Introduction

Bird flu, also known as Avian Influenza, is a viral disease that can infect birds. There are a variety of stains, some of which cause the infected birds to not show any symptoms and some of that are fatal. The recognition of bird flu, its significance, how it can be identified and what to do if you do come across an infected bird is important because some strains are zoonotic, which means it can pass from an animal to a human.

As the virus is carried by birds, the potential for spread and mutations is great. There are over 10,000 known species of birds and they can be found in nearly every region on earth, with migration leading to the ability to cause greater chances of spread.¹ Influenza viruses are particularly good at adapting to survive in a variation of hosts and environments. This is why so many flu viruses have posed a problem globally to be controlled and managed.

The species of wild birds that seem most susceptible to the virus are waterfowl, gulls, and shore birds with the main domestic bird infections occurring in poultry.² The first time that the influenza virus was proven in wild birds was from Common Terns in 1961 in South Africa. However, it was initially discovered in domestic poultry in 1959,³ with evidence also suggesting that the influenza pandemic in 1918 may have had avian origins.¹

In the years since, there has been limited success in controlling and limiting the spread of the virus, until within the last 10 years when the effects seen have significantly affected both the wild population of birds and domestic birds. This has had repercussions on bird-related ecology, the economy, and more worryingly public health.

There are two main strains, which are known as LPAI (low pathogenic avian influenza) and HPAI (high pathogenic avian influenza). The differences will be covered in more detail later but as the HPAI strain has been shown to have an up to 100% mortality (meaning causing death) rate in birds, it needs to be taken seriously.¹

Common symptoms in birds

Symptoms in birds aren’t always obvious and it can be that a bird may carry the virus without outwardly showing any signs at all or they may be very subtle. It can also present in two different variations mainly affecting the respiratory or digestive systems, although other body systems can also show symptoms.²

Symptoms that may present relating to the respiratory system are:

• Coughing
• Sneezing
• Changes to breathing – this may look like the bird is gasping or the bird is having to put in more effort for each breath
• Nasal discharge
• Rattling noises with each breath

Any one of these symptoms or a combination of them can cause the birds to appear in distress. 

Symptoms that can present that involve the gastrointestinal system are:

• Diarrhoea – this may present as watery or green in colour
• Swollen abdomen
• Reduced appetite
• Sudden changes to water consumption

Symptoms that can also present that affect other areas of the body are:

• Lethargy/weakness
• Swollen head/twisting of head and neck
• Discharge from eyes/ closed eyes
• Drooping of wings
• Lack of coordination
• Fever
• Wattle and comb appearing blue and swollen – this is due to a lack of oxygen reaching these areas
• Bleeding/redness on the skin of the legs or neck
• Reduction or complete stop in egg production or change in the egg shells themselves
• Unconsciousness/sudden death

Sudden death can happen in birds that otherwise show no symptoms as mentioned above, this is typically the case when they are infected with HPAI.⁴

Differences between low pathogenic (LPAI) and highly pathogenic (HPAI) strains

LPAI (Low Pathogenic Avian Influenza) can present with no or only mild symptoms which may go undetected if the birds are not monitored closely. As it is commonly carried in wild birds, it will often go undetected. The symptoms may include only slight lethargy or mild respiratory issues.

Due to its presence in the wild bird population, there is the risk it can be passed on to domestic poultry. The big concern with this is that some variations of LPAI can mutate into HPAI, which has a much more severe effect on both the birds themselves and the eventual outcome of a flock.

HPAI (Highly Pathogenic Avian Influenza) This is usually much easier to spot in the infected birds as symptoms are more obvious and the effect on the bird is evident more quickly. Unfortunately, the likelihood of death is much greater with sudden death being commonly seen.

Research is still being carried out to find out how and why the mutation from LPAI to HPAI occurs, with the hope that with further understanding, more can be done to prevent it from happening.⁵ 

How the virus is spread

The virus can be spread through either direct contact with an infected bird or by its faeces, saliva, and mucous. Alternatively, it can be spread via a host animal that can act as a carrier from the infected bird and pass it on to another through similar contact methods.

This second method is rare but can happen. The length of time, volume of virus present and lack of protective measures can all make a difference to the likelihood of infection being passed on.⁶ 

Importance of early detection and reporting

Due to the increasing risk avian flu poses to public health, it is important to limit its spread. Recognising and reporting cases will help to do this. As wild birds are a key element in spreading the virus, making all people more aware of the signs and what to do when they notice an infected bird will help.

Authorities have protocols in place that will be carried out once they have been informed of a potentially infected bird. In the UK, any suspected cases of avian flu need to be reported to the government via the APHA (Animal and Plant Health Agency) as it has been designated a notifiable disease. This means that should anyone be suspicious of infection, they are legally required to pass this information on.

Once the APHA has been informed, they will take steps to clarify whether the virus is present such as by inspecting the bird/flock, implementing movement restrictions, or a controlled area. If infection is eventually confirmed, then it may be necessary for the involved birds to be culled and thorough cleaning and disinfection to be carried out.⁶ The CDC in America has a similar approach to the reporting of and dealing with birds suspected or confirmed to be infected with the virus, as do several countries around the world.

Alongside the efforts to limit the spread of the virus, there are also options available to help minimise the effect that the virus can have. Research is being done to produce vaccines and effective anti-viral medications which will help to reduce both the spread and the impact of the virus. However, good hygiene practices and biosecurity measures are the most significant factors currently that will make a difference in preventing spread.

Summary

As discussed here, the risk of avian flu developing into a more significant problem to not only birds but also to humans is more present each day. This is why it is so important that familiarity with the signs of infection, what action to take, and the potential impacts need to be more widely known among the general public.

If everyone who comes across birds out in the wild or works alongside them can recognise that a bird showing respiratory problems, lethargy, and changes to its body may be infected with avian flu then the chances of reducing spread are greatly increased.

As everyone will remember, in recent times, how quickly a mutating virus that can spread rapidly impacts the world, Everyone must contribute in any way they can to prevent it from happening again.