A malaria control trial using insecticide-treated bed nets and targeted chemoprophylaxis in a rural area of The Gambia, west Africa. 4. Perceptions of the causes of malaria and of its treatment and prevention in the study area

Applying medical anthropology in the control of infectious disease

This paper focuses on two roles of anthropology in the control of infectious disease. The first is in identifying and describing concerns and understandings of disease, including local knowledge of cause and treatment relevant to disease control. The second is in translating these local concerns into appropriate health interventions, for example, by providing information to be incorporated in education and communication strategies for disease control. Problems arise in control programmes with competing knowledge and value systems. Anthropology's role conventionally has been in the translation of local concepts of illness and treatment, and the adaptation of biomedical knowledge to fit local aetiologies. Medical anthropology plays an important role in examining the local context of disease diagnosis, treatment and prevention, and the structural as well as conceptual barriers to improved health status. National (and international) public health goals which respect local priorities are uncommon, and generic health goals rarely coincide with specific country and community needs. The success of interventions and control programmes is moderated by local priorities and conditions, and sustainable interventions need to acknowledge and address country-specific social, economic and political circumstances.

The Gambian National Impregnated Bednet Programme: costs, consequences and net cost-effectiveness

Clinical trials have indicated that treating mosquito nets with insecticide could be a potentially cost-effective method of preventing malaria. As malaria is one of the most common causes of death in children under five in developing countries, there has been substantial interest in whether such findings can be replicated for a country's control programme in practice. The cost-effectiveness of the Gambian National Insecticide-impregnated Bednet Programme (NIBP), from the viewpoint of providers (government and non-governmental agencies) and the community, has been calculated. Information was collected from existing records, interviews with NIBP personnel, observation and household surveys. Information is provided on the resource use consequences of the NIBP in terms of reduced expenditure on anti-malaria preventive measures, treatment in government health services, household financed treatment and "charity" (burial, funeral and mourning activities), as well as cash income lost as a result of child death. The annual implementation cost of the NIBP was D757,875 (US$91,864), of which 86% was recurrent cost. The estimated number of death averted was 40.56. The net implementation cost-effectiveness ratio per death averted and discounted life years gained were D3884 (US$471) and D260 (US$31.5), respectively. Adding the cost of all mosquito nets would increase the cost-effectiveness ratios by over five times, which is an important consideration for countries with a lower coverage of mosquito nets per capita. It is concluded that insecticide-impregnated mosquito nets are one of the more efficient ways of reducing deaths in children under 10 years in rural Gambia.

Anopheles gambiae gonotrophic cycle duration, biting and exiting behaviour unaffected by permethrin-impregnated bednets in The Gambia

Permethrin-impregnated bednets protect children against malaria in The Gambia, where Anopheles gambiae complex mosquitoes are the main vectors of malaria. However, no effect has been found on mosquito density, parous rates or sporozoite rates in An.gambiae sensu lato populations; only a reduction in the numbers of mosquitoes resting indoors in rooms with treated bednets. A possible explanation for this paradox is that exposure to treated bednets leads to changed vector behaviour such as a shift in biting time, a diversion to biting outdoors instead of indoors, to biting animals instead of humans, or to increased duration of the gonotrophic cycle. To investigate these possibilities, we observed the biting and existing behaviour of An.gambiae in ten pairs of villages, in half of which the residents used permethrin-treated bednets. The possible influence of treated bednets on the gonotrophic cycle length was evaluated by mark-release-recapture experiment. No significant difference was found between villages with treated and untreated bednets in the indoor/outdoor ratio of human biting, in mean biting times or in human blood indices of An.gambiae females found resting indoors in the mornings. The proportions of unfed, fed or gravid An.gambiae females collected in exit traps, and the number of females exiting showed no significant differences between rooms with treated and untreated bednets. Indications for a gonotrophic cycle length of 2 days were found. No evidence for any change in duration of the gonotrophic cycle in relation to exposure to treated bednets was found, although the number of recaptures was low in the villages with treated bednets. Since equal numbers of infective An.gambiae were found in villages with treated or untreated bednets, and no changes in mosquito behaviour were detected, we cannot account for how children are protected against malaria by treated bednets. One possibility is that mosquitoes divert to bite other hosts, including adults.

