Lymphatic filariasis

background

Lymphatic filariasis, also known as elephantiasis, is a parasitic infestation of nematodes. Nematodes are worms, commonly known as roundworms because of their shape. The nematodes that invade the human body and damage internal structures are Brugia malayi, Brugia timori,and Wuchereria bancrofti.
The disease is transmitted from human to human by certain species of mosquitoes. Mosquito species that can transmit the disease are Culex quinquefasciatus mosquitoes and some Anopheles species; Brugia roundworms are primarily transmitted by Mansonia mosquitoes.
If a human is infected, he or she carries larvae, known as microfilariae, in the bloodstream. A larva is the transitional form of a worm between the egg and adult. If an infected person is bitten by a mosquito that is capable of carrying the microfilaria, these organisms then develop within the mosquito to an infective stage. The process takes one to three weeks before the larvae travel to the mosquito's biting mouth parts. When the mosquito bites another human, the larvae enter that person's bloodstream, thus completing the infectious cycle.
The microfilariae travel from the bloodstream into the lymphatic system, which is a network of vessels that maintain a delicate fluid balance between body's tissues and the bloodstream. They lodge in the lymphatic system where they mature into adult worms. These worms live for four to six years and produce millions of immature microfilariae that circulate in the blood.
The adult worms block the normal flow of lymphatic fluid, damaging the lymphatic system. This blockage produces tremendous enlargement of the arms, legs, or genitals, which may swell up to several times their normal size. The worms also lodge in the kidneys, causing damage to this organ.
More than 120 million people have lymphatic filariasis and more than 40 million of those individuals are seriously disfigured and incapacitated. Affected body parts include the arms, legs, genitals, and breasts. Tremendously swollen legs and genitals make walking difficult. Kidney damage caused by filariasis can cause serious health problems and even death. More than one billion people in developing countries are at risk of infection.
Of those currently infected, about one-third live in Africa, about one-third in India, and the rest in South Asia, the Americas, and Pacific Islands. In these regions, affected individuals usually live in poor, underdeveloped communities.

Related Terms

Brugia malayi, Brugia timori, elephantiasis, infection, mosquito, nematode, parasite, parasitology, roundworm, Wuchereria bancrofti.

research

Current research is focused on vaccines to prevent the disease, different drug combinations that better treat the infection, and pesticides to kill the mosquitoes that carry the worms. Filarial glutathione-S-transferase is currently under investigation as a possible vaccine. This substance is an enzyme that has been shown to inactivate and kill the microfilariae and adult female worms.
The nematode Brugia malayi is of particular interest for current research because of evidence that infection with the organism results in marked reduction (down-modulation) of the infected human's or host's immune response. This is accomplished by secretions from the parasites, which are essentially an expression of its genome. Analyzing this genome should provide important new understanding of the parasite's biology.
Doxycycline is under investigation as a supplementary agent to use with albendazole, DEC, or ivermectin therapy. Doxycycline is an antibiotic effective against a large variety of bacteria. It appears to boost the effect of antiparasitic drugs used to treat lymphatic filariasis and malaria.
The leaf extracts of Acalypha indica are under investigation as a potential pesticide that kills mosquito larvae.

future research

Future research is focused on the same areas as current research: vaccines to prevent the infection, more effective treatment for infected individuals, and pesticides to kill the mosquitoes that transmit the nematodes from person to person.
A major focus of future research will be in the area of genomics. As knowledge increases, effective treatment of the condition should follow.