The effect of domestic detergents on the population dynamics of the immature stages of two competitor mosquitoes, Culex cinereus Theobald and Culex quinquefasciatus Say (Diptera, Culicidae) in Kenya.

In some rural areas of Kenya pit latrines are the most important breeding places of Culex quinquefasciatus, but this vector is often rapidly displaced by a competitor, Culex cinereus, which then breeds prolifically in the latrines. In urban settlements, however, cesspools are the main breeding sites of C. quinquefasciatus and no such species replacement occurs. These latter habitats contain water contaminated with domestic detergents. When detergents were introduced into a pit latrine colonized only by C. cinereus this mosquito was eliminated after about 3 weeks. When both species were reared in water containing detergents C. cinereus had lower pupal yields than C. quinquefasciatus. In two pit latrines where C. cinereus normally displaced C. quinquefasciatus, the addition of detergent prevented this, and after their coexistence for a few weeks, C. cinereus eventually disappeared. These observations suggest that during the last few decades domestic detergents, together with other pollutants such as insecticides, may have contributed to the elimination of competitors, such as C. cinereus, from C. quinquefasciatus breeding sites.

Biting activity and resting behaviour of Anopheles merus Donitz (Diptera: Culicidae) on the Kenya Coast.

Behavioural studies on An. merus were conducted during a period of 11 months in Jimbo, a village on the Kenya Coast. The biting activity of An. merus both outdoors and indoors attained a peak between 24.00 and 01.00 hours. The mosquito showed a stronger tendency to bite outdoors than indoors and was markedly exophilic. Various outdoor resting sites were also identified.

The regulation of preimaginal populations of Aedes aegypti (L.) (Diptera: Culicidae) on the Kenya coast. II. Food as a main regulatory factor.

Experiments were carried out in a village on the Kenya coast to investigate observed differences in pupal productivity of Aedes aegypti breeding in indoor pots. Daily addition of maize gruel, the staple food of villagers, to pots of high and low mosquito production promoted an increase of pupal numbers, although daily introduction of first-instar larvae did not significantly affect pupal production. Differences in pupal productivity were not related to differences in the numbers of eggs laid in the pots. Predation and overcrowding did not seem important in regulating the preimaginal stages. It was concluded that food, especially maize gruel accidentally introduced into the pots by villagers, was the key factor which regulated population size. As numbers of eggs are always considerable, genetic control of Ae. aegypti can be successful only when it reduces egg hatchability to a very low level. The prospects of controlling Ae. aegypti by means of health education and/or environmental management are discussed.

The regulation of preimaginal populations of Aedes aegypti L. (Diptera: Culicidae) on the Kenya coast. I. Preimaginal population dynamics and the role of human behaviour.

On the Kenya coast Aedes aegypti breeds in pots maintained indoors for water storage. Pupal numbers vary greatly from one pot to another. The rhythm of water replenishment and the accidental introduction of food into the pots regulate pupal numbers. When water replenishment occurs more often than once per week, pupal numbers are small. When replenishment occurs less often, both low and high pupal numbers may be observed. The presence or absence of larval food distinguishes pots of high versus low productivity. A hypothesis is put forward that the introduction of food into the pots could be the result of human activity especially of young children when getting water for their meals.

The distribution and frequency of Culex pipiens quinquefasciatus Say 1823 (Diptera, Culicidae) breeding places on the Kenya Coast in relation to human sociological factors.

In rural settlements of the Kenya Coast C. p. quinquefasciatus develops in three major types of breeding-places. These are pit latrines, cesspools and small cement cisterns which man builds to improve his sanitary facilities. All three types are present in Moslem villages. At present only latrines have been recorded in non-Moslem villages. Building of such facilities is an established practice in Moslem villages while it is recent in non-Moslem ones. The proportion of houses with potential breeding-places is increasing with the standard of living of the inhabitants and with the size of the settlements. Since the building of sanitary facilities will probably increase in the future the mosquito breeding situation will tend to worsen accordingly. Thus there is an urgent need to curb such breeding by developing low cost technology which can easily be implemented.

[Ecology of Culex pipiens fatigans larvae in an area of high endemicity of Bancroftian filariasis (author's transl)]. / Ecologie larvaire de culex pipiens fatigans Wiedemann, 1828 (Diptera, Culcidae) dans une zone de haute endemie filarienne (Mayotte, archipel des comores)

Culex pipiens fatigans in the main vector of bancroftian filariasis in the Mayotte island (Comores) where it imposes an important health problem. The breeding-sites of C. p. fatigans are either man-made (latrines, cesspools, various containers), or natural (polluted water of estuaries of some rivers). The man-made breeding-sites are not similarly distributed in the different localities of the island. Their distribution varies according to the customs of the inhabitants, size and site of the community. They are mainly represented by latrines, where Anjouan ethnic group is predominent; by cesspools in localities inhabited by Sakalava (a Malagasian ethnic group) and by other latrines and cesspools in mahoraises (inhabitants of Mayotte) and cosmopolitan localities. In rural areas, the percentage of habitations with cesspools usually increases with the size of the villages. The various breeding-sites are primarily productive when they are built on a ground with poor permeability. The importance of the present information is further discussed with relation to the population dynamics of C.p. fatigans and to the measures which may be useful for a control program of this mosquito.