Blood donation is
now infamous for transmitting infectious diseases: HIV/AIDS and hepatitis B and
C are the best-known offenders and the blood supply is screened for these
viruses. American trypanosomiasis, or Chagas disease, is caused by a parasite,
and it, too, can be transmitted through organ or blood donation, so we can
add Trypanosoma cruzi, the cause of Chagas disease, to our list of
concerns.
How do You Get American trypanosomiasis?
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| Triatoma infestans is the best known of the kissing bugs. Image by Bärbel Stock; CC BY-SA 3.0 |
The parasites enter
fat and muscle cells and multiply, eventually being released into the blood and
thus distributed throughout the body. In time, they become quite rare in the
blood but continue to live and multiply in organs indefinitely. Should another
hungry reduviid bug feed on the host, there are enough T. cruzi trypanosomes
circulating to pass the parasite to the bug, and subsequently to another human.
Parasites present in donor blood and donated organs will also thrive in their
new host.
Symptoms of American Trypanosomiasis
Early symptoms of
Chagas disease include a painful swelling at the site of the bite, swollen
lymph nodes, high fever, aching muscles, enlarged liver, rash, inflammation of
the heart and swelling of the face and extremities. This stage of the disease
is often severe and dangerous in small children, while symptoms in victims over
five years of age are generally milder and progress to a more prolonged, often
asymptomatic though still destructive, form of the disease.
In chronic Chagas
disease, there is organ damage, particularly enlargement of the heart with
gradual loss of function, and enlargement of the esophagus (megaesophagus) and
colon (megacolon) leading to loss of function in the digestive tract. The
severity of disease varies from person to person, and from one geographic area
to another – when the heart and/or digestive system damage are severe enough,
the patient dies.
Chagas Disease Distribution
The WHO estimates
that between 6 and 7 million people are infected with T. cruzi.
Most of them are in South and Central America, with about 12,000 deaths
attributed to the parasite annually.
With increasing migration of people from endemic areas, incidences of Chagas disease acquired through blood transfusion or organ transplant are increasing, and there is evidence that reduviid bugs in North America are carrying and transmitting the parasite. Thus, Chagas disease has become a matter for concern – an emerging disease – in North America, and both blood and organ donors are now being selectively screened for T.cruzi in both the United States and Canada.
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| Global distribution of Chagas disease. The red area shows where the disease is frequently transmitted by the kissing bug. In the blue area, occasional transmission occurs. In red, blue, and green areas, the disease is also transmitted from mother to fetus, and through blood or organ donation. Derived from a United Nations map. |
With increasing migration of people from endemic areas, incidences of Chagas disease acquired through blood transfusion or organ transplant are increasing, and there is evidence that reduviid bugs in North America are carrying and transmitting the parasite. Thus, Chagas disease has become a matter for concern – an emerging disease – in North America, and both blood and organ donors are now being selectively screened for T.cruzi in both the United States and Canada.
Further reading on Chagas disease
Trypanosoma cruzi may owe its success in humans to the domestication of the guinea pig. I wrote about this in my book Parasites: Tales of Humanity's Most Unwelcome Guests.
Trypanosoma cruzi may owe its success in humans to the domestication of the guinea pig. I wrote about this in my book Parasites: Tales of Humanity's Most Unwelcome Guests.
Schmidt, Gerald D.
and Larry S. Roberts. Foundations of Parasitology 8th Ed. New
York: McGraw Hill, 2009.
WHO. “Chagas disease (American Trypanosomiasis)” Updated March 2017
