Elephantiasis

From VOA Learning English,

this is the Health Report.

Scientists are working on ways to

stop a disease

that threatens one-fifth of the world's population.

Over 120 million people

are infected with lymphatic filariasis,

also known as elephantiasis.

The disease is found mainly in Southeast Asia and Africa.

It effects the lymphatic system

which is a major part

of the body's natural defense for fighting disease.

Elephantiasis can cause swelling

or enlargement of skin and tissue.

The cause is a tiny worm

that enters and lives in lymphatic tubes

for six to eight years.

Scientists say

they have been able to demonstrate

that the most common cause of elephantiasis

can be stopped.

They are urging those at risk

to sleep under nets

treated with chemicals

that kill a common insect - the mosquitoes.

Lisa Reimer teaches at the Liverpool School

of Tropical Medicine.

She formerly served in Papua New Guinea,

as part of the team studying the disease.

The team involved researchers from Papua New Guinea,

Britain, Australia and the United States.

Doctor Reimer says

she was surprised at how effective

anti-malaria bed nets covered with insecticide

could be at fighting the disease.

"Filariasis is only picked up

by mosquitoes late in the evening,

so this is the time

when people are more likely to be protected

by their bed nets.

So we found that bed net use actually

is a greater barrier against

filariasis transmission

whereas malaria transmission may still be occurring

outside the times when the user is under the net."

Doctors normally use drugs to fight the disease.

Ms Reimer says doctors in Papua New Guinea

gave the drugs to people of five villages.

She says this treatment nearly ended

the threat from the worm to humans,

but the drugs didn't stop the threat from mosquitoes.

The treated nets

block female mosquitoes from securing blood,

which is necessary for them to reproduce.

The insecticide also cuts the life of the insects in half.

"If we can reduce mosquito-biting rates

then we're able to increase the thresholds

below which the disease prevalence will move to zero.

So by controlling mosquitoes we're making the targets

for the mass drug administration more obtainable."

The World Health Organization (WHO) has

set a goal of stopping lymphatic filariasis

as a public health problem by the year 2020.

The WHO estimates that 1.4 billion people

in 73 countries are at risk of the disease.

Children are often infected,

but they do not show signs of the disease

until later in life.

And that's the Health Report from VOA Learning English.

I'm Bob Doughty.