R e v is ta d a S o c ie d a d e B ra sile ir a de M edicin a T rop ic al 2 7(3):16 3-16 9, ju l-s e t, 1994.
TH E HAMSTER
(M ESO CRICETU S A U R AT U S)
AS
EXPERIM ENTAL MODEL IN CHAGAS’ DISEASE:
PARASITOLOGICAL AND HISTOPATHOLOGICAL STUDIES
IN ACUTE AND CHRONIC PHASES OF
TRYPANO SO M A C R U Z I
INFECTION
Luis Eduardo R am irez, E liane Lages-Silva, José M aria Soares Junior and Edm undo Chapadeiro
This re se a rc h ch aracterizes the acute a n d chronic p h a se s o f Chagas ' d ise ase in h am ster through p a ra sito lo g ic a l a n d histopathological studies. The acute p h a s e w as a ch ie ve d with 44 y o u n g ham ste rs injec ted intraperitoneally with 10 0 .0 0 0 blood trypom astigotes o f B en ed ito a n d Y str a in s o fT . cruzi. The ch ronic p h a se was indu ced in 4 6 ha m sters injected intraperitoneally w ith 3 5 .0 0 0 trypom astigotes o fV ic e n tin a , B enedito and Y strains. A n im a ls w ere sa crificed at re g u la r intervals o f 24 ho urs o f acute p h a se a n d fr o m the 3 r<^ to the lCf^1 m onth o f infection o fc h r o n ic ph ase. In the acute p h a se , p a ra sites w ere easily re c o v e re d fro m a ll anim als a n d there w as an inflam m atory reaction characterized by m on onu clear a n d p o ly m orph o u s leukocyte infiltration o f variable d eg ree in the m ajority o f tissues a n d organs, specially in the connective loose a n d fa tty tissu es, sm ooth m uscle m yocardium a n d skeletal m uscle. In the ch ro nic p h a s e the lesions o ccurre d in the sam e tissues and organs, but the inflam m atory re sp o nse w as less se v e re a n d ch ara cterized by m ononuclear infiltration m ainly with fo c a l or z o n a lfib ro sis in the m yocardiun. In 50% o f infected anim als p ara site s w ere fo u n d inm yo ca rdiun a n d re c o v e re d fro m p e ric a rd ic , p e rito n e a l a n d ascitic flu id s in som e anim als. Signs o f h eart fa ilu r e , sud de n dea th a n d en largem en t o f b ow el w ere o b serve d regularly. W e co nclu ded th a t th e h a m ste r is a n u sefu l m o d e l f o r C hagas 'disease studies.
K ey w ords: C hagas ’ disease. E xperim ental model. H am ster.
Many species o f animals have been used as
models to study the infection o f T. cru zi, being the
mouse, rat, guinea pig, rabbit, dog and the monkey the most frequently employed9. Although the
susceptibility o f hamster to T. cru zi is well known,
this animal has been not used yet as an experimental model for Chagas’ disease. Only a few papers describe the infection in the acute phase (AP) and no one in the chronic phase (CP).
Cariola e t a l10 infected hamsters with the
Tulahuen strain o f T. cr u zi and observed nests o f
parasites in all organs, great inflammatory reaction, degenerative phenomena and a high hyperplasia of
D isciplina de Parasitologia, D epartam ento de C iências Biológicas da F acu ld ad e d e M ed icin a do T riân g u lo M in eiro , U beraba, M G .
S u p p o rted b y F M T M -F U N E P U , FA P E M IG and C N P q, A d d r e s s to: D r. Luis E d u ard o R am írez. P raça M anoel T erra , s/ n , 3 8 0 2 5 -0 5 0 U b erab a, M G .
R eceb id o p ara p u b licação em 2 1 /0 3 /9 4 .
the macrophagic system. They also observed high mortality rates o f the infected animals. Osimani and Gurri25 made compared between the infection o f
many different Uruguayan strains o f T. cru zi and
observed a higher susceptibility o f mice (100%) in relation to hamster (65% ). Schoemaker and Hoffman32 infected mice, rats, hamsters and guinea
pigs with trypomastigotes o f Tulahuen strain o f T.
cruzi and observed that mice were more severely infected than the other three species and that fat tissue and the adrenal cortex were not infected.
