To investigate the impact of insecticide impregnated curtains (IIC) on child mortality over the period 3 to 5 years following their introduction.
a) determining whether, after an initial reduction in child mortality following the introduction of IIC, there is a subsequent increase in child mortality ("delayed" mortality) in the age range 6-59 months;
b) documenting changes over the medium term in the ability of children's immune systems to inhibit the invasion of red blood cells by malaria parasites;
c) documenting changes in the prevalence of malaria episodes and in the profile of parasitological parameters of malaria infection in children aged 6-59 months living in villages protected by IIC;
d) documenting changes in the intensity of transmission, in the biting/resting behaviour of malaria vectors, in their susceptibility to permethrin and in the genetic composition of the population following the introduction of IIC;
e) training one Burkinabe graduate to the level of MSc (epidemiology/statistics), one to PhD level in entomology, one to PhD level in immunology, and one to MSc level in molecular biology.
The proposed study will maintain the intervention in two groups (yearly re-impregnation of curtains and replacement of damaged curtains) and the collection of mortality data for an additional three years (up to June 1999). It is expected that the opportunity of investing in impregnated materials for controlling malaria in high transmission settings will be evaluated on the basis of the results. In addition, the relationship between transmission, immunity and disease will be clarified.
Child mortality. The primary outcome measure in this study will be all-cause child mortality. This variable will be measured by yearly re-census.
Complementary activities concern:
Children's immune status. As no marker of protective immunity has been identified thus far, we shall measure in vitro the ability of children's sera to inhibit parasite invasion of erythrocytes in combination with a monocyte cell line.
Child morbidity. Cross-sectional surveys in 48 villages (24 in each group) will be conducted in September 1996, 1997 and 1998 (September is the month of peak transmission).
Assessment of transmission. Transmission throughout the study area will be assessed by cross-sectional, outdoor CDC light trap catches. The genetic composition of the vector population will be compared between villages of Group A and B and villages outside the study area. The duration of malaria transmission will be assessed longitudinally from June to December. The residual vector population and its biting behaviour will be determined by outdoor CDC light trap catches. Antibodies to the circumsporozoite protein (CS) of Plasmodium falciparum will provide an indication of intensity of transmission.
Monitoring coverage and utilisation. Re-impregnation and installation rates are recorded yearly at the time of re-impregnation. Coverage will be further assessed by visits to a 10% random sample of dwellings. Utilisation will be assessed by pyrethrum spray catches and by surprise visits.
Assessment of insecticide susceptibility. Mosquito susceptibility to permethrin will be assessed once yearly, by the standard WHO method on impregnated paper.
Funding SchemeCSC - Cost-sharing contracts