Fowl pox virus (FPV) is a slow spreading viral disease of various avian species that causes skin lesions (dry pox) seen around the comb, wattle, ear lobes and eyes. The diptheritic (wet pox) lesions are associated with the oral cavity and the upper respiratory tract, especially the larynx and trachea.
The latter form is the more serious and the source of current industry problems. The course of the disease in individual birds is from 10 days to two weeks and ''on a flock basis'' generally lasts 6 to 10 weeks.
There are many types of fowl pox viruses and they tend to be specific to particular species of birds. All age groups are at risk and distribution of this disease is worldwide. The incidence of disease is variable depending on climate, management, hygiene, biosecurity and use of a regular vaccination programme.
In the past 15 years, outbreaks of wet pox have caused severe mortality losses in both vaccinated and non-vaccinated flocks. Field isolates from severe wet pox cases have been studied and some have been found to contain intact reticuloendotheliosis (REV) provirus or long terminal repeats (LTRs) of REV. Most of these field strains show a greater pathogenicity and induce an antibody response to both REV and FPV. REV is associated with immunosuppression and, with integrated sequences in the genome of FPV, seems to play an important role in the pathogenesis and prolonged persistence of wet pox.
Wet pox alone can cause high mortality of up to 50-60 percent in unvaccinated chickens. This disease can start out as wet pox and spread to birds in the dry pox form and vice versa. It can be found causing both wet and dry pox at the same time. Infectious laryngotracheitis (ILT) can occur as a dual infection with wet pox.
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Article made possible through the contribution of Hy-Line International.