Tropical disease diagnosed in La.

January 23, 2007

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A Loyola University researcher has found in Louisiana a human case of an insect-spread disease that is rare in the United States but infects as many as 12 million people in Central and South America.

It was found in a woman who lives in a rural part of the New Orleans metropolitan area in a house without air conditioning that offered easy access for the bugs that carry a parasite that causes the disease. It is just the fifth confirmed case of chagas (pronounced SHA-gas) disease spread by an insect bite in the nation. Five other cases have been blamed on infected organ transplants or blood infusions.

The infection can cause heart disease decades after the first bite.

“I think the people’s natural reaction is alarm. Here’s this tropical disease showing up in Louisiana,” said Patricia L. Dorn, an assistant professor of biology at Loyola. She said she and others specifically asked State Epidemiologist Dr. Raoult Ratard whether chagas might be a public health threat and he said no.

However, because it is so endemic south of the border with Mexico and there are so many immigrants from Central and South America now in the United States, the nation’s blood supply will soon be screened for the disease, Dorn said.

Only 20 to 30 percent of those bitten by infected bugs will develop chagas disease, Dorn said.

The woman who was confirmed as a chagas patient was living in “a very open house. They have chosen to live with nature,” Dorn said, “but most people are not living in the types of homes that would invite the bugs in. The bugs don’t have ready access.”

The woman showed no symptoms at all. She had been bitten by a lot of bugs and had called in an exterminator, who found the problem was a small insect species, triatomines, also known as the “kissing bugs.”

The bugs enter homes at night and usually bite people on the only part of their body often exposed when they are sleeping — the face, hence the name “kissing bug.”

The bugs feed on blood, like mosquitoes, and often defecate shortly after eating, dropping the parasite they carry in their bodies on to the victim’s face. Scratching and rubbing the bite can push the parasite into the wound or into the mouth, nose or eyes, where it can get into the blood stream and infect someone. It is also possible to ingest the parasites in food or drink contaminated by the bugs.

Once the exterminator told the woman her home was infected with kissing bugs, she then did some Internet research and realized she may have been infected with chagas. She contacted health officials, including Dawn Wesson of the Tulane University School of Heath and Tropical Medicine. Wesson knew Dorn specialized in researching the disease and worked with Dorn on the case.

Chagas is found in animals also be bitten by the bugs. It has been present in animals in the United States for thousands of years, Dorn said.

In Louisiana, studies done more than a decade ago showed about 40 percent of the opossums and armadillos in Louisiana carried the parasite and 2 percent to 5 percent of the dogs also were carriers. Dorn said more recent work by LSU School of Veterinary Medicine researcher Trixia Nieto showed 20 percent to 30 percent of dogs in the Atchafalaya Basin area are infected with the parasite and the disease, Dorn said. That is one of the several “hot spots” for the parasite around the state, she said.

Dorn said she recently read where 100,000 to 650,000 people in the United States, mostly natives of Central and South America, are believed to be infected with chagas.

The U.S. Centers for Disease Control reported the bugs are found in houses made from materials such as mud, adobe, straw, and palm thatch. During the day, the bugs hide in crevices in the walls and roofs. During the night, when the inhabitants are sleeping, the bugs emerge.

Two recent cases resulted from organ transplants in Los Angeles, Dorn said. Pilot programs to screen blood supplies showed that in Los Angeles, one in 7,500 units of blood was tainted with the disease and in Miami one unit in 9,000 units of blood was infected by chagas, Dorn said.

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