Citric Acid and Sodium Bicarbonate as an Alternative Carbon Dioxide Source for Mosquito Surveillance

Most mosquito surveillance programs rely on traps baited with carbon dioxide (CO₂) to attract host-seeking mosquitoes. The source of CO₂, traditionally dry ice or gas cylinders, poses operational challenges, especially in remote locations. CO₂ production from citric acid and sodium bicarbonate (NaHCO₃) using low-cost intravenous fluid bags ('acid traps') was evaluated in laboratory experiments. Field trials then compared the efficacy of these acid traps with dry ice traps. Using a 2 × 2 Latin square style design, trapping locations were established at two sites in Sydney, New South Wales, Australia (one urban and another peri-urban), to assess trap performance in diverse environments. The laboratory results showed CO₂ production of sufficient amount and duration for overnight mosquito capture. Whilst field experiments showed that dry ice traps captured more mosquitoes (up to 59%) than acid traps, numbers were similar in the urban environment. At both sites, species composition was similar, with <i>Culex quinquefasciatus</i>, <i>Aedes notoscriptus</i>, and <i>Aedes vigilax</i> predominantly collected, and these are known species of pest and public health concern. Further modifications to the acid traps could further improve CO₂ output and trap efficiency.