First report of Triatoma sordida Stål, 1859 (Hemiptera, Reduviidae, Triatominae) in the State of Acre and Brazilian Western Amazon

Abstract

INTRODUCTION

The occurrence of Triatoma sordida in the Brazilian Western Amazon is reported for the first time.

METHODS

Triatoma sordida specimens were collected from a Gallus gallus nest in a peridomiciliary area of Senador Guiomard municipality in the state of Acre.

RESULTS

The number of triatomine species in Acre increased from six to seven with this first report of T. sordida in the Brazilian Western Amazon.

CONCLUSIONS

The occurrence of T. sordida in Acre is of concern since it is among the most captured triatomines in peridomiciliary environments in Brazil, and carries a high potential for vector transmission.

Keywords:
Triatomines; Chagas disease; Trypanosomatids

Triatominae (Hemiptera, Reduviidae, Triatominae) are insects of medical importance, since they can transmit Trypanosoma cruzi, the etiologic agent of American trypanosomiasis, also known as Chagas disease¹, which affects approximately 12 million people, with a further 60 million people living in areas of risk around the world².

In the Brazilian Amazon, there are at least 20 species of wild triatomines³, among which six species distributed in three genera are recorded in the state of Acre: Rhodnius montenegrensis⁴, Rhodnius stali⁵, R. robustus⁶, R. pictipes, Panstrongylus geniculatus³, and Eratyrus mucronatus⁷.

This study reports for the first time the occurrence of the species Triatoma sordida in the state of Acre and the Brazilian Western Amazon; this is also the first record of the genus Triatoma for the State of Acre.

Two specimens, adult T. sordida males (Figure 1), were collected at the Catuaba Experimental Reserve, Senador Guiomard, Acre, Brazil (10° 09ʹ 03ʹʹ S 67° 44ʹ 09ʹʹ W), an area belonging to the Federal University of Acre (UFAC). The insects were collected during May 2016, through active searches in Gallus gallus nests in the peridomiciliary area of an old farm house, built with wood and covered with palm tree thatching. The building is situated in the middle of a secondary forest fragment, surrounded by palms of the genera Attalea, Euterpe, and Bactris.

FIGURE 1:
Triatoma sordida collected in the Catuaba Experimental Reserve. (A and B): dorsal view; (C and D): ventral view.

The triatomines were sent to the Laboratory of Tropical Medicine (LABMEDT) at UFAC, where the taxonomic identification was carried out based on external morphological characteristics, as described by Lent and Wygodzinsky⁸. Trypanosomatid infection was also analyzed by diluting the triatomine feces in saline solution, preparing them on microscope slides, and then examining them under light microscopy (1,000× magnification) after staining with triarylmethane (0.1%), xanthene (0.1%), and thiazine (0.1%).

The occurrence of this species in nests is already known, as it has recently been found in bird and mammal nests in the Brazilian Pantanal region^2,9. However, the discovery in poultry nests, such as those of G. gallus, generates a concern due both to the proximity of these animals to humans, especially species that have a high frequency of infection by T. cruzi¹⁰, and the findings of the present study, because the two specimens collected tested positive for trypanosomatids, although no molecular analysis was performed to confirm the species.

Three adult specimens of T. sordida (Figure 2), two males and one female, were located in the entomological collection of the Department of Entomology of the State Department of Health, Acre, but they had been mistakenly identified as Triatoma matogrossensis. According to the Department’s registry, these specimens were collected and delivered by residents living in the periurban region of the municipality of Rio Branco, Acre, from the Calafate neighborhood, but with no exact description of the locality or date of collection.

FIGURE 2:
Specimens of Triatoma sordida stored in the Department of Entomology of the State Health Department of Acre. (A): dorsal view; (B), (C) and (D):: ventral view.

The presence of another species of triatomine occurring in Acre increases the total number of species in the state from six to seven, and the number of genera from three to four. The new record also increases the geographic distribution of T. sordida, since it has been described for the states of Bahia, Goiás, Maranhão, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Paraná, Pernambuco, Piauí, Rio Grande do Sul, Santa Catarina, São Paulo, and Tocantins^3,10.

Although T. sordida is not reported to occur in the states neighboring Acre (Rondônia and Amazonas), this species does occur in Bolívia¹¹, a country neighboring Acre. A study carried out in Velasco Province in the north of the Department of Santa Cruz, Bolívia, showed that 58% of the residences were occupied by T. sordida, 21.4% of which were infected by T. Cruzi¹². This domiciliation behavior has also been observed in other regions of the Department of Santa Cruz, La Paz, and the Bolivian Chaco region^13,14.

This new report for Acre is worrying, because T. sordida is considered the most frequently captured species in peridomiciliary environments in Brazil¹⁰. When evaluating the rate at which T. sordida is infected by T. cruzi, it has been observed that this species and Triatoma infestans, Triatoma brasiliensis, Triatoma pseudomaculata, and Panstrongylus megistus are the five species with the highest participation in home transmission of American trypanosomiasis^10,15. Vigilance services must remain active in order to prevent the wider dispersion of T. sordida in western Amazonia, given the spread of Chagas disease in this region.

Ethical considerations

The specimens were collected with permission from the Brazilian Institute of Environment and Renewable Natural Resources [Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA)]; permanent license Nr. 52260-1.

Acknowledgments

The authors are grateful to Fundação de Amparo à Pesquisa do Estado do Acre (FAPAC) for the financial assistance and Pró-Reitoria de Pesquisa e Pós-Graduação da Universidade Federal do Acre (UFAC), for help in translation into English.

REFERENCES

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• Financial support:Programa Pesquisa Para o SUS: Gestão Compartilhada em Saúde (PPSUS) 001/2015 - Fundação de Amparo à Pesquisa do Estado do Acre (FAPAC).

Publication Dates

• Publication in this collection
  Jan-Feb 2018

History

• Received
  28 Apr 2017
• Accepted
  18 Sept 2017