What is Loaoz?
Loaoz (Colabar tumor) is a chronic helminth infection, the characteristic feature of which is the migration of sexually mature parasites into the tissues of the body, which causes the development of the so-called Calabar tumor.
Loaoz is distributed only in the countries of West and Central Africa. People of any gender and age are susceptible to loazu, but adult men with black skin are more often ill. It is estimated that about 12-13 million people are infected with loaoz.
Causes of Loaza
The causative agent of loazi is the round worm Loa loa. Worms dioecious. The size of adult females is 50-70 mm in length, the males are 25-35 mm. The thickness of the worms is about 0.25 mm. Adult parasites live in the subcutaneous fatty tissue, the disease belongs to the group of filariasis.
Pathogenesis during Loaza
The final owner is a person in whose body mature filaments parasitize in the subcutaneous tissue, under serous membranes and conjunctiva.
Filarias produce microfilariae, which at night are located in the vessels of internal organs, and during the day they are concentrated in the peripheral vessels of the skin. The maximum number of microfilariae in peripheral vessels is found during the day, from 12 to 14 hours. Intermediate hosts of parasites are gadfly of the genus Chrysops, in the body of which microfilariae reach maturity within 7-12 days.
The development of microfilariae in the body of gadfly at a temperature of 28-30 ° and an absolute humidity of 92% ends in 7 days, at a lower temperature and humidity – in 10-20 days.
Infected gadflies while sucking the blood of a healthy person are injected into the blood of microfilariae in the invasive stage. Blind people attack people during the day, they are attracted by moving objects, smoke, fire. They usually live in forests and shrubs along the banks of rivers, but can also fly into nearby settlements.
In humans, they become sexually mature in a few months (from 6 to 18) and can parasitize up to 15 years.
The main role in the mechanism of development belongs to the toxic-allergic reactions that occur on the products of parasites, with which most of the symptoms of infection. Of great importance is also the factor of mechanical damage to the tissues as a result of the movement of mature worms. Pathogenetically due to the possibility of attaching a secondary bacterial flora and the formation of abscesses.
Symptoms of Loaza
Residents of endemic foci and newcomers have different manifestations of the disease. In some parts of the indigenous population, it is asymptomatic, with microfilariaemia. In this situation, the diagnosis is established only after the migration of the adult parasite under the conjunctiva.
The incubation period usually lasts several years, occasionally shortened to 4 months. The disease begins with allergic manifestations. An urticaria rash appears on the skin, the body temperature rises to subfebrile numbers, the patient is disturbed by pain in the extremities, paresthesia. Subsequently, the movement of parasites in the subcutaneous tissue causes itching and burning. When the parasite penetrates under the conjunctiva of the eye, conjunctivitis develops with swelling of the eyelids and sharp pains. When Loa loa enters the urethra, pain occurs regardless of urination. The disease is characterized by the sudden appearance of painless edema in limited parts of the body, which usually resolves within three days, less often than several weeks. The skin in the edema pales or, conversely, becomes hyperemic. Edemas are found in different parts of the body, but most often on the extremities. There is a more frequent occurrence of tumors in the summer hot weather. Cases of the development of hydrocele in men, as well as numerous intramuscular abscesses, which arise as a result of the addition of a secondary infection in the places of death of adult parasites, are described. There are reports of the development of symptoms of encephalitis with the penetration of parasites into the central nervous system. In peripheral blood, marked eosinophilia and secondary anemia are noted.
Diagnosis of Loaza
The possibility of loaosis should be considered when the symptoms of Calabar edema develop in patients in hot countries. With the penetration of the parasite under the conjunctiva of the eye, it is easily detected during normal examination. The diagnosis is confirmed by the detection of microfilariae in the blood during the daytime. Approximate values are intradermal allergy test and the reaction of complement fixation. Blood eosinophilia is also taken into account.
Diethylcarbamazepine (8-10 mg / mg / kg / day by mouth for 21 days). The drug acts on both adult worms and their larvae. It requires several courses of treatment. With a large number of microfilariae treatment may be accompanied by increased allergic manifestations, adverse reactions, including from the central nervous system. In case of severe invasion, it is recommended to start treatment with glucocorticoids (prednisone, 40-60 mg / day, by mouth) and small doses of diethylcarbamazine (0.5 mg / kg / day). In the absence of side effects, the dose of prednisone is reduced, and the anthelmintic drug is increased. Prophylactic administration of diethylcarbamazine (300 mg orally once a week) prevents infection.
Prevention of Loaza
Prevention of loaza is the identification and treatment of infected persons, the improvement of the environment in order to eliminate the breeding ground of gadflies.
In terms of personal prevention, the basis is protection against gadfly and chemoprophylaxis: 200 mg ditrazine 2 times a day for 3 consecutive days once a month.