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versión impresa ISSN 0716-0720
Parasitol. día v.25 n.3-4 Santiago jul. 2001
Prevalence of Tetratrichomonas didelphidis from the
Opossum Didelphis albiventris in the Botanical Garden,
Porto Alegre, Rio Grande do Sul, Brazil
* Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Avenida Ipiranga, 6681 Porto Alegre 90619-900 RS, Brasil.
** Associação Pró-Carnívoros, Porto Alegre, RS, Brasil.
*** Instituto de Geriatria e Gerontologia, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Avenida Ipiranga, 6681 Porto Alegre 90619-900 RS, Brasil.
**** Faculdade de Farmácia, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Avenida Ipiranga, 6681 Porto Alegre 90619-900 RS, Brasil. Corresponding author: E-mail: firstname.lastname@example.org
Tetratrichomonas didelphidis (Hegner and Ratcliffe 1927) Andersen and Reilly 1965 is a flagellate protozoan from the intestine, cecum and colon of Didelphis marsupialis Linnaeus, 1758. The prevalence of T. didelphidis in opossums D. albiventris was studied in the Botanical Garden, Porto Alegre City in the southernmost Brazilian State, Rio Grande do Sul, Brazil. T. didelphidis was found in seven of eight cultures of swabbed rectums, representing a prevalence of 87.5% in D. albiventris. In the present investigation it was observed that the T. didelphidis found in the intestine content of D. albiventris had the same morphological characteristics as those previously described by other authors in the D. marsupialis, being probably the same protozoan species in both host species.
Key words: Tetratrichomonas didelphidis, Didelphis albiventris, prevalence, opossum.
Tetratrichomonas didelphidis is a parasitic protozoan from the intestine, cecum and colon of the opossum Didelphis marsupialis. The protozoan is a flagellate belonging to the family Trichomonadidae, subfamily Trichomona-dinae1. The taxonomy of trichomonads has had a complex history. This species was first described with the name Trichomonas didelphidis.2 Subsequently, was described again the species on the correct genus Tetratri-chomonas.3
Up to the present there is only one paper on the occurrence and anatomy of trichomonads from opossum D. marsupialis. There is no paper about the prevalence in D. albiventris and this is the first report on the occurrence of T. didelphidis from the cecum and colon in opossums (D. albiventris). Nothing is known about the transmission, epidemiology, pathoge-nicity, biochemistry and imunologic features, neither about the culture requirement of the parasites.
The aim of this study was to determine the prevalence of T. didelphidis in opossums D. albiventris in the Botanical Garden, Porto Alegre City in the southernmost Brazilian State, Rio Grande do Sul, Brazil.
MATERIAL AND METHODS
In the present study was used the Diamond's modified trypticase-yeast extractstarch (TYS)4 medium, pH 7.5, without maltose and with starch solution (5 mg/ml).5 The opossums were captured and, immediately after examination set free with a little incision on the ear for demarcation to avoid repetition of animals. The rectum of the opossums were swabbed and the swabbings and fecal material was inoculated into TYS medium, pH 7.5, for incubation. Samples were cultured in vitro at a temperature of 28º C (± 0.5) in TYS medium supplemented with 10% (v/v) heat inactivated bovine serum, penicilin (1000 U/ml) and streptomycin sulfate (1 mg/ml). Material for the stained smears was obtained from a 72 h old culture in TYS medium and stained by the Giemsa method6. The morphologic study was made by light microscopy with an Olympus AX 70 microscope connected to a video camera and to a computer with the program Image-Pro Plus 4.1.
The prevalence of T. didelphidis was determined in the summer, January and February. T. didelphidis was found in seven of eight cultures of rectums swabbed, representing a prevalence of 87.5% in opossums D. albiventris. The number of opossums investigated in the park was 8 (n = 8), based on the binomial probabilities table 7 and, on the occurrence data of other authors.3 Direct microscopic examination of wet smears from the intestinal content and feces revealed vast numbers of actively motile flagellates protozoa.
The organisms were classified as trichomonads because of their elongate ellipsoid shape, the presence of an undulating membrane associated with four free anterior flagella which could be accurately counted only when the trichomonads had slowed down or stopped moving. The body is very plastic but not particularly ameboid. The trophozoites had a long posterior free flagellum and a parabasal body disc-shaped with well defined constant central granule. Most of these morphological features could be recognized in air-dried smears of intestine content, fixed in methanol and stained with Giemsa. Examination of the cultures after incubation at 28º C from 48 to 72 h revealed a heavy growth of flagellates. The cultures were routinely maintained in TYS medium at 28ºC and transferred three times per week (at 48 or 72 h).
Even so, in this investigation it was observed that trophozoites of T. didelphidis has the same morphological characteristics as previously described by other authors.
The trichomonads belong to the subkingdom Protozoa, phylum Sarcomastigophora, subphilum Mastigophora, class Zoomastigo-phorea, superorder Parabasalidea and order Trichomonadida.8 They are classified in the family Trichomonadidae and subfamilies Trichomonadinae, Tritrichomonadinae and Pentatrichomonadinae. In the subfamily Tri-chomonadinae there is a typical pelta. This subfamily contains four genera. In the genus Trichomonas the posterior flagellum is not free, whereas it is in the other three; Trichomonas has four anterior flagella. The other three genera can be differentiated by the number of their anterior flagella and by the shape of their parabasal bodies. In the genus Trichomitus there are three anterior flagella and the parabasal body is usually V-shaped (occasionally rod-shaped). In the genus Tetratrichomonas there are four anterior flagella in mature individuals and the parabasal body is usually disc-shaped. In the genus Pentatrichomonas there are five anterior flagella, of which four are grouped together at the base and one is independent, and the parabasal body appears to be composed of small granule(s).1
The genus Tetratrichomonas is different from Trichomonas not only with respect to minor morphological characteristics but also in the structure of the well-developed undulating membrane, the outer margin of which continues into a free posterior flagellum. It is the last attribute which facilitates most the distinction between Trichomitus and Tetratrichomonas on one side and Trichomonas on the other. Although it is nearly impossible to be certain which of the genera, Tetratrichomonas or Trichomonas, or if both of them, came directly from a Trichomitus-type flagellate, it seems that in most features, morphological as well as physiological (for example, the primitive site in the hosts), Tetratrichomonas is closer to the main line of evolution1. The phylogenetic analysis of T. didelphidis is in the present, aim of study of our group.
In the present investigation it was observed that T. didelphidis is a frequent inhabitant found in the intestine content of opossums D. albiventris. The isolates had the same morphological characteristics as those previo-usly described in D. marsupialis3, being the same protozoan species in both different host species.
Acknowledgments: We are grateful to Iveli Rosset (BPA-PUCRS) and Rossana Mattia.
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