Oviposición diaria de Aedes aegypti en Orán, Salta, Argentina / Daily oviposition activity of Aedes aegypti in Orán, Argentina / Oviposição diária de Aedes aegypti em Orán, Salta (Argentina)

El objetivo del estudio fue determinar los horarios de máxima actividad de oviposición de Aedes aegypti en la ciudad de Orán (noroeste argentino). Se realizaron muestreos quincenales entre noviembre de 2006 y febrero de 2007 (primavera-verano). La ciudad fue dividida en tres zonas (norte, centro, sur), donde fueron seleccionadas al azar las viviendas para colocar dos ovitrampas en el exterior de las mismas. Las ovitrampas fueron reemplazadas cada cuatro horas, desde la mañana (8h) hasta el atardecer (20h). Se registró la mayor cantidad de huevos entre las 16 y 20 h (81 por ciento). Estos datos aportan al conocimiento del vector y, por lo tanto, de la posibilidad de control, pudiendo realizarse las fumigaciones en la franja horaria con mayor actividad de oviposición.

The study aimed to determinate the maximum daily peak of Aedes aegypti oviposition in the city of Oran, northwestern Argentina. Biweekly samplings were taken between November 2006 and February 2007 (spring-summer). The city was divided into three areas (north, center, and south) and households were randomly selected. Two ovitraps were placed outdoors in the selected houses. Ovitraps were replaced every four hours, from morning (8 a.m.) to late afternoon (8 p.m.). The largest number of eggs was recorded between 4 p.m. and 8 p.m. (81 percent). These findings enhance our understanding of the vector and thus its control such as spraying during the hours of peak oviposition activity.

O objetivo do estudo foi determinar os horários de máxima atividade de oviposição de Aedes aegypti na cidade de Orán (noroeste argentino). Foram realizadas coletas quinzenais, entre novembro de 2006 e fevereiro de 2007 (primavera-verão). A cidade foi dividida em três zonas (norte, centro, sul); foram escolhidos aleatoriamente dez domicílios em cada zona e duas ovitrampas foram instaladas no exterior de cada domicílio. As ovitrampas eram trocadas a cada quatro horas, cobrindo desde a manhã (8h) até a noite (20h). A maior quantidade de ovos (81 por cento) foi registrada entre as 16h e 20h. Esses dados aportam conhecimento do vetor e, portanto, a seu controle, como, por exemplo, realizar a fumegação na faixa horária de maior atividade de oviposição.

Enfermedad de Chagas experimental: I estudio de diferentes condiciones de inmunización sobre el curso de la infección / Experimental Chagas disease: I study of different immunization conditions over the infection course

In previous works it has been demonstrated that Balb/c albino mice immunized with Trypanosoma rangeli developed cellular and humoral immune response to Tripanosoma cruzi. Moreover, the immunized animals were protected against lethal infection by virulent T. cruzi trypomastigotes. In fact, immunized mice had significantly lower parasitemias and longer survival than controls. To go further in this experimental model, the aim of the present work was to analyze the effect of the number of antigenic stimuli and the conservation of the antigen on the effectiveness of protective effect. For that purpose, three different immunization schedules injecting T. rangeli epimastigotes fixed with glutaraldehide and emulsified with Saponin (SAP) as adjuvant were assayed. Different lots of mice which received only phosphate buffer saline or SAP were used as controls. In another set of experiments the conservation of the antigen during 90 days at 4ºC was studied. In all the experiments mice were infected with 100 trypomastigotes of T. cruzi, Tulahuén strain. The parasitemias were analyzed on 13th, 16th and 21th post infection days, and the survival until the 60th day. The results revealed that one dose of antigen was inadequate to give an effective protection. On the other hand, mice immunized with 2 and 3 ddose showed a significant decrease of parasitemia with regard to controls (p<0.001- p<0.0001) and the survival were markedly increased. Likewise, the antigen kept during 90th days at 4ºC showed similar protective efficacy than fresh antigen. Both of these experimental groups showed significant differences with respect to control animals in parasitemia (p<0.05 - p>0.01) and survival (p>0.01). In conclusion, the results of this work showed that in the experimental conditions assayed, the immunization with T. rangeli trigger and adequate immune response when mice received at least two antigenic stimuli. Likewise, it is interesting to point out the stability of the antigenic preparation during at least 90th days