Control of Disease Vectors using Fungi - Biological and Environmental Control of Disease Vectors - page 81

could result in reductions of entomological
inoculation rates (EIR) of up to 80%. Developing
delivery systems that exploit mosquito behaviour
(upwards fl ight and host seeking) can therefore
maximize coverage.
The fi rst village fi eld trials using black
cotton cloth were also carried out in Tanzania,
where formulations of M . anisopliae with low
vegetable oil content (8%) were used. Black
cotton sheeting (3×1 m 2 ) was treated by
sprinkling 700 ml of the oil formulations over
the material and kneading it by hand (Scholte et
al. , 2005). Cotton cloth targets, found to be
relatively attractive to resting mosquitoes, were
installed in houses as resting targets. Of those
mosquitoes collected from treated houses,
approximately one-fi fth became infected.
Although no signifi cant overall dif erence in
survival was found between those caught in
treated and untreated houses, survival of
fungal-infected An . gambiae s.l. mosquitoes from
treated houses was signifi cantly less compared
to that of uninfected mosquitoes. Modelling the
impact on potential malaria transmission
suggests a reduction in sporozoite rates and EIRs
by up to 75% if community-wide fungal control
was implemented for 1 year (Scholte et al. ,
2005).
Applying fungi to bed nets has also been
suggested as a mode of delivery. Success has
been demonstrated in the laboratory by treating
netting. Exposure of mosquitoes to fungal-
treated netting in cone and tube assays has been
shown to reduce survival of An . gambiae s.s.
(Howard et al. , 2010a, 2011), with treatment of
cotton netting resulting in higher mosquito
mortality than polyester (Farenhorst et al. ,
2011). This was attributed to better spore
adhesion to the more fi brous cotton strands.
Furthermore, passage through the net holes was
shown to have greater impacts on survival
(Farenhorst et al. , 2011). Whereas exposure to
B . bassiana and M . anisopliae is generally
thought not to have any substantial impacts on
human health (Section 5.3.4), the formulations
applied to materials with which people have
regular contact will have to undergo rigorous
safety checks. Bed nets are also regularly
washed, undoubtedly reducing the persistence
of the treatment. With this in mind, the use
of fungal-treated net curtains was investigated
in experimental huts in Benin against Cx .

quinquefasciatus mosquitoes (Howard et al. ,
2010b) (Fig. 5.8). While reductions in mosquito
blood feeding were demonstrated in huts fi tted
with B . bassiana and M . anisopliae -treated
curtains, there were no signifi cant reductions in
adult mosquito survival. As with the installation
of the treated cloth targets in Tanzania, it
appeared that coverage was not high enough to
observe such an impact.
Attention has also focused on applications
in traps, which may be attractive to mosquitoes,
encouraging longer resting periods and
therefore resulting in higher infection rates.
Research focused on the use of clay pots that
had been shown to harbour high numbers of
resting anophelines in the lowlands of western
Kenya (Odiere et al. , 2007; Mouatcho, 2011).
Anopheles arabiensis , An . quadriannulatus , An .
merus , An . parensis and An . funestus became
infected following exposure to M . anisopliae and
B . bassiana -treated clay pots in the laboratory
(Mouatcho, 2011), and Farenhorst et al . (2009)
demonstrated infection rates of more than 90%
as well as signifi cant reductions in survival of
An . gambiae s.s. and An . funestus released into

Fig. 5.8. Eave curtains installed in experimental
huts in Benin. (Photo courtesy of Marit
Farenhorst.)