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Chagas' disease in pre-Columbian South America.

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Chagas’ Disease in Pre-Columbian South America
Department o f Cellular Biology and Genetics, University o f Chile, Santiago
7 (F: R.j, Institute of Anthropology and Archaeology, University of Tarapacd,
Arica (M.J.A., VS., B.A.), and Department of Archaeology, Northern
University, Antofagasta (LN.j, Chile
The quest for the origin and dispersion of Chagas’ disease, the
second most important vector-borne disease in Latin America, has epidemiological, immunological, and genetical implications.
Conjectures based on accounts of chroniclers, reviews of the archaeological
literature and the present distribution of triatomine bugs, the vectors of the
disease, held that the origin of the adaptation of Triatoma infestans (a species
of the subfamily Triatominae) to human dwellings occurred in prehistoric
The autopsy of 35 mummies exhumed in the Chilean desert, dated between
470 B.C. and 600 A.D., revealed the presence of clinical manifestations of
Chagas’ disease and put earlier speculations on a factual basis.
Chagas’ disease is, after malaria, the most
prevalent vector-borne Latin American malady (Schofield et al., 1982). It was discovered
by the Brazilian Carlos Chagas in 1909
(Leon, 1962) and is caused by the protozoan
parasite Trypanosoma cruzi, which is commonly transmitted in the faeces of reduviid
bugs of the subfamily Triatominae, but may
also be conveyed by blood transfusion, congenitally, orally, or by organ transplant
(Schofield et al., 1982). The most frequently
encountered Triatominae in meridional
South America belong to the species Triatoma infestans and are found in rural dwellings proliferating in the cracks of roofs and
Anecdotal information provided by chroniclers and naturalists suggests that the adaptation of T infestans to human habitats
occurred before the sixteenth century. Among
others, Fray Reginald0 de Lizarraga and
Padre Bernabe Cobo, Spanish priests, noted
the presence of blood-sucking bugs in Argentina, Bolivia, Chile, and Paraguay (Leon,
1962); and Charles Darwin mentioned having been attacked by the “benchuca” (vinchuca) in Argentina (Darwin, 1839). This
term is derived from Quechua and still used
to designate triatomine bugs in Andean
countries (Carpintero and Viana, 1980). Recently, Carpintero and Viana (19801, on the
basis of the aforementioned accounts as well
0 1985 ALAN R. LISS, INC.
as on incomplete archaeological literature reviews and the present distribution of Tinfestans, speculated that the adjustment oftriatomine bugs to human dwellings took
place in certain early agroceramic foci which
emerged in the central sierras of Argentina
around 500 A.D., as well as in southern Peru
and eastern Bolivia. The ancient and widespread practice of Andean aborigines to raise
guinea pigs (Cauiaporcellus)for consumption
might have favored the adaptation of Triatominae to human habitats. These small rodents, as well as larger mammals such a s the
American Camelidae, probably hosted l? infestans before becoming domesticated.
The object of this report is to describe the
results of the autopsies of Chilean mummies
which revealed the presence of clinical manifestations of Chagas’ disease and to put,
through the presented evidence, earlier speculations about the origin and dispersion of
this disease on a factual basis.
The arid northern part of Chile which extends from the Peruvian border to the Copiapo river, consists of a t least three ecogeographic areas, namely, the Andean highlands, the fertile transverse valleys and ravReceived March 26, 1985; revised June 28. 1985; accepted July
15, 1985.
ines, and the desert between the valleys.
Vegetation in the valleys is correlated with
humidity and includes such diverse plants as
cattail (Scirpus californieus) and carob tree
As part of a multidisciplinary research effort concerned with the early emergence of
sedentarism in the Chilean desert, 35 mummies of four archaeological sites dated respectively with I4C at 470 B.C., 383 A.D.,
290-360 A.D., and 600 A.D. (Nuiiez, 1982)
were exhumed in Quebrada de Tarapaca (latitude 19" 57' S; longitude 69" 33' W; elevation 1,150 m). This is a small transverse
valley that was peopled around 2850 B.P. by
incipient agriculturalists who first built rectangular shelters and later dwellings from
mud blocks, stone, and straw, providing ideal
conditions for the adaptation of triatomine
The mummified bodies were autopsied in
search of mega-syndromes, which are the result of the denervation of the intraneural
nervous plexus of hollow organs such as the
colon, the heart or the esophagus caused by
I: cruzi (Koeberle, 1956). Megacolon was diagnosed by relative size of colon and weight
of coprolites, and cardiomegaly and megaesophagus by relative heart size and esophagus diameter. Diagnoses were performed by
one of us (M.J.A.). Male and female age estimates were obtained according to methods
described by Bass (1971).
to have megacolon. A 20-25-year-old male
had megacolon and megaesophagus and, finally, a 2%-half-year-oldboy exhibited megacolon and cardiomegaly.
Among affected females were four mummies with megacolon aged, respectively, 12,
35-40, 40, and 50 years. Considering the
above figures we tentatively estimated the
prevalence of megacolon in pre-Columbian
Chilean populations to be 41%. Similar estimates for cardiomegaly and megaesophagus
are respectively, 9% and 4.5%.
