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Viral Diseases
Viral Diseases
239
BIRDS
BIRDS
Viral Diseases BASIC INFORMATION DEFINITION Diseases caused directly or indirectly by the pathogenic action of a virus
SYNONYM Viral infection
EPIDEMIOLOGY SPECIES, AGE, SEX All species and ages and both sexes. Some are more prevalent in youngsters (circovirus, polyomavirus). GENETICS AND BREED PREDISPOSITION • Species have various susceptibilities to specific viral diseases:
Psittaciformes are more prone to herpesvirus (type 1, 2, or 3; Pacheco, Amazon tracheitis virus, internal papillomatosis), proventricular dila tation disease (see Proventricular Dilatation Disease) (PDD; bor naviruses), circovirus (psittacine beak and feather disease [PBFD]),
240 Viral Diseases polyomavirus, reovirus, adenovirus, paramyxovirus, togavirus. Falconiformes and strigiformes are most commonly infected with pox virus, adenovirus (falcon adenovi rus), herpesvirus (falcon herpesvirus, eagle herpesvirus, owl herpesvirus), paramyxovirus, influenzavirus, flavi virus (West Nile virus). Passeriformes are most often affected by poxvirus, herpesvirus, polyomavirus, paramyxovirus, cyto megalovirus, and circovirus. Columbiformes are mainly diag nosed with circovirus, adenovirus, herpesvirus, poxvirus, and para myxovirus. Anseriformes are more suscep tible to herpesvirus (duck plague virus), picornavirus (duck viral hepatitis), parvovirus (goose par vovirus infection), paramyxovirus (type I), and orthomyxovirus (in fluenzavirus). Galliformes are principally sus ceptible to retrovirus (avian leu kosis, reticuloendotheliosis virus), adenovirus (egg drop syndrome, marble spleen disease), herpesvi rus (infectious laryngotracheitis, Marek’s disease), birnavirus (Gum boro disease), influenzavirus, para myxovirus (Newcastle disease), and adenovirus. RISK FACTORS • Stress-associated immune depression (e.g., importation, poor nutrition, captive conditions) • Mixing of species from various origins, large groups of birds • Contact with latently or chronically infected birds • Lack of prophylaxis, hygiene, quarantine CONTAGION AND ZOONOSIS • All viral diseases are contagious, but contagiosity depends on the virulence and the mode of transmission. Conta gion from one species to another depends on the host range of the virus. Mosquito-borne viral diseases are less contagious from one bird to another. • Avian viruses reported to be zoonotic are avian influenza, Newcastle disease, West Nile virus, and other mosquitoborne encephalitis. GEOGRAPHY AND SEASONALITY • Mosquito-borne viral infections (pox virus, viral encephalitis viruses) are more prevalent during spring and summer. • Polyomavirus and PBFD seem to be more commonly diagnosed in pet psittacines in Europe than in North America. PBFD is also endemic in Australia. • Avian viral serositis and other types of avian encephalitis are restricted to
particular geographic regions of the United States. ASSOCIATED CONDITIONS AND DISORDERS • Systemic infection is common with viral outbreaks and with some specific avian viruses: circovirus (PBFD), polyomavirus (in particular, in budgerigar, lovebirds, lories, and cockatoos), influenzavirus (gallifor mes), and paramyxovirus (galliformes) are especially known for their devas tating effects. • Immune deficiencies associated with circovirus infection (psittacines, pigeons, canaries, geese) might pre dispose to a variety of secondary dis eases. Multiple viral infections (PBFD, polyomavirus, pigeon circovirus, and adenovirus) are not uncommon. • Feather abnormalities are common with PBFD and polyomavirus and have been reported with West Nile virus and herpesvirus. • Skin and mucocutaneous conditions are documented with poxvirus, her pesvirus (cloacal papillomatosis, foot lesions in macaws and cockatoos), and papillomavirus in African grey parrots. • Hepatitis (see Liver Disease): herpes virus, adenovirus, reovirus, polyoma virus • Gastroenteritis: PDD, herpesvirus, poxvirus (diphtheric and systemic forms), picornavirus, reovirus, para myxovirus, adenovirus • Cardiac disease: West Nile virus, poly omavirus, PDD, togavirus • Neurologic disorders: paramyxovirus (PVM1 in all birds, PVM3 in Neophema spp. and passerines), influenzavirus, PDD, togavirus, flavivirus, adenovirus • Nephritis: polyomavirus, adenovirus, herpesvirus, retrovirus • Ascites: polyomavirus, avian viral serositis (togavirus), systemic viral infection
CLINICAL PRESENTATION DISEASE FORMS/SUBTYPES • Acute infection and presentation • Chronic infection • Latent infection HISTORY, CHIEF COMPLAINT • Lethargy, anorexia, fluffy at the bottom of the cage • Labored breathing • Regurgitation, vomiting, change in droppings • Ascites, abdominal distention • Polyuria-polydipsia • Neurologic signs (see Neurologic Disease) PHYSICAL EXAM FINDINGS • Clinical signs or lesions are often non specific or pathognomonic for any viral diseases and may affect all organ systems.
