Home Data Guidance Medical Providers Submission and Testing Resources
Chagas disease, also called American
trypanosomiasis, is caused by infection with Trypanosoma cruzi, a single-celled parasite transmitted by certain
species of blood-feeding insects. The parasite is naturally present only in the
Americas, from most of South America to the southern half of the United States
(U.S.), including all regions of Texas. Human infection occurs commonly in some
parts of Latin America, but relatively rarely within the U.S., mainly due to improved
housing conditions.
The Pan American Health Organization estimates that
approximately 8 million people in Latin America are infected, resulting in about
12,000 deaths per year. The U.S. Centers for Disease Control and Prevention
(CDC) estimates that approximately 300,000 people within the U.S.—predominantly
immigrants from high-risk areas of Latin America—are infected. Human cases acquired
in Texas are uncommon.
Transmission
The T. cruzi parasite is naturally transmitted in the feces of
blood-feeding triatomine bugs (also called reduviid bugs, kissing bugs, or
cone-nosed bugs). The triatomine bug vectors usually become
infected after feeding on an infected animal or, more rarely, a person. After
the organism reproduces in the bug, it can spread to people if the infected bug
defecates while feeding on them, usually while the person is sleeping at night,
and the person accidently rubs the feces into the bite wound, an open cut, or a
mucous membrane.
People
also can become infected through:
- congenital
transmission (from a pregnant woman to her baby)
- blood
transfusion
- organ
transplantation
- consumption of
beverages or uncooked food contaminated with feces from infected bugs
- accidental
laboratory exposure
Chagas
disease is not transmitted from person to person like a cold or the flu or
through casual contact with infected people or animals.
Disease
There are two phases of Chagas disease: acute and
chronic. Both phases can be symptom-free or life-threatening.
The acute phase of disease occurs during approximately the first 8 weeks of
infection. Symptoms, if present, may include:
- fever
- malaise
- body aches
- rash
- headache
- loss of appetite
- vomiting
- diarrhea
- a localized swelling (“chagoma”) where the parasite
entered the body
People with acute illness may also have mild
enlargement of the liver or spleen and swollen lymph nodes, among other
less-common findings. The most recognized marker of acute Chagas
disease is called Romaña's sign, a swelling of the eyelids on the side of the
face near the bite wound or where bug feces were deposited into the eye or
accidentally rubbed into the eye. Symptoms
of acute illness can last weeks to months and then disappear, even without
treatment. The acute phase of disease may go unnoticed because it often causes
no symptoms or only mild symptoms.
The chronic phase of disease follows the
acute phase and includes an asymptomatic form (“indeterminate” or “latent”
infection) and a symptomatic form. The majority of people in the chronic phase
will remain symptom-free for life, but 20-30% will develop symptomatic illness,
including:
- an enlarged heart (cardiomyopathy), heart failure,
altered heart rate or rhythm, or sudden death
- an enlarged esophagus (megaesophagus) or enlarged colon
(megacolon), which can cause difficulties eating or having bowel movements
Medical Evaluation and Treatment
If you think you have Chagas disease, have been
exposed to a triatomine bug, or share risk factors with a family member who has
Chagas disease, contact your medical provider. Your medical provider will conduct
a thorough physical exam, ask you about risk factors for infection, especially
travel to areas where Chagas disease is common, evaluate your heart rhythm, and
order blood tests to determine if you have been infected. If tests show that you
are infected, drugs are available for treatment, however a cure is not always
possible. These drugs may cause significant side effects that some people may
not tolerate.
Blood Donor Testing
Blood banks screen first-time blood donors for
evidence of T. cruzi infection.
Donors testing positive are notified by the blood bank and are advised to
consult their medical provider for evaluation and additional laboratory testing.
Potential blood donors found to be infected with T. cruzi should not donate blood or tissues for the remainder of
their lifetime.
T. cruzi Infection in Dogs and Cats
T. cruzi infection has been reported in
dogs in Texas
and several other states,
including Louisiana and Oklahoma.
Infections in domestic cats have been reported in South America, but not in the
U.S. Although dogs may become
infected anywhere in the state, infection most commonly occurs in Central and South Texas.
Outdoor dogs are at much higher risk due to their outdoor exposure, the
likelihood of infestation of outdoor kennel areas, and the tendency for some
dogs to eat triatomine bugs. Studies
conducted in South Texas
in 1999 found that 7.5% of the stray dogs
tested were positive for the parasite and infection in coyotes has
also been reported. If you think your dog may have been infected, contact your
veterinarian. Your veterinarian will be able to examine your dog and collect
blood samples for laboratory testing. Currently, there are no drugs available
in the U.S. to treat dogs infected with T.
cruzi.
Preventing Chagas Disease
Preventive
measures while traveling to endemic areas include using bed nets treated with long-lasting
insecticides, wearing protective clothing, and applying insect repellent to
exposed skin. In addition, travelers should be aware of other possible routes
of transmission, including blood-borne (i.e. blood transfusion) and food-borne
(ingestion of food and/or drink contaminated with infected bug feces)
transmission.
Recommendations
for reducing the risk of transmission to animals and humans in the U.S.
include:
- keep
yard and kennel areas clean to eliminate habitat for the bugs; remove brush piles,
rock piles, excessive buildup of leaf litter, etc.
- control
rodents to remove a potential food source that may sustain populations of bugs
in the yard
- turn
off outdoor lights at night so that bugs aren’t attracted to the house and yard
- identify
and seal entry points for the bugs into the home and consider the appropriate
use of a long-lasting insecticide
- keep
pet food and water bowls inside to prevent contamination with feces from the
infected bugs
- keep
dog houses and poultry coops clean, fill in crevices where the bugs might hide,
and consider the appropriate use of long-lasting pesticides in and around these
structures
Triatomine Bug Testing Services
DSHS, in conjunction with
CDC, provides testing of triatomine bugs for the presence of T. cruzi. This free service is provided to
Texas residents only. For more information about submitting a bug
for testing, please see http://www.dshs.texas.gov/idcu/health/zoonosis/Triatominae/.