Invited Review: Pathology and Epidemiology of FP Virus

Fowl Pox (FP) is a contagious slow-spreading viral disease caused by the FP virus, a DNA virus belonging to the genus avipoxvirus, subfamily chordopoxvirinae of the poxviridae family. It affects all ages, sexes, and breeds of chickens and is distributed worldwide with high prevalence in tropical and subtropical countries. FP is transmitted by direct contact with an infected chicken or indirectly by biting arthropods, (mostly mosquitoes) and through infective fomites. In chickens it is characterized by two forms: (1) The cutaneous or dry form that is characterized by wart-like proliferative lesions and scabs on the featherless areas of skin and (2) the diphtheritic or wet form that is characterized by canker lesions found in the upper digestive and respiratory tracts. In the case of the cutaneous form, the mortality rate is usually low and affected chickens are more likely to recover than those with the diphtheritic form. In the diphtheritic form, proliferative lesions involving the nasal passages, larynx, or trachea cause respiratory distress and death from suffocation. The disease can be diagnosed based on history, presence of typical lesions, and by microscopic examination of affected tissues and virus isolation. Like many other viral diseases, there is no specific treatment for FP but due to its slow-spreading characteristic, the disease can be controlled by vaccination. Therefore, vaccination, arthropod control, and good management programs are important prevention and control methods of chicken FP to be undertaken both at the field and farm level.