• Neoplasia and masses are reported for herpesviruses (internal papillomatosis, Marek’s disease), retroviruses (avian leukosis), poxviruses, and papilloma virus (African grey parrots).
ETIOLOGY AND PATHOPHYSIOLOGY • Results of entry and replication of a virus within host cells: cytolysis, immune system stimulation or depres sion, oncogenicity, and latency • Transmission: oral-fecal route (adeno virus, herpesvirus, orthomyxovirus, paramyxovirus, polyomavirus, circovi rus, reovirus, PDD), respiratory secre tions (herpesvirus, orthomyxovirus, paramyxovirus, polyomavirus, PDD), vectors (poxvirus, togavirus, flavivi rus), direct contact with wounds or feather dust (poxvirus, circovirus, poly omavirus, PDD), contamination of eggs • Incubation period: short for most dis eases (3-12 days). Some viruses may take months to years to induce clinical disease (PDD, Marek’s disease, her pesviruses causing internal papilloma tosis, circovirus). Herpesviruses are well known for latent infections. • Clinical disease will depend on species susceptibility, the bird’s immune system, the presence of stressors, viral load, and the virulence of the agent.
DIAGNOSIS DIFFERENTIAL DIAGNOSIS • Bacterial, fungal, and parasitic infections • Other causes of gastroenteritis, hepa titis, neurologic symptoms, and sys temic diseases
INITIAL DATABASE • Complete blood count (CBC): normal to moderate heterophilic leukocytosis, lymphocytosis, monocytosis. Anemia and leukopenia are occasionally observed with some viral infections, in particular PBFD in African grey parrots. Reactive lymphocytes are occasionally observed on the blood smear. • Plasma biochemistry panel: depends on the organ affected. Dramatic increase in hepatic enzymes can be seen with acute viral hepatitis. Hyper globulinemia is an occasional finding. • Radiographs may show organomegaly (nephromegaly, splenomegaly, hepa tomegaly, proventriculus enlargement) and some fluid accumulation in peri cardial, hepato-peritoneal, and intes tino-peritoneal cavities. • Cytologic examination may be useful: fine-needle aspirates from poxvirus nodular lesions frequently show intra cytoplasmic inclusion bodies (Bol linger bodies).
Viral Diseases ADVANCED OR CONFIRMATORY TESTING
preferred technique for many viruses, including poxvirus, papillomavirus, adenovirus, reovirus, and PDD.
TREATMENT THERAPEUTIC GOALS • Stabilize and improve patient’s physi cal condition. • Limit systemic and local inflammatory reactions. • Affect the virus replication cycle. • Limit viral transmission. • Treat any secondary bacterial infections. • Provide symptomatic treatment.
ACUTE GENERAL TREATMENT • Provide supportive care: supplemental heat, humidity, oxygen, fluid replace ment, force-feeding • Medications Broad-spectrum antibiotics: TMS 60 mg/kg PO q 12 h, enrofloxacin 15 mg/kg PO q 12 h, amoxicillin/ clavulanate 125 mg/kg PO q 12 h Nonsteroidal antiinflammatories: meloxicam 0.3-1.0 mg/kg PO q 12-24 h Antivirals: acyclovir is useful in her pesvirus outbreak and active infec tion but seems ineffective in internal papillomatosis. Other antivirals against specific viral families may be tried, but data on their clinical effec tiveness are lacking. Interferons activate cells’ natural protection against virus infection: recombinant omega interferon (1,000,000 IU IM q 7 d for 3 wk), poultry gamma interferon
CHRONIC TREATMENT
is most often limited to symptomatic treatment.
POSSIBLE COMPLICATIONS Complications are related to progression of the infection and include death, latency, chronic infection, and develop ment of neoplasia. It is to be noted that internal papillomatosis seems to be asso ciated with pancreatic and bile duct car cinomas in the long term.
