Pacheco’s Disease

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    What Is Pacheco’s Disease?

    This is a disease that aviculturists should fear. It is caused by a filterable virus which has been classified as herpesvirus. One which you may all recognize causes fever blisters or cold sores about the mouth of humans. It is related to the dread Pacheco’s disease virus. Dr. G. Pacheco discovered Pacheco’s Disease (PD) during an epidemic of psittacosis (parrot fever) in humans which occurred in the United States and Europe in 1929-1930. In 1975, Pacheco’s Disease was diagnosed in Florida in parrot-like birds.

    Subsequently, this disease has been reported from multiple locations within the United States and from around the world, in countries where Central and South American parrots have been imported. PD is almost exclusively a disease of psittacine (parrot) birds. Nanday and Patagonian conures tend to be inapparent carriers of the disease.

    However, many species of parrot, including Amazon parrots and macaws, may also shed this virus. Some believe that any bird that has survived an outbreak of the disease should be considered as a possible carrier. In the last 10 years, it has become apparent that PD may be caused by more than one herpesvirus. Five PsHV subtypes have been isolated from birds with PD, which eventually cause acute liver failure.

    Signs & Symptoms

    Clinical signs include ruffling of the feathers, progressive weakness, nasal discharge, diarrhea, loss of weight, regurgitation of clear mucus, and nervous signs (tremors in the neck, wing and legs). Most diseased birds die suddenly without signs. When signs occur, they are not specific and resemble other systemic infectious diseases. Parrots with signs of disease seldom survive.


    Birds shedding Pacheco’s Disease virus should be immediately isolated. Cages, feeders, and all other contaminated surfaces must be disinfected with an oxidizer such as chlorine bleach. Pacheco’s virus is resistant to many disinfectants, including alcohol. Although blood tests can sometimes identify carrier birds shedding the virus, there are no reliable tests for the virus. Prophylactic treatment on susceptible birds includes continual dosing with B-complex vitamins.

    It has been suggested that birds at higher risk (such as in pet stores) should be given a vaccine. However, there were multiple side effects and a number of deaths associated with the vaccine. Some outbreaks show the failure of the vaccine prophylaxis that had been administered to the birds with ordinary commercial preparations containing Psittacid Herpesvirus type 1. Some experts emphasize the necessity of producing a vaccine containing inactivated viruses of all known serotypes.

    One should guard against adding any new birds directly into an aviary. It is recommended that isolation of at least 60 days be imposed on any new birds. Any stress could cause a carrier bird to break out into active disease. Within the isolation period, it is also recommended that the newly purchased bird be examined by an avian veterinarian and that various tests are run to screen for diseases. Treatment mostly consists of supportive care. Acyclovir, an antiviral medication, is thought to be helpful in reducing the severity of the outbreak and possible save exposed but not yet seriously ill birds.


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