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.