B307 - FOWL POX

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B307 - FOWL POX

Nature of the disease
Fowl pox is a viral disease of poultry due to a avipoxvirus from the family Poxviridae. The disease is slow spreading and is responsible for low production.
Classification
OIE, List B disease
Susceptible species
Chicken and turkeys
Distribution
Worldwide, it is also very present in the Pacific Region.
Clinical signs 
The disease is characterised by egg production drop off and late growth of young birds.

In the cutaneous form (dry pox) clinical signs include the development of proliferative lesions, ranging from small nodules to spherical wart-like masses on the skin of the comb, wattle and other unfeathered areas.

In the diphtheritic form (wet pox), clinical signs include slightly elevated white opaque nodules develop on the mucous membranes of the mouth and trachea. They rapidly increase in size to become a yellowish diphtheritic membrane.  Mortality can reach 50%.

Post-mortem findings 
Lesions occur on the mucous membranes of the mouth, oesophagus, larynx or trachea. 
Differential diagnosis 
Symptoms of the cutaneous form are easy to recognise, for the diphteric form, differential diagnosis may include:
  • Vitamin A deficiency
  • Respiratory diseases (Infectious Laryngotracheitis)
Specimens required for diagnosis 
Lesions can be submitted for histological observation or observation of virus by electron microscopy. DNA probes are also available to demonstrate viral genomic material.

Serological diagnosis is possible using virus neutralisation, agar gel immunodiffusion, immunofluorescence, or passive haemagglutination tests, enzyme-linked immunosorbent assay and immunoblotting.

Transmission   
The virus, abundantly present in the lesions is transmitted by contact to pen mates through abrasions of the skins. 

Mosquitoes and other biting insects can have a mechanical role in the transmissions.

Risk of introduction   
Where it is exotic fowl pox could be introduced by importation of live infected birds and poultry meat traded with skin on.
Control / vaccines  
Modified live fowl pox virus vaccines are available commercially. The use of vaccines is indicated in areas where the disease is endemic, or on premises where infection has been diagnosed.

Other aspects of disease control include hygiene practices and insect control (such as mosquito net). 

References
  • Fowl pox, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p. 1960-1962
  • Office International des Epizooties, 2002
  • SAVILLE P. South Pacific Commission, Fowl Pox, Animal Health Advisory Leaflet 1, Noumea 1994