Mosquito borne diseases in England : past, present and future risks, with special reference to malaria in the Kent Marshes
Malaria was once common in the marshes of southern England. In this study I investigated why a disease called benign tertian malaria became known as the killer of the marshes and looked at the present and future threat from malaria returning to these marshes. The main focus of research was carried out on the Isle of Sheppey, one of the last places in England to experience an epidemic of malaria. An historical analysis of malaria was carried out by analysing births and deaths using Parish and Hospital records. Here I make the case that the deaths associated with malaria were more likely to be caused by diarrhoeal diseases and acute respiratory infections. The present risk of malaria was assessed using several methods. Field surveys showed that populations of An. atroparvus on Sheppey were small and severely limited by the few over-wintering sites and the filamentous surface algae needed for the aquatic stages to develop. Local residents found mosquitoes a major nuisance during the summer months, but few of these were likely to be malaria vectors. Overall the risk of local malaria transmission is extremely low and far below that needed to maintain the disease. Searches of 52 aircraft arriving at Gatwick Airport from Africa revealed no malaria vectors suggesting that the risk of importing exotic mosquitoes by aircraft is remote. Finally, 1 developed a simple surveillance system that could be used for assessing the threat of future vector borne diseases, using West Nile virus as a model. Routine sampling with Mosquito Magnet traps, a carbon-dioxide baited trap, was extremely efficient at collecting large numbers of potential disease vectors and could be used as a tool for risk assessment programmes. These studies indicate that malaria is extremely unlikely to ever return to the United Kingdom.