An outbreak of a tropical disease caused by sand fly bites that leaves disfiguring skin sores has hit Afghanistan, with tens of thousands of people infected, health officials said on Friday.

Cutaneous leishmanisis is a parasitic disease transmitted by the female phlebotomine sand fly, an insect only 2-3 millimeters long that requires the blood of humans or animals so its eggs can develop. Treatable with medication and not life-threatening, cutaneous leishmanisis can leave severe scars on the bodies of victims.

The disease threatens 13 million people in Afghanistan, the World Health Organization said, and many impoverished Afghan victims can’t afford the medication to treat it.

In Kabul, described by the WHO as “the world capital of cutaneous leishmaniasis, the number of cases jumped from an estimated 17,000 a year in the early 2000s to 65,000 in 2009, WHO said.

Peter Graaff, WHO representative to Afghanistan, told AP on Friday that the stigma and shame attached to the disfiguring disease results in underreporting, and the number of infected people is likely much higher.

“This number is likely to be the tip of the iceberg as cases are grossly underreported,” said Graaff.

An outbreak has occurred in a small village in western Herat province’s Kohsan district with 63 people infected since August, Graaff said. The cause of the outbreak was unknown and a WHO team has been dispatched to investigate, he said.

The insects thrive in unsanitary conditions such as piles of garbage and debris and proliferate from June to September. The sand flies bite at night, though using bed nets can keep them away. As the disfiguring sores grow larger, many suffer social stigmatization.

“The high cost of treatment makes it difficult to integrate anti-Leishmaniasis drugs,” said Dr. Suraya Dalil, acting minister of public health. “I urge donors to take this cause seriously, as it causes unnecessary suffering amongst a large number of Afghans.”

According to the WHO as many as 12 million people are infected worldwide with the disease, with about 1 million to 2 million new cases annually.

Online-

http-//www.who.int/leishmaniasis/en/