Fowl pox

Occurrence: Worldwide.
Species affected: All.
Age affected: All.
Causes: Avian pox viruses are single, linear double stranded DNA viruses.
Effects: Incubation is from 4-10 days.There are two forms of the disease- cutaneous dry and diphtheritic or wet. Both may present in the same flock. The dry form is manifest as pimples or scabs on the skin (mainly on unfeathered parts of the body). The diphtheritic form shows cankers or yellow lesions in the mouth, oesophagus or trachea. Other symptoms include blindness, feed refusal, lowered egg production, facial swelling.

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Causes

Pox viruses are single, linear, double stranded DNA viruses which cause chronic disease in poultry of all species and age.

Mode of transmission

Mosquito bites and mechanical transmission of virus to lacerated skin or eye are common routes of viral spread. Wild birds are a reservoir for the viruses.

Clinical signs

Incubation period is from 4-10 days. They are two forms of the disease; the cutaneous or dry and the diphtheritic or wet. Both may be present in the same flock or animals.
The  dry form  shows  as  a  pimple  or  scab  on  skin  (mainly comb,  wattles,  eyelids  and  other unfeathered portions of the body).
The wet-mucous form shows diphtheritic, cankers or yellow lesions in mouth, oesophagus or trachea. Eye involvement (blindness), off feed, lower egg production, facial swelling and an increase in culls can be seen.

Fowl pox

Postmortem lesions

Cankers or false membranes in mouth (wet) are seen as slightly elevated white opaque nodules. Nodules increase in size and coalesce to yellow, cheesy, and necrotic membranes.
Grey  or  black  papular  eruptions  on  unfeathered  portions  of  skin  (dry)  are  due  to epithelial hyperplasia. Head, face, and feet are most commonly affected, but may spread to feathered portions of the body.

Diagnosis

Eliminate bacterial dermatitis. Virus isolation on CAM of embryos will produce plaques, which will reveal intracytoplasmic inclusion bodies. Gross lesions will reveal inclusion bodies. Presence of scales on skin and cankers in the mouth in the fall of the year is an important characteristic of the disease.

Treatment & control

Prevention
Vaccination in ovo with recombinant vaccines or in pullets by wing web puncture.