Chagas disease

Chagas disease, also known as American trypanosomiasis, is a serious parasitic infection. It is caused by a tiny organism called Trypanosoma cruzi.

This disease is classified as a neglected tropical disease. This means it primarily affects people living in poverty. As of 2019, it is estimated that 6.5 million people live with the infection. Most cases occur in Mexico, Central America, and South America.

However, large-scale migrations have carried the disease to the United States and Europe. It is not just a human problem, as it affects over 150 types of animals.

The infection cycle begins with insects called triatomine bugs.

These insects are often called "kissing bugs" because they prefer to feed on moist surfaces near the eyes or mouth. When a bug bites a person to take a blood meal, it also defecates. The Trypanosoma cruzi parasites are found in the bug's feces. If a person scratches the bite, the parasites enter the body through the wound. Once inside, the parasites enter the bloodstream as motile forms called trypomastigotes. They then invade host cells and transform into a different form called an amastigote. Inside the cell, the amastigotes replicate many times. Eventually, they turn back into trypomastigotes and burst the cell to spread throughout the body.

Chagas disease progresses through two distinct stages. The first is the acute stage, which appears one to two weeks after infection. This stage is often symptom-free, but when symptoms do appear, they are usually mild. They can include fever, headache, and swollen lymph nodes. A specific sign called Romaña's sign involves swelling of the eyelid.

In rare cases, the acute stage can be life-threatening by causing brain inflammation. After four to eight weeks, the acute phase typically resolves. However, the person remains infected and enters the chronic stage.

The chronic stage can last for many years and is often silent. Many people have what is called indeterminate chronic Chagas disease, where they show no symptoms. However, over decades, the parasite can cause serious organ damage. This is known as determinate chronic Chagas disease. About 14% to 45% of people with chronic infections develop heart disease.

The heart may experience arrhythmias, which are irregular heartbeats. In many cases, the heart ventricles become enlarged, a condition called dilated cardiomyopathy. This enlargement makes it much harder for the heart to pump blood effectively.

Digestive complications are another major part of the chronic stage. Up to 21% of people experience damage to their digestive system. The most common issues are an enlarged esophagus or an enlarged colon. People with an enlarged esophagus may suffer from pain while swallowing or acid reflux. Those with an enlarged colon might face severe constipation or intestinal blockages. Additionally, up to 10% of people may experience nerve damage. This can lead to numbness or changes in how they move.

In 1909, a Brazilian physician named Carlos Chagas first described this disease.

The disease is named in his honor. Doctors diagnose early infections by finding the parasite in the blood using a microscope. They can also use a technique called polymerase chain reaction to detect the parasite's DNA. For chronic cases, doctors look for antibodies in the blood. These are proteins the immune system makes to fight the infection. While we have medicines like benznidazole and nifurtimox, they work best shortly after infection.

These drugs can have side effects like skin disorders or digestive irritation.

Prevention is the most effective way to manage the spread of Chagas. One method is to eliminate kissing bugs using insecticides. People can also use bed-nets to avoid bites while sleeping.

It is also vital to screen blood used for transfusions and organs. This is because the disease can spread through blood, organ transplants, or from a mother to her baby. While scientists have studied vaccines in animals, a human vaccine has not yet been developed. Researchers continue to work on new drugs to help those living with this complex disease.