Comparative evaluation of two lures to attract female mosquitoes in an urban natural reserve during daytime.

The most widely used attractant to capture adult female mosquitoes is CO2. However, there are also baits available on the market that emit a scent resembling human skin. These baits were specifically designed to attract highly anthropophilic species such as Aedes albopictus and Aedes aegypti. In this study, we compare the effectiveness of CDC traps baited either with CO2 or with a commercial blend simulating skin odor, BG-Sweetscent, for trapping female mosquitoes during daylight hours in an urban reserve in the City of Buenos Aires. We employed a hurdle generalized linear mixed model to analyze trap capture probability and the number of mosquitoes captured per hour, considering the effects of attractant, mosquito species, and their interaction. Traps baited with CO2 captured ten mosquito species, while those baited with BG-Sweetscent captured six in overall significantly lower abundance. The odds of capturing mosquitoes were 292% higher for the CO2-baited traps than for those baited with BG-Sweetscent. No evidence of a combined effect of attractant type and species on female mosquito captures per hour was found. Results indicated that CDC traps baited with CO2 were more effective than those baited with BG-Sweetscent in capturing more mosquito species and a higher number of mosquitoes within each species, even if the species captured with CO2 exhibited a certain level of anthropophilia. This result has practical implications for mosquito surveillance and control in urban natural reserves.

Different approaches to characterize artificial breeding sites of Aedes aegypti using generalized linear mixed models.

BACKGROUND: As no globally accepted dengue vaccines or specific antiviral therapies are currently available, controlling breeding sites of Aedes aegypti is a target to prevent dengue outbreaks. The present study aimed to characterize outdoor artificial breeding sites in urban households using an exhaustive classification system. METHODS: A cross-sectional entomological survey was carried out in Colón city, Entre Ríos, Argentina, using a two-stage stratified sampling design during March and April 2014. The city was stratified given the degree of urbanization of each block, and blocks and households were randomly selected. All outdoor containers with water were inspected, and the presence of immature mosquitoes was recorded. Containers were classified according to physical, functional, and location attributes. Generalized linear mixed models were applied to take into account the aggregated nature of the data (containers in houses and houses in blocks). RESULTS: Overall, 207 houses were inspected. Out of 522 containers with water, 25% had immatures of Ae. aegypti (7336). In adjusted models, the abundance of immatures was higher in containers with increasing opening surface and volume, without roof cover, exposed to shadow, out of use or with functions related to gardening activities, household chores, water storage, or construction. At block level, immatures abundance was positively associated with the degree of urbanization. CONCLUSIONS: We detected high immatures abundance in containers associated with water utilization. This suggests that containers involved in these activities, whether directly (e.g., water storage) or indirectly (e.g., incomplete water drainage in the last use), are susceptible to present a high immature abundance. Although our results indicate the importance of the type of use over the type of container, we encourage the use of both classification criteria for artificial breeding sites of mosquitoes, mainly because these are complementary. Additionally, generalized linear mixed models allowed us to analyse predictor variables at different scales (container/house/block) and consider the lack of independence between observations. An exhaustive analysis of artificial breeding sites that use this analytical methodology can lead to new information that could help designing more appropriate tools for dengue surveillance and control.

Effect of different thermal conditions on the pre-imaginal biology of Culex apicinus (Philippi, 1865) (Diptera: Culicidae).

The time of development and survival of the pre-imaginal period and the adult body size of Culex apicinus were analyzed in individuals reared from the 1st instar larva to adult emergence under laboratory and field conditions. In the laboratory, insects were exposed to three constant temperatures (15, 20, and 25 degrees C) and a photoperiod of 14:10 (L:D). In the field, temperature and photoperiod were not manipulated; during the study period water temperature ranged between 15.5 and 24.2 degrees C, and photoperiod changed from 13:11 to 14:10 (L:D). Survival to the imaginal stage at 15 degrees C (85.4%) and in the field (88.8%) was higher than that at 20 degrees C (45.8%) and 25 degrees C (8.3%). Based on femur and wing length measurements, the mosquitoes reared under field conditions (mean water temperature = 20.5 degrees C) were smaller than those laboratory-reared, even when the time of development in the field (29.5 - 36 days) was longer than that observed at 15 degrees C (24 days), 20 degrees C (15 days), and 25 degrees C (11 days). Male emergence was earlier than that of females (protandry) only in the field. Although laboratory conditions included a photoperiod and temperature range comparable with the observed values in the field, the disagreements between field and laboratory results suggest that the characteristics examined in this work could be affected by the joint variation of several factors not controlled in field conditions, such as photoperiod, temperature regime, and/or food quality of larval habitat.

Foraging activity of commensal Mus musculus in semi-captivity conditions. Effect of predator odours, previous experience and moonlight.

BACKGROUND: Mus musculus is a pest in urban and rural habitats where it consumes and contaminates food and may transmit diseases to human and domestic animals. Its control by anticoagulants is partially effective because of aversive behaviours and resistance. In this context, we wanted to assess the potential of the use of predator odours as repellents in experimental feeding trials using urine and faeces of domestic cats and faeces of geoffroyi cat, a wild small felid that is one of the main rodent predators in the study area. We also assessed the effect of previous experience and moonlight on foraging activity. RESULTS: We did not find an aversive response to cat odours in Mus musculus individuals. There was a trend to consume food in the same feeding stations over time, and the visit rate was lower in periods with high moonlight than in periods with low moonlight. CONCLUSIONS: Predator odours did not seem to be useful as rodent repellents, but maintaining illumination may lower rodent foraging activity. As rodents maintain their feeding sites over time, toxic baits may be more efficiently placed at sites previously known to be used by rodents.