(4) Acanthocheilonema perstans. This parasite does not seem to give rise to clinical manifestations except possibly to cause an irregular fever.
The adult is found in the retroperitoneal connective tissue or fat, while the sheathless, blunt-tailed embryo is found in the blood, both by day and night, hence perstans. The adult forms are found in the tissues behind the abdominal aorta and at the attachment of the mesentery.
(5) Dracunculus medinensis. The female of this parasite, about 36 inches long and 1/15 inch in diameter, travels to the subcutaneous tissues of the extremities and boring through the skin causes a small surface erosion.
An unimportant filarial worm which has been found only in the West Indies and British Guiana is known as Filaria demarquayi or F. ozzardi. The embryos have sharp tails and are without a sheath. The parasite is not known to produce symptoms.
History
Filaria bancrofti.—While elephantiasis was frequently described by ancient writers yet the confusion between Elephantiasis Graecorum, a term applied to leprosy, and Elephantiasis Arabum, or the filarial condition, made the question of the nature of the skin thickenings very indefinite.
The thickenings due to leprosy and those connected with filariasis were separated clinically by observers during the 17th and 18th centuries, Hilary, in 1750, having accurately described the progress of that form of elephantiasis connected with elephantoid fever and lymphangitis. In 1863 Demarquay discovered filarial embryos in the exudate of a chylous hydrocele and three years later Wucherer, in Brazil, found similar nematode larvae in the urine of a case of haematochyluria. Commencing with the year 1863 Lewis carried on a series of investigations in Calcutta in which he found these embryos not only in the urine of patients with chyluria but as well in the lymph and blood of those affected with elephantiasis. He called the parasite Filaria sanguinis hominis, a name still frequently employed by medical writers.
In 1876 Bancroft, in Australia, discovered the adult filarial worms in a lymphatic abscess, hence the name Filaria bancrofti. In 1878 Manson, in China, demonstrated the mosquito transmission of the disease as well as the phenomenon of nocturnal periodicity. Manson’s idea, however, was that the fully developed embryo escaped from the body of the infected mosquito at the time of the death of the insect and that man contracted the infection in drinking water.
The investigations of Low and more recently those of Fülleborn and Bahr and others have shown that the larvae escape by way of the mosquito’s proboscis and enter the skin of man.
Loa loa.—The knowledge of a filarial infection of the region of the eye seems to date from the time of Magellan. Although the disease is now confined to the west coast of Africa, cases were reported from the West Indies by Mongin and Bajou during the 18th century. These cases were in slaves who had contracted the infection in Africa.