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Virus diseases (Diagnosis)
Virus diseases (Research)
Birds (Health aspects)
Tully, Thomas N.
|Publication:||Name: Journal of Avian Medicine and Surgery Publisher: Association of Avian Veterinarians Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 Association of Avian Veterinarians ISSN: 1082-6742|
|Issue:||Date: Dec, 2009 Source Volume: 23 Source Issue: 4|
|Topic:||Event Code: 310 Science & research|
|Geographic:||Geographic Scope: United States Geographic Code: 1USA United States|
An adult red-rumped parakeet (Psephotus haematonotus) was presented to the Louisiana State University School of Veterinary Medicine with clinical signs of lethargy, anorexia, and bilateral conjunctivitis. The bird was owned by a local breeder who had recently imported the bird from Europe, then quarantined it in south Florida before it was shipped to his residence.
On physical examination, the bird weighed 57 g and was in moderate body condition. A slit-lamp ophthalmologic examination revealed bilateral ulcerative blepharitis, after which a conjunctival swab sample was collected from the affected tissue. A blood sample was collected from the right jugular vein and submitted for a complete blood cell count (CBC). Results of the CBC revealed a mild monocytosis at 1.8 x [10.sup.3]/[micro]l (reference range for a related species, a rosella, Platycercus species: 0-0.3 x [10.sup.3]/[micro]l). (1) The bird was initially treated with oxytetracycline ophthalmic ointment (topical application OU q8h; Terramycin, Pfizer Animal Health, Exton, PA, USA), flurbiprofen (1 drop OU ql2h; Ocufen, Allergan, Irvine, CA), doxycycline (50 mg/kg IM once; Vibramycin, Pfizer, Capelle a/d IJssel, the Netherlands), and meloxicam (0.3 mg/kg PO ql2h; Metacam, Boehringer Ingelheim, Saint Joseph, CO, USA). Staphylococcus cohnii ssp cohnii was isolated from the conjunctival culture and was sensitive to doxycycline. The bird's ophthalmic condition slightly improved over the next 2 days. However, 4 days after presentation, the parakeet developed severe dyspnea characterized by tail-bobbing and open-mouth breathing. The patient was immediately placed in an oxygen cage. Thirty minutes after placement in the oxygen chamber, the bird was anesthetized with isoflurane to examine the glottis and trachea for possible causes of the sudden onset of respiratory distress. The parakeet was induced with a face mask, then intubated and ventilated while being maintained in a surgical plane of anesthesia. Transillumination of the trachea did not reveal any abnormalities or obvious foreign bodies. Soon after intubation, the bird started breathing better and recovered without complications. The bird was supported in an oxygen/critical care unit after recovery but died approximately 12 hours later. The next day, the breeder brought 3 more redrumped parakeets from his aviary that had died after exhibiting the same antemortem clinical signs as those described in the initial patient. All birds had bilateral conjunctivitis and blepharitis with thickened periorbital skin (Fig 1).
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Major clinical signs observed in the red-rumped parakeet patients were severe bilateral blepharitis, conjunctivitis, and dyspnea, and the apparent disease spread to other birds of the same species. Differential diagnoses for these cases included poxvirus infection, mycoplasmosis, chlamydiosis, and polyomavirus or herpesvirus infection. Gross postmortem examination revealed, other than the blepharitis and conjuctivitis, raised skin lesions and hemorrhages at the commissure of the beak in 2 birds, splenomegaly in 2 birds, hepatomegaly in 3 birds, and a thickened crop in 2 birds (Fig 2). Histologic examination of the eyelids and the periorbital skin revealed varying degrees of epidermal hyperplasia and necrosis among birds. Within all epidermal layers, a moderate number of keratinocytes exhibited ballooning degeneration of the cytoplasm (Fig 3). The periorbital skin of the bird initially presented, contained large numbers of septate fungal hyphae in the dermis, as well as multifocal colonies of coccobacilli. The fungus was not further identified but was morphologically consistent with Aspergillus species. Large eosinophilic intracytoplasmic inclusion bodies (Bollinger bodies) were also seen (Fig 3). In the birds exhibiting hepatomegaly and splenomegaly, extramedullary hematopoiesis and mild congestion were present in these organs. In one bird, the crop displayed a marked hyperplasia and necrosis of the mucosal epithelium with multifocal ballooning degeneration of the epithelial cells that also contained large numbers of intracytoplasmic inclusion bodies. Additionally, the epithelium was infiltrated by numerous pseudohyphae and yeasts consistent with Candida species and was overgrown with large numbers of bacteria. In another bird, a mild lymphoplasmacytic infiltration of the proventriculus and ventriculus was observed along with the presence of a small number of Macrorhabdus ornithogaster on the mucosal surface. A third bird had severe necrosis and epithelial hyperplasia in the trachea and terminal bronchi. Multifocally, the epithelial cells contained intracytoplasmic inclusion bodies (Fig 4). In these 4 cases, gross and histologic lesions were consistent with poxvirus infection that included secondary bacterial and fungal infections in some of the submitted birds. The presence of internal lesions in the crop of one bird and the trachea and bronchi in another were consistent with the wet or diphtheritic pox form. Birds were negative for polyomavirus on the basis of polymerase chain reaction testing of tissue samples. Results of transmission electron microscopy on affected skin and crop tissues revealed large, electron-dense intracytoplasmic inclusion bodies that contained abundant virions (Fig 5). The virions were enveloped and measured approximately 300 nm in length and had brick-shaped nucleocapsids with a biconcave core. The viral particles were consistent with poxvirus.