Treatment seeking for malaria: a review of recent research

A review of literature on treatment seeking for malaria was undertaken to identify patterns of care seeking, and to assess what is known about the adequacy of the treatments used. There is considerable variation in treatment seeking patterns, with use of the official sector ranging from 10-99% and self-purchase of drugs ranging from 4-87%. The majority of malaria cases receive some type of treatment, and multiple treatments are common. The response to most episodes begins with self-treatment, and close to half of cases rely exclusively on self-treatment, usually with antimalarials. A little more than half use the official health sector or village health workers at some point, with delays averaging three or more days. Exclusive reliance on traditional methods is extremely rare, although traditional remedies are often combined with modern medicines. Although use of antimalarials is widespread, underdosing is extremely common. Further research is needed to answer the question of what proportion of true malaria cases get appropriate treatment with effective antimalarial drugs, and to identify the best strategies to improve the situation. Interventions for the private and public sector need to be developed and evaluated. More information is needed on the specific drugs used, considering resistance patterns in a particular area. In order to guide future policy development, future studies should define the nature of self-treatment, record multiple treatments and attempt to identify the proportions of all cases who begin treatment with antimalarials at standardized time intervals. Hypothetical questions were found to be of limited usefulness in estimating rates of actual treatments. Whenever possible, studies should focus on actual episodes of illness and consider supplementing retrospective surveys with prospective diary-type methods. In addition, it is important to determine the specificity of local illness terms in identifying true malaria cases and the extent to which local perceptions of severity are consistent with clinical criteria for severity and symptoms of complicated malaria.

Geographical perspectives on bednet use and malaria transmission in The Gambia, West Africa

Insecticide-impregnated bednets are now widely accepted as an important tool in reducing malaria-related deaths in children in Africa. Defining the circumstances in which net treatment programmes are likely to be effective is essential to a rational development of this control strategy. In The Gambia a National Impregnated Bednet Programme was introduced into the primary health care system in 1992. Prior to its introduction baseline epidemiological and entomological studies were conducted throughout the country. These studies showed that in areas where mosquito biting nuisance was high, people protected themselves with bednets and that where mosquito densities (and therefore bednet usage) was low malaria prevalence rates were relatively high. Since the national programme is designed to assist only those people who already own a bednet (by providing the insecticide) an understanding of the factors which determine bednet ownership is needed to help evaluate the programme's effectiveness and provide guidelines for increasing bednet usage. Village scale bednet usage rates and malaria prevalence rates obtained from the baseline survey were correlated with certain geographical variables: dominant ethnic group, area, habitat, distance from the River Gambia and distance from the 'bluffline' (the interface between the sandstone soils and alluvial soils which border the river system). In a multiple regression analysis, bednet usage was independently associated with area (P < 0.001), ethnic group (P = 0.010), habitat (P = 0.006) and distance from the river (P = 0.013). A negative association of bednet usage with malaria prevalence persisted after allowing for the other variables. Malaria prevalence was not independently associated with area, ethnic group, habitat or distance from the river. Our analysis showed that the impregnated bednet programme is likely to be most effective in villages which are sited near to or on the alluvial soils in the middle and lower river zones. These villages, which were originally settled for easy access to the river (for transport) and its swampy margins (for rice production) are within the flight distance of mosquitoes that have their breeding sites on the poorly drained alluvial soils. Variation in malaria prevalence rates (after bednet usage has been taken into account) may be related to factors such as poverty and access to health care, and/or to localized differences in the ecology of The Gambia, which determine the duration and intensity of transmission. If the National Bednet Programme is to be effective throughout The Gambia it is vital to develop promotional activities which will encourage bednet usage in areas where nuisance biting by mosquitoes is low.

Local terminology for febrile illnesses in Bagamoyo District, Tanzania and its impact on the design of a community-based malaria control programme

This paper reviews results of several ethnographic studies that have examined the issue of local terminology for malaria in Africa, then presents findings from an on-going study in Bagamoyo District, Tanzania. The study used a mixture of qualitative and quantitative interview methods to examine local perceptions of malaria and malaria treatment practices. Although the local term homa ya malaria or malaria fever appeared on the surface to correspond closely with the biomedical term malaria, significant and often subtle differences were found between the two terms. Of perhaps greatest importance, common consequences of malaria in endemic areas such as cerebral malaria in young children, severe anaemia and malaria in pregnancy were not connected with homa ya malaria by many people. A set of guidelines are described that were used to determine how best to promote acceptance and use of insecticide-impregnated mosquito nets, given these results. It is demonstrated that the position of the term used to denote malaria in the local taxonomy of febrile illnesses has important implications for the design of health education interventions.