In view o f the few papers about the infection by T. cruzi in hamster and in order to search for an ew
R a m ir e z L E , L a g e s-S ilv a E , S o a re s J u n io r J M , C ha pa deiro E. The h a m ste r M esocricetus auratus a s e x p e rim e n ta l m o d e l in C h a g a s ' d is e a se : p a ra sito lo g ic a la n d histo p a th olo g ical stu dies in acu te a n d ch ro n ic p h a s e s o/T rypanosom a cruzi infectio n. R e v ista d a S o c ie d a d e B r a sile ira d e M ed ic in a T ro p ic a l 2 7 :1 6 3 -1 6 9, ju l- s e t, 1994.
MATERIAL AND METHODS
In the AP forty-four young non isogenic Syrian hamsters ( M e s o c r i c e t u s a u r a t u s), 34 males and 10 fem ales, were infected intraperitoneally with 100.000 trypomastigotes from Y and Benedito
strains o f T . c r u z i (Benedito strain was isolated
through xenodiagnosis from a patient with the indeterminate form).Fifteen animals, nine males and six females, were used as controls.
The parasitologic study was performed through the direct method7 at intervals o f 24 hours until the 15th day post-infection. Three infected animals and one control were randomly sacrificed after ether anesthesia at the same intervals .
In the CP forty-six hamsters, 22 males and 24 females, in the same conditions as AP group were infected with 35.000 trypomastigotes forms from Y, Benedito and Vicentina strains (Vicentina strain was isolated through xenodiagnosis from a patient with chronic cardiac form) and twelve hamsters, six males and six females, were used as controls.
The parasitologic studies were performed at each 3 0 d ay s th rou gh the m eth od s o f microhematocrit concentration and hemoculture (LIT mediun). At each 30 days, three to four infected animals and one control were randomly sacrificed until the 1 0 ^ month post-infection. Fragments o f the same tissues and organs o f the AP were obtained and also from animals that died spontaneously or from those sacrificed in general bad state.
The tissue specimens obtained at the necropsy in both experiments were fixed in 10% formalin solution and embedded in paraffin; 5-7/un sections were stained by hematoxylin-eosin (H .E) and Gomori trichromic for routine histopathologic a n a ly sis. T h e p ero x id a se - an tip eroxid ase immunohistochemistry test was used for tissular parasitism search.
RESULTS
During the AP all infected animals showed patent parasitemia. Those infected with the Y strain had a pre-patent period o f 5 days and a maximum peak o f parasitemia on 6th, 9th, 13th and 15th days with a maximum number o f4 .5 0 0 trypomastigotes/ 5/xl o f blood. In Benedito strain the pre-patent period was three days and the maximum peak o f
1 6 4
p arasitem ia w as on the 8 ^ day w ith 6 4 trypomastigotes/5/iil o f blood. The parasitemia o f these animals was low and no death was observed during the AP.
In animals chronically infected (after three months) the parasitémie curves were very similar to th o se o b se r v e d w h e n 1 0 0 .0 0 0 b lo o d trypomastigotes were injected. Nevertheless the parasitemia was lower with the Vicentina strain,
with a maximum o f 16.2 trypomatigotes/5f ti o f
blood during the AP. In this experiment, two animals infected with Y strain died, but no death was noticed in animals infected with the other strains. The parasitemia detected at each 30 days through microhematocrit and hemoculture methods was sometimes positive and sometimes negative.
In the AP o f both experiments no important clinical signs were noticed. At necropsy infected animals showed enlargement and congestion o f heart, spleen and liver. Microscopic lesions were common and progressive since the first 24 horns in the majority o f tissues and organs, being more severe in the loose connective and fatty tissues (cellulitis) and the smooth muscle. The heart (Figure 1) presented carditis (peri, myo and endocarditis) early in atria and later in ventricles with mononuclear and polymorphous leucocytes infiltration o f the three layers including the specific conduction tissue. The autonomic atrial ganglia, as well as the nervous twigs (ganglionitis and neuritis), were also infiltrated by the same cells with degenerative changes and nerve cells necrosis.
R a m ir e z L E , L a g e s-S ilv a E , S o a re s J u n io r J M , C h ap ad eiro E. T he h a m ste r M esocricetus auratus a s e x p e rim e n ta l m v d e l in C h a g a s ' d is e a se : p a ra sito lo gical a n d histo p ath o lo gical stu dies in acu te an d ch ro n ic p h a s e s o f T T y p u n o s o m a . cruzi in fection . R e v ista d a S o c ie d a d e B ra sile ir a d e M ed ic in a T ro p ic a l 27:1 6 3-16 9, ju l- s e t, 1994.
