Chagas in the Chaco

Posted on August 22, 2010

My first trip to Paraguay was in July of 2009, when I volunteered with CEDIC (Centro para el Desarrollo de la Investigacion Cientifica), a non-profit research lab in Asuncion.  My main purpose while I was there (aside from improving my Spanish and checking out my future field site) was to add a sociocultural component to their ongoing study of the vectors of Chagas disease in indigenous communities in the Chaco.  (A vector is a carrier that transmits a disease from one organism to another.)

Chagas is an endemic disease in poor, rural areas of Mexico, Central America and South America.  It’s caused by Trypanosoma cruzi, a protozoan parasite that is transmitted by blood-sucking triatomine insects.  Triatomine insects are called “kissing bugs” because they prefer to bite on the face of their victims.  The insects live in the dead wood used to build homes in these parts of the world and come out at night to feed on people while they sleep.  After taking a blood-meal they release their feces containing the parasites near the bite wound.  The parasites can then easily be introduced into the body when the person scratches their bite wound or rubs their eyes or mouth.

Kissing Bug

Immediately after infection people experience the ‘acute phase’ of Chagas disease.  This phase usually goes unnoticed because symptoms are mild or not unique to Chagas disease (i.e. fever, fatigue, body aches, headache, rash – many other medical conditions share these symptoms).  The only distinguishable symptom of acute Chagas is Romaña’s sign, a swelling of the eyelids which occurs when the bite from the kissing bug is near the eye.   After a few weeks or months, symptoms from the acute phase subside and the infection enters the chronic phase.

During the chronic phase few or no parasites are detectable in the infected person’s blood, and they may remain asymptomatic for the rest of their life.  But about 30% of infected persons develop serious medical complications.  The parasite attacks the smooth muscle in the heart and digestive system, leading to heart rhythm abnormalities that can cause sudden death or difficulties eating or passing stool.

There is no vaccine for Chagas disease, but there are two drugs available for treatment (Nifurtimox and Benznidazole).  These drugs can produce very unpleasant side effects and the longer someone has been infected with Chagas the less effective they are.  Since the acute phase of Chagas disease is difficult to distinguish from other medical problems it is difficult to catch the disease early.  Most of the indigenous peoples we interviewed did not know what Chagas disease was, or if they did know what it was, they did not know that it was spread by kissing bugs – so they would not know when to seek treatment.

Most prevention programs focus on the vector for Chagas disease, and try to eliminate the kissing bugs from human habitations with two strategies:  (1) spraying homes with insecticide and (2) improving housing conditions (plastering walls, using metal instead of thatched roofs).  Unfortunately, but not unexpectedly, the kissing bugs have developed some resistance to the insecticides and re-infest the houses that have been sprayed.  CEDIC is trying to learn more about the ecological factors involved in the re-infestation process (such as, what factors make it more likely that a house will be re-infested? and where are the re-infesting kissing bugs coming from?).

The second home improvement strategy sounds nice enough, but is difficult to implement in practice.  These communities are extremely poor.  It’s not that people in these communities don’t want to improve their homes: they simply don’t have the resources to make these improvements.  The Chaco is a difficult place to eke out a living, and economic development in these communities is challenging.

To read more about Chagas disease you can go here or here.

I’ve posted some pictures from my trip last year in the Flickr gallery (see the column on the right).

Posted in: Chagas disease