Mosquitoes ‘change feeding habits’

By GATONYE GATHURA

Malaria infections could be on the rise again as mosquitoes learn new tricks such as changing meal times and feeding on unprotected boda boda riders and early morning palm wine tappers.

The rise in malaria, after an almost 50 per cent decline mainly at the Coast, threatens the country’s 2017  eradication target.

Starting today through to Friday, the new threat will be the major topic of discussion among more than 100 medical experts attending a scientific conference at the Kenya Medical Research Institute.

Researchers will present evidence showing how the malaria-causing mosquitoes have learnt to feed on humans, even when they sleep under chemically-treated mosquito nets.

Tomorrow, Dr Eric Ochomo of Kemri, Kisumu, will present findings from a study carried out in Gem and Bungoma which demonstrate that the nets are no longer effective in killing or scaring away the insects. The findings also show that the nets do not last as long as the promised five years.

“In Gem, 83.3 per cent of nets were less than three years old and 32.4 per cent had holes; while in Bungoma, 92 per cent were less than three years old and 48 per cent had holes.”

He also found up to 94 per cent of the insects had developed resistance against the common net treating chemicals. He concludes that such nets are not protecting people against malaria at all and new strategies need to be thought out.

Even in highland areas such as Vihiga,  the nets are not doing any better while the mosquitoes have also changed their meals times.

According to Dr Peter Githeko, also of Kemri and who will be presenting his findings on Thursday, the malaria mosquito is feeding early in the evening before humans go to sleep under nets.

“A shift has occurred in the biting time for the insect to early evening, feeding almost exclusively on humans. This may maintain malaria transmission despite the high usage of nets,” says the Vihiga study.

Another study by both Kemri and Michigan State University, US, shows how a mosquito which had stopped transmitting malaria in the 1990s is doing so again in Asembo in Nyanza.

“These results are of serious concern for public health in the region, indicating that this type of mosquito may once again be contributing significantly to the transmission of malaria in this region despite the widespread use of bed nets.”

But even in areas where malaria has declined significantly such as Malindi and Magarini at the Coast, there are concerns that residents have become too complacent while the insect is hunting outdoors.

A study to be presented by Dr Lydia Kibe of Kemri-Wellcome Trust shows that mosquitoes are feeding on unprotected boda boda operators, men waking up early to harvest and tap palm wine and those playing cards late into the night.