Minimising the Risk of Avian Influenza on Free-Range Farms

BACKGROUND

Influenza viruses belong to the family Orthomyxoviridae and they affect a wide variety of animal species, man and even marine mammals. The nomenclature of influenza viruses is subtyped based on the surface glycoproteins antigens, Haemagglutin (H) and Neuraminidase (N) where there are 16 subtypes of H and 9 subtypes of N. Most combinations of these subtypes have been identified in domestic and wild birds, particularly water fowl. The main reservoir of Avian Influenza (AI) viruses is water fowl. Influenza viruses have a high frequency of antigenic variation, that is a potential to mutate readily. This makes their control by vaccination difficult over time because of the need to continually produce new vaccines to accommodate for the emergence of new strains. This is in part why the Australian AI preparedness plan currently does not include a stored bank of an AI vaccine. The “Bird Flu” strain or H5N1 and the emerging strain in Asia of H7N9 have not been identified in Australia. The geographical isolation of Australia and the absence of any significant migratory flight pathways of the high risk family birds, called the Anatidae, (part of the order Anseriformes) which includes ducks, geese and swans, protect Australia from the incursion of these viruses.

For Australia though, the AI status has always been the same before and now after the “Bird Flu” scare. Wild water fowl in Australia, in particular ducks are endemically infected with a wide variety of subtypes of AI. Surveillance work undertaken in wild birds over many years provides evidence that there is the presence of AI antibodies in most species of wild ducks and in some there is also notably a high level of AI virus. This includes the H5 and H7 subtypes which in domestic chickens usually cause serious clinical disease. In water fowl AI is asymptomatic and the viruses are normally of the low pathogenic AI (LPAI) form. When these viruses affect chickens or turkeys, they usually become high pathogenic AI m(HPAI) with the outcome of significant production losses and mortality. Thus wild water fowl are a silent but ever present reservoir of AI with the potential to cause significant problems to the poultry industry in Australia.

Australia has formally recognised AI as a disease requiring stamping out and eradication with this first occurring in 1976 in Victoria. Since then we have had a number of outbreaks involving Victoria, Queensland and NSW. These outbreaks involved commercial layers and broiler breeders with in one case some ratites (emus) involved. The most recent outbreaks have originated in two free range layer farms in NSW with another asymptomatic identification in domestic ducks. There has also been two occurrences of AI in turkeys in NSW but caused by a H9 subtype AI. While this is not an AI strain covered by the Australian Emergency Animal Diseases Response Plan (EADRP) H9 AI viruses are recognised in some countries, and particularly those in the Middle East to become endemic and cause ongoing and significant production losses.

The Avian Influenza (AI) virus being an enveloped virus is not a particularly hardy virus and can be killed by all common disinfectants and even soapy water. Its persistence in the environment is limited although it can survive for extended periods in surface water.

Thus for the virus to spread from wild water fowl there is the need for a relatively close physical association or horizontal contact involving the fomites or faeces of the wild ducks contaminating the inputs such as drinking water of the commercial chickens.

In all cases of AI in Australia in commercial poultry there were identified or had to be fundamental failures in biosecurity. Are these avoidable when farming chicken under free range condition is the topic of this paper.

Minimising the Risk of Avian Influenza on Free-Range Farms - Image 1

WHAT IMPACT DO AI OUTBREAKS HAVE IN AUSTRALIA

Even despite the absence of H5N1 or “Bird Flu” in Australia the response to the concern (fear) of it causing a human pandemic created a substantial amount of costly preparedness for government and industry and had a spinoff of causing some temporary decline in the consumption of chicken meat, but surprisingly not eggs (although they are produced by chickens!). Concern was both in the public and human health authorities that commercial poultry could be the contaminating source of “Bird Flu” to the human population. Fortunately for the world human population the pandemic concerns about “Bird Flu” have diminished and public reaction has also declined. Prior to this the poultry industry sectors saw it necessary to have prepared a publicity campaign in the event of an H5N1 outbreak in Australian poultry, to hopefully prevent an aversion of the consumer away from poultry and poultry products.

