A Parasite in the Blood Supply

Trypanosoma cruzi, Found in Blood and Organs, Causes Chagas Disease

Mar 21, 2007

American sleeping sickness, or Chagas disease, is caused by a parasite, and it can be transmitted through organ or blood donation.

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. Now we can add Trypanosoma cruzi, the cause of Chagas disease, or American sleeping sickness, as a risk in some localities - a parasite in the blood supply.

For people living in areas where Trypanosoma cruzi is endemic, Chagas disease usually starts with an insect bite: the reduviid bug, also known as the triatomid bug or kissing bug, bites a human taking a blood meal. As blood goes in at the mouth end, the bug defecates at the other end leaving a fecal droplet full of infectious parasites on the skin. Later, when the bite itches and the victim scratches, the tiny parasites are rubbed into the wound and gain access to the tissues under the surface of the skin.

The parasites enter fat and muscle cells and begin to multiply, eventually being released into the blood and thus distributed throughout the body. They eventually become quite rare in the blood, but continue to live and multiply in organs. The infection persists indefinitely with live and infectious parasites in both blood and organs. Parasites can be passed on when the reduviid bug bites again, this time taking in parasites with its meal and subsequently passing them on to the next person it bites. Parasites can also be passed on via blood transfusions or organ donations.

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 are severely affected, the patient usually dies.

In South America and Central America, nearly 20 million people are infected with T. cruzi, with about 45,000 deaths attributed to the parasite annually. There is a growing risk of this parasite in the blood supply, particulaly in the United States. With increasing migration of people from endemic areas, incidences of Chagas disease acquired through blood transfusion or organ transplant are increasing, and screening for Trypanosoma cruzi in blood and organ donors is becoming a pressing issue.

Sources:

Garcia, Lynn S. and David A. Bruckner. Diagnostic Medical Parasitology 3rd ed. Washington: ASM Press, 1997.

Schmidt, Gerald D. and Larry S. Roberts. Foundations of Parasitology 6th Ed. Boston: McGraw Hill, 2000.

The copyright of the article A Parasite in the Blood Supply in Human Infections is owned by Rosemary Drisdelle. Permission to republish A Parasite in the Blood Supply in print or online must be granted by the author in writing.