Avian Metapneumovirus, which used to be known as avian pneumovirus (APV) and avian rhinotracheitis (ART) virus, causes a severe infection in the respiratory tract system in turkeys. It is also associated with swollen head syndrome in broiler breeders and broilers. Chickens, turkeys, Guinea fowls, Muscovy Ducks and pheasants are mainly affected, with turkeys being considered the most susceptible to the disease.
Avian Metapneumovirus was first detected in 1978 in South Africa, and since the late 1970s, it has spread across the world but has not yet reached Australia.
The virus is a part of the genus (group of organisms in a hereditary or ancestral hierarchy) Metapneumovirus. It is part of the Pneumoviridae family – negative strand- RNA viruses. The spherical particles measure 100 to 500 mm in diameter. There are four subtypes of the virus (A to D). It is categorised by the attachment of glycoprotein also known as G-protein. G-proteins are proteins which have a bond to amino acid side-chains. It is suggested that subtypes A, B and D are more closely related to each other than subtype C. Subtype D was described in France but has not been reported since 1980.
Avian Metapneumovirus is considered to be highly contagious primarily through oral transmission in direct contact or contact with material that is contaminated. The spread of the virus depends on several factors including the standard of hygiene and biosecurity measures within the flocks.
The disease is not defined as zoonotic, and since the virus mainly affects the upper respiratory tract, the transmission of the virus is considered to be airborne.
Chickens, turkeys and ducks have developed clinical signs with various subtypes of the disease. Avian Metapneumovirus can affect birds of all age groups, with younger birds considered to be more susceptible to the virus.
The most common signs of Avian Metapneumovirus includes conjunctivitis, frothy eyes and serous ocular and nasal discharge. Other symptoms of the disease consists of sneezing, coughing, clogged nostrils and swollen infraorbital sinuses. The respiratory signs are followed by ruffled feathers, anorexia and depression.
It has been discovered that laying hens only suffer a mild respiratory infection, which can cause a drop in egg production by up to 70%.
The mortality rate once infected by the disease, can range from 1% to 50% in flocks, depending on the age of the bird and whether or not they are secondary infections. Birds without secondary infections can typically recover within seven to ten days, but birds that have secondary infections that are not taken care of properly, can suffer from the disease longer and may contract pneumonia, pericarditis or perihepatitis.
It is essential to use virus detection and serology (laboratory testing for antibodies) to diagnose Avian Metapneumovirus. In the early stages of catching the disease, it is important to obtain samples from the upper respiratory tract. With broilers, samples need to be taken before the sixth day of being infected by Avian Metapneumovirus. The most suitable samples for detection are choanal and tracheal swabs.
There is a growing amount of genome sequence data and access to sequencing techniques. Therefore, detailed characterisation of Avian Metapneumovirus strains can be conducted. Right now, sequencing approaches have not been able to identify host specific variations between strains. Detecting new subtypes of the virus may need new diagnostic tools to develop and become accessible.
Treatment and control
There are vaccines (reducing the virulence – ability to cause damage to a host – of a pathogen whilst keeping it viable) available across Europe, to control subtypes A and B, but there is a risk that live vaccine strains may revert to more virulent variants.
There are three main methods to treat your flock infected with Avian Metapneumovirus. These methods are:
- Oculo-nasal method
- Spray vaccination
- Drinking water vaccination (which is considered to be the least reliable method)
Inactive vaccines are often used as a booster shot for layer and breeder flocks after receiving live vaccines. If infected or healthy flocks were only given inactive vaccines, they would be partially protected from the virus. The most efficient and long-lasting protection is ensuring that the flock has been given a combination of live-attenuated vaccines and inactivated vaccines.
Improving biosecurity measures can reduce the likelihood of introducing an infection, and should it take hold, helps to restrict the spread of it. Livetec offers bespoke solutions to protect livestock and enhance biosecurity measures. The Biosecurity Advisory Service consists of experts on hand to support clients in optimising biosecurity on farms.
Advice from Livetec
Livetec are leaders in biosecurity. We construct tailored plans to mitigate the risk of infectious diseases like Avian Metapneumovirus, from entering and spreading across your farm business.
Our Biosecurity Advisory Service is unparalleled in providing you with real-time, actionable advice based on years of expertise. Our Biosecurity Advisors conduct a comprehensive, one-day on-site visit to assess your farm and provide a customised list of recommendations aimed at safeguarding your poultry and protecting your livelihood. Our goal is to help you optimise the biosecurity of your farm business to the highest possible standards.
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