Transcript Lecture 25

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Pox is a slow-spreading disease
characterized by the development of discrete
nodular proliferative skin lesions on the
nonfeathered parts of the body (cutaneous
form) or fibrino-necrotic and proliferative
lesions in the mucous membrane of the
upper respiratory tract, mouth, and
esophagus (diphtheritic form). A concurrent
systemic infection may also occur.
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Avian poxviruses (fowl, turkey, pigeon,
canary, junco, mynah, psittacine, quail,
sparrow, crow, peacock, penguin, alala,
apapane, condor, and starling) are members
of the genus Avipoxvirus of the Family
Poxviridae. FPV is the type species of the
genus.
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Poxvirus infection occurs through mechanical
transmission of the virus to the injured or
lacerated skin. Individuals handling birds at
the time of vaccination may carry the virus on
their hands and clothing and may
unknowingly deposit the virus in the eyes of
susceptible birds.
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Incubation period of the naturally occurring
disease varies from about 4—10 days in
chickens, turkeys, and pigeons and is about 4
days in canaries.
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The disease may occur in one of the two
forms, cutaneous or diphtheritic, or both.
The signs vary depending upon the
susceptibility of the host, virulence of the
virus, distribution of the lesions,and other
complicating factors.
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The cutaneous form of the disease is
characterized by the appearance of nodular
lesions on the comb, wattle, eyelids, and
other nonfeathered areas of the body.
Cutaneous eye lesions will interfere with the
bird’s ability to reach food and water.
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In the diphtheritic form (wet pox), cankers or
diphtheritic yellowish lesions occur on the
mucous membranes of the mouth,
esophagus, or trachea with accompanying
Coryza-like mild or severe respiratory signs
similar to those caused by infectious
laryngotracheitis virus infection of the
trachea.
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Lesions in the corner of the mouth, on the
tongue, throat, and upper part of the trachea
interfere with eating, drinking, and breathing.
In pullets coming into lay and in older birds,
the disease often runs a slow course
accompanied by unthriftiness and reduced
egg production.
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The characteristic lesion of the cutaneous
form of pox in chickens is a local epithelial
hyperplasia involving epidermis and
underlying feather follicles, with formation of
nodules that first appear as small white foci
and then rapidly increase in size and become
yellow.
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In the diphtheritic form, slightly elevated,
white opaque nodules or yellowish patches
develop on the mucous membranes of
mouth, esophagus, tongue, or upper trachea.
Nodules rapidly increase in size and often
coalesce to become a yellow, cheesy,
necrotic, pseudodiphtheritic, or diphtheritic
membrane
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Microscopy
Isolation and Identification of Virus
Serology
Differential Diagnosis
Infectious laryngotracheitis
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Management Procedures
Types of Vaccines
Vaccines of fowlpox and pigeonpox virus
origin are routinely used for vaccination of
chickens and turkeys in areas where the
disease is endemic.
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The flock should be examined about 7—10
days after vaccination for evidence of “takes.”
A “take” consists of swelling of the skin or a
scab at the site where the vaccine was applied
and is evidence of successful vaccination.
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The lack of a take could be the result of
vaccine being applied to an immune bird, use
of a vaccine of inadequate potency (after the
expiration date or subjected to deleterious
influences), or improper application.
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Recent success with in-ovo administration of
FPV vaccines to 18-day-old chicken embryos
has provided encouraging results