Olfactory basis of host location by mosquitoes and other haematophagous Diptera

The behavioural role of odours released by mosquito hosts is poorly understood, indeed for many species it is still uncertain whether olfactory cues play a significant part in host location. Generalist attractants, such as CO2, have found application in mosquito trapping systems, and yet more host-specific attractants, such as L-lactic acid, remain of questionable value. Recent work with other haematophagous Diptera, notably Glossina, has shown that by a co-ordinated multidisciplinary approach it is possible to develop odour-baited trapping systems with a high level of attractiveness and specificity. Many of the compounds shown to attract Glossina have been tested with mosquitoes, and one of these, 1-octen-3-ol, attracts female mosquitoes of a number of species, but only in the presence of CO2. The behavioural significance of other compounds identified as host attractants of haematophagous Diptera, such as phenols, indoles and carboxylic acids, are currently under investigation. Efforts to produce a host odour attractant for the highly anthropophilic species Anopheles gambiae have been hindered by the chemical nature of the compounds associated with its human host, although a number of short-chain fatty acids identified in sweat samples have been shown to be electrophysiologically active.