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Source: Centers for Disease Control and Prevention

The kissing bug causes the transmission of Chagas.

Parasitic disease on the rise in the U.S.

by J. Okray
June 02, 2010

Chagas disease is an often lethal parasitic disease that's found predominantly in South American countries and is spreading in the United States, threatening thousands of lives.   

The Centers for Disease Control and Prevention estimates that 300,000 people in the U.S. have Chagas, an illness that leads to heart failure. This number is based on blood donor tests and immigration records because there is currently no federal regulation for any testing.  

"I would say it is probably in that range," said Dr. David Engman, professor of pathology and microbiology at Northwestern University. "If anything, I would say it may be an underestimate because, if you are an illegal immigrant, you may not want to donate blood because they register you."

Engman said the incidence of the illness among blood donors does not necessarily reflect the population at large and immigration records are not likely to have records regarding Chagas.  

Since 2007, the CDC reports 65 percent of U.S. blood banks have been testing for Chagas, though it’s not required. CDC has confirmed 1,200 positive cases in units of blood to date, making the risk of being infected from a blood transfusion low. However, Engman said there is "still a lot of contaminated blood out there."

This disease has no cure and is prevalent in South America, afflicting between 8 and 20 million people. It can take years for heart symptoms to appear.  

Chagas is caused by a parasite, Trypanosoma cruzi, and is transmitted primarily from the "kissing bug," blood or organ transfers and breast milk. T. cruzi lives in the digestive systems of the insects and is transmitted to humans through contact with the insect's feces, not bites. 

T.cruzi causes a substantial disease burden in the U.S. according to the Infectious Diseases Society of America. The society estimates 30,000-45,000 cardiomyopathy cases and 63-315 congenital infections occur annually in the U.S. because of Chagas. 

Approximately 30 percent of those infected will develop Chagas-caused heart problems (often decades after infection), which results in swelling of the heart. Eventual death results without heart treatments including pacemakers, valve surgery or a transplant.

There is little that can be done once a person is infected, except in some acute, immediate onset cases of transmission to children. In these instances, a drug called benznidazole has been successful in destroying the parasite. This drug is not suitable for adults because of side effects and lower success rates of usage, according to Engman. He said it is a dangerous drug shown to cause lymphoma in rats. 

A small percentage of those who develop Chagas may experience digestive or neurological problems. There is no vaccine for the disease but it is detectable through a blood test.

In most cases, there are no immediate symptoms for Chagas, except for swelling in the area of transmission in acute cases. The best way to prevent infection is to wash raw fruits and vegetables, especially if they are from South America or Mexico.

If traveling to affected areas, Engman cautions to use plenty of insect repellent and bring bug nets for sleeping.