Fowl pox is a contagious disease of birds, caused by a member of family Poxviridae, characterized by wart-like nodules on the skin and diphtheritic necrotic membranes lining the upper digestive and respiratory system. Mortality is not usually significant unless the respiratory involvement is marked. The disease occurs in all age groups of birds and affects weight gain as well as egg production. The virus is highly resistant in dried scabs and under certain conditions may survive for months on contaminated premises. Pigeon pox virus and canary pox virus are the other two different but related strains that present similar clinical picture.
Fowl pox can be transmitted by direct or indirect contact. The disease may be mechanically transmitted by mosquitoes that may harbor infective virus for a month or more after feeding on affected birds. After the infection is introduced, it spreads within the flock by mosquitoes as well as direct and indirect contact. Recovered birds do not remain carriers.
Symptoms and lesions: Affected young birds are retarded in growth. Drop in egg production in laying birds is a constant finding. Birds with oral or respiratory involvement have difficulty in eating and breathing. The disease manifests itself in one or two ways, cutaneous pox (dry form) or diphtheritic pox (wet form). Dry pox starts as small whitish foci that develop into papules, pustules, pocks and scabs. The scabs eventually are sloughed off with healing if not complicated with secondary infection. Lesions are most commonly seen on the combs, wattles, feet etc. Wet pox is associated with the upper digestive and respiratory tract, particularly the mouth, esophagus, larynx and trachea. The lesions are diphtheritic in character and involve the mucous membranes revealing an ulcerated or eroded area.
Diagnosis: The clinical picture and lesions are adequately confirmatory. In some cases, laboratory diagnosis by virus isolation in chicken embryos or transmission studies is necessary.
Prevention and control: Disease can be prevented by biosecurity measures coupled with vaccination. In India, quality vaccine for fowl pox is available and used by wing web applicator that provides satisfactory immunity.