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I saw this article posted on another forum, thought I'd share it here.
[ A Bird Tale — Division of Research and Graduate Studies ]
A Bird Tale
BY ROMA SUBRAMANIAN
Itamar Villanueva is really interested in “the band.” However, this band is not a bunch of guitarists belting out rock songs but rather a horizontal strip of dark blue on a membrane.
The band represents the results of a test that Villanueva, a Ph.D. student who works in the Schubot Exotic Bird Health Center of the Texas A&M University College of Veterinary Medicine and Biomedical Sciences, has developed. The test has the potential to help diagnose proventricular dilation disease (PDD)—a fatal neurological disorder affecting captive parrots worldwide.
The test, which is the first of its kind, screens the serum of PDD-affected birds for antibodies produced in response to a specific antigen of avian Borna virus (ABV), the proposed causative agent of PDD. PDD is named for one of its symptoms: dilation of the proventriculus, an organ in the upper digestive tract of birds. The proventriculus secretes digestive enzymes and transfers food from the crop to the gizzard, where it is digested further. PDD damages the nerve supply to the proventriculus, ventriculus (gizzard) and portions of the small intestine. Food accumulates in the proventriculus, resulting in swelling of the organ. Common clinical signs include depression, weight loss, regurgitation and passage of undigested seeds.
As is often true in scientific discovery, a mixture of curiosity and serendipity led to the development of the test.
“I was working on a vaccine for influenza in chickens and had a little downtime and asked if I could observe the necropsy of a macaw that had died of PDD,” Villanueva says. He was curious to see whether the tissues of PDD-affected birds contained an antigen recognized by their own serum.
By using a technique called Western blotting (which uses a membrane to separate and identify proteins according to their size), Villanueva reacted the serum of PDD-affected birds against their own tissue proteins. He found that the serum almost always reacted against a 38-kilodalton (a Dalton is a unit of atomic mass) protein (the reaction appeared as a blue band on the membrane), indicating that the birds were producing antibodies specifically targeted against this protein. Serum from healthy birds did not react against this protein, indicating that only PDD-affected birds produced the protein.
Richard M. Schubot Professor of Exotic Bird Health and professor of immunology, Ian Tizard, leads the PDD research group in the Schubot Exotic Bird Health Center. Tizard says that the test shows in one step that PDD-positive birds have a PDD-specific antigen and are producing antibodies against that antigen.
Villanueva hopes that the test, which is currently about 90 percent accurate in detecting anti-ABV antibodies, will help prevent PDD misdiagnosis, which may result in the needless euthanasia of rare, expensive birds. The test is also an improvement over crop biopsy, another method to detect PDD. Crop biopsy is invasive, can give rise to complications and is only 60 percent accurate in diagnosing PDD.
The test is being offered as a free service to veterinarians to confirm its accuracy. It has also been submitted to the Office of Technology Commercialization at the Texas A&M University System to investigate its marketing potential. The Schubot lab is collaborating with Thomas Briese, associate director of the Center for Infection and Immunity at the Mailman School of Public Health, Columbia University, New York, to determine whether the PDD-specific antigen that Villanueva has isolated is the ABV nucleoprotein.
Although the test represents a step forward in understanding this complex disease, a maze of unanswered questions remains. For example, not all birds infected with ABV will develop PDD. Tizard says that “ABV is necessary but not sufficient for causing sickness.” Whereas some ABV-infected birds remain healthy for as long as 10 years, others become ill and die within two to three weeks. The trigger that leads to the development of PDD is not known. Also, although PDD is believed to be an infectious disease, its mode of transmission is not understood. Tizard illustrates the perplexing nature of PDD transmission by describing a case in which PDD developed in only one bird of a bird pair, even though the birds shared a cage and food for five years and even fed each other.
As is often true in scientific discovery, a mixture of curiosity and serendipity led to the development of the test.
To better understand the behavior of ABV, the PDD research group at the Schubot Center grew the virus in tissue culture. The group will collaborate with a research group at Columbia University to sequence the genome of the virus to determine its relatedness to other viruses. Tizard says that the goal is to develop “effective, practical treatments for PDD and, if possible, a vaccine.”
