Triatomines are hematophagous insects belonging to the family Reduviidae and subfamily Triatominae1. They are epidemiologically important because they transmit the protozoan Trypanosoma cruzi, the etiologic agent of American trypanosomiasis, also known as Chagas disease2,3. In Brazil, there are ten genera of Triatominae, namely, Alberprosenia, Belminus, Cavernicola, Eratyrus, Microtriatoma, Panstrongylus, Parabelminus, Psammolestes, Rhodnius, and Triatoma4. All these genera are potential vectors for parasites.
In the Brazilian Amazon, at least 20 species of sylvatic triatomines belonging to eight genera have been identified, of which more than 10 are infected with trypanosomatids1,5,6. In the State of Rondonia, there have been reports of six triatomine species belonging to three genera, namely, Rhodnius montenegrensis1, Rhodnius robustus, Rhodnius pictipes, Rhodnius milesi, Panstrongylus geniculatus2,8, and Eratyrus mucronatus6. The present study is the first report on the presence of Panstrongylus lignarius, collected inside a house, in the State of Rondonia.
In November 2016, a male specimen of P. lignarius (Figure 1) was collected from an apartment (Lat. 8°47′38′′S, Long. 63°55′10′′W) located in Vila Candelaria neighborhood in the municipality of Porto Velho, Rondonia, Brazil. The apartment was on the second floor of a condominium and had been in existence for about 3 years. The condominium was a few meters away from a forest reserve, with many palm trees. The identification of the triatomine species was done in the Laboratory of Tropical Medicine of Universidade Federal do Acre (UFAC), Rio Branco, Acre, Brazil, based on the keys previously described by Lent & Wygodzinsky9.
The specific epithet “lignarius” comes from the Latin word “lignum” meaning “wood,” a reference to the coloration of the insect being similar to that of wood10. P. lignarius has an overall light brown color dorsally, ferruginous, dark brown or black ventrally, with dark brown to black markings on the dorsal surface complex present on head, neck, pronotum, scutellum, hemelytra, and connexivum; legs are ferruginous or black, with yellow markings, and the body surface has very short and inconspicuous golden setae9.
In the same apartment where the P. lignarius specimen was collected, 17 other triatomines were also collected over a period of one year; however, all of them belonged to the genus Rhodnius. It is believed that the triatomines arrived at the apartment attracted by the lights. These wild Amazonian species are considered opportunistic; they fly from their wild ecotopes to the houses, but do not colonize, most of the time11.
The forest reserve near the apartment is about 700m from the edge of the Madeira River. It is characterized as an open ombrophilous forest containing palms (Attalea speciosa) over an area of 4,800m2, surrounding the apartment complex. The occurrence of bromeliads, birds’ nest, rodents, and marsupials, which are reported to be associated with P. lignarius, is common in this area9,10,12. Beyond this stretch of forest, totally devastated and anthropized area with constructions is present. In this environment, it is possible to visualize the interaction of other animal species, such as mammals, primates, rodents, marsupials, xenarthrans, chiropterans, birds ̶ Passeriformes, Columbiformes, Falconiformes, and Ciconiiformes, various reptiles, amphibians, and other arthropods, which are typical of forests in the Amazon.
The feces of specimen were diluted in saline solution, mounted on microscope slides, and then examined under an optical microscope (1,000× magnification). Flagellates, similar to T. cruzi, were identified; however, no molecular analysis was performed to confirm the trypanosomatid species.
In Brazil, besides the present record from the State of Rondonia, P. lignarius has been recorded in the States of Amazonas, Maranhão, Pará, Tocantins9,10,12, Mato Grosso13, and Amapa14 (Figure 2). The occurrence of this species was also registered in Ecuador, Peru, Guyana, French Guiana, Suriname, and Venezuela10,12.
The presence of one more triatomine species in the State of Rondonia increases the total number of species found in this area from six to seven. This finding is alarming because in some regions of Peru, P. lignarius(previously known as P. herreri) is considered to be the major cause for the Chagas disease15, it being the second epidemiologically important species, with the highest domiciliation index13.