It is unlikely that the megacolon cases discovered are attributable to aganglionic
megacolon, since the rectum of megacolon
mummies was distended with faeces, as opposed to the empty rectum found in Hirschsprung's disease (La Mont and Isselbacker,
1980). Moreover, congenital megacolon as
well as chronic idiopathic megacolon and
other forms of colon distention which are secondary to neurologic disorders, myxedema,
amyloidosis, or scleroderma are very infrequent. It is interesting to note that in a recent survey conducted in Chile, consisting of
the second largest series of patients of South
America, 90% of subjects with megacolon and
100% of individuals with megacolon and
megaesophagus turned out to be serologically Chagas' disease positive (Atias, 1980).
In Chile, megacolon is approximately four
times a s frequent as megaesophagus. In enRESULTS
demic areas, roughly 34% of the population
Table 1 reports the presence of megacolon, was found to be serologically positive. Some
cardiomegaly, and megaesophagus in mum- 24% of positive individuals, roughly 8% of
the population, develop cardiopathies (Arrimies of Quebrada de Tarapaca.
Of 22 mummified bodies which were pre- bada et al, 1981).
It has been suggested to us (P. Horne, perserved in sufficiently good conditions to assure accurate diagnosis, nine mummies sonal communication) that in unembalmed
exhibited mega-syndromes. One 40-45-year- bodies following death, especially in a warm
old male presented megacolon and cardio- climate, fermentation with gas production
megaly. Three 45-year-old males were shown may cause expansion of intestinal walls,
TABLE I . Megacolon, cardiomegaly, and megaesophagus in Pre-Columbiari mummies
from northern Chile
Exhumed bodies
Preserved bodies
Megacolon present
Cardiomegaly present
Megaesophagus present
Archaeological site
which followed by rapid dehydration, could
in turn produce pseudomegacolon. The fact
that the colons of the mummies were packed
with coprolites makes this explanation unlikely. Also, the expansion due to gas from
ingestion of beans, i.e., Phaseolus lunatus, is
not supported by analysis of coprolites, which
contained carob tree sheaths, i.e., Prosopis
It has been indicated, furthermore, that
high altitude can eventually cause megacolon (Frisancho, 1974). Consequently, some
mummies with megacolon could have been
migrant highlanders. This conjecture would,
however, imply that an unusually high proportion of the prehistoric inhabitants of Tarapaca valley were recent migrants and that
megacolon was exceptionally frequent in the
highlands. It is worth mentioning in this context, that only one megacolon case was found
in Azapa valley, some 150 km north, among
roughly 500 mummies autopsied. The prehistoric populations of both valleys were, however, exposed to the same highland penetration since around 1000 B.C. (Nufiez, 1983).
Cardiomegaly has been interpreted by us
elsewhere as an indicator of highland birth
(Fontana et al., 1983). However, both cardiomegalic males presented histopathological evidence of fibrotic changes in the myocardial tissue which cannot be attributed to
high altitude. Finally, our finding of a case
of megaesophagus, added to the previously
discussed evidence, strongly suggests that
Chagas’ disease was present in northern
Chile before 500 B.C.
Although our estimates of the prevalence
of megacolon, megaesophagus, and cardiomegaly in pre-Columbian populations may
be biased as a result of the excavation procedures, we note that our figures are similar to
those presently encountered in endemic areas
of Chile.
The transition from a hunting-gathering to
a transitory and subsequently permanent sedentary stage was probably accomplished by
Paleoindian hunters in the Pampa de Junin,
central highlands, some 6,000 years ago
(Wheeler et al., 1976). Permanent dwellings
of stone or mud block (adobe)walls and straw
roofs were built as early as 3000 B.C. in the
central highland and on both the eastern and
western slopes of the southern Andes (Nuiiez, 1983).
Archaeological evidence indicates that the
Quebrada de Tarapaca was initially peopled
by small bands of migrants from the southern highlands, specifically from the shores of
Lake Poopo, as judged by the presence of
ceramic fragments and other cultural artefacts belonging to the Wankarani, a culture
that established itself around 1200 B.C. (NUiiez, 1982).
It is hypothetically possible that before becoming sedentary, Andean Paleoindians acquired Chagas’ disease by ingesting raw
infected meat of Camelidae, Cervidae, or
small rodents, which have probably hosted
T infestans since before the Pleistocene
(Neghme, 1982) and which were found associated with Paleoindian archaeological sites
(Dauelsberg, 1983). Furthermore, given the
opportunistic nature of Triatominae, it may
also be speculated that triatomine-mediated
transmission started with human occupation
of caves and rock shelters. We suggest, however, that the increase of prevalence of the
disease to endemic levels, occurred most
probably after the adaptation of T infestans
to permanent human dwellings in the central and southern highlands before 500 B.C.
This work was supported by grants 825991
UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, B-518-845F, D.I.B., University
of Chile, and 01068 Fondo Nacional de Ciencias, Conicyt, Santiago. We are indebted to
Prof. T. Pizzi for the histopathological analysis of myocardial tissue. Comments of M.
Diaz, L. Eaton, G. Hoecker, and C.Y. Valenzuela are gratefully acknowledged.
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