DOI: 10.1515/ap-2015-0009© W. Stefański Institute of Parasitology, PASActa Parasitologica, 2015, 60(1), 65–74; ISSN 1230-2821

Biological and molecular characterization of a Trypanosoma cruzi isolate obtained from

Panstrongylus megistus captured in Sao Paulo State, Brazil

Luciamáre P.A. Martins1, Roberto E.P. Castanho1, Altino L.S. Therezo2, Aline R. Ribeiro7, Luciana Lima4, Marta M.G. Teixeira4, Márcia A. Sperança5,

Vera L.C. Rodrigues6 and João A. da Rosa3

1Disciplina de Parasitologia da Faculdade de Medicina de Marília, Brasil; 2Disciplina de Anatomia Patológica da Faculdade de Medicina,de Marília, Brasil; 3Disciplina de Parasitologia da Faculdade de Ciências Farmacêuticas da Unesp de Araraquara, Brasil; 4Instituto de Ciências

Biomédicas da Universidade de São Paulo, Brasil; 5Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Brasil; 6Superintendência de Controle de Endemias de Mogi-Guaçu, Brasil; 7Departamento de Biologia Animal do Instituto de Biologia,

Universidade Estadual de Campinas, Brasil

AbstractAn isolate of Trypanosoma cruzi obtained from P. megistus captured in the peridomicile area of a home in Santo Antonio do

Jardim city in the State of São Paulo, denominated T. cruzi Mogi, was characterized biologically and molecularly. The RFLP

analysis of the D7 divergent domain in the 24Sα rDNA and of the mini–exon positioned the T. cruzi isolate within the TcI

group. Phylogenetic analysis performed with the trypanosomatid barcode confirmed that the isolate belongs to the TcI group,

with high homology to the 3014 c1 T.cruzi strain. The biological characterization of the isolate in rats showed a prepatent

period of about 8 days, low parasitemia and tropism for cardiac, skeletal and colonic muscles. In Swiss mice the T. cruzi Mogi

isolate showed a prepatent period of about 22 days, intermittent parasitemia in some animals, and tropism for cardiac and

colonic muscles. Despite the inherent difficulty of identifying correlations amongst the molecular and biological characteris-

tics of different T. cruzi groups, the tropism for colonic muscle demonstrated by T. cruzi Mogi represented a peculiarity of this

isolate within the TcI group.

KeywordsTrypanosoma cruzi, Chagas’ disease, characterization, lineage, DNA, strains

Introduction

There are currently 148 known species of triatomine bugs

(Ayala 2009; Rosa et al. 2012; Gonçalves et al. 2013), 62 of

which can be found in Brazil, and 38 of which are exclusive

to Brazil (Gurgel-Gonçalves 2012; Rosa et al. 2012). How-

ever, only Panstrongylus megistus, Triatoma sordida, T. in-festans, T. brasiliensis, and T. psedomaculata demonstrate

epidemiological significance (Coura and Dias 2009), by virtue

of their anthropophilic characteristics and domiciliation abil-

ities (Coura 2007). In Brazil, T. infestans was restricted to

human dwellings and was the main vector of Chagas disease

until 2006 (Almeida et al. 2009) when, after ostensive control

programs, the transmission of Chagas disease by this

triatomine was interrupted, as confirmed by the WHO (Dias

2006; Silva et al. 2011). However, there is still 1.8 to 2.4

million individuals in Brazil in the chronic phase of Chagas

disease (Almeida et al. 2009) and eight million people in 21

countries in Latin America are infected with Trypanosomacruzi (Schmunis 2007).

After T. infestans control, the secondary native Brazilian

triatomine species, T. sordida and P. megistus, became the

main targets of triatomine vigilance (Wanderley 1991).

