The impact of adverse weather events on cockroaches and flies, and the possible effects on disease.

Climate change is associated with an increase in adverse weather events such as heatwaves, drought, hurricanes and typhoons, floods and wildfires. These extreme weather events can disrupt public health infrastructure and can be detrimental to hygiene and sanitation practices, leading to knock-on effects on populations of vectors associated with disease transmission. Both the frequency and intensity of climate-related adverse weather events are predicted to increase, likely resulting in changes to vector dynamics and vector-human interactions, leading to an increased risk of disease transmission. Yet, a gap exists in our knowledge of the impact of these events on hygiene and associated pest-borne diseases. A growing body of research connects two groups of pests (domestic flies and cockroaches) that are linked with poor hygiene and sanitary conditions to mechanical disease transmission. We present a review of these specific vectors' population biology and behaviour, links with hygiene and sanitation and how pest populations and public health could be affected by adverse weather events. There is evidence that increased temperatures, extreme rainfall and flooding events are most likely to be associated with increased fly and cockroach populations and changes in the behaviour or activity of these insects, which could exacerbate the risks of disease transmission. Warmer temperatures accelerate their rates of reproduction, while heavy rainfall and flooding disrupt their habitats, driving them indoors. Other factors like habitat destruction, breakdown in healthcare system infrastructure, population displacement and altered pesticide use following an extreme weather event are predicted to influence insect populations and provide opportunities for increased human -pest contact. We highlight research gaps and provide recommendations for the improvement of current domestic and professional pest control products and strategies that might be employed to mitigate the impacts of adverse weather events on hygiene-related pests in a changing world.