Filariasis or elephantiasis is the disease caused by the nematode parasites. Wuchereria bancrofti, Brugia malayi and Brugia timori, commonly called phyllia, which lodge in the lymphatic vessels causing lymphedema.
This disease is also known as elephantiasis due to the elephant leg aspect of the patient with this disease. Its transmitter is the mosquitoes of the genera Culex, Anopheles, Mansonia or Aedes, present in tropical and subtropical regions.
When the nematode obstructs the lymphatic vessel, the edema is irreversible, hence the importance of prevention with mosquito nets and repellents, as well as preventing the accumulation of standing water in old tires, cans, pots and others.
The adult forms are nematode worms of circular section and complete digestive tract. Females (a few centimeters) are larger than males and reproduction is exclusively sexual, with microfilariae generation. These are small spindle larvae with only 0.2 millimeters.
The larvae are transmitted by the bite of mosquitoes and the Chrysomya fly known as Varejeira Fly. From the bloodstream they go to the lymphatic vessels, where they mature into adult sexual forms. After about eight months of the initial infection, they begin to produce microfilariae that appear in the blood, as well as in many organs.
The mosquito gets infected when it bites a sick human being. Inside the mosquito the microfilariae change after a few days into infectious forms, which migrate mainly to the mosquito's head.
Progression and symptoms
The incubation period can be one month or several months. Most cases are asymptomatic, but microfilariae are produced and the individual spreads the infection through the biting mosquitoes.
Episodes of microfilariae transmission (usually at night, depending on the species of the vector) through the blood vessels can lead to immune system reactions such as itching, fever, malaise, cough, asthma, fatigue, rash, adenopathy (swollen glands). lymph nodes) and swollen limbs, scrotum or breasts. Sometimes it causes inflammation of the testicles (orchitis).
In the long term, the presence of several pairs of adults in the lymphatic vessels, with fibrous and obstructed vessels (forming palpable nodules) can lead to lymph accumulations upstream of the obstructions, with dilation of alternative lymphatic vessels and thickening of the skin.
This condition, ten to fifteen years later, manifests as a grotesque swelling of the affected regions, especially the legs and scrotum, due to lymph retention. Lymph vessels enlarged by retained lymph sometimes burst, complicating lymph drainage even further. Sometimes the legs become thick, giving an appearance similar to elephant paws, described as elephantiasis.
Diagnosis and Treatment
The diagnosis is by microscopic observation of microfilariae in blood samples. If the species presents nocturnal periodicity, it is necessary to collect blood at night, otherwise they will not be found. The ultrasound allows to detect the adult forms. ELISA serology is also useful.
Antiparasitics such as mebendazole are used. It is important to treat secondary infections.
There is a WHO program that seeks to eliminate the disease with drugs administered as prevention and insecticides. It is useful to wear clothes that cover as much skin as possible, insect repellents and sleep protected with nets.