Biology Reference
In-Depth Information
may promote a greater spore uptake. Repeated
exposure to fungi may also increase the dose the
insects acquire, resulting in higher mortality
(Blanford et al. , 2005). Continuously returning
for blood meals creates multiple opportunities
for exposure of mosquitoes, thus maximizing
coverage.
Mosquitoes also may pick up spores from
other mosquitoes through copulation. Hori-
zontal transfer of fungi between infected and
uninfected mosquitoes has been demonstrated
in three laboratory studies. Copulation of
unexposed male and infected female anophelines
resulted in subsequent infection and reduced
survival of male An . gambiae s.s. (Scholte et al. ,
2004b). Male St . aegypti mosquitoes treated
with M . anisopliae and B . bassiana were also able
to transfer spores to untreated females resulting
in 90% mortality within 15 days, reductions in
fecundity of up to 95% and lower female
insemination rates (Garcia-Munguia et al. ,
2011; Reyes-Villanueva et al. , 2011). However,
these studies were carried out in the laboratory
in small cages where the opportunity for close
contact is increased, and further work in semi-
fi eld and fi eld systems is required to see whether
such ef ective horizontal transfer does also occur
in nature.
housefl ies that are implicated with diarrhoeal
disease (Dimbi et al. , 2003; Lecuona et al. , 2005);
cof ee plants treated with suspensions of B .
bassiana have been investigated for control of
Phlebotomus papatasi and Lutzyomia longipalpis
sandfl ies, the primary vectors of leishmaniasis
(Reithinger et al. , 1997); nesting boxes to attract
mice (reservoirs for Borrelia burgdorferi , the
agent of Lyme disease) on which Ixodes scapularis
ticks feed were treated with M . anisopliae spores
(Hornbostel et al. , 2005); boxes baited with
carbon dioxide were treated with B . bassiana
against Triatoma infestans bugs, vectors of
Trypanosoma cruzi (Pedrini et al. , 2009).
Using light volatile oils to formulate spores,
walls inside houses can be treated in a similar
way to those during chemical indoor residual
spray programmes (IRS). Applications of M .
anisopliae and B . bassiana to mud and clay tiles
are ef ective in reducing survival of adult An .
gambiae s.s. and An . stephensi mosquitoes in the
laboratory. Furthermore, exposure to such
surfaces appears to result in greater mortality
than to treated cloth or cardboard surfaces
(Mnyone et al. , 2010; Blanford et al. , 2011).
Dark attractive surfaces (Hecht and Hernandez-
Corzo, 1963; Stevenson, 2008) such as black
cotton cloth (Fig. 5.6) acting as resting targets
may be used in place of direct wall treatments
against St . aegypti (Edman et al. , 1997; Paula et
al. , 2011). Laboratory experiments have
demonstrated the ef ectiveness of treating black
cloth with spores against anopheline mosquitoes
(Scholte et al. , 2005; Stevenson, 2008; Mnyone
et al. , 2010, 2012; Darbro et al. , 2011;
Farenhorst et al. , 2011). In experimental huts in
Tanzania, B . bassiana and M . anisopliae -treated
netting and black cloth installed in dif erent
ways within the hut were tested for subsequent
infection and survival of An . gambiae s.l.
mosquitoes (Mnyone et al. , 2012) (Fig. 5.7).
Neither treated nets nor cloth curtains around
the eaves were able to infect mosquitoes with
fungi whereas treated cloth bal es installed at
an angle caused almost 70% of mosquitoes to be
infected and reduced survival by as much as
43% compared to controls. This ef ect was
increased by treating strips of black cloth that
were hung around a bed net; 76% of mosquitoes
caught were infected with fungi and survival
was reduced by 45% (Mnyone et al. , 2012).
Models demonstrate that such infection rates
Delivery systems tested
The majority of reports on potential uses of
fungi against vectors are based on laboratory
assays, employing either topical application
directly on to the insect (Romana and Fargues,
1992), contact with airborne spores (Clark et al. ,
1968), sporulating cultures (Rizzo, 1977;
Scholte et al. , 2004b) or treated paper surfaces
(Warburg, 1991; Maniania, 1994; Blanford et
al. , 2005; Lecuona et al. , 2005; Mnyone et al. ,
2009b). These techniques of infecting insects
were designed mainly as proof-of-principle
experiments and are not transferable for fi eld
use. More recently, traps and devices that could
be employed in the fi eld have been designed.
Pyramidal traps for tsetse fl ies, vectors of
trypanosomes, which cause human sleeping
sickness, were modifi ed to have contaminative
devices containing M . anisopliae spores
(Maniania et al. , 2006); traps with spore-treated
food baits such as rice, maize cobs and molasses
have been used against Musca domestica
 
Search WWH ::




Custom Search