Arboviruses Preventing Mosquito-borne Disease in Victoria 2016-2017 Summer preparedness November 2016
Arboviruses
Preventing Mosquito-borne Disease in Victoria 2016-2017
Summer preparedness
November 2016
Mosquitoes in Victoria
Range of endemic species
• 275 species
• Few bite humans or are ‘vectors’ for human disease
Not known to be exotic mosquitoes (e.g. Aedes. Aegypti –
yellow fever)
Abundance measured through trapping and reports
• Significant increase post-floods
• Around 30K trapped in recent flooding
• Around 15K trapped in total last season
Mosquito-borne diseases overall
Mosquitoes are linked to:
• Nuisance / reduced amenity (bites >>allergy) particularly
in wetland and bushland habitats
• Transmission of rare but potentially dangerous mosquito-
borne diseases
• Murray Valley Encephalitis virus
• Kunjin Virus
• Transmission of uncommon but potentially debilitating
mosquito-borne diseases
• Ross River virus
• Barmah Forest virus
The basics: relevant diseases
Which diseases are we most concerned about this season?
Flaviviruses (look like the Yellow fever virus or ‘flavus’ – Latin for yellow)
• Murray Valley Encephalitis virus (MVEV)
• Kunjin virus (West Nile Virus Kunjin-strain)
Alphaviruses (small, spherical viruses)
• Ross River Virus (RRV)
• Barmah Forest Virus (BFV)
Why?
• MVEV is extremely rare but the consequences of illness can be severe
• RRV & BFV are comparatively mild illnesses, but can affect large numbers of people
and cause protracted illness (4-6 months)
• All mosquito-borne diseases are preventable
Murray Valley Encephalitis Virus / MVE
Epidemiology
Endemic in north of WA and Top End of NT by waterbirds
Primary vector thought to be Culex annulisrostris
Reservoir probably waterbirds
Infected waterbirds into flood affected areas - ↑risk
The illness
Rare disease - last Victorian case in 1974
Can affect people of all ages
Around 1/150-1000 infected get symptoms, mostly severe
– Fever and headache, 7-28 days after exposure
– Encephalitis / meningitis (brain infection, swelling, damage)
– Risk of permanent neurological damage or sequelae (60%)
– Case fatality rate 10-30% (20% in 1974)
The risk of human cases infection is higher than in previous
years, but remains very low in absolute terms (‘flooding is
probably necessary, but not sufficient’)
What happened during last
flood event?
Increased Culex spp. vector and flooding
MVEV was detected in horses and
sentinel chickens
16 cases in humans across Australia –
increase and re-emergence
None identified in Victoria
3 cases died (19%)
Ross River Virus / RRV
Epidemiology
Endemic in Victoria
Wildlife reservoir - primarily kangaroos
Primary vectors: (but 40 species can carry it)
Culex annulisrostris, Aedes camptorynchus
The illness
Seasonal – peak seen in Feb, Mar each year
Notifiable Group B disease - normally around 200 cases/year
Can affect people of all ages – predominately adults
Usually mild, after 3-21 days resulting in:
– Joint inflammation and pain
– Fatigue and muscle aches
– Body rash
But symptoms can persist or recur over ~4-6 months or longer
(up to a year, probably providing lifelong immunity)
(BFV is similar to RRV, slightly milder, much fewer cases)
What happened during last
flood event?
RRV cases increased 7-fold
~1300 cases across Victoria
High notification rates in north-west
Some inland areas severely affected
(Buloke, Hindmarsh, Horsham)
– See map next slide
Ross River Virus – widely found, low rates
Ross River Virus Notification by LGA (2010/2011)
5 December 2016
Arbovirus Risk in Loddon Mallee region
Arbovirus disease risk
Variable risk across region
Many parts flood affected
MVEV detected in humans during last outbreak in 1974
• Buloke, Campaspe, Greater Bendigo, Mildura
Consistently high RRV notification rates
• Buloke, Campaspe, Gannawarra, Loddon, Mildura,
Swan Hill
High mosquito abundance observed now and during last
major flooding event
• Campaspe (current field observations)
• Gannawarra, Mildura, Swan Hill (adult trapping)
What happened during last
flood event in 2016?
MVEV was detected in horses and
sentinel chickens
Extremely high RRV rates in:
• Buloke (480 cases per 100,000)
• Mildura (470 cases per 100,000)
• Loddon (340 cases per 100,000)
• Swan Hill (300 cases per 100,000)
Comparatively lower rates in Greater
Bendigo and Campaspe
Floods in Victoria in 2016
September flood event:
• Recent rain and flooding → ideal conditions for mosquito breeding
• An increase in mosquitoes may increase the risk of mosquito-borne
diseases
• Mosquito-borne diseases are typically found around inland waterways
and coastal regions
DHHS response
• Activation of the Beat the Bite campaign
• Early trigger of surveillance and controls in funded councils
• For Loddon Mallee - Campaspe, Gannawarra, Mildura, Swan Hill
• Inter-agency coordination
• State Mosquito Working Group of the State Emergency Management Team
• State Health Incident Management Team led by DHHS
• Objectives of the response:
• Where is the risk, how large is it and how will it change? (MVE, RRV, nuisance)
• What enhancements are needed in human and vector surveillance?
• What enhancements in vector controls?
• What do our communities need to know, consider and do?
• What do agencies, departments and health professionals need?
5 December 2016
How are we monitoring risk?
Surveillance
Human
• ‘Notifications’ to Department (DHHS)
• Opportunistic laboratory surveillance
Vertebrate
• Sentinel chickens – warning system
• Neurological illness in horses
Mosquitoes
• Adult mosquito surveillance
• Laval surveillance
Climatic conditions
Why sentinel chickens?
Are susceptible to MVEV
Can be located at sites where mosquito
abundance is high
Are easily handled and bled (weekly
from 27 October – flaviviruses)
Can show antibodies as early as 4 days
post infection
The assumption:
If mosquitoes are biting and infecting
chickens (or horses), the theoretical risk
to humans is present
Controls – Integrated Mosquito Management
Victorian Arbovirus Disease Control Program
• Nine rural/regional funded councils – November-April
• Surveillance via DEDJTR for RRV/BFV
Areas for targeted increased activity
• Surveillance – sentinel chicken flocks, horses, humans
• Source reduction – best - containers, person-made structures (breeding sites)
• Larval control – main option - larvicides (registered, safe, non-toxic to
water/species, drinkable, used in potable water tanks)
• Pupal control – rarer/older – low-mammalian toxicity agents
• Adult mosquito control – adulticides - fogging or contact spraying, can affect
other insects / bees
5 December 2016
Overview of the Beat the Bite campaign
An integrated campaign designed to support awareness of the
ways to reduce the risk of being bitten by mosquitoes.
Includes social media, print and web-based information with all
resources available at:
www.betterhealth.vic.gov.au/campaigns/beat-the-bite
Beat the Bite – Social Media
Share the Better Health Channel’s social media posts:
• Facebook - https://www.facebook.com/BetterHealthChannel
• Twitter -https://twitter.com/betterhealthgov
#beatthebite
5 December 2016
Resources
Order from the warehouse and share:
http://ideas.health.vic.gov.au/resources.asp
How you can help Beat the Bite
• Connect through social media
• Link to our website
• www.betterhealth.vic.gov.au/beat-the-bite
• Agencies can talk to councils about promoting Beat the Bite
using social media kits they were sent
• Councils can actively promote the materials and social media
resources
• Everyone can download the resources on BHC and share with
your stakeholders.