Toxocarosis - Causes, symptoms and treatment. MF.

Toksokaroz is widely distributed in a number of countries, some of which are in Africa, Southeast Asia, Russia, the USA, England, Poland and others. This parasitosis, which is not typical for humans, is mainly distributed among stray cats and dogs with a lifelong carrier of larvae in the body, throwing helminth eggs in dwelling massifs with feces. The average infection rate among dogs and cats is about 16%, however, in a number of regions it reaches up to 90%.In a population of perfectly healthy people, positive immunological tests for toxocarosis are recorded in 5-15% of cases.

Toxocarosis is a zoonotic parasitic disease characterized by ingress( migration) and harmful life activity in the human body of roundworm larvae - toxocar, with possible damage to internal organs and systems.

Pathogen causative agent

The causative agent of toxocarias can be: Toxocara canis( dog roundworms), Toxocara mystax or cati( cat), Toxocara vitulorum( buffalo toxoids, cows).Toksokary are of the type Nemathelminthes( round worms), the genus Toxocara. Most cases of toxocarosis are associated with T. sanis. These are dioecious round worms or nematodes having a yellowish color, 4-10 cm long( male) and 6-18 cm( female) with a curved caudal end, as well as a mouth opening with 3 lips. The cephalic end of the worms has swollen cuticles in the form of "side wings", in terms of which differential diagnosis is performed.

Brown eggs( from light to dark shade) are round in shape with a dense outer shell, the eggs are 65-75 microns in size( they are larger than the ascarids, but they have a similar structure).If the egg is invasive( ripe), then inside it is a sufficiently mobile larva. If the egg is non-invasive( immature), then inside the larva there is no, but there is a blastomer of spherical shape.

Egg toxocary

Sexually mature forms of toxocar inhabit mainly in the small intestine and stomach of animals, mainly young dogs, cats and other animals, as well as intermediate hosts. The life expectancy of worms is from 4 to 6 months. Sexually mature female is able to postpone up to 200 thousand eggs per day. Since 1 grams of faeces of a sick animal can contain up to 12-15 thousand eggs, it is not difficult to imagine how many of them are in the soil during defecation. Eggs when defecated fall into the soil, where under certain conditions( temperature and humidity) ripen within 5-30 days, and ripe eggs in the soil can maintain their viability for several months and even years.

Toksokara sexually mature

A short cycle of development of toxocarias in the animal: The final host is the animal dog( most often) or feline. Infection occurs either by oral route when ingested infected soil, or transplacentally from the female puppy. Then the life cycle of development takes place either along the main path( dog-soil-dog) or along an auxiliary path( dog-soil-intermediate host( rodents, pigs, sheep or man.) In the second case, a "biological impasse" arises, since the intermediate host(in particular, a person) does not participate in the transmission of infection. The peculiarity of toxocarosis is that either a complete migration of toxocar larvae( about 5 weeks) occurs with the formation of the sexually mature stage in the intestine of the animal and the release of eggs( this is more common in young puppiess) or migration in somatic organs( adult animals) and the possibility of infection in pregnant animals of their offspring.

The cycle of development of toxocarosis in humans resembles ascariasis. After ingestion, the eggs enter the small intestine, where larvae emerge from them, which through the blood vessels enter the liver, in which a part of them settles and forms around itself a kind of inflammatory granulomas. Then, through the lower hollow vein, the larvae move to the right heart. From there, the pulmonary arteries get into the lungs, where again some of them are delayed. From the pulmonary artery, the remaining larvae enter the pulmonary veins and enter the left heart. Further along the large blood flow it moves to vessels in diameter of about 0.02 mm, where they get stuck and exit into that organ where they are stuck. Consequently, multi-organ pathology( lungs, liver, pancreas, muscles, eyes, thyroid, kidneys, brain and others) is possible. In these organs, for a long time( months, years), the larvae retain their viability. Under the influence of various factors affecting human immunity, larvae can again carry out their migration, which is characterized by a relapse of toxocariasis. Larvae toxocar in the human body can survive up to 10 years. Some of the larvae settled in the organs are encapsulated( forming tight capsules around themselves), in which they gradually break down. From the lungs on the bronchial tree get into the nasopharynx, esophagus, ripen in the omentum.

