Chagas disease is an anthropozoonosis caused by the protozoan
parasite Trypanosoma cruzi that represents a major
public health problem throughout Latin America. The Hamer lab
studies Chagas disease in the United States, but with help from the
CVM travel grant I was able to explore the ecology of T.
cruzi in an endemic environment, in Campo Grande Brazil.
T. cruzi demonstrates extreme biological
plasticity. It can infect a wide range of mammalian hosts and is
genetically diverse being characterized by seven genotypes. In the
US, we find two strain types, while in Brazil they have all
seven. The goal of this project was to explore the genetic
diversity of T. cruzi in wildlife along the
urban-sylvatic interface. While ample research has been devoted to
transmission and control of T. cruzi in a domestic or
peridomestic environment, many questions remain regarding T.
cruzi ecology and transmission along the sylvatic-urban
environments. To better understand the sylvatic cycle we sampled
wildlife in peridomestic environments and propagated T.
cruzi from host blood in pure culture to ascertain the
genetic strain type. T. cruzi plasticity within
the sylvatic transmission cycle threatens progress towards Chagas
disease elimination as spillover from wildlife reservoirs and oral
transmission can limit the effectiveness of conventional vector
control methods. Our research aimed to provide an ecological
basis for disease transmission, which is a necessary prerequisite
for developing effective intervention strategies.
For the first three weeks of my project I worked in the city
Campo Grande, which is a biologically diverse area with a wide
diversity of wildlife species. Here we set up traps in city
parks and along urban-sylvatic interfaces. Small mammals were
captured by setting up linear transacts with defined capture points
using baited Sherman and
Tomahawk live traps. Trapped animals were either euthanized for
blood sample collection by cardiac puncture for parasitological and
serological analyses, or the animal was anesthetized and skin and
blood samples were taken. We mostly caught opossums and some small
rodents, opossums are a known reservoir for T. cruzi
in Brazil. We did also sample a marmoset to see if it
was T. cruzi positive (it was not).
Additionally, we set up mist nets in the evening to capture bats.
Two bats of each species were euthanized for blood and tissue
collection, all other bats were tagged and released.
For my remaining time in Brazil, I analyzed the samples at
FioCruz in Rio de Janeiro. FioCruz is a well-known public health
organization that is at the forefront of Chagas disease
research. I worked under the guidance of Dr. Jansen, the head
of the trypanosomatids biology laboratory. Here I
examined and tested the samples collected in the field. To
test for the T. cruzi parasite, fresh blood samples
were examined to visualize flagellates and hemoculture was
performed. Hemoculture will be
performed by inoculating blood into tubes with media and visually
examined weekly for three (for seronegative animals) to six weeks
(for seropositive animals). Samples were also tested by
Indirect Immunofluorescent Antibody Test (IFAT) and ELISA to detect
anti-T. cruzi IgG antibodies. While not
directly a part of my research there, I got to see their kissing
bug colony, which as established over 50 years ago from kissing
bugs throughout South and North America. We established a
kissing bug colony at TAMU two years ago, but it was wonderful to
see the diversity of species that they had at FioCruz and to see
how they housed and cared for their bugs-all information that will
be informative for our TAMU colony.
Working in the Chagas disease system in an endemic environment
was both enlightening and rewarding (finding a T.cruzi
positive animal is more common in Brazil than in our Texas
environment). It was also wonderful to work on part of a project
that is a part of such a large and established research
facility. Chagas research is relatively new in the US, where
our first human case was documented in 1950s and the first canine
case the 1970s, whereas Carolos Chagas, a Brazilian physician at
FioCruz, first discovered Chagas disease in 1909. Therefor it
was educational and inspirational to be in this environment.