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Memórias do Instituto Oswaldo Cruz
Fundação Oswaldo Cruz, Fiocruz
ISSN: 1678-8060 EISSN: 1678-8060
Vol. 90, Num. 6, 1995, pp. 687-688
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Memorias do Instituto Oswaldo Cruz
Vol. 90(6), Nov./Dec. 1995
RESEARCH NOTE: Search for Trypanosoma cruzi in the Anal Glands
of Wild Didelphis albiventris from Santiago del Estero,
Argentina
Osvaldo Conti, Nicolas J Schweigmann, Silvia Pietrokovsky,
Victoria Bottazzi, Cristina Wisnivesky-Colli
Laboratorio de Ecologia de Reservorios y Vectores de
Parasitos, Departamento de Ciencias Biologicas, Facultad de
Ciencias Exactas y Naturales, Pabellon II, 4o Piso, Ciudad
Universitaria, 1428 Nunez, Buenos Aires, Argentina
Code Number: OC95139
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Key words: anal glands - opossums - Didelphis albiventris -
Trypanosma cruzi
The genus Didelphis is one of the most important
sylvatic reservoirs of Trypanosoma cruzi (Barretto 1979
Epidemiologia, p. 89-151. In Z Brener , ZA Andrade Trypanosoma
cruzi e Doenca de Chagas. Guanabara Koogan, Rio de Janeiro).
In a parasitological follow-up performed during 1984-1991 in
the Departamento Moreno, province of Santiago del Estero,
Argentina, D. albiventris showed annual prevalences of
T. cruzi infection between 29 to 50% (NJ Schweigmann 1994
Doctoral Thesis). Since the low T. cruzi infection rate
(about 1%, unpublished results) of the wild triatomines
captured in the same area might not account for the high
prevalence recorded for opossums, we decided to study other
alternative routes of transmission.
MP Deane et al. (1984 Mem Inst Oswaldo Cruz 79: 513-515)
described two coexisting cycles of T. cruzi in experimentally
infected D. marsupialis: one involving bloodstream
trypomastigotes and the other epimastigotes and metacyclic
trypomastigotes in the lumen of the anal glands. Opossums of
other genus such as Lutreolina crassicaudata also
showed parasitized glands as a result of experimental
infections (M Steindel, CJ Carvalho Pinto 1988 Mem Inst
Oswaldo Cruz 83: 397).
Though unfrequent, positive anal glands of naturally infected
opossums were subsequently confirmed for Brazilian populations
of D. marsupialis and D. albiventris (M Steindel
et al. 1987 Mem Inst Oswaldo Cruz 82: 66, RD Naiff et al. 1987
Resumos X Congr Soc Bras Paras, Salvador, Bahia p.87, M
Steindel et al. 1988 Mem Inst Oswaldo Cruz 83: 135-137, AJ
Fernandes et al. 1987 Mem Inst Oswaldo Cruz 82: 65). These
findings prompted us to examine the anal glands of D.
albiventris from Santiago del Estero, as well as to
consider their eventual role in the direct transmission of
T. cruzi.
From the beginning of 1990, wild specimens of D.
albiventris were confined in individual cages and kept in
an animal house free of triatomines in the field. Three
successive xenodiagnoses were performed on each animal at
intervals of approximately 45 days, and they were considered
as infected when at least one of these tests was positive. A
total of 56 D. albiventris - 15 males and 41 females -
were used. According to CH Tyndale-Biscoe and RB Mackenzie
(1977 J Mammal 57: 249-265), animals corresponded to ages four
(n = 18), five (n = 33) and six (n = 5). Of these, 38 were
positive to T.cruzi.
The anal glands of positive and negative live opossums were
examined in August and September 1990 and in February, June
and October 1991. Five infected and four non-infected animals
were re-analyzed in June and July 1991.
The perianal zone was thoroughly disinfected and the anal
glands contents, obtained by direct puncture, were cultured in
blood-agar biphasic medium (OE Souza 1985 Rev Soc Bras Med
Trop 18: 23-27) as well as in Brain-Heart-Tryptose liquid
medium (S Pietrokovsky 1991 J Parasitol 77: 643-645) and kept
at 28 C. The microscopic examination was performed at days
10th and 30th post-culture in our laboratory in Buenos
Aires.
Trypanosomes were never observed in the culture media
suggesting that in naturally infected opossums anal glands are
seldom or never parasitized, in agreement with other authors
(Naiff loc. cit., Steindel et al. loc.cit, Fernandes et al.
1989, Mem Inst Oswaldo Cruz 84: 87-93).
We assume that our results can be made extensive to the whole
D. albiventris population of the study area since the sampling
involved an adequate number of animals of different seasonal
periods, ages and sexes (Schweigmann loc. cit.).
We considered that even if there were some opossums having
infected anal glands, the parasite transmission would be
hindered by their solitary habits. Therefore, this mechanism
of direct transmission should be extremely efficient as to
account for the high opossum infection rates found in Santiago
del Estero. Further research regarding other transmission
routes is needed to explain this fact.
This research work was performed with financial support from
Secretaria de Ciencia y Tecnica, Universidad de Buenos Aires,
Argentina.
Received 21 February 1995
Accepted 14 July 1995
Copyright 1995 Fundacao Oswaldo Cruz, FIOCRUZ
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