Bird - Herpes Virus Infection

General information

Herpes viruses are believed to cause two well-known diseases of parrots: Pacheco’s Disease and papillomatosis. The former is an acute disease and capable of causing rapid death. The latter is much more chronic but no less severe.

What are the signs of Pacheco’s disease?

Many species of birds are susceptible. Amazon parrots are very susceptible to the infection and usually die, whereas Nanday and Patagonian Conures seem to be resistant to the disease.

Unfortunately, there are no unique clinical signs specific for Pacheco’s disease. Some birds may show only a brief period of lethargy and appetite loss before dying, whereas others may have moist droppings and/or regurgitation of clear mucus. Many birds show no clinical signs and are found dead. Therefore, any sick bird could potentially be infected with Pacheco’s disease. Pacheco’s disease should be considered as a possible cause of death in any bird found suddenly dead, especially if there were no clinical signs preceding death and the bird is in good body condition. A history of recent contact with imported conures is suggestive of this infection.

How is Pacheco’s disease diagnosed?

Due to its insidious (subtle) nature, diagnosis prior to death of the bird is not always possible. If the bird has died, the virus can be detected in the liver, kidneys, intestines, or faeces. When Pacheco’s disease is diagnosed after death, which is often the case, it is extremely important to treat other exposed birds.

How is Pacheco’s disease treated?

Since birds with Pacheco’s disease often die suddenly, treatment is not usually effective. An antiviral drug, acyclovir, can reduce death rates in other exposed birds; however, acyclovir is expensive and can be difficult to administer to birds.

Can Pacheco’s disease be prevented?

Some birds, such as Nanday and Patagonian Conures, carry the virus but never become ill. These species should be housed separately from other species of birds. If you have a bird which died from Pacheco's, the environment should be thoroughly disinfected and faeces should be properly disposed of to prevent transmission to other birds. Vaccination may be possible in certain situations though the vaccine must be imported on a named patient basis.

Papillomatosis

This is especially common in Amazon parrots and macaws. Herpesvirus has been isolated from infected birds and it is believed that these birds are survivors or chronic carriers of Pacheco’s Disease.

The signs consist of masses or thickenings (papillomata) in the gut. The mouth and cloaca (vent) are most commonly affected. These can be become very large and may cause obstruction or difficulty eating.

On occasion papillomata will become secondarily infected.

The worst sequel is the occurrence of malignant bile duct carcinoma (cancer) in some of the birds.

Surgery can be used to remove or debulk the papillomata. However, this may not always be possible especially for the more diffuse forms in the cloaca. Even where surgery is possible it should be viewed only as a palliative (to relieve not cure) measure – masses will return or recur in other parts of the gut.

Chemotherapy does not appear effective, though some birds may do well for a considerable period with palliative care.

Preventive measures are difficult as the causes are not exactly known. However, with the likely link to Pacheco’s then the measures suggested above may be useful. However, vaccination will play a lesser role.