IMAGE: ISRAEL NATURE AND PARKS AUTHORITY. EDITORIAL: BBC - https://www.bbc.com/news/world-middle-east-59808888
Tens of thousands of turkeys are being destroyed in Israel, as it tries to contain a serious avian flu outbreak.
More than 5,000 migratory cranes have already died at the Hula Nature Reserve, which Environment Minister Tamar Zandberg called "the worst blow to wildlife" in Israel's history.
Local farmers were also being forced to cull half a million chickens, prompting fears of a possible egg shortage.
So far no transmission of the A(H5N1) virus to humans has been reported.
However, Prime Minister Naftali Bennett met his national security adviser and other experts on Monday to discuss efforts to stop that from happening.
People who have been in close contact with infected birds are being given preventative treatment.
Although transmission from birds to humans is a rare event, the deaths of 456 people infected with the virus have been reported worldwide since 2003, according to the World Health Organization.
Images published by the Israel Nature and Parks Authority showed rangers in protective suits using a dinghy to retrieve the dead cranes from Hula Lake to prevent other wildlife being infected.
The authority also reported that the remains of 250 cranes had been seen in the surrounding Hula Valley and that 30 sick cranes had been observed elsewhere in the country.
The sight of tens of thousands of cranes from Europe wintering at the Hula Nature Reserve is usually a delight for bird-watchers. But the site was declared off-bounds to visitors last week because of the devastating avian flu outbreak.
Avian flu viruses occur naturally in migratory waterfowl, which tend not to develop symptoms.
Domestic birds are far more susceptible and once the virus is found in commercial or household flocks, rapid destruction is recommended of all birds that might be infected.
Israeli media reported that more than half a million egg-laying chickens at Moshav Margaliot, a communal farm about 12km (7 miles) to the north, were being culled in an effort to contain the outbreak and minimise risk to humans. The moshav provides 7% of all the eggs consumed in Israel.
The Times of Israel said the first outbreak of avian flu in Israel this autumn was reported on 18 October at Moshav Nahalal in the Jezreel Valley, about 60km south-west of the Hula Nature Reserve.
In November, cases were reported at a kibbutz and two poultry farms, it added.
Avian influenza is a disease that is caused by influenza A viruses. There are broad types of influenza virus, A, B, and C but avian influenza viruses are all influenza A viruses and that is the type of virus referred to in this article. Influenza viruses infect many different host species such as humans, birds, pigs and horses as well as more exotic species such as seals, whales and tigers. The natural reservoir for the majority of influenza viruses is wild aquatic birds such as ducks and geese as well as shore birds like gulls and waders. Poultry encompassing chickens, turkeys, quails and game birds are not a natural hosts and subtle adaptation of the viruses must occur upon transmission from wild birds to poultry if the virus is to be successful at infecting them. As a consequence we don’t see all subtypes of avian influenza virus causing outbreaks in poultry. There is a spectrum of disease in birds caused by avian influenza infection ranging from asymptomatic through moderate signs like reduced growth and egg production to high mortality.
Influenza viruses contain genetic material that encodes for all the viral factors required to successful infect cells. Influenza genetic material is called RNA, a related molecule to DNA which animals use as their genetic material. The RNA of the virus is split or segmented into 8 individual pieces per virus and contained inside a protein shell (Figure 1). The protein scaffold of the virus is covered by a membrane envelope into which two very important viral proteins are embedded. The Haemagglutinin protein or H protein is responsible for the attachment and entry of influenza viruses into host cells. The Neuraminidase or N protein helps new viruses escape from cells and spread to new cells and hosts. The combination of H and N protein on the outside of the virus determines the subtype of the virus eg H5N1 or H7N7. There are currently 16 different H subtypes and 9 different N subtypes which circulate in avian species. The segmented nature of the virus genetic material that encodes for viral proteins including the H and N proteins, enables different strains to mix up and swap segments if they infect the same cell, this we call reassortment (Figure 2). Therefore theoretically 144 combinations of different H and N could exist. Currently approximately 90 different combinations have been identified and isolated from wild bird species. Not all these strains are capable of efficiently infecting poultry species because of differences host factors that the virus must interact with. For example the immune system of ducks and chickens are different as are the repertoire of receptors available to the virus on the surface of a chicken cell compared to aquatic birds.
