Title: Effectiveness and sustainability of a source reduction strategy embedded in a routine vector control programme for prevention of dengue fever outbreak in the Ratnapura district, Sri Lanka Authors: N.G.S. Panditharathne 1, 2, K.B.Kannangara 1, Kensuke Goto 2, Satoshi Kaneko 2, 3 Authors’ Affiliations: 1 Ministry of health, Sri Lanka, 2 Department of eco-epidemiology, Institute of Tropical Medicine, Nagasaki University, Japan 3 Graduate School of International Health Development, Nagasaki University, Japan Background: At present, endemic dengue is a major public health problem in Sri Lanka. To assess the effectiveness of a community-based house-to-house larval source reduction campaign embedded in the routine laval controls strategy, we analysed the data from the official intervention of source reduction and dengue surveillance data between 2010 and 2012 in a district of Sri Lanka. Methods: According to the dwelling coverage percentage of the larval source reduction campaign, 575 Grama Niladari Divisions (GND) were categorized into four groups; group A (>75%), group B (50 - 74%), group C (25 - 49%) and group D (< 25%). By group, incidence rates (IR), incidence rate ratios (IRRs) and attribute risk percentages (AR %) of dengue fever was calculated to evaluate the effectiveness and sustainability of the campaign. Additionally, we calculated the cost for the campaign operation and avoidable costs for dengue patient management. Findings: Since the commencement of campaign, there was a minor outbreak in 2011 and a major one in 2012. Both outbreaks were observed only in lower campaign coverage groups and no outbreak was observed in group A area. IRs of group B, C, D areas were about three or four times higher in the major outbreak year of 2012 compared with that of group A and all of them were statistically significant. In group B, C & D study areas, 60 to 70% (total of 2456) of cases may have been avoided by the clean-up program, which is at least equivalent to US$ 159,645 in hospital admission cost. The initial cost of cleaning, programme embedding and subsequent maintenance cost in the study area was estimated at US$139,651 and US$ 88,999, respectively. Interpretation: Because 70% of maintenance clean-up cost would be recovered by revenue from recycling of the materials collected by the campaign and considerable avoidable cost of dengue patients, the maintenance of the clean-up activities would be sustainable.

1. EFFECTIVENESS AND SUSTAINABILITY OF A SOURCE
REDUCTION STRATEGY EMBEDDED IN A ROUTINE VECTOR
CONTROL PROGRAMME FOR PREVENTION OF DENGUE
FEVER OUTBREAK IN SRI LANKA
N.G.S. PANDITHARATHNE 1, 2, K.B.KANNANGARA 1, KENSUKE GOTO 2, SATOSHI KANEKO 2, 3
1）MINISTRY OF HEALTH, SRI LANKA; 2）DEPARTMENT OF ECO-EPIDEMIOLOGY, INSTITUTE OF TROPICAL MEDICINE, NAGASAKI UNIVERSITY, JAPAN;
3）GRADUATE SCHOOL OF INTERNATIONAL HEALTH DEVELOPMENT, NAGASAKI UNIVERSITY, JAPAN
Introduction
Areas in Group A
Figure 1. Map of Sri Lanka
Incidence per 10,000
50 100 150
0
Incidence per 10,000
50 100 150
0
ja
01
n2
01
1
01
jul2
01
1
01
jan
20
12
01
jul2
01
2
01
jan
20
13
01
jul2
01
0
01
jan
20
11
01
Areas in Group C
ju
01
jul2
01
1
01
jan
20
12
01
jul2
01
2
01
jan
20
13
Incidence per 10,000
50 100 150
0
Areas in Group D
Incidence per 10,000
50 100 150
0
Endemic dengue is a major public health problem at present in Sri
Lanka. Endemic dengue is a major public health problem at present
in Sri Lanka. In 2012, 44,456 cases were reported and dengue
infection once primarily in urban areas has spread to peri-urban and
rural areas. During the chikungunya outbreak of 2008, a district wide
entomological survey in the Ratnapura district figure 1, was
undertaken and it identified Aedes albopictus as the predominant
mosquito in the district. A Breteau index (BI), the number of
containers containing mosquito larvae per 100 households inspected,
recorded over 90 , which has a significantly high risk of chikungunya
or dengue transmission because the cut-off value of BI for
transmission is reported 4 or 5. The district wide entomological
survey in 2008, implicated 60% of larva positive containers as
