Highlights

• Submission trends: Marked reduction of 26 per cent in the total number of avian diagnostic submissions to AHVLA and SAC in the third quarter of 2012 compared with 2011 - 14 per cent decrease comparing the four-year average (2008-2011), comprising a 25 per cent drop in carcase submissions, but a four per cent rise in non-carcase submissions. Impact of high, volatile cereal and ration prices considered as contributory.
• New & Re-emerging diseases: First detection in GB poultry of multi-drug resistant Salmonella Java. Re-emergence of Goose parvovirus. Alerts for Fowl Typhoid in the UK and S. Stanley in EU poultry supply chains. Further findings from three ongoing new & emerging disease investigations.
• Unusual diagnoses: Infectious avian encephalomyelitis in backyard flock and coronavirus nephritis in 10- to 12-week-old pheasants in release pens.
• Changes in disease patterns and risk factors: Confidence sustained in the poultry meat sectors with increased day-old placings. Some respite for the layer sector with increased egg prices and a drop in ration prices since July peak. However, rising chick placings prompting future over-supply concerns.

New and Re-Emerging Diseases & Threats

During Q3-2012 no new and re-emerging diseases were identified in GB from analysis of available avian scanning surveillance information for broiler breeders, layer breeders, layers, turkey breeders, turkeys, ducks and backyard flocks. However, a new threat and a re-emerging threat were identified in a commercial broiler flock and a seasonal goose rearing flock respectively. In addition, two other emergent poultry threats were identified from AHVLA horizon-scanning surveillance activities. There were no other new and re-emerging disease investigations during the quarter.

First detection of multi-drug resistant Salmonella Java in GB poultry

Multi-drug resistant (MDR) Salmonella Paratyphi B variant Java (MDR Java) was detected from a commercial broiler holding in GB during Q3-2012. Clinically, diarrhoea and reduced flock performance were reported.

This represents the first detection of such a MDR Java isolate in GB poultry, and as such presents a new and emerging threat. S. Java has also been reported as an unusually persistent infection in broiler supply chains/poultry in other northern European countries, including dramatic increases in prevalence in some Member States (MS). For example, before 1996, less than two per cent of Salmonella isolates from poultry in the Netherlands (NL) were S. Java (11/462) compared with 60 per cent in 2002 (96/155), suggesting a clonal expansion (van Pelt, 2003). Furthermore, S. Java has now replaced S. Enteritidis as the main serotype in Dutch poultry. Human cases have also occurred in The Netherlands, Italy, Germany and the UK, the latter associated with chicken imported for further processing (Brown and others, 2003).

The development of antimicrobial resistance to therapeutic priority products used for the treatment of invasive salmonellosis in people (e.g. fluoroquinolones and cephalosporins) has also been reported. Due to the vertically and horizontally integrated nature of poultry supply chains, the potential exists for spread of infection, including via intra-community movements of hatching eggs, birds and products. Investigations into the affected broiler flock in GB have identified some of the birds originated from hatching eggs from northern Europe, indicating a likely source.

It is highly desirable that MDR Java is eliminated from any poultry flocks where it may be detected as quickly as possible to minimise the risk of persistence and spread. Control is based on rigorous cleansing and disinfection (C&D) to prevent biofilm formation and environmental persistence. The AHVLA, private veterinary surgeon (PVS) and flock owner have been working closely together to monitor the situation through advisory farm visits, the implementation of strict hygiene measures and extensive environmental sampling. The situation will continue to be monitored and AHVLA are interested to hear of any cases of suspected S. Java infection.

Re-emergence of fowl typhoid in the UK

An outbreak of Fowl Typhoid (FT), a disease caused by Salmonella Gallinarum biovar Gallinarum, has been reported in Northern Ireland involving two separate commercial poultry premises, the most recent during early November (ProMED, 2012a; b). Disease was initially diagnosed during September 2012 in a commercial housed layer flock of 125,000 birds, in one of three similar, linked houses on the site, following PVS investigation of escalating morbidity and mortality within the affected house.

Gross post mortem examination findings revealed generalised signs of septicaemia including enlargement and congestion of the liver, which developed a coppery surface sheen after exposure to air. FT is a well characterised bacterial disease in fowl, typically causing septicaemia and mortality. S. Gallinarum (SG) is not notifiable in the UK and is not considered to be of public health significance. However, it can have serious implications for poultry health and welfare, economics of production and may also affect international trade, particularly of poultry breeding stock/hatching eggs (Council Directive 2009/158/EC; Poultry Health Scheme). The affected layer site produces eggs for processing only, and fomites associated with the movement of eggs and/or personnel from outside the UK may have been a risk pathway for the introduction of SG.

There are no direct epidemiological links reported with the second affected and nearby site, but spread via wild bird contact with contaminated manure is considered a possibility. Both affected flocks have been culled voluntarily. There are no licensed SG vaccines available in the UK.

