Season 4, Episode 7: Hearts and Minds
David testifies as expert witness at a hearing about a drug called Lefalin, which appears to be connected to an increased risk of congestive heart failure. Virologist Enuka Okimba thinks the drug causes increased virus replication that leads to heart failure, but when NorBAC investigates they find that a lowered immune response caused by the drug triggers an underlying case of Chagas disease in the affected patients. The source of the Chagas infections was traced back to a batch of infected sugar cane juice used in a health drink.
 Image provided courtesy of Shaftesbury Films. |
 |
Enuka Okimba (left) looks on as David testifies at the Lefalin hearing. |
CAN A DRUG THAT LOWERS IMMUNE RESPONSE PUT SOMEONE AT HIGHER RISK TO DEVELOP THE SYMPTOMS OF CHAGAS DISEASE?
What is Chagas disease?
Chagas disease is predominantly found in Latin America. It's caused by the bite of an insect called a "kissing bug". This is the collective name for a group of insects of the family Reduviidae and subfamily Triatominae. These insects often carry a parasite, Trypanosoma cruzi, which is passed on to humans. The parasite can live in the body unnoticed for a few decades before symptoms appear. Symptoms include chronic heart problems and swelling of parts of digestive tract. The major cause of death in people with Chagas disease is congestive heart failure.
Does Chagas occur in the United States or Canada?
Even though Chagas is mostly found in South and Central America, there have been a few cases of Chagas in North America, north of Mexico. The infections that occurred in the US and Canada were all caused by blood transfusions.
Because the parasite goes unnoticed in a person for so long, people often don't realize that they are infected. Immigrants from South America who were carrying the T. cruzi parasite have donated blood after they moved to the US, and the infected blood has ended up in blood banks. Now that they are aware of the problem, the US has started to screen blood for Chagas, and Canada plans to follow soon.
 Image provided courtesy of AXS Studio Inc and Shaftesbury Films. |
|
Artist’s rendition of the Chagas parasite, Trypanosoma cruzi. |
Can you get Chagas disease from food?
In addition to being transmitted through bug bites and infected blood, the Chagas parasite can be passed from a pregnant woman to her developing fetus; as a result, some people have been infected before birth.
But can you be infected by food, as happened to the patients in this episode? Yes, there have been a few cases of food-related Chagas outbreaks. One of the most recent and most well-studied cases is similar to the outbreak portrayed in this episode: In March 2005, several people who bought sugar cane juice at a roadside stand in Santa Catarina, Brazil, developed acute Chagas disease. Acute Chagas causes symptoms rapidly and is more severe than the chronic form, which doesn't kick in until several decades after infection. However, unlike the sugar cane juice in this episode, the Brazilian juice was not exported, and the juice-related infections only occurred in Santa Catarina.
Can Chagas disease be triggered as a result of immuno-suppressants?
The fictional drug, Lefalin, which appears to be related to the onset of Chagas in this episode, is an immune suppressor prescribed to people with an autoimmune disease. In autoimmune diseases a person's immune system attacks their own body. To treat these conditions, the immune system needs to be slowed down, or suppressed. Because the immune system isn't working as well anymore when taking such drugs, patients are more susceptible to all kinds of infections.
There have indeed been several reported cases of AIDS patients who were receiving immune suppressors to manage their condition, but got sick or died from symptoms related to a Chagas parasite that was lingering in their body. If they hadn't received the treatment, their Chagas symptoms probably would not have developed until much later; but, they needed the immune suppressors to treat their autoimmune disease, and unfortunately, the drugs accelerated the emergence of Chagas. The same thing happened to the patients in this episode.
So?
A lowered immune response caused by immuno-suppressants makes a person more susceptible to any infections. If a person on such drugs is carrying the Chagas-causing parasite, T. cruzi, their Chagas symptoms may start earlier than they would if that person was not on the drugs. This does not mean there is a problem with the medication; these drugs are supposed to lower a patient's immune response. Such patients must be as careful as possible to avoid contracting any infections - but there's little they can do about an infection they already have, particularly if they don't know they have it!
However, the cases investigated by NorBAC had all contracted Chagas through sugar cane juice, and this form of the disease is normally more acute. So, at least some of the patients would have gotten sick at the time they drank the juice and therefore might not have taken immuno-suppressants until they were rid of the parasite.
DID YOU KNOW?
David mentions Karl Popper and "finding black swans." Karl Popper was a 20th century philosopher of science. One of the questions he grappled with was when to consider a statement "scientific" or not. Karl Popper is famous for his falsification theory: he said that a statement can be considered scientific only if it could be proven wrong (or falsified) by observations. He used the colour of swans as an example: For centuries, Europeans had only ever encountered swans that were white, and had accepted the statement "all swans are white" as being true. But as soon as they set foot in Australia, they found black swans. They could no longer say "all swans are white" -- it only took one black swan to falsify the statement. According to Popper, this means that the claim that "all swans are white" is scientific, because it's falsifiable by observing a non-white swan. To Popper, the potential of finding a counter-example to a theory was more important than finding many observations that support the theory.
-- Eva Amsen
Want to read and learn more?
Read what the Public Health Agency of Canada has to say about Chagas disease:
http://www.phac-aspc.gc.ca/tmp-pmv/info/am_trypan_e.html
Find out how the US is now screening donated blood for Chagas disease:
http://www.cdc.gov/mmwR/preview/mmwrhtml/mm5607a2.htm
Learn about the infected sugar cane juice found in Brazil:
http://www.nytimes.com/2005/04/12/health/12docs.html
Read more about falsifiability, including Popper's swan example:
http://en.wikipedia.org/wiki/Falsifiability