As well as the many different subtypes of avian influenza virus there also exists the categorisation of highly pathogenic or low pathogenic strains. This different pathogenicity rating only exists for H5 or H7 viruses currently as these are the only subtype that can become highly pathogenic. All the other H subtypes of avian influenza virus are low pathogenic in nature. The definition of a highly pathogenic avian influenza virus is one that kills more than 6/8 infected chickens within 10 days when the virus is administered into the blood stream. High pathogenicity viruses have been characterised as having a specific motif in the H protein that allows their identification through sequencing alone. The H protein must be cleaved by a enzyme in the infected animal in order to be functional and allow entry of the virus into cells. Normally the enzyme that cleaves the H protein resides only in the respiratory tract or gut of the host species and therefore low pathogenicity influenza viruses are restricted to one or both of these locations. However this special motif in highly pathogenic viruses allows the H protein to be cleaved by a different enzyme found throughout all the organs of a host thereby allowing replication systemically. This motif is often generated when a low pathogenic version of a H5 or H7 virus infects a poultry flock. The reason for this mutation in poultry is unknown but it has been clearly demonstrated in multiple poultry flock outbreaks that the H in virus collected at the start of an outbreak are low pathogenic but at the latter stages this mutation has occurred and the virus is highly pathogenic. Highly pathogenic viruses have been transmitted back into the wild bird population and therefore they do circulate here but their generation is thought to occur only in infected poultry.
H5N1 is the most famous avian influenza strain and until recently is the subtype that the majority of the media refer to as “bird flu”. There are high and low pathogenic versions but the highly pathogenic version has been circulating in wild birds since 2003 unabated. It has caused ongoing devastating outbreaks in poultry flocks in Asia and the Middle East where it is endemically entrenched as well as sporadically causing Outbreaks in Europe and the Americas. During this time the H5N1 viruses have undergone evolution facilitated by the fact that influenza viruses have a quick mutation rate and the ability to mix the internal genes with other subtypes (reassortment). Therefore many different lineages of H5N1 circulate in different geographic locations, hindering vaccination control strategies by countries. H5N1 has also sporadically infected humans in areas where it is endemic. Infection of humans has occurred there has been very close contact with infected poultry and no transmission from one human to another has been evidenced. The current mortality rate of highly pathogenic H5N1 in humans is estimated as 58% according to WHO sources.
The most recent highly pathogenic H5 subtype virus to cause problems for the poultry industry globally is a group of viruses with the H and N combinations of H5N8, H5N6 and H5N2. They all have genetically related H5 genes. In 2014 H5N6 caused several severe outbreaks in poultry in China and Japan and also infected a human fatally. Subsequently H5N8 started causing outbreaks in poultry flocks of South Korea and was also found in wild waterfowl populations too. By late 2014 the H5N8 virus had made its way to Europe causing outbreaks on poultry farms in the Netherlands, Germany, Italy and UK. Migratory wild birds are thought to be responsible for the spread to Europe of this virus as the virus was subsequently detected in migratory wild birds in both the Netherlands and Germany and the timing of the outbreaks coincided with migratory patterns to Europe from South East Asia. From Europe this virus was spread across to North America again presumably through migratory pathways of wild birds where is caused out breaks and mixed up its genetics again to form the H5N2 subtype. Since early 2015 Canada and the USA have endured multiple outbreaks in poultry farms of these H5N8 and H5N2 viruses and they are causing serious economic problems for the industry there. These subtypes are also found in the wild bird surveillance that is carried out in North America. The rapid evolution of this group of influenza viruses has also meant that scientists have had to race to develop robust diagnostic tests to determine which strain of influenza is causing the different outbreaks.
