GB Emerging Threats Report: Avian Diseases: October-December (Q4) 201313 June 2014
Among the highlights in this quarterly report are the re-emergence of avian influenza A(H7N9) virus infection in China as well as in the UK the detection of livestock-associated MRSA and reovirus-associated tenosynovitis in broilers.
Submission trends: Decrease of 21 per cent in the total number of avian diagnostic submissions to AHVLA and SAC during Q4-2013 compared with Q4-2012. Drop of seven per cent in the total number of avian diagnostic submissions to AHVLA and SAC during 2013. Long- and short-term avian diagnostic submission patterns and trends and factors affecting scanning surveillance are discussed.
New & Re-emerging diseases: Re-emergence of avian influenza A(H7N9) virus infection in China. Detection of LA-MRSA from a farm in GB. Ongoing diagnoses of reovirus-associated tenosynovitis in broilers and ‘Autumn cough’ syndrome in adult pheasants. Summary of other threats seen during 2013.
Unusual diagnoses: Ulcerative enteritis in game birds. A selection of other cases has been described in the AHVLA and SAC 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 gains for egg producers as egg prices increased and size of the national flock and feed prices stabilised. However, concerns and uncertainty remain over future egg market volatility.
New and Re-emerging Diseases and Threats: October – December 2013
During Q4-2013 the re-emergence of avian influenza A (H7N9) infections affecting people and poultry in China was identified as a re-emerging disease threat through AHVLA and Defra horizon-scanning surveillance activities. One new and re-emerging threat (NRT) was identified at a poultry farm, with the first detection of Livestock-associated MRSA in farmed livestock in GB. Investigations also continued into two other poultry disease threats reported previously, affecting broiler flocks and game birds in Great Britain, respectively.
These are described below. No further new and re-emerging diseases or threats were identified for broiler breeders, layer breeders, layers, turkey breeders, ducks, geese, game birds and backyard flocks in GB.
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 China since mid-February 2013 (WHO, 2013; ProMED, 2013).
These reports were soon followed by confirmation of H7N9 LowPathogenicity Avian Influenza (LPAI) infection in poultry and environmental samples from live bird markets in the same regions as the human cases (Anon, 2013b). Since then two waves of disease have been identified in people suggesting a seasonal pattern. To July 2013 there were 132 human cases and 44 deaths reported from ten regions of Eastern China. Only sporadic numbers of human cases were then reported until October 2013 when the number of cases started to increase (CDC, 2014).
There is still no evidence of sustained human-to-human transmission (WHO, 2014). In the majority of cases, contact with poultry or live bird markets is a significant risk factor (FAO, 2014), which presents risk pathways for susceptible birds and people (poultry/market workers and consumers). A small number of ‘exported’ cases have also occurred via infected travellers in countries outside China (Taiwan, Hong Kong, Malaysia; NaTHNaC, 2014). This raises a further possible risk pathway for infection of livestock by reverse zoonosis if contact of an infectious person were to occur with susceptible animal species.
However, the risk of disease spreading to Europe via people is considered low (ECDC, 2014), but this could change if the virus acquired the capability to transmit between humans. The risk of introduction of avian influenza A (H7N9) through legal trade in any poultry products is considered to be negligible (Defra, 2014).
Livestock-associated MRSA detected at a poultry farm in GB
The presence of Livestock-associated Methicillin Resistant Staphylococcus aureus (LA-MRSA) was identified as an incidental finding following the investigation of an unrelated health problem affecting a turkey flock in GB. The cause of the health problem was diagnosed as Marek’s disease, a disease that is considered to be uncommon in turkeys (Deuchande and others, 2012). LA-MRSA has been identified in livestock in a number of countries and is not considered to represent a significant risk to animal health and welfare. LA-MRSA is also not the same as those that cause healthcare associated infections that affect people. The risk of getting LA-MRSA from eating poultry meat is very low if the meat is handled hygienically and cooked thoroughly to kill any bacteria and the risk of the general public catching LA-MRSA from an animal is also very low (Defra, 2013). AHVLA and SAC contribute to the programme to monitor antibiotic resistance in bacteria isolated from livestock in GB on behalf of the Veterinary Medicines Directorate (VMD) and Defra. In this case farm visits and other cross-government veterinary and public health investigations were performed. These enabled a fuller understanding of the epidemiology and biology of the LA-MRSA organism that was detected, provision of relevant advice and enabled prompt control.
