More than 300 US soldiers in Iraq have been diagnosed with the parasitic skin disease leishmaniasis, which is expected to infect nearly 1,000 soldiers by the end of 2004. “This is probably the largest outbreak of leishmaniasis that the US military has ever seen,” says Lt. Col. Peter Weina, director of Leishmania diagnostics at Walter Reed Army Medical Center.

Known in Iraq as the 'Baghdad boil', the cutaneous form of the disease is transmitted by the bite of sandflies carrying various species of the protozoan Leishmania, and causes craterlike skin lesions. Leishmaniasis is the “major medical issue” facing troops in Iraq, says Lt. Col. Russell Coleman, assistant chief of entomology at Walter Reed.

Most soldiers were infected during the sandfly season that began in April 2003, but did not show symptoms until recently because of the disease's long incubation period. There have been no cases reported thus far of the more serious visceral form of leishmaniasis, which affects the liver and spleen and can be fatal.

The standard treatment for the skin disease, GlaxoSmithKline's Pentostam, has not been approved by the US Food and Drug Administration, but is available to soldiers and civilians through an Investigational New Drug protocol. Soldiers are sent to Walter Reed for treatment because potentially severe side effects require that the drug be administered under strict controls.

More than a million new cases of cutaneous leishmaniasis are reported worldwide each year, with current large outbreaks in Sudan and Afghanistan. As a result, the availability of Pentostam is limited and the Army is investigating alternative treatments for the disease.

Although vaccines for leishmaniasis are in early development, an effective one is “a long way off,” says Lt. Col. Weina.

To prepare for the return of the sandfly season in April, the Army has deployed medical units in Iraq to control insects and animals that may act as reservoirs for the disease, and to educate soldiers about preventive measures. “Living conditions certainly play a large role in this because there is no drug you can take to prevent the disease,” says Lt. Col. Coleman. “All you can do is keep that infected sandfly from biting the soldier.”