FILARIASIS, fil-a-rra-sis, a group of dis eases caused by nematode worms (see NEMA TODA) of the genus Filaria, some species of which are parasitic in man and domestic ani mals. The Filarice are very slender worms, mostly parasitic in subdermal connective tissue and in serous cavities. The developmental his tory is not entirely elucidated, but they seem to undergo indirect development in the body of some crustacean or insect, species of mosquitoes notably serving as intermediary hosts. Under the term filarie sanguinis hominis, old authori ties include the species F. bancrofti, F. diurna, and F. perstans, the last the parasite to which the sleeping-sickness of the negroes in Africa has been attributed. The most important one of these is F. bancrofti, whose numerous em bryos enter the blood through the lymphatics, and are present at night in the blood, although usually absent in the daytime. This worm (the male) is about 1% inches long and from 1-10 to 1-12 of an inch broad. The female is al most twice this size. This parasite may be pres ent in the blood without giving rise to any symptoms, but frequently they block the lymph channels and produce the conditions of elephan tiasis. These forms of lymph-scrotum, and of hematochyluria, exist very extensively in Asia and Africa, and within recent years have been found in cities in the southern United States.
(For lymph-scrotum and elephantiasis, see F-TYPHArrrinsis). In hematochyluria the pa tient, while in excellent health, suddenly passes a large amount of urine of a peculiar whitish or milky-whitish appearance, occasionally bloody; or frequently a fluid resembling chyle, which on settling shows the presence of a blood-clot. This chylnria seems to be intermittent, the pa tient being well for weeks or months at a time, and then passing large quantities of this modi fied urine. The embryos are to be found in this urine. Occasionally there are symptoms of un easiness in the loins and lumbar region, but as a rule the health is not affected. The treatment is prophylactic solely.
Another form of filariasis is a disease produced by F. medinensis. It has been known from time immemorial, and it has been fancied that the plague of fiery serpents which afflicted the children of Israel in the wil derness was really an irruption of such worms. This worm is thought to be bred in the body of some minute aquatic crustacean, as Cyclops, and thence to enter its final host, which may be the horse, dog, wildcat or jackal, as well as man, by the drinking of the water. The form of dis
ease brought about by F. medinensis Is ex tremely common among African negroes. In certain provinces of India sometimes nearly one-half the entire population are affected; and it is known in Russia, Turkestan and Hindu stan. The adult female worm usually finds its way into the subcutaneous connective tissue, generally in the lower extremities, especially in the feet or ankle. It has also been found in the arm, eyelid, tongue, perineum, scrotum and trunk. The presence of the worm is not ap parent until it bores its way to the skin. Here it produces a painful swelling which later be comes irritable and sore, and finally there de velops a suppurating sinus. The worm may be expelled spontaneously from the sore, or it may be taken out in native fashion. F. loa is a sim ilar species, limited in its distribution to the west coast of Africa, where it is not uncom mon, and is introduced into man by means of drinking-water. It is an active worm, passing rapidly through the connective tissue, and is very frequently found in the region of the eye, where it bores its way to the conjuctival sur face. Filaria loa was for a long time consid ered a very rare human parasite but in the last ten years many cases of human infection by this worm have been described. Hitherto consid ered a parasite invading the eye only it has been found in a number of other localities. In fact its presence may be anywhere in the con nective tissues following the bite of an infected insect. It then bores through various tissues of the body, often giving rise to local swellings, named variously, Calabar swellings, etc., and may emerge from any part of the body. In as much as emergence from the eyeball makes a striking difficulty the idea originated that it was an eye parasite. The loa parasite is chiefly a native of Africa. It was introduced into the West Indies, and the chances are that with the very active mingling of races incident to the World War there will be numerous cases in the United States. There are a number of minor filaria parasites the exact nature of which can be ascertained from monographs published.
Consult Stedman, 'Reference Hand-Book Medical Sciences' ; article, 'Nematodes and Manson, 'Tropical ; Nuttall, 'The Role of Insects, etc., in the Spread of Parasitic Disease' ; (Johns Hopkins Hospital Reports, Vol. VIII, No. 1); Braun, 'Thierichen Parasite& (1902).