New and Re-emerging Diseases and Threats: January – December 2013
AHVLA avian scanning surveillance activities, in partnership with SAC Consulting and working with private veterinary surgeons, industry and Defra, highlight hazards and risk pathways that may exist for the poultry industry and poultry populations in GB. Ten NRTs were identified during 2013 (Table 1).
New and re-emerging diseases and threats identified and investigated in poultry by AHVLA and SAC Consulting during 2013
- Avian influenza A(H7N9) in China
- H9N2 LPAI (non-notifiable) virus infection in GB
- Challenges faced by egg producers in the face of changes in the size of the national flock and weak egg market
- Tenosynovitis associated with reovirus infection in broilers in the UK
- Re-emergence of Newcastle disease lineage 5a in Europe
- Outbreak of H7N7 HPAI in Italy
- White striping/wooden breast affecting broiler meat quality
- Re-emergence of Fowl Typhoid in the UK
- Spread of respiratory cryptosporidiosis (sinusitis) in free-living red grouse on moors in northern England & Scotland
- Livestock-associated MRSA found at a poultry farm in GB
Investigations associated with the NRTs affecting poultry in the UK have also been described in the quarterly avian disease surveillance reports. These reports and other advisory material for vets and poultry producers are available at www.defra.gov.uk/ahvla-en/publication/avian-survreports/.
Maintaining good biosecurity and hygiene 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. Surveillance activities and PVS and industry contact continue to monitor for the presence of any potential new or re-emergent threats in the GB poultry population.
Ongoing New and Re-emerging Disease Investigations
Seasonal respiratory disease in pheasants: ORT and 'Autumn cough' syndrome
During the winter months of 2009, 2010 and 2012 cases of a respiratory syndrome in pheasants once released into a semi-wild state were investigated by AHVLA (Anon, 2012); some cases were characterised clinically as an 'autumn cough'. This is a multifactorial condition associated with pneumonia and airsacculitis in affected birds, and a variety of both infectious and non-infectious causes may be contributory.
Ornithobacterium rhinotracheale (ORT) has been isolated in some cases. ORT is a well-recognised component of respiratory disease in turkeys and chickens. The detection of ORT from the lungs of affected pheasants has recently been described, as part of a mixed aetiology, and may account for the cough reported clinically (Welchman and others, 2013). In December 2013 further cases of the condition were investigated by AHVLA on a shooting estate in southern England, again with a mixed aetiology including ORT, in birds with severe changes in the lungs and airsacs. The course of this disease may be affected by the increasing use of respiratory disease vaccines in pheasants under the cascade, but these are generally of unproven efficacy in this species and, in any case, are not effective against the full range of respiratory pathogens that can be detected in the affected birds. The problem currently remains seasonal, but 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.
Reovirus-associated tenosynovitis/arthritis in broilers
Investigations of lameness and tenosynovitis problems in broilers continued during Q4-2013, mainly due to concerns relating to reovirus-associated disease, as described previously (Anon, 2013a,c). A total of nine cases have been diagnosed by AHVLA since Q2-2013 from different regions of GB following the isolation of a reovirus from affected hock tissues.
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, 2013c). We would also be interested to hear from colleagues who have experienced cases. Investigations continue and the situation will continue to be monitored through AHVLA scanning surveillance activities and PVS contact.
Endemic poultry diseases, including some unusual cases, continued to be diagnosed in backyard and commercial poultry during Q4-2013 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 (AHVLA, 2014; SAC, 2013a). 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.
Ulcerative enteritis in game birds: a possible new aetiological agent
Ulcerative enteritis (UE) is regarded principally as a disease of quail, and is considered to be caused by infection with the anaerobic bacterium, Clostridium colinum. AHVLA has also diagnosed UE in red-legged partridges (Alectoris rufa). UE-like lesions were found on post-mortem examination of a two year-old Capercaillie (Tetrao urogallos) from a small private collection, which had died shortly after falling ill.
Anaerobic bacterial cultures of the intestine and caeca yielded a heavy mixed growth of organisms including Clostridium sordellii but C. colinum was not detected. Whilst UE in quail and some other game birds is attributed primarily to Clostridium colinum infection, outbreaks of UE-like disease in quail have also recently been associated with C. sordellii , and this organism can occasionally be isolated from other bird species (Crespo and others, 2013).
The findings in this case indicated that C. sordellii should be considered in the aetiology of this condition in game birds other than quail. A primary aetiological role has not yet been confirmed for C. sordellii, but nevertheless the possible role of this agent should be investigated in future cases of suspected UE identified by scanning surveillance.