The government of Malawi is rapidly scaling up a full range of existing evidence-based malaria prevention and control strategies. These strategies include use of ITNs, IPTp and prompt and effective case management, particularly among children who are sick with malaria. Between 2005 and 2008, 3,727,330 nets (PSI, personal communication) were distributed and a new malaria treatment policy was implemented countrywide, with artemether-lumefantrine replacing SP as the first-line drug. A modest, non-statistically significant increase in ITN household ownership (from 41.5% to 45.3%) and a statistically significant increase in adherence to any net (regardless of treatment status) were observed between 2005 and 2008. The results also show a moderate reduction in the odds of anaemia; the prevalence of anaemia decreased by a modest 15-16% from baseline, depending on the type of survey. In light of these data, and the very recent introduction of ACT, it can be argued that anaemia is a sensitive indicator to the scale up of malaria interventions and may thus be used as a proxy indicator to track the burden of malaria and demonstrate timely impact of malaria interventions in areas of high malaria This finding is important because existing impact indicators are either hard to measure at the national scale (e.g. all-cause under-five mortality, malaria-attributed mortality) or not sensitive enough to changes in malaria transmission (e.g. parasite prevalence). In contrast, anaemia is measurable and quantifiable in the field with the portable HemoCue haemoglobinometre using small volumes of capillary blood, it requires a smaller sample size, and gives more precise results than does measurement of all-cause mortality for children under-five years of age. However, anaemia may have limited utility in areas of lower malaria transmission where the attributable fraction of anaemia due to malaria is too low to reflect changes in malaria transmission/control.
Parasitaemia, another common indicator used to assess malaria control, was also evaluated in this study. The prevalence of parasitaemia was reduced by 11% in the HH survey and 57% in the EPI-HF survey. This observation supports the finding above that reduction in both anaemia and parasitaemia could have been due to the modest scale up of malaria interventions. The dramatic reduction in parasitaemia observed in the EPI-HF survey was unexpected but could be due to accidental inclusion of some sick children during the EPI-HF survey in 2005. This is supported by the data showing that the proportion of children who had fever at the time of recruitment into the EPI-HF survey was significantly decreased from 11.7% to 4.6% between 2005 and 2008 (p < 0.0001). A corresponding decrease was also observed in children presenting to the clinic with a history of fever in the past 48 hours (p < 0.0001)(see Table A, additional file 1). Adjusted analyses revealed that the reductions in the odds of parasitaemia in both types of surveys were not significantly different from each other.
Not surprisingly, the reduction in the prevalence of anaemia and parasitaemia observed in this study was very modest. A similar household evaluation conducted among children under five years of age in Zambia has reported over 50% reduction in both parameters between 2006 and 2008, likely due to an increase of >20% in household ownership of at least one mosquito net following a mass distribution campaign . Household ITN ownership in the Malawian study only increased from 41.5% to 45.3% (p = 0.10) during the three-year interval. This modest and non-significant increase could be explained by several factors. First, between 2007 and 2008, the procurement and distribution of ITNs experienced a lot of logistical problems resulting in fewer subsidized nets being delivered to the target groups (PSI, personal communication). As a result, most of the ITNs during this period were only distributed after the 2008 follow up surveys. Secondly, there is the possibility that because the distribution of ITNs was targeted to only households with pregnant women or children aged less than five years, during the period between the two surveys, the same households were reached with ITNs as a result of the targeted distribution. This is supported by the fact that overall net ownership did not increase during this period. Population growth could also explain the modest increase in household ITN increase. While the number of new nets distributed is known, population growth in the communities surveyed is not known with a possibility that fewer nets were distributed compared to population growth. This failure to significantly scale up household ownership of ITNs has been reported in other surveys . In this survey, in households with at least one ITN, over 75% of the children slept under an ITN suggesting good adherence to nets among children under five as has been reported elsewhere . Therefore, in Malawi, more needs to be done to achieve the Roll Back Malaria target of protecting 80% of the population at risk by 2010. Rapid scale up of the ITN programme through mass distribution to achieve universal coverage could significantly reduce malaria morbidity, and especially malaria-related anaemia.
This study also shows that the reduction in anaemia, as measured during EPI-HF surveys, was similar to the reduction measured during the household surveys. Thus, anaemia measured at the EPI clinics at the facility level may be a good surrogate indicator of anaemia measurement at the household level. This finding has important programmatic implication because EPI-HF surveys have the advantage of being cheaper and logistically simpler to execute than household surveys. In addition, measurement of anaemia in the EPI clinic would be only a small burden for health workers since surveys would only be done periodically. The ability to measure the impact of malaria interventions through EPI clinics could afford District Health Management Teams the means to quickly evaluate the impact of the malaria programme and inform the efficient deployment of malaria interventions within the district.
The results of this evaluation should be interpreted in the context of the limitations of the study. The causes of anaemia are multifactorial; paediatric HIV infection and malnutrition are prominent ones [12–14]. As a result the reduction in the prevalence of anaemia observed in this study could be affected by improvements in coverage of non-malaria related interventions. This study did not collect information on other competing causes of anaemia, such as nutritional status, HIV, hookworm infection, helminths, or bacteraemia. However, between 2005 and 2008, there were no large scale nutritional interventions or other child health interventions that underwent rapid scale up in the selected districts which could have led to the decrease in the prevalence of anaemia. Children in the household surveys were significantly older than children in the EPI-health facility surveys (p < 0.0001). This difference in age may have introduced bias in the results; however, this is unlikely as the prevalence of anaemia in the EPI-HF survey compared very well to that in the household survey. Despite these limitations, it is reasonable to argue that the very modest decline in anaemia prevalence was as a result of the small increase in malaria control interventions, specifically the scale up of ITN coverage and the introduction of ACT, since other proxies for malaria such as fever in the last two weeks were also significantly reduced between 2005 and 2008.
The sampling strategies for the two household surveys were different from one another. In 2005, a simple random sample of households in each EA was selected, whereas in 2008, information was collected from all households in a randomly selected segment of each EA. Although both strategies have been validated [8, 9], both strategies experienced challenges in the application of the respective techniques because of the physical size of EAs in Malawi. If some households were inadvertently missed due to these challenges, it may result in a bias in the estimates presented here. The generalizability of these results is also limited by the fact that the selection of districts, although geographically representative of the different transmission strata in Malawi, was a convenience sample. Furthermore, the EPI-HF survey was restricted to only three districts due to financial and logistical constraints.