In the digestive tract it was also observed acute inflamation with the same inflamatory cells mainly in the muscular layer (myositis) and myoenteric ganglia (ganglionitis) with signs o f ganglion cells degeneration and necrosis (Figure 2).
F igure 2 - L a rg e intestine o f h a m ste r infected in the A P exhibiting se v e re m o no nu cle a r infiltration o f the m uscle lay er (m yositis) a n d m yoenteric p le x u s (ganglionitis). H E 100X.
Genital internal lesions were early and generaly severe in the smooth muscle layer, intheinterstitium o f the testis (orchitis) and the adnexa (epididymitis, vesiculitis, prostatitis and funiculitis), and also in the ovary and uterus (oophoritis and metritis).
The spleen, thymus, lymph nodes and the bone marrow presented, since the beginning, a reactive state o f variable intensity with phagocytosis o f parasites.
Lesions in other organs as skeletal muscle (m yositis), lungs and bronchia were less severe and appeared later. Adrenal glands showed nodules o f mononuclear and polymorphous leucocytes in sinusoids with phagocytized parasites. Nothing was noticed in other organs o f the endocrine system.
In general, the tissue parasitism in the AP was early and more severe in the loose connective and fat tissues, particularly surrounding the internal genitals, peritoneum and smooth muscle fibres o f internal genitals, from the 3rd day after-infection for both strains. In other tissues and organs the parasitism was delayed (seven to nine days after infection). N o correlation between the grade o f inflammatory reaction and tissue parasitism was
noticed anywhere. It should be emphasized that the acute inflammatory response was present in variable degree in the absence o f parasites since the first 24 hours post-infection for both strains.
In the CP, some animals presented a bad general state characterized by apathy, loss o f weight, ulcerative gingivitis, pallescense, dyspnea and g e n e r a liz e d edem a; se v e n a n im a ls d ied spontaneously.
In seven animals it was observed edema in the subcutaneous fat tissue and a clear and transparent abdominal, pleural and pericardial liquid effusion. In some o f these animals it was found trypomastigotes in the pleural, pericardic and ascitic fluid through microhematocrit concentration and hemoculture methods.
The heart o f the majority o f animals was
enlarged and congested with dilatation o f the cavities specially o f the apex o f the left ventricle with mural trombosis (Figure 3). The liver was also enlarged and congested; mild to moderate splenomegaly was noticed. In some animals, the intestinal tract, specially the bowel, presented variable degree o f dilatation o f the lumen (Figure 4). Atrophy o f
F igure 3 - C ontrol h am ste r h e a rt (right) a n d ch ronic chagasic h e a rt (left) with dilatation o f cavities (cardiom egaty).
R a m i r e z L E , L a g e s - S i l v a E , S o a r e s J u n i o r J M , C h a p a d e i r o E . T h e h a m s t e r M esocricetus auratus a s e x p e r i m e n t a l m o d e l i n C h a g a s ’ d i s e a s e : p a r a s i t o l o g i c a l a n d h i s t o p a t h o l v g i c a l s t u d i e s i n a c u t e a n d c h r o n i c p h a s e s ofTrypanosom a
cruzi i n f e c t i o n . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d x ç i n a T r o p i c a l 2 7 : 1 6 3 - 1 6 9 , j u l - s e t , 1 9 9 4 .
internal genitals mainly o f testis, ovary and uterus was frequent.
The microscopic lesions were relatively scanty and found in the heart, digestive tract and adnexa and internal genitals. A ll cardiac layers were
infiltrated only by round mononuclear cells,
nevertheless the myocardic lesions were more severe with focal or zonal endomisial infiltration and fibers destruction sometimes accompanied by variable extension o f fibrosis (Figure 5). The myocardic specific tissue showed the same lesions. In the myocardium were found amastigote nests in 50% o f infected animals. The epicardiun showed also focal or patchy areas o f mononuclear infiltration as w ell as the autonomic cardiac ganglia and nerve twigs associated to degenerative changes and reduction o f nerve cells (Unpublished data).
F ig u r e 5 - H a m s te r h e a r t in th e C P sh o w in g f o c a l m y o c a r d itis e x te n d in g to th e e p ic a rd iu m a n d
g a n g lio n itis (a rro w ). H E 10 0X .
