Journal of Mosquito Research 2015, Vol.5, No.14, 1-8
2
of the individual components which has contributed to
the overall reduction in the malaria burden.
However, the success of the IMM program has some
challenges, especially with use of insecticides. This is
because, resistance to conventional insecticides, a
phenomenon currently widespread across Sub-Sahara
Africa has been reported (Ochomo et al., 2014;
Russell et al., 2010). Resistance to pyrethroids
presents a real and immediate challenge to the efficacy
of otherwise successful insecticide treated nets (ITN)
based malaria control intervention against adult vector
(Russell et al., 2010). The long-lasting insecticidal
nets (LLIN) and/ or indoor residual spraying (IRS) has
influenced
An. gambiae
population and their host
seeking behavior with demographic coverage of
humans dramatically reducing in relation to infection
prevalence of
Plasmodia
in
An. gambiae
(Russell et
al., 2010; 2011).
Previous studies in Mwea and Ahero (Kamau and
Vulule, 2006; Kamau et al., 2007) found no resistance
to insecticide groups that have been recommended by
WHO for Indoor Residual Spraying, including
pyrethroids. Prolonged continuous use of insecticides
such as that which has been carried out in the country
by the Ministry of Health has been shown to result in
increased resistance in various settings (Jeffrey and
Pia, 2002). Developments that could impact insecticide
resistance in Kenya include increased awareness of
the effectiveness of ITNs as a result of concerted
social marketing efforts such as was witnessed
between 2002 and 2004 and increased availability of
ITNs either through the provision of heavily
subsidized ITN distribution by the Ministry of Health
or through free mass ITN distribution through various
programmes. Additionally, the use of pesticides for
agriculture has also been found to be key driver of
resistance in mosquito populations (Riveron and
Wondji, 2014). It is widely accepted that increases in
insecticide resistance will negatively impact the
sustainability of vector control strategies employing
insecticides. Thus, continued monitoring of resistance
is necessary so as to detect and manage any developing
resistance in a timely manner. The study reported
here sought to determine the status of insecticide
resistance in Mwea and Ahero some eight to ten years
after earlier studies indicated the absence of
insecticide resistance and whether there have been
changes in blood feeding behavior and malaria
parasite rates in the vectors of malaria.
Materials and Methods
Study Sites
This study was conducted between the months of
October 2009 and June 2011 in Mwea and Ahero rice
irrigation zones. Mwea (37.25
0
E, 1.42
0
S) is located
on the base of Mount Kenya, Central Kenya, with a
population of about 160,000 (Kenya National Bureau
of Statistics, 2009). Mwea experiences long and short
rain seasons from March to June and October to
December, respectively. The mean annual rainfall
level is between 1200 to 1600 mm with rice cultivation
as the main agro-economic activity. Rice cultivation
involves flooding of rice paddies thus potential
breeding sites for mosquitoes. The species of
Anopheles
mosquitoes in the Mwea region include
Anopheles
arabiensis
Patton 1905,
Anopheles funestus
Giles
(Kamau and Vulule, 2006; Ijumba et al.
,
2008; Muturi
et al., 2008) and
Anopheles gambiae
sensu stricto
Giles 1902 (Ijumba et al., 2008; Kamau et al., 2007).
Recent studies in Mwea have reported susceptibility
of
An. gambiae
to the conventional insecticides,
especially permethrin and deltamethrin (Kamau and
Vulule, 2006).
Ahero (34.90
0
E, 0.16
0
S) is located 24 Km East of
Kisumu town along the shores of Lake Victoria in
Western Kenya. It has a human population of 50, 730
(Kenya county fact sheets December 2011). The site
experiences long and short rainy seasons from March
to May and September to December, respectively. The
mean annual rainfall level is between 1,000 to 1,800
mm with rice and sugar cane cultivation and fishing
forming part of their major agro-economic activities.
In Ahero, the presence of river Nyando facilitates rice
fields’ irrigation thus breeding grounds for mosquitoes.
The species of
Anopheles
mosquitoes in Ahero include
Anopheles arabiensis
Patton 1905,
Anopheles funestus
Giles (Bruhnes, 1978) and
Anopheles gambiae
sensu
stricto Giles 1902 (Chandler and Highton 2009).
Reports on insecticides resistance indicate
An. gambiae
is susceptible to conventional insecticides (Chandler
and Highton 2009). Apart from feeding on humans,
non- human hosts include bovines, goats, dogs, felines,
birds and reptiles (Githeko et al., 1994).
