Chagas Disease

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Additional website information regarding Chagas Disease:

Centers for Disease Control and Prevention

The Pan American Health Organization

World Health Organization, Special Programme for Research and Training in Tropical Diseases

Medline Plus, The National Library of Medicine

The ChaggaSpace Group

University of Florida IFAS Extension

Chagas Disease is endemic in Mexico, Central, and South America, where 16-18 million people are infected with the parasite causative of the disease, and causes 21,000 deaths every year. Moreover, 120 million people are at risk of becoming infected.

In the southern United States, six (6) cases of locally transmitted Chagas Disease have been reported (the most recent in 2006 in Louisiana, 1 case in Tennessee, 3 in Texas, and 1 in California.) It is possible, however, that some cases of Chagas Disease in the U.S. might have been overlooked because the early phase of the infection is often asymptomatic. Indeed, the Southwest U.S. is at potential risk of transmission of the disease because infected kissing bugs and mammals (such as packrats, mice, armadillos, raccoons, squirrels, bats, opossums, skunks, foxes, and dogs) exist in the region.

Chagas Disease is caused by a protozoan parasite, Trypanosoma cruzi, which in the insect lives inside its digestive tract. The parasite is transmitted to humans when feces or urine (which are usually deposited during feeding or shortly thereafter) from infected bugs come into contact with damaged skin or oral and/or eye mucous membranes, or when the victim rubs the itchy wound site and brings the feces or urine into the bite site. Since the bite is painless and occurs at night, most people never know they have been bitten. Although mainly a vector-borne disease, humans can also acquire Chagas Disease through blood transfusion. Acute infection can be lethal, but the disease usually evolves into a chronic stage, accompanied in 25-30% of cases by severe debilitation and ultimately death. During the 30-40-day acute phase of the infection it is possible to treat the patient, but often the drugs are not well tolerated and furthermore, most cases are not diagnosed because the infection involves nonspecific symptoms (e.g. rushes of fever, fatigue).

After the acute phase, the disease enters an asymptomatic, chronic phase characterized by a lifelong, low-grade parasitemia. Up to 30% of the infected people develop life-threatening illnesses of the cardiac and gastrointestinal systems. Neither a vaccine for prevention nor an effective cure for chronic Chagas Disease currently exists. Thus, control of the disease depends mainly on early detection and eradication of kissing bugs through use of insecticides. In future, insect control strategies should be enhanced by trapping methods.

Unfortunately, most available information about infection rates by T. cruzi in North American kissing bugs date to more than 50 years ago. The average infection rates (i.e., considering the most abundant species altogether) in kissing bugs from California, Arizona, New Mexico, and Texas were reported to be 21%, 7%, 3.4%, and 7%, respectively. A systematic study carried out in 1964 in what is today suburban Tucson found that 7.5% T. rubida (the most abundant species) and 19.5% of T. protracta were infected with T. cruzi.

Why is Chagas Disease in humans so rare in the U.S.? Possible reasons might be the lack of suitable domestic dwellings for the insects, low numbers of those insects inside houses, possible misdiagnosis of the infection, and more importantly, apparently delayed defecation times, that is, defecation far from the person bitten.