WASH Cluster – Emergency Training
VC
Vector Control
Module 2B
Mosquito borne
diseases
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Behaviour of mosquitoes
Genus
Breeding site
Disease and distribution
Anopeline mosquito
Biting period : NIGHT
Non polluted water: Edges
of rivers, swamps, tanks,
rice fields, saltwater
without wave action,
Malaria : Tropical and sub-tropical
Filariasis : Asia and Africa
Aedes mosquito
Biting period : DAY
Small water containers:
Cans, jars, gutters
Yellow fever : Africa and Americas
Dengue : Africa and Americas, Asia
Filariasis : Pacific
Culex mosquito
Biting period : NIGHT
Any dirty water: Waste
water ditches, latrines,
septic pits,
Filariasis : Most tropical areas
Encephalitis virus: worldwide
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Mosquito Life Cycle
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Lymphatic Filariasis
• Transmission by
mosquitoes
– Anophelenes and
Culicines
• Filarial worms, Mainly
Wuchereria bancrofti,
– Also Brugia malayi or B. timori
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Lymphatic Filariasis Endemic Areas
Endemic in 83 countries
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Guerrant et al 2006,
5
Tropical Infectious Diseases 2nd Ed.
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Clinical Disease
• Hydrocoele
• Elephantiasis
• Tropical Pulmonary
Eosinophilia
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Chichungunya
• 'Chikungunya' 'that which bends up'
Swahili
• 1st documented in 1952 to 1953 in Africa
• Alphavirus of family Togaviridae
• Primary vectors : Aedes albopictus or aegypti.
• 2005 to 2006 - 266,000 cases = 35.0% of the
population in Reunion, Madagascar, Mauritius and
Seychelles.
• 2006 –2007 Outbreaks in India, Sri Lanka & Italy
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Chikungunya Global Distribution
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Outbreaks have increased
in scale and frequency in
recent years.
Distribution follows
dengue as it can be
transmitted same vectors.
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Insecticide Treated Nets (ITN)
Also help to
reduce fleas
and mites in
the bed
clothing and
mattress
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Environmental Control
• The elimination of mosquito breeding sites.
• In most circumstances, difficult because of lack
of staff, the extent of the breeding sites and
cost.
• Some breeding sites may also be the only
available water.
• Malaria mosquitoes can fly several km.
• Localised (household) grass cutting and bush
cleaning not useful for malaria control.
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Time of biting:
Number caught (no.) and Number positive for sporozoites (+)
1800-2200h
Species
An. gambiae
2200-0200h
0200-0600h
Source
Tanganyika (Gilles, 1957)
no.
+
248
9
743
20
606
8
no.
+
5900
295
13000
1040
10850
2061
Burkina Faso (Robert 1991)
An. gambiae
no.
91
1269
1831
Sierra Leone (Bockarie
1996)
An . gambiae
no.
+
23
2
189
14
211
9
Tanzania (Maxwell 1997)
An. funestus
no.
+
31
0
232
7
86
2
An. gambiae
/An. funestus
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Mosquito prefer pregnant women
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Issue for Control #1
• Different insect vectors may peak in different
seasons. The malaria vector may be
present during the dry season when other
mosquito populations are low.
It is important to use LLITN throughout the
year if you want to control malaria.
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Longevity (daily survivorship)
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Issue for Control #2
• Mosquitoes don’t live very long – most will die
before they can transmit malaria. A mosquito
will rest on the wall after it feeds.
Therefore Indoor residual spraying (IRS) works It
kills the mosquito sometime within the
incubation period
Spraying your own house, but not the others in
the community will not protect your family
from malaria.
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Issue for Control #3
• At 25º it takes 12 days before a mosquito can
transmit malaria – most will die before then.
Below 19º malaria can not be transmitted.
• Malaria falls off in winter because of the
cooler temperature, but can happen before
the rains as long as there is ground water
• IRS works by killing the mosquito sometime
within the incubation period
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VBD Control Myths
1.
2.
3.
4.
5.
All mosquitoes are the same
Cutting grass and maize is useful
Filling in puddles around house is useful
Clearing garbage is useful for malaria control
Wearing long sleeve shirts and pants
protects
6. Spraying individual houses protects the
family
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VBD Control Facts
• Sleeping under an LL ITN every night provides good
protection against malaria, some filariasis and
Lieshmaniasis
• IRS also protects equally well against malaria if >85% of
houses in a community are sprayed. It may also be
effective against mosquito borne Rift valley fever
• Larval control works well for dengue fever and to a lesser
extend also malaria (i.e. temporary floods etc) but all
breeding sites within the flight range of the vector need to
be eliminated
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