P. megistus has a wide distribution in Brazil, being the most

frequently collected species in regions covered by Atlantic

forest and by the gallery forests of the Brazilian Cerrado and

Caatinga biomes (Gurgel-Gonçalves et al. 2012). Due to eco-

logical characteristics, P. megistus is usually found in hollow

trees, palm canopies, and the shelters of rodents and marsupi-

als (Miles et al. 1982; Patterson et al. 2009), which are

*Corresponding author: luciamarepam@gmail.com

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Luciamáre P.A. Martins et al.66

sylvatic hosts of T. cruzi, (Gurgel-Gonçalves et al. 2012). The

epidemiological importance of P. megistus lies in its inva-

siveness and adaptability to domestic and peridomestic envi-

ronments (Rodrigues et al. 2003; Patterson et al. 2009;

Gurgel-Gonçalves et al. 2012). This invasiveness is motivated

by the need for blood feeding due to reduced food sources

(Coura and Borges-Pereira 2012) which is especially likely

to occur in deforested areas and in regions presenting paltry

social conditions (Litvoc et al. 1990).

In the State of São Paulo, Brazil, where Chagas disease

constituted a considerable public health problem until the

1970s (Silva 1986), after T. infestans control, in 1985, T. sor-dida represented 77.4% of the triatomines captured around the

domiciles of different cities in São Paulo State, while

P. megistus represented 15.2%. The T. cruzi infection rate was

0.8% and 7.9%, respectively (Wanderley 1991). Afterwards,

in the period from 1990 to 2007, 19.271 specimens of

P. megistus were captured, 10.962 being adults and 8.309

nymphs. Of these specimens, 58.3% were collected outside and

41.7% were collected inside the domicile. T. cruzi positivity

was 5.2% and 7.2%, respectively (Wanderley et al. 2009). Pre-

cipitin tests showed that 26.2% of these captured triatomines

reacted against human blood (Wanderley et al. 2009). These

results strongly indicate the risk of domiciliation of P. megis-tus infected with T. cruzi, which could pose new Chagas dis-

ease threats to the human population (Rodrigues et al. 2003).

Clinical presentation of Chagas’ disease is highly variable

expressing as negligible, acute, indeterminate and chronic (Teix-

eira et al. 2006). Pathogenesis, response to chemotherapy, geo-

graphic variation, clinical presentation and morbidity of Chagas

disease have been linked to biological, biochemical and genetic

characteristics of T.cruzi strains (Devera et al. 2003) which re-

cently were divided in six discrete typing units (DTUs):

TcI-TcVI (Zingales et al. 2012). The TcI is more related to the

sylvatic cycle and has been associated with cardiomyopathic

manifestations (Ramirez et al. 2010). TcII is mainly transmitted

by T. infestans being associated to Chagas disease in the South-

ern Cone of America. TcV and TcVI correspond to hybrid groups

which contain genetic characteristics from TcIII and TcII/TcIV

(Westenberger et al. 2005). Also, T. cruzi strains can be classified

biologically in biodemes I, II, III according to pathogenecity and

virulence in animals models (Andrade 1974).

Thus, in order to determine the profile of the T. cruzi strains

that are currently circulating in the sylvan environments of São

Paulo State, Brazil – after the eradication of T. infestans – an

isolate of T. cruzi obtained from P. megistus, captured in the

peridomicile area of a home in the city of Santo Antonio do

Jardim was characterized biologically and molecularly.

Materials and Methods

T. cruzi isolation

Two fourth instar nymphs of P. megistus, were captured out-

side the domicile of a rural residence in the Germanada district

of Santo Antonio do Jardim city, localized at 22°06´57˝ South

latitude and 46°40´48˝ West longitude, within the mesoregion

of Campinas, bordering the State of Minas Gerais. The feces

of these two insects were diluted with 0,85% saline and ob-

served in optical microscope at 400 times magnification. After

the finding of Trypanosomatidae shape in feces of these two

collected insects, a portion of feces was inoculated into liver

infusion tryptose (LIT) medium and another portion inocu-

lated into Wistar rats and Swiss mice.

