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!!!