Download - Dengue vector surveillance final
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Norma DC JosonEntomologist III
Department of Health
DENGUE VECTOR DENGUE VECTOR SURVEILLANCESURVEILLANCE
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What is Vector Surveillance
an on-going systematic process of collection analysis interpretation
dissemination of information
about the vector for appropriate action.
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MOSQUITO VECTORS
Aedes
CulexAnopheles
Mansonia
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General :To obtain information about the
mosquito for proper action.
Specific :•To establish presence/absence of the vector.•To determine major mosquito breeding sites.•To monitor high risk areas.•To monitor seasonal population fluctuations.•To monitor mosquito population w/c will serve as a warning for an impending outbreak. •To recommend immediate prevention & control measures when necessary. •To assess impact of interventions.
Objectives
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What life stage of the mosquito is used in vector surveillance?
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A. ADULT MOSQUITO COLLECTION• collection of adult mosquito as
they land on a human bait
B. PUPAL SURVEY• collection of pupae from the breeding sites
C. LARVAL SURVEY• collection of mosquito larvae from the
breeding sites
D. OVITRAP/LARVITRAP • collection of mosquito eggs using an
oviposition trap where adult mosquitoes lay their eggs
• if the eggs emerged into larval stage before collection, the method is called Larvitrap
Methods of Vector Surveys
Adult collection
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A. PREPARATORY PHASE
1. Organize & mobilize a Dengue Watch Team/Task Force/Brigade.
2. Prepare a spot map of the barangay.3. Prepare entomological supplies needed4. Group the team into 4 to cover 25
houses per group.5. Coordinate with local officials prior to
the activity.
Strategies / Activities
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B. FIELD COLLECTION
1. Inspect all houses w/in 300m radius of index house
2. Inspect all water-holding containers• artificial : drums, tires, tin cans, bottles,
flower vase, roof gutter, coconut shell• natural : leaf axils, tree holes, bamboo
stumps 3. Label as to kind, location & type of container4. Indicate containers w/o larvae in the survey
form5. Collect adult mosquitoes, if any.6. Conduct on the spot health education to the
household/owner.
Strategies / Activities
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What are the common breeding sites of Aedes mosquitoes?
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C. LABORATORY
1. Prepare laboratory materials, equipment & other supplies
2. Mount & identify the larvae under the microscope
3. Identify adult mosquitoes, if any, using a stereoscope or magnifying lens
4. Determine larval indices.5. Analyze & interpret findings.
Strategies / Activities
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Strategies / ActivitiesRAPID MOUNTING OF MOSQUITO LARVAE
1. Kill the larvae in 600C hot water.
2. Transfer larvae into 70% alcohol solution.
3. Transfer larvae into 95% alcohol solution.
4. Clear larvae using xylene.5. Put larvae on clean slides,
wipe excess water w/ filter or tissue paper.
6. Mount the larvae using a mounting medium.
7. Examine specimen under the microscope.
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A. ADULT MOSQUITO
ADULT BITING INDEX (ABI) or HUMAN LANDING RATE (HBR) used to determine adult mosquito
density through human bareleg catches
ABI = no. of Aedes sp. collected x 60
no. of human baits
Interpretation :
ADULT DENSITY >2/human/hr = high risk
<2/human/hr = low risk
Mosquito Indices
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B. PUPAL SURVEY
PUPAL INDEX used to calculate adult mosquito
production used for special assessment &
studies, not for routine surveys
PI = no. of Aedes sp. collected x 100%no. of houses inspected
Mosquito Indices
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B. LARVAE
B.1 LARVAL INDICES – from larval surveysHouse IndexContainer IndexBreteau Index
B.2 LARVITRAP INDEX (LI) – from trapsLI = no. of traps (indoor/outdoor) (+) for
Aedes sp x 100 total no. of traps set
Interpretation : LI (rural) >20% & LI (urban) >10% =
dengue sensitive areas
Mosquito Indices
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C. EGG – survey is conducted in areas where Aedes density is low; useful for early detection of new Aedes infestations
OVITRAP DENSITY INDEX (ODI) – from traps
ODI = no. of Aedes eggs x 100
no. of positive traps
Mosquito Indices
BLACK TIN CAN PADDLE (Lawanit)
¾ full of H2O
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A. HOUSE/PREMISE INDEX (HI)HI = no. of houses (+) for Aedes sp. x
100% no. of houses inspected
B. CONTAINER INDEX (CI)CI = no. of containers (+) for Aedes sp. X 100%
no. of containers inspected
C. BRETEAU INDEX (BI)BI = no. of positive containers x 100 total no. of houses inspected
Larval SurveyCOMPUTATION OF RESULTS
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A. Vector presence/absence - primary/secondary vectors,
geographic distribution larval indices - high/low indices based on WHO
figure, mosquito density vs. cases, area dengue sensitive or not, color code, etc.
breeding sites - kind of container (i.e. drum, tire, etc.), type (artificial/natural), location (indoor/outdoor), size (large/small), most common container, etc.
B. Community socio-economic factors & behavioral practices,
lifestyle, beliefs, presence/absence of legislations on dengue prevention & control, etc.
Larval SurveyANALYSIS OF FINDINGS
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Priority 1 - localities where an outbreak of DF/DHF had occurred
Priority 2 - localities w/ high larval indicesHI >5% and/or BI >20
Priority 3 - localities w/ relatively low larval indices
HI <5% and/or BI <20
Priority 4 - localities where there are no dengue cases and low Aedes densities.
Priotization of Areas
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w/in 24 hrs of the 1st case from an outbreak locality
following an outbreak based on priority classification of the locality
high risk areas (Priority 1 & 2) = monthly/ quarterly in 100% of houseslow risk areas (Priority 3 & 4) = monthly/ quarterly in at least 20% of houses
before and after interventions
when there is suspect of insecticide resistance
When to Conduct Larval Surveys
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COLOR CODES :Dengue Vector Surveillance
CODE INTERPRETATION
WHAT TO DO
WHITE HOUSE INDEX is<5% and/orBRETEAU INDEX is <20
•Continue IEC campaign on prevention & control•Continue clean-up activities•Continue monthly entomological survey by local health authorities•Maintain the Code WHITE in the community
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COLOR CODES :Dengue Vector Surveillance
CODE INTERPRETATION
WHAT TO DO
RED HOUSE INDEX is >5% and/orBRETEAU INDEX is >20
•Intensify IEC campaign on prevention & control•Mobilize residents of affected barangay to start clean-up campaign w/ the help of the Dengue Brigade•Continue monthly entomological survey by local health authorities•Improve environmental sanitation•Start community vigilance; search for more areas w/ HI >5% and/or BI >20 •Apply larvicide.
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Who will benefit from the Information
Program Planners & ManagersField Health WorkersLocal Government Units Community Researchers MediaOther Sectors of SocietyFunding agencies
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Thank you!!!