This outbreak represents a re-emergent threat to UK poultry. FT was last reported in GB during 2005 and 2006 following a gap of 20 years after the end of the statutory eradication programme. At that time, two of these outbreaks involved large commercial cage layer farms and incurred substantial losses; the other two cases were in backyard flocks with no known links to the layer sites (Cobb and others, 2005; Parmar & Davies, 2007).

Vertical and horizontal transmission are key features of FT epidemiology, recovered birds can act as carriers, and fomites, red mites (Dermanyssus gallinae), people, wildlife and environmental persistence are also important factors. Movements of birds or hatching eggs, contaminated fomites (e.g. egg trays) and/or red mite carriage on fomites/people present potential risk pathways for SG introduction into the poultry industry on mainland Britain. The situation will continue to be monitored and AHVLA are interested to hear from any colleagues who encounter cases of suspected Fowl Typhoid.

Further information is also available on the AHVLA web site [click here].

Salmonella Stanley – Be alert!

European veterinary and public health authorities have investigated a food-borne outbreak of Salmonella Stanley infection affecting people in seven EU Member States (MS), linked primarily to the turkey supply chain in at least one EU MS (EFSA, 2012).

From 01/08/11 to 18/09/12, 254 probable and 167 confirmed human cases were reported, including one from GB (during January 2012). S. Stanley isolates from the confirmed human cases have an identical genetic fingerprint (PFGE) pattern and are resistant to nalidixic acid. All confirmed cases also have no history of travel outside the EU, which was previously the most common route for acquisition of this infection, mainly from south-east Asia.

From 2004-2010, there were 55 reported isolations of S. Stanley from animals, food or feedstuffs in EU MS through national zoonoses monitoring (Directive 2003/99/EC) programmes; none were from turkey flocks/products. Similarly, no S. Stanley isolations were reported from the EU-wide baseline turkey flock Salmonella survey (2006/7). However, during 2011, a total of 311 S. Stanley isolates were reported, of which 298 (96 per cent) were linked with the turkey supply chain in five EU MS (n=275). This included breeder and fattening holdings and S. Stanley has also been detected from the broiler supply chain in Hungary and Germany. There were no reports of S. Stanley from any of the livestock sectors or from animal feedstuffs in the UK in 2011, but there have been two isolations of non-outbreak S. Stanley from feedstuffs during 2012.

Prevention and control at holding level centres on rigorous hygiene, C&D and biosecurity. Primary source investigations in the supply chain continue in affected EU MS to enable further risk management actions. Due to the vertically and horizontally integrated nature of poultry supply chains the potential exists for spread of infection, including via intra-community movements of hatching eggs, birds and products. AHVLA are very interested to hear of any cases of suspected S. Stanley infection of poultry, including nalidixic acid resistant strains.

Re-emergence of goose parvovirus in GB

Goose parvovirus (GPV) has been diagnosed in a seasonal, Christmas market production flock in England following submission of goslings to investigate high mortality (50 to 65 per cent) in two consecutive batches.

GPV is a well-characterised viral disease in geese (and Muscovy ducks), typically causing excess losses in birds less than six weeks old. There is no recognised public health significance and the disease is not notifiable. However, Official Area Declarations of GPV status may be required by some importing countries. Characteristic clinical findings were reported with typical histological findings and positive virus isolation results confirming the diagnosis (Irvine and Holmes, 2010).

GPV outbreaks have been diagnosed periodically in GB since 2004 (VIDA, 2011a). Vertical and horizontal transmission are key features of GPV epidemiology and recovered birds can act as latent carriers. GPV vaccination is reportedly widespread amongst goose breeder flocks in GB. However, the affected gosling batches were sourced from an apparently unvaccinated breeder flock in GB that hatched its own eggs. Risk pathways include the retention of recovered geese for later breeding, import of hatching eggs from infected parent flocks and wild bird exposure.

Further information about GPV is also available on the VLA web site [click here].

Ongoing New and Emerging Disease Investigations

Laboratory and field investigations continued into the reported cases of a seasonal respiratory disease in adult pheasants, myocarditis associated with reovirus infection in fattening turkeys and sinusitis in free-living red grouse, conditions described in previous quarterly avian Emerging Threats Reports in GB.

Seasonal respiratory disease in pheasants: ORT and 'Autumn Cough Syndrome'

During the winter months of 2009 and 2010, four cases of a respiratory condition characterised clinically as an 'autumn cough' affecting pheasants once released into a semi-wild state were investigated by AHVLA (Anon, 2010; 2011).

This is a multi-factorial condition associated with pneumonia and airsacculitis in affected birds, and a variety of both infectious causes and non-infectious contributory factors. One organism isolated in some cases has been Ornithobacterium rhinotracheale (ORT), a well-recognised component of respiratory disease in turkeys and chickens. The detection of ORT by culture and molecular methods has been described by Welchman and others in a series of four of these cases, from different game estates in southern England as part of a mixed aetiology. This included Mycoplasma gallisepticum (MG - a common cause of sinusitis in pheasants), coronavirus, avian paramyxovirus-2 and bacterial infection.