[Motivation to acquire and use impregnated mosquito nets in a stable malaria zone in Burundi]

In Burundi, the purchase, acceptance and utilization of impregnated bed nets sold at a promotion price (2 $US) were evaluated in a stable malaria area (South-Imbo, district of Nyanza Lac) where this method of protection was previously unknown to the inhabitants. The sale of the impregnated nets differed between the administrative subdivisions (so-called 'collines') of the area with a coverage varying from 10 to 70% of families. Moreover, in one of these collines with a high overall coverage rate (62%) a difference was also found between the three administrative regions (so-called 'sous-collines') which were socially and economically similar. However, these sous-collines (SC) differed in their geographical location and were found at different altitudes. The real coverage corresponding with the percentage of families showing at least one installed bed net, was calculated for each SC. This coverage was 77% in the SC-1 situated in the low wet area and decreased gradually to 14% in the SC-3 at the highest altitude. The purchase of a bed net does not necessarily mean that people will use them. About 30% of the bed nets bought at the promotion price could not be found and most of them were resold in the neighbouring country (Tanzania). Between 7 (SC-I) and 47% (SC-3) of the bed nets were still packed and not in use. The motivation for buying and using impregnated nets appears to depend essentially on the nuisance level caused by mosquitoes, as shown by the abundance of the mosquitoes in the SC-1 situated in the low wet area (75 bites/man/night) compared to that observed in the SC-2 located at a higher altitude (i bite/man/night). The authors conclude that appropriate health education and information should be developed and promoted by health staff, local authorities and teachers in order not only to improve comfort by decreasing the insect nuisance, but also to decrease the considerable malaria burden in the community.

Traditional healers in Tanzania: the perception of malaria and its causes

The coordination of traditional and western medicine is still in its infancy in most African countries. Although there is much discussion about the contribution of traditional medicine and its practitioners, especially on the primary health care level, it has rarely be done in practice. This is probably due to the lack of knowledge of how to do it, because a serious attempt to include traditional medicine in health planning would presuppose that it is known what traditional medicine has specifically to offer for certain diseases/illnesses and how traditional healers manage such conditions. The aim of this study was to investigate the management of malaria by traditional healers in different areas in Tanzania. This included looking at the perception, the causation concepts and the knowledge about prevention of the disease/illness of malaria. For this purpose traditional healers were interviewed in different rural and urban places in Tanzania: in the Kilombero valley (Kilombero/Ulanga District), on the main island of Ukerewe (Ukerewe District), in the region near Bukoba town (Bukoba District) and in the settlement of Dar es Salaam (largest town of Tanzania). The results of the study show that most of the interviewed traditional healers were very familiar with the signs and symptoms relating to malaria, as it is defined by western medicine. Many healers were aware of different manifestations of malaria and attributed to them different local names, which match the scientific terms which describe the different types of Plasmodium falciparum malaria, such as cerebral malaria, clinical malaria or febrile type, and gastrointestinal type, respectively. Differences compared to western medical knowledge were found for concepts of causation, and in the fact that severe malaria in children may not be perceived as being associated with malaria.

Malaria prevalence is inversely related to vector density in The Gambia, West Africa

Baseline epidemiological and entomological studies were conducted in 5 different areas of The Gambia before the introduction of a national malaria control programme, the objective of which was to treat all the bed nets belonging to people living in primary health care villages with insecticide. All malariometric indices used (parasite density, parasite rates, splenomegaly, and packed cell volume) indicated that malaria transmission was more intense in the east of the country than elsewhere. High transmission in the east was associated with a high sporozoite rate but not with the greatest vector abundance; the lowest malaria prevalence rates were found in villages which were close to very productive breeding sites of Anopheles gambiae s.l. Bed net usage was strongly correlated with vector density and the highest malaria rates were found in villages where bed net usage was relatively low. These results suggest that in The Gambia malaria prevalence rates are reduced where nuisance biting by mosquitoes is sufficient to encourage the population to protect themselves with bed nets.

A malaria control trial using insecticide-treated bed nets and targeted chemoprophylaxis in a rural area of The Gambia, west Africa. 2. Mortality and morbidity from malaria in the study area

Background data on child mortality and morbidity from malaria were obtained in a new study area in the centre of The Gambia, south of the river, chosen as the site for a malaria intervention trial. Infant and child mortality rates were 120 and 41 per 1000 respectively. Results obtained using post-mortem questionnaires suggested that malaria was an uncommon cause of death in children under the age of one year but responsible for about 40% of deaths in children aged 1-4 years. Ninety-two percent of deaths attributed to malaria occurred during or immediately after the rainy season. Parasite and spleen rates in children aged 1-5 years at the end of the malaria transmission season were 66% and 64% respectively. Malariometric indices were similar in primary health care (PHC) villages, selected as sites for an intervention with insecticide-treated bed nets and targeted chemoprophylaxis, and in smaller, non-PHC, control villages.