63. Reoviral diseases of poultry.

Question 1

History and Occurrence?

Answer 1

Avian orthoreovirus infections ʹ Reoviridae, Spinareovirinae (WITH PROJ), Orthoreoviruses

History, occurrence:

• 1954: Fahey & Crawley: isolation from chronic respiratory disease
• World-wide distributed, all serotypes

Question 2

Epidemiology?

Answer 2

Epidemiology

• Susceptibility: mainly chicken, but turkey, goose, guinea fowl, Muscovy duck, quail pigeon, parrot
• & many other bird sp too
• Age-dependent resistance: over 10 days of age only infection but no signs
• Shedding with faeces & discharges
• Litter, fomites play a role in the transmission
• Resistant in the environment (20oC ʹ 1 year, 4oC ʹ 3 years!)
• PO, airborne, transcutaneous infections (injuries)
• Germinative infections!

Question 3

Pathogenesis?

Answer 3

Pathogenesis

1. Trypsin resistant strains; mainly PO infections, diarrhoea (frequent)
2. Trypsin sensitive strains: airborne or transcutaneous infections (severe)
3. Multiplication in the enterocytes & in the bursa fabricii
4. Epithel damage, viraemia -> inflammation of the tendon sheaths & joints necrotic and inflammatory foci in the visceral organs
5. Several strains can be isolated from clinically healthy birds too (orphan)

• Factors influencing the severity of the disease
• Age, sp. & breed of the host
• Immunological stage, resistance, immunosuppression (CAV, IBDV!)
• Virulence & biotype of the virus strain
• Infection route, titre
• Concomitant infections!

Question 4

Main diseases entities connected to avian orthoreoviruses?

Answer 4

Main disease entities connected to avian ortheoreovirus infections

A) Tenosynovitis ʹ arthritis

B) Enteritis, stunting disease, PEMS

C) Helicopter disease “Blue wing disease”

D) Malabsorption syndrome

E) Hydropericardium

F) Respiratory disease

G) Immunosuppression

Question 5

Tenosynovitis Clinical signs?

Answer 5

Tenosynovitis ʹ arthritis:

• Caused by certain serotypes, strains
• Co-infections: Mycoplasma synoviae, Staphylococcusspp.

Clinical signs

• Mainly in 4-8 week-old broilers (weight has role in clinical signs!)
• In poor kept, even seen in 15-16 weeks of age
• Lame, swollen knee/tarsal/MT joints (one or both), arthritis, haemorrhages under skin
• Deformed toes, swaying walking, paralysis-like signs
• Rupture of the m. gastrocnemius tendon (in roosters!)
• Swollen thoracic bursa, restricted body weight gain, weak feed utilisation
• Morbidity 5-50%, mortality 2-10%; in milder cases recover w/in 4-6days
• Frequent subclinical infections

Question 6

Pathology, Histopathology of tenosynovitis?

Answer 6

Pathology, histopathology

• Arthritis in the knee & metatarsal joints, swollen joints
• Deformed toes, haemorrhages on the synovial membranes over the joints
• Erosions on the synovial cartilage, fibrinous exudate in the hock joint & tendon sheaths
• Rupture of the m. gastrocnemius, enlarged diaphysis of the o. metarsalis
• Ankyloses, oedema, haemorrhages, heterophil granulocyte infiltration in the tissues
• Synovial cell hypertrophy & hyperplasia, villosus proliferation on the synovial membranes
• Scar tissues, fuse tendon & sheaths

Question 7

Diagnosis and DD of tenosynovitis?

Answer 7

Diagnosis

• Virus isolation: embryonated eggs (yolk sac, CAM), chicken liver cell culture: cell rounding,
• syncytia, cytoplasmic inclusion bodies
• Experimental infections of day-old chickens: inoculation of joints, muscles
• RT-PCR
• Serology: VN, AGID, ELISA

DDX:

• concomitant bacteria ʹ
• cultivation,
• adenoviruses

Question 8

Prevention and control?

Answer 8

Prevention, control

• Avoiding early (<2 week old) infections ʹ hygiene
• VACCINE: with appropriate vaccines!
• Attenuated, inactivated, combined vaccines
• Chicken with yolk immunity ʹ vaccination in the age of 5-7 weeks with attenuated
• strain, repetition in the 11th week
• Before the laying season (age 18-22 weeks) ʹ with inactivated vaccine (maternal immunity)
• Chicken w/out yolk immunity ʹ vaccination on day 1(Marek-disease vaccination competition of Atgs!)

Question 9

Generalised form?

Answer 9

B) Generalised form:

• Necrosis, inflammation & degenerative processes in the visceral organs
• Focal necrosis in the liver, liver dystrophy
• Pancreas-atrophy, pancreatitis
• Nephrosis
• Haemorrhages, perivasculitis in the brain stem
• Thymus-atrophy, lesions in the bursa of Fabricus & in the BM ʹ immunosuppression
• Myocarditis, ascites (in goslings)
• Hydropericardium ʹ in chicken, together with adenovirus

Question 10

Runting stunting syndrome and PEMS and Prevention?

Answer 10

Runting-stunting syndrome (RSS), poult enteritis & mortality syndrome (PEMS)

• Together with parvo-, adeno-, astro-, hepe-, cornoa-, enteroviruses
• Enteritis, diarrhoea, retarded development
• Feather, bone developmental problems, cartilage necrosis
• Enlarged intestines, watery content

Prevention:

• technology,
• hygiene,
• vaccinations