Today the consumer is essentially desensitised to concerns about AI and despite the media response to recent AI outbreaks the key focus and concern was on the reduced table egg supply. The increased occurrence of the weekend breakfast at the local café has clearly shifted the concerns and priorities of the Australia middle class consumer.

What AI outbreaks do cause in Australia is significant financial loss both directly and through consequential losses to the affected producer. Coupled with this are the substantial costs that the government and various other bodies need to cover and also the levies that all sectors of the poultry industry have to pay under the EADRP cost sharing agreement.

The export sectors of live birds, hatching eggs and poultry products also suffer significant financial losses and often for extended periods of time during which markets can be permanently damaged. During these periods the various exporting industries often impose their frustrations on AQIS despite the later just applying the directives imposed by the importing countries.

The recent three outbreaks of AI in relatively close proximity to each other have created some questions from government and some industry sectors of how sustainable is the EADRP cost sharing agreement if we have further AI outbreaks. The government is under tight fiscal pressures and some sectors of the poultry industry, (for whom export markets are not significant) question the ongoing costs. Under membership of Animal Health Australia the various animal and poultry industry sectors have signed an agreement to implement best practice which includes sound biosecurity practices. It is questioned if the layer sector is achieving these requirements considering the repeat AI outbreaks in recent times.

The reality that retail and consumer pressures are moving production away from the more biosecure secure cage to free range systems does increase the risks of both EAD and endemic diseases but this cannot be used as an “excuse” because the outcome of an AI outbreak still result in the major negative impacts on the Australia poultry industry and exporters. If the domestic market struggles with supply and there is reoccurrence of AI outbreaks this could potentially create import pressures for the industry.

AUSTRALIA’S INTERNATIONAL STATUS

To be declared officially free of AI (which includes LPAI H5 and H7 and all HPAI) under the OIE requirements it is a requirement that the country undertakes both active surveillance and passive surveillance. Currently Australia does undertake quality passive surveillance where any suspicious mortalities or production drops are clinically observed these flocks are tested at government laboratories to exclude an EAD. Australia though does not undertake active surveillance which involves the strategic testing of clinically normal birds from a range of production systems and demographic areas. The poultry industry is concerned about the ongoing cost of such surveillance work and in some sectors where exports are not a major component they can see no value in such testing. For exporters this current situation of Australia not being classified AI free (for LPAI H5 and H7) does not significantly impact on exports these only being affected by HPAI outbreaks. During the “Bird Flu” scare there was some concern from the human health sector that active surveillance of commercial poultry was not occurring. The poultry industry argues that the incursion of LPAI into a commercial flock is relatively quickly followed by mutation into the HPAI form with the expression of serious clinical disease which is identified by surveillance. This comment does not apply to ducks which can asymptomatically carry LPAI. Active surveillance is also a point of time determination of the status of flocks and thus there is still the dependence on passive surveillance for the majority of the time. These are both valid industry points. The fact that Australian is also an island country adds that extra confidence of restricting the entry of exotic AI viruses.

Australian outbreaks of HPAI AI do significantly impact on the ability of the Australian genetic companies to export too many countries. This problem for these very high biosecure facilities has been overcome in such countries as the UK by the concept of compartmentalisation which effectively isolates the accredited company site from the affected countries disease outbreak status. Commercial poultry industry sectors have not supported the compartmentalisation of Australian hatching egg exporters because if similar reciprocal countries achieve such compartmentalisation status it would potentially allow imports into Australia. The latter is unlikely as all potential importing countries are positive for virulent infectious bursal disease (IBD), this being the major barrier for imports.