“containers with water that are not used or that are discarded”, in
other words, thrown away or improperly stored artificial containers
such as plastic receptacles, broken and empty glassware, tins,
coconut shells and clay pots. The other 40% were named as natural
sites. The behaviour change in Sri Lankan context is to contain the
throw away culture of both biodegradable and non-biodegradable
discards in the domestic environment. Communication, education
and social mobilization, should complement efforts to adopting
more effective ways to engage the general public and other key
stakeholders for effectiveness of source reduction campaigns, and
targeted mosquito control measures. The programme in Sri Lanka
has failed to achieve an effective sustainable model with community
connectivity. We postulated that a community refuse collection
targeting household container discards, embedded in the routine
house-to-house visits by Public Health Inspectors (PHI) for vector
surveillance could prevent an outbreak of dengue. This study aims to
evaluate the effectiveness and efficiency of this model from 2010 to
2012 and the level of integration into the routine programme in
Ratnapura district, Sri Lanka.
Areas in Group B
l20
10
0
n
1ja
20
11
ju
01
l20
11
0
n
1ja
20
12
ju
01
l20
12
0
n
1ja
20
13
ja
01
n2
01
0
ja
01
n2
01
1
ja
01
n2
01
2
ja
01
n2
01
3
Figure 2. Distribution of monthly dengue fever incidence rates according to the cleanup proportion group among 575 Grama Niladari Divisions (GND)
(Grouping was done by the dwelling coverage percentage of the larval source reduction campaign;
Group A: >75%; group B: 50 - 74%; group C: 25 - 49%; group D: < 25% at the end of year 2010.)
The GNDs that have achieved an estimated > 75% household
coverage was groupednto category A, 74 - 50% coverage was
grouped into category B, > 25 - 49% coverage was grouped into
category C, < 25% coverage was grouped into category D. The annual
cluster incidence rate for 2011 & 2012 was summarised to observe
the clustering of cases under respective categories figure 2.
Coverage increase was estimated linearly and the estimated
coverage was used for categorization of cleaning coverage; 10 %
degrade per year was assumed after the end of year 2010 in areas
that discontinued the intervention.
Results
The IRR for the areas of less than 75% coverage of dwellings (Group
B, C, D) compared with area A (well cleaned area) showed a
significant increase in Group D area even in non-epidemic year of
dengue of 2011. In 2012, which was an epidemic year for dengue
fever, the risks for group B, C, D areas increased to 2.5 to 3.8 times
higher than group A area Table 1. AFs for group B, C, D areas ranged
from 59.7% to 73.9%, which indicated that that more than half
dengue cases were probably infected due to low cleaning level in the
areas. The preventable numbers of new cases were estimated at 190
of 319 cases in group B area, 569 of 775 cases and 1697 of 2296
cases in groups C & D areas in 2012. In total, 2456 cases could be
prevented in 2012 if group B, C and D areas were cleaned up as
group A area.
Table 1. Incidence rate ratio (IRR), attributable risk (AR), attributable fraction (AF) and preventable
number of dengue cases by high coverage of the source reduction activities in 2011 and 2012
Ratnapura is one of Sri Lanka’s administrative districts with high
rainfall and an average temperature between 30 C and 32C. The
estimated district population is approximately 1.1 million. The
district is further divided into health administrative divisions or
health units. The health units are further subdivided into smaller
geographically defined sub units that comprise an average of 2500
persons. These units are called Grama Niladari Divisions (GND) and
575 GNDs were the units of analysis. The district wide intervention
was carried out over a 15 month period from October 2009 to
December 2010 in 18 public health administrative units. We adopted
the following community intervention steps;
1) Dengue and its vector control
messages were delivered using
a public address system.
