Triatomines Involved in Domestic and Wild Trypanosoma cruzi Transmission in Concepción, Corrientes, Argentina

Vol. 97(1): 43-46, January 2002

María Esther Bar/+, Miryam Pieri Damborsky, Elena Beatriz Oscherov, Alicia María Francisca Milano, Gilberto Avalos, Cristina Wisnivesky-Colli*

Cátedra de Artrópodos, Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Av. Libertad 5470 (3400) Corrientes, Argentina *Unidad de Ecología de Reservorios y Vectores de Parásitos, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina

An entomological and serological survey was performed in three localities of the Department of Concepción, Province of Corrientes, Argentina in 1998 and 1999, to identify triatomines species involved in domestic and wild transmission of Chagas disease. Triatomines were collected by man/hour capture in 32 houses randomly selected and 44 nearby outdoor ecotopes. Trypanosoma cruzi infection in triatomines was assessed by direct microscopic observation (400x) of feces and polymerase chain reaction. Serological techniques used for people were Indirect Hemagglutination Test and Indirect Fluorescent Test. Triatomines were collected in 28.1% of the houses and 31.8% of the wild biotopes. Triatoma infestans (Klug 1834) was exclusively found indoors and T. cruzi infected 60% of them. Triatoma sordida (Stål 1859) was mainly found in extradomestic ecotopes where trypanosome infection rate reached 12.7%. Serological study of 98 local people showed that 29.6% were seroreactive; most of their houses were closed to wild biotopes colonized by T. sordida.

Results indicate that there is an active T. infestans mediated transmission of Chagas disease in this zone that yields important human prevalence and that the populations of T. sordida in wild biotopes not only sustain the wild T. cruzi cycle but also represent an actual risk for people living in the area.

Key words: Triatoma infestans - Triatoma sordida - infestation - infection -seroprevalence - Argentina

In rural areas of Corrientes Province, Triatoma infestans (Klug 1834) is mainly found indoors and is also present in peridomestic premises (Bar et al. 1992, 1996b, 1997).

T. sordida (Stål 1859) colonizes wild biotopes (Bar et al. 1996a) as well as artificial ecotopes in peridomestic areas, sometimes coexisting with T. infestans and even established inside a rural house (Bar et al. 1992, 1996b). In Corrientes city it frequently invades houses and a large colony was captured in an urban ecotope (Bar et al. 1993).

Although intradomestic colonies of T. infestans have been eliminated from some areas of Corrientes province, T. sordida may replace it as a domestic vector. Integration of extradomestic triatomines to domestic transmission cycles has been occasionally reported in Minas Gerais, Brazil (Diotaiuti et al. 1993).

Anthropic environmental modification, mainly the replacement of natural forest by cultivated land, harvesting of wood and uncontrolled grazing may produce a concentration of wild mammals and triatomines in the peridomicile, generating local transmission cycles of Trypanosoma cruzi. Those foci can provide invading vectors to the domicile that can eventually carry trypanosomes (Wisnivesky-Colli et al. 1993). The peridomicile may represent a transition environment for triatomines coming from the wild and facilitate their domiciliation process (Gajate et al. 1996).

An important flood affected Corrientes Province in 1998, as a consequence of the El Niño phenomenon, which made the owners of the dwellings leave them temporarily. Most of the houses were rebuilt afterwards.

This entire situation contributed to the increase of the environmental disturbance.

In order to increase our knowledge on the ecology of domestic and wild triatomines, an entomological and serological survey was carried out in rural settlements of the Department of Concepción, Corrientes.

MATERIALS AND METHODS

RESULTS

DISCUSSION

REFERENCES

Table I | Table II

⁺Corresponding author. Fax: +54-3783-473930. E-mail: mebar@exa.unne.edu.ar

Received 5 March 2001

Accepted 23 August 2001