H7N9 is a low pathogenic virus in poultry and wild birds circulating in China. It was first identified in 2013 from infected humans where the infection is actually a severe infection causing up to 30% mortality. Subsequent investigations of poultry farms, live bird markets and wild waterfowl also found the H7N9 virus in these populations. The virus does not seem to have spread outside mainland china, with infected cases of humans in other countries having spent recent time in China where their infections originated. There is no conclusive evidence that H7N9 can transmit between humans and close contact with infected birds in any of the settings above is required. The Chinese government has attempted several interventions to prevent the transmission of H7N9 to humans in China including culling of wild birds and shutting the live bird markets for periods of time.
H7N7 is a subtype of avian influenza that can exist as a high or low pathogenic version, the high pathogenic viruses usually develop once introduced into a poultry flock and do not usually circulate in wild birds. H7N7 at different points in history has caused infections in birds, pigs, humans and horses. In 2003 there was the biggest outbreak of H7N7 in poultry to date in the Netherlands, involving multiple farms and resulting in the culling of 30 million birds. Sporadic small outbreaks of H7N7 subtype influenza viruses have been detected since 2003 in Europe.
H9N2 is an interesting subtype of avian influenza virus, it is low pathogenic in nature for birds but is widespread and considered endemic in South East Asia and the Middle East and as such is a serious economic burden for the poultry industry in those areas. Like H5N1, H9N2 has evolved rapidly in birds and there are several different lineages of the virus circulating in different geographies. H9N2 viruses have infected humans sporadically again through very close contact with infected poultry but the disease symptoms in humans are reported as mild. There may well be more unreported, asymptomatic cases of humans. H9N2 is known to undergo the reassortment process (mixing of genetic segments) with other subtypes of virus very readily. H9N2 internal genes have been found in many avian influenza strains that have infected humans including H5N1, H7N9 and H10N8 and scientists are investigating if there are unique properties of the H9N2 genes that make viruses containing them more likely to infect mammals.
In the past 10 years there have been several incidences of H5 or H7 avian influenza in the UK (Table 1). These were all robustly controlled by DEFRA through the UK policy of movement restrictions and culling of infected and associated flocks of poultry. There have also been a couple of other low pathogenic subtype infections of birds in the UK which don’t get as much attention as these are not notifiable to the OIE (World Organisation of Animal Health) as H5 and H7 infections are.
The main risk of transmission of avian influenza viruses into UK poultry farms is through association with wild waterfowl. This can be actual contact with wild birds or contact with secretions (droppings and contaminated water sources). Physical transfer of the virus by farm workers is also possible from outside contaminated sources into areas where poultry are housed. Influenza in the correct humidity and temperature environments or protected by other proteins that are found in bird secretions can survive up to 72 hours as infectious virus. Precautions against these exposure routes should be taken seriously.
The risk of transmission of avian influenza virus to those who work with poultry is low. There are many barriers for an avian virus to overcome in order to effectively infect humans. These include differences in the virus entry receptors, differences in body temperature that can affect the efficacy of the viral proteins and differences in the immune system of humans and birds. Some strains of avian influenza virus find it easier to cross these barriers than others. However what is clear is that direct exposure to infected poultry which are excreting high doses of virus is required to facilitate any transmission that occurs unlike human influenza that circulates annually and can be easily transmitted through the air. Protection of farm workers through normal hygiene (washing of hands and no touching of the face after handling poultry) and personal protective equipment (gloves, facemasks and eye protection) also reduces this risk dramatically. Outbreaks of influenza in UK poultry happen on an infrequent basis.
There are many research establishments in the UK who work on avian influenza including The Pirbright Institute in Surrey. Research around the big questions regarding avian influenza are tackled including:
• What viral genes increase infectivity, pathogenicity and transmissibility of a virus in bird populations?
• What characteristics does an avian influenza virus need to transmit to humans or other mammals including pigs and horses?
• How can we create novel diagnostics that decreases length of time required to confirm an outbreak in birds?
• How can broad protection avian vaccines be developed?
