Trichinosis is an acute parasitic disease caused by Trichinella, which occurs in humans in severe forms and often with complications.
Content
Life cycle of Trichinella
Trichinella spiralis is a roundworm, females are 2.5-3.5 mm long and males are 1.1 mm long. The development cycle of the worm occurs without changing hosts, within one organism - humans, pigs, rats, bears and other carnivorous and omnivorous mammals. At the same time, not a single stage of helminth development is released into the external environment.
Trichinella females are viviparous; the larvae emerge from the eggs while still in the uterus. The source of human infection is the meat of animals, in the muscles of which there is an encapsulated helminth larva.
When contaminated meat enters the stomach, the muscle fibers are digested and the larvae penetrate the intestines. In the jejunum, they penetrate the mucous membrane and molt. After 3 days they reach sexual maturity and change into males and females.
On the 5-6th day after fertilization, the female gives birth to larvae. Its lifespan is about 50 days, during which time it is capable of giving birth to up to 2 thousand larvae, then dies.
Males continue to live and parasitize in the intestines.
How do Trichinella parasitize the human body?
The larvae penetrate the lymphatic and circulatory systems through the intestinal walls and spread throughout the body. They finally settle only in the striated muscles.
The larvae appear in the muscles 6-9 days after infection. Having a drilling stylet and secreting a special liquid, the larva penetrates muscle tissue, which is destroyed in the process. A person experiences quite severe muscle pain due to tissue destruction.
After 17-18 days, the larvae curl into a spiral and become capable of infecting another organism. By day 21, a capsule is formed around them, which protects the human body from direct contact with the parasite, but allows the helminth to receive nutrients and remove metabolic products.
Starting from the 6th month, the capsules become calcified and the larva can live in it for many years.
When a person’s immunity is sharply weakened, the larvae do not spread throughout the body, but remain in the intestine and penetrate the villi of the mucous membrane, where they quickly develop into adults, return to the intestinal lumen and lay larvae. There is a sharp increase in larvae in the body, which significantly worsens its condition.
What harm is done to the body?
The pathological effect of Trichinella on the body is due to:
- damage and irritation of the mucous membrane of the small intestine by adult worms,
- intoxication (poisoning) of the body during the movements of larvae,
- destruction of muscle tissue when larvae settle in it,
- tension of the body's immune reactions in response to the metabolic products of encapsulated larvae and the decay of dying parasites.
Most often larvae are found
- in the legs of the diaphragm,
- in the muscles of mastication,
- tongue muscles,
- oculomotor muscles,
- intercostal muscles,
- pectoral, cervical, deltoid and calf muscles.
Smooth muscles and cardiac muscle, as a rule, are not colonized by parasites.
Myocardial damage occurs in cases of severe infection in the form of allergic myocarditis, which is the main cause of death.
Trichinosis
In Russia, the disease is widespread. Areas of constant surveillance of epidemics are the northern regions of the Caucasus, Krasnodar Territory. The centers of spread are pigs, and to a lesser extent rats. The main factor in infection of pigs is unboiled feed from slaughterhouses. During outbreaks, both cats and dogs can become infected.
In nature, foci of infection are maintained by animals such as wolves, bears, foxes, raccoon dogs, badgers, and wild boars.
How can you get infected?
A person becomes infected with Trichinella by eating wild animal meat or pork.
This happens when the meat is not cooked well enough. The larvae can be found in bacon, brisket, lard and sausage.
Inside a piece of meat, Trichinella larvae die at a temperature of 70⁰C.
Salting and smoking have no detrimental effect on them.
The disease is usually widespread; members of the same family or people participating, for example, in the same feast are infected.
Cases of the disease are recorded mainly in the fall.
Development of the disease
There are three phases of the pathological process:
- enzymatic-toxic, which develops 1-2 weeks after infection,
- allergic at 3-4 weeks,
- immunopathological.
