MONTHLY REPORT ON DENGUE ENTOMOLOGICAL SURVEILLANCE A publication of the National Dengue Control Unit

Ministry of Health, Sri Lanka

National Dengue Control Unit-Ministry of Health, Sri Lanka Public Health Complex, 555/5, Elvitigala Mawatha, Narahenpita, Colombo 05.

Tel : +94(0)112368416 / 7 Fax: +94(0)11 2369893 Email: ndcu2010@yahoo.com

Web : http://www.dengue.health.gov.lk

Vol.02 Issue No 05 May 2015

Role of Entomological surveillance in

Dengue Control

Dengue fever (DF)/ Dengue Haemorrhagic fever

(DHF) is a mosquito borne viral disease which is

endemic in Sri Lanka. Entomology is defined as the

scientific study of insects, a branch of Zoology. Entomological surveillance is a scientific process to

understand the dynamics of the disease transmitting

vector.

Dengue is transmitted by female mosquitoes of

Aedes aegypti (Linnaeus) and Aedes albopictus

(Skuse). A.aegypti is the primary and the epidemic

causing vector of DF/DHF and it is a highly

domesticated and anthropophilic very efficient

vector mosquito while Aedes albopictus is the

secondary vector that is important in maintaining an

epidemic. The life cycle of the Aedes mosquito is as

follows (Fig 1.):

Fig 1- Life cycle of dengue mosquito

Life cycle consists of water stages i.e. eggs, pupa

and larvae and non-water stages i.e. adult mosquito.

Based on existing evidence, control of water stages

of the life cycle is cost effective. Therefore under

entomology surveillance more emphasis is given

for studying of water stages of life cycle of the

mosquito.

The objectives of vector surveillance are to

determine breeding sites, temporal and spatial

distribution, interventions that are used for dengue

vector control seasonal population fluctuations,

feeding and resting habits (vector bionomics/

behaviour), and effectiveness of vector control to

collect data for early warning and forecasting

dengue outbreaks / epidemics.

Dengue vector surveillance is carried out both at

sentinel sites, routine surveillance areas and spots

(spot checks).

Commonly used vector surveillance methods are

larval surveys (both larvae and pupae). Here, the

basic sampling unit is the house or premise. During

the survey, all potential dengue vector breeding

sites that are prevalent in and around the selected

houses/ premises should be examined for Aedes

larvae.

Once identification is completed, larval density

indices are calculated for A.aegypti and A.

albopictus separately, and combine for Aedes

aegypti and A.albopictus, in order to give the vector

density in the area. The indices, namely, Container

index (CI), House/premise index (HI) and Breteau

index (BI) are used to give the vector density.

High container index of a particular type of

containers indicates the importance of that

container type as a dengue vector breeding site and

the vector control interventions need to be directed

to eliminate such types of containers immediately.

Cut-off points of larval density indices, container

types and the most productive container types also

need to be considered in dengue prevention and

control. In Sri Lanka, HI and BI (A.aegypti) >3 is

an indication for dengue transmission and

application of appropriate dengue vector

prevention/ control interventions.

Appropriate utilization of entomology surveillance

data would be helpful in successful control of

dengue by implementing targeted interventions.

Compiled by :Dr.Sinha De Silva

Contents Page

1. Role of Entomological surveillance in Dengue Control

2. Island wide Entomological Surveillance Summary -2014 April

3. Entomological Forecast

1

2

2

Comments and contributions for publication in the MRDES Sri Lanka are welcome. Prior approval should be obtained from the NDCU before publishing data in this publication.

