puffy").Appearing on the 1-5th day of the disease, may persist for 1-2 weeks. In severe forms, swelling develops more slowly and lasts longer. First there are swelling of the eyelids, superciliary arches, then the entire face. In severe cases, edema descends to the neck, trunk, upper and lower limbs - this is an unfavorable prognostic sign.
Edema in trichinellosis
3) With 3 or more days of illness, muscular pains of of different muscle groups appear in most patients.
The muscles of the legs( usually calf) hurt first, then the muscles of the buttocks, back, abdomen, arms, shoulder girdle, neck, tongue, pharynx, oculomotor, chewing. Muscle pains are often intensive, with movement increasing, palpation of the muscles is painful. In severe cases severe myalgias with contractures occur, sometimes leading to immobility of the patient. Muscle pain and swelling persist for 1-3 weeks and can recur periodically, accompanied by fever( relapses occur more easily than the primary disease).
The acute period of trichinosis is also characterized by:
- abdominal syndrome( abdominal pains, dyspeptic disorders),
- allergic manifestations in the form of polymorphic rash on the skin of the whole body( urticaria, roseosa, spotted).
4) , characteristic for acute period, reaches a high level( up to 80%), appears with
of the first days of the disease with a maximum increase at 2-4 weeks( with a mild form - no more than 30%, with an average - up to 60% andmore, with severe - the number of eosinophils is not significant, but a sharp increase to 95% is a prognostic adverse trait).
In severe cases, organ lesions appear that develop 3-4 weeks after infection. Organ damage is often the cause of death.
Develop:
1) myocarditis of allergic nature - the main cause of death( tachycardia, hypotension, symptoms of acute vascular insufficiency, collapse).On ECG - signs of diffuse myocardial damage.
2) lung damage( pneumonia with involvement in the pathological process of the pleura), which are associated with systemic vasculitis.
3) central nervous system damage( meningoencephalitis, encephalomyelitis).
4) liver damage.
5) thrombohemorrhagic syndrome( a disorder of the blood coagulation system).
The total duration of the disease on average is from 1-2 weeks( light forms) to 5-6 weeks. With the time started treatment, these periods are shortened by 3-5 days. In severe form of trichinosis, the recovery period can last up to 6 months or more. Prolonged convalescence in the form of asthenia( weakness, fatigue, decreased appetite), myalgia can be observed in patients taking immunosuppressive( immunosuppressive drugs, for example, hormones) drugs.
In the absence of treatment, the defeat of vital organs can develop and a fatal outcome is possible. Mortality in trichinellosis can reach 5%.However, not always easy forms can be correctly diagnosed and timely treatment is prescribed. There is a possibility that with a mild form of trichinosis, a lethal outcome will not occur, since recovery may occur in the immunocompetent organism( but in a small percentage of cases).
Diagnosis of trichinosis
Preliminary diagnosis is made on the basis of clinical and epidemiological data. When collecting an epidemiological anamnesis, attention is drawn to the fact of using insufficiently thermally processed pork and wild animal meat - wild boar, brown bear, deer;when analyzing complaints, attention is drawn to the characteristic "tetrad" of clinical symptoms.
The final diagnosis is made on the basis of laboratory tests:
1) detection of Trichinella larvae in residues of meat consumed;
2) detection of larvae in muscle biopsies( trichinelloscopy) - take a gastrocnemius or tick-shaped muscle;
3) serological diagnosis( RNGA becomes positive from the 15th day of the disease, ELISA method);
4) skin-allergic tests( positive from 2 weeks of illness, persist for many years).
Differential diagnosis is performed with opisthorchiasis, strongyloidiasis, typhoid fever, face mug, pseudotuberculosis, iersiniosis.
Treatment of trichinosis
Treatment includes specific( etiotropic) and pathogenetic therapy.
The tasks of etiotropic therapy: destroy intestinal Trichinella, stop the production of larvae, disrupt the encapsulation process and increase the death of muscle trichinella.
Apply: mebendazole( vermox) - different schemes on average for 14 days course;minesol( thiabendazole) - less effective than vermox due to adverse reactions, but also used in a number of cases;albendazole.
The most effective implementation of specific( etiotropic) therapy in the incubation period, when possible prevention of clinical manifestations, or in the early days of the disease, when there are still intestinal Trichinella. During the muscular stage and encapsulation, its effectiveness decreases and may contribute to exacerbation of the disease.
Specific treatment should be "covered" with the appointment of antihistamines( claritin, zodak, zirtek, cetrine, erius and others).
The appointment of hormonal treatment is indicated in severe forms of trichinosis and in the development of complications( because of the effect on the process of capsule formation around the larvae) - prednisolone is prescribed in medium and high doses and short courses - from 40-80 mg / day for 5-7 days withsubsequent reduction of the dose and withdrawal of the drug after 1-1.5 weeks. Since hormones can prolong the period and the amount of production of larvae in the intestine, it is recommended that anthelminthic drugs be administered throughout the period of their application and a few days after their cancellation.
Control of the effectiveness of treatment is carried out in 6-12 months( efficiency of dehelminthization - 90%).
Pathogenetic therapy of includes antipyretics, analgesics, non-steroidal anti-inflammatory drugs.
Trichinosis prophylaxis
Pay attention to the meat that you are going to cook. Any foreign inclusions are an excuse not to use it for food. If the invasion is massive, you can see the yellowish pea is very small in the fibers of the striated muscle, but with nonintensive invasion it is not visible. That is why meat, which is sold in stores and in markets, must necessarily pass universal trichinelloscopy.
Infected meat should not just be thrown away, stray animals can eat it and the disease will continue to spread. Such meat is processed with kerosene and buried in the ground to a depth of at least 1 meter.
And even normal meat in your opinion should be subjected to long-term heat treatment.
Meat of wild animals should also be subjected to trichinelloscopy, which is established by the current veterinary legislation, and if at least one larva is found, it is recycled. When there is no possibility of trichinelloscopy, heat treatment of meat should last at least 6 hours.
The doctor infektsionist Bykova N.I.