RECOMMENDED MONITORING • General health monitoring should be performed with regular physical exam ination, CBC, and biochemistry panels. • During the course of the disease, a bird should be retested. A positive bird may become negative and may be considered cured, and a negative bird may become positive if a previous sample was taken during the incuba tion period. Two positive tests several months apart may indicate a perma nently infected bird.
PROGNOSIS AND OUTCOME Depends on the course of the disease, the susceptibility of the species, and the bird’s immune response but may be death, recovery, latent infection, or chronic infection
PEARLS & CONSIDERATIONS COMMENTS It should be kept in mind that many viral infections remain subclinical in birds, and some may be persistently infected.
Chronic infection and latent infection may be challenging to treat; therapy
Viral Diseases Necropic feather stumps can be a sign of psittacine beak and feather disease. A biopsy of the affected area including the feather follicle should be performed. (Photo courtesy Jörg Mayer, The University of Georgia, Athens.)
BIRDS
• Serology: low sensitivity for peracute and acute infections; few serologic assays are validated for pet birds Enzyme-linked immunosorbent assay (ELISA) may be useful but has variable sensitivity depending on cross-reactivity between species of birds and chicken or availability of species-specific antibodies. ELISA is commonly used for poultry viral diseases. Virus neutralization assay is seldom an option for the veterinary practi tioner because of prolonged turn around time and technical difficulties. It is available for a few of the major psittacine viruses. Hemagglutination inhibition assay (HIA) is applicable only to viruses able to aggregate avian red blood cells; this test is commonly used in paramyxovirus, influenzavirus, and West Nile virus detection and typing. Complement fixation assay may be useful, but such assays lack valida tion in avian species. • Immunofluorescent assay (IFA) neces sitates that conjugates are available for pet bird species viruses. This test is offered, for instance, for reovirus and Pacheco’s disease. • Electron microscopy is relatively non sensitive and nonspecific and is not readily available. It may still be valu able for detection of viruses in fixed tissues for which no other tests are available. • Virus isolation techniques are expen sive and time-consuming. Therefore, their value is limited in clinical situations. • PCR detects nucleic acid fragments, has generally good sensibility and specific ity, and is more readily commercially available for virus detection. Accessi bility depends on the availability of specific primers. It should be kept in mind that viral nucleic acids detected from different sites have different diag nostic values. PCR is currently offered for PBFD, Pacheco’s disease, general herpesvirus, polyomavirus, West Nile virus, and avian bornaviruses. • Histopathologic examination is invalu able in detecting lesions induced by the virus, visualizing inclusion bodies, and explaining clinical signs. Many viruses induce specific microscopic lesions. Targeted biopsies obtained by endoscopy are the preferred choices. Immunohistochemistry can be used when specific antibodies are available. In situ DNA hybridization is also valu able to confirm the presence of spe cific viral DNA in tissues. Antemortem viral infection diagnosis by histo pathologic examination remains the
241
PREVENTION • The goals of prevention are to limit viral exposure and transmission and to detect subclinical infection. • Birds should be maintained in an adequate environment and should be properly fed. • A good hygiene protocol is mandatory in pet stores, collections, aviaries, or breeding facilities. Facilities and equip ment should be cleaned and disin fected regularly. • In and out should be controlled: visi tors, objects, animals; contact with wild animals should be minimized • Any new bird should be quarantined for at least 1 month and tested for the common viruses. Sick birds should
be isolated. Health monitoring and disease screening can also be performed. • Vaccines currently available for pet birds include polyomavirus, psittacine herpesvirus, canary poxvirus, and West Nile virus, but effectiveness may be inconsistent among species. Some other vaccines for major psittacine viral diseases are in development.
Phalen DN: Avian viral diagnostics. In Fudge AM, editor: Laboratory medicine: avian and exotic pets, Philadelphia, 2000, WB Saun ders, pp 111–124. Ritchie BW: Avian viruses, function and control, Lake Worth, FL, 1995, Wingers Publishing.
CLIENT EDUCATION
Proventricular Dilatation Disease Polyomavirus Liver Disease Neurologic Disease
See Prevention.
SUGGESTED READINGS Greenacre C: General concepts of virology, Vet Clin North Am Exotic Pet Pract 8:1–6, 2005.
CROSS-REFERENCES TO OTHER SECTIONS
AUTHOR: HUGUES BEAUFRÈRE EDITOR: THOMAS N. TULLY, JR.
