Visceral Leishmaniasis Caused by Leishmania infantum in Salta, Argentina: Possible Reservoirs and Vectors.

Cases of human visceral leishmaniasis (HVL) were not recorded until recently in the Chaco region of northwestern Argentina. Dogs were surveyed at the sites of infection of two HVL index cases in the Chaco region of Salta province. Canine cases (CanL) were diagnosed by two parasitological methods, two molecular methods targeting mini- and maxicircle DNA, and immunochromatographic dipstick. Among 77 dogs studied, 10 (13%) were found infected with Leishmania spp. In seven dogs and two humans, the infecting species was typed as Leishmania (Leishmania) infantum. The same genotype was detected in the human and two of the CanL. Although several diagnostic methods displayed weak or moderate agreement, the concordance values for serology versus maxicircle PCR were very good (Kappa index = 0.84). Sandflies captured in the area were identified as Lutzomyia migonei and Lu. cortelezzii/Lu. sallesi (cortelezzii complex). The focal appearance of leishmaniasis in dogs and humans in a sylvatic region and its relatively low prevalence of infection suggests that L. (L.) infantum transmission to dogs and humans may, in this region, stem from sylvatic reservoirs.

Biological Control of the Chagas Disease Vector Triatoma infestans with the Entomopathogenic Fungus Beauveria bassiana Combined with an Aggregation Cue: Field, Laboratory and Mathematical Modeling Assessment.

BACKGROUND: Current Chagas disease vector control strategies, based on chemical insecticide spraying, are growingly threatened by the emergence of pyrethroid-resistant Triatoma infestans populations in the Gran Chaco region of South America. METHODOLOGY AND FINDINGS: We have already shown that the entomopathogenic fungus Beauveria bassiana has the ability to breach the insect cuticle and is effective both against pyrethroid-susceptible and pyrethroid-resistant T. infestans, in laboratory as well as field assays. It is also known that T. infestans cuticle lipids play a major role as contact aggregation pheromones. We estimated the effectiveness of pheromone-based infection boxes containing B. bassiana spores to kill indoor bugs, and its effect on the vector population dynamics. Laboratory assays were performed to estimate the effect of fungal infection on female reproductive parameters. The effect of insect exuviae as an aggregation signal in the performance of the infection boxes was estimated both in the laboratory and in the field. We developed a stage-specific matrix model of T. infestans to describe the fungal infection effects on insect population dynamics, and to analyze the performance of the biopesticide device in vector biological control. CONCLUSIONS: The pheromone-containing infective box is a promising new tool against indoor populations of this Chagas disease vector, with the number of boxes per house being the main driver of the reduction of the total domestic bug population. This ecologically safe approach is the first proven alternative to chemical insecticides in the control of T. infestans. The advantageous reduction in vector population by delayed-action fungal biopesticides in a contained environment is here shown supported by mathematical modeling.

[Efficacy of Fipronil in the control of the peridomiciliary cycle of Triatoma infestans in an area resistant to Deltamethrin]. / Eficacia del Fipronil en el control del ciclo peridomiciliario de Triatoma infestans en un área con resistencia a la Deltametrina.

This study tested the efficacy of liquid Fipronil (1.0%) against Triatoma infestans, administered by pouring on birds and mammals both in laboratory and field conditions. In the laboratory a chicken, dog, and goat were treated with Fipronil, after which deltamethrin-resistant stage III T. infestans nymphs were fed on them. The control group used same-stage nymphs reared in laboratory. During the field phase, Fipronil was used to treat 4 dogs, 1 cat, and 2 broody hens. Intradomiciliary infestation was treated using aerothermics. In laboratory, nymphal mortality was 100.0% after 7 days and 88.8% after 30 days. In the field, there was a 65.4% decrease in the triatomine density rate after 30 days.

Eficacia del Fipronil en el control del ciclo peridomiciliario de Triatoma infestans en un área con resistencia a la Deltametrina / Efficacy of Fipronil in the control of the peridomiciliary cycle of Triatoma infestans in an area resistant to Deltamethrin

Se investigó la eficacia del Fipronil líquido al 1,0 por ciento contra T. infestans, administrado pour on en aves y mamíferos, tanto en condiciones de laboratorio como en el terreno. En laboratorio se trataron con Fipronil una gallina, un perro y un caprino y se alimentaron sobre ellos ninfas III resistentes a Deltametrina. Como grupo control se utilizaron ninfas del mismo estadio criadas en laboratorio. Durante la fase de terreno se impregnaron con Fipronil 4 perros, 1 gato y 2 gallinas cluecas. La infestación intradomiciliaria fue tratada mediante Aerotermia. En laboratorio la mortalidad ninfaria fue del 100,0 por ciento a los 7 días y del 88,8 por ciento a los 30 días. En terreno, la disminución del índice de Densidad Triatomínea - medida a los 30 días - fue del 65,4 por ciento.

[Air temperature elevation as an alternative for the control of deltamethrin-resistant Triatoma infestans (Hemiptera, Reduviidae)]. / La aerotermia como alternativa para el control de Triatoma infestans (Hemiptera, Reduviidae) resistentes a deltametrina.

This study explores the effects of artificial air temperature elevation on the embryonic, nymphal, and adult forms of deltamethrin-resistant Triatoma infestans. In the laboratory, complete offspring of T. infestans were exposed to increasing air temperatures to determine the viability of eggs and survival of nymphs and adults; in the field, the experiment was conducted in a poor rural dwelling previously identified as infested with the vector. The laboratory phase showed 100% non-viability of eggs and 100% mortality of nymphs and adults exposed to airtight temperatures from 45 degrees C to 55 degrees C, while the field phase succeeded in reproducing the heat's ovicidal effect and negative conversion of entomological assays in the experimental dwelling, as conducted over the course of 72 hours at 30, 60, and 90 days from the baseline evaluation. Artificial elevation of airtight temperature on dwellings proved to be an acceptable, harmless, and technically simple control method.

La aerotermia como alternativa para el control de Triatoma infestans (Hemiptera, Reduviidae) resistentes a deltametrina / Air temperature elevation as an alternative for the control of deltamethrin-resistant Triatoma infestans (Hemiptera, Reduviidae)

Se exploraron los efectos de la elevación artificial de la temperatura del aire sobre las formas embrionarias, ninfales y adultas de Triatoma infestansresistentes a Deltametrina. En laboratorio, se expuso a temperaturas crecientes del aire la progenie completa de T. infestans, para determinar viabilidad de huevos y supervivencia en ninfas y adultos; sobre el terreno, la experimentación se llevó a cabo en una vivienda tipo rancho previamente evaluada como colonizada. Durante la fase de laboratorio se comprobó la inviabilidad del 100 por ciento de los huevos y la mortalidad del 100 por ciento de las ninfas y adultos expuestos a temperaturas del aire estanco de entre 45ºC y 55ºC, mientras que en la fase de terreno se logró reproducir el efecto ovicida del calor, como así también la negativización de las evaluaciones entomológicas de la vivienda de experimentación, llevadas a cabo a las 72 horas, a los 30, 60 y 90 días. La elevación artificial de la temperatura del aire estanco en las habitaciones resultó ser un método de control de eficacia aceptable, inocuo y técnicamente sencillo.