Voice Card  -  Volume 19  -  Drury Card Number 35  -  Sun, Mar 17, 1991 11:26 PM

Drury R., DVM

3. Recently I recieved a call from an individual who had purchased one of my domestic Blue Front Amazon babies a year earlier. The person stated that on routine exam her vet saw scarring in the mouth and indicated that the bird had previously had pox (virus). Neither my pair or it's offspring have any history of pox since in my possission ten years. My question is: Can Blue Front Amazon carriers pass the disease on to their young? Could the young have a mild enough case not to show any symptoms?

A: Before I address your excellent question, let me first describe what is known about the disease for those who maybe unfamiliar with pox.

Poxvirus infections are described in over 60 species of birds from 20 avian families. Studies indicate that the poxvirus is generally "host adapted" (causing disease in one species and not others) and is therefore placed into groups (ie. Canarypox, pigeonpox, quailpox, psittacinepox, etc.) based on the species it infects and on laboratory defined characteristics. This means that if your canaries have pox, their virus will not cause pox disease in your psittacines. Parrotpox (psittacinepox) is further divided into three catagories-Agapornispox (lovebird pox), psittacinepox (Amazon pox) and budgerigarpox. The relationship among these three poxviruses is still under research.

In the parrots there are two forms of the disease. The first one is the skin or dry form. The disease causes lesions (an injury) on the unfeathered areas (eyelids, around the beak, nares or nostrils, uropygial gland, the legs and feet) of the bird. If there are no secondary infections from bacteria or fungus, these lesions heal with little scarring. This skin form causes a mild disease with few deaths. The wet form or fibrinonecrotic form is much more severe, causing a high death rate. The lesions are in the mouth and esophagus, on the cornea of the eye, in the trachea and lungs, and under the eyelids (on the conjunctivia). Secondary infections are common with the wet form. In nonpsittacine birds, two other forms of the disease are described-a septicemic form and an oncogenic (cancer) form. At this time, these forms have not been documented in psittacines. The definitive diagnosis of pox infection is based on a biopsy or aspiration of the affected skin or mucosa (the lining of the respiratory and digestive systems) from the bird. The sample is examined microscopically. The lesions on the bird are similar in appearance to those caused by trauma, knemidocoptes mites, trichophyton (a fungal infection of the skin), trichomonas (a protozoan), candida, and vitamin A deficiency.

The virus is transmitted by mosquitoes, by the feces, skin, or feather quills of infected birds, and by objects (gloves, nets, towels, utensils) that have been in contact with an infected bird. Incubation takes about one to two weeks. For those birds that survive the disease, immunity lasts about eight to twelve months. There has been no documented evidence of carrier parrot birds. The virus is very resistant to many commonly used disinfectants and can remain in the environment for many years. Steam, 1% KOH, 2% NaOH and 5% phenol, are all effective for killing the virus. To answer your question, of the parrots, South American species (Macaws, Amazons, and Pionus) and Lovebirds are more susceptible to parrotpox. The Blue-fronted Amazon is especially susceptible to the disease. Given that your bird was a Blue-fronted Amazon and there was evidence of scarring in the month, I can understand why her vet suggested pox virus as the cause of the lesion. It should be very high on the list of diseases that can cause the exam findings. However, with the history YOU have provided, it does not seem likely that the bird had a pox infection while with you. As I mentioned before, there is no documented evidence of carrier birds, but remember, the virus can persist in the environment for years. It can also be spread by mosquitoes which is of concern for people with outdoor facilities near a pox outbreak. The disease can indeed be mild enough to show few symptoms, however Blue-fronted Amazons tend to become very ill.

For your own peace of mind, I would suggest having your birds vaccinated against pox disease. There is a very good KILLED pox vaccine for psittacine birds. Because the virus is killed, it CANNOT cause the disease. For those of you familiar with pox disease in other bird species, in some cases, we can use the poxvirus from one species as a vaccine to protect another species from the disease. Historically, cowpox (vaccinia) was used as a vaccine to protect people from smallpox disease. Unfortunately, poxvirus vaccines from nonpsittacine birds have not proven to protect psittacines from their disease. Therefore, to protect your parrot birds, have your vet use the correct vaccine.

Drury R., DVM