Introduction - Biological and Environmental Control of Disease Vectors - page 4

transmission settings (e.g. an 18-fold reduction
in EIR between 1990 and 2008 in the
Kilombero Valley, Tanzania; Russell et al .,
2010), alternative control methods will
increase in relative importance (Shaukat et al .,
2010). Whereas chemical control is highly
ef ective at early stage control programmes,
more species- and location-specifi c malaria
control (such as environmental and biological
control methods) will become a central
component in low and moderate transmission
settings when disease incidence nears
elimination (Beier et al ., 2008). Thus, both for
malaria control and for control of other vector-
borne diseases (Table 1.1), alternative, sus-
tainable and environmentally friendly methods
that do not select for resistance and that are
locally adaptable, are required.

This knowledge is leading to the increasing
recognition of the importance of combining a
range of dif erent control methods within
programmes, sometimes not just to fi ght one
disease but to target several vectors or diseases
within one programme (see Cameron et al .,
Chapter 10, this volume). Integrated vector
management (IVM), adapted from the agri-
cultural concept of integrated pest management,
is being hailed for the sustainable management
of disease vectors (Thomas et al ., 2012;
WHO, 2012a) and should complement already
existing disease control strategies to avoid the
dependence on single methods (e.g. Killeen et al .,
2000).

1.2 A Role for Environmental and
Biological Control

1.1.3 Specifi cally tailored control
interventions

So, what are the alternatives to supplement the
use of insecticides in disease control, and to
restrain the evolution of insecticide resistance in
vectors? Options for vector control include
chemical control, environmental management,
biological control and personal protection, such
as use of repellents, wearing protective clothes
and sleeping under bed nets.
As described above, environmental
management, which includes environmental
modifi cation, environmental manipulation and
modifi cation of human habitations (WHO,
1980), is a viable option that has been
successfully employed in water management
schemes, such as drainage and irrigation (see
Konradsen et al ., Chapter 9, this volume), in
vegetation manipulation schemes (see Lorenz et
al ., Chapter 4, this volume), in sanitation
schemes to develop more hygienic sanitation
options and reduce diarrhoeal infections (see
Ensink et al ., Chapter 8, this volume) and in
house improvements, including house screening
(see Kirby, Chapter 7, this volume). Biological
control utilizes natural enemies, such as
arthropods, including copepods and Toxo-
rhynchites (see Howard, Chapter 2, this volume),
fi sh (see Chandra et al ., Chapter 3, this volume),
fungi (see Stevenson et al ., Chapter 5, this
volume) and biological toxins, Bacillus
thuringiensis israelensis , Bti, and Bacillus
sphaericus , Bs (see Cameron et al ., Chapter 10,

All disease control programmes need to be
specifi c to disease epidemiology and vector
ecology and behaviour to reduce their vectorial
capacity in local settings. Often, environmental
and biological control methods are not
universally applicable, and their ei cacy in
reducing disease transmission depends on how
well the intervention is matched to the vector's
specifi c ecological characteristics, which may
include breeding site preferences, dispersal
distance, feeding preferences (e.g. type of host,
time of feeding, location of feeding) and the level
of insecticide resistance (WHO, 2012a).
Misidentifi cation of species can thus lead to the
targeting of non-vector species with subsequent
failure of control programmes. For example in
Vietnam, Anopheles varuna , a zoophagic
mosquito species that does not vector malaria
was identifi ed as Anopheles minimus . This led to
intense ef orts to eliminate An . minimus rather
than the actual predominant malaria vector
present ( Anopheles dirus ), which exhibits
dif erent behaviours and requires dif erent
control interventions (Van Bortel et al ., 2001).
Additionally, environmental conditions, such as
temperature, humidity and rainfall may also
af ect particular interventions, and therefore
their ef ects on disease transmission.