Control of Pyrethroid-Resistant Chagas Disease Vectors with Entomopathogenic Fungi

Chagas disease, also known as American Trypanosomiasis, is the most relevant parasitic disease in Latin America, being a major burden that affects mostly poor human populations living in rural areas. The kissing-bugs of the Triatominae family transmit the parasite Trypanosoma cruzi by infectious blood-sucking; Triatoma infestans is the vector of major relevance in the southern Cone of South America. Current control strategies, heavily based on residual insecticide spraying, are threatened by the emergence of pyrethroid-resistant bug populations. Furthermore, ensuring the long-term and sustainable control of this overwhelming disease remains a major challenge. Here we show the utility of a simple, low-cost, biological control methodology against T. infestans bugs, regardless of their susceptibility to pyrethroid insecticides. It is based on the understanding of the initial contact interactions between a mycoinsecticide agent—the fungus Beauveria bassiana—and the host defense barrier, the bug cuticle. The proposed methodology is also supported by present data showing a relationship between the triatomine cuticle width and its hydrocarbon surface components, with insecticide resistance. These results will help to provide a safe and efficient alternative to overcome pyrethroid-resilience of these noxious bugs. A high transfer potential to immediate application in rural communities located in remote areas inaccessible to sanitary control teams, and to the control of other Chagas disease vectors as well, is also envisaged

Strong Host-Feeding Preferences of the Vector Triatoma infestans Modified by Vector Density: Implications for the Epidemiology of Chagas Disease

Chagas disease is a complex zoonosis with more than 150 mammalian host species, nearly a dozen blood-sucking triatomine species as main vectors, and 9–11 million people infected with Trypanosoma cruzi (its causal agent) in the Americas. Triatoma infestans, a highly domesticated species and one of the main vectors, feeds more often on domestic animals than on humans in northern Argentina. The question of whether there are host-feeding preferences among dogs, cats, and chickens is crucial to estimating transmission risks and predicting the effects of control tactics targeting them. This article reports the first host choice experiments of triatomine bugs conducted in small huts under natural conditions. The results demonstrate that T. infestans consistently preferred dogs to chickens or cats, with host shifts occurring more frequently at higher vector densities. Combined with earlier findings showing that dogs have high infection rates, are highly infectious, and have high contact rates with humans and domestic bugs, our results reinforce the role of dogs as the key reservoirs of T. cruzi. The strong bug preference for dogs can be exploited to target dogs with topical lotions or insecticide-impregnated collars to turn them into baited lethal traps or use them as transmission or infestation sentinels

Distribution and pathogenicity of Trypanosoma cruzi isolated from peridomestic populations of Triatoma infestans and Triatoma guasayana from rural Western Argentina

We assessed the distribution of Trypanosoma cruzi infection in peridomestic triatomines collected manually at a district-wide scale in rural villages around Olta, Western Argentina, and typed the isolated strains according to their pathogenicity to laboratory mice. Of 1623 triatomines examined, only 14 (0.9%) were infected with T. cruzi based on microscopical examination of feces. The prevalence of T. cruzi infection was 0.8% in Triatoma infestans, 2.3% in T. guasayana, and nil in T. garciabesi, T. platensis, and T. eratyrusiformis. Local transmission occurred in kitchens, store-rooms and goat corrals or nearby, though at very low levels. T. cruzi was detected by at least one parasitological method in 11 (79%) of 14 microscope-positive bugs. Hemoculture was the most sensitive method (67%) followed by culture of organ homogenates, histopathology or xenodiagnosis of inoculated suckling mice (55-58%), and culture of microscope-positive bug feces (46%). The evidence suggests that most of the isolated T. cruzi strains would be myotropic type III. Our study establishes for the first time that peridomestic, microscope-positive T. guasayana nymphs were actually infected with T. cruzi, and may be implicated as a putative secondary vector of T. cruzi in domestic or peridomestic sites

Effectiveness of residual spraying of peridomestic ecotopes with deltamethrin and permethrin on Triatoma infestans in rural western Argentina: a district-wide randomized trial