In humans, toxocares are parasitic only at the stage of the larvae, so a person is not contagious to others.

Toksokaroz, larva

What are dangerous for human larvae toxocar?

The main danger of toxocar larvae is the occurrence of systemic allergic reactions with characteristic manifestations. Also, given the peculiarity of subsidence in various organs and the ability to form inflammatory infiltrates around the body - granulomas, there is a danger of impaired functions of the affected organs and systems( liver, kidney, eyes, thyroid, brain and others).We must not forget that the larvae that have settled down and "silent" at first glance, while reducing the body's defenses, can resume their migration again and appear in another organ, violating its functional state.

Causes of the appearance of human toxo-acarose

The source of infection for human is dogs, especially young puppies, and other representatives are also possible( for example, cats, which is less common).Man is not the source of infection.

Source of invasion with toxocarose

Transmission mechanism - fecal-oral. Infection occurs when swallowing eggs toxocar in case of direct contact with the wool of a sick animal on which invasive eggs can be found, as well as contact with soil containing eggs, the consumption of contaminated food. Transmission factors can be dirty hands, unwashed vegetables, fruits, berries, poorly thermally processed meat of the intermediate host - pigs, chickens, lambs, for example, contaminated water. The possibility of transmission of infection from a pregnant woman to a fetus, as well as breastfeeding, is not ruled out, but this path has not been proven.

Groups at risk for toxocariasis infection:
1) preschool age children( 3-5 years old) playing with sand, soil or with a dog;
2) professional groups( veterinarians, dog breeders, cynologists, communal workers, chauffeurs, nursery workers for dogs, sellers of vegetable stores and departments, persons who have contact with soil and others);
3) owners of dachas, household plots, land plots and vegetable gardens;
4) lovers of hunting with the involvement of dogs.
Mostly children who, playing in the yard( sandboxes), swallow eggs with dirty hands. Summer-autumn seasonality is characteristic.

Clinical forms and symptoms of toxocarosis

There are two forms: visceral( systemic) and eye toxocariasis.

1. Visceral form of toxocariasis( more frequent in children)
- acute infectious-toxic syndrome( weakness, lethargy, fever in the afternoon or evening, body temperature is often subfebrile - up to 37,50, less often febrile - above 380 with relapses in the periodpulmonary manifestations);
is a broncho-pulmonary syndrome( beginning with catarrhal phenomena in the form of a throat swelling and coughing up to a severe asthmatic condition, there may be bronchitis, bronchopneumonia, asthmatic component of coughing( cough with dyspnea), dry, less damp rales are heard, roentgenologically:"Eosinophilic or infiltrates,
- hepatic syndrome( enlargement and compaction of the liver, its soreness, in 50% of patients combination with enlarged spleen)
- syndrome of poly-lymphadenopathy( enlargement of lymph nodes of various grooves
- allergic syndrome( urticaria or vesicular rashes on the skin in the form of bubbles with transparent contents),
- abdominal syndrome( abdominal pain, nausea, vomiting, diarrhea, flatulence).

There may be lesions: pancreas( pancreatitis), heart( myocarditis), brain
( prolonged headaches, epileptiform seizures, paresis, paralyzes)

In the general blood test: eosinophilia( up to 70-90%), leukocytosis( up to 15-20 thousand), insignificant increaseESR.With prolonged course, patients develop anemia( reduced hemoglobin), hypergammaglobulinemia, an increase in Ig E. In a biochemical blood test: there may be an increase in bilirubin, an increase in the activity of enzymes - ALT, AST, GGTP.

An important problem of toxocarias is its relationship with the development of bronchial asthma. A number of scientific studies have shown the detection of antibodies to toxocaram in patients with bronchial asthma, as well as the improvement of the course of asthma after the treatment of toxocariasis.

2. Eye toxocariasis( 67% of all cases)
Develops with nonintensive invasion. Often one eye is affected: toxocars penetrate into the choroid of the eye, cause inflammation and the formation of specific granulomas in the retina, the lens. Endophthalmia, iridocyclitis, keratitis can develop until the loss of vision is complete.
In the general analysis of a blood: eosinophilia is not present. Methods of detecting toxocar in the contents of a special element of the eye - the vitreous humor are used. Most often, in case of toxocarosis, the process is one-sided.

