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Novel dengue surveillance and control strategies
developed at UWI, St Augustine, Trinidad
Dave D. Chadee
Department of Life Sciences, Faculty of Science and
Technology, University of the West Indies, St.
Augustine, Trinidad, West Indies.
Presented at the UWI Research Expo 2013 at the St Augustine Campus, UWI, Trinidad, W.I 2nd-3rd October 2013.
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World Distribution
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Epidemiology Factors
Mosquitoes Dengue virus Environment Humans
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Dengue transmission within the
Caribbean Region• Dengue is caused by any of 4 different serotypes of
the arbovirus (Den 1,2,3,& 4)
• An incubation period of 2-8 days after an infective bite by the Aedes aegypti mosquito.
• The disease usually begins with onset of fever, headaches followed by chills, retro-orbicular pain, photophobia, backache, severe muscle ache and joint pain
• Maculopapular rash, lymph node enlargement, petechiae and haemorrhagic manifestations like epistaxis and gastrointestinal bleeding (WHO 1997)
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Introduction
• In 2013 the global
incidence of dengue
fever was found to be
underestimated by 3
times
• The iceberg effect-
instead of 100 million
cases 390 million cases*
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Dengue situation Globally and in the Caribbean
RegionBackground
• Over 3 billion people live in areas where dengue is endemic (latitude 45oN-35oS)- dengue belt
• Dengue causes more illness and death than any other arbovirus disease in humans
• So each year over 390 million cases of dengue and several thousands cases of DHF occur- 93 M asym.
• DHF is the leading cause of hospitalization and death among children in South East Asia
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Reported and Confirmed Cases of Dengue, Trinidad , 1980-2011
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The UWI approach and Rationale for
Current Strategies in Trinidad
This program was developed based on the
scientific approach with respect to :
• (1) the mosquito: genetics (Benedict and
Robinson 2003), ecology (Chadee 2010),
behavior (Chadee 2010) and vulnerable life
stages (Christophers 1960);
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UWI rationale
• (2) the anthropogenic factors affecting human population size, housing patterns, behavior, culture and socio-economic conditions (Chadee 2004) and ;
• (3) knowledge of various aspects of the environment (biotic and abiotic factors) which foster the development of the vector (Gubler and Kuno 1997, Chadee 2012)and enhance disease transmission.
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Roads as a barrier to mosquito
movement and dengue transmission
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Results: The frequency of DHF cases to
different road classes were:
0% (1st Class roads),
7% (2nd Class roads),
32% (3rd class roads),
57% (4th Class roads) and
4% (5th Class road).
The data clearly demonstrated that both class 3 and
class 4 roads account for 89% of nearby dengue
cases. URBAN PLANNING??
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Shows the distance of DHF cases (home addresses) and their proximity to road
classes in Trinidad, West Indies (1998).
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Cardinal Points Surveillance
Cardinal points approach- Quick, Less Labour
intensive, Cheap, More Sensitive and Specific
Casa segura – safe house- IT Curtains
Key Containers
Key Premises
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Cardinal Points Surveillance method –micro-
investigate (Chadee et al. 2007)
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10.00-12.00
Atypical blood feeding12.00-15.00
Adults resting
indoors and
outdoors
12.00
Noon
n
0.00
Midnight
15.00
6am-9am
Oviposition
Blood feeding
Sugar feeding
Copulating
6.00
18.00-21.00
Atypical blood feeding
21.00-05.00
Adult resting
indoors and
outdoors
16.00-18.00
Oviposition
Blood feeding
Sugar feeding
Copulating
Aedes aegypti Circadian Rhythm
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Physiological Process Period of inactivity (h)
References
Post adult emergence 24 Bowen, 1991
Post insemination 12 Fuchs & Kang, 1978
Post blood feeding 12 Klowden & Brazil, 1994
Inhibition of host seeking 24 Klowden, 1994
Post oviposition 12 Chadee, 2012
Periods of quiescence among Aedes aegypti females.
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Females Males
Room No. collected
% Range No (%) of houses with
females
No. collected
% Range No (%) of houses with
males
Bedroom 968 81.9 0-32 159 (31.8) 493 57.4 0-29 130 (26.0)
Living room
101 8.7 0-10 93 (18.6) 201 23.4 0-25 71 (14.2)
Kitchen 71 6.0 0-6 40 (8.0) 93 10.8 0-22 32 (6.4)
Bathroom 22 1.8 0-5 40 (8.0) 55 6.4 0-19 29 (5.8)
Other rooms
19 1.6 0-12 12 (2.4) 17 2.0 0-13 10 (2.0)
Total 1181 100 858 100
Table 1 Adult Aedes aegypti collected from different rooms in houses from St Augustine, Trinidad
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Two types of effective spraying for
Dengue
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Curtains
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Curtains (Manufacturers????)
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Use of the Sticky traps (Chadee and
Ritchie 2011)
An alternative adult mosquito collection
method:
• Collects adult Ae. aegypti mosquitoes and
eggs
• Less labour intensive
• Less expensive
• More sensitive in collecting adults
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A. Sticky Ovitrap – for Adult Mosquitoes
Attach panels to the bucket with a folding clip (Fig. 1.
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Aedes aegypti collections from sticky traps in
Trinidad (Chadee and Ritchie, 2011)
Locations in Trinidad Sticky trapsAdults Immatures
Double sticky trapsAdults Immatures
St. Augustine (urban) 1,480 5,900 2,286 7,777
Tamana (rural) 220 1,592 316 1,652
Total 1,700 7,492 2,602 9,421
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Home made traps?????