Infrared video tracking of Anopheles gambiae at insecticide-treated bed nets reveals rapid decisive impact after brief localised net contact

Long-lasting insecticidal bed nets (LLINs) protect humans from malaria transmission and are fundamental to malaria control worldwide, but little is known of how mosquitoes interact with nets. Elucidating LLIN mode of action is essential to maintain or improve efficacy, an urgent need as emerging insecticide resistance threatens their future. Tracking multiple free-flying Anopheles gambiae responding to human-occupied bed nets in a novel large-scale system, we characterised key behaviours and events. Four behavioural modes with different levels of net contact were defined: swooping, visiting, bouncing and resting. Approximately 75% of all activity occurred at the bed net roof where multiple brief contacts were focussed above the occupant’s torso. Total flight and net contact times were lower at LLINs than untreated nets but the essential character of the response was unaltered. LLINs did not repel mosquitoes but impacted rapidly: LLIN contact of less than 1 minute per mosquito during the first ten minutes reduced subsequent activity; after thirty minutes, activity at LLINs was negligible. Velocity measurements showed that mosquitoes detected nets, including unbaited untreated nets, prior to contact. This is the most complete characterisation of mosquito-LLIN interactions to date, and reveals many aspects of LLIN mode of action, important for developing the next generation of LLINs

Host-seeking activity of a Tanzanian population of Anopheles arabiensis at an insecticide treated bed net

Background: Understanding how mosquitoes respond to long lasting insecticide treated nets (LLINs) is fundamental to sustaining the effectiveness of this essential control tool. We report on studies with a tracking system to investigate behaviour of wild anophelines at an LLIN, in an experimental hut at a rural site in Mwanza, Tanzania. Methods: Groups of adult female mosquitoes (n = 10 per replicate) reared from larvae of a local population, identified as predominantly (95%) Anopheles arabiensis, were released in the hut. An infrared video tracking system recorded flight and net contact activity over 1 h as the mosquitoes attempted to reach a supine human volunteer within a bed net (either a deltamethrin-treated LLIN or an untreated control net). A range of activities, including flight path, position in relation to the bed net and duration of net contact, were quantified and compared between treatments. Results: The total time that female An. arabiensis spent in flight around LLINs was significantly lower than at untreated nets [F(1,10) = 9.26, p = 0.012], primarily due to a substantial reduction in the time mosquitoes spent in persistent ‘bouncing’ flight [F(1,10) = 18.48, p = 0.002]. Most activity occurred at the net roof but significantly less so with LLINs (56.8% of total) than untreated nets [85.0%; Χ2 (15) = 234.69, p < 0.001]. Activity levels at the bed net directly above the host torso were significantly higher with untreated nets (74.2%) than LLINs [38.4%; Χ2 (15) = 33.54, p = 0.004]. ‘Visiting’ and ‘bouncing’ rates were highest above the volunteer’s chest in untreated nets (39.9 and 50.4%, respectively) and LLINs [29.9 and 42.4%; Χ2 (13) = 89.91, p < 0.001; Χ2 (9) = 45.73, p < 0.001]. Highest resting rates were above the torso in untreated nets [77%; Χ2 (9) = 63.12, p < 0.001], but in LLINs only 33.2% of resting occurred here [Χ2 (9) = 27.59, p = 0.001], with resting times spread between the short vertical side of the net adjacent to the volunteer’s head (21.8%) and feet (16.2%). Duration of net contact by a single mosquito was estimated at 204–290 s on untreated nets and 46–82 s on LLINs. While latency to net contact was similar in both treatments, the reduction in activity over 60 min was significantly more rapid for LLINs [F(1,10) = 6.81, p = 0.026], reiterating an ‘attract and kill’ rather than a repellent mode of action. Conclusions: The study has demonstrated the potential for detailed investigations of behaviour of wild mosquito populations under field conditions. The results validate the findings of earlier laboratory studies on mosquito activity at LLINs, and reinforce the key role of multiple brief contacts at the net roof as the critical LLIN mode of action

Evaluación de los niveles séricos de vitamina D en pacientes infectados con covid 19 en un hospital de Colombia

Introduction: The disease caused by covid 19 is a pathology that affects not only the respiratory system, but also leads to multi-organ failure. Until the current date this manuscript is written, there is no effective treatment to counteract it, prevention is the only way to reduce the number of infected and deaths resulting from it. Materials and methods: A total of 160 medical records of patients with COVID-19 from a hospital in Colombia were selected and retrospectively analyzed. Data collection was carried out in the period between 04/09/2020 and 04/09/2021. Conclusions: It was possible to conclude that low serum vitamin D levels were significantly associated with a higher risk of acquiring a covid 19 infection and developing a more severe course of the disease, which can even lead to death. Therefore, vitamin D supplementation would provide serum levels of vitamin D so that infection can be prevented or the severity of covid 19 minimized.Introducción: La enfermedad originada por el covid 19 es una patologia que afecta no solo al sistema respiratorio, sino que también conduce a falla multiorgánica. Hasta la fecha actual en que se redacta este manuscrito, no existe ningun tratamiento eficaz para contrarrestarla, la prevención es la única forma de reducir el número de infectados y muertes producto de esta. Materiales y métodos: Se seleccionaron y analizaron retrospectivamente un total de 160 historias clínicas de pacientes con COVID-19 de un hospital de Colombia. La recolección de datos se llevó a cabo en el período comprendido entre el 09/4/2020 y el 09/04/2021. Conclusiones: Se pudo llegar a la conclusion que los niveles bajos de vitamina D en suero se asociaron significativamente con un mayor riesgo de adquirir una infección por covid 19 y desarrollar un curso mas grave de la enfermedad, que puede conducir incluso a la muerte. Por lo cual la suplementación con vitamina D proporcionaria niveles sericos de vitamina D para que se pueda prevenir la infección o minimizar la gravedad del covid 19