Mosquitoes have become smarter. Some are avoiding homes and instead hang around primary schools waiting for children who arrive for early morning preps, a new study says.
They immediately begin feasting on the pupils at 6am.
Researchers who established this pattern said they believe the mosquitoes are going to schools to avoid the treated bed nets distributed in homes in Western Kenya by the Ministry of Health and its partners.
“The early morning biting observed here points to a change in behaviour to avoid bed nets,” they said in results presented at the ongoing Kenya Medical Research Institute (Kemri) Annual Scientific and Health (Kash) Conference in Nairobi.
The 14 researchers, led by Kemri’s Eric Ochomo, conducted the study in four day primary schools in Alego-Usonga, Siaya County. These schools are Bukhoba, Gangu, Kanyaboli and Gendro.
Children in these schools wear shorts.
Siaya has the second highest malaria prevalence nationally and residents regularly receive long-lasting insecticidal nets (LLINs).
The Kemri researchers camped in the four schools between August 4-6, 2023.
They observed that many children consistently arrived at school between 6am and 7am. They would find mosquitoes waiting for them.
“Interestingly, the peak in biting was at 6am, just as the children would normally be arriving at school,” they said.
The researchers also collected most mosquitoes that landed on people, every hour, until 11am.
Most of those collected were the anopheles funestus, which transmits malaria with a notoriously high efficiency.
At least half of them were full of human blood or were carrying eggs.
“Surprisingly, more than half of all the mosquitoes collected landing on the collectors were either already fed or gravid, suggesting that the vector has a repeat feeding behaviour,” they said.
“This means that children sitting in these structures are potentially being bitten during their morning classes as they sit still and pay attention during their lessons.”
Several past studies have reported changes in mosquitoes biting behaviour, with changing preference towards early evening and late morning biting when people are often not under the protection of their bed nets.
However, this is the first investigation of anopheles vectors as a contributor to malaria transmission within these school settings.
The study notes many children in high transmission settings have developed immunity by this age.
Such children are less likely to seek treatment than younger children and therefore less likely to have the parasitaemia cleared with antimalaria drugs.
They are also likely to have the poorest usage of nets thus remaining important reservoirs of infection in the communities, the researchers said.
They also tested some of the mosquitoes and at least 2.05 per cent of them had plasmodium falciparum sporozoites, which means they could spread malaria.
“This study highlights the need to consider vector control approaches in schools,” the authors said.
The use of vector control in schools has the potential to reach a large asymptomatic reservoir of infectious individuals, they said.
Their study, "Late morning biting behaviour of anopheles funestus is a risk factor for transmission in schools in Siaya", has also been published in the Malaria Journal.
The co-cuthors are Seline Omondi, Jackline Kosgei, George Musula, Margaret Muchoki, Bernard Abongo, Silas Agumba, Caroline Ogwang, Daniel McDermott, Martin Donnelly, Sarah Staedke, Jonathan Schultz, Julie Gutman and John Gimnig.
The Ministry of Health recently distributed long-lasting insecticidal nets in six high-burden counties of Siaya, Kisumu, Migori, Kwale, Mombasa and Taita Taveta.
The exercise, which started in January, was completed on February 3.
The ministry distributed 262,865 nets in Taita Taveta, 668,779 in Kwale, 932,284 in Mombasa, 738,008 in Siaya, 858,658 in Kisumu and 829,507 in Migori.
"After distributing nets in these six counties, we shall proceed to distribute in 10 more counties in March and April until all the targeted population receive their requisite LLINs," Public Health PS Mary Muthoni said.
