ASK THE VET (Pacheco's Disease)

Pacheco's disease is caused by a herpes virus. This disease is dreaded by aviculturalists because it is very devastating and often fatal. It was first recognized in Brazil when birds started dying several days after becoming ill.

Different strains of herpes virus are believed to exist. A variety of birds may be infected, such as chickens, ducks, pigeons and psittaformes. Psittaciformes are most susceptible to the virus. Macaws, Amazons, African greys, cockatoos, budgies, cockatiels and conures are some of the species that can be infected. Patagonian and Nanday conures are frequently asymptomatic carriers. Any bird that survives an outbreak should be considered a "latent" carrier of the virus.

Infected birds may die suddenly or show nonspecific signs such as lethargy, anorexia, ruffled feathers, sinusitis and intermittent diarrhea. Urates may become green, indicating that liver damage has occurred.

The first sign of a problem often occurs when a seemingly "healthy" carrier bird is introduced into a collection and birds start to die suddenly. Any type of stress (e.g., breeding) can activate the virus and result in its being shed in large numbers in the feces. The incubation period is thought to be as short as several days in some of the smaller parrots.

The biggest problem is that there is no good antemortem test that can be used to detect the virus in a live, "healthy" carrier bird. Diagnosis is usually made on postmortem with virus isolation and characteristic histopathology changes. If an outbreak occurs, some people suggest using the human herpes medication Zovirax (registered trademark for acyclovir), given by gavage. Vaccination in the face of an outbreak is considered by some to be controversial, since handling may help spread the virus.

A vaccination using killed vaccine is available and can be given in a series of two injections, 4-8 weeks apart. Some species, such as cockatoos, have had vaccination reactions. Only birds with high risk of exposure, such as pet store birds, should be vaccinated.

Prevention is the best way to avoid an outbreak. Strict quarantine measures should be carried out. Some advise not to mix conures with Amazons, since conures can be asymptomatic carriers and serve as a source of infection for susceptible birds.