Although sinusitis is well-recognised in pheasants, involvement of the lower respiratory tract (lungs and air sacs) in bacterial and viral respiratory disease is less common, and would have accounted for the characteristic cough reported clinically. It is possible that susceptibility to the different infectious agents including ORT may have been exacerbated by the prevailing winter weather conditions. As this seasonal condition is seen in released pheasants in the autumn and winter, successful treatment is difficult to achieve. In some circumstances MG and other respiratory disease vaccines used in commercial poultry have been administered under the cascade system. However, their efficacy is unproven and outbreaks of lower respiratory tract disease may occur despite the use of such vaccines.

The problem currently remains seasonal, and ORT remains uncommon in game birds. However, continued investigation of field outbreaks will be required to monitor the impact of ORT and any other emerging infectious agents in the wider pheasant population.

Myocarditis associated with reovirus infection in fattening turkeys in GB

Investigation of an episode of increased mortality in one flock of commercial, housed fattening turkey poults from two weeks of age revealed histopathological lesions in the hearts of affected birds consistent with those described in cases of 'reovirus myocarditis'.

This condition is recognised as a typically sporadic disease affecting commercial meat turkeys in the USA (Shivaprasad and others, 2009; Franca and others, 2010). Initial findings described previously (Anon, 2012b) included the detection of a reovirus following virus isolation from the heart tissue of affected turkey poults (Figures 1-3). This finding has been further endorsed by immunohistochemistry giving reovirus-positive labelling. We would be very interested to hear from colleagues who experience any similar cases.

Figures 1-3: Abnormal hearts seen at post-mortem of 31-day-old fattening turkey poults. Round heart (Figure 1; left) compared with the appearance in a case of reovirus myocarditis - flaccid heart (Figure 2) and transverse section of formalin-fixed heart showing diffuse areas of myocardial pallor (Figure 3).

Sinusitis in free-living red grouse in Northern England

This seasonal condition was reported previously (Anon, 2012b) and is associated with Cryptosporidium baileyi infection, giving a 'bulgy eye' appearance in affected birds (Coldwell and others, 2012). Further cases have been investigated by AHVLA in northern England during Q3-2012, from separate, non-contiguous moors, and the involvement of cryptosporidia in these cases has again been demonstrated. Whilst this shows evidence of the further spread of this new disease, further investigations will be required to better elucidate the epidemiology.

AHVLA avian disease scanning surveillance activities, in partnership with SAC Consulting and working with private veterinary surgeons and industry continue to detect disease threats in GB. This highlights hazards and risk pathways that may exist for the poultry industry and poultry populations. Maintaining good biosecurity standards, disease awareness and vigilance and prompt investigation of problems are essential to limit both the risk of introduction and spread of infection and the impact of disease outbreaks. The situation will continue to be monitored through routine scanning surveillance activities and PVS and industry contact.

Unusual Diagnoses

Avian encephalomyelitis in backyard poultry

Infectious avian encephalomyelitis (IAE) was diagnosed in four-month-old bantams which had been seen ataxic the day before they were found dead in a backyard flock.

This disease is infrequently diagnosed in the backyard sector and it is unusual to find it in birds of this age. Typically, it causes clinical signs in young chicks following trans-ovarian infection.

In this case, it is possible that naïve birds may have become infected at a later stage as lateral transmission by the oral route is possible. IAE is a well recognised condition and control in commercial poultry is usually achieved through vaccination.

AHVLA surveillance activities continue to highlight common endemic avian disease problems in the backyard sector (e.g. Marek's disease, infectious laryngotracheitis, mycoplasmosis, red mite, infectious bronchitis virus, including QX variant strains). It is also relevant to note that the backyard poultry sector may act as both a reservoir and a sentinel for avian infectious disease (e.g. infectious coryza: click here; Welchman and others, 2010).

Coronavirus nephritis in young pheasants

This disease was first described in the late 1980s and is typically associated with mortality in adult pheasants during the breeding season. Sporadic diagnoses of coronavirus nephritis in game birds have been recorded by AHVLA every year since 2004 (VIDA, 2011b). During Q3-2012, coronavirus infection was more unusually diagnosed in one flock of 10- to 12-week-old pheasant poults, previously purchased and placed in release pens. It was reported that 230 of 1500 birds had died over several days. Postmortem examination found evidence of visceral gout and renal failure, subsequently shown by histopathology to be associated with interstitial nephritis.

An infectious bronchitis virus RRT-PCR test was performed on kidney tissue from a culled sick bird, which recorded a positive result, confirming the diagnosis. The situation will continue to be monitored through AHVLA scanning surveillance activities and PVS and industry contact.

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.

Further Reading You can view the full report by clicking here. Find out more information on the diseases mentioned in this article by clicking here.

January 2013