239
BIRDS
BIRDS
Viral Diseases BASIC INFORMATION DEFINITION Diseases caused directly or indirectly by the pathogenic action of a virus
SYNONYM Viral infection
EPIDEMIOLOGY SPECIES, AGE, SEX All species and ages and both sexes. Some are more prevalent in youngsters (circovirus, polyomavirus). GENETICS AND BREED PREDISPOSITION • Species have various susceptibilities to specific viral diseases:
Psittaciformes are more prone to herpesvirus (type 1, 2, or 3; Pacheco, Amazon tracheitis virus, internal papillomatosis), proventricular dila tation disease (see Proventricular Dilatation Disease) (PDD; bor naviruses), circovirus (psittacine beak and feather disease [PBFD]),
240 Viral Diseases polyomavirus, reovirus, adenovirus, paramyxovirus, togavirus. Falconiformes and strigiformes are most commonly infected with pox virus, adenovirus (falcon adenovi rus), herpesvirus (falcon herpesvirus, eagle herpesvirus, owl herpesvirus), paramyxovirus, influenzavirus, flavi virus (West Nile virus). Passeriformes are most often affected by poxvirus, herpesvirus, polyomavirus, paramyxovirus, cyto megalovirus, and circovirus. Columbiformes are mainly diag nosed with circovirus, adenovirus, herpesvirus, poxvirus, and para myxovirus. Anseriformes are more suscep tible to herpesvirus (duck plague virus), picornavirus (duck viral hepatitis), parvovirus (goose par vovirus infection), paramyxovirus (type I), and orthomyxovirus (in fluenzavirus). Galliformes are principally sus ceptible to retrovirus (avian leu kosis, reticuloendotheliosis virus), adenovirus (egg drop syndrome, marble spleen disease), herpesvi rus (infectious laryngotracheitis, Marek’s disease), birnavirus (Gum boro disease), influenzavirus, para myxovirus (Newcastle disease), and adenovirus. RISK FACTORS • Stress-associated immune depression (e.g., importation, poor nutrition, captive conditions) • Mixing of species from various origins, large groups of birds • Contact with latently or chronically infected birds • Lack of prophylaxis, hygiene, quarantine CONTAGION AND ZOONOSIS • All viral diseases are contagious, but contagiosity depends on the virulence and the mode of transmission. Conta gion from one species to another depends on the host range of the virus. Mosquito-borne viral diseases are less contagious from one bird to another. • Avian viruses reported to be zoonotic are avian influenza, Newcastle disease, West Nile virus, and other mosquitoborne encephalitis. GEOGRAPHY AND SEASONALITY • Mosquito-borne viral infections (pox virus, viral encephalitis viruses) are more prevalent during spring and summer. • Polyomavirus and PBFD seem to be more commonly diagnosed in pet psittacines in Europe than in North America. PBFD is also endemic in Australia. • Avian viral serositis and other types of avian encephalitis are restricted to
particular geographic regions of the United States. ASSOCIATED CONDITIONS AND DISORDERS • Systemic infection is common with viral outbreaks and with some specific avian viruses: circovirus (PBFD), polyomavirus (in particular, in budgerigar, lovebirds, lories, and cockatoos), influenzavirus (gallifor mes), and paramyxovirus (galliformes) are especially known for their devas tating effects. • Immune deficiencies associated with circovirus infection (psittacines, pigeons, canaries, geese) might pre dispose to a variety of secondary dis eases. Multiple viral infections (PBFD, polyomavirus, pigeon circovirus, and adenovirus) are not uncommon. • Feather abnormalities are common with PBFD and polyomavirus and have been reported with West Nile virus and herpesvirus. • Skin and mucocutaneous conditions are documented with poxvirus, her pesvirus (cloacal papillomatosis, foot lesions in macaws and cockatoos), and papillomavirus in African grey parrots. • Hepatitis (see Liver Disease): herpes virus, adenovirus, reovirus, polyoma virus • Gastroenteritis: PDD, herpesvirus, poxvirus (diphtheric and systemic forms), picornavirus, reovirus, para myxovirus, adenovirus • Cardiac disease: West Nile virus, poly omavirus, PDD, togavirus • Neurologic disorders: paramyxovirus (PVM1 in all birds, PVM3 in Neophema spp. and passerines), influenzavirus, PDD, togavirus, flavivirus, adenovirus • Nephritis: polyomavirus, adenovirus, herpesvirus, retrovirus • Ascites: polyomavirus, avian viral serositis (togavirus), systemic viral infection
CLINICAL PRESENTATION DISEASE FORMS/SUBTYPES • Acute infection and presentation • Chronic infection • Latent infection HISTORY, CHIEF COMPLAINT • Lethargy, anorexia, fluffy at the bottom of the cage • Labored breathing • Regurgitation, vomiting, change in droppings • Ascites, abdominal distention • Polyuria-polydipsia • Neurologic signs (see Neurologic Disease) PHYSICAL EXAM FINDINGS • Clinical signs or lesions are often non specific or pathognomonic for any viral diseases and may affect all organ systems.