T h e g a s tr o -in te s tin a l tract p resen ted mononuclear cells infiltration o f the muscle layer (m yositis) and o f the nervous myoentericus ganglia (ganglionitis Figure 6). In the liver, besides the congestion, there were intralobular nodules o f mononuclear infiltration, fatty degeneration o f hepatocytes and deposits ô f Congo red stained material similar to amyloid. Chronic pancreatitis with parenchimatous atrophy was also observed.
Internal genitals exhibited chronic mononuclear cells infiltration in the testis (orchitis), epididymus (epididymitis, Figure 7), seminal vesicle (vesiculitis) and prostate (protatitis) in males and ovary (oophoritis) and uterus (metritis) in females with variable atrophy o f these organs. The urinary tract
F ig u re 6 - L a r g e in te s ti n e fr o m , th e s a m e a n im a l e x h ib itin g d is c r e e t m o n o n u c le a r in filtra tio n
in th e m u s c u la r la y e r (m y o sitis) a n d in th e m y o e n t e r i c p l e x u s ( g a n g l i o n i t i s ) w i th
d e s tr u c tio n o f n e r v e c e lls . H E 4 00 X .
F ig u re 7 - E p id y d im u s f r o m o n e a n im a l in th e C P s h o w in g s e v e r e m o n o n u c le a r in filtra tio n o f
th e in te r stic iu m w ith tu b u la r a tr o p h y . H E
lOOx.
showed the same chronic cell infiltration especially in themuscle layer (cystitis, ureteritis and urethritis).
The thymus, lymph nodes and spleen presented discreet chronic reactional state.
In the central nervous system there were the same chronic focal cell infiltration (encephalitis and meningitis). Focal neuritis and spinal ganglionitis with characteristic infiltrate o f mononuclear cells were observed, too.
The skeletal muscles showed focal myositis with mononuclear cell infiltration and necrosis o f fiber cells (Figure 8).
R a m i r e z L E , L a g e s - S i l v a E , S o a r e s J u n i o r J M , C h a p a d e i r o E . T h e h a m s t e r M esocricetus auratus a s e x p e r i m e n t a l m o d e l i n C h a g a s ' d i s e a s e : p a r a s i t o l o g i c a l a n d h i s t o p a t h o l o g i c a l s t u d i e s i n a c u t e a n d c h r o n i c p h a s e s o/T rypanosom a cruzi i n f e c t i o n . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 7 : 1 6 3 - 1 6 9 , j u l - s e t , 1 9 9 4 .
F ig u r e 8 - S k e le ta l m u s c le w ith f o c a l c h r o n ic n ec ro tizin g m y o s itis . H E 4 00 x.
DISCUSSION
The parasitological behaviour o f the T . c r u z i
infection in hamster ( M e s o c r i c e t u s a u r a t u s) during
the AP showed that Y strain is more virulent than Vicentina and Benedito strains. This fact is also observed when Y strain is used in other experimental models1218 2S. Although the inocula utilized in AP and CP were different from each other they maintained their original characteristics curves.
W hile the elevated number o f trypomastigotes o f Y strain in the AP killed the majority o f mice4 8, infected hamsters remained in a good general state and only two deaths ocurred. This is also observed when infections are made with Y strain in other experimental models as rats12 rabbits28 and dogs11 which demonstrate that the hamster has a more efficient control o f the infection than mice.
The parasitemia evaluated in CP through the hemoculture and microhematocrit concentration methods, confirms that hamster does not abort the infection as does rats and other animal models9 and probably the chagasic human39. The parasite isolation from pericardic, pleural and ascitic fluids, in higher number than in blood through microhematocrit and hemoculture methods is a finding not yet related. This fact needs further studies for explanation.
Our data shows that in the AP, macroscopic and microscopic lesions in the heart and in other organs are similar to that found in man20 and in other experimental m odels5 6 12 19 33. It should be emphasized that the internal genitals and urinary tract o f hamsters o f both sexes are early and severely
invaded by the same inflammatory process as described for m ice17 and guinea pig15.
The mortality in the CP occurred occasionally as consequence o f the infection, heart failure or even due to immunodepression. The urinary incontinence was consequence o f cystitis and probably o f lesions in the hypogastric plexus (ganglionitis).
The fluid effusion in the cavities and dyspnea were probably due to the heart failu re, in consequence o f the chronic myocarditis. It is interesting to notice that these manifestations were not discribed in mice and rats, although it has been found in dogs19 and rabbits14 27 36.
