Filariasis
Overview
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. 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.
Diagnosis
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. Various concentration methods are also applied- i.Membrane filter ii.Knott's concentration method iii.Sedimentation technique
Treatment
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.