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Dermatologists identify North Texas leishmaniasis outbreak

September 14, 2007

A team of dermatologists and dermatopathologists at UT Southwestern Medical Center has identified nine North Texas cases of an infectious skin disease common in South America, Mexico and in the Middle East, where it is sometimes referred to as a "Baghdad boil."

Numerous cases of the disease, called leishmaniasis, have been reported in troops returning from Iraq and Afghanistan. But for the first time, cases of this dangerous infection are appearing in North Texas in patients who have not traveled to endemic areas.

The infection causes nonhealing sores that can be the size of a half-dollar or larger and that look like boils. These sores usually last for 6 to 12 months and because they are often mistaken for a staph infection, patients may have been given multiple courses of standard antibiotics without success.

The disease is caused by a single-celled parasite called Leishmania, and special cultures must be done in order to confirm the diagnosis of leishmaniasis.

The identified cases were from Waxahachie, Hillsboro and Glenn Heights, all areas south of Dallas; Tom Bean, Anna, Savoy and Nevada, all north of Dallas; and North Richland Hills.

North Texas doctors must have a high index of suspicion and understand that this organism must now be considered endemic in this area, said Dr. Kent Aftergut, a clinical instructor of dermatology at UT Southwestern and in private practice at Methodist Charlton Medical Center.

"Luckily, all of the leishmaniasis cases in North Texas that have been cultured have grown Leishmania mexicana, which is less dangerous than other forms of the parasite," he said. "It makes skin sores, but the infection doesn't spread and become a full body disease like some of the others species of Leishmania. Usually, if patients have a normal immune system, the sores will resolve in six to 12 months and won't make the patients ill."

In North Texas, doctors suspect that the process leading to human infection begins when a sand fly bites a rodent called the burrowing wood rat, which carries the parasite. When the sand fly later bites a person, the sores may develop, said Dr. Aftergut, who began tracking cases in North Texas after identifying the ailment in a patient who had been simply working outside in his yard and had no travel history to areas of infection.

"If a patient has been in Iraq or another known endemic area, we are very used to looking for leishmaniasis. But in the past, you just would not have suspected it in a patient living in North Texas with no travel history. This is why I think it's important to get the word out to other health-care professionals," Dr. Aftergut said.

For many years sporadic cases have been seen in South Texas. But no one has ever reported cases this far north, Dr. Aftergut said. He said this may be due to a movement in either the burrowing wood rat or the sand flies that transmit the infection to humans, although the reason for this movement is unclear.

"There are nine cases of leishmaniasis in North Texas residents who had no travel history in the last two years," said Dr. Aftergut. "This is very strong evidence that the areas we need to consider endemic are moving north."

Dr. Aftergut said he believes that rural areas are more at risk due to their proximity to wooded areas, where the burrowing wood rat and sand flies are more likely to be found.

Dr. Aftergut said using insecticides, bug repellant and protective clothing while working in areas where sand flies might be present should help reduce exposure. Once bitten, there are two types of medicines to treat the infection; however, one treatment can be toxic to some patients.

Doctors who identify a possible case of leishmaniasis should contact the Centers for Disease Control and Prevention, which can assist with the special tests needed to verify it. The federal agency also is tracking cases, Dr. Aftergut said.

UT Southwestern Medical Center