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Avian Pox Virus | 367

(A)

(B)

Figure 13.4 Cutaneous pox lesions in an experimentally infected
chicken involving head area.

Figure 13.6 (A) Diphtheritic fowlpox with a tracheal plug (Courtesy
of Dr G. Sarma, Vice President of Research and Development,
Hygieia Biological Laboratories, Woodland, CA). (B) Diphtheritic
fowlpox; microscopic lesion in the trachea characterized by marked
proliferation of the tracheal epithelium.

those with the diphtheritic form involving oral mucosa and the
respiratory tract. In pullets coming into lay and in older birds, the
disease often runs a slow course accompanied by unthriftiness and
reduced egg production. The course of the mild cutaneous form
of disease is about 3–4 weeks, but if complications are present,
the duration may be considerably longer. With virulent strains of
FWPV, both primary and secondary cutaneous lesions may per-
Figure 13.5 Cutaneous pox lesions in a naturally infected wild sist for more than 4 weeks (Tripathy et al., 1975). In turkeys, the
turkey involving head area retardation of growth development of market birds is of greater
financial importance than mortality. Blindness due to cutaneous
eye lesions and starvation cause most of the losses (Fig. 13.5).
flock if a virulent virus is present and no preventative measures If pox occurs in breeding birds, decreased egg production and
have been taken. Two forms of the disease recognized are: cuta- impaired fertility may result. Severe outbreaks of fowlpox often
neous and/or diphtheritic. Often both forms of the diseases may last 6, 7, or even 8 weeks. Flock mortality in chickens and turkeys
be observed in a single bird or in a flock. The cutaneous form of is usually low, but in severe cases it may be high. In pigeons and
the disease is characterized by the appearance of nodular lesions psittacines, morbidity and mortality rates are similar to those in
on the comb, wattle, eyelids, and other non-feathered areas of the chickens.
body (Figs. 13.4 and 13.5). Cutaneous eye lesions may interfere A systemic form of infection with high mortality is usually
with the bird’s ability to find food and water. In the diphthe- seen in canaries. The clinical signs include respiratory distress;
ritic form (wet pox), cankers or diphtheritic yellowish lesions loss of feathers and or/scaly skin on the head, neck, and back;
(Fig. 13.6A and B) occur on the mucous membranes of the weight loss; and high mortality (Donnelly and Crane, 1984). Pox
mouth, oesophagus, or trachea with accompanying coryza-like in canaries can cause mortality as high as 80–100%. For exam-
mild or severe respiratory signs similar to those caused by infec- ple, in a natural outbreak of canarypox virus mortality in excess
tious laryngotracheitis virus (ILTV) infection of the trachea in of 65% occurred in a flock of 450 canaries (Shivaprasad et al.,
chickens. Lesions in the corner of the mouth and on the tongue, 2009). Similarly, significant mortality has been observed in quail
throat, and upper part of the trachea interfere with eating, drink- infected with quailpox virus. Poxvirus infections have been con-
ing, and breathing. Birds affected with less virulent virus strains sidered as a population-limiting factor for endangered Hawaiian
causing few localized skin lesions are more likely to recover than forest birds.