© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009 HUME...

© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009

Queensland Primary Industries and Fisheries

HUME FIELD Biosecurity Queensland, Australia

Epidemiology, surveillance and Epidemiology, surveillance and control control

of Hendra virusof Hendra virus



o

background..

• no evidence of infection in horses prior to 1994.

• 13 known spillover events.• low infectivity, but high

case fatality rate.• human cases attributed to

close contact with infected horses.



known spillovers..Mackay 2 horses & one human August 1994

Brisbane (Hendra) 20 horses & two humans September 1994

Cairns (Trinity Beach) 1 horse January 1999

Cairns (Gordonvale) 1 horse* & one human October 2004

Townsville 1 horse December 2004

Peachester 1 horse June 2006

Murwillimbah 1 horse October 2006

Peachester 1 horse June 2007

Cairns (Clifton Beach) 1 horse July 2007

Brisbane (Redlands) 5 horses* & two humans June 2008

Proserpine

Cawarral

Bowen

3 horses*

4 horses & one human

2 horses

July 2008

July 2009

Aug 2009



o

o Mackay 1994

o Cairns 1999, 2004, 2007

spatial pattern..

o Townsville 2004

o Peachester 2006, 2007 Brisbane 1994, 2008o Murwillumbah 2006

o Proserpine 2008

o Cawarral 2009

Bowen 2009 o



..temporal pattern1994 1,1

b 1995 0e 1996 0t 1997 0w 1998 0e 1999 1e 2000 0n 2001 0

2002 0y 2003 0e 2004 1,1a 2005 0r 2006 1,1

2007 1,12008 1,12009 1,1

w jan 1i feb 0t mar 0h apr 0i may 0n jun 1,1,1

jul 1,1,1y aug 1,1e sep 1a oct 1,1r nov 1

dec 0



natural reservoir..

• fruit bats identified as the natural host in 1996.

• antibodies in all 4 species.

• antibodies across the geographic range.

• no attributed clinical disease in flying foxes.

• antibodies in archived samples.

Grey-headed flying fox

hume field

photo credit??



..HeV antibody prevalence

Key:Horizontal hatching P. alectoVertical hatching P. poliocephalusSolid black P. conspicillatusBroken line P. scapulatus (southern inland limit)

Map adapted from Hall and Richards (2000). Data from Field (2005)

51% (95% CI 48-54)

27% (95% CI 17-39)

31% (95% CI 19-46)

29% (95% CI 21-39)

P. alecto 13/13P. scap 13/13P. polio 5/13P. consp 3/13



risk of spillover..

probability of spillover from any given colony depends on

• the proportion of susceptible flying foxes,• the colony size,• the presence of infection..

plus • the number and density of horses,• the number and density of flying foxes,• management of the horses,• the virus strain/virus dose/route of infection?

potentialviral load

effective contact



modes of transmission..

plausible modes of direct bat-horse transmission:

• ingestion of partially eaten fruit.• ingestion of ‘spats’.• ingestion of urine-contaminated

pasture/feed.• licking/sniffing foetal tissues.



indirect transmission via an intermediate host?

improbable because• negative screening of non-bat species.• phylogenetic clustering of bat and horse virus

sequence.• temporal overlap between equine cases

and detection in flying foxes.• direct horse-to-horse

and horse-to-human transmission via infected body fluids.

• biological plausibility of direct transmission.

Photo: Photo:

Ian TembyIan Temby

Peachester (SEQ) 2007

Proserpine (FNQ) 2008Cairns (FNQ) 2007

FNQ 2008

Redlands (SEQ) 2008

SEQ 2009

Hendra (SEQ) 1994

for nucleotide 1500 to 2240 of the genome (carboxy terminal of the Nucleoprotein and the intergenic region) using Mega 4.0 (Neighbor-joining, p distances). Bat sequence in red italics. [Ina Smith, AAHL]

Hendra virus

phylogenetic analysis..



infection dynamics in bats..

antibody prevalence studies

bat level variables• age p=0.0028

• season p=0.0025

[Andrew Breed, 2005.]



infection dynamics in bats..

• UC Davis• US NSF funding

[Raina Plowright, 2002.]



limiting infection in horses..

• awareness.• exposure risk minimisation strategies.• early consideration of Hendra virus.• appropriate management/PPE in suspects.• rapid rule-out/-in.• quarantine of identified case properties.



limiting infection in horses..

• remains a rare infection– 2 in 200,000 horses pa.– 13 in 5 million horse-years at risk.

• likelihood vs consequence.



research directions..

• infection dynamics in bats.• drivers for virus emergence from bats.• modes of transmission. • exposure risk management.• early detection methods.• therapeutics.



drivers for emergence..

• emergence or awareness?• the more you look, the more you find?

• St. George (1989) suggested the possibility of a rabies-like virus in Australian bats in 1989.. ‘might not become evident unless active surveillance of bats was undertaken, or man or a domestic animal became infected’.



changed bat population dynamics..

in recent decades, • decreased total population.• altered distribution.• change in the number and permanency of

roosts.• altered frequency of contact.

Plowright, Foley, Field et al 2009 (submitted)[Raina Plowright, 2002.]



increasing urbanization..

• major shift in the distribution of flying foxes into urban areas.

• perception of plague proportions.

Plowright, Foley, Field et al 2009 (submitted)



changed risk of spill-over..

in urban areas,more flying foxesplus higher contact

ratesmeans larger

outbreaks

more infectious individuals,a greater total viral load, and a greater probability of exposure and infection

=




in summary..

• landscape changes resulted in changed population dynamics that promoted emergence and spillover.

• further landscape changes and climate change may further de-stabilize the system.




If you suspect Hendra virus, please contact Biosecurity Queensland immediately on 13 25 23 or contact the Emergency Disease

Watch Hotline on 1800 675 888.

OverviewHendra virus overview

Get a copy of the reportDownload: 'Independent review of Hendra virus cases' (PDF, 480 kB)

For veterinariansUpdates from the Chief Veterinary Officer:2009, April 3 | 2008, August 19 | 2008, August 8 | 2008, July 28 Guidelines for veterinarians handling potential Hendra virus infection in horses Version 3, April 2009 Submitting samples for analysis Safe use of personal protective equipment (PPE)

For communitiesHendra virus: important information for horse owners (PDF, 262 kB)Download your copy today. Fact sheet: important community information (PDF, 71 kB)(including advice to horse owners) Fact sheet: Hendra virus infection (from Queensland Health)

ResearchInitial experimental characterisation of HeV (Redland Bay 2008) infection in horses (PDF, 222 kB)Report authored by Deborah Middleton, CSIRO AAHL Research into Hendra virus: the story so farResearch participants, progress, challenges and current work. Hendra virus: the initial researchThis information sheet reports on the emergence of Hendra virus in horses and on research into reservoir hosts and transmission studies in fruit bats, horses and cats. Scientific papersLink to the PubMed website (published research papers). Search for "Hendra virus".

QPIF Hendra virus webpage ..



acknowledgements..

• Queensland Primary Industries & Fisheries/Biosecurity Queensland.

• CSIRO Australian Animal Health Laboratory.• Australian Biosecurity CRC for Emerging

Infectious Diseases.• Australian Dept. of Agriculture, Forestry &

Fisheries.• US Wildlife Trust/Consortium for Conservation

Medicine.

© The State of Queensland, Department of Employment, Economic Development and Innovation, 2009 HUME...

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