Filariasis (Philariasis) is a parasitic and infectious tropical disease, that is caused by thread-like filarial nematode worms.
There are 9 known filarial nematodes which use humans as the definitive host. These are divided into 3 groups according to the niche within the body that they occupy:
Lymphatic Filariasis, Subcutaneous Filariasis, and Serous Cavity Filariasis.
- Symptoms can appear 5-18 months after a mosquito bite.
- No symptoms - many people do not develop symptoms
- Swollen lymph nodes
- Swollen armpit lymph nodes
- Swollen groin lymph nodes
- Arm swelling
- Breast swelling
- Leg swelling
- Male genital swelling
- Massive leg swelling
- Massive genital swelling
- Lymph gland obstruction
- Limb swelling
- Acute funiculitis
- Chronic lymph gland enlargement
- Rupture of lymph into urinary tract
- Lymph varices
- Thickened skin
- Warty skin appearance
Lymphatic Filariasis is caused by the worms Wuchereria bancrofti, Brugia malayi, and Brugia timori. These worms occupy the lymphatic system, including the lymph nodes, and in chronic cases these worms lead to the disease Elephantiasis. Subcutaneous Filariasis is caused by Loa loa (the African eye worm), Mansonella streptocerca, Onchocerca volvulus, and Dracunculus medinensis (the guinea worm).
These worms occupy the subcutaneous layer of our skin, our fat layer.
Serous Cavity Filariasis is caused by the worms Mansonella perstans and Mansonella ozzardi, which occupy the serous cavity of the abdomen.
In all cases, the transmitting vectors are either blood sucking insects (fly or mosquito) or Copepod crustaceans in the case of Dracunculus medinensis.
There is no vaccine for filariasis. Prevention centers on mass treatment with anti-filariasis drugs to prevent ingestion of larvae by mosquitoes, public health action to control mosquitoes, and individual action to avoid mosquito bites. To avoid being bitten by mosquitoes:
- If possible, stay inside between dusk and dark. This is when mosquitoes are most active in their search for food.
- When outside, wear long pants and long-sleeved shirts.
- Spray exposed skin with an insect repellent.
Filariasis is usually diagnosed by identifying microfilariae on a Giemsa stained thick blood film. Blood must be drawn at night, since the microfilaria circulate at night(nocturnal periodicity), when their mosquito vector is most likely to bite.Also,decreased peripheral temperature may attract more microfilariae.
Lymphatic filariasis is rarely fatal, but it can cause recurring infections, fevers, severe inflammation of the lymph system, and a lung condition called tropical pulmonary eosinophilia (TPE). In about 5% of infected persons, a condition called elephantiasis causes the legs to become grossly swollen. This can lead to severe disfigurement, decreased mobility, and long-term disability. Testicular hydrocele is a disfiguring enlargement of the scrotum.
The recommended treatment for killing adult filarial worms in patients outside the United States is Albendazole (a broad spectrum anthelmintic) combined with Ivermectin. A combination of Diethylcarbamazine (DEC) and Albendazole is also effective.
In 2003 the common antibiotic Doxycycline was suggested for treating elephantiasis. Filarial parasites have symbiotic bacteria in the genus Wolbachia, which live inside the worm. When the symbiotic bacteria are killed by the antibiotic, the worms themselves also die. Clinical trials in June 2005 by the Liverpool School of Tropical Medicine reported that an 8 week course almost completely eliminated microfilaraemia.
Soap and water and skin care to prevent secondary infections, and elevation, exercises, and, in some cases, pressure bandages to reduce swelling.