Stephen L. Doggett
Senior Hospital Scientist
Department of Medical Entomology, ICPMR,
Westmead Hospital, Westmead NSW 2145
Overview

Factors driving arbovirus activity

Methods of surveillance
 NSW Arbovirus Program

Enhanced surveillance!

Information dissemination

How to use surveillance data

Case study: MVEV in 2008

A little challenge…
Factors Driving Arbovirus Activity

Temperature drives mosquito activity

Water drives mosquito abundance

Water – rain, tides, humidity

Distribution of vectors & reservoir hosts

Host/herd immunity
Reservoirs & humans
 Low immunity – pot. larger outbreaks


Virus & virus strain

Various human behaviours
Arbovirus Surveillance in NSW

Predictive

Weather patterns

Vector populations

Virus infected mosquitoes

(Computer modeling)
Transmission




Sentinel animals (MVEV & KUNV)
Humans
Program must be tailored to the virus, the
virus ecology and the human population
NSW Virogeographic Regions
RRV, MVEV, KUNV
RRV,
BFV
Aedes vigilax
Culex annulirostris
NSW Surveillance Locations
Weather Patterns

Rainfall
 Level of mosquito abundance

Climatic indicators (El Nino/SO)
 Long term mosquito/arbovirus activity
 MVEV hypotheses: Forbes, Nichols
Weather - MVE models
Forbes’ hypothesis
Oct-Dec
2014
Jan-Mar
2015
Oct-Dec
2015
Darling River
0.80
0.65
0.48
Lachlan/
Murrumbidgee/
Murray Rivers
0.97
1.05
0.29
Northern Rivers
0.94
0.67
0.33
North Lake Eyre
system
1.07
0.67
0.11
Catchment Basin
Jan-Mar
2016
Nicholls’
Hypothesis
Southern
Oscillation
Weather Patterns

Rainfall
 Level of mosquito abundance

Climatic indicators (El Nino/SO)
 Long term mosquito/arbovirus activity
 MVEV hypotheses: Forbes, Nichols, Bennett

Tidal
 Level of saltmarsh mosquito abundance
2.5
2.3
2.1
6000
5000
4000
1.9
3000
1.7
2000
1.5
1000
1.3
0
Mosquito Numbers
W
k1
W
k2
W
k3
W
k4
W
k5
W
k6
W
k7
W
k8
W
k
W -9
k1
W 0
k1
W 1
k1
W 2
k1
W 3
k1
W 4
k1
W 5
k1
W 6
k1
W 7
k1
W 8
k1
W 9
k2
W 0
k2
W 1
k2
W 2
k2
W 3
k24
Tide height (m)
Tide & Mosq. Populations
8000
2.9
7000
2.7
Tide & Mosq. Populations
Weather Patterns

Rainfall
 Level of mosquito abundance

Climatic indicators (El Nino/SO)
 Long term mosquito/arbovirus activity
 MVEV hypotheses: Forbes, Nichols, Bennett

Tidal
 Level of saltmarsh mosquito abundance

Advantage: Cheap!

Disadvantage: Least sensitive method
Vector Populations

Determine species composition

Examine seasonal abundance

Arbovirus detection

Quarantine

Long term




Mosquito population monitoring
Arbovirus monitoring
Changes in vector distribution
Control Programs
EVS Trap
(Encephalitis Vector
Surveillance Trap)
Adult monitoring
Vector Population Monitoring
1200
1000
800
600
400
200
0
Nov
Dec
Jan
Feb
Mar
Apr
Virus Isolation from Vectors

Provide information on ‘normal’ activity
(long term)

Early indication of virus activity/type
identify potential outbreaks

Identify new vectors

Monitor new virus incursions

Traditionally via ‘cell culture’
Virus Identification Times
Honey-Baited Cards
Honey-Baited Cards

FTA cards coated with honey
 Placed into mosquito trap
 Mosquitoes spit virus
 Cards tested via molecular tests

Advantages
Virus Identification Times
Honey-Baited Cards

FTA cards coated with honey
 Placed into mosquito trap
 Mosquitoes spit virus
 Cards tested via molecular tests

Advantages
 Rapid: 1-2 days
 Sensitivity: > cell culture, > animals
 Labour savings!!!
But can we
do even
better?
Sugar Bait Stations
Lark Coffey, UC Davis
Advantages/Disadvantages

Mosquito Population Monitoring
Highly significant relationship between
mosquito populations & human disease
 Field equipment cheap & portable
 Traps can be placed in viral ‘hot spots’
 Laboratory labour intensive


Virus Isolation
 Good early indicator of epidemic activity
 Need to process many mosquitoes
(1 virus in 2-4,000 mosquitoes)
Human Cases

Advantages
Most sensitive but…
 Provide epidemiological information
 Provide information on ‘risk’, e.g.
geographic exposure, time of exposure
determine when health warnings are needed
 Modify existing surveillance programs


Disadvantage

Too late for health interventions
Information Dissemination

NSW Arbovirus Surveillance Web Site
 http://medent.usyd.edu.au/arbovirus

Weekly reports

Annual reports

Special reports
So how can the data be used?

Base mosquito warnings on the data



The timing & degree
Use the data in media campaigns
It’s mosquito season:
Take Precautions!

Mosquito numbers 8x normal
Increased Disease Risk!

Virus detected in mosquitoes
Disease Outbreak Feared!
Case Study
MVEV 2008
MVEV 2008: Background

Forbes: not fulfilled

Nichols: not fulfilled

Summer rainfall: >average

Low irrigation allocation

Mosquito numbers: low

MVEV activity unlikely
MVEV Activity 2008
26/Feb/08
5/Feb/08
18/Feb/08
3/Mar/08
24/Mar/08
2/Feb/08
4/Feb/08
Low Pressure Cell Mid-Jan 2008
Dr Andrew Read, DPI, Menangle
Health Actions
Media releases/Fact Sheets/Radio/TV
 EDs, GPs contacted
 Telephone Hotline (1800 064 400)
 Weekly teleconferences
 Extended chicken/mosquito season
 Established further flocks & traps
 Opportunistic testing
 Dept. Agriculture opportunistic testing

Surveillance Requires

Appropriate number of sites

Intelligently located

Multitude of methods

Continuous

Timely sample analysis & response

Review locations/techniques
 Must
consider vector!!!
Aedes albopictus
Asian Tiger Mosquito (ATM)
Honey-Baited Cards

FTA cards coated with honey
 Placed into mosquito trap
 Mosquitoes spit virus
 Cards tested via molecular tests

Advantages
 Rapid: 1-2 days
FTA vs CC
Viral
Assay
BFV
RRV
EHV
KOKV
STRV
Total
FTA
12
68
2
0
0
82
CC
6
17
No. traps = 903
3
1
1
28