As today is World Water Day it is time to reflect on the relationship between water and malaria. As USAID notes, “The impact of water on all aspects of development is undeniable: A safe drinking water supply, adequate sanitation and hygiene, management of water resources, and improvement of water productivity can help change the lives of millions.”
The key to the relationship between water and malaria is the word safe. The breeding of the malaria carrying anopheles mosquito species certainly depends on unsafe collections of “clean” but unmoving sources water that could range from a village pond to a cow hoof print. During certain seasons these are ubiquitous.
Seid Tiku Mereta and colleagues showed us recently that humans may be their own worst enemies when it comes to producing mosquito larval breeding sites. They found that Anopheline mosquito larvae showed a widespread distribution and especially occurred in small human-made aquatic habitats… In contrast, anopheline mosquito larvae were found to be less prominently present in permanent larval habitats. This could be attributed to the high abundance and diversity of natural predators and competitors suppressing the mosquito population densities.”
The drier parts of northern Benin Republic were studied by Renaud Govoetchan and team. They also found that human activity created water sources in urban areas in the dry season thereby “maintaining the breeding of anopheles larvae and the malaria transmission.” In the rural areas village ponds provided opportunity for dry season mosquito breeding. Although transmission was lower in the dry season and in the urban areas, it still persisted thanks to human water use behaviors and persistence of unsafe rural water sources.
From the above we can see that safe water alone would not prevent malaria. Water use behaviors must also be targeted. That said, it is interesting how water may also be related to other malaria interventions such as insecticide treated nets and case management with local herbs.
A major factor that influences the durability of the so-called long lasting insecticide treated nets (LLINs) is how often people wash them. Frequent washing of curtains, bed sheets and of course personal clothing is so routine that villagers may not even consider this hygenic behavior to be harmful. In fact it reduces the potency of the insecticide-treated nets.
Virgile Gnanguenon and co-researchers found that LLINs that might be expected to last 3 years if they were only occasionally washed were in fact only likely to be functional for two years or less. Water issues were prominent among the five factors that predicted net integrity and survival: “washing frequency, proximity to water for washing, location of kitchen, type of cooking fuel, and low net maintenance.”
Finally because primary health care does not reach all, community members still use their indigenous herbs to treat malaria. A recent study by Sabine Montcho and colleagues found an unexpected risk from the herbs. In Benin the plant Senna rotundifolia Linn. is commonly used for malaria treatment. Unfortunately the researchers learned that it was contaminated with lead and cadmium. “In terms of risk assessment through the consumption of Senna, the values recorded for lead were nine times higher with children and six times higher with adults than the daily permissive intake.” Polluted water does not have to be drunk directly to harm people.
Our relationships with water and malaria and the connection between the two are complex. World Water Day should provide us an opportunity to consider how our interventions ranging from appropriate use and care of LLINs, to provision of appropriate malaria treatment to larvae control and environmental management need to take into consideration the importance of water to human survival and disease prevention.