The variation of culex quinquefasciatus population density as an index of pollution in urban, peri-urban and rural locations

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A seven-month study of the variation of Culex quinquefasciatus population density was undertaken in three locations (i.e. an urban, pen-urban and rural) to establish that the population density of Culex quinquefasciatus could be used as an index of organic pollution. Weekly sampling of the larvae as well as two nights per month catches of the adult mosquitoes using human baits was carried out. At the end of the period, it was observed that in all the three locations, Culex. quinquefasciatus preferred organically polluted water for oviposition . The population density increased with the level of organic pollution. The more polluted sites containing human excreta had the highest densities. The result also showed that water quality is a determining factor of the type of mosquito species that would breed in a particular breeding site. It was further concluded that Culex is an urban mosquito, since the population densities obtained in the urban location for both the larvae and the adults were significantly (P <0.05) higher than those of the pen-urban and rural locations. Similarly, An. gambiae was identified to be a rural mosquito. The biting activities of Culex quinquefasciatus was more concentrated between 8.00pm and 12 midnight with the peak at 11.30pm, while that of Anopheles gambiae was between 11 .30pm and 5.00am, with peak at 1 .30am. The distribution of rainfall rather than the amount is an important determinant of the distribution of the population density of mosquitoes.
A thesis submitted to the Department of Biological Science, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirement for the award of Master of Science in Environmental Science, 2001