Malaria, Farms and Mobility

Whether overnight stays in farming huts poses a risk of malaria infection is a question being asked by researchers in Laos. Daisuke Nonaka and colleagues determined that “staying overnight in farming huts was not associated with an increased risk of malaria infection in the setting where ITNs were widely used in farming huts.”

Net use was greater in the rainy reason than dry in both farm huts (95% vs 66%) and main residences (82% vs 86%), and there were fewer nets on average in huts in the dry (1.1) and rainy seasons (2.3). The average number in main residences decreased from 3.1 in the dry to 2.1 in the rainy seasons.  This implies some movement of both people and nets between residences and seasons.

Another interesting finding was that there was higher prevalence of malaria when 5 or more people shared a net. Though the findings do not specify whether these sharing practices vary by residence or season, one might suspect a bit more crowding in the farm huts, and this should be explored.

village-huts-sm.jpgEnsuring adequate number of ITNs to achieve universal coverage when people have one residence is a big challenge. In fact most procurement estimates are based on population, not residences.  Are there enough nets to cover all sleeping spaces, even if this means extra nets for a family?

Researchers in Tanzania when net supplies were not as large as today found that, “The household’s location at the time of interview (whether at their farm or village homes) was associated with parasitemia, and those residing at their farms were more likely to be parasitemic than those at their village houses, all other things held constant.”

Likewise, we found that mobility between farm and town settlements affected availability and use of cloth filters to prevent guinea worm.  Absence from the farm settlement at the time of ivermectin distribution is an important factor that affects coverage in onchocerciasis prevention efforts.

Unlike bednets, cloth filters for guinea worm can be more easily carried from one residence to another, and ivermectin pills can be kept easily until a mobile villager comes back.  Bednets by themselves pose challenges of hanging in even one residence, but ultimately we need to address the challenge of matching bednet supplies with the fact that rural people can have more than one residence in order to eliminate the disease.

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