December 11, 2019

expert reaction to avian influenza (bird flu) being identified on a commercial chicken farm in Suffolk

An out break of avian influenza (bird flu) has been discovered on a Suffolk poultry farm.

Dr Holly Shelton, Group Leader of the Influenza Viruses group, The Pirbright Institute, said:

“This is the first outbreak in UK poultry since the 2017 H5N8 outbreaks.  The virus in this outbreak is different to that of the 2017 outbreak in that it is classified as a low pathogenic avian influenza virus.  In 2017 the outbreak was caused by a highly pathogenic virus.  This means that the virus causing the current outbreak has molecular characteristics in the virus surface attachment protein (H) that restrict infection to the respiratory and gastrointestinal tract of these birds, whereas highly pathogenic strains can spread systemically to every organ of an infected bird.

“The term highly pathogenic or low pathogenic does not refer to the infectious nature of the virus and this low pathogenic virus is likely to be spread just as easily amongst avian species including any wild birds that are in contact with the contaminated holding.  This is why the response of the government agencies is very important and the controlled zones around the infected premises should be taken seriously.  Low pathogenic H5 influenza viruses have the potential to evolve in poultry to produce highly pathogenic H5 viruses so understanding the genetics of the virus is also a priority.

“The source of the outbreak is unknown at the moment and the genetic analysis of the virus will help with identification of this by comparison to other H5 viruses.  However in the past outbreaks on poultry farms have been initiated by transmission of the virus from wild birds to susceptible animals on poultry farms.”

Prof Wendy Barclay, Chair in Influenza Virology, Imperial College London, said:

“The virus that has been detected is classed as of low pathogenicity.  This means it doesn’t kill the chicken but causes milder disease.  Some H5 viruses can mutate as they circulate in poultry and become more pathogenic.  It will be important to monitor the virus here and to control this outbreak to minimize the chances that happens.  Even then, the virus is unlikely to infect people unless it undergoes more mutations that adapt it to humans.  Those mutations are rare, and some avian viruses never acquire them at all.  Provided the people involved in controlling the outbreak wear suitable protective clothing there is little risk to humans from this bird flu strain.”

Prof Mick Bailey, Professor of Comparative Immunology, Bristol Veterinary School, University of Bristol, said:

“Wild birds in the North of Asia are the main source of avian influenza across the world.  New strains of avian influenza mostly appear there.  However, every winter, migrating birds (mostly water fowl) bring the new strains on a range of flight paths across into Europe, down into south east Asia and down the west coast of North America.  Each year, there is the potential for these birds to infect local, non-migratory wild birds and domesticated poultry.  In the UK, we had several outbreaks in wild birds and commercial chickens in the winter of 2017/8, but not the winter of 2018/9.

“In general, spread between commercial poultry units has been well-controlled by the preventative measures Defra impose (movement restrictions, culling etc.).  The main risk to any individual poultry unit or smallholder is from wild birds.  Having said that, there is a risk that some smallholders may assume that the risk is only to the larger units and that they don’t need to worry – in fact, the more free-range their birds are, the more they are at risk of getting the virus from wild birds.

“High pathogenicity avian influenza (HPAI) and low pathogenicity (LPAI) are defined by the severity of the disease in the birds.  Low pathogenicity causes only mild symptoms in birds, whereas high pathogenicity causes very high mortality in birds.  Influenza viruses are characterised by two proteins, the H-protein and the N-protein, each of which can be of one or more types (e.g. H3N2).  The normal, seasonal flu in humans, or the big pandemics like the 2009 ‘swine flu’ have mostly been H1, H2 or H3.  The bird outbreaks have mostly been H5 or H7.

“However, the H5 and H7 bird strains can infect humans.  Across the world, this has only happened a couple of thousand times since 2000 – it seems that transmission from birds to humans is very rare (there seem to have been 1,567 confirmed cases of H7N9 and 861 of H5N1 since 2000, and none in the UK; given the amount of contact between birds and humans, this is a tiny amount of transmission).  When it does happen, though, it can be quite nasty which is why workers exposed to infected chickens are given antivirals as a precaution, even though the risk of infection is very low.  In addition, although it’s not normally a problem, pigs can also get bird flu from poultry, so it’s worth restricting close contact between pigs and chickens (e.g. in smallholdings) in affected areas.”

Prof John Oxford, Professor of Virology, Queen Mary University of London, said:

“Firstly we are lucky that this is the low pathogenic H5.  In practice this means that it is not likely to spread to humans.  The people at some risk are those dealing on site to kill the birds, which is also a soul-destroying task.  They will wear protective gear and masks and will not move to other farms in the exclusion zone.  They will have been trained and will have masks and goggles.  The virus can potentially be spread to these workers or chicken keepers via feather dust and chicken droppings, which is why they wear protective clothing.  A sensible idea is to give them a course of the anti flu drug Tamiflu which blocks H5 viruses.