Fil: Gürtler, Ricardo E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Laboratorio de Ecología General; Argentina.Fil: Canale, Delmi M. Coordinación Nacional de Control de Vectores; Argentina.Fil: Spillmann, Cynthia. Coordinación Nacional de Control de Vectores; Argentina.Fil: Stariolo, Raúl. Coordinación Nacional de Control de Vectores; Argentina.Fil: Salomón, Oscar D. ANLIS Dr.C.G.Malbrán. Centro Nacional de Diagnóstico e Investigación de Endemo-Epidemias; Argentina.Fil: Blanco, Sonia. Coordinación Nacional de Control de Vectores; Argentina.Fil: Segura, Elsa L. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Parasitología; Argentina.Objective: To compare the effectiveness of a single residual spraying of pyrethroids on the occurrence and abundance of Triatoma infestans in peridomestic ecotopes in rural La Rioja. Methods: A total of 667 (32.8%) peridomestic sites positive for T. infestans in May 1999 were randomly assigned to treatment within each village, sprayed in December 1999, and reinspected in December 2000. Treatments included 2.5% suspension concentrate (SC) deltamethrin in water at 25 mg active ingredient (a.i.)/m(2) applied with: (a) manual compression sprayers (standard treatment) or (b) power sprayers; (c) 1.5% emulsifiable concentrate (EC) deltamethrin at 25 mg a.i./m(2); and (d) 10% EC cis-permethrin at 170 mg a.i./m(2). EC pyrethroids were diluted in soybean oil and applied with power sprayers. All habitations were sprayed with the standard treatment. Findings: The prevalence of T. infestans 1-year post-spraying was significantly lower in sites treated with SC deltamethrin applied with manual (24%) or power sprayers (31%) than in sites treated with EC deltamethrin (40%) or EC permethrin (53%). The relative odds of infestation and catch of T. infestans 1-year post-spraying significantly increased with the use of EC pyrethroids, the abundance of bugs per site before spraying, total surface, and host numbers. All insecticides had poor residual effects on wooden posts. Conclusion: Most of the infestations probably originated from triatomines that survived exposure to insecticides at each site. Despite the standard treatment proving to be the most effective, the current tactics and procedures fail to eliminate peridomestic populations of T. infestans in semiarid rural areas and need to be revised

Effectiveness of residual spraying of peridomestic ecotopes with deltamethrin and permethrin on Triatoma infestans in rural western Argentina: a district-wide randomized trial.

OBJECTIVE: To compare the effectiveness of a single residual spraying of pyrethroids on the occurrence and abundance of Triatoma infestans in peridomestic ecotopes in rural La Rioja. METHODS: A total of 667 (32.8%) peridomestic sites positive for T. infestans in May 1999 were randomly assigned to treatment within each village, sprayed in December 1999, and reinspected in December 2000. Treatments included 2.5% suspension concentrate (SC) deltamethrin in water at 25 mg active ingredient (a.i.)/m(2) applied with: (a) manual compression sprayers (standard treatment) or (b) power sprayers; (c) 1.5% emulsifiable concentrate (EC) deltamethrin at 25 mg a.i./m(2); and (d) 10% EC cis-permethrin at 170 mg a.i./m(2). EC pyrethroids were diluted in soybean oil and applied with power sprayers. All habitations were sprayed with the standard treatment. FINDINGS: The prevalence of T. infestans 1-year post-spraying was significantly lower in sites treated with SC deltamethrin applied with manual (24%) or power sprayers (31%) than in sites treated with EC deltamethrin (40%) or EC permethrin (53%). The relative odds of infestation and catch of T. infestans 1-year post-spraying significantly increased with the use of EC pyrethroids, the abundance of bugs per site before spraying, total surface, and host numbers. All insecticides had poor residual effects on wooden posts. CONCLUSION: Most of the infestations probably originated from triatomines that survived exposure to insecticides at each site. Despite the standard treatment proving to be the most effective, the current tactics and procedures fail to eliminate peridomestic populations of T. infestans in semiarid rural areas and need to be revised

Effectiveness of residual spraying of peridomestic ecotopes with deltamethrin and permethrin on Triatoma infestans in rural western Argentina: a district-wide randomized trial