• What happens if anti-viral resistance develops in avian influenza viruses?
• Our work is funded by the UK research councils as well as the poultry industry and veterinary pharmaceutical industry.
Progress is being made on these topics which will enable better control strategies of the virus in farmed birds and help us protect the public from cross over infections by avian influenza viruses.
Dana Simpson DVM MRCVS, St David’s Poultry Team
We have unfortunately seen the return of Avian Influenza cases recently. Numerous cases of HPAI, mainly H5N1, have been confirmed in different parts of the UK and Ireland. 3km and 10km Temporary Control Zones have been put in place surrounding the premises.
The initial source of Avian Influenza is likely to come directly or indirectly from wild birds, particularly waterfowl. At present the virus is also being detected in bird species (e.g. Mute Swans, Curlews, Mallards) which are not migratory, this is highly indicative of secondary infection. There may also be wild birds who were infected previously and may not be showing clinical signs or mortality at present.
Spread between poultry premises is most often due to the movement of people, products, poultry manure or equipment. The virus can spread quickly between flocks if biosecurity is poor. The main risk is posed by people carrying infected faeces into the bird area. Good biosecurity measures such as a change of footwear or the presence of foot dips are just a number of steps that can be taken to help reduce the risk.
At present (17 November 2021) an AIPZ (Avian Influenza, Prevention Zone) is in place in GB and Ireland. The aim is to reduce the risk of transmission of Avian Influenza to poultry and other captive birds from wild birds or any other source. The AIPZ means all bird keepers, including pet birds and captive birds, are legally required to comply with the minimum biosecurity measures set out by the government. This is especially relevant if your birds are in a higher risk area.
Biosecurity measures include:
- Restricted access for non-essential people / visitors
- A change of clothing and footwear before entering bird enclosures
- Vehicles entering the site will need to be cleaned and disinfected prior to accessing the site. Limit these to essential vehicles only.
- Site vehicles need to be cleaned and disinfected regularly
- Enhanced vermin and pest control
- Disinfectant foot dips containing approved disinfectant at the advised concentration
- Prevention of access to standing water by the poultry and water ingress into the poultry holdings
For more information, please visit the website below where you can also find a biosecurity self-assessment checklist to help you identify any areas that may need improvement.
Avian influenza (bird flu) - GOV.UK (www.gov.uk)
It is highly recommended to register your poultry, even if only kept as pets, so you can be contact during an outbreak. This is a legal requirement in the UK if you have 50 or more birds. Poultry includes chickens, ducks, turkeys, geese, pigeon (bred for meat), partridge, quail, guinea fowl and pheasants. There is a text alert service available which can be signed up to by texting BIRDS to 67300.
Several confirmed HPAI cases in the UK at the start of the year had been attributed to either contact with wild birds or water ingress into the birds’ housing. The latter can occur through leaking roofs, cracks in the walls etc. Making sure the fabrication of the house/holding pen is sound and waterproof is essential.
It’s the small things that make all the difference so remain vigilant. For example, if a toolbox, bucket or other equipment has to be brought into the bird house for maintenance reasons, make sure it is thoroughly disinfected prior to entry. It can be dipped in the foot bath, wiped down with disinfectant wipes or sprayed with a hand spray containing alcohol/disinfectant solution.
It helps to keep extra boot covers / wellies and boiler suits on site in case of essential visitors entering the bird area.
Keeping a spare sprayer with disinfectant solution in the egg store for use after each egg collection to spray the area the ramp has touched down on and the trolleys have moved across can further help reduce any potential risks.
Keep all other non-essential vehicles out of the bio-secure area where possible.
There are a couple of strains of Avian Influenza known to be circulating in the UK at present. Early detection can help prevent further spread of the disease. It helps to familiarise yourself with some of the clinical signs of bird flu. In laying hens these tend to be increased mortality, diarrhoea, sick looking birds, respiratory distress, dark discolouration of the combs and a drop in production often with shell quality changes such as pale eggs and soft shells. Very early signs can be as insidious as a drop in feed or water consumption. It is important to remember that different strains can clinically manifest in a variety of ways and not all signs are present at the same time or in every affected flock. With that in mind it is best to speak to your veterinary surgeon if you have any concerns and they can advise on the best course of action if you suspect disease in your flock.
