health

An Ancient, Widespread Disease

Elephantiasis was known to the early Greeks and Romans. It is a tropical
or subtropical disease, occurring where many kinds of disease-carrying
mosquitoes are found: South America, Cuba, Puerto Rico, West Indies,
Africa, Spain, Turkey, Asia, Australia, and many South Pacific Islands.
About 100 million people worldwide are affected.

The Mosquito Carrier

Insects that carry diseases are known as vectors, and several species of
mosquito are vectors of Wuchereria bancrofti, 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.


Lymphedema

The lymphatic system is a complicated network of
very fine tubes, about the diameter of a needle, which crisscross body
tissues to collect a fluid called lymph. Lymph is a milk-like substance
(containing white blood cells, proteins, and fats) that plays an important
role in absorbing fats from the intestine, in fighting infections, and in
the proper functioning of the immune system. Lymph is returned to the
bloodstream via many vessels known as lymphatics. At various points, the
lymphatics drain into masses of tissue known as lymph nodes or glands.
If a blockage occurs, fluid may collect in the tissues, causing a type of
swelling known as lymphedema (limf-e-DEE-ma). In the lymph system
draining the legs, for example, few connections exist, and the legs often
are a site of swelling when lymphedema occurs.

Lymphatic filiariasis

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 can cause the
appearance of an elephant’s leg. However, 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.