Chapter 34 Pansystemic Diseases
Pansystemic diseases are usually viral, bacterial, or fungal diseases that involve multiple body systems. These diseases are devastating to the bird and the owner, resulting in losses of pet birds and valuable breeding stock. Unlike with mammalian pets, few vaccines are available to protect avian species from these diseases.
Viral diseases of pet birds are common. Many of these viruses have a complex biology and are difficult to prevent and treat. Prevention of viral diseases involves quarantine and testing of all new additions to the household, limiting the number of species housed together, prepurchase examinations of all new birds, obtaining new birds from reputable breeders (avoid imported birds and previously owned birds), and common sense. Viral diseases may be subclinical in some birds but may cause disease in other species. Some birds may be carriers yet show no clinical signs of disease. Because disease may be unapparent, all new birds should be quarantined for a minimum of 60 to 90 days (this means in a separate room or facility, worked last for cleaning and feeding, etc.). A prepurchase examination including a complete blood cell count (CBC), serum chemistries, fecal tests, and Gram stains may identify birds with early signs of disease. Viral testing is available for some diseases that are species specific.
Avian polyomavirus disease (APVD) is a recognized cause of high nestling mortality in budgerigar aviaries. Affected birds are stunted and have dysplastic feathers, abdominal distension, hepatomegaly, and discolored skin. The disease may persist within the aviary from breeding season to breeding season. The disease also occurs in nonbudgerigar parrots. Macaws, conures, electus parrots, and ring-necked parakeets are most susceptible, but Amazons, cockatoos, and lories may also be infected. Most birds die suddenly as nestlings or young fledglings (2–14 weeks of age). APVD is endemic in many lovebird collections.
APVD is caused by a nonenveloped, double-stranded DNA virus capable of infecting numerous species of birds. The virus is shed in droppings and in feather and skin dander. The virus is capable of replicating in many tissues.
In the past, Pacheco’s disease has been seen predominately in aviaries or in quarantine stations that house imported psittacines. Infection of birds in pet shops and individual pet birds have also been reported, especially in birds that have been exposed to newly added conures (Patagonian, nanday, and mitred). The cause of the infection is an enveloped, double-stranded DNA herpes virus. The virus is shed in the feces and respiratory secretions of the infected bird. The incubation period is between 5 and 14 days. Birds may exhibit latent infections and shed virus when stressed. A vaccine is available but has not been well accepted in the United States because of the severity of vaccine complications (sudden death, vaccine granulomas). Other control measures that help to prevent infection include good management practices, testing of all new birds, and keeping a closed aviary.
Because of good quarantine procedures and the limiting of importation of all bird species, current outbreaks of exotic Newcastle disease are usually related to smuggled birds. The disease can be spread to poultry; previous outbreaks have been devastating for the poultry industry. Mexican and Central American parrots and fighting cocks are commonly implicated in outbreaks.
The disease is caused by an enveloped, single-stranded RNA virus (five strains of varying virulence and species specificity). Infected birds shed large amounts of virus in feces and respiratory secretions. Recovered birds can continue to shed viral particles for up to 1 year. The disease has been eradicated in the United States because of quarantine procedures; however, in states where smuggling of birds is common (e.g., southwestern states), the possibility of an outbreak of infection is always a concern. This is a reportable disease.