Biological characterization

Parasitemia

Five male Wistar rats (12 days old) and 5 male Swiss mice (20

days old) were infected intraperitoneally with 0.1 ml of blood

containing 1.500 trypomastigotes from another previously in-

fected rat. Parasitemia was investigated twice a week for 60

days from 5 μL of blood collected from the tail of each rat and

mouse according to the technique described by Brener (1962).

Table I. Isolates of T. cruzi included in the phylogenetic analysis: TcI: Jose c2, Honduras, 3014 c1; TcII: SLU31 c2, Esmeraldo, Famema, Y; TcIII: MT 3869, MT 3663, M 6241 c6, SO3 c5

Trypanosoma cruzi Accession number Gene

Tc3014 c1 AY785565.1 18S

Honduras c1 AY785581.1 18S

Jose c2 AY785574.1 18S

Famema c2 AY785584.1 18S

Y AF301912.1 18S

Esmeraldo c3 AY785564.1 18S

SLU31 c2 AY785586.1 18S

MT3869 AF303660.1 18S

MT3663 AF288660.1 18S

M6241 c6 AY785578.1 18S

SO3 c5 AY785580.1 18S

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Biological and molecular characterization of a Trypanosoma cruzi strain 67

Histopathology

Fifteen Wistar rats (12 days old) and 15 Swiss mice (20 days

old) were infected with 0.1 ml of blood containing 1,500 try-

pomastigote, obtained from a previously infected rat. Heart,

liver, colon and skeletal thigh muscle were collected from

three animals on the 10th, 20th and 30th days post parasite in-

oculation for the acute phase of infection; and on the 150th and

180th days post parasite inoculation for the chronic phase of in-

fection. The collected organs were embedded in paraffin and

5 μm sections were stained with hematoxylin – eosin. We used

a semiquantitative scale from zero (–) to three crosses (+ + +)

to grade the inflammatory process and the amount of amastig-

ote nests as follows: “(–)” – absence of inflammation and

amastigote nests; “(+)” – mild inflammation, few amastigote

nests; “(+ +)“ – moderate inflammation and a moderate num-

Fig. 1. Parasitemic curve obtained by averaging the logarithmic number of trypomastigotes/5μl of blood in Wistar rats and Swiss mice infected with 1.500 trypomastigotes of the Trypanosoma cruzi Mogi strain

Table II. Semiquantitative histopathological analysis of inflammation and amastigote nests performed on 15 Wistar rats infected with T.cruziMogi during acute and chronic phases of infection

Heart Skeletal muscle Liver Colon

IP AN IP AN IP AN IP NA

10thDay

R1 – – + – – – – –

R2 – – – – – – – –

R3 + – + – – – + –

20th Day

R4 +++ ++ ++ +++ – – + –

R5 +++ +++ + +++ – – + +++

R6 +++ ++ + – – – + +++

30thDay

R7 ++ – + – – – ++ –

R8 ++ – + – – – – –

R9 ++ – ++ + – – – –

150th Day

R10 ++ – – – – – – –

R11 + – – – – – + –

R12 + + – – – – – –

180th Day

R13 – – – – – – – –

R14 + – – – – – + –

R15 ++ – – – – – + –

IP – Inflammatory process; AN – amastigote nests

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Luciamáre P.A. Martins et al.68

ber of amastigote nests, and “(+ + +)” – intense inflammation

and many amastigote nests.

Molecular characterization

Genotyping

Genomic DNA was obtained from T. cruzi Mogi parasites culti-

vated in 5mL of LIT, concentrated by centrifugation at 3000 g for

10’. The pellet of parasites was resuspended in 50 μl of

digestion buffer (2M NaCl 2M Tris- HCl pH 8.0, 0.5 M EDTA,

pH 8.0, 10% SDS and 10mg/ml of proteinase K) and incubated

for 16 hours at 65°C. The DNA extraction was conducted using

a silica column purchased from GeHealthcare following the

manufacturer’s instructions and stored at –20°C. T. cruzi Mogi

genotyping was performed by analyzing the α rDNA D7 domain

(Souto and Zingales 1993) and the gene encoding the non- tran-

scribed spacer of the mini-exons (Fernandes et al. 2001). The

D7 divergent domain of the 24Sα rDNA of T. cruzi was ampli-

fied with 0.4 mM of the oligonucleotides 5’AAG D71 GTG GT

CGA CAG TGT GG 3’ and D72 5’ GAA TTC TCA GCC AAC

AGT TGG 3’, 2.5 U Taq DNA polymerase (Promega GoTaq)