• Neoplasia and masses are reported for herpesviruses (internal papillomatosis, Marek’s disease), retroviruses (avian leukosis), poxviruses, and papilloma virus (African grey parrots).
ETIOLOGY AND PATHOPHYSIOLOGY • Results of entry and replication of a virus within host cells: cytolysis, immune system stimulation or depres sion, oncogenicity, and latency • Transmission: oral-fecal route (adeno virus, herpesvirus, orthomyxovirus, paramyxovirus, polyomavirus, circovi rus, reovirus, PDD), respiratory secre tions (herpesvirus, orthomyxovirus, paramyxovirus, polyomavirus, PDD), vectors (poxvirus, togavirus, flavivi rus), direct contact with wounds or feather dust (poxvirus, circovirus, poly omavirus, PDD), contamination of eggs • Incubation period: short for most dis eases (3-12 days). Some viruses may take months to years to induce clinical disease (PDD, Marek’s disease, her pesviruses causing internal papilloma tosis, circovirus). Herpesviruses are well known for latent infections. • Clinical disease will depend on species susceptibility, the bird’s immune system, the presence of stressors, viral load, and the virulence of the agent.
DIAGNOSIS DIFFERENTIAL DIAGNOSIS • Bacterial, fungal, and parasitic infections • Other causes of gastroenteritis, hepa titis, neurologic symptoms, and sys temic diseases
INITIAL DATABASE • Complete blood count (CBC): normal to moderate heterophilic leukocytosis, lymphocytosis, monocytosis. Anemia and leukopenia are occasionally observed with some viral infections, in particular PBFD in African grey parrots. Reactive lymphocytes are occasionally observed on the blood smear. • Plasma biochemistry panel: depends on the organ affected. Dramatic increase in hepatic enzymes can be seen with acute viral hepatitis. Hyper globulinemia is an occasional finding. • Radiographs may show organomegaly (nephromegaly, splenomegaly, hepa tomegaly, proventriculus enlargement) and some fluid accumulation in peri cardial, hepato-peritoneal, and intes tino-peritoneal cavities. • Cytologic examination may be useful: fine-needle aspirates from poxvirus nodular lesions frequently show intra cytoplasmic inclusion bodies (Bol linger bodies).
Viral Diseases ADVANCED OR CONFIRMATORY TESTING
preferred technique for many viruses, including poxvirus, papillomavirus, adenovirus, reovirus, and PDD.
TREATMENT THERAPEUTIC GOALS • Stabilize and improve patient’s physi cal condition. • Limit systemic and local inflammatory reactions. • Affect the virus replication cycle. • Limit viral transmission. • Treat any secondary bacterial infections. • Provide symptomatic treatment.
ACUTE GENERAL TREATMENT • Provide supportive care: supplemental heat, humidity, oxygen, fluid replace ment, force-feeding • Medications Broad-spectrum antibiotics: TMS 60 mg/kg PO q 12 h, enrofloxacin 15 mg/kg PO q 12 h, amoxicillin/ clavulanate 125 mg/kg PO q 12 h Nonsteroidal antiinflammatories: meloxicam 0.3-1.0 mg/kg PO q 12-24 h Antivirals: acyclovir is useful in her pesvirus outbreak and active infec tion but seems ineffective in internal papillomatosis. Other antivirals against specific viral families may be tried, but data on their clinical effec tiveness are lacking. Interferons activate cells’ natural protection against virus infection: recombinant omega interferon (1,000,000 IU IM q 7 d for 3 wk), poultry gamma interferon
CHRONIC TREATMENT
is most often limited to symptomatic treatment.
POSSIBLE COMPLICATIONS Complications are related to progression of the infection and include death, latency, chronic infection, and develop ment of neoplasia. It is to be noted that internal papillomatosis seems to be asso ciated with pancreatic and bile duct car cinomas in the long term.