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The clinical signs, epizootiology, and pathologic findings were highly suggestive of avian pox infection in these 4 red-rumped parakeets. Electron microscopic identification of viral particles in the lesions confirmed the diagnosis.
Avian poxviruses have a wide host range that include 278 bird species, of which 32 psittacine species have been reported with poxvirus infections. (2,3) One report has documented the infection in a red-rumped parakeet. (4) Several strains of Avipoxvirus, including psittacine pox, have been characterized by molecular methods. (2) An Agapornis pox antigenically distinct from the psittacine pox has also been suggested? Transmission can occur indirectly by mechanical vectors (biting insects) or directly by contact with infected birds and contaminated objects. (2,5) Three forms are commonly described: a skin (dry) form with cutaneous wart-like lesions on unfeathered skin, a diphtheritic (wet) form in which lesions can be found in the upper gastrointestinal and respiratory tracts, and a systemic form in canaries. (2,5,6) In this outbreak, a combination of skin and diphtheritic forms were observed.
In psittacine birds, poxvirus infections can occur as a single case (7-9) but are often associated with outbreaks and bird importation, especially in blue-fronted Amazon parrots (Amazona aestiva). (5,10) A recent outbreak report described a poxvirus infection involving 50 individuals, primarily lovebirds, in an aviary that housed redrumped parakeets, although the parakeets were not affected. (11) In this report, most of the birds had the cutaneous form of the disease but some diphtheritic forms also occurred (4 of 50).
Pathologic findings in our cases were typical of poxvirus infection with hyperplasia of the epithelium, ballooning degeneration of epithelial cells, and the presence of large eosinophilic intracytoplasmic inclusion bodies. (2,5) Secondary infections were also present on the eyelids of 2 birds and the crop of another. These secondary microbial infections often occur after inflammation and lesions of epithelial cells in avian pox cases. Although histopathologic lesions are highly suggestive of avian pox infections, further testing should be performed to obtain a definitive diagnosis of this viral disease. Viral isolation can be performed by inoculating the chorioallantoic membrane of avian embryos. (11) Demonstration of the poxviral particles by electron microscopy is another means of confirming the infection, and other specific molecular diagnostic techniques have also been used. (12,13)
No specific antiviral treatment is currently available for birds infected with poxvirus. Therefore, treatment should be directed against secondary bacterial and fungal infections and ocular lesions, if present. Vitamin A supplementation may be used to enhance the healing of the epithelium. The disease might be self-limiting in some birds, but uninfected birds should be protected from exposure to infected birds and potential vectors, primarily mosquitoes, to control the spread of the virus. (2)
This case was submitted by Hugues Beaufrere, Dr Med Vet, Manoj Bhaskaran, DVM, PhD, Gwendolyn Jankowski, DVM, Thomas N. Tully, Jr, DVM, MS, Dipl ABVP (Avian), Dipl ECZM (Avian), Leslie McLaughlin, DVM, PhD, and Nobuko Wakamatsu, DVM, PhD, Dipl ACVP, from the Department of Veterinary Clinical Sciences (Beaufrere, Jankowski, Tully) and Pathobiological Sciences (Bhaskaran, McLaughlin, Wakamatsu), School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
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