Should you find any sick or dead wild birds, keep any pets away and do not touch them. Notify the competent authority should you find any dead waterfowl or significant numbers of other birds.
Further details can be found in the DEFRA booklet online which describes what is expected of the bird keeper. www.gov.uk/guidance/avian-influenza-bird-flu
During the HPAI outbreak that occurred at the start of this year a housing order was brought into force by legislation as an aid for controlling the disease. Housing orders are enforced to protect the health and welfare of the birds. The housing order also aims to protect the economics of the industry.
Eggs can be marketed as free range for up to 16 weeks whilst the birds are being kept inside. In newly placed flocks this starts from the time the pullets are placed on the laying site, not when production starts.
In the event of a housing order there are challenges to overcome when a flock that is accustomed to being let out a certain time and ranging freely is suddenly kept in. If a proposed housing order has been announced, and you have a few days to prepare, then varying the times that the pop-holes are opened during that lead up period may give you an idea of how the birds will react and what you may have to do to mitigate against the effects.
Ventilation can be challenging in the winter months when the pop-holes are closed especially in naturally ventilated houses. Poor ventilation can adversely affect litter quality which in turn can lead to an increase in ammonia levels and associated health issues as well as proliferation of parasites such as coccidia and worms inside the house. In automatically ventilated houses the ventilation systems can be adjusted to prevent deterioration in litter quality and your ventilation consultant should be contacted for advice if required. Wet and badly capped litter should be removed from the house and the bedding material replenished frequently. Continue to monitor for worm eggs. If there is a cessation in the worm egg count service due to AI, routine worming should be considered during the housing period to mitigate any worm associated health and production issues.
Housing can induce stress which may lead to behavioural changes and aggression. Injurious feather pecking can develop and once this behaviour is established, it can be very difficult to control. Reducing the lux level of lighting within legal levels can be a useful tool in calming the birds and preventing bullying. Adequate enrichment should always be in place –especially destructible products such as alfalfa bales and pecking blocks. Grit given at 7g/bird/week sprinkled on the scratch area may help keep the birds occupied and helps keep litter friable as they scratch about to find the particles.
Smothering incidents were not as common during the last housing order as many had feared. However, it is advised to monitor the birds often, especially around the times when the pop holes would usually open and crowds of birds should be broken up by walking the scratch area. The placement of ramps or other objects which stop hens crowding in certain areas can help stop deaths due to smothering. Electric fences should only be used as a last resort and after discussion with your veterinary surgeon who may have to write a letter to allow for a derogation for use depending on the age of the flock.
Keeping the hens in increases infection pressure for diseases such as Infectious Bronchitis (IB) and can exacerbate any associated clinical signs. IB is a coronavirus and as we are by now all aware can spread more quickly in closed areas. The majority of flocks in the UK are vaccinated with live IB vaccines in lay and this should continue during any lockdown period by your usual method of application.
Using nutraceuticals in conventional flocks can help support the hens’ health and there are also solutions available for organic production systems. These can help especially if the birds are experiencing stress due to being housed. Please contact your veterinary surgeon for advice on suitable products and if you have any concerns about how your birds are reacting to being kept in.
House temperatures often rise due to the birds being housed, even in the winter months. This in turn will result in increased activity and proliferation of the red mite population in the house. Monitor the red mite levels in the house closely and speak to your veterinary surgeon about the best way to control the red mite population in your house.
Avian Influenza can cause serious bird health and welfare issues and have a devastating economic impact on poultry farmers. The views and opinions expressed in the article are just that, they are generic and may not be appropriate to your situation. Any actions taken in regard to AI must be done in discussion with the appropriate veterinary and government consultants and should be appropriate to your farm and specific situation.
| Date confirmed | Virus | Location, County | Description | Map | |
