Triatomines are hematophagous insects belonging to the Reduviidae family and the Triatominae subfamily1. They are found throughout South and Central America and are of epidemiological importance as they are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease (American trypanosomiasis)1. These vectors may also transmit the protozoan, Trypanosoma rangeli, to vertebrates; although this species does not cause symptoms of infection in humans, it may complicate differential diagnosis of T. cruzi2.
Currently, 154 triatomine species, grouped into 19 genera3–5, have been identified worldwide. Of these, over 30 species, distributed among nine genera, occur within the Amazon region6. In the Brazilian state of Amazonas, ten species, distributed among four genera, were previously recorded: Cavernicola lenti Barrett and Arias, 1985, Eratyrus mucronatus Stal, 1859, Panstrongylus geniculatus (Latreille, 1811), P. lignarius (Walker, 1873), P. rufotuberculatus (Champion, 1899), Rhodnius amazonicus Almeida, Santos, and Sposina, 1973, R. brethesi Matta, 1919, R. paraensis Sherlock, Guitton and Miles, 1977, R. pictipes Stal, 1872 and R. robustus Larrousse, 19277. The present article reports the first occurrence of R. montenegrensis in the Brazilian state of Amazonas.
In January 2019, using a dissection technique, triatomines were collected from four Attalea butyracea palm trees (commonly referred to as Jaci or coquinho da mata in the Amazon region) in a rural area of the municipality of Guajará, Amazonas, near the river Juruá (latitude 07º 30′ 87”S, longitude 72º31’17”W). This municipality is located in the meso-region of the southwestern Amazon and the micro-region of Juruá.
Two triatomines were collected and transferred to the Laboratory of Tropical Medicine at the Federal University of Acre (UFAC) in the city of Rio Branco, Acre, where they were identified based on their morphological characteristics, previously described by Lent and Wygodzinsky8 and Rosa et al.9. These two specimens were subsequently identified as female R. montenegrensis and referred to the Entomology Laboratory of the Department of Biological Sciences, School of Pharmaceutical Sciences, Paulista State University Júlio de Mesquita Filho (UNESP), Araraquara, São Paulo, Brazil, where the species were further confirmed by genital charactersistics10 (Figure 1A-D). These R. montenegrensis individuals (two adult females, municipality of Guajará, Amazonas, Brazil, latitude 07º 30′ 87”S, longitude 72º31’17”W, Madeira, F.P, col. Oliveira J, det.) were then added to the Triatominae collection, “Dr Jose Maria Soares Barata” (CTJMSB) of the UNESP, Araraquara.
Collected R. montenegrensis individuals were mainly yellow in color with black longitudinal stripes on the pronotum, wings, and connexivum9 (Figure 1A). Markings on the head included a distinct central yellow band between two continuous brown bands; stains from the climax regions to the neck were not present9 (Figure 1B). Legs were yellow in color, except for the posterior tibias, which had a black stripe near the tarsus9(Figure 1A).
R. montenegrensis specimens were further analyzed for Trypanosoma sp. infection. Fresh intestinal content in a 0.9% saline solution was examined using optical microscopy (400x magnification)11. R. montenegrensis specimens were not positive for trypanosomatids, however.
This is the first report of R. montenegrensis in Amazonas. This species was first described in the municipality of Monte Negro, Rondônia9, and it was further recorded in two meso-regions in the state of Acre1,12. Given the results of the present report, the number of triatomines occurring in the state of Amazonas has increased from 10 to 11, expanding the distribution of this species in Brazil, which previously only comprised the states of Rondônia and Acre (Figure 2).
Although in the present study, R. montenegrensis specimens were not infected by trypanosomatids, this species is nonetheless a potential vector for transmission of this etiological agent given that its infection by T. cruzi13 and T. rangeli2 was previously confirmed. R. montenegrensis individuals infected by T. rangeli were further found inside apartments in the state of Acre, but without evidence of domiciliation14.
The occurrence of T. cruzi-infected R. montenegrensis individuals indicates that this triatomine has an active role in the maintenance of the enzootic cycle of this trypanosomatid13,15, thus reinforcing the need for further studies on R. montenegrensis occurrence to further elucidate its distribution and overall ecology.