Occurrence and Economic Significance
The disease occurs in most countried with
warm and humid climates. Losses are
associated with a depression in growth rate although the infection does not result in
primary mortality.
Transmission
The virus is mosquito - borne. direct intraflock transmission by contact between infected and susceptible birds occurs.
Clinical Signs
Pink focl lesions occur on the comb and wattles
and non feathered portions of the body. there
foci enlarge to become 0.5 to 1.0 mm diameter, black and scab-like lesions, which persist for up
to two weeks followed by desquamation and healing.
Broilers may show confluent and extensive lesions
of the back especially in the slow-feathering males
of the auto-sexing strains. mild respiratory rales or (sounds) may occur in broiler flocks especially with suboptimal ventilation.
Pathology
Histological examination shows the
characteristic intracytoplasmic inclusion
of bodies in infected skin and tracheal mucosa.
The diphtheritic form is recognized by the
presence of nodular hyperplasia of the mucosa
of the pharynx and trachea. Dead birds may
show plugs of desquamated epithelium which
lodge in the glottis resulting in asphyxiation.
Diagnosis
The cutaneous lesions are characteristic. Histological examination of affected tissue
will confirm the presence of intracytoplasmic inclusions (B0llinger bodies) in the respiratory mucosa and skin.
Prevention
Immunization is recommended in epdemic
areas using a mild-attenuated avipox,
chicken-strain virus vaccine admisitered
at approximately 8 weeks of age.
In areas where early exposure occurs, the
age of vaccination can be advanced.
In some areas, broilers are routinely vaccinated against avian pox by subcutaneous injection at
day old age. the efficiency of this procedure is questionable based on evidence of maternal antibody infterference.
In areas where flocks are affected with vertically transmitted mycoplasmosis, adverse vaccine reaction can be avoided by administration of a pigeon-pox vaccine.
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