35. Fowl pox.

Question 1

Ethiology?

Answer 1

Avipoxvirus genus

Fowl pox

Avian poxviruses (Avipoxvirus genus)

Etiology

• Lesions on the skin and mucosa of domestic and wild birds
• Cytoplasmic inclusion body (Bollinger, 1873)
• Significant in
• Pheasant
• Turkey ➝ more severe
• Pigeon
• Fowl
• May be a problem in exotic birds (parrot, canary), more than 230 bird species
• Occurence: worldwide
• Cross infections of host species ➝ milder or no symptoms in heterologous hosts
• Cross immunity ➝ not all cases (viral antigen structures are not the same)

Question 2

Epidemiology?

Answer 2

Epidemiology

• In all ages (yolk immunity, recovery)
• Source of infection
• Recovered, carrier birds
• Shedding during the incubation period (before clinical signs)
• Mechanical transmission: litter, fomites
• Blood-sucking insects for weeks
• Wild birds and pigeons: more common in wet, rainy weather (mosquito activity)
• Fowl, turkey: more severe in fall and winter
• A-vitaminosis
• Mycoplasma
• Viral disease

Question 3

Pathogenesis?

Answer 3

Pathogenesis

• Homologous strains

1. Per os, inhalation, skin lesion
2. Primary asymptomatic replication at the site of entry
3. Viraemia
4. Organs, mucosa, skin in second replication cycle
   - If they survive
5. Second viraemia
6. Replication in skin (flourishing)

• Heterologous strains ➝ only primary replication

Question 4

Clinical signs?

Answer 4

Clinical signs

• Incubation: approximately 1 week

• Fowl, turkey, pigeon: 4-10 days
• Canary: 4-5 days

• Cutaneous form

• Local lesions on featherless areas
• Animals usually recover

• Diphtheric (wet) form ➝ malignant mucosal membrane

• Anorexia, lethargy, coryza, conjunctivitis
• Respiratory tract, oral cavity mucosal membrane ➝ nodules ➝ converge and covered with fibrin ➝ anorexia, wasting
• Death or recovery (secondary infections)
• Mixed form ➝ pocks on skin and mucosa
• Acute haemorrhagic (septicaemic) form ➝ rapid death without clinical signs (canarypox)
• Fowl: mainly diphtheroid form
• In immunised birds ➝ respiratory signs without nodules
• Turkey: diphtheroid form, infertile eggs
• Pheasant: respiratory signs
• Pigeon: diphtheroid form in young birds
• Parrot: rare, conjunctivitis, ulcers around eye, diarrhoea, necrotic ulcers in nasal cavity

Question 5

Pathology, Histopathology?

Answer 5

Pathology, histopathology

• Cutaneous form
• Proliferative nodules at the larynx ʹ may be obstructive
• Tracheitis, diphtheric membranes
• Body condition loss, degeneration of visceral organs, pulmonary oedema, enteritis
• Epithel-proliferation, oedema, cytoplasmic inclusion bodies

Question 6

Treatment and control?

Answer 6

Treatment and control

• Movement restrictions
• Improving general resistance (microclimate, feeding, vitamin supply)
• Antibiotic treatment against bacterial (mycoplasma) co-infections
• Vaccination (natural infections do not result in homologous herd immunity) ʹ most flocks are
• immunised in the first few weeks of age (only really seen in backyard chickens)

Question 7

Prevention?

Answer 7

Prevention

• Avoid introduction - closed farming, quarantine, exclude wild birds, arthropod control
• Preventive vaccination
• Chicken, turkey, pheasant: live, attenuated fowlpox virus; inject into the skin of the wing,
• check after 1 week
• Turkey ʹ inject into the skin of the neck
• Usually in 3 months-old of age; sometimes in younger (6-8 weeks old) ʹ repeat 2 months
• before laying period
• Pigeon: attenuated pigeonpox vaccine: inject into the skin of the wing or rub into feather follicles

Question 8

Diagnosis and differential diagnosis?

Answer 8

Diagnosis

• Symptoms, post mortem
• Isolation (Bollinger), EM, IHC

• DD:

• ILT (infectious laryngotracheitis),
• Mycoplasma