Species differences in susceptibility to Polyoma virus are thought to exist. Macaws, Conures, Eclectus, African Greys and Amazons are thought to be very susceptible to infection.
Polyoma virus can be present in a carrier state, with adult birds appearing clinically normal until they undergo stress. One type of stress that can cause a latently infected bird to shed virus is breeding.
Increases in reproductive hormones -- oestrogen, progesterone, and testosterone -- are thought to have an effect on the immune system and may be responsible for the activation, multiplication and shedding of the virus.
Most commonly this is recognised in chicks in the nest. Swollen bellies, tremors, wobbly, abnormal feathers may be seen. Larger psittacine species may live longer and show diarrhoea or regurgitation. Classical infections seem to affect larger species at around 7 weeks of age and can kill within a few hours of the first signs. Adult birds are also affected. Signs resemble those of septicaemia and hepatitis.
Embryonic death or decreased hatchability can also be caused by Polyoma virus.
Please use or at the very least liaise with your avian vet. Interpreting what the test means to you and your birds and what if any action is required in your situation needs veterinary input. UDL can assist your vet but we cannot get involved with cases directly.
Blood is not a reliable source of virus, especially in carriers. We recommend a cloacal swab be taken. Then clip the swab end off into our sample tube, put the top on and shake well.
Detection of polyoma virus:
Postmortem detection of Polyoma is based upon finding viral intranuclear inclusion bodies in the liver, kidney, spleen, heart and feather follicles. Identification of the virus in a live bird can be very difficult. Early tests looked for the presence of antibodies or proteins produced by the body against the virus. These antibodies, however, may no longer be present in a bird that remains infected by the virus. No correlation exists between serum neutralizing antibodies and viral shedding. This means that a bird could have a negative antibody titre and still shed the virus, or a positive antibody titre and not shed virus.
Polyoma virus infection in young parrots was initially seen in parakeets (budgerigars) and called budgerigar fledgling disease (BFD). Adult birds with sickness due to Polyoma have been seen although more commonly they appear normal but shed the virus periodically from the body. The disease is most devastating in young birds and may occur in parent raised as well as hand raised birds.
The disease is caused by a non enveloped DNA virus and virtually all psittacine species are at risk. Polyoma virus has also been seen in finches.
The younger the bird the more severe the signs. The age and species of affected individuals result in a large variance of clinical signs.
CLINICAL SIGNS IN LARGER PARROT SPECIES
The only sign in larger parrots may be a healthy appearing hand feeding baby who drops over dead. Classical signs may include depression, lack of appetite, poor feeding response, weight loss, crop stasis, vomiting/regurgitation, diarrhoea, dehydration, bleeding under the skin or into the belly, trouble breathing, weakness in the legs, paralysis and polyuria (increased water in the droppings).
One case of a Macaw death was an 8 week old baby who appeared perfectly normal throughout his short life. He vomited on day 57 of life and fell over dead. A chronic form (long term) of polyoma virus infection shows weight loss, poor feather condition, reoccurring bacterial and fungal infections and long term low grade anaemia.
Clinical diagnosis traditionally was made from a combination of history, clinical symptoms, gross lesions on autopsy, histopathology from autopsy (this is when your vet "sends out" tissues to a lab for a pathologist to check for virus in body tissues. It is extremely important for these tissues to go to a laboratory familiar with Polyoma virus or it will be missed!).
UDL now offers sensitive and virus specific DNA swab tests for screening live birds by cloacal swab.
The following regular screening protocols are recommended:
1. Cloacal swabs to screen individual birds that are actively shedding virus. Negative results do not assure non-infective or non-carrier status because of variable and unknown factors responsible for intermittent viral shedding. Positive results mean only that there is viral DNA present in the submitted sample. This does not say clinical disease is present, but strongly suggests a carrier state.
2.A twice annual screening of breeding collections. Ideally swabbing just at the end of laying eggs is best, the birds are stressed by laying and this increases the chances of them shedding virus. Closed aviary protocols are important to follow. All birds in one location need to be screened and found negative and no new birds should be added to this location for any reason until they have had appropriate testing.
NO SPECIFIC ANTI-VIRAL TREATMENT IS KNOWN FOR POLYOMA VIRUS.