0.2 mM dNTP, 2.0 mM MgCl2, and 50 – 100ng of T. cruzi Mogi

genomic DNA. The reaction conditions were 1 cycle at 94°C for

5 minutes, 30 cycles (94°C for 30 seconds, 55°C for 30 seconds

and 72°C for 30 seconds) and 1 cycle at 72°C for 7 minutes. The

PCR fragment corresponding to the non-transcribed spacer of

the mini-exon gene was obtained by using 1μM of oligonu-

cleotides 5’ GCG GTG ACA CTT TCT CTG ATC G 3’ (spe-

cific for group TCI DTU I) TC2 : 5’ TTG CTC GCA CAC GCT

GCT GCA T 3’ (specific for group II DTU ), TC3 5’ GCC ACC

ACA CCT CGW MAT AAA AAT G 3’ (specific for group Z3),

TR : 5’ CCT ATT GTG CCC ATC ATC TTC G 3’ (specific for

Trypanosoma rangeli ) and ME 5’ TAC CAA TAT AGT ACA

GAA ACT G 3’ (common to all groups), 0.2 mM dNTP, 2.0 mM

MgCl2, 2.5 U of Taq DNA polymerase ( Promega GoTaq ) and

50–100 ng of genomic DNA. The reaction conditions were 1

cycle at 94°C for 5 min, 40 cycles (94°C for 30 seconds, 55°C

for 30 seconds and 72°C for 30 seconds) and 1 cycle at 72°C for

7 minutes. The strains of T. cruzi: SI 1, Y, Bolivia and QM 1 for

groups TcI, TcII (DTU I and IIb ) were used as positive controls

of PCR reactions and autoclaved distilled water was used as a

negative control. To determine the size of the PCR fragments

obtained, products of the PCR reactions were fractionated using

Fig. 2. Histological sections of Wistar rats organs obtained in the acute and chronic phases of T.cruzi Mogi infection. A. Amastigote nests in muscular layer of colon. B. Skeletal muscle presenting necrosis of muscle fiber and surrounded by inflammatory infiltration.C. Amastigotes inside muscle fiber. D. Diffuse inflammatory process in the muscular layer of the colon

A

C D

B

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Biological and molecular characterization of a Trypanosoma cruzi strain 69

2% agarose gel electrophoresis in 1X TBE (0.1 M Tris- base,

0.09 M boric acid and 0.001 M EDTA, pH 8.0), stained with

ethidium bromide (0.5g/mL) and photographed under UV light.

Phylogenetic analysis

Sequence of the PCR product corresponding to V7- V8 region

of the gene encoding the rRNA small subunit (SSU rRNA) of

the T.cruzi Mogi isolate was obtained [Genbank:KF788250],

in accordance with Lima et al. 2012. The V7V8 SSU rRNA

sequence of T. cruzi Mogi was subjected to comparison with the

sequences available in the GenBank database using the

BLASTN program. A phylogenetic tree was constructed from

the alignment of sequences of the V7 – V8 SSU rRNA of

different T. cruzi strains representative of taxonomic groups of

parasites, as shown in Table I. Alignment was performed by us-

ing the Clustal W program, available in BioEdit (Hall, 1999) and

phylogenetic analyses were conducted using distance method-

ology employing the Neighbor – Joining algorithm and param-

eter p distance calculated by MEGA 3.1 (Kumar et al. 2004).

