Spatial analysis of dengue transmission in an endemic city in Brazil reveals high spatial structuring on local dengue transmission dynamics.

In the last decades, dengue has become one of the most widespread mosquito-borne arboviruses in the world, with an increasing incidence in tropical and temperate regions. The mosquito Aedes aegypti is the dengue primary vector and is more abundant in highly urbanized areas. Traditional vector control methods have showing limited efficacy in sustaining mosquito population at low levels to prevent dengue virus outbreaks. Considering disease transmission is not evenly distributed in the territory, one perspective to enhance vector control efficacy relies on identifying the areas that concentrate arbovirus transmission within an endemic city, i.e., the hotspots. Herein, we used a 13-month timescale during the SARS-Cov-2 pandemic and its forced reduction in human mobility and social isolation to investigate the spatiotemporal association between dengue transmission in children and entomological indexes based on adult Ae. aegypti trapping. Dengue cases and the indexes Trap Positive Index (TPI) and Adult Density Index (ADI) varied seasonally, as expected: more than 51% of cases were notified on the first 2 months of the study, and higher infestation was observed in warmer months. The Moran's Eigenvector Maps (MEM) and Generalized Linear Models (GLM) revealed a strong large-scale spatial structuring in the positive dengue cases, with an unexpected negative correlation between dengue transmission and ADI. Overall, the global model and the purely spatial model presented a better fit to data. Our results show high spatial structure and low correlation between entomological and epidemiological data in Foz do Iguaçu dengue transmission dynamics, suggesting the role of human mobility might be overestimated and that other factors not evaluated herein could be playing a significant role in governing dengue transmission.

Optimising the surveillance of Aedes aegypti in Brazil by selecting smaller representative areas within an endemic city.

OBJECTIVES: Arboviruses, such as dengue (DENV), zika (ZIKV), and chikungunya (CHIKV), constitute a growing urban public health threat. Focusing on Aedes aegypti mosquitoes, their primary vectors, is crucial for mitigation. While traditional immature-stage mosquito surveillance has limitations, capturing adult mosquitoes through traps yields more accurate data on disease transmission. However, deploying traps presents logistical and financial challenges, demonstrating effective temporal predictions but lacking spatial accuracy. Our goal is to identify smaller representative areas within cities to enhance the early warning system for DENV outbreaks. METHODS: We created Sentinel Geographic Units (SGUs), smaller areas of 1 km2 within each stratum, larger areas, with the aim of aligning the Trap Positivity Index (TPI) and Adult Density Index (ADI) with their respective strata. We conducted a two-step evaluation of SGUs. First, we examined the equivalence of TPI and ADI between SGUs and strata from January 2017 to July 2022. Second, we assessed the ability of SGU's TPI and ADI to predict DENV outbreaks in comparison to Foz do Iguaçu's Early-Warning System, which forecasts outbreaks up to 4 weeks ahead. Spatial and temporal analyses were carried out, including data interpolation and model selection based on Akaike information criteria (AIC). RESULTS: Entomological indicators produced in small SGUs can effectively replace larger sentinel areas to access dengue outbreaks. Based on historical data, the best predictive capability is achieved 2 weeks after infestation verification. Implementing the SGU strategy with more frequent sampling can provide more precise space-time estimates and enhance dengue control. CONCLUSIONS: The implementation of SGUs offers an efficient way to monitor mosquito populations, reducing the need for extensive resources. This approach has the potential to improve dengue transmission management and enhance the public health response in endemic cities.

Stress behaviors in captive robust capuchins: Effects of humidity, visitors, management and sex.

Wild robust capuchins (Sapajus spp.) are omnivorous neotropical primates that live in relatively large groups in extensive home and daily ranges with activity budgets dominated by traveling, foraging, and object manipulation, meaning that enclosed spaces can result in significant deprivation. Space restriction, manipulation by caretakers, and the chronic presence of visitors, can disrupt the animals' welfare, altering their normal activities and inducing stress behaviors. We aimed to study the behavioral repertoire, activity budget, and frequency of stress behaviors (stereotypes and self-directed behaviors) between two captive groups of robust capuchins in a public zoo in Foz do Iguaçu, Brazil, to understand how much their behavioral homeostasis has been affected. More specifically, we assessed the effect of environmental variables (temperature, relative air humidity, number of visitors, and food management) and sex on the frequency of stress behaviors. Capuchins showed a high frequency of stress behaviors, which represented around 10% of their activity budget (though the frequencies were unevenly distributed among the individuals), and traveling was positively correlated with stereotypes. We found that high relative air humidity appears to induce more stereotypes, high numbers of visitors appear to increase self-directed and vigilance behaviors and reduce stereotypes, food management can increase both kinds of stress behaviors, and females demonstrated more frequent stress behaviors than males, but individual variation may play a role. Capuchins in the group with a greater space restriction showed more stereotypes, while those in the group with more individuals showed more self-directed behaviors. Our study shows that the stress behaviors performed by the capuchins are complex and it is difficult to determine a single cause, because many traits could be involved. Despite that, this study enlightens us to direct some approaches to help these animals to meet their ecological and social needs, mitigating their stress.