Communication/comunicação Natural Infection of Triatomines (hemiptera: Reduviidae) by Trypanosomatids in Two Different Environments in the Municipality of Ouro Preto Do Oeste, State of Rondônia, Brazil

Infecção natural de triatomíneos (Hemiptera: Reduviidae) por tripanosomatídeos em dois ambientes distintos no município de Ouro Preto do Oeste, Estado de Rondônia, Brasil ABSTRACT Introduction: This study analyzed the occurrence and the contamination of triatomines by trypanosomatids in Orbignya speciosa (babassu) specimens in the State of Rondônia, Brazil, in two different environments (pasture and woods). Methods: Capture of triatomines on babassus and microscopic search for trypanosomatids in their digestive tube were carried out. Results: Four hundred ninety-four (494) specimens were captured (Rhodnius prolixus and R.robustus), of which 35.6% of the triatomines were positive for trypanosomatids. Conclusions: The high index of natural infection along with the abundance of triatomines points out to the necessity to create an epidemiological surveillance system to monitor vector-borne transmission and deepen the studies on the ecology of such vectors in the Amazon.

Triatomines, also known as conenose bugs, kissing bugs, or assassin bugs, are insects largely spread throughout the Americas and are found from the South of the United States through the South of Argentina.They are of great importance, as they may convey the South American Trypanosomiasis, also called Chagas' disease 1 .
Many studies have pointed out the importance of babassus as a natural biotope, as they shelter a diversity of mammalian fauna such as bats, rats, opossums, and monkeys, besides snakes, birds, scorpions, amphibians, and a great variety of arthropods 3 .Such environment embodies a combination of shelter and food resources for the growth and procreation of triatomines, specially the species of the genus Rhodnius 3 , whose distribution on the sylvatic environment is strongly related to the distribution of palm trees 4 .On the other hand, the species of the Triatoma and Panstrongylus genus live rather in association with terrestrial hosts 5 .Over their evolutionary processes, only few species have adapted themselves to households and peridomiciliar animals 6 .
This study aimed to analyze the occurrence and the contamination of triatomines found in palm trees, such as Orbignya speciosa (babassu), by trypanosomatids in two different environments (primary forest and pasture) in the State of Rondônia, Brazil.
The study was carried out in the municipality of Ouro Preto do Oeste (S10º44'53," W62º12'57"), located in the State of Rondônia, whose population is estimated to be at 36,725 inhabitants settled in a 1,970-km 2 area (population density of 18.6 inhabitant/km 2 ), located at 325km from the state capital, the City of Porto Velho (Figure 1).
The research was carried out in two different environments one in a primary forest and the other in a pasture area.The collection of insects was done twice a month one in each environment within the period from February 2009 to January 2010, totaling 24 collections.
The babassus were cut off with a chain saw.Then, the bracts (where a large quantity of invertebrates and small vertebrates can inhabit) were taken off one-by-one in order to facilitate the capture of triatomines (Figure 2).The triatomines picked-up were sorted according to their nymphal stage and were then sent to the Centro Universitário Luterano de Ji-Paraná/Universidade Luterana do Brasil (CEULJI/ ULBRA) -The Microscopy Laboratory of the Lutheran University Center of Ji-Parana (S10°51'48," W 61° 57'35") -in thermal boxes at room temperature where the digestive tube content was diluted in saline solution, prepared on microscope slides, and then examined with a microscope using a 16x and 40x objective lenses.The microscopic examination was rigorous, covered the whole slide, and was considered positive when flagellated protozoa were found.
Then, the smears were soaked in methanol, stained with Giemsa, and again observed by optical microscopy to confirm their positivity for the presence of trypanosomatids.
In the 24 examined babasuss, a total of 494 triatomines were found -78 in the 12 babasuss of the primary forest and 416 in the other 12 babassus of the pasture area.In both environments, 100% of the babassus picked-out were found to be positive for triatomines (Figure 3).

FIGURE 1 -
FIGURE 1 -Geographical location of the municipality of Ouro Preto do Oeste, State of Rondônia, Brazil.

FIGURE 2 -
FIGURE 2 -Active search for triatomines on Orbignya speciosa (babassu).A: Cutting off the bracts; B: Triatomine mating during the collection procedure; C: A triatomine being picked up.

FIGURE 3 -
FIGURE 3 -Triatomines captured on Orbignya speciosas (babassu) located in a primary forest and pasture area, from February 2009 to January 2010, and the pluvial monthly average precipitation in the municipality of Ouro Preto do Oeste, State of Rondônia, Brazil.