Transcript An Assessment of the Impact of Climate Features on Dengue

An Assessment of the Impact of
Climate Features on Dengue Fever
and its Vectors in Five Caribbean
Countries (AIACC Project)
By
S C Rawlins PhD,
Emeritus Scientist
c/o Caribbean Epidemiology Centre,
Trinidad
Introduction
 In
the last two decades there has
been an unprecedented increase in
the occurrence and severity of
dengue fever (DF) in Caribbean
countries.
 Any tool useful to predicting
outbreaks and implementing
enhanced prevention strategies –
adaptation – would be most
welcome.
Introduction contd.
Dengue in the Caribbean and El Nino years and
year after an El Nino - El Nino +1
El Nino
El Nino + 1
Caribbean Countries
Introduction Contd.
Already, we have examined the impact of
climate change features especially
warming conditions on retrospective
dengue fever data in the Caribbean
region.
 We have shown some association in the
increased occurrence of DF and warming
periods in some Caribbean Epidemiology
Centre (CAREC) Member Countries (CMCs)

Caribbean countries
Fig. 2 Seasonal variation of dengue Fever Cases for 3 Epidem ic Years
in Selected CAREC Mem ber Countries
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Barbados 1997
Jamaica 1998
St Kitts/Nevis 2001
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Prospective Studies, 2002-2004
. In this present study we are examining
prospectively the occurrence of DF and
population features of the vector with
varying climate features such as
temperature and precipitation.
 Here, we are examining the patterns of
reported dengue fever cases in the
Caribbean region – mainly CMCs with a
population of just over 6 - 7 millions – to
demonstrate any climate-related patterns
of disease presentation over 2002 - 2004

Design and Methods
Data on reported monthly dengue fever
(DF) cases, vector – Aedes aegypti –
indices, and climatic indicators were
collected prospectively for a 12 month
period beginning early 2003 in 5
Caribbean countries
 Jamaica, Trinidad and Tobago (T&T),
Barbados, St Vincent and the Grenadines
(SVG) and St Kitts/Nevis (SKN).
 Data were analyzed by ANOVA for
evidence of climate impact on DF cases
and vector indices.

St Vincent Results
 SVG
data showed minor fluctuations
of vector breteau (BIs) and house
indices (HIs) with precipitation
 Dryer periods coincided with low
vector HIs of 9-22%. In wet periods,
both indices were higher – HIs (1772%) and BIs (31-55).
 Temperature varied slightly (2332˚C) throughout the year.
St Kitts/Nevis Results
 SKN
vector data showed a bimodal
pattern with peaks of HIs and BIs in
May-June and October-December,
the latter associated with significant
precipitation.
 Mean monthly temperatures only
varied between 26 -29˚C (Fig. 4).
Trinidad and Tobago
T&T data for 2002 and 2003 showed
distinct dry and wet seasonal patterns
 In 2002 dry periods (January-May), there
were low BIs (21– 29), and mean monthly
DF cases of 290.4.
 Increases in BIs (32-44), (P=0.000) and
mean monthly DF cases (695/month)
coincided with the wetter period (June –
December).
 Temperature varied slightly 22-25˚C (min)
to 31 -33˚C (max) for the period.

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Rainfall (mm)
Dengue cases
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Temperature and Breteau index
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Rainfall, Temperature, Breteau index and Dengue cases, Trinidad
(2002-2004.
Conclusions 1
 Patterns
from SKN, SVG and T&T
data discerned a correlation of
seasonal effect on BIs and in T&T on
DF transmission
 . Temperature variations did not
seem to be significant, but may have
affected the onset of precipitation
and in turn, vector production, an
increase in indices and DF cases
Conclusions 2
 The
data confirm the usefulness of
recognizing the wet season as a risk
factor for DF transmission in the
region
 Utilising this knowledge for
preparation of early warning systems
for DF prevention will be vital