The next parasite I want to talk about is the one that causes Chagas disease. This is also a protozoan parasite. It's a type of trypanosome, and this one is actually not seen globally. This affects about six to seven million people approximately, mostly in Mexico, Central, and South America, and it's often referred to as American trypanosomiasis, and that's to differentiate it from African trypanosomiasis, which is caused by a very similar organism. And you may have heard of African sleeping sickness being transmitted by the tsetse fly.
So that's the African trypanosome. Now, trypanosoma cruzi, which is the protozoan that causes Chagas disease, is transmitted by something called a kissing bug or a triadamine bug. And this particular organism bites people usually near their eyes or their mouth.
I think that's why it's called the kissing bug, because it gives them a little kiss on their face. That's a pretty nice way to put it. This parasite can also be transmitted mother to child.
It can be transmitted via blood and organ donations. And if the insect, the triatomine bug, poops near food, it can actually be transmitted from food by ingesting that food and ingesting the parasite. This is primarily a problem south of the United States, but of course with climate change, these insects are moving north.
So the CDC... estimates that there are about 300,000 cases of Chagas disease inside the U.S., even though most of those people were probably infected elsewhere. Like most of these protozoan parasites, Trypanosoma cruzii has a fairly complicated life cycle, and I'm actually not going to go through the whole life cycle, but I want to draw your attention to a few key spots.
The triatomine bug, the first thing it does is it bites you. When it bites you, it usually poops at the same time. The parasites in the poop infect the cells where you were bitten.
They go through a single life cycle stage and then those parasites are released into the bloodstream. The parasite then can get from your blood into muscle tissue and this can include your heart tissue and tissue in the gut. This is where it does most of its long-term damage. Obviously the parasites themselves can then get back into a new triatomine bug when...
you get bitten again and then it will bite a new person and the cycle starts over again. It's really possible to be bitten by a triatomine bug and have no symptoms at all. If you do have symptoms then it's typically fever, maybe a little bit of swelling around where the bite is. This begins in acute phase which lasts just a few weeks or months.
The big problems with Chagas disease occur in a chronic phase. So many people actually remain asymptomatic for life and there are no long-term consequences. But for some, the parasites that are mainly in the heart and the digestive muscle, they actually will damage that muscle over time. And about 20 to 30 percent of people develop severe or life-threatening symptoms.
These typically include heart rhythm abnormalities, having an enlarged heart, in the gut you can have a dilated esophagus or colon. This causes problems eating or passing stool. There are excellent treatments for shockous disease. The key is that a lot of people don't realize they have it and they don't get treatment and these chronic cases can occur and by the time someone realizes that they're in heart failure it's too late. So the goal is to treat people early with drugs during that acute phase when the parasite can be cleared and before there's any permanent damage.
Benzinizol and nifertimox are both great drugs. You can also do a lot to prevent Chagas disease by improving housing, so you want to have less bugs in the house using insecticides, using bed nets, and then of course because this has other routes of transmission, blood donations and organ donations need to be screened, and pregnant women need to be screened to make sure they don't pass the parasite onto their child. Next we're going to spend a few minutes talking in very general terms about infections of the nervous system.