In the first week after infection, inflammation of the small intestine develops under the influence of metabolic products secreted by larvae and adult Trichinella.
By the end of the first week, the larvae begin to spread en masse throughout the body through the lymphatic and blood vessels. The immune system does not react to the larvae, as it is focused on producing antibodies to the metabolic products of adults. Therefore, they spread unhindered.
By the end of the second week, the level of specific antibodies becomes so high that it leads to violent allergic reactions. Severe inflammation in the small intestine leads to the death of adults. Granulomas form around the larvae, which at this time are already settling in the muscles, from which fibrous capsules are then formed.
If the larvae linger not in the muscles, but in the brain, myocardium or lungs, then round cell infiltrates form around them, in which the larvae die. This leads to disruption of the functioning of these organs, which manifest themselves as vascular disorders.
Allergic reactions of the body are manifested by swelling, secretory activity of the mucous membranes, which leads to conjunctivitis, diarrhea, runny nose, and cough.
The phase of immune reactions during intensive infection can manifest itself as systemic vasculitis and severe organ damage. In addition, complications of trichinosis can include focal myocarditis, meningoencephalitis, and focal pneumonia.
By 5-6 weeks, inflammation in parenchymal organs (brain, lungs, etc.) is replaced by dystrophic disorders.
Symptoms
Unlike many other worm infections, trichinosis occurs with severe symptoms.
Moreover, when meat is infected with pork, the disease occurs with a shorter incubation period, pronounced symptoms and moderate damage to the body.
When infected with bear meat, the incubation period is usually long, the symptoms are moderate, but serious organ damage is observed.
This is due to the fact that these Trichinella have strain differences.
A malignant course of the disease is possible, in which death occurs on days 2-3 of the disease.
There are 5 forms of helminthiasis:
- subclinical,
- erased,
- light,
- medium-heavy,
- heavy.
Severe and subclinical course
With this course of trichinosis, the incubation period is 4-5 weeks.
This form of the disease is registered in approximately 1/3 of those infected and is manifested by the following symptoms:
low-grade fever,
mild muscle pain,
slight swelling of the face,
general malaise.
In the blood there is eosinophilia (7-12%), normal leukocytes.
Light and medium-heavy forms
For mild cases
- the incubation period is 4 weeks,
- body temperature rises to 38-39⁰С.
From the first days the following symptoms appear:
- headache,
- general malaise,
- moderate pain in the calf, lumbar, masticatory muscles,
- swelling of the eyelids,
- puffiness of the face.
After 1-2 days, the body temperature drops to low-grade fever. Painful symptoms go away without treatment within 1-2 weeks.
The moderate form of the disease begins with a sharp increase in body temperature to 39-40⁰C with a gradual decrease over 2-3 hours to 38-38.5⁰C and persists throughout the first week, becoming subfebrile in the second week of the disease.
The incubation period for this form is 2-3 weeks.
Fever is accompanied by intense pain in the calf muscles, lumbar, occipital, chewing, and extraocular muscles.
Characteristic symptoms:
- pronounced swelling of the eyelids,
- puffiness of the face,
- conjunctivitis,
- rash,
- stomach ache,
- vomit,
- diarrhea.
With bronchopulmonary damage the following appear:
- bronchitis,
- pneumonia,
- pleurisy,
- heartbeat,
- dyspnea.
Changes are observed in the chemical analysis of blood:
- hypoproteinemia,
- hypoalbuminemia,
- increase in α₂-globulins, γ-globulins,
- decreased aldolase activity.
A general blood test shows leukocytosis, eosinophilia (25-60%), and in the initial period of the disease, a decrease in ESR.
Severe forms
The incubation period is short and lasts 7-10 days; in very severe cases with pronounced intestinal symptoms, it is reduced to 1-3 days.
High body temperature up to 40-41⁰С lasts 2-3 weeks and is accompanied by
- severe headaches,
- delusional
- excitement.