The macroscopic and microscopic findings in the majority o f organs in the CP are similar to those fo ip d in other experimental models4 121419 27 36 ancj humans20. The chronic carditis is more discreet, sometimes focal as in the chronic indeterminate form, sometimes zonal as in the symptomatic chronic cardiopathy. The left ventricle apex dilatation suggests the human vorticilar lesio n (apical aneurism)3 23 31.
The gastrointestinal tract enlargement specially o f the bowel, found in some animals, may be a good model to investigate the pathogenesis o f chagasic enteromegalies since this is questioned in other models21 22 24. In this phase the liver lesion were similar to those observed in acute phase but no parasites were seen in the intralobular infiltrates. The pancreas atrophy was probably due to two factors: chronic inflammation and nutritional state o f animals in consequence o f the infection, since controls did not show such lesions.
Skeletal muscles and the nervous system were slightly damaged as in man26 and other experimental models1 2 16 34 35 37.
The urogenital organs were strongly affected in the hamster, as described in other experimental models13 17. Cystitis resulting from lesions o f the
muscular layer associated to the lesions o f
hypogastric plexus were probably the main cause o f bladder enlargement and urinary incontinence. Testes, ovaries and the uterus atrophy are probably consequence o f the severe chronic inflammatory process.
R a m i r e z L E , L a g e s - S i l v a E , S o a r e s J u n i o r J M , C h a p a d e i r o E . T h e h a m s t e r M esocricetus auratus a s e x p e r i m e n t a l m o d e l i n C h a g a s ' d i s e a s e : p a r a s i t o l o g i c a l a n d h i s l o p a t h o l o p c a l s t u d i e s i n a c u t e a n d c h r o n i c p h a s e s o f T rypanosoma cruzi i n f e c t i o n . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 7 : 1 6 3 - 1 6 9 , j u l - s e t , 1 9 9 4 .
C h a g a s’d is e a s e in fe c tio n . A lth o u g h the
e le tr o c a r d io g r a fic stu d y and r a d io lo g ic a l examination o f the digestive tract are going on w e can conclude that the hamster is an useful model for Chagas’disease research.
RESUMO
O p r e s e n te tra b a lh o te m c o m o fin a lid a d e ca r a cte riz a r a s f a s e s a g u d a e c r ô n ic a d a d o e n ç a d e C h a g a s em
h a m s t e r , a t r a v é s d e e s t u d o s p a r a s i t o l ó g i c o s e h isto p a to ló g ic o s . A f a s e a g u d a f o i in d u zid a em 4 4 h a m s te r s j o v e n s , in o c u la d o s in tr a p e rito n e a lm e n te , co m 1 0 0 .0 0 0 tr ip o m a s tig o ta s sa n g u ín e o s d a s c e p a s Y e
B e n e d ito d o T . cruzi. A f a s e c r ô n ic a f o i p r o d u z id a em 4 6 h a m s te r s , in o c u la d o s in tr a p e r ito n e a lm e n te , c o m 3 5 .0 0 0 tr ip o m a s tig o ta s s a n g u ín e o s d a s c e p a s Y, V ic en tin a e B e n e d ito . O s a n im a is f o r a m sa c r ific a d o s a in te rv a lo s
r e g u la r e s d e 2 4 h o r a s n a f a s e a g u d a , d u r a n te 1 5 d ia s e n a f a s e c r ô n ic a , a p a r tir d o 3 ° m ê s a té o 1 0 ° m ê s d a
in fe c ç ã o . N a f a s e a g u d a , o p a r a s ita f o i fa c ilm e n te r e c u p e r a d o d e to d o s o s a n im a is , o s q u a is a p re se n ta r a m r e a ç ã o in fla m a tó ria , d e in te n sid a d e v a r iá v e l, d e c é lu la s
m o n o n u c le a r e s e p o lim o r fo n u c le a r e s , n a m a io r ia d o s te c id o s e ó r g ã o s , p r in c ip a lm e n te n o s te c id o s c o n ju n tiv o f r o u x o e a d ip o s o , m ú s c u lo liso , c a r d ía c o e es q ue lé tic o . N a f a s e c rô n ic a , a s le s õ e s o c o r r e r a m n o s m e s m o s te c id o s e ó r g ã o s , m a s a r e s p o s ta in fla m a tó ria c o m in filtra d o
m o n o n u c le a r f o i m a is g r a v e n o m io c á r d io o n d e a d q u ir iu c a r á te r fib r o s a n te . N o m io c á r d io o s p a r a s ita s fo r a m e n c o n tr a d o s em 5 0 % d o s c a so s. A p a r tir d o líq u id o
p e r ic á r d ic o , p e r ito n e a l e a s c ític o d e s s e s a n im a is fo r a m r e c u p e r a d o s p a r a s ita s a tr a v é s d o m ic r o h e m a tó c r ito e
h e m o c u ltu r a . R e g u la r m e n te , o b se r v a ra m -s e s in a is d e in s u fic iê n c ia c a r d ía c a , c o m m o rte s ú b ita e d e d ila ta ç ã o d o in te s tin o g r o s s o e a tr o fia d o s g e n ita is in te rn os. C o n c lu i-s e q u e o h a m s te r é u m m o d e lo ú til p a r a o e stu d o d a d o e n ç a d e C h aga s.
