GB Emerging Threats Report – Avian Diseases – July-September (Q3) 201303 January 2014
Among the highlights of the latest report are the re-emergence of fowl typhoid in the UK in two linked free-range layer flocks and reovirus-associated tenosynovitis.
- Submission trends: Increase of 1.3 per cent in the total number of avian diagnostic submissions to AHVLA and SAC during Q3-2013 compared with Q3-2012. Drop of 7 per cent in avian carcase submissions and increase of 12 per cent in non-carcase diagnostic submissions. Approximately 25 per cent of Q3 avian diagnostic submissions were from game bird flocks and two-thirds from chicken flocks.
- New & Re-emerging diseases: Re-emergence of Fowl Typhoid (Salmonella Gallinarum) in the UK, affecting two linked free-range layer flocks. Ongoing diagnoses and investigation of reovirus-associated tenosynovitis in broilers and respiratory cryptosporidiosis in free-living red grouse.
- Unusual diagnoses: Myeloid leukosis diagnosed in a backyard flock, with ALV ‘J strain’ isolated. A selection of other cases has been described in the monthly surveillance highlights reports published in the Veterinary Record.
- Changes in the industry and disease patterns: Confidence and growth sustained in the broiler sector. Some respite for egg producers as demand and egg prices increased and size of the national flock and feed prices decreased. However, egg market is considered likely to remain ‘finely balanced’.
New and Re-emerging Diseases & Threats
During Q3-2013 one re-emerging disease threat was identified through AHVLA horizon-scanning surveillance activities affecting commercial layers. No new and re-emerging diseases or threats were identified for broilers, broiler breeders, layer breeders, turkeys, turkey breeders, ducks, geese, game birds and backyard flocks in GB. Investigations also continued into two other emergent poultry threats reported previously, affecting broiler flocks and game birds in GB, as described below.
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 free-range layer premises during September 2013 (OIE, 2013).
The affected sites are owned by the same company and are located two miles apart. At the time of the outbreak the flocks comprised 6,000 and 24,000 hens, respectively, aged approximately 40 weeks.
At both sites, acute onset losses were experienced in one house with a cumulative two per cent mortality. All birds were culled voluntarily within one week of the diagnosis and intensive cleansing and disinfection is in progress. This follows a previous outbreak that started in September 2012 and involved two separate commercial poultry premises (Anon, 2012a).
There is no apparent epidemiological link between these two outbreaks and the free-range layer sites are located approximately 50 miles distant from the premises affected during 2012.
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). There are no licensed SG vaccines available in the UK.
This outbreak in free-range layer premises represents a re-emerging threat to UK poultry. Prior to the outbreak during 2012, FT was last reported in GB during 2005 and 2006 following a gap of 20 years after the end of the statutory eradication programme (Anon, 2012a).
Vertical and horizontal transmission are key features of FT epidemiology. Recovered birds can also 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 equipment (eg. egg trays) and/or red mite carriage on equipment and 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 at: www.defra.gov.uk/ahvla-en/disease-control/non-notifiable/fowl-typhoid/.
Ongoing New and Emerging Disease Investigations
Reovirus-associated tenosynovitis/arthritis in broilers
Investigations of lameness and tenosynovitis problems in broilers continued during Q3-2013, mainly due to concerns relating to reovirus-associated disease, as described previously (Anon, 2013).
Three further cases from different regions of GB were confirmed during the quarter following the isolation of a reovirus from affected hock tissues. This gives a total of four cases diagnosed by AHVLA since Q2-2013 in GB.
Serological testing has also been performed by Virus Neutralisation Test (VNT). Sera from several affected broiler flocks from one broiler integration were tested with positive results.
The reovirus isolated from the index case flock in this company was used in the VNT assay. Reoviruses are considered ubiquitous in poultry, can cause other diseases in chickens, and are not associated with public health or international trade implications. Veterinary investigation of affected flocks and differential diagnoses is important so that appropriate treatment, prevention and control measures can be implemented (Anon, 2013).
AHVLA would also be interested to hear from colleagues who have experienced cases.
Investigations are continuing and the situation will continue to be monitored through AHVLA scanning surveillance activities and poultry PVS (PPVS) contact.
Sinusitis in free-living red grouse in northern England and southern Scotland
This seasonal condition has been reported previously (Anon, 2012d) 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 both SAC and AHVLA during Q3-2013, with cases being diagnosed in the Scottish Borders and from a moor in Lancashire, respectively.
These incidents represent the likely northern and most southerly reports of confirmed disease to date, and provide evidence of the further spread of this new and emerging disease.
AHVLA has also been investigating comparative testing approaches to enable timely and cost-effective laboratory diagnosis. However, further investigations will be required to better elucidate the epidemiology of this condition.
Endemic poultry diseases, including some unusual cases, continued to be diagnosed in backyard and commercial poultry during Q3-2013 in GB, with some interesting and unusual investigations outlined below. A selection has also been described in the monthly surveillance highlight reports published in the Veterinary Record (SAC, 2013a,b,c). 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.
Myelocytoma: Avian Leukosis Virus ‘J strain’ associated disease
A 12-month-old backyard bantam chicken presented with partial paralysis, lameness and audible croaking respirations. It was purchased at four months of age, and five other chickens were reported by the owner to have died with similar signs over several months, out of a small, mixed species flock of 11 birds.
At PME, widespread, pale, tumour-like infiltrations were present in the majority of organs and histopathology indicated a myelocytoma. This is a variety of myeloid leukosis, one of the many types of tumour that can occur in chickens infected with Avian Leukosis Viruses (ALV).
Whilst myelocytomas can rarely arise spontaneously, in the past they have been typically associated with the so-called J strain of ALV (ALV-J). This strain has been eliminated from commercial broilers and has not been recorded in the UK for several years.
Virus isolation has resulted in the detection of ALV-J in this case, indicating the parent birds are likely to also be infected. This could result in further localised cases in related backyard birds. Investigations are ongoing and the situation will continue to be monitored through scanning surveillance activities and PVS contact.
Biosecurity-related disease problems in backyard flocks
Several cases investigated this quarter illustrated issues associated with suboptimal biosecurity in the backyard sector.
Infection with strains of the European QX-like variant of Infectious Bronchitis virus (IBV) was reported in small, mixed-age flocks following the purchase of hens, sometimes from a variety of sources, and resulted in mortality and significant respiratory disease.
Infectious laryngotracheitis (ILT) resulted in 12 deaths and extensive respiratory disease in a group of 20 chickens aged four months. The outbreak was linked to birds returning to the premises from a poultry show.
Purchased hens were also thought to have introduced Avian Intestinal spirochaetosis into a backyard flock.
AHVLA scanning surveillance activities continue to highlight common endemic poultry disease problems, e.g. Marek’s disease in chickens, ILT, IBV, mycoplasmosis, egg peritonitis, adenocarcinoma, ectoparasite (eg. red mite, lice) and endoparasite infections. In addition, presentations of disease in unusual host species are also detected, notably in the last 12 months, Marek’s disease in turkeys (Deuchande and others, 2012).