40. Duck viral hepatitises. Flashcards
1
Q
Occurrence and aetiology?
A
Duck hepatitis A virus (serotype I) - Notifiable x
Occurrence
- 1950 USA
- Worldwide
- 1962 Hungary
- History, etiology previously
- Serotype 1 ➝ now duck hepatitis A virus
- Serotype 2 ➝ now Astrovirus
- Serotype 3 ➝ now Astrovirus
- Duck hepatitis B virus ➝ Hepadnavirus
‣ Circular, dsDNA, enveloped
Etiology
- Duck hepatitis A virus
- Avihepatovirus genus
- 3 genotypes (serotypes)
- Genotype 1 ➝ highly pathogenic
- Genotypes 2 and 3 ➝ less pathogenic
• High resistance ➝ survives in bedding for 10 weeks)
2
Q
Epidemiology?
A
Epidemiology
- Shed in faeces for several weeks
- Infection
- Per os ➝ faeces
- Tracheal discharge
- No germinative infection
- Fast spread within flock
- Day old duckling
- Explosive, 90% morality
- If there is some yolk immunity ➝ slower (until the age of 2-3 weeks)
- 50% mortality
- Clinical signs in young ducklings (0-4 weeks)
- Mycotoxins, complications (Salmonella) can make more severe
3
Q
Pathogenesis?
A
Pathogenesis
- Per os infection
- Replication in the mucous membrane of the gastrointestinal tract
- Viraemia
- Liver, spleen, kidney ➝ replication
- Liver dystrophy, necrosis of hepatocytes, death - Long lasting immunity, yolk immunity (3-6 weeks)
- Secondary bacterial infection can happen ➝ Salmonellosis
4
Q
Clinical signs?
A
Clinical signs
- Clinical signs are seen in young ducklings (0-4 weeks of age)
- Incubation: 2-3 days
- Peracute ➝ large scale death within few hours
- Acute
- Depression, lethargic, ataxia
- Spasmodic paddling ➝ opisthotonus, hunched back
- Death within a few days
5
Q
Pathology?
A
Pathology
- Liver: enlarged, yellow, liver dystrophy, haemorrhages with sharp edges
- Spleen: enlarged, mottled
- Kidney: swollen, plethoric, nephrosis
6
Q
Diagnosis?
A
Diagnosis
- Epidemiology ʹ clinical signs ʹ pathology
- Histopathology
- Detection of the virus: PCR, IF, virusisolation
- Detection of Abs: VN, ELISA
7
Q
Differential diagnosis?
A
Differential diagnosis:
- duck hepatitis caused by astroviruses,
- duck plague
8
Q
Prevention?
A
Prevention and Prevention
- Treatment: none
- Prevention
- Epidemiological rules ➝ strict isolation in the first 4 weeks of age
- Vaccine
‣ Inactivated
๏ Vaccination of layers
๏ Booster needed
‣ Attenuated
๏ Layers and day-old ducklings, aerosol, drinking, SC injection
๏ Vaccination at the age of 7 weeks and 2-3 weeks before laying
๏ Homologous protection
‣ Attenuated + inactivated
๏ 7-12 week old ➝ attenuated vaccine
๏ 18 weeks old ➝ inactivated vaccine
