Community based studies on childhood mortality in a malaria holoendemic area on the Tanzanian coast

Demographic surveillance of children under 5 years of age was undertaken over a 2 year period in a rural area of coastal Tanzania where holoendemic malaria conditions exist. The mean annual entomological innoculation rate (EIR) during the period under study was 234 infective bites per person. There were 192 deaths in children and 1130 live births during the 2 years. Of these, 148 were infant deaths giving an infant mortality rate of 131/1000 live births (95% CI 101, 154). There were 44 deaths in children 1-4 years of age and the overall child mortality rate was 10/1000 (95% CI 6.1, 14.3). Using verbal autopsy questionnaires, 56% of the deaths under 4 years were tentatively attributed to malaria.

Changes in weight gain and anaemia attributable to malaria in Tanzanian children living under holoendemic conditions

We investigated the effect of Plasmodium falciparum malaria on weight gain and haematocrit in Tanzanian children aged 6-40 months following a malaria control scheme which combined insecticide-impregnated bed nets with chloroquine chemotherapy on demand. Data from 7 villages (3 intervention and 4 control) were collected before, and one year after, the implementation of the programme. Initially, 82% of the children were parasitaemic, 78% were anaemic (i.e., packed cell volume < 33%) and 38% were underweight (i.e., 2 standard deviations below their weight-for-age Z score). One year after implementation of the programme, children not protected by the bed nets grew 286 g less (95% confidence interval [CI] 171-402 g) in a 5 months period and were twice as likely to be anaemic (95% CI 1.4-2.7) than were children not using impregnated bed nets. Our results indicated that, under holoendemic conditions, P. falciparum infection has a marked effect on both weight gain and anaemia.

Changes in malaria associated morbidity in children using insecticide treated mosquito nets in the Bagamoyo district of coastal Tanzania

A community based malaria control intervention using insecticide treated mosquito nets (IMN) has been implemented and tested in 13 villages of the Yombo Division, Bagamoyo District in the Coastal Region, Tanzania, an area holoendemic for P. falciparum malaria. Following extensive sociological research into local perceptions of malaria, the programme was implemented. It wa decided by consensus that village mosquito net committees would be the appropriate local level implementors. These were formed and provided with IMN's which were sold to villagers at subsidised cost. The income was invested for use by the committees for sustaining the activity. Use patterns were determined and high coverages were obtained among the community, particularly after promotions e.g. plays, school meetings etc. Malaria morbidity was measured among children 6-40 months of age in 7 index villages prior to the intervention in 1992 and in a comparison study between 3 villages using nets and 4 villages not using nets in 1993. Examination of the 7 cohorts of children was done from June to October each year covering the period of most severe transmission. The children using nets showed marked improvement in several malariometric indices. Following an initial clearance of parasitaemia with sulphadoxine/pyrimethamine, when compared with unprotected children, those with nets were slower to become re-infected (Relative Risk 0.45), had lower parasitaemias and showed marked improvement in anaemia (RR 0.47). Use of IMN's produced a 54% reduction in the prevalence of anaemia among young children. Attempts are being made to ensure that the programme is locally sustained.

Anaemia and Plasmodium falciparum infections among young children in an holoendemic area, Bagamoyo, Tanzania

Although the aetiology of anaemia in tropical areas is multifactorial, Plasmodium falciparum malaria is commonly associated with anaemia in children living in holoendemic malaria areas. Such an association was examined in a population based study of 338 children 6 to 40 months of age living in the Bagamoyo area of Tanzania. Stepwise regression analysis showed that fever and parasitaemia were effective in predicting anaemia and that the anaemic condition was age dependent. The majority of the children were iron deficient, followed by normochromic macrocytic anaemias. There was strong evidence in this age group that the anaemia was associated with malaria and not geohelminth infection. The importance of malaria and anaemia as a cause of childhood morbidity in Africa is discussed. This condition has taken on new significance with the realization that blood transfusions commonly used to treat severe anaemia are a major vehicle for Human Immunodeficiency Virus (HIV) transmission.

Seasonal variation in the perceived risk of malaria: implications for the promotion of insecticide-impregnated bed nets

Bed nets (mosquito nets), impregnated every 6 months with pyrethroid insecticides, are a simple, low-cost malaria control method well suited to conditions in sub-Saharan Africa. As large seasonal variations in levels of net usage may seriously limit the potential impact of the nets on malaria transmission, a study was conducted on local definitions of seasons, perceptions of seasonal variation in mosquito populations and incidence of febrile illnesses in Bagamoyo District, Tanzania, to aid in the design of a communication strategy for promoting sustained use of the nets. Both the diagnosis and treatment of febrile illnesses are affected by what season people think it is, by what illnesses they think are common in each season, and also by their perceptions of how abundant mosquitoes are. During dry seasons when mosquitoes are scarce and malaria is thought to be unlikely, it will be difficult to attain high rates of net usage. It will be necessary to develop locally-appropriate messages and communication materials that explain how it is possible that malaria can be a threat even when mosquitoes are few. Cultural consensus analysis was found to be a particularly valuable tool for understanding the reasons behind large variations in local perceptions of seasonality.

Recognition of Plasmodium falciparum asexual stage antigens by antibodies in sera from people exposed to Plasmodium vivax

An analysis of Plasmodium falciparum antigen-specific antibodies was performed on 44 serum samples from Guatemala, a region endemic for P. vivax. Most sera showed positive reactivity to P. falciparum asexual stage antigens by indirect immunofluorescent assay, enzyme-linked immunosorbent assay, and immunoprecipitation analysis using biosynthetically labeled parasites. Although several antigens were recognized by these sera, proteins with molecular weights of 195 kD, 140 kD, and in the range of 70-80 kD were strongly recognized by many of the sera studied. No such reactivity was observed for any of the surface antigens in the male and female gametes and zygotes of P. falciparum. These studies suggest that P. vivax and P. falciparum, two major human parasites, may share certain epitopes in several antigens of immunologic significance.