Raquel Aparecida Ferreira

Chemical communication in chagas disease vectors. source, identity, and potential function of volatiles released by the metasternal and Brindley's glands of Triatoma infestans adults

Compounds from the metasternal and Brindleys glands of the blood-sucking bug, Triatoma infestans, were identified by solid phase microextraction (SPME) and gas chromatography-mass spectrometry. Volatile compounds released by adult bugs during copulation or after mechanical disturbance were also characterized. Six compounds were identified and found consistently in all samples from metasternal glands. The most abundant were 3-pentanone, 2-methylbutanol, 3-pentanol, and an unidentified compound. The metasternal gland blends did not differ qualitatively between sexes. Compounds found in Brindleys glands were short chain acids, alcohols, esters, and a ketone with no qualitative differences between sexes. Isobutyric acid was the main component of this blend, and two new confirmed compounds were described as products of these glands: 2-butanone and 2-methylbutyric acid. 3-Pentanone was collected from the headspace over 33% of the copulating pairs of T. infestans. Volatiles found in the headspace of disturbed T. infestans adults included short-chain fatty acids, alcohols, esters, and ketones, with no qualitative differences between sexes. Both types of glands apparently discharge their contents after disturbance. However, most of the volatiles released by bugs after disturbance came from Brindleys glands. The locomotor activity of fourth instars increased significantly after stimulation with the odors emitted by disturbed adults, as compared with larvae stimulated by the odor of undisturbed adults or by clean air. We also studied the directional behavioral response of fifth instars to the disturbance scent in a locomotion compensator. Larvae exposed to volatiles released by disturbed adults walked away from the direction of the odor. The results suggest that this blend or part of it functions as an alarm pheromone for T. infestans. We suggest that the metasternal glands of this species are involved both in the sexual and the alarm contexts, and that the Brindleys glands probably have both alarm and defensive roles.

Do Haematophagous Bugs Assess Skin Surface Temperature to Detect Blood Vessels

Background It is known that some blood-sucking insects have the ability to reach vessels under the host skin with their mouthparts to feed blood from inside them. However, the process by which they locate these vessels remains largely unknown. Less than 5% of the skin is occupied by blood vessels and thus, it is not likely that insects rely on a “random search strategy”, since it would increase the probability of being killed by their hosts. Indeed, heterogeneities along the skin surface might offer exploitable information for guiding insects bites. Methodology/Principal Findings We tested whether the bug Rhodnius prolixus can evaluate temperature discontinuities along the body surface in order to locate vessels before piercing the host skin. When placed over a rabbit ear, the bugs first bites were mostly directed towards the main vessels. When insects were confronted to artificial linear heat sources presenting a temperature gradient against the background, most bites were directly addressed to the warmer linear source, notwithstanding the temperature of both, the source and the background. Finally, tests performed using uni- and bilaterally antennectomized insects revealed that the bilateral integration of thermal inputs from both antennae is necessary for precisely directing bites. Conclusions/Significance R. prolixus may be able to exploit the temperature differences observed over the skin surface to locate blood vessles. Bugs bite the warmest targets regardless of the target/background temperatures, suggesting that they do not bite choosing a preferred temperature, but select temperature discontinuities along the skin. This strategy seems to be an efficient one for finding blood vessels within a wide temperature range, allowing finding them on different hosts, as well as on different areas of the host body. Our study also adds new insight about the use of antennal thermal inputs by blood sucking bugs.

Substrate texture properties induce triatomine probing on bitten warm surfaces

BackgroundIn this work we initially evaluated whether the biting process of Rhodnius prolixus relies on the detection of mechanical properties of the substrate. A linear thermal source was used to simulate the presence of a blood vessel under the skin of a host. This apparatus consisted of an aluminium plate and a nickel-chrome wire, both thermostatized and presented at 33 and 36°C, respectively. To evaluate whether mechanical properties of the substrate affect the biting behaviour of bugs, this apparatus was covered by a latex membrane. Additionally, we evaluated whether the expression of probing depends on the integration of bilateral thermal inputs from the antennae.ResultsThe presence of a latex cover on a thermal source induced a change in the biting pattern shown by bugs. In fact, with latex covered sources it was possible to observe long bites that were never performed in response to warm metal surfaces. The total number of bites was higher in intact versus unilaterally antennectomized insects. These bites were significantly longer in intact than in unilaterally antennectomized insects.ConclusionsOur results suggest that substrate recognition by simultaneous input through thermal and mechanical modalities is required for triggering maxillary probing activity.

Leishmaniose tegumentar americana entre os indígenas Xakriabá: imagens, ideias, concepções e estratégias de prevenção e controle

A leishmaniose tegumentar americana (LTA) e uma doenca infecciosa em expansao na comunidade indigena Xakriaba, localizada no Norte de Minas Gerais, devido as suas caracteristicas ambientais e condicoes precarias. Sua importância como problema de saude publica entre esses indigenas reside nao apenas na elevada incidencia, como tambem nos transtornos que ocasiona a vida dos individuos afetados. O presente estudo teve como objetivo identificar imagens, ideias, concepcoes, atitudes e condicoes relacionadas as praticas de prevencao e cuidado da LTA na comunidade Xakriaba. Foram realizadas entrevistas com liderancas indigenas, profissionais de saude, gestores do campo da saude e educacao; grupos focais com profissionais de saude e educacao, alem de usuarios do Sistema Unico de Saude. As falas foram gravadas mediante assinatura de um Termo de Consentimento Livre e Esclarecido. As gravacoes foram transcritas e analisadas segundo a tecnica de analise de conteudo. A partir do conteudo apreendido das falas definiram-se as seguintes categorias: imagens, ideias e concepcoes acerca da doenca; compreensao sobre elementos do ciclo da doenca; aspectos socioeconomicos e culturais que dificultam a sua prevencao. Evidenciou-se que a prevencao e o controle da LTA na Aldeia Indigena Xakriaba nao e um problema simples de ser solucionado. Assim, acoes educativas constituem importantes ferramentas para a compreensao da doenca, bem como formulacao e implementacao de estrategias de prevencao. Portanto, e de suma importância, antes de qualquer intervencao na comunidade, a apreensao das concepcoes, imagens e ideias que essa populacao tem acerca da LTA, para entao, com ela, construir estrategias de controle e prevencao.