[ 2012-09-18 ]

New Malaria-Transmitting Mosquito Discovered in Kenya
Scientists from the London School of Hygiene and
Tropical Medicine, have discovered a potentially
dangerous new malaria-transmitting mosquito in
Kenya.

The species, which has never been implicated in
the transmission of malaria before, poses a threat
because it bites humans at times when they are not
protected by current malaria control techniques.

The commonly caught Anopheles mosquitoes that
transmit malaria in Africa, generally, prefer to
rest indoors and feed on humans at night. This led
to the development of programmes to stop the
spread of malaria such as spraying insecticide in
homes and issuing bed nets for people to sleep
under.

However, this mosquito was found to be active
outdoors and bite people earlier in the evening
soon after sunset.

The scientists warn of risk that bed nets and
insecticides could fail to fully protect the
population.

Lead author Jennifer Stevenson, Research Fellow at
the London School of Hygiene & Tropical Medicine,
said: “We observed that many mosquitoes we caught,
including those infected with malaria, did not
physically resemble other known malaria
mosquitoes.”

“Analysis indicated that their DNA differed from
sequences available for known malaria-transmitting
mosquitoes in Africa. These unidentified
mosquitoes are potentially dangerous because they
are outdoor-active and early-biting, and so may
evade the current indoor-based interventions to
control mosquitoes. In this way, they may prevent
the complete suppression of malaria transmission
in the area,” she said.

The study outlines how researchers set up indoor
and outdoor mosquito traps in a village in Kisii
in the highlands of western Kenya, an area with
seasonal and unstable malaria transmission. Over
65 percent of mosquitoes caught were outdoors, the
majority before 2230 hours.

Three hundred and forty-eight mosquitoes were
identified using DNA sequencing techniques of
which over 40 percent were found to be of this
unidentified species. Five mosquitoes of this
species were carrying malaria parasites and two
had fed on humans.

The researchers are now calling for increased
entomological surveillance and a focus on
integrating a wider range of malaria control tools
to deal with the threat of outdoor transmission.

Malaria is the leading cause of death in Kenya,
with 25 million out of a population of 34 million
Kenyans at risk of the disease.

Jo Lines, Reader in Malaria Control and Vector
Biology at the London School of Hygiene & Tropical
Medicine and former coordinator for the World
Health Organization’s Global Malaria Programme,
said: “These findings remind us that the basic
biology of malaria transmission is subtle and
complex: there are still plenty of gaps in our
knowledge, and local variations that we do not
understand. We do not yet know what these
unidentified specimens are, or whether they are
acting as vectors on a wider scale, but in the
study area they are clearly playing a major and
previously unsuspected role.”

“The practical implication for malaria control
programmes is that there is no substitute for
careful monitoring of mosquito populations. In
order to be effective, such monitoring must be
carried out by specialist experts who have the
skills to recognise and investigate unexpected
entomological observations.”

The researchers added that as these mosquitoes had
so far been seen only in one location in Kenya, it
was essential that tourists still protected
themselves with a mosquito net treated with a
long-lasting insecticidal treatment whilst
travelling.

The research was carried out in collaboration with
the Kenya Medical Research Institute under the
Malaria Transmission Consortium, funded by the
Bill and Melinda Gates Foundation. The findings
are reported in Emerging Infectious Diseases.

The London School of Hygiene & Tropical Medicine
is a world-leading centre for research and
postgraduate education in public and global
health, with 4000 students and more than 1300
staff working in over 100 countries.

The School is one of the highest-rated research
institutions in the UK, and was recently cited as
one of the world's top universities for
collaborative research. The School's mission is to
improve health and health equity in the UK and
worldwide; working in partnership to achieve
excellence in public and global health research,
education and translation of knowledge into policy
and practice.

Source - GNA

... go Back