Lymphatic Filariasis
- Lymphatic filariasis [lim-FA-tick fil-uh-RY-uh-sis]
is a disease of the tropics. It is caused
by infection with any of several round, thread-like
parasitic worms. The most common is infection
with a parasite that lives in the lymph system.
This is called lymphatic filariasis.
- The parasite is spread from person to person
by infected mosquitoes.
- Long-term exposure and repeated infections
can cause severe damage to the lymph system
and serious, debilitating complications.
- Prevention centers on controlling mosquito
populations in communities and avoiding mosquito
bites.
What is lymphatic filariasis?
Filariasis is an infection with any of several
round, thread-like parasitic worms. The most
common type of filariasis is infection with
a parasitic worm that lives in the human lymph
system. This is called lymphatic filariasis.
What is the infectious agent that causes
lymphatic filariasis?
Filariasis is caused by three types of parasitic
worms: Wuchereria bancrofti, Brugia
malayi, and Brugia timori.
Where is lymphatic filariasis found?
Lymphatic filariasis is a disease of the tropics.
Wuchereria bancrofti, the most common
filariasis parasite, is found in Africa, India,
Southeast Asia, the Pacific islands, the Caribbean,
and South America. The Brugia malayi
and Brugia timori parasites are found
in Southeast Asia.
How is lymphatic filariasis spread?
Filariasis is spread from infected persons
to uninfected persons by mosquitoes. Adult worms
live in an infected person's lymph vessels.
The females release large numbers of very small
worm larvae, which circulate in an infected
person's bloodstream. When the person is bitten
by a mosquito, the mosquito can ingest the larvae.
These develop in the mosquito and can then be
spread to other people via mosquito bites. After
a bite, the larvae pass through the skin, travel
to the lymph vessels, and develop into adults,
which live about 7 years. Then the cycle begins
again.
What are the signs and symptoms of lymphatic
filariasis?
Most of the signs and symptoms of filariasis
are caused as a consequence of the adult worms
living in the lymph system. Tissue damage caused
by the worms restricts the normal flow of lymph
fluid. This results in swelling, scarring, and
infections. The legs and groin are most often
affected.
How soon after exposure do symptoms appear?
Symptoms can appear 5-18 months after a mosquito
bite.
How is lymphatic filariasis diagnosed?
Filariasis larvae can sometimes be detected
in blood.
Who is at risk for lymphatic filariasis?
Those most at risk are people who live in or
stay for a long time in tropical areas where
the disease is common. Short-term tourists rarely
get filariasis. Getting an infection with symptoms
usually requires several mosquito bites over
a long period of time.
What complications can result from lymphatic
filariasis?
Lymphatic filariasis is rarely fatal, but it
can cause recurring infections, fevers, severe
inflammation of the lymph system, and a lung
condition called tropical pulmonary eosinophilia
(TPE). In about 5% of infected persons, a condition
called elephantiasis causes the legs to become
grossly swollen. This can lead to severe disfigurement,
decreased mobility, and long-term disability.
Testicular hydrocele is a disfiguring enlargement
of the scrotum.
What is the treatment for lymphatic filariasis?
Treatment consists of: 1) medicine to kill
circulating larvae and adult worms, 2) soap
and water and skin care to prevent secondary
infections, and 3) elevation, exercises, and,
in some cases, pressure bandages to reduce swelling.
How common is lymphatic filariasis?
At least 120 million people in 73 countries
worldwide are estimated to be infected with
filariasis parasites. The most widespread is
Wuchereria bancrofti, which affects about
100 million people in Africa, India, Southeast
Asia, the Pacific islands, South America, and
the Caribbean. The Brugia malayi and
Brugia timori parasites affect about
12 million people in Southeast Asia.
Is lymphatic filariasis an emerging infectious
disease?
Yes. Lymphatic filariasis is among the world's
leading causes of permanent and long-term disability.
The number of infected persons is increasing
worldwide, due in large part to unchecked urbanization
in many areas where the parasite is common.
How can lymphatic filariasis be prevented?
There is no vaccine for filariasis. Prevention
centers on mass treatment with anti-filariasis
drugs to prevent ingestion of larvae by mosquitoes,
public health action to control mosquitoes,
and individual action to avoid mosquito bites.
To avoid being bitten by mosquitoes:
- If possible, stay inside between dusk and
dark. This is when mosquitoes are most active
in their search for food.
- When outside, wear long pants and long-sleeved
shirts.
- Spray exposed skin with an insect repellent.
Where can I find more information about
lymphatic filariasis?
WHO
website
This fact sheet is for information only and
is not meant to be used for self-diagnosis or
as a substitute for consultation with a health-care
provider. If you have questions about the disease
described above, consult a health-care provider.