P a la v r a s - c h a v e s : D o e n ç a d e C h a g a s . M o d e lo e x p e rim e n ta l. H am ste r .
ACKNOWLEDGMENTS
W e thank Luzia Helena Gonçalves dos Santos and Valéria Ramos for technical assistance and Najara Vieira Galvão for help with the manuscript.
REFERENCES
1. A lcân tara F G . D esn erv ação dos gânglios cardíacos
in tram urais e cerv ito ráx ico s na m oléstia d e C h a g as. R evista G oiana d e M edicina 16:259-277,1970.
2. A lencar A. H istogenese do g ran u lo n a chagásico do
Sistem a N ervoso Central do cão. Segundo Congresso Latino-A m ericano d e A natom ia Patológica São Paulo 5 1-52,1958.
3 . A lm eida H O . A lesão v o rtic ilar d a cardiopatia chagásica crônica. T ese de D o u to rad o , U niversidade F ederal d e M inas G erais, Belo H orizonte, M G , 1976. 4. A n d r a d e S G . C a r a c t e r iz a ç ã o d e c e p a s d e
T r y p a n o so m a c r u z i isoladas no R ecôncavo Baiano. R evista d e Patologia T ro p ical 3 :6 5 -1 2 1 ,1 9 7 4 . 5. A n d rad e V , B rodskyn C , A n d ra d e SG. C orrelation
between isoenzym e patterns andbiological behavio ur o f d if f e r e n t s tr a in s o f T r y p a n o s o m a c r u z i .
T ransactions o f the R oyal S ociety o f T ro p ica l M edicine and H y g ien e 77: 79 6 - 799, 1983. 6. A nselm i A , Pifano F C , S u arez JA , D om inguez A,
V a s q u e z A D , A n s e lm i G . E x p e r i m e n t a l
S c h izo tr y p a n u m c r u z i m yocarditis. A m erican H eart Jo u rn al 7 0 :638-656, 1965.
7. B ren er Z . T h erap eu tic activity and criterio n o f c u re on m ice experim entally in fected w ith T r y p a n o s o m a
c r u z i. R evista do Instituto d e M edicina T ro p ica l d e São Paulo 4: 389-396, 1962.
8. B ren er Z . C o m parative studies o f d ifferent strains o f
T r y p a n o s o m a c ruz i. A nnals o f T ro p ica l M edicine and P arasitology 59: 19-26, 1965.
9. B ren e r Z , R am irez L E . M odelos crônicos da doen ça
d e C hagas experim ental. /n :C an çad o JR , C h u sterM (eds) C a rd io p atia c h a g á sic a , F u n d açã o C a rlo s
C hagas, Belo H o rizo n te p. 29 -3 2 , 1985.
10. C a rio la J , P ra d o R , A g o sin M , C h riste n R . Susceptibilidad dei ham ste r ( C r ic e tu s a u r a tu s) & P e ro m y s c u s (P e ro m y sc u s m a n ic u la tu s gam beliX , a la infección experim ental p o r T r y p a n o s o m a c m z i , cepa T u lahuén. B oletin Inform ativo P arasitarias C hilenas V: 44-45, 1950.
