Polyomavirus and Budgies

Polyomavirus goes by a number of other names, the most recognised name being Budgerigar Fledgling Disease or Papovavirus. It was first reported in 1981 in the US and Canada ( but probably was in aviaries long before this ). Although it was first seen in Budgies it is known to infect many birds worldwide, including other parrots, finches, canaries and poultry. What makes this virus interesting is that the same virus causes completely different symptoms in differing species.



Remember that we are talking about a virus. A very small particle that cannot move by itself, cannot multiply outside its host, but when it enters the host it can penetrate inside cells and cause severe damage. Viruses can be selective about which cells they enter, so symptoms vary depending on what organs are targeted by the virus. Because they enter cells, viruses are not susceptible to antibiotics, so recovery relies on the bodies own defense mechanisms. What we see as symptoms of the disease are the outcome of the battle between the virus and the host’s immune system. A really smart virus will live in the bird without causing disease but will multiply and shed viral particles so that other birds may be infected – this is what we refer to as carriers

Polyomavirus and Budgies

Infection with the virus causes the disease “ Budgerigar Fledgling Disease “. In an outbreak, 100% of birds in the aviary will become infected, but only the young will show symptoms. Young in the nest are most susceptible. Some will die suddenly, others will develop feather abnormalities and go on to die, some will develop feather abnormalities (become runners) and recover after the next moult and still others will show no symptoms of infection at all.

The disease sweeps through the aviary generally during a breeding season. It is most often introduced through a newly acquired breeding adult. Adults that have the virus and are shedding it into the environment look perfectly normal. The virus can be transmitted from bird to bird directly or from adult to young through the egg. There is no test available in Australia to detect carrier adults.

In the face of an outbreak the best thing to do is to stop breeding. This has two results – one it stops you having to cope with dead babies and runners, two it gives the adults a chance to develop some immunity to the virus. All remaining young birds should be culled from the aviary and adult breeders rested for at least 6 months. Although there may be some carriers left in the aviary when breeding starts up again we rarely see infected babies.

Polyomavirus in nonbudgerigars

In other birds we see a different looking disease but it is still caused by the Polyomavirus. Sudden death of nestlings and weanlings is the most common sign. These birds have a short illness that may cause depression, anorexia, weight loss, diarrhoea, regurgitation, crop stasis, and subcutaneous haemorrhage. If given a needle or a blood quill is pulled these birds may bleed profusely. Often they develop subcutaneous bleeding over the crop and on top of the head.
In hand reared babies the crop will stop emptying, small haemorrhages appear under the skin, the eyes will be partly closed and the skin will become pale. The baby will die within 12 to 36 hours. In a nursery all babies may be infected and the death rate can be as high as 80%. Cockatiels and Lorikeets appear particularly susceptible.

What to do to minimise the risk of introducing the disease

The concepts of the closed flock and quarantine must be understood and implemented in the aviary. To date very few Australian birdkeepers understand these concepts let alone do anything positive toward protecting their flocks.
The free movement of birds between aviaries without thought to disease spread means that the circulation of viruses within aviculture has been rapid. The boom in hand rearing has created the “contract rearer “ who takes in birds from several aviaries to rear at a central nursery – this must stop if these diseases are to be halted.

Article by Dr Tony Gestier
Featured in Talking Birds magazine June 2011