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Avian influenza is a disease primarily of birds but also affects some mammals. The influenza type A group of viruses causes the disease. There are many subtypes having a wide range of clinical manifestations—from a carrier status with no clinical disease in some wild ducks, to causing rapid death in commercial poultry.
In Australia the avian influenza viruses of major concern are the subtypes H5 and H7, with the H5 high pathogenic type being of central concern. To date, the highly pathogenic H5N1 virus has not been detected within Australia but could be easily introduced via migratory birds. Avian influenza H5N1 has been associated with human mortalities and has created a lot of concern. However, it must be remembered that this particular virus is principally a disease of animals and needs to undergo a complex mutation process before becoming an influenza virus of significant danger to humans. Hence the emphasis on strategically controlling this virus within the bird population. This has included the slaughter of poultry in regions where the disease has been detected and preventing contact between commercial poultry, domestic pets and wild birds. From present evidence it would appear that most human deaths associated with the present H5N1 virus have been due to circumstances where people have had close contact in the husbandry, slaughter or preparation for eating of infected birds.
Report suspicious events to the National Exotic Animal Disease Hotline on 1800 675 888.
- World Health Organisation
- In the Event of an Outbreak
- Victorian Department of Primary Industries
- Department of Health and Ageing
- Department of Agriculture and Fisheries
Every now and then, people comment on seeing the odd Sulphur-crested Cockatoo in a mob which has extensive feather loss around the head which sometimes extends to the body. In addition, the beak looks deformed and overgrown.
These sightings are not uncommon and during winter these birds become dependent on backyard bird feeders for their survival.
The condition is commonly known as Beak and Feather Disease or more technically Psittacine Circovirus Disease, after the virus group affecting parrots. While the disease is commonly noted in the Sulphur-crested Cockatoo it is known to affect a large number of the members belonging to the parrot, lovebird, lory and cockatoo families. In addition it has been suspected of affecting some non parrot species including the dove family but this still requires further investigation.
While the name Beak and Feather Disease would suggest that the virus relates only to these tissues it actually attacks the epithelium cells and many other tissues and organs in the body. It has three forms and these relate to the age that the virus affects the birds. In very young birds “neonates” the disease appears as septicaemia, enteritis or pneumonia and death is rapid. Birds at the fledging stage or first feather formation have a less rapid onset of the disease exhibiting signs of depression, diarrhoea and feather abnormalities but still results in death. The most observed chronic form is seen in older birds usually 6 -12 months of age undergoing their first and successive adult moults with increasing feather deformation and loss of powder down. Excessive beak growth and rotting is more common in cockatoos. Death is not sudden but progressive, taking 6 -24 months from the onset of clinical signs. The bird has a progressive inability to feed and is subject to secondary events.
The virus is spread in feather dust, faeces and crop tissue allowing transfer from adults to young during feeding.
This disease is widespread in the wild population of parrots and the chances of a bird surviving the disease and mounting an immune response depends on the route the virus enters the body and the dose level of the infecting virus. Other factors also play a role such as the age of the bird at the time of infection and if the mother has passed on maternal antibodies.
While the disease usually causes death in the wild some birds have been known to survive if nursed. The issue here is that the virus often persists within the liver and therefore the bird continues to excrete the virus when released back into the wild. Thereby posing a greater threat to other birds it comes in contact with.
Most established populations of parrots can handle the disease and in itself does not pose a threat to the species. However that is not the case for vulnerable parrot species where this disease may be the additional threat which places it into extinction. Hence research is focused on the development of a vaccine to assist the reestablishment of vulnerable species.
Diagnosis of the disease requires a few feathers and a couple of drops of blood to determine the presence and activity of the virus in the bird. A few other diseases can be confused with Beak and Feather disease causing the highly visible feather deformations but Beak and Feather disease is well established in the ACT and would be considered the most likely suspect disease in the majority of cases.
During the months of late March to September when the weather is starting to cool off. A number of juvenile birds particularly King parrots and Galahs are reported as suffering from a wasting syndrome.
The birds are weak and easily caught. They show signs of severe loss of body weight noted by the sharpness of the keel bone, normally not noticeable due to the surrounding chest muscles. In addition they have diarrhoea with green faeces adhering to the vent feathers around the cloacal opening. As this is a severe condition with a rapid onset some birds are simply found dead.
The disease is known as Spironucleosis after a small protozoan parasite which attacks the gut lining of mainly the small intestine but also parts of the large intestine. This results in the inability to digest food hence the resulting loss in body weight and diarrhoea.
It is assumed that the young birds are infected by sharing food from the adults. This in combination with the stress of cooler weather, weaning and a growing shortage of food through the winter, challenges the bird’s immunity and results in the disease.
Diagnosis can be confused with a number of other diseases including Aspergillosis, Salmonellosis, Psittacosis and Chlamydiosis. All of these diseases have symptoms with some similarities and are associated with small microscopic organisms. However Spironucleosis is seen every year within the ACT and should be high on the probable diagnostic list.
Spironucleosis can only be confirmed in a live bird by a microscopic examination of the faeces. Low powered microscopy with a darken field can detect these flagella protozoan organisms which resemble a tiny tadpole having a polar head and an active thrash tail. The faecal sample has to be taken and examined fresh because the organism once exposed to drying encysts into a small hard to recognise clear ball.
Successful treatment of these birds depends on rapid intervention and the prognosis depends on the initial extent of bodyweight loss. Treatment is initially intensive involving forced feeding and fluids. A warm environment and the use of anti protozoan medication such as dimetridazole or metronidazole are also required. Treatment programs can last from 7-14 days with a gradual increase in body weight increased appetite and cessation of diarrhoea. Carers are reminded to maintain a high level of hygiene when nursing these birds due to the high level of cross contamination caused by the droppings.