[ A Bird Tale — Division of Research and Graduate Studies ]
A Bird Tale
BY ROMA SUBRAMANIAN
Itamar Villanueva is really interested in “the band.” However, this band is not a bunch of guitarists belting out rock songs but rather a horizontal strip of dark blue on a membrane.
The band represents the results of a test that Villanueva, a Ph.D. student who works in the Schubot Exotic Bird Health Center of the Texas A&M University College of Veterinary Medicine and Biomedical Sciences, has developed. The test has the potential to help diagnose proventricular dilation disease (PDD)—a fatal neurological disorder affecting captive parrots worldwide.
The test, which is the first of its kind, screens the serum of PDD-affected birds for antibodies produced in response to a specific antigen of avian Borna virus (ABV), the proposed causative agent of PDD. PDD is named for one of its symptoms: dilation of the proventriculus, an organ in the upper digestive tract of birds. The proventriculus secretes digestive enzymes and transfers food from the crop to the gizzard, where it is digested further. PDD damages the nerve supply to the proventriculus, ventriculus (gizzard) and portions of the small intestine. Food accumulates in the proventriculus, resulting in swelling of the organ. Common clinical signs include depression, weight loss, regurgitation and passage of undigested seeds.
As is often true in scientific discovery, a mixture of curiosity and serendipity led to the development of the test.
“I was working on a vaccine for influenza in chickens and had a little downtime and asked if I could observe the necropsy of a macaw that had died of PDD,” Villanueva says. He was curious to see whether the tissues of PDD-affected birds contained an antigen recognized by their own serum.
By using a technique called Western blotting (which uses a membrane to separate and identify proteins according to their size), Villanueva reacted the serum of PDD-affected birds against their own tissue proteins. He found that the serum almost always reacted against a 38-kilodalton (a Dalton is a unit of atomic mass) protein (the reaction appeared as a blue band on the membrane), indicating that the birds were producing antibodies specifically targeted against this protein. Serum from healthy birds did not react against this protein, indicating that only PDD-affected birds produced the protein.
Richard M. Schubot Professor of Exotic Bird Health and professor of immunology, Ian Tizard, leads the PDD research group in the Schubot Exotic Bird Health Center. Tizard says that the test shows in one step that PDD-positive birds have a PDD-specific antigen and are producing antibodies against that antigen.
Villanueva hopes that the test, which is currently about 90 percent accurate in detecting anti-ABV antibodies, will help prevent PDD misdiagnosis, which may result in the needless euthanasia of rare, expensive birds. The test is also an improvement over crop biopsy, another method to detect PDD. Crop biopsy is invasive, can give rise to complications and is only 60 percent accurate in diagnosing PDD.
The test is being offered as a free service to veterinarians to confirm its accuracy. It has also been submitted to the Office of Technology Commercialization at the Texas A&M University System to investigate its marketing potential. The Schubot lab is collaborating with Thomas Briese, associate director of the Center for Infection and Immunity at the Mailman School of Public Health, Columbia University, New York, to determine whether the PDD-specific antigen that Villanueva has isolated is the ABV nucleoprotein.
Although the test represents a step forward in understanding this complex disease, a maze of unanswered questions remains. For example, not all birds infected with ABV will develop PDD. Tizard says that “ABV is necessary but not sufficient for causing sickness.” Whereas some ABV-infected birds remain healthy for as long as 10 years, others become ill and die within two to three weeks. The trigger that leads to the development of PDD is not known. Also, although PDD is believed to be an infectious disease, its mode of transmission is not understood. Tizard illustrates the perplexing nature of PDD transmission by describing a case in which PDD developed in only one bird of a bird pair, even though the birds shared a cage and food for five years and even fed each other.
As is often true in scientific discovery, a mixture of curiosity and serendipity led to the development of the test.
To better understand the behavior of ABV, the PDD research group at the Schubot Center grew the virus in tissue culture. The group will collaborate with a research group at Columbia University to sequence the genome of the virus to determine its relatedness to other viruses. Tizard says that the goal is to develop “effective, practical treatments for PDD and, if possible, a vaccine.”
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