|
Aedes aegypti is the main vector of DEN/DHF
which has been responsible for all urban epidemics of this disease. Ae. albopictus
is also mainly involved in dengue transmission in South-East Asia and the Western Pacific regions.
Ae. aegypti
has a close association with man and it is a highly domestic species with
more than 90 per cent resting on no sprayable
surface in the house. Therefore, indoor residual treatment of houses is not
generally recommended. Chemical control using insecticide generally has very
little impact for long-term control of DEN/DHF. The use of insecticide should
be discouraged for long-term prevention and control. However, experiments on
the control of Ae. aegypti in several
countries in SEA Region has shown that thorough treatment at an interval of
1-2 weeks with portable fogging applicators together with truck-mounted
applicators yielded controlof Ae. aegypti. Space spray with
insecticide should be considered as an epidemic contingency measure. Total
coverage should be targeted for, however attention
should be focused inside the house and in the places where high vector
densities have been recorded. Space spray should be implemented in a compact
community and it should be within the radius of 400-500 metres
from the affected house.
Equipment
used for ULV/thermal fogging are listed below:
|
Equipment
|
Possible Daily Coverage
|
|
Vehicle-mounted cold fogger, e.g. LECO
|
225 ha
|
|
Vehicle-mounted thermal fogger, e.g. Dyna-Fog
|
150 ha
|
|
Back-pack ULV mist blower, e.g. Fontan
|
30 ha
|
|
Hand-carried thermal fogger e.g. Swing Fog
|
5 ha
|
|
Hand-carried indoor ULV aerosol generator,e.g.
Mity Moe
|
5 ha or 250 houses
|
Suitable
insecticides for thermal and cold aerosols are indicated in the table.
Insecticides suitable as cold aerosol sprays and for thermal fogs
for mosquito control
|
Insecticde
|
Chemical
|
Dosage of ai.b (g/ha)
|
Toxicity: oral LD50ofai.b for
rats(mg/kg body weight)
|
|
Cold
|
Thermal
|
|
Chlorpyrifos
|
OP
|
10-40
|
150-200P
|
135
|
|
Cyfluthrin
|
PY
|
1-2
|
-
|
500
|
|
Ypermethrin
|
PY
|
1-3
|
-
|
7180
|
|
Cyphenothrin
|
PY
|
2-5
|
-
|
2250-2640
|
|
Deltamethrin
|
PY
|
0.5-1.0
|
-
|
>2940c,d
|
|
D-phenothrin
|
PY
|
5-10
|
-
|
>10,000
|
|
Etofenprox
|
PY
|
10-20
|
10-20
|
>40,000
|
|
Fenitrothion
|
OP
|
250-300
|
270-300
|
503
|
|
Fenthion
|
OP
|
150
|
-
|
330d
|
|
Malathion
|
OP
|
112-693
|
500-600
|
>4000
|
|
Naled
|
OP
|
56-280
|
-
|
430
|
|
Permethrine
|
PY
|
5-10
|
-
|
>4000c,d
|
|
Pirimiphos-Methyl
|
OP
|
230-330
|
180-200
|
2018
|
|
Propoxur
|
C
|
100
|
-
|
95
|
|
Zeta-Cypermethrin
|
PY
|
1-3
|
-
|
86
|
PY = Synthetic pyrethroid, OP = organophosphorus,
and C= Carbamate
b ai.= active ingredient
c
Because of their low dermal toxicity and on the basis of experience with
their use, these products have been classified in the WHO Hazard
Classification in Class III, Table 5 (WHO/PCS/94.2).
d Dermal
toxicity
e Also
used in mixtures with knock-down agents or synergists
|