2) The householders were
advised to collect all the
discarded recyclable material in
their home premises and hand
it over to the town council
tractor.
3) Public Health Inspector of the
area and the town council
personnel making personal
visits to inspect premises.
4) Sorting & storage of
containers in the sorting centre
of the town council.
The data on house to house container removal days were obtained
by a weekly activity return furnished by the health units.
Kahawatta and Kolonna health units (Area A) continued the
intervention throughout year 2011 and 2012, on a routine basis
embedded in their dengue control activities.
Data Analysis
We considered a GND as a population cluster. The primary outcome
was category specific cluster incidence. We calculated incidence rate
ratios (IRRs) after clustering the GNDs to four categories based on
percentage coverage of dwellings in a GND (cluster). We considered a
GND as a population cluster.
59
74
102,750
7.20
38
68
105,050
6.47
0.90
0.64 - 1.27
Group C
108
174
223,712
7.78
1.08
370
626
650,152
9.63
1.34
Total
575
942
1081664
8.71
Group A
37
63
68,355
9.22
Group B
2012
Populati
on
Group D
2011
Dengue
cases
Incidenc
e per
10,000
Group B
Methods
No.
of
GND
Group A
Year
Area
group
categor
y
60
319
139,445
22.88
2.48
1.89 - 3.31
13.66
59.7%
190.5
Group C
108
775
223,712
34.64
3.76
2.91 - 4.94
25.43
73.4%
568.8
Group D
370
2296
650,152
35.31
3.83
2.98 - 5.00
26.10
73.9%
1696.8
Total
575
3453
1081664
31.92
Incidence
rate ratio
(IRR)
Attributab
le fraction
(AF)
Preventabl
e number
of dengue
cases
-0.73
-11.3%
-
0.82 - 1.44
0.58
7.4%
12.9
1.05 - 1.73
2.43
25.2%
157.8
95%
confidence
intervals
Attribut
able risk
(AR) per
10,000
reference
170.6
reference
2456.1
Note: Attributable risk (AR): (incidence rate of Group B, C, D) minus (incidence rate of Group A);
Attributable fraction (AF): AR divided by (incidence rate of Group B, C, D), which means
percentage of dengue cases in group B, C, and D that can be attributed to the lower coverage of
source reduction of mosquito larva.
Discussion
2,456 cases may have been have been avoided in 2012, in group B, C
and D which is about 12,280.4 patient days. Hence, a cost of SLR
21,071155.7 (USD 159,890) could have been avoided. We estimated
that mobilisation of a tractor per day for container from the local
council will cost only SLR 1,672.90 (USD12.7). This is well within the
capacity of all municipal councils. Furthermore, 70% of the
investment is recoverable by sale of collected material. Two of the
poorest local councils in the district (Area A) continued to provide
resources for the programme in 2011, 2012 which yielded a rich
public health dividend. Sri Lanka's public health infrastructure
provides for routine premises inspection and vector surveillance by
PHI and small teams of entomological assistants. Waste collection
embedded in the routine surveillance program of these teams,
needs to continue until the throw away culture of residents is
replaced by a segregation and storage culture at a domestic level.
The return passage of recyclable house waste to collecting centres of
the local councils is feasible. These activities in an enabling socio
political environment may provide a long term sustainable solution
to prevent epidemic dengue in Sri Lanka.
Acknowledgements
Authors thank the Sabaragamuwa provincial council and the central environmental
authority of Sri Lanka for strengthening the recalling capacity of the local councils. The
intervention was fully funded by the dengue control unit of the ministry of health, Sri
Lanka. The paper was prepared partly as a fulfilment of board certification
requirement of Community Medicine, MD part III training programme of the Post
graduate Institute of Medicine, University of Colombo, Sri Lanka.
Correspondence to: N.G.S Panditharathne, sujee1963@yahoo.com