Vector Control Using Semiochemicals - Biological and Environmental Control of Disease Vectors - page 101

Sumba, 2008) (see Lorenz et al. , Chapter 4, this
volume).
Biological activity of the synthetic
pheromone, in an ef ervescent tablet for-
mulation, convenient for fi eld use, operated for
up to 10 m in Kenya (Otieno et al. , 1988).
Furthermore, addition of an insect growth
regulator (IGR) to the formulation pyriproxyfen,
2-(l-methyl-2-(4-phenoxyphenoxy)ethoxy)
pyridine, did not af ect the activity of the
pheromone but induced 100% mortality by the
pupal stage in a sample of larvae taken from the
treated site, suggesting that a lure-and-kill
strategy is possible in the fi eld (Otieno et al. ,
1988). The lure in such a strategy could be
further enhanced by combining the synthetic
pheromone with site-specifi c cues. For example,
in the laboratory, it was demonstrated that, when
presented individually, both polluted water and
erythro-6-acetoxy-5-hexadecanolide received
more oviposition by gravid Cx. quinquefasciatus
mosquitoes and, when combined, the ef ect was
additive (Mordue et al. , 1992). Similarly, an
additive ef ect has been observed when combin-
ing the synthetic pheromone with skatole,
3-methylindole, in the fi eld (Mboera, L.E.G. et al. ,
2000). Indeed, a synergistic response has been
observed when combining the pheromone with
grass infusion and soakage pit water (Mboera,
L.E. et al. , 2000a), and even low doses (3.0 μg of
(-)-(5R,6S)-6-acetoxy-5-hexadecanolide, a dose
equivalent to ten egg rafts) elicited a synergistic
ef ect with hay infusion in gravid Cx.
quinquefasciatus females (Braks et al. , 2007). An
alternative lure-and-kill formulation used a
synthetic mixture of diasteromers of 6-acetoxy-
5-hexadecanolide incorporated in polyurea
microencapsules, combined with the larvicide
temephos, for the control of Cx. pipiens
mosquitoes (Michaelakis et al. , 2007). The
optimum dose of 300 mg of dried microcapsules
attracted mosquitoes for up to 40 days, and
temephos provided larvicidal activity without
compromising the ef ect of the lure (Michaelakis
et al. , 2007). In certain areas of the USA,
restricted to where there is no disease present,
traps baited with environmentally friendly
oviposition semiochemicals, such as oviposition
pheromones and infusions, play an important
role in integrated programmes for the control of
Cx. quinquefasciatus , by minimizing the use of
insecticides (Michaelakis et al. , 2009; Mao et al. ,

2010). For example, skatole, and grass infusion,
has been suggested to be combined with Bacillus
thuringiensis var. israelensis in BR-OVT traps for
control of Cx. quinquefasciatus in Brazil (Barbosa
et al. , 2010b).
The role of odorant binding proteins
(OBPs), found in the female's antenna, in
sensing oviposition cues has been studied in an
attempt to identify and screen suitable synthetic
mosquito oviposition attractants for surveillance
and control programmes for Culex species (Leal
et al. , 2008). The OBP1 for Cx. quinquefasciatus
(CquiOBP1) bound to the oviposition pheromone
6-acetoxy-5-hexadecanolide (Zhou et al. , 2004;
Leal et al. , 2008; Mao et al. , 2010). By using
both CquiOBP1, as a molecular target in bind-
ing assays, and gas chromatography-electro-
antennographic detection (GC-EAD), nonanal,
trimethylamine (TMA) and skatole were
identifi ed as test compounds, and TMA (0.9 μg
l −1 ) and nonanal (0.15 ng ml −1 ) were shown to
be equivalent in attraction to the infusion-based
lure currently used in gravid trapping in Recife,
Brazil (Leal et al. , 2008).
Trapping using gravid traps detected higher
rates of West Nile virus infections in gravid Cx.
quinquefasciatus for arbovirus surveillance in
North America than for other collection
methods (Lukacik et al. , 2006; Williams and
Gingrich, 2007). The potential role of gravid
trapping for monitoring of lymphatic fi lariasis
(LF), caused by Wuchereria bancrofti , in the
mosquito vectors (xenomonitoring) has been
recognized (S. Irish et al ., personal com-
munication). The disease is easily treated using
mass drug administration (MDA) and has been
targeted for elimination by 2020 (WHO, 2011).
However, as MDA often relies on the voluntary
attendance of the local population, there is a risk
that transmission will persist due to the presence
of untreated people in the community. The
dii culties in reaching all members of the
community have led some LF monitoring
agencies to consider xenomonitoring, but, as
rates of infection in mosquitoes are often quite
low, this strategy is dependent on the collection
of large numbers of mosquitoes for testing
(Pedersen et al. , 2009). Previous typical methods
included the use of light traps next to untreated
bed nets (Simonsen et al. , 2010), pyrethrum
spray catches (Boakye et al. , 2007) or hand
captures (Farid et al. , 2007). Gravid traps have