Eye damage with toxocarose

Fibrosis and retinal detachment with toxocarose

The course of toxocarosis varies from subclinical and mild forms to the development of a recurring course of the disease( months, years), which is due to repeated processes of migration of larvae of toxocar.

Diagnosis of toxocarrosis

Preliminary diagnosis of toxocarias is exposed on the basis of clinical symptoms of bloating( allergic reaction, bronchopulmonary syndrome, hepatosplenomegaly and others), general blood analysis( pronounced increase in eosinophils in peripheral blood, increase in leukocytes, ESR, decrease in hemoglobin), changes in biochemistry, ALT, AST, GGTP), an increase in gamma globulins.
Differential diagnosis of toxocariasis with other helminthiases - opisthorchiasis, ascariasis, lymphogranulomatosis, vasculitis, eosinophilic granuloma and others.

The final analysis is made after a specific laboratory examination. Serological diagnosis is used - an ELISA test for the detection of specific antibodies - ELISA with toxocarose antigens.

The diagnostic titer is 1: 400.The titers below 1: 400( 1: 100, 1: 200), especially in the absence of symptoms of the disease, are considered as a sign of invasiveness, but not the presence of the disease in the present( recall the ability of toxocar encapsulated and the possibility of dying inside the capsules, which will also be accompanied by antibody circulation inblood for a certain time).In this case, the prescribed treatment will not bring the desired effect, the titers will remain at the same level. Titer 1: 200 may also indicate a remission( recovery) of visceral toxocarias for several months after treatment.
Captions 1: 200-1: 400 can talk about the presence of toxocaroness( carriers of encapsulated larvae).
Titer 1: 400 indicates a likely eye toxicity or remission of visceral toxocarias after treatment during the first weeks. The purpose of therapy should be weighed and proven by the clinical symptoms of the disease.
Titer 1: 800 and more indicates the incidence of visceral toxocariasis, which is an absolute indication for the purpose of treatment.

Do not forget about the possibility of recurrence of the disease, so in a particular patient, antibody titers can vary and fluctuate. False positive reactions to antibodies to toxocar can be detected: in patients with systemic lymphoproliferative diseases, gross violations in the immunity system. The final verification of the diagnosis also requires detection of larvae in tissue biopsies( most often it is possible with liver damage).

Treatment of toxocarrosis

Specific( antiparasitic) treatment is prescribed only by the doctor in the presence of strict indications( symptoms of the disease, changes in the general blood test, high titer of the ELISA response).The drugs are effective only in the presence of migrating larvae, there is a weak efficacy in the presence of granulomas in tissues and absence of migration.

As antiparasitic therapy, albendazole( zentel, nemozol), mebendazole( vermox, vormin), thiabendazole( minesol), medamine are used. The course of treatment is from 10 to 30 days, depending on the form of the disease and the chosen drug. Treatment is carried out 3-5 courses with an interval of 3-4 months( you can 2 months with a steady decrease in the titer AT).Criteria of effectiveness: decrease in the level of eosinophils, antibody titer, stagnation of symptoms.

For the purpose of intensifying treatment, symptomatic therapy is prescribed: hepatoprotectors( essliver, karsil, hepatrinum and others), antihistamines( claritin, zodak, zirtek, cetrin, erius and others), nonsteroidal anti-inflammatory drugs( diclofenac, indomethacin, ibuprofen and others), expectorants, enteroseptics, immunomodulators and others.

The prognosis of toxocarias is generally favorable. Lethal outcomes are rare in the case of intensive invasion, the absence of therapeutic measures.

In the case of eye toxocariasis, the prognosis depends on the severity of the changes. If the timing of infection is small and there is an active infection( that is, there is active migration), there is a chance of medicinal action on the larvae and regress of the inflammatory process in the organs of vision. If there is a central location of the foci, and also in the formation of fibrosis, the prognosis in terms of visual functions is unfavorable, the changes are irreversible.

Prevention of toxocarrosis

Preventive measures are related to the hygiene of children, hygiene training for the younger generation. One of the areas of prevention is the timely examination of dogs and their de-worming. Protection of children's playgrounds, sandboxes from visits to animals, their good insolation( sunlight illumination).

Doctor infectious diseases Bykova N.I.