Nigel Perkins

Managing Hendra riskManaging Hendra risk

AusVet Animal Health Services

Thoroughbred Breeders Queensland Association

Gatton

25 October 2009

Hendra incidentsLocation Horse PeopleMackay August 1994 2 1 (died 1995)Hendra September 1994 20 2 (1 died)Cairns January 1999 1Cairns October 2004 1 1Townsville December 2004 1Peachester June 2006 1Murwillumbah, NSW October 2006 1Peachester June 2007 1Clifton Beach (Cairns) July 2007 1Redlands June 2008 5 2 (1 died)Proserpine July 2008 3Cawarral July 2009 4 1 (died)Bowen August 2009 2

Date

Hendra virus in horses

Underlying effects on cells is via virus damaging endothelial cells

Clinical signs may then depend on which organs are most severely affected first (resp vs GIT vs neurological etc)

Signs likely to be variable & non-specific, esp early Hendra is rare and most cases that show signs

consistent with Hendra will NOT be cases Tomorrow's case may not look like priors It seems unlikely that we will be able to better pick

Hendra cases earlier in the future

Exposure risk Hendra virus is present in fluids & tissues in

infected horses• blood, saliva, nose/mouth, urine/faeces, tissues• Virus is shed from late incubation and through clinical stages

to death• Virus shedding/secretion maximal around the time of death

Splash/droplet risk and not aerosol

Risk depends on:• horse factors: stage of infection, localisation of virus, amnt

being shed…• What procedures are being done, level of PPE & biosecurity

Viral shedding Amount of virus shed by the horse

time

Infection Clinical signs DEATHoccurs first appear

Incubation period

Previous human cases & exposures

1994: Hendra virus was unknown• no precautions taken against Hendra

2004 (Cairns)• post mortem, Hendra not suspected• Vet later developed signs & tested positive• Horse not suspected until after Vet tested positive

2008 (Redlands)• Vet & Vet nurse infected• Horses being treated, examined, handled etc prior

to Hendra being suspected

Previous human cases & exposures

2008 Proserpine• Vet suspected Hendra when client reported deterioration & death of

the horse

• Vet called DPI and received instructions – used PPE & restricted necropsy

• Horse positive & no human infection

2009 Cawarral• Vet infected while dealing with a sick horse without suspecting

Hendra at the time

2009 (Bowen)• Vet took precautions at first visit to a suspect horse (Sept) – Hendra

• Then an earlier sick horse that had died the month before also tested positive

Other possible human exposures

• Redlands- 2 people infected- Many more people potentially at risk of

exposure through interacting with Hendra horses before or after the horses died

• Proserpine- horse & property owners

• Cawarral- property owner, staff, private vets

Possible exposure pathways for people

1. Horse that is severely ill or dead with signs consistent with Hendra• Staff/Vet concerned about Hendra

• Take precautions before approaching the horse

2. Horse presents with non-specific signs (mild, severe or sudden death)• Hendra is not suspected when Staff first approach horse

• Risk of exposure depends on activities/procedures

3. Horse that is apparently healthy yet is incubating Hendra• Staff/Vet involvement for other reasons

• Exposure risk much more variable & generally lower

Redlands

Proserpine

Cawarral

Bowen

QPIFHorse with fatal disease InvolvementRecovered horseHuman case

X XX XX

X XX

X XX X

X X

XX >70% of all cases occurred

prior to QPIF involvement

What happens when QPIFget involved?