11. C astro M A , B ren er Z . E studo p ara sito ló g ico e
anatom o-patológico da fase ag u d a da d o en ç a d e C hagas em cães inoculados co m d u as d iferen tes cepas d e T r y p a n o s o m a c r u zi. R evista da S ociedade B rasileira d e M edicina T ro p ic a l 1 8 :2 2 3 -2 2 9 ,1 9 8 5 . 12. C hapadeiro E , B eraldo PSS, Jesu s P C , O liveira J r
W P , Ju n q u eira J r L F . L esõ es card íac as em ratos W is ta r in f e c ta d o s co m d if e r e n te s c e p a s do
T r y p a n o so m a c r u z i. R evista d a S o cied ad e B rasileira d e M edicina T ropical 21 :9 5 -1 0 3 , 1988.
13. C iconelli A J, E studo quantitativo d os n eu rô n io s do plexo hipogástrico in ferio r em ratos n o rm ais e em
infectados ex perim entalm ente pelo T r y p a n o so m a
c r u zi. T e se d e D ou to rad o , U n iv ersid a d e d e São Paulo, R ibeirão P re to ,S P , 1963.
14. Fig ueiredo F , R ossi M A , R ibeiro dos S antos R. Evolução d a cardiopatia experim entalm ente induzida
em coelhos infectados com T r y p a n o s o m a cruzi-Revista da Sociedade B rasileira de M edicina T ropical
R a m i r e z L E , L a g e s - S i l v a E , S o a r e s J u n i o r J M , C h a p a d e i r o E . T h e h a m s t e r M esocricetus auratus a s e x p e r i m e n t a l m o d e l i n C h a g a s 1 d i s e a s e : p a r a s i t o l o g i c a l a n d h i s t o p a t h o l o g i c a l s t u d i e s i n a c u t e a n d c h r o n i c p h a s e s o/T rypanosom a cruzi i n f e c t i o n . R e v i s t a d a S o c i e d a d e B r a s i l e i r a d e M e d i c i n a T r o p i c a l 2 7 : 1 6 3 - 1 6 9 , j u l - s e t , 1 9 9 4 .
18: 133-141, 1985.
15. F ra n co M F . C a rd ite experim ental do cobaio pela
cep a Y do T r y p a n o s o m a c r u z i. C orrelação entre a
histopatologia e a p rese n ça d e antígenos parasitários id e n tific a d o s p o r im u n o flu o re sc ê n c ia ind ireta. Revista da Sociedade Brasileira de M edicina Tropical 23: 187-189, 1990.
16. Ja rd im E . M oléstia d e C hagas experim ental no rato:
parasitism o do núcleo do 111 p a r cra n ia n o . Revista do Instituto d e M edicina T ro p ica l d e São Paulo 13:405- 410, 1971.
17. L am ano C arv alh o T L , R ibeiro R D , L opes RA. P arasitism o f th e m ale reproductive organs by
T r y p a n o s o m a c r u z i (Bolivia strain). M em órias do Instituto O sw aldo C ruz 84(suppl.II):22, 1989. 18. L an a M . O cão com o m odelo experim ental p a ra o
estudo da doen ça d e C hagas. T ese d e D outorado, U n iv e rsid a d e F e d e ra l d e M inas G erais, Belo H o rizo n te, M G , 1992.
19. L an a M , C h iari E , T a fu ri W L . E xperim ental C h a g a s’d ise ase in dogs, M em órias do Instituto
O sw aldo C ru z 1 7 :59-71,1
m ,
20. L opes E R , C hapadeiro E ,T afu ri W L , Prata AR, D oença d e C hagas. In : L opes E R , C hapadeiro E, R aso E , T afuri W L (eds) Bogliolo Patologia, Rio de Ja n eiro , G u an ab ara, Koogan p. 1047-1065, 1987. 21. M arsd en P D , A lv a re n g a N J, Soares V A , G am a MP,
A ttem pts to p ro d u c e m eg asy n d ro m e in m ice using sto ck s o f T r y p a n o s o m a c r u z i a sso c ia te d w ith m egaoesophagus in m an. Transactions Royal Society
T ro p ical M edicine and H ygiene, L ondon 73: 651, 1979.
22. M arsd en PD , Seah SKK , D ra p er C C , Pettitt L E ,
M iles M A , V o lle r A. E xperim ental T ry p a n o so m a
c r u z i infection in rhesus m onkey. II T h e early ch ro n ic phase. T ran sactio n o f the Royal Society o f
T ro p ic a l M e d icin e an d H y g ien e , L ondon 70: 2 4 7 :2 5 1 , 1976
2 3 . M ig n o n e C . A lguns aspectos da patologia da cardite c h a g á s ic a crônica. T e se d e d o u to ra d o , U niversidade São P aulo, São P aulo-SP, 1958.
