Some Contrasts in the Regional Geography of Malaria in India and Pakistan

Hydrological and geomorphological controls of malaria transmission

“…Learmonth (1957) reported malaria epidemics in Sind due to such riverine flooding, rather than local rains. Similarly, river fluctuations explain the various associations between malaria risk and rivers observed in areas of perennial flows.…”

“…Crucially, the flushing effect coincides with the time of year where temperature favours vector breeding (Learmonth, 1957). The small amount of breeding in the wetter east Bengal in contrast to the drier 'dying' delta in west Bengal can be further explained by the inability of the dominant vector Anopheles philippinensis to breed in surface water bodies formed by a high water table.…”

“…These local topographic depressions may be formed naturally, or may arise as a consequence of housing, infrastructure or irrigation canal construction. They are especially prevalent alongside roads or railways that cut across catchment drainage lines (Learmonth, 1957). Bomblies et al (2008) found that such pools were the sole source of breeding habitats in a desert-fringe village in Niger and formed local hotspots for malaria risk.…”

“…Likewise, in tropical lowlands where large anabranching river systems are commonplace, channel avulsion and discharge related changes in channel form and density can potentially alter the risk of malaria transmission in floodplains and valley bottoms radically. Meanwhile, abandoned channels (palaeochannels) form suitable breeding sites during heavy rainfall events or inundation from the main channel (Learmonth, 1957). The history of geomorphological responses to climate change can be reconstructed from sedimentological analyses of fluvial sedimentary archives, providing greater understanding of potential effects of predicted climate change (see Macklin et al, 2012).…”

“…Mapping was a central tool, embedded within an appreciation of hydrological and geomorphological processes responsible for the formation of suitable habitats (e.g. Learmonth, 1957). In the latter half of the century, widespread use of residual insecticides such as dichlorodiphenyltrichloroethane (DDT, which acts by killing adult mosquitoes when they come in contact with the sprayed surface) were employed as part of a major international drive towards malaria elimination.…”