Chagas Disease Parasite Found in Texas

Chagas disease, once thought to be confined to more tropical areas, may be affecting US patients

(RxWiki News) Chagas disease is usually thought of as a tropical disease, found in places like Guatemala or Brazil. But researchers recently found that the parasite that causes Chagas disease was present in the blood of some Texans.

Houston, TX, began screening blood donors for Chagas disease in 2007. A small study of those blood donors found that some had been infected with the parasite that causes Chagas.

Untreated Chagas disease may lead to heart disease decades later. The study authors said doctors need to start considering Chagas disease when they see unusual cases of heart disease. People who have no other condition that could lead to heart disease, such as high blood pressure or a history of smoking, should be tested for Chagas disease, the authors said.

The parasite Trypanosoma cruzi (T. cruzi) is spread through an insect known as the triatomine bug. T. cruzi may cause heart disease in as many as 30 percent of those infected with the parasite, the study authors wrote.

The study was done by Melissa N. Garcia, MPH, of the Baylor College of Medicine in Houston, and colleagues. They presented a poster on the topic Nov. 4 at the American Society of Tropical Medicine and Hygiene Annual Meeting in New Orleans.

The authors studied 30 Houston blood donors whose blood had screened positive for T. cruzi infection between 2008 and 2012. They re-tested the blood of those patients and asked them to fill out a survey meant to find the source of the infection.

The authors found that 17 of those patients (57 percent) tested positive for Chagas. Among those who had Chagas, seven (41 percent) had a heart problem often seen in patients with Chagas disease, such as heart muscle damage or a severe infection of the heart muscle. The study authors detected these heart problems using electrocardiograms (EKGs) — tests that check for problems with the electrical activity of the heart.

Based on the patients' surveys, the study authors believed that about six of the 17 patients with Chagas (36 percent) had become infected in the US. But past estimates suggested one locally acquired case per every 354,000 cases, Garcia told dailyRx News.

“As you can see, 36 locally acquired cases per every 100 cases [in the United States] is significantly higher than previously reported,” she said.

Many people don’t know they have been bitten by the bug that causes Chagas disease because the swelling at the site of the bite — similar to that of many more harmless bug bites — goes away. Patients may also have mild flu-like symptoms that go away. But if the parasite causes Chagas disease, the disease may slowly cause damage to the heart. Symptoms of this heart damage may not show up until 10 or 20 years later.

The triatomine bug is also known as the kissing bug because it often bites people on the face while they sleep. Chagas disease is caused by a parasite found in the feces of the kissing bug, and the bug often passes feces when it bites. If it bites the person near an opening in the skin or near the eyes or mouth, the person could become infected.

The kissing bug is commonly found in South and Central America. But it has also recently been found in parts of the southern US, such as Georgia, Louisiana and Texas, according to the Centers for Disease Control and Prevention (CDC).

"Recently, a few cases of Chaga's have been suspected to have been acquired in the US," said Steven G. Davis, MD, an infectious disease specialist with Baylor Medical Center at Irving, TX, in an interview with dailyRx News. "However the housing conditions that would permit 'kissing bug' entry to dwellings are less common here. Further the types of triatomine bugs in US may be less effective at transmitting the parasite than the common insect vectors in South America."

The study authors said US doctors — particularly those in southern states — should consider Chagas disease when treating patients with heart problems. Doctors should look for people who do not have other risk factors for heart disease, such as high blood pressure, and test them for the parasite — even if the patient has not been to a country where Chagas is common, the authors noted.

Less than half of people with Chagas go on to develop heart disease. Treatment is believed to be most effective if caught early in heart disease progression, Garcia said.

“However, we are concerned that US citizens might be going undiagnosed with this disease for years due to lack of physician awareness,” Garcia said.

If the parasite is caught early on, medication may kill it. But this medication isn't widely available, Dr. Davis noted.

"Anti-parasitic treatments are most helpful for more recent infection," Dr. Davis said. "Many of the late manifestations of Chaga's like heart failure and dilated esophagus may not respond to these medications. The two anti-parasitic medications that are used to treat Chaga's are Benznidazole and Nifurtimox. These medications are only available through the CDC for use under investigational protocols. The available therapies can cause nerve, skin and stomach side effects so new less toxic drugs would be welcomed."

These findings will be published in the American Journal of Tropical Medicine and Hygiene, according to a press release.

The Cardiovascular Research Institute at Baylor College of Medicine funded the study. The authors disclosed no conflicts of interest.

Review Date: 
November 3, 2014