Results

Triatomine monitoring and notifications made in the State of

São Paulo facilitated the isolation of a wild strain of T. cruzi, demoninated T. cruzi Mogi, from two fourth instar nymphs of

P. megistus captured in the rural district of Santa Germanada in

the municipality of Santo Antônio do Jardim. This strain showed

strong growth in LIT medium and was able to parasitize Wistar

rats, but had difficulty infecting and maintaining in Swiss mice.

Biological behavior of T.cruzi Mogi isolate in Wistar rats

and Swiss mice

Parasitemia

The study of parasitemia in rats revealed a short prepatent pe-

riod, as all animals showed the presence of parasites upon the

first reading at day eight post inoculation, and reached peak

parasitemia 20 days post-infection. Afterwards, parasitemia

declined, indicating the end of the acute phase and the begin-

ning of an early chronic phase of infection. No animals died

during the acute phase of the infection.

In Swiss mice parasitemia of T. cruzi Mogi showed a long

prepatent period with the observation of trypomastigotes on

day 22 post inoculation, evolving with low parasitemia or in-

termittent parasitemia in some animals, and peak parasitemia

around day 43 post inoculation. Only one animal died during

the acute phase of infection (Fig. 1).

Histopathology

Wistar rats

The results of the histopathological study in rats are shown in

Table II and Fig. 2. On the 10th day post-infection only mild

inflammatory infiltrate was observed in the heart, skeletal

muscle and colon, and no amastigote nests were found.

On the 20th day there was an increase in the intensity of

the inflammatory process and the appearance of amastigote

nests in the heart of the three animals examined. In the skele-

tal muscle, the inflammation ranged from mild to moderate,

Table III. Semiquantitative histopathological analysis of inflammation and amastigote nests performed on 15 Swiss mice infected withT.cruzi Mogi during acute and chronic phases of infection

Heart Skeletal muscle Liver Colon

IP AN IP AN IP AN IP AN

10thDay

C1 – – – – – – – –

C2 – – – – – – – –

C3 – – – – – – – –

20th Day

C4 – – – – – – + –

C5 + – – – – – – +

C6 – – – – – – – –

30thDay

C7 – – – – – – – –

C8 – ++ – – – – + +

C9 – – – – – – ++ +

150th Day

C10 – – – – – – – –

C11 ++ – + – – – – –

C12 + – + – – – – –

180th Day

C13 – – – – – – – –

C14 + – + – – – ++ –

C15 – – – – – – – –

IP – Inflammatory process; AN – amastigote nests

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Luciamáre P.A. Martins et al.70

Fig. 3. Histological sections of Swiss mice organs obtained in the acute and chronic phases of T.cruzi Mogi infection. A. Amastigote nestsin cardiac muscle. B. Amastigote nests in colon. C. Moderate chronic inflammatory process in cardiac muscle. D. Moderate chronic inflam-matory process in the muscular wall of the colon

Fig. 4. Agarose gel electrophoresis of PCR products corresponding to ME: a hyper-variable region of the mini-exon gene non-transcribedspacer that is able to characterize T. cruzi I (200 bp), II (250 bp), and Z3 (150 bp); and to the D7 domain of the 24Sα rDNA with primers D71 and D72 that are able to characterize T.cruzi I (110 bp), TcIIb (125 bp), TcIIa (117 bp), and TcIIc (110 bp). T. cruzi isolates: QB1 (TcIIc),TcY (TcIIb), Tc Bolívia (TcI); stock of T. cruzi isolated from Panstrongylus megistus: TcMogi

A

C D

B

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Biological and molecular characterization of a Trypanosoma cruzi strain 71

but with frequent amastigote nests in two animals. In the colon

of two animals, the presence of mild to moderate inflamma-

tory process in the muscle layer with frequent amastigote nests

was observed. This period coincided with the peak of para-

sitemia. Analysis on the 30th day post inoculation showed in-

flammatory process in heart and skeletal muscle in all three

categories, ranging from mild to moderate, and was found in

all animals. Amastigote nests were observed only in the skele-

tal muscle of one animal. At this point in time, colon inflam-

mation was observed in only one animal.