This makes testing and quarantine even more important. Some adult birds do survive with good supportive care, blood transfusions and antibiotics or antifungals as individual diagnosis may dictate. Baby birds with Polyoma virus die.
Egg transmission is believed to occur since virus has been found in 1 day old budgerigars. Artificial incubation will not prevent or control disease spread in an aviary. Contaminated faeces and aerosolized dust has been documented to transmit the virus.
Chicks that have protective level of antibody from the yolk sac may infect susceptible chicks in the same nursery. Repeated finding of the virus in crop washings and feather samples from persistently infected adults that are clinically normal is responsible for continued spread of the virus in the aviary. Respiratory secretions have also shown virus so that breathing the air is all that is necessary in theory to transmit the disease. Virus shed from the kidney and reproductive tract are also probable sources of infection.
All of the true means of infections, including length of viral shedding from carrier birds and factors that cause shedding to occur, are poorly understood. Polyoma virus is resistant to many environmental conditions, disinfectants and heat. Chlorine is effective in killing polyoma as are many commercially available disinfectants. Available from VET-ARK.
Violators of the closed aviary concept are the primary manner of introduction of disease into the aviary. In Polyoma outbreaks involving 33 different aviaries, 100% of the exposures were traced to the addition of new clinically normal breeders to an established breeding aviary.
Birds found to be shedding the virus or are suspected should be isolated and managed separately from non shedders. These birds can produce healthy offspring that are not carriers or clinically diseased, but the chicks from a carrier breeding collection should be raised in a separate nursery from the chicks from a non carrier group of birds. Euthanasia is inappropriate for most suspect carrier healthy breeder stock. Once a vaccine for Polyoma becomes available the need for DNA screening tests will decrease, however, closed facility management protocols should still be followed.
In an outbreak of Polyoma virus in a closed facility the following basic protocols have been suggested:
1. The aviculturalist should disinfect appropriately between individual clutches of babies while hand feeding. Care should be taken to make sure that hands, feeding instruments, scales, incubators, brooders and other potential fomites are included.
2 Immediately remove all visible affected individuals from the nursery, establishing a separate isolation nursery.
3. Minimize dust, feathers, and aerosolized particles from the nursery. Consider installing an air filtration system. Remove larger birds from the nursery that are capable of flapping their wings and stirring or aerosolizing viral particles, and isolate this group separately.
4. Disinfect the room appropriately. Flooring should be a non-porous material, such as vinyl, that can be cleaned easily.
5. Do not allow the introduction of new chicks or eggs to the diseased nursery. Establish an entirely new area for chicks that need to come in from the breeding aviary.
6. Question the appropriateness of antibiotic or other drug therapies that may be being administered.
7. Recommend strongly that all surviving babies be screened for Polyoma virus via DNA probe before release for sale.
1. Investigate the possible origin of the virus. Consider and recommend DNA probe screening and detailed history collection as potential tools to use in the investigation. Question the appropriateness of screening the flock during the time of the outbreak.
2. Do not condemn carrier birds. Carriers, or suspect carrier, should be isolated away from the rest of the breeding collection. These birds can raise healthy offspring that are non carriers. Do not intermix chicks or traffic between two nursery settings.
3. Disinfect or destroy nest boxes belonging to the suspected carrier parents at the end of the breeding season. Consider advising forced sexual inactivity for some species until next season.
4. Make sure that human and fomite traffic between the aviary and the nursery does not allow reintroduction of viral particles from the aviary to the nursery. Recommended are foot baths, protective clothing and disinfecting procedures at appropriate sites as a routine maintenance procedure.
Control or prevention of viral disease outbreak in a facility that is open and accepts young from outside is virtually impossible.
In an outbreak in a facility that is not practising closed concept management, the facility should be conceptually closed to introduction of new birds, and then basic closed facility protocols followed.
Adapted from: Seminars in Avian and Exotic Pet Medicine. Dr. Brian Speer, W.B. Saunders Co.
IT IS ALWAYS A SOUND IDEA TO PRE-SCREEN NEW BIRDS BEFORE ADDING THEM TO YOUR VALUABLE COLLECTION.
For free test kits or further information CLICK here