Chagas disease - a new public health threat for Americans?

Chagas Disease - a parasitic infection that can cause severe heart disease and death if not caught and treated early - affects millions of people worldwide, mainly in Latin America. Now, new research suggests it is increasingly being seen in the southern US and poses an emerging potential public health threat for Americans.

Experts say a large area of the southern US faces a tangible but mostly unrecognized risk of contracting Chagas disease.

Researchers from Baylor College of Medicine in Houston, TX, presented the results of their work on 4th November at the 63rd Annual Meeting of the American Society of Tropical Medicine and Hygiene (ASTMH) in New Orleans, LA.

They say a large area of the southern US faces a tangible but mostly unrecognized risk of contracting Chagas disease.

Chagas disease (American trypanosomiasis) is caused by Trypanosoma cruzi, a protozoan parasite related to the African Trypanosoma that causes sleeping sickness (African trypanosomiasis).

The infection occurs via bloodsucking bugs that carry the parasite. The bugs are sometimes called "kissing bugs" because they feed on people's faces during the night. The parasite transfers to the new host via the feces of the kissing bug. This is deposited on the skin and then gets into the bloodstream either via the bite, or through other means, for instance when the person scratches the bite site.

Once the parasite enters the bloodstream, it travels to the heart and settles there, and damages the heart muscle. Up to 30% of infected people have chronic heart disorders and up to 10% get sick with other health problems including digestive and neurological disorders.

Many infected people do not realize they have Chagas until symptoms become severe - and even then, they can be misdiagnosed as other conditions, such as cardiovascular disease.

Chagas disease - which can also be spread through the blood supply from donors infected with the parasite - can be cured if caught early. It affects about 8 million people worldwide, mostly in Mexico, Central America and South America.

Cases of Chagas disease increasing in Texas

However, the Baylor researchers say cases of Chagas disease are increasingly being seen in Texas, and at higher levels than previously thought. They also believe a high percentage of American cases have become infected inside the US.

The team reports some of its findings in the American Journal of Tropical Medicine and Hygiene. Commenting on those findings, and those of other studies they conducted, Baylor epidemiologists say:

"We were astonished to not only find such a high rate of individuals testing positive for Chagas in their blood, but also high rates of heart disease that appear to be Chagas-related. We've been working with physicians around the state to increase awareness and diagnosis of this important emerging infectious disease."

We clinicians are aware that Chagas disease is a "silent killer:"

People don't normally feel sick, so they don't seek medical care, but it ultimately ends up causing heart disease in about 30% of those who are infected.

Chagas disease could be going undetected in Americans due to low awareness

The Baylor team suggests Chagas disease is an emerging public health concern not only for Texas - where their research was conducted - but also for other parts of the US. According to the Centers for Disease Control and Prevention (CDC), kissing bugs are found across half of the US.

In the US, Chagas disease is considered one of the neglected parasitic infections, a group of five parasitic diseases that the CDC have targeted for public health action.

The Baylor team suggests there could be cases of Chagas in Americans who are infected through kissing bug bites that are undiagnosed because of low awareness of the disease among US health professionals.

The team presented the results of several studies to back up their suggestions. One of these, published in the journal Epidemiology and Infection, is an analysis of routine testing of Texas blood donors from 2008 to 2012. Since 2007, all potential blood donors in the US are screened for exposure to the Chagas disease parasite.

From their analysis, the Baylor team found 1 in every 6,500 donors tested positive for the Chagas parasite, which is 50 times higher than the CDC's one in 300,000 estimate of the national infection rate.

In August 2014, the World Health Organization (WHO), the Universitat Politècnica de Catalunya, and other academic centers stated that they are setting up a global scientific database on Chagas disease.

References:

1. Evidence of autochthonous chagas disease in southeastern Texas, Melissa N. Garcia, et al., Am J Trop Med Hyg, doi:10.4269/ajtmh.14-0238, published online 4 November 2014, abstract.
2. Trypanosoma cruzi screening in Texas blood donors, 2008-2012, M. N. Garcia et al., Epidemiology and Infection, doi:10.1017/S0950268814002234, published online 29 August 2014, abstract.
3. American Society of Tropical Medicine and Hygiene news release, accessed 4 November 2014 via EurekAlert.