MINIMISING THE RISK OF AI INFECTION IN POULTRY

It is the responsibility of all the components of the poultry industry to undertake best practice activity to avoid the incursion of AI into their flocks, this is despite the size or alignment of the operation. Under the EADRP cost sharing agreement all producers and industry sectors are obligated to farm responsibly if they are to have access to compensation. Some comments from the smaller niche market free range sectors that the nature of their farming operations makes their birds “immune” to AI is without logic and scientific merit. Evidence of AI has been seen in flocks of all sizes and system types.

WILD WATER FOWL - WILD DUCKS

The primary focus on avoiding the incursion of AI into commercial poultry is the avoidance of contact between wild water fowl, their fomites or inputs contaminated by wild water fowl.

All primary (IP1) outbreaks of AI have invariably been associated with the observed or suspected horizontal contacts with wild water fowl.

Drinking and Cooling Water is the key critical point of control when sourced from surface water (dams, channels, reservoirs) and also captured rainwater which is commonly not considered by producers as a potential contaminated source. Despite the sanitation of surface water being recognised as the highest risk it is disappointing that the authors observe noncompliance in this area throughout all sectors of the industry. This could be the total absence of any sanitation system, chronically inoperable systems, poorly maintained and inconsistent operation, the failure to replenish the sanitiser and finally the absence of an ongoing and reliable monitoring system that verifies that the level of sanitiser is effective.

In other cases there are concerns about the effectiveness of sanitation systems because of the way they are facilitated where contact time is limited.

On some occasions scenarios are seen where drinking water is sanitised but the cooling water is not. Why the occurrence of poor water biosecurity is still common in the industry is multifactorial with the combination of lack of technical knowhow, concern about costs of equipment, complacency, lack of supervision, and the “it will not happen to me” syndrome.

The equipment, chemicals and know how is readily available for producers and there is no reason why all egg producers in Australia should not have quality and effective water sanitation systems. Details of the technical and facilitation aspects of water sanitation are available in the National Water Biosecurity Manual Poultry Production.

The use of medicators to supply medication and vaccines is also considered to be potentially problematic particularly with vaccination. There is often the anomaly that birds are vaccinated with chlorinated water that has not had the chlorine appropriately inactivated or the converse that the chlorination of water is discontinued during the vaccination process. Both approaches are unsatisfactory from the aspects of efficacious vaccination and the risk of using potentially contaminated water.

The ongoing incidence of Egg Drop Syndrome (EDS) in the layer industry confirms that biosecurity practices around water fowl and contamination are an industry concern. The epidemiology of EDS and its primary infection into a flock similarly also involves water fowl with the EDS being a more environmentally resistant virus compared to AI.

FREE RANGE ENVIRONMENT

The presence of surface water on or within the vicinity of free range areas provides an attractant for water fowl to aggregate and extend their range out into areas frequented by the layers. With the likely probability of some of these water fowl actively shedding AI virus the opportunity for cross contamination by faeces and fomites is high. This is not only direct contact but also the aerosol contact of AI contaminated fomites. There have been cases where poultry in controlled environment sheds have become AI positive as a consequence of ducks grazing around the perimeter of the shed. Paradoxically during times of drought having green grass in the range area is another attractant for ducks and other water fowl.

Where open bodies of water are in the vicinity of range areas they must not only be fenced off but also covered with netting or ribbons to impede the ability of the water fowl to alight on the dam. Ideally where such dams are not required they should be filled in. Producers with applications for new free range farms should endeavour to have planning permits that do not mandate the requirement for retention dams on site.

Earthworks and landscaping in the range area should ensure that after rain there are not persistent bodies of surface water. Even in the absence of surface water ducks can be observed within the vicinity of poultry sheds and within range areas. Initially attractants such as spilt feed should be cleaned up. Under summer conditions green grass around sheds will also attract grazing ducks.

Producers must use any aversion methods they can to deter water fowl from being in range areas or around sheds. The methods used here need to have an outcome that ensures the biosecurity of their operation and the minimalist intervention procedures that may be required are insignificant compared to the ramifications of an AI outbreak to the industry and country.

