Smoke of Capsicum baccatumL. var. baccatum (Solanaceae) repels nymphs of Triatoma infestans(Klug) (Hemiptera: Reduviidae)

Control of the Chagas disease vector, Triatoma infestans(Klug) (Hemiptera: Reduviidae) with synthetic pesticides in Bolivia has become increasingly inefficient due to the development of resistance in the insects. In the Chaco region of Bolivia, guaraní populations have approached the problem by fumigating their houses with the smoke of native plants. Through interviews and field work with local guides, the main plant used by the guaraníes was collected and later identified as Capsicum baccatumL. var. baccatum(Solanaceae). In choice bioassays, filter papers exposed to the smoke of the plant repelled nymphs of T. infestans. Activity remained significant after storing the exposed filter papers for 9 days. Chemical analysis of smoke and literature data suggested that capsaicinoids present in the smoke were responsible for the repellent effect. The data presented provide a rationale for the use of C. baccatumvar. baccatumto control the Chagas vector bythe guaraní populations.

Feeding-Induced Changes of Bacteriolytic Activity and the Pattern of Bacteriolytic Compounds in the Stomach and Small Intestine of the Haematophagous Bug Triatoma infestans (Klug, 1834) (Reduviidae, Triatominae)

Intestinal homeostasis mechanisms of the haematophagous triatomines regulate the development of mutualistic symbionts and other gut bacteria. Investigating antimicrobial compounds of these insects, we have determined spectrophotometrically that the bacteriolytic activity is between pH 3 and pH 9 using homogenates of fifth instar Triatoma infestans stomachs and small intestines from unfed bugs and up to 50 days after feeding. The activity against Gram-positive Micrococcus luteus was strongest at pH 4 and pH 7 and was higher in the stomach than in the small intestine. Symbiotic Rhodococcus triatomae were not lysed. Lysis of Gram-negative Escherichia coli showed a maximum at pH 7 in the stomach and at pH 5 in the small intestine. Bacteriolytic activity against both M. luteus and E. coli was reduced 24 h after feeding, then increased, and at 50 days after feeding was strongly reduced. In zymographs, the activity against M. luteus was mainly correlated to proteins of about 16 kDa. At different periods of time after feeding, seven bands of lysis appeared between 15 and 40 kDa and more bands using extracts of the small intestine than those of the stomach. This is the first proof for the synthesis of antibacterial proteins of 22–40 kDa in triatomines.

Trypanosoma cruzi Parasite Load Modulates the Circadian Activity Pattern of Triatoma infestans

American trypanosomiasis is a disease caused by the flagellate protozoan Trypanosoma cruzi, which is transmitted mainly in endemic areas by blood-sucking triatomine vectors. Triatoma infestans is the most important vector in the southern cone of South America, exhibiting a nocturnal host-seeking behavior. It has been previously documented that the parasite produces changes in some triatomine species, but this is the first time that the behavior of a vector has been evaluated in relation to its parasite load. After comparing the movement events and distance traveled of infected and non-infected T. infestans, we evaluated the change produced by different T. cruzi parasite loads on its circadian locomotor activity. We observed differences between infected and non-infected triatomines, and a significant relation between the parasite load and the increase in locomotor activity of T. infestans, which was accentuated during the photophase. This could have direct implications on the transmission of T. cruzi, as the increased movement and distance traveled could enhance the contact of the vector with the host, while increasing the predation risk for the vector, which could both constitute a risk for vectorial and oral transmission to mammals.

Transcriptomic modulation in response to an intoxication with deltamethrin in Triatoma infestans, vector of Chagas disease

Background: Triatoma infestans is the main vector of Chagas disease in the Southern Cone. The resistance to pyrethroid insecticides developed by populations of this species impairs the effectiveness of vector control campaigns in wide regions of Argentina. The study of the global transcriptomic response to pyrethroid insecticides is important to deepen the knowledge about detoxification in triatomines. Methodology and findings: We used RNA-Seq to explore the early transcriptomic response of T. infestans after intoxication with deltamethrin. We were able to assemble a complete transcriptome of this vector and found evidence of differentially expressed genes belonging to diverse families such as chemosensory and odorant-binding proteins, ABC transporters and heat-shock proteins. Moreover, genes related to transcription and translation, energetic metabolism and cuticle rearrangements were also modulated. Finally, we characterized the repertoire of previously uncharacterized detoxification-related gene families in T. infestans and Rhodnius prolixus. Conclusions and significance: Our work contributes to the understanding of the detoxification response in vectors of Chagas disease. Given the absence of genomic information from T. infestans, the analysis presented here constitutes a resource for molecular and physiological studies in this species. The results increase the knowledge on detoxification processes in vectors of Chagas disease, and provide relevant information to explore new potential insecticide resistance mechanisms in these insects.

Near infrared spectroscopy accurately detects Trypanosoma cruzi non-destructively in midguts, rectum and excreta samples of Triatoma infestans

Chagas disease is a neglected tropical disease caused by Trypanosoma cruzi parasite with an estimated 70 million people at risk. Traditionally, parasite presence in triatomine vectors is detected through optical microscopy which can be low in sensitivity or molecular techniques which can be costly in endemic countries. The aim of this study was to evaluate the ability of a reagent-free technique, the Near Infrared Spectroscopy (NIRS) for rapid and non-invasive detection of T. cruzi in Triatoma infestans body parts and in wet/dry excreta samples of the insect. NIRS was 100% accurate for predicting the presence of T. cruzi infection Dm28c strain (TcI) in either the midgut or the rectum and models developed from either body part could predict infection in the other part. Models developed to predict infection in excreta samples were 100% accurate for predicting infection in both wet and dry samples. However, models developed using dry excreta could not predict infection in wet samples and vice versa. This is the first study to report on the potential application of NIRS for rapid and non-invasive detection of T. cruzi infection in T. infestans in the laboratory. Future work should demonstrate the capacity of NIRS to detect T. cruzi in triatomines originating from the field.

Infección de Rattus rattus por Trypanosoma cruzi como indicador del control vectorial en Arequipa, Perú

Como parte del programa de control de la enfermedad de Chagas en la región Arequipa, se vienen realizando rociados residuales, con deltametrina PM 5%, y entre los criterios para evaluar la interrupción de la transmisión vectorial, no se considera la infección natural de los roedores sinantrópicos por T. cruzi. El objetivo fue determinar el índice de infección natural por T. cruzi en el roedor sinantrópico R. rattus, antes y después del rociado residual de las viviendas con deltametrina PM 5%, como indicador del impacto del control vectorial de la enfermedad de Chagas. Se diseñó un estudio cuasi-experimental, a través de capturas de roedores en la etapa pre-rociado en el intradomicilio y capturas de roedores en la etapa post-rociado, en la localidad rural de Murco (Caylloma, Arequipa). Se les aplicó xenodiagnóstico por animal, con 10 ninfas III de Triatoma infestans. Los roedores fueron identificados como R. rattus y el índice de infección por el hemoflagelado identificado como T. cruzi, en el pre-rociado fue 84,2% y en el post- -rociado fue 0%. Además, en el pre-rociado el 50.0% (2/4) de Mus musculus fueron positivos a T. cruzi. Se concluye que la negativización de R. rattus en el post-rociado, indicaría la notable reducción de la transmisión o la interrupción de la transmisión vectorial de T. cruzi en la localidad de Murco.