María Inés Guaia, Argentina
Chagas disease is the most important parasitic disease in Latin America,
and the third most important infectious disease in the region, only after AIDS
and tubeculosis. According to WHO figures, an estimated 10 million people are
infected worldwide, and more than 25 million are at risk, most of them in Latin
America.
This disease is caused by the parasite Trypanosoma cruzi, a
flagellate protozoan, which is most often transmitted to men and other animals
by an insect vector commonly named ‘vinchuca’. Vinchuchas are blood-sucking
insects of the family Reduviidae, subfamily Triatominae.
(Vinchuca)
The transmission generally happens at night, when the bugs emerge to
feed. Unfortunately, vinchucha often
take to dining on human blood. They bite
humans, ingest their blood and immediately defecate liquid feces on the wound.
The infection occurs if the Tripanosoma cruzi parasites in the insect feces
enter the organism through mucous membranes or breaks in the skin. This is more likely to happen if the bitten
person, likely asleep and unaware, scratches or rubs the feces into the bite
wound.
Blood transfussions, infected organ transplants and mother-to-child
exchanges during pregnancy are other, less common, avenues for transmission. In rare cases, Chagas has been transmitted
through consumption of uncooked food contaminated with feces from infected bugs,
or even accidental laboratory exposure.
The incubation phase of the disease lasts about a week. Following it,
the disease evolves in three stages:
Acute phase: During the first 20 to 30 days, there may be inflammation in the
place of bite, with local redness and temperature. Trypanosomas can be seen
moving just by examining a drop of infected blood with the microscope.
Intermediate or latent
phase: This is a variable period during which
symptoms are absent. It can last for many years; generally, for the rest of an
infected person’s life. The existence of parasites can be confrimed by
observing antibodies in a blood test.
Cronic phase: The last phase depends on the severity of the case. This phase
ussually starts 10 to 20 years after the infection. In many cases, patients
realise they have the disease in this stage. Symptomes related to the affected
organ/s (most commonly heart, colon or esophagus) arise. The most common
alteration is the dilation of the organ/s involved. Chagasig cardiopathy is the
most common cause of cardiac impairment and sudden death in the endemic zones
of South America. It develops as right cardiac impairment and conduction
dysfunctions.
Chagas is mainly a disease of the poor. The substandard housing
conditions in which millions of people in LatinAmerica live provide plenty of
cracks and holes in which the vinchuca can nest and develop confortably.
Crowding and poor hygienic conditions also facilitate the proliferation of the
bug.
The Chagas disease problem should not only be addressed from a
medical and sanitary point of view, but also as a socioeconomic and
infrastructural issue.