RECOMMENDED MONITORING • General health monitoring should be performed with regular physical exam ination, CBC, and biochemistry panels. • During the course of the disease, a bird should be retested. A positive bird may become negative and may be considered cured, and a negative bird may become positive if a previous sample was taken during the incuba tion period. Two positive tests several months apart may indicate a perma nently infected bird.
PROGNOSIS AND OUTCOME Depends on the course of the disease, the susceptibility of the species, and the bird’s immune response but may be death, recovery, latent infection, or chronic infection
PEARLS & CONSIDERATIONS COMMENTS It should be kept in mind that many viral infections remain subclinical in birds, and some may be persistently infected.
Chronic infection and latent infection may be challenging to treat; therapy
Viral Diseases Necropic feather stumps can be a sign of psittacine beak and feather disease. A biopsy of the affected area including the feather follicle should be performed. (Photo courtesy Jörg Mayer, The University of Georgia, Athens.)
BIRDS
• Serology: low sensitivity for peracute and acute infections; few serologic assays are validated for pet birds Enzyme-linked immunosorbent assay (ELISA) may be useful but has variable sensitivity depending on cross-reactivity between species of birds and chicken or availability of species-specific antibodies. ELISA is commonly used for poultry viral diseases. Virus neutralization assay is seldom an option for the veterinary practi tioner because of prolonged turn around time and technical difficulties. It is available for a few of the major psittacine viruses. Hemagglutination inhibition assay (HIA) is applicable only to viruses able to aggregate avian red blood cells; this test is commonly used in paramyxovirus, influenzavirus, and West Nile virus detection and typing. Complement fixation assay may be useful, but such assays lack valida tion in avian species. • Immunofluorescent assay (IFA) neces sitates that conjugates are available for pet bird species viruses. This test is offered, for instance, for reovirus and Pacheco’s disease. • Electron microscopy is relatively non sensitive and nonspecific and is not readily available. It may still be valu able for detection of viruses in fixed tissues for which no other tests are available. • Virus isolation techniques are expen sive and time-consuming. Therefore, their value is limited in clinical situations. • PCR detects nucleic acid fragments, has generally good sensibility and specific ity, and is more readily commercially available for virus detection. Accessi bility depends on the availability of specific primers. It should be kept in mind that viral nucleic acids detected from different sites have different diag nostic values. PCR is currently offered for PBFD, Pacheco’s disease, general herpesvirus, polyomavirus, West Nile virus, and avian bornaviruses. • Histopathologic examination is invalu able in detecting lesions induced by the virus, visualizing inclusion bodies, and explaining clinical signs. Many viruses induce specific microscopic lesions. Targeted biopsies obtained by endoscopy are the preferred choices. Immunohistochemistry can be used when specific antibodies are available. In situ DNA hybridization is also valu able to confirm the presence of spe cific viral DNA in tissues. Antemortem viral infection diagnosis by histo pathologic examination remains the
241
PREVENTION • The goals of prevention are to limit viral exposure and transmission and to detect subclinical infection. • Birds should be maintained in an adequate environment and should be properly fed. • A good hygiene protocol is mandatory in pet stores, collections, aviaries, or breeding facilities. Facilities and equip ment should be cleaned and disin fected regularly. • In and out should be controlled: visi tors, objects, animals; contact with wild animals should be minimized • Any new bird should be quarantined for at least 1 month and tested for the common viruses. Sick birds should
be isolated. Health monitoring and disease screening can also be performed. • Vaccines currently available for pet birds include polyomavirus, psittacine herpesvirus, canary poxvirus, and West Nile virus, but effectiveness may be inconsistent among species. Some other vaccines for major psittacine viral diseases are in development.
Phalen DN: Avian viral diagnostics. In Fudge AM, editor: Laboratory medicine: avian and exotic pets, Philadelphia, 2000, WB Saun ders, pp 111–124. Ritchie BW: Avian viruses, function and control, Lake Worth, FL, 1995, Wingers Publishing.
CLIENT EDUCATION
Proventricular Dilatation Disease Polyomavirus Liver Disease Neurologic Disease
See Prevention.
SUGGESTED READINGS Greenacre C: General concepts of virology, Vet Clin North Am Exotic Pet Pract 8:1–6, 2005.
CROSS-REFERENCES TO OTHER SECTIONS
AUTHOR: HUGUES BEAUFRÈRE EDITOR: THOMAS N. TULLY, JR.