Intense pain in the calf, eye, chewing muscles, in the tongue, with the development of the disease in the muscles of the lower back, shoulder girdle, accompanied by cramps up to complete loss of mobility.
Multiple edema of the torso, limbs, internal organs, and
membranes of the brain lead to dysfunction of the central nervous system.
A rash appears on the skin of the face, torso, and extensor surfaces of the limbs.
Often observed
- nausea,
- vomit,
- stomach ache,
- loose stool mixed with mucus and blood.
When the respiratory system is affected, bronchitis with an asthmatic component, diffuse pneumonia, with a painful cough, shortness of breath and blue discoloration of the skin develop.
Often there are lesions of the central nervous system, which manifest themselves:
- headaches,
- insomnia,
- delusional
- convulsions,
- mental disorders,
- epileptic seizures,
- paralysis,
- deafness,
- bulging eyes,
- blindness.
In the malignant course of trichinosis, the death of patients is possible within several days as a result of ulcerative-necrotic damage to the intestines and bleeding. This development of the disease is associated with the rapid and intense development of allergic reactions.
Symptoms in children
In children, mild forms of the disease predominate, often erased and subclinical.
The temperature reaction is weakly expressed.
The main symptoms are moderate:
- swelling,
- muscle pain,
- abdominal pain.
Changes in blood tests are minor.
Doctors believe that this course of trichinosis in children is due to the lower intensity of infection and the low immune reactivity of the body.
Diagnostics
When diagnosing, an important place is given to the survey. If it turns out that the sick people ate meat, then if there are remains of this meat, it is examined for the presence of Trichinella larvae.
With the artificial digestion method, 10 g of crushed muscle mass is placed in a flask and filled with artificial gastric juice. After 4 hours, the sediment is examined under a microscope.
200 larvae per 1 g of muscle tissue correspond to a moderate degree of infection,
500 - intense, more than 500 - super-intense.
During compressor trichinoscopy, pieces of muscle tissue the size of oat grains are placed between glasses and compressed with screws. The crushed pieces are examined under a microscope.
From the third week of the disease, the diagnosis is confirmed by a serological method; ELISA is often used. 2 sera taken at an interval of 2-3 weeks are examined.
Treatment
Patients with trichinosis are treated in a hospital. The most effective treatment is in the first 2 weeks of infection, until the larvae are encapsulated.
After encapsulation, the effectiveness of treatment decreases.
Recommended antiparasitic drugs:
albendazole for a course of 8-14 days or mebendazole for a course of 5-14 days.
To reduce symptoms, antipyretic and anti-inflammatory drugs are used:
- diclofenac,
- ibuprofen.
In patients with moderate and severe disease, antiparasitic drugs cause exacerbation of allergic reactions. Therefore, they need to take glucocorticosteroids: dexamethasone, prednisone.
If glucocorticosteroids are not indicated for the patient, then antihistamines are used: promethazine, chloropyramine.
In case of severe intestinal manifestations, it is necessary to correct the water-electrolyte balance with potassium chloride or potassium and magnesium aspartate.
Severe swelling is relieved with furosemide intramuscularly or intravenously or spironolacone orally.
If necessary, protein balance is corrected.
After suffering moderate and severe trichinosis, patients need restorative treatment:
- taking vitamins,
- physiotherapy (for muscle contractures),
- anabolic agents for severe exhaustion.
Forecast
In mild forms of infection, complete recovery occurs within 1-2 months. In moderate forms, exacerbations in the form of muscle pain may occur after a course of treatment. Working capacity is restored after 4-6 months. In case of severe trichinosis, full working capacity is restored after 6-12 months.
Prevention
The main preventive measures are
- purchasing meat that has passed veterinary control,
- sufficient heat treatment of meat (the temperature of the meat inside the piece should be at least 70 degrees),
- in the absence of a guarantee of sanitary and veterinary examination, the meat should be subjected to heat treatment for at least 2.5 hours,
- keep lard frozen for at least 1 month before salting or smoking.
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