OBJECTIVE: To compare the effectiveness of a single residual spraying of pyrethroids on the occurrence and abundance of Triatoma infestans in peridomestic ecotopes in rural La Rioja. METHODS: A total of 667 (32.8%) peridomestic sites positive for T. infestans in May 1999 were randomly assigned to treatment within each village, sprayed in December 1999, and reinspected in December 2000. Treatments included 2.5% suspension concentrate (SC) deltamethrin in water at 25 mg active ingredient (a.i.)/m² applied with: (a) manual compression sprayers (standard treatment) or (b) power sprayers; (c) 1.5% emulsifiable concentrate (EC) deltamethrin at 25 mg a.i./m²; and (d) 10% EC cis-permethrin at 170 mg a.i./m². EC pyrethroids were diluted in soybean oil and applied with power sprayers. All habitations were sprayed with the standard treatment. FINDINGS: The prevalence of T. infestans 1-year post-spraying was significantly lower in sites treated with SC deltamethrin applied with manual (24%) or power sprayers (31%) than in sites treated with EC deltamethrin (40%) or EC permethrin (53%). The relative odds of infestation and catch of T. infestans 1-year post-spraying significantly increased with the use of EC pyrethroids, the abundance of bugs per site before spraying, total surface, and host numbers. All insecticides had poor residual effects on wooden posts. CONCLUSION: Most of the infestations probably originated from triatomines that survived exposure to insecticides at each site. Despite the standard treatment proving to be the most effective, the current tactics and procedures fail to eliminate peridomestic populations of T. infestans in semiarid rural areas and need to be revised

Exploration for Triatoma virus (TrV) infection in laboratory-reared triatomines of Latin America: a collaborative study