QPIF generally involved once a Hendra positive test has been obtained

Risk management generally improves dramatically• Quarantine declared• Horse movement stopped or controlled• In contact animals tested• Biosecurity measures implemented: entry/exit, PPE,

disinfection, decontamination, restricted horse interaction• QH involved for human risk management & testing

Different risk periodsBEFORE Hendra is diagnosed

• Horse showing signs• May or may not be Hendra• To date, owners/vets have

been poor at taking effective precautions• little or no PPE

• Likelihood of Hendra is LOW• Risk of exposure if Hendra is

present is HIGHER• All human cases to date have

occurred in this scenario

AFTER Hendra is diagnosed

• Hendra test positive• QPIF involved

• quarantine, PPE, …• Likelihood of Hendra being

present is HIGH• Risk of exposure is LOW

because of biosecurity measures

• no human cases have occurred in this scenario

Major risk management issues for owners/staff

Prior to confirmation of Hendra in a horse• QPIF not involved • Major period of risk for staff/owners & vets• Need to develop plans to manage exposure risk for day-to-

day work with horses

After confirmation of at least one Hendra case on your property• QPIF involved, quarantine declared• Shared responsibilities:

- QPIF working on Hendra testing & euthanasia of positives- Farm staff still responsible for day-to-day activities including care &

welfare of horses for reasons other than Hendra monitoring/testing- Farm staff & PVP may be involved in taking samples/observations

Managing exposure risk given what we know now

Everyone who contacts a horse is bearing some risk – shared responsibility

People involved in more invasive procedures (vets, vet nurses, dentists, …) bear higher risk because of the activities & associated contact with potentially infectious material

How can we assess risk? Picking horses that have higher or lower risk

• horses that we think have Hendra virus would be at high risk

• Horses that we think don’t have Hendra virus would be at low risk

BUT

Horses that are infected with Hendra virus• show variable & often vague clinical signs that

could be due to other conditions and in fact are more likely to be due to other conditions (fever, off feed, depression, colicy, respiratory, neurological, …)

• AND, can shed Hendra virus before they show any clinical signs of illness

Procedures-based risk

Activities or procedures with higher associated risk

• exposure to blood, urine, nasal/oral secretions, internal organs, …

• Biosecurity: hygiene, PPE, disinfection, …

Activities associated with lower risk• lameness, physical exam, …• Reduced level of biosecurity• Focus on personal hygiene

Workplace Health and Safety

Need to be aware of responsibilities under state legislation

• to employees• to people coming onto the property to do

work (vets)• others

Risk management plans Training Equipment (PPE)

Risk management

Develop a risk-based approach to horse practice

Risk management has to be implemented prior to the time when Hendra might be suspected

Rapid tests are not a solution to initial veterinary risk management

Depends more on identifying:• activities or procedures with associated risk• horse history & signalment

Risk management Very low risk

• healthy horses & simple interaction (no contact with biological fluids)

• risk management based on person hygiene

Low to moderate risk• healthy horses & human interaction with some risk of contact with

biological fluids

• PPE (barrier protection) & personal hygiene

Moderate & higher risk• sick horse showing variable signs

• PPE (barrier protection) & personal hygiene & procedures based risk assessment

• restrict people who are involved

• get veterinary help

Risk on a confirmed property

Day to day tasks and health & welfare care continues Add Hendra monitoring & full PPE and entry/exit procedures Minimise contact with horses Movements/flow from low risk first to high risk last Cant move horses very much if at all How much time & what procedures can be safely done in full

PPE? How to manage non-Hendra health needs (foalings, injuries,

…) How to manage staff fatigue, rosters, get sufficient labour etc Provision of training and a framework for making decisions

Complexities of managing risk

Concepts seem rational Practical difficulties seem immense

• if hendra is listed as a differential then DPI vet must be notified. What quarantine/response measures should be imposed while waiting for a test result?

• how do we manage all the ongoing cases – cut legs, foalings, injuries, colics etc & try to manage Hendra risk?

• what are the ramifications for farm day-to-day management?

Future Simple PPE & biosecurity that can be used routinely Awareness campaigns for all stakeholders Risk planning facilitated & aided by industry bodies &

implemented by every horse operator Training in PPE & biosecurity for those that need it Work with QPIF (DPI) & other stakeholders to manage the

notification & response alerts Research to address issues that will help manage risk

• understanding spillover events & how to reduce risk• behavioural research on adoption of change• Post-exposure treatment• testing: test availability, speed• vaccine• others