ANCILLARY BIOSECURITY

The use of foot baths and hand sanitation while providing only small percentile gains in maintaining biosecurity for free range operations do though provide a message to staff on the importance of biosecurity. This discipline encourages the thought process around all the general aspects of biosecurity. People entering a free range facility should still met the stand down time requirement between farms and also enter with clean clothes and footwear. On entering individual sheds a change of protective foot wear should occur.

The movement of equipment and disposables should also meet the standard biosecurity requirements of traceability and hygiene before entering the farm. There must be always the assumption that this material maybe contaminated particularly if the traceability information is not reliable.

BOUNDARY BIOSECURITY

Boundary biosecurity can be described as that biosecurity that is applied at the entrance point to a farm or site. Within the boundary confines of the property there are the normal endemic diseases present but the incursion of new endemic diseases or EAD animal diseases need to be brought onto the property past that boundary. This, other than through free flying birds (or vermin) as discussed above, can only occur by human intervention. The numerous horizontal contacts that occur are many and include:

live birds,
dead birds,
used litter and fresh litter,
people, including staff, contractors and suppliers,
feed,
eggs, egg filers and other poultry products,
feed, and
vehicles

All of these must be considered as possible vectors of AI onto the farm or farm site.

The spread of AI from IP1 to IP2 occurs because assumptions are made that the IP1 is free of any possible EAD. This logic is erroneous and why with some EAD outbreaks we see the spread of AI from IP1.

It is critical to appreciate that the shedding of virus will occur before overt clinical signs and in the case of LPAI these signs may be minimal for a week or more prior to virus the moving into adjacent flocks and manifesting as HPAI. It is possible on small holdings with single age flocks that the birds after exposure to AI may be free of significant clinical signs but still be shedding virus that can be transferred onto other sites by horizontal contacts.

The recognition of AI even with the expression of clinical disease can be delayed on sites historically chronically affected with fowl cholera and it is not after a failure to respond to antibiotic treatment that suspicions become heightened about a possible EAD. By this time, which could be weeks, there can have been extensive spread of AI to other sheds and properties. The above scenario is one of reality for past Australian AIV outbreaks.

The egg industry continues to have complacency in this area and in recent times due to national egg shortages this admixing behaviour through the movement of eggs and disposals has become even more prominent.

Layer sites have become larger, with the mixing of cage and free range facilities on the one site. Add some staff amenities, a feed mill and a grading and packing floor and we have a potential for large and costly outbreaks. The multi-functional nature of this type of operation is not a concern provided there is strict adherence to the principles of boundary biosecurity and these are applied for the horizontal contact movements. The presence of free range facilities, while meeting the expedience of producing higher value eggs on the main site, is considered a high risk practice.

The practice of having one egg truck moving from farm to farm offloading disposables and loading eggs is practicable and convenient but a high risk practice. Where producers have control over the series of farms and confidence in their on farm and between farm biosecurity practices then some of this risk will be mitigated but where the operations have contact with external suppliers and where there is lack of traceability the risks are much higher.

Producers should also ensure that all eggs that move into grading floors are located in their own designated zones with clear traceability. In the event of an EAD in a source flock then authorities can trace the product, quarantine it and dispose of it as required without the need to quarantine and dispose of the entire contents of the grading floor for example.

SUMMATION

The ongoing occurrence of AI in the egg industry is causing significant negative impacts at the level of the producer, industry, retailer and consumers, exporters and the overall governance policy makers with the later concerned about biosecurity compliance.

The increased direction of the industry into free range does heighten the risk of commercial birds coming in contact with the major vector of AI, wild water fowl. This risk to the egg industry though can be minimised if the well-known existing fundamentals of biosecurity are implemented.

The egg industry needs to progress a more coordinated approach to ensuring compliance with best practice through the ongoing implementation of its Egg Corp Assured programs. The industry itself in conjunctions with commonwealth and state governments and food safety authorities need also to establish mechanisms where non-aligned producers are enforced to implement sound biosecurity practices.