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Pacheco's Disease

By: Dr. Branson Ritchie

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Diagnosis In-depth

Pacheco's disease should be considered in any bird that dies suddenly with no signs of illness, particularly if some stressful event has occurred in the past three days to two weeks. Pacheco's disease should also be considered in birds that die shortly after developing clinical signs that include depression, anorexia, diarrhea (which may or may not contain blood), regurgitation and yellow-green urates.

Most cases of Pacheco's disease are suspected when viral factories called inclusion bodies are seen in the cells of the liver using a microscope. The disease is definitively diagnosed using viral specific DNA probes are by culturing the virus from infected tissues.

Other Tests

  • Your veterinarian may use radiographs (X-rays) or changes in the types of blood cells (CBC) or enzymes found in the blood (blood chemistry) to evaluate the overall health status of a sick bird.

  • The most common radiographic change associated with PDV is an enlarged liver. However, this radiographic change can also occur from other causes.

  • The most common changes in the blood are a substantial increase in liver enzyme activity and a decrease in the number of white blood cells. These blood changes can also occur from other causes, which is why specialized testing of swabs of the choana and feces and/or serum will be necessary to determine if an active PDV infection is occurring.

  • Until the site of viral persistence has been documented, use of an antibody detection assay is likely to remain the best test for screening clinically normal birds to determine if they have previously been infected or vaccinated. A virus neutralization assay is the most commonly used antibody test. Because PDV causes a lifelong infection, demonstrating that an unvaccinated bird has an antibody titer suggests that the bird has survived an infection and the bird should be considered latently infected. If detecting antibodies in an unvaccinated bird will be used to make life changing decisions for the bird, then it is important to repeat the test to make certain that some laboratory error did not occur.

  • Confirming an active case of PDV is best achieved by combining tests that detect antibodies against the organism with tests that demonstrate that PDV is present in a sample. Tests to detect the presence of the virus include culture and DNA probe-based assays (PCR). These tests are most valuable in birds with suggestive clinical signs, since they are most likely to be shedding PDV from the respiratory and/or gastrointestinal tract. Culture remains the gold standard for documenting the presence of PDV in a clinical sample. However, culture is problematic, time-consuming and expensive in comparison to other tests. If a swab for DNA probe-based testing or culture is not slimy after sampling the choana and not coated with excrement after sampling the feces, then the sample is of poor quality.

  • Currently, there is no test that can be used to confirm that a bird does not have PDV.

    Therapy In-depth

    Acyclovir has been shown to reduce the severity of herpesvirus infections and to decrease the number of deaths in an outbreak. This drug and related compounds would be expected to be most effective when treatment is started before a bird develops clinical signs of disease. This drug has been linked to kidney damage in some species and should only be used when necessary and under the supervision of an avian veterinarian.

    In birds with active signs of disease, your veterinarian may choose to administer acyclovir by either an intravenous or subcutaneous route. If you have birds that have been exposed but that are clinically normal, your veterinarian is likely to give acyclovir through a crop tube. If a flock is being treated, your veterinarian will instruct you on how to add acyclovir to the food and/or water.

    Other therapies that may be needed include fluids to correct dehydration and supportive nutrition if the bird has not eaten for several days or has lost considerable weight.

    Once acyclovir therapy has been initiated, it is important to start vaccinating. The acyclovir should help reduce the number of birds that will die while the vaccination program should help provide long-term protection of uninfected birds.

    Follow-up Care

    Optimal treatment for your companion bird requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your bird does not rapidly improve.

    Make certain you administer all prescribed medications at the appropriate time intervals. Contact your veterinarian immediately if you are having difficulties treating your bird as prescribed. If you are having problems, it may be best to hospitalize your bird to assure that a proper course of treatment is administered.

    Any bird suspected of having Pacheco's disease, that has been exposed to birds with PDV or that is being treated for PDV should be isolated from other birds to prevent transmission. The common practice of placing a hospital or "sick" room in the same building or airspace with a psittacine nursery is NOT recommended.

    As with most viruses, organic debris such as blood, soil, nesting material or feces would be expected to protect PDV from disinfectants that do not contain detergents. Caretakers should always wear a dust mask when handling the waste of birds. To reduce dust, use a misting bottle filled with disinfectant to moisten excrement and feather debris before handling. PDV can be inactivated with household bleach and most common disinfectants.

    Deaths should stop within two to three days after starting acyclovir therapy. If deaths continue, you should contact your veterinarian.

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