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GB Emerging Threats Report – Avian Diseases – January-March (Q1) 2013

09 August 2013

Avian influenza A(H7N9) virus infection in China and the rapid detection of a case of H9N2 low-pathogenic avian influenza in turkeys in eastern England are among the highlights of the latest AHVLA surveillance report.

Highlights

  • Submission trends: Decrease of 3.8 per cent in the total number of avian diagnostic submissions to AHVLA and SAC during Q1-2013 compared with Q1-2012. Total number of avian diagnostic submissions received by AHVLA virtually unchanged. However, drop in avian carcass submissions and continued upward trend in the numbers of non-carcass diagnostic submissions.
  • New & re-emerging diseases: Avian influenza A(H7N9) virus infection in China discussed.  Rapid detection of a case of H9N2 LPAI (non-notifiable) virus infection in GB.
  • Unusual diagnoses: A selection has been described in the monthly surveillance highlight reports published in the Veterinary Record by AHVLA and SAC.
  • Changes in industry and disease patterns: Confidence sustained in the poultry meat sectors. Change of ownership for VION-UK operations. Layer ration prices relatively stable, but still high. Egg producers challenged by weak market following recent expansion in size of national flock.

New and Re-emerging Diseases and Threats

January - March 2013

During Q1-2013 no new and re-emerging diseases were identified in GB for broilers, broiler breeders, layers, layer breeders, turkeys, turkey breeders, ducks, geese, game birds and backyard flocks.

However, horizon-scanning activities identified one new and emerging threat during the quarter, as described below. In addition, surveillance activities for suspected avian notifiable disease (AND) resulted in the detection of a non-notifiable avian influenza infection in turkey breeders during April 2013.

H7N9 influenza in China

During early March 2013 cases of human illness and fatalities associated with avian influenza A(H7N9) virus infection were reported affecting people in several regions of since mid-February 2013 (WHO, 2013a; ProMED, 2013). Illness in affected people was anecdotally linked to exposure to poultry and/or poultry products, indicating a possible source and zoonosis. The disease situation in people has been changing rapidly since its onset, with 131 human cases and 36 deaths reported as of 17/05/13 (case fatality rate 27 per cent), an age range of 2- to 91-years-old, with an unusual age/sex distribution of reported cases in people, and widening geographic distribution to nine regions of Eastern China. In addition, there has been one report of an 'imported' human case in Taiwan epidemiologically linked to mainland China (http://www.chp.gov.hk/en/view_content/24244.html; CDC, 2013a,b; WHO, 2013b; ProMED, 2013; Skowronski and others, 2013).

Importantly, there is no reported evidence of sustained person-to-person transmission to date (WHO, 2013b). The causative avian influenza A(H7N9) virus is a reassortant putatively with genes from avian-origin H7N9 and H9N2 avian influenza (AI) viruses (Defra, 2013a). It has been shown to be a low pathogenicity AI (LPAI) virus in poultry (AHVLA-Weybridge, pers. comm.; OIE, 2013a) but has also been shown to have acquired specific genetic changes that explain the ability to infect people.

The emergence of this novel influenza A virus from a likely animal source presents an ongoing threat to human health, as well as posing threats to both poultry health and supply chains. Furthermore, there are concerns regarding more severe public health impacts should the causative H7N9 virus undergo further adaptations that enable sustained community transmission within human populations that are immunologically naïve to infection with an H7 influenza A virus, including pandemic potential. It should also be noted that it is safe to eat properly prepared and cooked meat and eggs, but specific precautions are recommended when plucking poultry (OIE, 2013b). 

Investigations into the possible sources of infection and reservoirs of the virus in China are ongoing. There is increasing evidence of H7N9 LPAI virus infection in poultry and live bird (wet) markets. Sanitary disease control measures have been implemented to limit exposure risks (OIE, 2013a,b,c). Infection of poultry with H7 (and H5) AI viruses are notifiable to the OIE, as well as being subject to statutory sanitary disease control measures in Europe and many other parts of the world (OIE, 2012; CEC, 2006a,b). Furthermore, infection of poultry with H7N9 LPAI may result in few or no clinical signs, reducing the sensitivity of scanning surveillance detection methods and highlighting the importance of robustly validated laboratory methods. Work at AHVLA-Weybridge has confirmed detection of the H7N9 virus using molecular and serological tests recommended for notifiable AI diagnosis and statutory surveillance programmes in poultry (and wild birds) in the UK and Europe. The risk of introduction of this H7N9 LPAI virus through legal trade of poultry and poultry products is considered to be negligible (Defra, 2013b). Until the source of infection has been definitively identified and controlled, it is expected that there will be further cases of human infection. The WHO has recently published a risk assessment relating to human infections with avian influenza A(H7N9) virus (WHO, 2013c). The situation will continue to be monitored.

H9N2 LPAI virus infection detected from turkey breeders in England

Official field and laboratory investigations following the prompt notification to AHVLA of suspected avian notifiable disease (AND) resulted in the diagnosis of H9N2 LPAI (non-notifiable) virus infection affecting turkey breeders on a premises in East Anglia. Initial clinical signs comprised an acute onset of coughing, a drop in feed consumption with an estimated morbidity of 10 per cent. Within 48 hours, morbidity was estimated to be 90 per cent with respiratory signs, lethargy and the onset of losses (average daily mortality of approximately one per cent over five days).

