dengue vector surveillance final
Post on 21-Aug-2014
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Norma DC JosonEntomologist III
Department of Health
DENGUE VECTOR DENGUE VECTOR SURVEILLANCESURVEILLANCE
What is Vector Surveillance
an on-going systematic process of collection analysis interpretation
dissemination of information
about the vector for appropriate action.
MOSQUITO VECTORS
Aedes
CulexAnopheles
Mansonia
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
What life stage of the mosquito is used in vector surveillance?
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
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
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
What are the common breeding sites of Aedes mosquitoes?
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
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.
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
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
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
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
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
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
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
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
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
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.
Who will benefit from the Information
Program Planners & ManagersField Health WorkersLocal Government Units Community Researchers MediaOther Sectors of SocietyFunding agencies
Thank you!!!
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