The histopathological analysis in the chronic phase of

infection (150 and 180 days) showed a mild to moderate

inflammatory process in the heart and discrete process in

the colon. At this disease stage, rare amastigote nests were

observed in the heart of one animal.

Swiss mice

Histopathological results obtained from different organs of Swiss

mice infected with T.cruzi Mogi are shown in Table III. During

the acute phase of the disease T. cruzi Mogi presented tropism for

cardiac muscle and discrete colon inflammation was observed.

Rare amastigote nests were verified in heart and colon.

In the chronic phase of infection there were no amastigote

nests observed and only a mild to moderate inflammation was

observed in cardiac, skeletal and colonic muscle.

Molecular characterization of the T. cruzi Mogi isolate

PCR genotyping of the T. cruzi Mogi isolate showed a 110-bp

DNA fragment corresponding to the D7 domain of the 24S_

rDNA amplified with primers D71 and D72 (Souto and Zin-

gales 1993) and a DNA fragment of 200 bp corresponding to

a fragment of the non-transcribed spacer of the mini-exon

gene (Fernandes et al. 2001; Mendonça et al. 2002). These re-

sults indicated that the T. cruzi Mogi isolate belongs to lineage

TCI (Fig. 4). Comparison of V7–V8 rRNA sequences from

the T. cruzi Mogi isolate revealed higher similarity with the

homologous sequence from the reference strains of T. cruziTCI 3014c1 and the genetic relatedness inferred in the phylo-

genetic tree segregated T. cruzi Mogi in the branch corre-

sponding to T. cruzi lineage TCI (Fig. 5). Thus, molecular and

phylogenetic analysis of T. cruzi Mogi corroborate that it

belongs to lineage TCI.

Discussion

Currently, P. megistus is considered the main autochthonous

vector of Chagas disease in the central, eastern and south-

eastern regions of Brazil (Patterson et al. 2009), and is also

the most prevalent species of triatomine in Campinas (Silva

et al. 2006), including the city of Santo Antonio do Jardim

from where we isolated the T. cruzi Mogi strain characterized

in this study. Rodrigues et al. (2009) showed that during the

period from 2000 to 2007 of 3.322 triatomine specimens cap-

tured in the Santo Antonio do Jardim region, 2.977 were of

P. megistus. The nymph of P. megistus harboring the T. cruziMogi isolate was captured in Santa Germanada, a neighbor-

hood within Santo Antonio do Jardim.

Physiological variations inherent to different species of tri-

atomines (Azambuja et al. 2005) and its ecological behavior

Fig. 5. Philogenetic tree based on the rRNA V7-V8-bp sequence

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Luciamáre P.A. Martins et al.72

are important in the selection and geographic distribution of

T. cruzi strains (Araújo et al. 2009), making vector-parasite re-

lationship studies extremely important for the epidemiological

understanding of Chagas disease. P. megistus, a sylvatic tri-

atomine should harbors the TcI sylvatic T. cruzi strains. How-

ever, if the P. megistus changes its ecological habits during the

domiciliation process, it could participate in the transmission

cycle of TcII strains as T. infestans. In order to investigate

these hypothesis, the biological and molecular characteriza-

tion of the T. cruzi Mogi strain were performed.

Molecular characterization by size polymorphism of PCR

fragments corresponding to genes encoding the 24Sα rDNA

D7 divergent domain (Fig. 4) (Souto and Zingales 1993) and

the gene encoding the non- transcribed spacer of the mini-

exons (Fig. 4) (Fernandes et al. 2001) showed that the

T. cruzi Mogi strain belongs to the group TcI, the same group

as the strains isolated by Rodrigues et al (2003) and Monteiro

et al. (2012). These results indicate that TcI are derived from

wild reservoirs and, according to Zingales (2011), belong to

a monophyletic group. Genotyping results were confirmed

by the comparative analysis of the trypanosomatid barcode

sequence with the GenBank database and also by its use in

phylogenetic study (Fig. 5).

