I continue my visit to Kenya (back in Nairobi) and by coincidence the most interesting article in Malaria World this week relates to Kenya and was carried out by researchers from KEMRI, whose meeting I reported recently. ‘Impact of Titanium Mining and Other Anthropogenic Activities on Malaria Positivity Rates and Parasitemia in Five Selected Study Sites in Msambweni Subcounty, Kwale County, Kenya’ by Githinji et al studies Plasmodium positivity by RTD and microscopy in five villages. One village had titanium mining activities (Mwaloya), one sugar cane farming (Fahamuni), one had a dam (Marigiza), another had all three (Gonjora) and the fifth, the control (Mafisini), had none of these three human activities.
The results were quite clear especially comparing the village Mafisini (11.0% by RTD) with none and Gonjora with all three (33.7% by RTD). The villages with one activity had intermediate values. Mining, despite its prominence in the title, had the least effect (Mwaloya 17.6%) followed by Dam (Marigiza 23.3%) and Sugar cane farming (Fahamuni 26.8%).
No other differences between the villages were mentioned (e.g. poverty) and the authors admitted to limitations of the study. All of the explanations of the differences were linked to effect on mosquito habitats demonstrating the acceptance of the researchers of the conventional transmission model. The dam is a breeding ground for mosquitos. Sugar farming requires tilling of the land that results in additional pools in which mosquitos can breed. Mining requires the use of earth moving equipment that also results in pools for mosquito breeding. On the positive side, the wealth from mining pay packets, can benefit with improved houses and ability to buy malaria deterring items like bed nets. This explains why mining is the least bad of the three activities.
But what if mosquitos are not a factor in the transmission of malaria? We could explain the effects on increased positivity due to possible additional environmental toxins from these activities. The villages with a dam use potentially contaminated surface water instead of cleaner ground or piped water in areas without dams. Sugar cane farming uses a lot of pesticides. Mining operations use and unearth many toxic materials. And adding all three together could have a big additional effect.