Chagas Disease in Merida

By Jessica Malachowski
April 9, 2012

For anyone that’s ever traveled internationally, my arrival experience will sound very familiar. My layover in Texas was long and I quickly realized the layout of Bush International was awful. When I finally flew into the airport in Merida, it was almost 11 a.m., and unlike the airport security in Grenada, the officers hardly glanced at my passport before yawning and waving me through.

Merida, in the Mexican Yucatan, is very hot during the summer. When I arrived, I was told that I had just missed the hottest month where by midnight, it was still over 100 degrees and 100 percent humidity. By late May, it was only 95 late at night; I quickly decided that the extra 1000 pesos a month for AC was completely worth it.

All of my living arrangement had been arranged by Dr. Dumonteil, who I’d met during orientation almost a year before. When he’d stood up with the other professors and told us that he did drug research in Chagas disease, my brain said yes!

For public health students the practicum, in some form, will be a familiar term. For every student some hands-on, practical experience in the field of public health is required. Students work in local state health offices, do research for professors in their department, or run off to other countries (sometimes through the Peace Corps) for a time determined by their department. For tropical medicine, I needed 200 hours, and decided a lab in Mexico researching novel drug treatments for a parasite sounded particularly awesome.

Chagas disease is a chronic disease that is caused by the parasite Trypanosoma cruzi, transmitted through the feces of Reduviid bugs. Also known as cone-nosed bugs, assassin bugs, and kissing bugs, these little blood suckers are hemimetabolous and require a blood meal for each stage of their lifecycle. Reduviid bugs can live out in the wild, or in your home, loving to hide out in the cracks in the walls and thatched roofing. Found from the tip of South America all the way up to the southern United States, these bugs are very nasty eaters. During a blood meal, they decide their tummies are too full, and to make room for the meal they’re taking, they poop.

In terms of parasite transmission using an insects poop is not particularly effective, and thus higher base levels of insect infection is needed to maintain transmission. This means that more insects have to be infected, which increases your risk, if you’re bitten, of that annoying insect being infected. The parasite itself, T. cruzi, is very effective at getting in through mucous membranes and piercing your skin; they simply crawl down a hair follicle and, shlooop, they’re in.

The majority of people that get infected have few or no symptoms during the acute phase of infection, though children are at greatest risk of serious health problems. After about 6 months, after the end of the acute phase of infection, 70-90 percent of people never show chronic response to infection. The chronic form of the disease, Chagas, only occurs in 10-30 percent of people. Chronic disease doesn’t manifest until 20 or 30 years after initial infection and this poses many complications in terms of public health and education about the disease. Although people living in endemic areas are familiar with the bug and many know of Chagas, people don’t readily associate the bugs with the disease. Sometimes the only indication that a person has Chagas is that they drop dead due to ventricular aneurism! Infection often occurs at a very young age and the parasite can easily cross the placenta, meaning that a female line can carry the parasite without ever being exposed to the bug (just think of what that means about women immigrating to the US from an endemic area as the parasite can also be transmitted by blood transmission!). I got to go out into the field to a small rural town outside of Merida a couple of times to help collect bugs for a colony Dr. Dumonteil is trying to establish. Homes are very open with thatched roofing and animal housing is close by, all things Reduviids love!

The reason so few people develop chronic disease is not known, but some researchers believe it has to do with genetic immune propensity for a Th1 dominant T cell response. My work was a pilot study to investigate the response of administering IL 12 from transgenic tomatoes to force a Th1 immune response in a mouse model. For anyone that suddenly went, wait … a drug treatment in a plant!? LOOK IT UP! There have been a lot of advances in development of vaccine administration and drug treatment using food … especially bananas and tomatoes. This method could basically, hopefully, eliminate the cold chain needed for vaccines.

Every morning I would ride my bike to the lab — to get an idea of that experience, imagine the drivers in Grenada but in a major city with narrower sidewalks and more traffic and BIG buses – translate lab manual stuff from Spanish into English, or English into Spanish, and take care of my mice and other lab duties. My day-to-day work wasn’t really very glamorous, though I loved it, which is why I’m not going to tell you anything more about it (and why I droned on so long about the bugs and parasites! They’re far more fascinating). I, by the way, do not really speak Spanish, which made working with my non-English speaking lap partner very … interesting. But one thing about immersing yourself in a foreign country is that if you don’t speak the language, you learn.

I loved my time in Merida! The city is beautiful, the culture is rich, and the people are wonderful. The food, Yucatecan cuisine, is so so good. Although I was very busy with my practicum work, I did get to see some of the tourist attractions!

Chichen Itza is beautiful and I would highly recommend seeing the site and others of the Yucatan. I also went to Holbox (hall bosh) and went swimming with whale sharks! In my afternoons, if it wasn’t too hot, I would explore the city center and the vibrant, crazy markets that absolutely buzzed with people. Though a warning to all, meat markets in warehouses with no refrigeration smell really, really, really awful. On Friday nights and Saturdays, you could find cultural shows and little craft markets surrounded by food vendors (at which I never got ill), and anyone traveling through Merida should take the time to admire the colonial architecture and visit the anthropology museum. By the end of my seven weeks in Merida, I was very sad to leave.

Jessica Malachowski is a student at St. George’s University. She received her MSPH in Tropical Medicine from Tulane University School of Public Heath and Tropical Medicine.

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