“An important and worrying question is where the virus has come from.  In other words, has there been a quiet outbreak going on which has been missed in the UK or has some wild bird brought it in from Europe, or has the farm brought in eggs or chickens and if so from where.  Obviously the timing is bad for the Christmas season and I feel sorry for the poultry farmers affected.  The virus is easily killed by hot water and detergent and so equipment can be sprayed and outfits and gloves worn, and hands washed.”

Prof Paul Wigley, Professor of Avian Infection and Immunity, University of Liverpool, said:

“Avian influenza or ‘bird flu’ is not a common disease in the UK.  The current outbreak is of a low pathogenicity or LPAI type which leads to symptoms including respiratory distress and diarrhoea in chickens.  The virus can spread around flocks through respiratory secretions or faeces.  LPAI may infrequently cause human infections causing problems like conjunctivitis but unlike High Pathogenicity or HPAI are not usually associated with human influenza.

“Influenza viruses are typed by the surface structures haemaglutinin (H) and neuraminidase (N).  Avian flu is usually H5 or H7 type, whereas human influenza is more usually H1 or H3 type.

“The cull and restriction action undertaken by DEFRA is entirely the right course of action to stop both the spread of the disease into the UK poultry industry and for the welfare of the infected flock as there is no effective treatment for chickens.”

Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“Over the past few years we’ve seen sporadic outbreaks of avian influenza in various parts of the UK.  Usually these have been influenza strains that are deemed to be low pathogenic viruses, as is the case here – in other words viruses that are not associated with very serious symptoms in the domestic birds in which they’ve been found.

“Whilst in other parts of the world we have seen cases of so-called ‘bird-flu’ strains jumping into humans, this is a rare event and hasn’t been seen in the UK, so the risk to human health is very low.

“We know that lots of strains of influenza viruses circulate in wild bird populations and when biosecurity efforts are breached and these strains are introduced into poultry farms then the disease can spread rapidly – this is always going to be a risk in places where you have such high densities of birds.  The risk of spread to other farmed birds is real, which is why we see restrictions around affected farms and why the affected bird flocks are killed.”

Dr Colin Butter, Associate Professor and Programme Leader in Bioveterinary Science, University of Lincoln, said:

“Whilst outbreaks of Avian Influenza are not common in the UK, their effects can be of substantial economic significance.  It is particularly important to know if this case has arisen through transmission of virus from wild bird populations, as in the case of the 2016/17 H5N8 these were the source of many outbreaks over a protected period.  The critical information will be how many wild birds are infected and of which species.  If numbers are low then the control measures already taken may control the infection.  If high, then other infections of poultry are likely.

“Whilst it should also be remembered that the three human flu pandemics of the last century all resulted from natural genetic changes to avian flu viruses, there is no immediate threat to human health and properly cooked poultry mean is completely safe to eat.  Christmas dinners are not under threat!”

Daniella Dos Santos, President of the British Veterinary Association, said:

“We’d like to emphasise that this strain of avian influenza virus poses very low risk to public health and disease control actions taken to date reduce risks to poultry health.

“The quick identification of the suspected case by a private veterinary surgeon and swift precautionary measures to contain the disease also illustrate the ongoing importance of a robust veterinary surveillance system.  BVA and BVPA urge all vets and poultry keepers, including keepers of backyard flocks and seasonal poultry producers, to remain vigilant to any unusual signs of disease and continue to maintain the highest standards of hygiene and biosecurity.  Any suspicions of avian influenza should be reported to Defra as soon as possible.”

https://www.gov.uk/government/news/avian-influenza-bird-flu-identified-in-suffolk

Declared interests

Dr Holly Shelton: “No conflicts of interest.”

Prof Wendy Barclay: “I have received personal and non personal funding from Roche in regard of their new anti-influenza drug.”

Prof Mick Bailey: “I work on influenza, funded by the BBSRC, specifically in pigs but as part of the global pattern of influenza as a zoonosis and reverse zoonosis.  Meriel, who manufacture influenza vaccines for pigs are one of our collaborators, and we also collaborate with APHA, who are the UK centre for animal influenza preparedness, and the Pirbright Institute for animal virus research.”

Prof John Oxford: “I have no conflicts of interest.”

Prof Jonathan Ball: “None.”

Dr Colin Butter: “I have no conflicting interests.”

None others received.