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Dengue virus, transmitted mainly by Aedes aegypti mosquitoes, is a significant public health challenge in tropical and subtropical countries, with an incidence that is growing at an alarming rate. The release of Wolbachia-carrying mosquitoes has been suggested as a strategy to reduce the incidence of multiple arboviruses. In Medellín, Colombia, large-scale releases of Wolbachia-infected Ae. aegypti mosquitoes were performed between 2017 and 2022 by the World Mosquito Program to facilitate population replacement. In this study, we evaluated the prevalence and distribution of Wolbachia-infected Ae. aegypti two years after completion of these releases. We conducted the sampling across 19 communes in Medellín, using 416 ovitraps to collect Ae. aegypti eggs from epidemiological weeks 26 to 41 in 2023. Upon hatching the collected eggs, we identified and pooled adult female Ae. aegypti for DNA extraction. Subsequently, we conducted PCR assays for the detection of Wolbachia infection in these mosquitoes. We used maximum likelihood estimation (MLE) and Bayesian methods to estimate the prevalence of Wolbachia infection, while using QGIS to analyze spatial distribution of infection in the region. A total of 774 female Ae. aegypti mosquitoes from 182 pools were evaluated. We detected Wolbachia in 33.5 % of pools, with an estimated individual minimum infection rate of 9.5 % and a maximum of 33.2 %. The prevalence varied significantly across communes, with the highest rates observed in the northeastern and southwestern areas. Spatial analysis revealed a highly heterogeneous island-like distribution of Wolbachia across Medellín with a few hotspots. The observed Wolbachia prevalence in this work was lower than previously reported. We suspect a decline in the prevalence of Wolbachia-infected Ae. aegypti mosquitoes in Medellín following the completion of their release., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Objective: Determining Brucella canis prevalence in domestic dogs (pets) from 11 districts in Medellín. A survey of risk factors was also carried out., Materials and Methods: Immunoassay was used for analysing 441 dog serum samples and several risk factors regarding their owners and some related to the immediate environment were established., Results: Brucellosis prevalence was 2.76 % (1.11-4.42 95 %CI), being highest in the Buenos Aires (6.9 %) and Villa Hermosa districts (5.7%). Seroprevalence was higher in male dogs (4.6 %),mongrels (4.8 %),dogs less than one year old (3.7 %), in homes having nearby water sources (4.5 %) and in dogs living with their owners for more than five months (3.1 %).The dogs' breed was associated with antibody presence (p<0.05). Seroprevalence became increased to 7.5 % when the home was shared with other pets. Higher prevalence was found when the dogs lived in homes without drinking water (6.7 %) and homes lacking a fixed water supply or sewerage connection (7.7 %). No association was found for any of the aforementioned variables with the presence of antibodies., Conclusion: Apart from cases involving occupational risk, the risk of Brucella canis transmission to humans in domestic settings may increase if the aforementioned risk factors continue increasing in urban areas, such as those explored in this study.