Monitoring community response to malaria control using insecticide-impregnated bed nets, curtains and residual spray at Nsukka, Nigeria.

A project testing the efficacy of insecticide (permethrin)-impregnated bed nets, compared with impregnated door and window curtains, residual house spraying, and a control group was implemented in 12 village clusters in the Nsukka Local Government Area of Enugu State, Nigeria, using epidemiologic and entomologic indicators. The appropriate materials and services were given free to all families. During the first year of study, three monitoring exercises were carried out in a random selection of homes where children under 5 years of age resided. Information was collected on perceived effectiveness of the interventions, condition of nets and curtains, reasons for not sleeping under nets, and recall of steps required in caring for nets and curtains. Bed nets were perceived as more effective in reducing mosquito bites compared with the two other interventions. At the last monitoring period, which occurred a few weeks before a re-impregnation exercise, respondents also perceived bed nets to be most effective in preventing malaria. These findings coincided with epidemiologic evidence. Curtains, especially those at doors, were more likely to be torn and dirty than bed nets. Although holes would not reduce the effectiveness of the insecticide, they could reduce the 'beauty' of the curtains, a perceived benefit that initially attracted villagers to both curtains and nets. Bed net owners reported significantly less frequent use of other mosquito control measures in their homes than did members of the other groups. Finally, bed net users demonstrated increased knowledge of use and care steps than did those with curtains. These findings suggested a high level of social acceptability of bed nets, and point to the need to test their acceptability further under conditions where people would pay for nets and communities would manage distribution and re-impregnation systems.

Social and behavioural baseline for guiding implementation of an efficacy trial of insecticide impregnated bed nets for malaria control at nsukka, Nigeria.

Insecticide impregnated bed nets are being tested in many tropical areas as a major tool to control malaria. In a few African countries, there is a history of local bed net production and use, while in most others, ownership of commercially-produced nets is rare due to high costs relative to local income. Such variations in pre-existing bed net use behavior must be studied prior to designing new intervention trials. A "baseline" diagnostic study in Nsukka Local Government of Enugu State, Nigeria, found that local beliefs about malaria causation, which include heat from the sun and hard work, may reduce the perceived efficacy of bed nets as an appropriate malaria control action. While the belief that mosquitos can cause malaria increased with level of formal education, the study also documented that educated people simultaneously hold both indigenous and scientific perceptions about malaria. Although the project provided bed nets, curtains and residual house spray for free, long-term sustainability may be influenced by the main constraint to current ownership of a bed net, i.e., cost. Issues, such as concern about feeling hot under the nets, a tendency to sleep outside during the hot dry season, and variations in people's ideas about what constitutes a malaria episode, point to the need to monitor the bed net intervention. This is recommended as a means of learning how people perceive the efficacy of the nets, whether they use them correctly and whether the intervention can be sustained and integrated into local primary health care programs.

First record of breeding populations of Aedes albopictus in continental Africa: implications for arboviral transmission.

Eggs of Aedes albopictus were collected in oviposition cups from 3 forested areas of Delta State in south-central Nigeria during September 1991 as part of a post-yellow fever outbreak investigation. These eggs were shipped to the Centers for Disease Control in Colorado, where they were reared to the adult stage and identified. This is the first record of breeding populations of Ae. albopictus in continental Africa. Other taxa reared from the same oviposition cups included Ae. aegypti, Ae. apicoargenteus, Ae. africanus, Ae. lilii and Ae. simpsoni subgroup. The introduction and establishment of Ae. albopictus in Africa may have important implications for transmission of indigenous arboviruses.

Epidemic yellow fever caused by an incompetent mosquito vector.

Arbovirus epidemics in a geographic region are believed to depend on the presence of susceptible or "competent" arthropod vectors. We demonstrate that an urban, Aedes aegypti-borne, epidemic of yellow fever occurred in 1987 although the mosquito vector was relatively resistant to infection and transmitted the virus inefficiently. Twenty-six percent of the experimental mosquitoes from the epidemic area that ingested yellow fever virus became infected and only 7% of these transmitted the virus. In contrast, 80% of an exotic susceptible strain of Ae. aegypti became infected and 43% were able to transmit. We also show that no other potential vectors were active during the epidemic and that the local Ae. aegypti were present in extremely large numbers. These results document, for the first time, that, in the presence of high population density an incompetent mosquito vector can initiate and maintain virus transmission resulting in an epidemic.