Strategies for Controlling Animal Influenza and Implications for Human Health

Les SimsAsia Pacific Veterinary Information

Servicesapvis@bigpond.net.au

Background

Animal influenza is not eradicable

Possible to eliminate certain strains of virus

- Equine influenza in Australia- H5N1 HPAI from most infected countries

Background

Available control measures for influenza in animals are well described

How and when applied, more complex Measures are used in combination Not always used appropriately Any measure applied inappropriately will

hamper control Control in animals usually reduces

exposure of humans to animal influenza viruses

Vaccination

Surveillance and disease reporting systems Underpin control programs In many countries remain weak

Mandatory reporting of infection is only required for some subtypes in selected species (e.g. H5/H7 in poultry - NAI).

No international obligation to report cases of swine influenza (unless novel disease/strain)

Surveillance and disease reporting Farmers usually have few incentives

to report animal influenza

They can face significant disadvantages if they do

Consequences of surveillance

Influenza viruses in animalsTwo broad ‘categories’ of animal

influenza viruses

- those that countries choose to live with (but still subject to controls at individual farm level)

- those they attempt to eliminate

Control measures

Measures applied depend on:

- the virus subtype (e.g. H5, H7 (NAI) viruses versus H9 in poultry);

- the species involved (e.g. chicken versus wild bird) - the country where infection occurs (e.g. Australia versus

Vietnam)

Leads to variations in the objectives of animal influenza control programs from place to place

Objectives of different parties

Public health practitioner perspective/objective

Minimise exposure of humans to animal

influenza viruses

Objectives of different partiesCommercial farmer perspective/objective

Control influenza until:

- it no longer has a significant effect on performance or profits

- farmers are sure they will retain key markets (including export markets)

Legitimate concerns about effects on sales Some influenza viruses are subject to state and

industry supported ‘eradication’ campaigns when they occur

Objectives of different partiesSmallholder/household producer

perspective

Low input systems for food security/income diversity

Some driven by poverty Influenza only considered a problem

if it causes severe losses (due to disease or to the control measures applied, including losses of markets)

Areas of concern – human health

1. The difficulties encountered in eliminating Influenza A(H5N1) viruses from poultry in countries where infection is endemic

- Risk to humans from influenza A(H5N1) will persist for at least the next 5 to 10 years

2003

1996

2003

2006

2007

Areas of concern - countries with endemic infection

Why have these countries remained endemically infected ?

Three main factors

i) Nature of the production and marketing systems

Reproduced from FAO/USAID Atlas of poultry production

ii) Quality of veterinary and animal production services

iii) Commitment from public and private sector to virus elimination (not just containment)

Areas of concern - countries with endemic infection

Areas of concern – human health

2. Large scale animal influenza vaccination programs

Need to balance benefits versus concerns Need to understand objectives of vaccination program

- effects of vaccination on antigenic characteristics of viruses

- autogenous vaccines (especially in pig production)

- effects of ‘silent’ infection (need for modified surveillance and reporting signals)

Need better(user friendly) vaccines

Areas of concern – human health

3. The trend towards larger industrialized production units

- Not a recommendation of international agencies for influenza control

- Farm workers as a bridge to communities- Potential for looser ties to government (in

house testing)- Potential for negative effects on poor

Areas of concern - trend towards larger units

50% increase in human population in next 40 years – predominantly urban

Pig and poultry production expected to increase dramatically

Will provide opportunities for emergence of novel influenza viruses

Areas of concern – human health

4. Globalization and increased trade in livestock products

- Most introductions of avian influenza by trade in live poultry probably occur across land borders

- Most international trade in live poultry is in day old chicks (virus not vertically transmitted)

“If a pig coughs in Mexico the world should know about it”

Moves to improve surveillance and early identification and containment of potential human pandemic influenza viruses are laudable

Likely to fall short of expectations

Could we have stopped the 2009 pandemic with early detection?

If the 2009 influenza A(H1N1) pandemic virus had been detected in pigs in January 2009 what measures would have been implemented?

Not the first North American-Eurasian reassortant pig virus

Few characteristics to suggest it would be readily transmissible between humans

Low probability that such a virus would be detected when it first emerged (i.e. before spreading to other sites)

Pre-emptive action

Clear criteria are needed on:- when action will be taken to

contain/eliminate newly emerged strains of interest in animals;

- the measures that will be used; and - the support that will be provided to

producers and countries affected by the measures.

Pre-emptive action

To improve success, actions proposed should not disadvantage transparent countries or alienate farming communities

Communities need to understand and see the benefits in making changes and of being involved in surveillance – no simple solution

Close associations between humans and animals is not restricted to developing countries

Thank you for your attention

Acknowledgements I have been privileged to work in Asia for the past

17 years. The observations and views in this presentation

are personal but developed while working for a number of organizations, including the Government of Hong Kong, FAO, the World Bank, IDRC and PATH.

I wish to thank my many colleagues globally, and especially in Hong Kong, Vietnam, Cambodia, Mainland China and Thailand, who have worked with me, shared their expertise and helped to shape my views on animal influenza.

I would like to thank the Influenza Options team for inviting me to speak at the conference.