Biological characterization of the T. cruzi Mogi strain

showed a short pre-patent period, moderate parasitemia and

virulence in Wistar rats, presenting tropism for cardiac mus-

cle, skeletal and colon in the acute phase of infection (Fig. 1),

and according to Andrade’s criteria (1974), this strain can be in-

cluded in biodeme III. In Swiss mice the T. cruzi Mogi strain

presented a long pre-patent period indicating difficulty in es-

tablishing infection. When infection was achieved, low para-

sitemia, or intermittent parasitemia in some mice, and tropism

for cardiac muscle and colon were observed. These differences

in the biological behavior of T. cruzi Mogi strain in rats and

mice are indicative of the fact that genetic variability of the

host can act as a selective medium, yielding clones of different

parasite variants in the host environment (Martins et al. 2003).

Miles et al. (1982) also reported that strains of T. cruzi iso-

lated from wild foci of Rio de Janeiro showed low virulence

in mice, with infection being difficult to maintain in these an-

imals. Also, Lisboa et al. (2007) found that T. cruzi strains iso-

lated from triatomine vectors of the coastal Atlantic forest,

belonging to genotype TcI, showed sub or intermittent patent

parasitemia in Swiss mice. TcI strains isolated from Rhodniusrobustus and R. pictipes in the Brazilian state of Amazonas

also presented a low pathogenicity in mice. Other biological

behavior in Swiss mice included a discrete inflammatory

process in cardiac and skeletal muscle, and rare amastigote

nests (Monteiro et al. 2012). Thus, low pathogenicity of

T. cruzi TcI strains in Swiss mice seems to be common.

According to Guhl and Ramirez (2011), T. cruzi TcI strains

demonstrated histotropism for cardiac muscle being respon-

sible for the severe cardiomyopathy seen in Chagas disease in

the Southern Cone of South America. Histopathological stud-

ies of the T. cruzi Mogi strain performed in rats showed tro-

pism for cardiac and skeletal muscle (Table II), predominantly

on day 20 post infection. This period coincided with the par-

asitemic peak, corroborating the aforementioned research of

Guhl and Ramirez (2011).

In addition to the skeletal and cardiac muscle tropism seen

in the T. cruzi Mogi strain, the finding of amastigote nests in

the colons of rats and mice is a peculiarity of this strain which

could result in changes in the digestive system, such as mega-

colon, more commonly found in TcII strains (Virreira et al.2006). Although research performed by Zingales et al. (2011)

indicate that TcI strains do not favor digestive alterations, the

inflammatory process and amastigote nests produced in the

colon of rodents by the T. cruzi Mogi TcI strain seem to chal-

lenge this conclusion. Indeed, these findings reveal a greater

diversity in the biological behavior of these strains, up to and

including the possibility to induce the digestive form of Cha-

gas disease (Sanchez-Guillen et al. 2006; Reis et al. 2012).

Control of T. infestans has been effective in diminishing

the transmission of Chagas disease in Brazil, however the con-

tinued presence of naturally infected triatomines in endemic

areas ensures that T. cruzi are not eradicated (Dias 2009).

Thus, characterization research of T. cruzi strains recently iso-

lated from triatomines with high potentiality to invade do-

mestic and peridomestic environments, such as P. megistus,

is of great interest in understanding the clinical and epidemi-

ological manifestations of Chagas disease.

Several studies on the correlation of the biological,

molecular and geographical characteristic of T. cruzi strains

increase our understanding of parasite diversity. In this study,

the tropism of a TcI T. cruzi strain for the colons of rodents

is determined to be a unique characteristic, demonstrating the

complexity of the parasite life cycle and its ability to adapt to

different hosts.

Acknowledgments. Foundation for Research Support of State of São Paulo (Fapesp). Grant number 2009/15824-3.

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