MRDES Sri Lanka - Vol.02 Issue No 05 May 2015

Table 1: Dengue Entomological Surveillance - 2015 April Summary

Pro

vin

ce

Dis

tric

t

No. of Premises Percentage Positivity by type of containers

Insp

ecte

d

Fo

un

d

po

siti

ve

%

Po

siti

ve

Dis

card

ed

rece

pta

cles

Wat

er s

tora

ge

con

tain

ers

Cem

ent

tan

ks

Co

ncr

ete

slab

Nat

ura

l

A/C

& R

P

& O

Wel

ls

Oth

ers

WP

Colombo 1,377 165 11.98 35% 13% 1% 1% 3% 0% 14% 0% 33%

Colombo MC 225 15 6.67 9% 3% 0% 0% 0% 0% 0% 0% 88%

Gampaha 610 124 20.33 31% 18% 0% 0% 9% 0% 1% 0% 41%

Kalutara 1,817 181 9.96 61% 7% 0% 0% 11% 0% 2% 0% 19%

NWP Kurunegala 1,393 41 2.94 33% 33% 6% 0% 0% 0% 8% 0% 20%

Puttalam 150 23 15.33 54% 11% 0% 0% 13% 0% 3% 0% 19%

UP Monaragala 3,037 194 6.39 66% 15% 0% 0% 0% 0% 1% 0% 18%

Badulla 641 52 8.11 35% 14% 9% 11% 3% 3% 2% 0% 23%

CP

Matale 871 50 5.74 33% 0% 41% 0% 0% 7% 4% 0% 15%

NuwaraEliya * * * * * * * * * * * *

Kandy 1,354 67 4.95 27% 17% 17% 0% 2% 8% 0% 0% 29%

EP

Batticaloa 2,080 108 5.19 14% 35% 6% 0% 5% 4% 0% 8% 28%

Kalmunai 860 14 1.63 42% 16% 27% 0% 0% 0% 5% 5% 5%

Trincomalee 155 4 2.58 57% 14% 0% 0% 29% 0% 0% 0% 0%

Ampara 300 6 2.00 16% 67% 17% 0% 0% 0% 0% 0% 0%

NCP Anuradhapura 650 72 11.08 52% 1% 5% 0% 1% 0% 18% 0% 23%

Polonnaruwa 154 13 8.44 30% 15% 15% 0% 0% 5% 30% 0% 5%

SGP Kegalle 1,008 145 14.38 47% 17% 5% 0% 10% 4% 1% 0% 16%

Rathnapura 1,202 88 7.32 49% 11% 4% 0% 8% 4% 0% 0% 24%

SP

Galle 167 15 8.98 50% 9% 9% 0% 23% 0% 4% 0% 5%

Matara 300 33 11.00 53% 10% 3% 0% 3% 5% 8% 0% 18%

Hambantota 932 53 5.69 28% 10% 3% 0% 0% 5% 7% 0% 47%

NP

Jaffna 300 21 7.00 65% 12% 17% 0% 0% 0% 6% 0% 0%

Mannar 950 134 14.11 7% 88% 0% 0% 0% 0% 1% 0% 4%

Killinochchi 418 21 5.02 14% 0% 0% 0% 0% 0% 0% 0% 86%

Vavuniya 802 31 3.87 43% 27% 7% 0% 0% 0% 10% 0% 13%

Mullativu 439 58 13.21 21% 24% 17% 0% 0% 0% 0% 0% 38%

Sri Lanka 22,192 1,728 7.79 38% 18% 5% 0% 5% 2% 4% 0% 28%

Ad

dre

ss:

Director,

National Dengue Control Unit,

Public Health Complex,

555/5, Elvitigala Mawatha,

Colombo 05.

Address:

Key: This report is based on the weekly returns sent by Entomological Assistants (EAA) to N DCU. P & O- Ponds and Ornamentals; R –

Refrigerators ; * No data ; Others- Tyres, Roof gutters and other miscellaneous places (eg. Tube wells, Earth pipes, Water meters, etc)

Entomological Forecast of High-Risk Areas

RDHS MO(O)H

Colombo Kolonnawa,Moratuwa, Maharagama, Homagama

Kaluthara Horana, Aluthgama

Rathnapura Rathnapura Ps, Kuruwita

Gampaha Katana, Divulapitiya

Badulla Badulla MC

Matara Malimbada

Kandy Akurana

Kegalle Yatiyanthoya, Galigamuwa

Batticaloa Batticaloa

Kurunegala MC Kurunegala

NB:

Entomological

surveillance data for the

month of April 2015

done by MRI

entomology teams has

not received