Proventricular Dilatation Disease
Encyclopedia
Proventricular Dilatation Disease is a disease affecting psittacines (Parrot
s). It was first recognized and described in 1978 by Dr. Hannis L. Stoddard. Since the first reported cases were involving species of Macaw
, the condition was termed Macaw Wasting Syndrome.
Gastrointestinal signs may include: Regurgitation, crop impaction, poor appetite, weight loss, or passage of undigested food in the feces.
Neurologic symptoms may include: Weakness, ataxia, paresis, proprioceptive deficiets, head tremors, and rarely seizures.
Muscle wasting and a generalized poor body condition is usually found as well. The virus can also affect the Purkinje cells of the heart, the adrenal medulla, the brain, and the spinal cord.
On necropsy the affected organs appear dilated and may include the crop, proventriculus, ventriculus, and small intestine. On histopathological examination the tissues will contain a lymphoplasmacytic infiltration in the peripheral and central nervous tissue. The causative virus is believed to commonly affect the myenteric plexuses which will also lead to the presentation of atrophied smooth muscle within the affected gastrointestinal organs. It is this atrophy and loss of tone in the organs that causes the dilation and subsequent gastrointestinal symptoms which are commonly the first sign of disease for the owners.
was able to identify the virus that may cause PDD, which they have named Avian Bornavirus (ABV). A member of the bornavirus
family, Avian Bornavirus was isolated in 71 percent of samples from infected birds, but in none of the healthy birds. The researchers were able to clone a full-length genome
of the virus from avian tissue, and analysis of that tissue revealed that there are at least 5 distinct varieties of the avian virus - not all of them cause PDD. This virus was also identified by Honkavuori et al. in multiple cases of PDD. Gancz et al. succeeded in inducing PDD in cockatiels by inoculation of brain tissue from ABV positive birds while Gray et al. caused PDD in Patagonian conures by inoculation of a tissue-culture derived isolate of Avian Bornavirus. Avian Bornavirus is the cause of PDD.
ABV is not the sole cause of PDD and testing should not be used alone to confirm or rule out PDD. There are still other suspected viruses and conditions that are considered risk factors to developing PDD. Detection of ABV does not mean that PDD will follow. The disease does not follow a clear path of development or transmission.
The presence of Avian Bornavirus
may be detected in two ways. Testing fecal samples does not offer a reliable answer at the virus degrades quickly outside the body. A blood sample may be tested for antibodies to ABV by western blot
or ELISA
. Antibody production occurs late in infection but tends to develop in association with clinical disease.
There are many false posatives and false negatives at this time.. Additionally, because of the high prevalence of ABV
Parrot
Parrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae , the Cacatuidae and the Strigopidae...
s). It was first recognized and described in 1978 by Dr. Hannis L. Stoddard. Since the first reported cases were involving species of Macaw
Macaw
Macaws are small to large, often colourful New World parrots. Of the many different Psittacidae genera, six are classified as macaws: Ara, Anodorhynchus, Cyanopsitta, Primolius, Orthopsittaca, and Diopsittaca...
, the condition was termed Macaw Wasting Syndrome.
Symptoms
The clinical presentation of this disease varies with the individual as well as in severity of those symptoms. Often the symptoms include a gastrointestinal component, but many times birds suffering from this disease will present with neurologic signs as well, or in lieu of digestive anomalies.Gastrointestinal signs may include: Regurgitation, crop impaction, poor appetite, weight loss, or passage of undigested food in the feces.
Neurologic symptoms may include: Weakness, ataxia, paresis, proprioceptive deficiets, head tremors, and rarely seizures.
Muscle wasting and a generalized poor body condition is usually found as well. The virus can also affect the Purkinje cells of the heart, the adrenal medulla, the brain, and the spinal cord.
On necropsy the affected organs appear dilated and may include the crop, proventriculus, ventriculus, and small intestine. On histopathological examination the tissues will contain a lymphoplasmacytic infiltration in the peripheral and central nervous tissue. The causative virus is believed to commonly affect the myenteric plexuses which will also lead to the presentation of atrophied smooth muscle within the affected gastrointestinal organs. It is this atrophy and loss of tone in the organs that causes the dilation and subsequent gastrointestinal symptoms which are commonly the first sign of disease for the owners.
Cause
In July 2008, a team of researchers at the University of California, San FranciscoUniversity of California, San Francisco
The University of California, San Francisco is one of the world's leading centers of health sciences research, patient care, and education. UCSF's medical, pharmacy, dentistry, nursing, and graduate schools are among the top health science professional schools in the world...
was able to identify the virus that may cause PDD, which they have named Avian Bornavirus (ABV). A member of the bornavirus
Borna disease
Borna disease is an infectious neurological syndrome of warm-blooded animals, caused by Borna disease virus, which causes abnormal behaviour and fatality....
family, Avian Bornavirus was isolated in 71 percent of samples from infected birds, but in none of the healthy birds. The researchers were able to clone a full-length genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
of the virus from avian tissue, and analysis of that tissue revealed that there are at least 5 distinct varieties of the avian virus - not all of them cause PDD. This virus was also identified by Honkavuori et al. in multiple cases of PDD. Gancz et al. succeeded in inducing PDD in cockatiels by inoculation of brain tissue from ABV positive birds while Gray et al. caused PDD in Patagonian conures by inoculation of a tissue-culture derived isolate of Avian Bornavirus. Avian Bornavirus is the cause of PDD.
Diagnosis
After an exam including radiographs the vet may ask for a follow up radiograph with a marker to collect more data in digestion to aid in confirmation od PDD. A tissue sample is a reliable method as well but invasive and therefore uncommon with live birds.ABV is not the sole cause of PDD and testing should not be used alone to confirm or rule out PDD. There are still other suspected viruses and conditions that are considered risk factors to developing PDD. Detection of ABV does not mean that PDD will follow. The disease does not follow a clear path of development or transmission.
The presence of Avian Bornavirus
Avian Bornavirus
In 2008, by pyrosequencing of cDNA from the brains of several parrots suffering from Proventricular Dilatation Disease , Honkavouri et al. identified the presence of a novel Borna virus .-Process of Discovery:...
may be detected in two ways. Testing fecal samples does not offer a reliable answer at the virus degrades quickly outside the body. A blood sample may be tested for antibodies to ABV by western blot
Western blot
The western blot is a widely used analytical technique used to detect specific proteins in the given sample of tissue homogenate or extract. It uses gel electrophoresis to separate native proteins by 3-D structure or denatured proteins by the length of the polypeptide...
or ELISA
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
. Antibody production occurs late in infection but tends to develop in association with clinical disease.
There are many false posatives and false negatives at this time.. Additionally, because of the high prevalence of ABV