Vector Control Using Semiochemicals - Biological and Environmental Control of Disease Vectors - page 98

Some recent research has been conducted
to create CO 2 by fermenting yeast using a yeast-
sugar solution, which, under anaerobic
condition, will convert sugar into CO 2 and
ethanol (Van Dijken et al. , 1993; Barnett, 2003;
Saitoh et al. , 2004; Walker and Dijck, 2006;
Hazelwood et al. , 2008). Trials have shown that
traps baited with this caught a greater quantity
of Stegomyia (formerly Aedes ) and Culex
mosquitoes than unbaited traps. More recently,
Smallegange et al. investigated whether yeast-
produced CO 2 could be used to replace industrial
CO 2 from a cylinder (Smallegange et al. , 2010b).
They found that MM-X traps baited with yeast-
produced CO 2 caught signifi cantly more An.
gambiae mosquitoes than unbaited traps and
traps baited with industrial CO 2 , under
laboratory and semi-fi eld settings. Although
some studies have also shown that traps baited
with yeast-derived CO 2 catch less mosquitoes
than dry ice (e.g. Saitoh et al. , 2004; Oli et al. ,
2005) this method is very promising as a
replacement of bulky CO 2 gas cylinders, sig-
nifi cantly reducing costs and allowing
sustainable mass-application of odour-baited
devices for mosquito sampling in remote areas
(Smallegange et al. , 2010b).

racemic mixture with varying success
(Vythilingam et al. , 1992; Kemme et al. , 1993;
Becker et al. , 1995; Mboera, L.E. et al. , 2000b;
Burkett et al. , 2001; Russell and Kay, 2004;
Miller et al. , 2005). However, the ratio of the
enantiomers from cattle breath varies between
80:20 R:S and 92:8 R:S (Hall et al. , 1984).
Although no dif erences in olfactory responses
(measured by electroantennogram) or be-
havioural response in between the (R) and the
(S) enantiomers have been found for tsetse fl ies
(Hall et al. , 1984; Vale and Hall, 1985), the ef ect
of the enantiomers and mixtures on other
insects is apparent. For example, increased trap
catches of Anopheles crucians and Ochlerotatus
infi rmatus can be achieved when using the (R)-1-
octen-3-ol enantiomer compared to the (S)-1-
octen-3-ol enantiomer (Kline, 2007). Both in
vivo and in vitro electrophysiological studies also
showed that Cx. quinquefasciatus and St. aegypti
mosquitoes displayed greater sensitivity to the
(R)-1-octen-3-ol enantiomer compared to the
(S)-1-octen-3-ol enantiomer (Syed and Leal,
2007; Bohbot and Dickens, 2009). Cook et al.
(2011) recently confi rmed that St. aegypti and
Cx. quinquefasciatus responded signifi cantly
more to the (R)-1-octen-3-ol enantiomer
compared to the (S)-1-octen-3-ol enantiomers
by electroantennogram. However, in laboratory
behavioural studies, St. aegypti responded more
to the (R)-1-octen-3-ol enantiomer, showing an
increase in fl ight activity and 'relative attraction'
compared to Cx. quinquefasciatus . The (R)-1-
octen-3-ol enantiomer caused an increase in
activation for Cx. quinquefasciatus , but a reduced
relative attraction than the response observed to
the (S)-1-octen-3-ol enantiomer. This dif erent
behavioural ef ect may be due to the dif erent
host preferences of the two mosquito species
studied (Cook et al. , 2011). For example, St.
aegypti preferentially feeds on human and other
mammalian hosts, whereas Cx. quinquefasciatus
preferentially feeds on birds (Takken and
Kline, 1989; Takken, 1991; Zinser et al. , 2004).
Since 1-octen-3-ol has been identifi ed from
mammalian odour previously, but never from
bird odour, one might expect the behavioural
responses displayed by St. aegypti and Cx.
quinquefasciatus mosquitoes to dif er in this study.
Field studies have also been performed with
Culicoides biting midges in the UK using traps
used for surveillance (miniature CDC model

1-Octen-3-ol
1-Octen-3-ol was originally identifi ed from the
breath of an ox (Hall et al. , 1984; Vale and Hall,
1985) and has since been shown to be ef ective
at increasing catches of tsetse fl ies, Culicoides
midges, Stegomyia and Anopheles species
mosquitoes (Vythilingam et al. , 1992; Kemme et
al. , 1993; Becker et al. , 1995; Kline and Lemire,
1995; Mboera, L.E. et al. , 2000b; Burkett et al. ,
2001; Russell and Kay, 2004; Miller et al. , 2005;
Kline, 2007). When used in traps, 1-octen-3-ol
is often used in combination with CO 2 , and this
synergistic relationship is usually required to
elicit signifi cant behavioural responses and to
increase trap catches.
1-Octen-3-ol exists in two enantiomeric
forms, and is known to be released by a variety of
vertebrates, as well as plants (Hall et al. , 1984;
Knudsen et al. , 1993; Kline, 2007). Most studies
have assessed the ef ect of this compound on
insects using only its racemic form (1:1, R:S
enantiomers). Indeed, most traps that employ
1-octen-3-ol, usually alongside CO 2 , use the