FILARIASIS, the name of a disease due to the nematode Filaria sanguinis hominis, of which two varieties are known nocturna and diurna. A milky appearance of the urine, due to the presence of a substance like chyle, which forms a clot, had been observed in tropical and subtropical countries; and it was proved that this condition is uniformly associated with the pres ence in the blood of microscopic eel-like worms, the embryo forms of a Filaria (see NEMATODA). Sometimes the discharge of lymph takes place from ulcers on the surface of the body, or there is naevoid elephantiasis of the scrotum, or lymph-scrotum. More or less of blood may occur along with the chylous fluid in the urine. Both the chyluria and the presence of filariae in the blood are curiously intermittent ; with the nocturnal variety of parasite possibly not a single filaria is to be seen during the daytime, while they swarm in the blood at night. This alternation may be in verted by causing the patient to sit up all night and sleep through the day.
Sir P. Manson proved that mosquitoes imbibe the embryo filariae from the blood of man ; and that many of these reach full development within the mosquito, acquiring their freedom when the latter resorts to water, where it dies after depositing its eggs. Mosquitoes are thus the intermediate host of the filariae, and their introduction into the human body is through the medium of water (see PARASITIC DISEASES).