Elephantiasis (el-e-fan-TY-a-sis), the medical name of which is lymphatic filariasis, is the result of a tropical worm injection called filariasis (fil-a-RY-a-sis). When infected mosquitoes transmit the parasitic worm Wuchereria bancrofti to people, the worm blocks the lymphatic system, which causes swelling in the legs or other parts of the body, making these body parts appear large and puffy, or elephantlike. Elephantiasis is not elephant man disease, which is an inherited condition with completely different causes and symptoms.
Elephantiasis is an ancient disease known to the early Greeks and Romans. It is seen most often in the tropics or subtropics, occurring where many kinds of disease-carrying mosquitoes are found: South America, Cuba, Puerto Rico, the West Indies, Africa, Spain, Turkey, Asia, Australia, and many South Pacific Islands.
Insects that carry diseases are known as vectors, and several species of mosquito are vectors of Wuchereria bancrofti, which is the nematode worm that causes elephantiasis. When a Culex (KYU-lex), Anopheles (a-NOF-e- LEEZ), Aedes (ay-EE-deez), or Mansonia (man-SO-ne-a) mosquito carrying the Wuchereria bancrofti organism bites a human, the mosquito may inject worm larvae * into the body. The tiny larvae then may make their way into the lymph glands and the lymphatic system.
Worm larvae that make their way into lymph vessels can mature into adult worms. Male worms are long and slender, about 4 to 5 centimeters long, and 0.1 millimeter in diameter. Female worms are much larger, 6 to 10 centimeters long, and about three times wider than the males. The adults make their home mostly near the lymph glands in the lower part of the body. The adult female releases eggs enclosed within an egg membrane (microfilariae), and the microfilariae (mi-kro-fi-LAR-ee-i) develop into larvae to continue the life cycle.
In most parts of the world, microfilariae are at their peak in the blood during the night. The worms restrict the normal flow of lymph, resulting in swelling, thickening of the skin, and discoloration. This action, when it affects the legs, can cause the appearance of an elephant's leg. The swelling of elephantiasis usually does not occur until a person has been bitten by the disease-carrying mosquitoes many times, and has had years of exposure to infected mosquitoes.
About 120 million people worldwide are affected.
Elephantiasis is not contagious or transmissible by contact from an infected individual to another person. Even in regions of the world where elephantiasis is present, it is rare, and contact with a sick person is not a method for spreading the disease. In fact, simply being bitten by an infected mosquito is not sufficient for developing the disease, which likely requires both infection by the worm and some individual susceptibility (such as a problem with the immune system) to develop.
In addition to the characteristic swelling, people with this disorder sometimes have bouts of fever and headache. Their swollen limbs may also become infected. Elephantiasis commonly causes marked swelling of the scrotum in males.
Doctors may order a blood test because microfilariae can sometimes be detected in the blood when using a microscope. Often, doctors diagnose the disorder based on symptoms and the patient's medical history, after ruling out other disorders with similar symptoms.
Because elephantiasis is found mainly in poorer countries, money for research into the cure and prevention of the disease has been limited. Effective preventive efforts include large-scale annual dosing of albendazole together with either ivermectin or diethylcarbamazine citrate, and spraying to kill mosquitoes.
See also Filariasis • Parasitic Diseases: Overview • Roundworm Infection
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* larvae (LAR-vee) are the immature forms of insects or worms that hatch from an egg.