What is Filariasis?
Filariatoses (filariatoses) is a group of tropical transmissible helminth infections, the pathogens of which belong to the nematodes of the Spirurida order, family Filarudae.
Filariasis is common in countries with a humid tropical and subtropical climate (in Africa, tropical Asia, Central and South America). In the CIS countries there are only cases of importation of the disease.
Causes of Filariasis
The main human filariasis – wuchereria (pathogen Wuchereria Bancrofti), Brug’s filariasis (pathogen Brugia malayi), Loiasis (pathogen Loa loa) onchocerciasis (pathogen Onchocerca volvulus), and acanthocheilonemiasis Ozzard’s filariasis (activators Mansonella ozzardi, Mansonella perstans and Mansonella streptocerca), parafilyarioz, setarioz, dirofilariasis (activator is Dirofilaria immitis).
Pathogenesis during Filariasis
Filarias or filaments, nematodes from the order Spirurida, suborder Filariata, family Filanidae, viviparous biohelmints.
Man, vertebrates are the final owners; blood-sucking two-winged insects of various species (mosquitoes, gadflies, midges, biting midges) are intermediate hosts, they are also carriers of the parasite.
In humans, mature helminths are parasitic in lymphatic vessels and nodes, connective tissue, in the mesentery, retroperitoneal tissue, in various body cavities, in the skin and subcutaneous tissue; microfilariae (larvae) circulate in the blood or concentrate in the surface layers of the skin.
When an insect is bloodsucked, microfilariae with blood enter its stomach, then migrate to the muscles, where they turn into invasive larvae. They are brought into the piercing proboscis of the insect by the current of hemolymph, and at the next bloodsucking, the larvae enter the organism of the final host through the wound in the skin. Migrating, the larvae reach the habitat, where they turn into adult filaria. The concentration of the larvae of some species of filarias circulating in the blood may change in peripheral vessels during the day. In this regard, there are three types of invasion: periodic – a pronounced peak of number occurs at a certain time of day – day or night, subperiodic – the larvae are constantly in the blood, but at some time of day their concentration will increase; non-periodic (permanent) – microfilariae are detected in the blood at any time in the same quantity. The frequency of microfilariae is due to the time of maximum activity of the insect carrier.
The pathogenesis of filariasis is poorly understood. The leading role played by the sensitization of the body and the subsequent development of allergies.
The immune response in filariasis is formed in accordance with the general laws of the immune process. It is more pronounced for parasitizing the larvae. Immune reactions that occur against microfilariae protect the host from an uncontrolled increase in the intensity of invasion in cases of re-infection. The indigenous inhabitants of endemic foci develop partial immunity, which causes a decrease in the number of adults, a reduction in their lifespan, as well as inhibition of the reproduction of microfilariae. Resistance to repeated infections is also developing.
Symptoms of Filariasis
Filariasis is manifested by fever, skin rashes and ulcers, inflammation of the lymphatic vessels, elephantiasis of the hands, feet, scrotum, eye damage.
Diagnosis of Filariasis
The diagnosis is made on the basis of the clinical picture, data of the epidemiological history (stay in endemic areas) and the detection of microfilariae in a smear and a thick drop of blood stained by Romanovsky – Giemsa, skin biopsy specimens, in the eye (with loaosis, onchocerciasis). Also used immunological research methods (reaction of passive haemagglutination, the reaction of complement fixation, enzyme immunoassay, etc.)
Treatment of Filariasis
The treatment is carried out in the hospital dithrazine. At the same time, desensitizing drugs are prescribed (diphenhydramine, suprastin, tavegil, etc.). In case of onchocerciasis, antripol (suramin) is additionally administered intravenously, acting on mature onchocercias. When expressed allergic manifestations prescribe corticosteroids. With brugosis, onchocerciasis, surgical methods of treatment are used.
The prognosis for timely treatment is favorable; development of elephantiasis, eye damage can lead to disability. The cause of deaths can be purulent-septic complications.
Prevention of Filariasis
Prevention of filariasis provides for individual and group protection of people against the attack of insect vectors with the help of repellents, protective nets, closed clothing, bed curtains, setting of windows and doors. It is important to early detection and sanitation of microfilaria carriers as a source of the pathogen invasion. In connection with the possibility of filariasis of people who traveled to countries with a humid tropical subtropical climate, when returning from abroad, according to clinical indications, taking into account the epidemiological anamnesis, laboratory examination for filariasis is carried out. In the case of laboratory confirmation of filariasis, patients are hospitalized and at the end of the treatment they are put on clinical examination for 3 years. Apply the destruction of vectors by treating their breeding and habitat insecticides.