Psittacid Herpesvirus (Pacheco's Disease)
New Research Information on Pacheco's from R.A.L.
Research conducted by Dr. Phalen at Texas A & M combined with testing performed by Research Associates Laboratory has shown the following:
- DNA testing for birds infected with Pacheco's Disease Virus (Psittacid Herpes Virus - PsHV) detects
approximately 85% of carrier birds with one combined test consisting of choanal/cloacal swab and blood sample.
Accuracy improves to 95% of infected, non-clinically diseased birds with 2 tests, 30 days apart. This is
derived from Dr. Phalen's observations and monthly testing of carrier birds over a 2-year time period.
- For testing suspected carrier birds, submit whole, unclotted blood (heparanized) and a combined choanal
and cloaca swab. Swab and blood samples are tested together and charged as a single test.
- Viral shedding in carrier birds is much more frequent than previously thought. We detect PsHV in almost
every sample from carrier birds. One Double Yellow Headed Amazon quarantined for two years has yet to have
a negative test result!
- Birds that have become ill and survived a Pacheco's Disease outbreak are usually chronic carriers
of the virus. Wild caught, imported Amazon parrots and many Conure species are also commonly implicated carriers.
- It appears that, once infected with this virus, birds remain infected for extended periods of time and most
probably for life. Positive carriers have not been documented to revert to a negative status.
Positive: A positive blood sample confirms active infection, usually clinical. Extreme care must be taken with these birds. Most deaths occur 3 to 4 days post infection, shortly after the onset of clinical signs. Exposed survivors testing positive are considered infected for life. These birds may go on to develop other conditions, i.e., papillomas, carcinomas, and more. (Refer to current work at Texas A & M by Dr. David Phalen for updates.)
Low Level Positive: LLPs confirm infection. Unlike many other viruses, infected animals may or may not show clinical signs. As with positive blood results, these animals should be considered infected for life.
Negative: A negative blood sample does not rule out infection. Research has shown that most birds infected with Herpesvirus remain blood negative, but swab positive.
Swab Sample — Combined choanal/cloacal swab
Positive: A swab positive confirms active infection. Due to the nature of Herpesviruses, they prefer to "hide out" in the tissues and rarely circulate except during viremic episodes. These birds are actively shedding and should be housed accordingly. Most birds are considered at risk.
Low Level Positive: LLP swabs confirm active infection. Recent work has shown the Herpesvirus positive birds may continually shed at low levels for life. LLP swab birds should be treated as birds testing positive by swab.
Negative: A negative swab confirms no organism is being shed at the time it was taken.
Specimen of Choice: Swab
Combined choanal/cloacal swabs are the most accurate for detecting the presence of Herpesvirus. As this virus does not readily circulate in the blood, except during viremic stages, a blood sample may not detect it.
Swabs from liver and other organs provide the best samples. These swabs are excessively "hot," confirming disease.
Procedure is the same for all organisms (see above).