30. Duck plague, herpesviral disease of pigeons. Flashcards
Duck Plague history, occurrence?
Duck viral enteritis (Duck plague)
acute haemorrhagic disease of ducks & other waterfowl NOTIFIABLE DISEASE
History, occurrence
Netherlands 1920s ➝ mass mortality of ducks ➝ ‘duck adapted fowl plague’
- Bos (1942): differentiation from fowl plague (influenza)
- Jansen (1961-1968): characteristic of the virus
- Worldwide occurrence (Europe, North America, South-East Asia)
Duck Plague Causative agent?
Causative agent:
- AnHV-1, unassigned herpesvirus (unique genetic arrangement so not in a subfamily)
- 1 serotype, different virulence variants
- Anatidae susceptible ʹ duck, goose, swan etc.
Duck Plague Epizootiology, Pathogenesis?
Epizootiology
- Convalescent birds are lifelong carriers
- Wild ducks may plan an important role in the long-term spread of the virus
- Domestic ducks usually get infected an open waters (lakes) via the contact with wild ducks
- Virus is shed through nasal discharge and faeces ➝ contaminates the water
- The virulence of the strain, the species and density of the hosts, the weather and food availability influences the severity of the outbreak
- Layer ducks, adults more sensitive
- Morbidity: 100%, mortality: 15-25% (5-100%)
Pathogenesis
- Mainly oral infection
- Primary replication: bloody diarrhoea, rhinitis, conjunctivitis
- Viraemia
- Endothel damage of the blood vessels ➝ necrosis, haemorrhage, fibrin precipitation on the mucosa
Clinical signs of Duck Plaque?
Clinical signs
- Incubation period: 3-7 days
- Sudden and persistent increase in flock mortality
- Photophobia, conjunctivitis, eyelid oedema
- Loss of appetite, nasal discharge, increased thirst
- Droopiness, ataxia, tremors, soiled vents, watery or bloody diarrhoea
- Inactivity, floating on water
- Adult ducks may die in good conditions
- Ducklings ➝ dehydration, weight loss, blue beaks, blood-stained vents, changed voice
- Decreased egg production
- Dead males ➝ prolapsed penis
- Death within 4-6 days
Duck Plague Pathology?
Pathology
- Haemorrhages in various tissues and free blood in body cavities
- Petechial and ecchymotic haemorrhages on the heart (pain brush appearance), liver, pancreas, mesentery and other
organs
- Specific mucosal eruptions in the oral cavity, oesophagus, ceca, rectum and cloaca
- In the beginning elevated, yellowish, crustaceous plaques
- Later diphtheric pseudomembranes
- The mucosal lesions appear on the longitudinal folds in the oesophagus and on the lymphoid follicles of the intestines
- Lymphoid organs: necrosis and haemorrhages
- The liver is enlarged, brass colour with greyish pattern (dystrophy) and haemorrhage
- Clear, yellow fluid infiltrates and discolours the subcutaneous tissues from the thoracic inlet to the upper third of the
neck
- Ruptured yolk and free blood in the abdominal cavity of laying ducks
Diagnosis of Duck Plague?
Diagnosis
- Presumptive diagnosis based on disease history and lesions
- Definitive diagnosis: laboratory tests
- PCR, isolation
‣ From liver, spleen, kidney
‣ In cell cultures
‣ Innoculating the chorioallantoic membrane of 9-14 day old embryonate Muscovy duck eggs (Muscovy ducks are
more susceptible than White Pekin ducks)
- Immunofluorescence
- Serologic tests have little value in the diagnosis of acute infections
DD of Duck Plague?
Differential diagnoses:
- Duck viral hepatitis (age)
- Pasteurellosis ➝ identification of pathogen
- Necrotic and haemorrhagic enteritis ➝ haemorrhagic less common
- Trauma (non-epidemic)
- Drake damage and various toxicoses ➝ mycotoxins, mainly signs in the intestinal tract and liver
- Newcastle disease
- Avian influenza
- Fowlpox may cause similar lesions but are rarely reported in ducks
Control and Prevention of Duck Plague?
Notifiable disease!!: established cases should be reported to the appropriate regulatory authority!!
Control and eradication
- No treatment
- Contact with wild, free-flying waterfowl and direct or indirect contact with contaminated birds or material (free-flowing
water) should be avoided - Sporadic ➝ depopulation, removal or birds form the infected environment, sanitation and disinfection
- Epizootic ➝ vaccination and lifelong quarantine
- Immunisation
‣ Chicken-embryo-adapted, modified live virus vaccine
‣ In epizootic: ducks > 3 weeks of age ➝ twice within 2-3 weeks
‣ Layers: 4 and 8 weeks before laying season
‣ Ducklings ➝ age of 4 weeks
‣ Inactivated vaccine has also been developed
Pigeon Herpes Causative agent?
Pigeon herpes
- Disease of the upper respiratory tract, liver, pancreas and intestine of young pigeons
Causative agent
- CoHV-1, Mardivirus genus
- Worldwide occurring (Europe, North America, Australia, Iraq)
- Pigeons susceptible
Epizootiology, pathogenesis of Pigeon Herpes?
Epizootiology, pathogenesis
- Adult pigeons are non-symptomatic carriers
- Oral infection from mother, in yolk immunity period ➝ no clinical signs
- Infection from other birds, later during race ➝ airborne infection ➝ clinical symptoms
- Simultaneous infections (Chlamydophila, E. coli, Mycoplasma, Pasteurella) make the pigeons more sensitive
- Convalescent birds are latently infected ➝ periodic shedders (stress)
Clinical signs of Pigeon herpes?
Clinical signs
- Mainly in 2-6 month old pigeons
- Acute, serous conjunctivitis, rhinitis, pharyngitis, diarrhoea
- Fat eye/Herpes eye ➝ eyelid inflammation, the lower eyelid hangs a bit ➝ typical ‘dry’ in contrast
- Diphtheric, yellow plaques within the beak, oropharynx, oesophagus, and/or trachea, dyspnea
- Death within 3-4 days (10% mortality)
- Chronic: sinusitis, dyspnea, concomitant infections
‣ Trichomonas columbae
‣ Mycoplasma
‣ Pasteurella
‣ Salmonella
Pathology, Histopathology of Pigeon Herpes?
Pathology, histopathology
- Conjunctiva ➝ oedema, suffusions, pseudomembranes
- Liver ➝ enlarged, oedema tic
- Small intestine ➝ watery-bloody content, red mucosa
- Trachea, pharynx ➝ croupous inflammation, necrotic foci, erosions, pseudomembranes
- Trachea, liver cells ➝ nuclear inclusion bodies
- Pancreas, brains ➝ acute inflammatory processes
Diagnosis and DD of Pigeon Herpes?
Diagnosis
- Clinical signs
- Isolation: CAM, chicken embryo fibroblast cell culture
- PCR, IF
- Serology: VN, ilF
- Differentiation
‣ Newcastle disease ➝ CNS signs, laboratory testing
‣ Pigeon pox ➝ skin lesions
Prevention of Pigeon herpes?
Prevention: Immunisation
- Attenuated or inactivated vaccines with oil adjuvant
- Combined inactivated vaccines (+NDV, Chlamydophila psittaci, Salmonella typhimurium)
- Basic immunisation at 50 days of age and 14 days later
- Layers ➝ 3-4 weeks before laying season ➝ protected nestlings
