By Gatonye Gathura
The malaria causing mosquito has developed high levels of resistance against DDT while the chemical is poisoning soils in western Kenya where it is in use.
Two separate studies have put into question the rational of using a chemical, which may be carcinogenic to humans, against a resistant enemy and in the process needlessly poisoning agricultural land.
The latest study by researchers affiliated mainly to the Chinese Academy of Sciences and the Sino-Africa Joint Research Center based in Nairobi, reports unhealthy levels of soil contamination with DDT and the agricultural chemical endosulfan.
Soil samples collected from malaria areas especially in the western highlands showed high levels of contamination from more than 26 types of pesticides.
DDTs and endosulfan were the dominant in that order and further analysis showed the source being recent use of DDT in malaria control programmes.
The team published the results in a February issue of the journal Environmental Pollution and is clear that the contamination in the soil presents a significant threat to human health.
The findings of the second study are reported in the: Dispatch, Volume 21, Number 12—December 2015 of the US Centers for Disease Control and Prevention – Nairobi, showing that the malaria causing mosquito has developed high levels of resistance against DDT in western Kenya.
The Dispatch cites a study carried out by researchers from the Kenya Medical Research Institute, Kenyatta University, Kenya, Masinde Muliro University of Science and Technology, Kenya, and University of California, US, and funded by the US National Institutes of Health.
“We conducted standard insecticide susceptibility testing across western Kenya and found that the Anopheles gambiae mosquito has acquired high resistance to pyrethroids and DDT.”
The US study also confirms public speculation that Kenya’s Ministry of Health has been quietly using DDT for malaria control.
“In Kenya, current policy on indoor residual spraying use of insecticides is limited to pyrethroids and DDT,” says the Dispatch.
Kenya banned the use of DDT for agriculture use in 1986 but around 2010 there was a huge campaign to bring it back for malaria control.
Then the agriculture sector had opposed DDT use, arguing it could find its way in the food chain and threaten the country’s horticulture export market estimated at $355 million annually.
But now Kenya may be exploiting the WHO option allowing a group of high malaria countries a limited use of DDT in mosquito control.
Ironically Kenyans may be poisoning themselves for no gain because the extensive study described in the dispatch indicates DDT is no longer killing mosquitoes since they have developed resistance.