Triatoma virus (TrV) is a small, non-enveloped virus that has a +ssRNA genome and is currently classified under the Cripavirus genus of the Dicistroviridae family. TrV infects haematophagous triatomine insects (Hemiptera: Reduviidae), which are vectors of American Trypanosomiasis (Chagas disease). TrV can be transmitted through the horizontal fecal-oral route, and its infection causes either deleterious sublethal effects or even death of laboratory insect colonies. Various species of triatomines from different regions of Latin America are currently being reared in research laboratories, with little or no awareness of the presence of TrV; therefore, any biological conclusion drawn from experiments on insects infected with this virus is inherently affected by the side effects of its infection. In this study, we developed a mathematical model to estimate the sample size required for detecting a TrV infection. We applied this model to screen the infection in feces of triatomines belonging to insectaries from 13 Latin American countries, carrying out the identification of TrV by using reverse transcriptase PCR. TrV was detected in samples coming from Argentina, which is the country where several years ago the virus was first isolated from Triatoma infestans (Hemiptera: Reduviidae). Interestingly, several colonies from Brazil were also found infected with the virus. This positive result widens the TrV?s host range to a total of 14 triatomine species. Our findings suggest that many triatomine species distributed over a large region of South America may be naturally infected with TrV.Fil: Marti, Gerardo Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Estudios Parasitologicos y de Vectores. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Centro de Estudios Parasitologicos y de Vectores; ArgentinaFil: Echeverria, Maria Gabriela. Universidad Nacional de la Plata. Facultad de Ciencias Veterinarias. Departamento de Microbiología. Cátedra de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Susevich, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Estudios Parasitologicos y de Vectores. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Centro de Estudios Parasitologicos y de Vectores; ArgentinaFil: Ceccarelli, Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Estudios Parasitologicos y de Vectores. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Centro de Estudios Parasitologicos y de Vectores; ArgentinaFil: Balsalobre, Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Estudios Parasitologicos y de Vectores. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Centro de Estudios Parasitologicos y de Vectores; ArgentinaFil: Canale, Delmi Margarita. Centro de Referencia de Vectores, Coordinación Nacional de Control de Vectores, Pabellón Rawson-Hospital Colonia; ArgentinaFil: Stariolo, Raúl Luis. Centro de Referencia de Vectores, Coordinación Nacional de Control de Vectores, Pabellón Rawson-Hospital Colonia; ArgentinaFil: Guérin, Diego M. A.. Universidad del País Vasco; España. Consejo Superior de Investigaciones Cientificas; España. Universidad Politécnica de Valencia; EspañaFil: González Cifuentes, Nadia L.. Universidad de Los Andes; ColombiaFil: Guhl, Felipe. Universidad de Los Andes; ColombiaFil: Bacigalupo, Antonella. Universidad de Chile; ChileFil: Cattan, Pedro E.. Universidad de Chile; ChileFil: Garcıa, Alejandro. Secretaria Regional Ministerial de Salud de Coquimbo; ChileFil: Villacis, Anita G.. Pontificia Universidad Catolica del Ecuador; EcuadorFil: Grijalva, Mario J.. Pontificia Universidad Catolica del Ecuador; Ecuador. Ohio University; Estados UnidosFil: Solorzano, Elizabeth. Universidad de San Carlos; GuatemalaFil: Monroy, Carlota. Universidad de San Carlos; GuatemalaFil: Espinoza Blanco, Yrma. Universidad Nacional Mayor de San Marcos; PerúFil: Cordova Benzaquen, Eleazar. Universidad Nacional San Agustín de Arequipa; PerúFil: Ruelas llerena, Nancy. Universidad Nacional San Agustín de Arequipa; PerúFil: Guzmán loayza, Miriam. Dirección Regional de Salud Moquegua; PerúFil: Caceres, Abraham G.. Universidad Nacional Mayor de San Marcos; PerúFil: Vences Blanco, Mauro O.. Universidad Nacional Autónoma de México; MéxicoFil: Salazar Schettino, Paz María. Universidad Nacional Autónoma de México; MéxicoFil: Martínez Martínez, Ignacio. Universidad Nacional Autónoma de México; MéxicoFil: Espinoza Gutiérrez, Bertha. Universidad Nacional Autónoma de México; MéxicoFil: Mojoli, Andrés. Centro para el Desarrollo de la Investigación Científica. Asunción; ParaguayFil: Rojas de Arias, Antonieta. Centro para el Desarrollo de la Investigación Científica. Asunción; ParaguayFil: Feliciangeli, M. Dora. Universidad de Carabobo Maracay; VenezuelaFil: Rivera Mendoza, Pedro. Fundación para el Desarrollo; NicaraguaFil: Rozas Dennis, Gabriela Susana. Universidad Nacional del Sur; ArgentinaFil: Sánchez Eugenia, Rubén. Unidad de Biofísica; EspañaFil: Aguirre, Jon. Unidad de Biofísica; España. Fundación Biofísica Bizkaia; EspañaFil: Viguera, Ana R.. Unidad de Biofísica; EspañaFil: Hernádez Suárez, Carlos M.. Universidad de Colima; México. Unidad Monterrey; MéxicoFil: Vilchez, Susana. Universidad de Granada; EspañaFil: Osuna, Antonio. Universidad de Granada; EspañaFil: Gorla, David Eladio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de la Rioja. - Secretaria de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Mougabure Cueto, Gastón Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; ArgentinaFil: Esteban, Lidia. Universidad Industrial Santander; ColombiaFil: Angulo, Vıctor M.. Universidad Industrial Santander; ColombiaFil: Querido, Jailson F. B. Unidad de Biofísica; España. Fundación Biofísica Bizkaia; España. Universidad Nova de Lisboa; PortugalFil: Silva, Marcelo S.. Universidad Nova de Lisboa; PortugalFil: Marques, Tatiane. Universidade Federal do Triangulo Mineiro; BrasilFil: Anhe, Ana Carolina B. M.. Universidade Federal do Triangulo Mineiro; BrasilFil: Gomez Hernandez, Cesar. Universidade Federal do Triangulo Mineiro; BrasilFil: Ramirez, Luis E.. Universidade Federal do Triangulo Mineiro; BrasilFil: Rabinovich, Jorge Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Estudios Parasitologicos y de Vectores. Universidad Nacional de la Plata. Facultad de Cs.naturales y Museo. Centro de Estudios Parasitologicos y de Vectores; ArgentinaFil: Diotaiuti, Liléia. Centro de Pesquisas Rene Rachou-FIOCRUZ; BrasilFil: Guerin Aguilar , Diego Marcelo. Universidad del País Vasco; España. Unidad de Biofísica; España. Fundación Biofísica Bizkaia; Españ