Spatio-temporal dynamics of dengue 2009 outbreak in Córdoba City, Argentina.

During 2009 the biggest dengue epidemic to date occurred in Argentina, affecting almost half the country. We studied the spatio-temporal dynamics of the outbreak in the second most populated city of the country, Córdoba city. Confirmed cases and the results of an Aedes aegypti monitoring during the outbreak were geolocated. The imported cases began in January, and the autochthonous in March. Thirty-three percent of the 130 confirmed cases were imported, and occurred mainly at the center of the city. The autochthonous cases were more frequent in the outskirts, specially in the NE and SE. Aedes aegypti infestation showed no difference between neighborhoods with or without autochthonous cases, neither between neighborhoods with autochthonous vs. imported cases. The neighborhoods with imported cases presented higher population densities. The majority of autochthonous cases occurred at ages between 25 and 44 years old. Cases formed a spatio-temporal cluster of up to 20 days and 12km. According to a mathematical model that estimates the required number of days needed for transmission according to daily temperature, the number of cases begun to fall when more than 15.5 days were needed. This may be a coarse estimation of mean mosquito survival in the area, provided that the study area is close to the global distribution limit of the vector, and that cases prevalence was very low.

Winter biology of Aedes albifasciatus (Diptera: Culicidae) from Córdoba, Argentina.

Host-seeking females of Aedes albifasciatus (Macquart) were collected from April to September 1997, kept under seminatural conditions, and offered sugar solution and blood. Daily survival of females ranged from 0.91 to 0.96, with blood fed females living longer than sugar fed females. Overall, 43% of engorged females completed a gonotrophic cycle, and 15% of them refed and completed a second gonotrophic cycle. The life expectancy of females emerging at the end of summer was longer than those that emerged during winter. Immature developmental time and the developmental threshold were estimated by regression. Embryo development was recorded during autumn, winter, and spring, with a duration of 5-9 d. The developmental threshold for eggs was estimated to be 2.28 degrees C. Egg mortality varied from 0.51 to 0.74. The development time for larva and pupa was between 16 and 29 d and was significantly correlated with temperature. The developmental threshold for larvae and pupae was estimated to be 4.75 degrees C. A greater proportion of females than males emerged when temperatures averaged < or = 18 degrees C. Larval and pupal mortality was high at temperatures below the developmental threshold. Aedes albifasciatus females remained gonotrophically active and immature development continued during winter in Córdoba (10 degrees C isotherm).

Relative abundance and gonotrophic status of Aedes albifasciatus (Diptera: Culicidae) during the autumn-winter period in Córdoba Province, Argentina.

Variations in the abundance of larvae and females of Aedes albifasciatus (Macquart) were monitored biweekly during the autumn-winter periods of 1996 and 1997 on the southern edge of the Mar Chiquita Lake in Córdoba Province. The degree of development of the primary ovarian follicles also was determined in host-seeking females. Abundance of the larvae and the females were noticeably different during the 2 yr of the study and matched changes in the pattern of precipitation. Although most females had ovarian follicles in Christophers stages Ib-IIa, 14% and 4% in 1996 and 1997, respectively, were in stages III-V (i.e., exhibited gonotrophic discordance). Females appeared to continue taking blood meals and laying eggs even during the autumn-winter period.

Monitoring the abundance of Aedes (Ochlerotatus) albifasciatus (Macquart 1838) (Diptera: Culicidae) to the south of Mar Chiquita Lake, central Argentina, with the aid of remote sensing.

Surges in the size of adult populations of the flood-water mosquito Aedes albifasciatus can produce important economical losses because of the way this species irritates livestock. Although this species is also the main vector of west equine encephalitis in Argentina, little is known about the factors affecting its population dynamics, as it is difficult to obtain data on its abundance over a large area. However, the results of intensive study of the mosquito in a few sites might reasonably be extrapolated to a regional scale by the use of remotely sensed data. The adult, larval and pupal stages of Ae. albifasciatus were sampled at five field sites to the south of Mar Chiquita Lake, either once a month (during the dry, cold season) or once a fortnight (during the warm, rainy season), between August 1992 and April 1993. The measured abundance of adults or pre-adults and a meteorological coefficient useful for the estimation of larval abundance each showed significant correlation with various statistics derived from normalized-difference, vegetation indices (NDVI) calculated from satellite (NOAA-AVHRR) imagery. A linear discriminant analysis, using data on NDVI, rainfall and temperature, accurately identified periods with and without pre-adults. The satellite imagery was also useful in the estimation of larval abundance and consequently could be used to predict adult abundance 7 days in advance. Even though the satellite data employed have poor spatial resolution, their high temporal resolution makes them very useful in studies of the population dynamics of mosquitoes in general, at least once the relevant variables and their relationships with mosquito breeding and survival have been identified.

New records for mosquito species (Diptera: Culicidae) in Argentina.

The geographical distributions for Aedes fluviatilis, Culex acharistus, Culex apicinus, Culex coronator, Culex dolosus, Culex quinquefasciatus, Culex saltanensis, Psorophora paulli, Psorophora varinervis, and Uranotaenia apicalis are extended. New records for 6 provinces of Argentina are given.