Post-mortem findings included mild airsacculitis in the absence of sinusitis. Detailed molecular investigation and characterisation of the H9N2 LPAI virus (European lineage) at AHVLA Weybridge also confirmed properties indicative of a low zoonotic risk. Whilst the exact source of the virus was not definitively confirmed no other cases were reported. Such incidents also serve as a reminder of the potential risks to poultry health, as well as zoonotic hazards. LPAI viruses can often cause subclinical infections in poultry making recognition and detection of disease more difficult, a potential contributory factor conducive to spread. The risk also exists of more extensive secondary spread in areas of higher poultry population density. During Q1-2013, notifiable (H5/H7) LPAI outbreaks were also reported in northern Europe (Defra, 2013c,d).

The last AND outbreak in poultry in GB occurred during June/July 2008 (H7N7 HPAI in a free-range layer flock, Oxfordshire; Defra, 2008). Over the period 2009-2012, there were approximately 30 cases of suspected AND reported to AHVLA each year.

These all resulted in official veterinary investigation. In approximately half of these cases, AND was ruled out based on the clinical presentation. For the remainder, samples were submitted for statutory laboratory testing at AHVLA Weybridge. This resulted in seven separate detections of non-notifiable AI and avian paramyxovirus type 1 (APMV-1) virus infection during this four-year period.

The source of these infections was most commonly putatively attributed to be wild birds. These events highlight the continuous threat presented to poultry health by AI and APMV-1 viruses. The importance of maintaining good flock biosecurity and hygiene practices at all times, and prompt reporting of suspected AND to the veterinary authorities are also emphasised.

Ongoing New and Emerging Disease Investigations

No further updates to report for Q1-2013.

Unusual Diagnoses

A number of unusual diagnoses were made in backyard and commercial poultry during Q1-2013 and the course of the year. A selection have been described in the monthly surveillance highlight reports published in the Veterinary Record by AHVLA and SAC (AHVLA, 2013; SAC, 2012,2013). In these cases, no wider threats were recognised and no specific actions required other than for producers and veterinarians to maintain vigilance for disease problems and investigate as appropriate.

Changes in the Industry, Disease Patterns and Risk Factors

Broilers

The number of day-old broiler chicks placed from UK hatcheries during Q1-2013 was 3.6 per cent higher than the same time last year, continuing the upward trend in placings seen since Q1-2011 (Figure 5). This reflects continued confidence and consumer demand for chicken meat and follows an annual sector growth of 2.5 per cent during 2012 compared with the previous year. This has been achieved through changes to the numbers of broiler crops placed per year.

During Q1-2013 changes to the structure of the broiler sector in GB were also announced. The VION Food Group, a Dutch-owned farmers’ cooperative (VION-NV) divested their red- and white-meat processing operation in the United Kingdom (VION-UK). The 2 Sisters Food Group has purchased VION-UK's red meat and poultry processing capacity. The latter comprises seven plants in GB processing at least three million broilers per week and approximately 20 per cent of annual national broiler throughput.

The VION-UK poultry farming division in GB - VION Agriculture - has been bought by a 2 Sisters-related company, and renamed '2 Agriculture'. This comprises feed mills, hatcheries, veterinary division and company-owned broiler farms. The deals have been stated as safeguarding key supply chains to meet growing demand for British-sourced poultry.


Figure 5. Quarterly broiler chick placings (average) from UK hatcheries, 2011-2013

Layers

The number of layer chick placings declined both since the previous quarter (Q4-2012) and compared with Q1-2012 (Figure 6). Overall, layer chick placings dropped by seven per cent compared with Q1-2012. This follows national layer flock placings reaching 34.7 million birds during 2012, the highest figure for 10 years.

The current size of the UK laying flock of approximately 33 million birds is equivalent to that seen during 2010/11 when rapid expansion led to marked egg over-supply and low wholesale and retail egg prices. In turn, these conditions led to pressurised margins as costs of production exceeded income (Anon, 2011a,b,c). This cycle is now being repeated, with a weak egg market and high feed prices.

The reduction in layer chick placings seen during Q1-2013 will lead to a small reduction in the size of the national flock, but estimates indicate that by mid-2013 there will be approximately three million more hens present in the national flock than the same period 12 months ago.

Packing station throughput increased slightly during Q-2013 (Figure 7). Free-range and organic eggs accounted for 47 per cent of eggs packed during Q1-2013, the same as during Q4-2012.


Figure 6. Quarterly layer chick placings (average) from UK hatcheries, 2011-2013


Figure 7. Total and free-range UK packing station egg throughput 2011-2013

An imbalance between input costs and the prices paid for products affects profitability for producers. This is considered a risk factor for both prevention and control of disease and scanning surveillance coverage as diagnostic services may be less likely to be sought. These issues were also described in previous quarterly avian disease 'Emerging Threats' Reports.

Issues relating to feed and egg prices and the size of the national flock (including the impact of the EU-wide conventional layer cage ban) have also been discussed previously (Anon, 2011c; 2012a,e).

Turkeys

There was a 5.5 per cent decline in the numbers of turkey poults placed during Q1-2013 compared with the same period last year (Figure 8). However, the sector as a whole remains buoyant. The numbers of turkey poults placed during 2012 was 6.0 per cent higher than in 2011, at 18 million birds. This represented an increase of one million poults placed compared with 2011, and an annual total last seen in 2005.

This parallels trends in the broiler sector and reflects continued confidence in poultry meat production, which has been particularly marked in turkeys compared with previous years. There was a 3.4 per cent increase in UK poultry meat output during 2012 compared with 2011, exceeding 1.6 million tonnes.


Figure 8. Quarterly turkey poult placings (average) from UK hatcheries, 2011-2013
 

Further Reading

You can visit the Avian Flu page by clicking here.

August 2013



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