24. O k u m u ra M . D o en ça d e C hagas experim ental. In:
R aia A A (ed) M anifestações digestivas da M oléstia d e C h ag as, São Paulo p. 35-59, 1983.
2 5 . O sim ani JJ, G u rri J. Infección experim ental dei h am ster dorado (M e s o c r y c e tu s au ra tu s) co n algunax
cepas u ruguayas d e T r y p a n o s o m a c r u zi. A rchivos d e la S ociedad d e Biologia de M ontevideo XVIII: 7 3-78, 1954.
26. P rata A , Porto G. B iopsia d e m úsculo na doença de
C hagas. R ev ista do Instituto de M edicina T ropical d e São Paulo 8 :1 9 í-1 9 6 , 1966.
2 7 . R am irez L E . O coelho com o m odelo experim ental
no estudo d a d o en ç a d e C hagas crônica. T e se de
D outorado, U n iv ersid ad e F ed eral d e M inas G erais, ' Belo H orizonte-M G , 1984
28. R am irez L E , B ren e r Z . E valuation o f th e rab b it as am odel for C hagas’disease. I. Parasitological studies.
M em órias do Instituto O sw aldo C ru z 82: 531- 536, 1987.
29. R am irez L E , L ages-Silva E , C hapadeiro E . Infecção do ham ster pelo T r y p a n o s o m a c r u z i. R evista da Sociedade B rasileira d e M edicina T ro p ica l 2 4 :1 1 9 - 120, 1991.
30. R a m ire z L E , L a g e s-S ilv a E , S o a re s J r JM ,
C hapadeiro E . Infecção experim en tal do h am ster pelo T r y p a n o so m a cr uzi: fase crô n ica. R evista da S ociedade B rasileira d e M edicina T ro p ical 26: 253- 254, 1993.
31. R aso P, C hapadeiro E , T afu ri W L , L opes E R ,
R o ch a A . A natom ia p ato ló g ic a d a c a rd io p atia
crônica. In: C ançadoJR , C husterM (eds) Cardiopatia
Chagásica. Fundação C arlos C hagas, Belo H orizonte p .41-53, 1985.
32. Schoem aker JP , H offm an J r RV. P ossible stim ulatory
f a e te r (s ) In b r o w n a d ip o s e tis s u e in m ic e .
E xperim ental P arasitology 35: 272-274, 1971,
33. S ousa M A , A len car A A. O n the tissu lar parasitism o f T r y p a n o s o m a c r u z i and strain in Sw iss m ice, Revista do Instituto d e M edicina T ro p ical d e S Io
Paulo 26: 316-321, 1984.
34. Tafuri WL, Brener Z. Lesões do sistema nervoso autônomo do camundongo albino na T r i p a n o s o m í a s e c r u z i experimental na fase aguda. O Hospital 69:
179-191, 1966.
35. Tafuri WL, Lima Pereira FE, Bogliolo L, Raso P. Lesões do sistema nervoso autônomo e do tecido muscular estriado esquelético na fase crônica da
T r i p a n o s o m o s e c r u z i experimental. Estudos ao
microscópio óptico e eletrônico. Revista Goiana de Medicina 26: 61-67, 1979.
36. T eixeira A R L , F igueiredo F , R ezen d e Filho J, M a c e d o V . C h a g a s ’ d i s e a s e : a c l i n i c a i ,
parasitological, imm unological and pathological study in rabbits. T h e A m eric an Jo u rn a l o f T ro p ica l M edicine an d H yg ien e 32: 258 -2 7 2 , 1983.
37. V ichi FL . E studo do parasitism o na m edula espinal
de ratos na fase ag u d a d a m oléstia d e C hagas. R evista do Instituto de M edicina T ro p ica l d e São Paulo, 3: 37 -4 2 , 1961.
38. W ord H ealth O rganization. R ep o rt o f th e Scientific W orking G roup on th e D evelopm ent an d E valuation o f A nim al M odels for C h a g a s’d isease. G eneva,
1984.
39. Z eledón R , D ias JC P , S alazar-B rilla A , R ezende
JM , V argas L G , U rb in a A. D oes a spontaneous cu re for C h a g a s’ disease exist? R evista d a Sociedade
