Chickens victim of a new strain of virus

A virus common to poultry is outfoxing a long-used vaccine, apparently through natural genetic. A new form of fowl pox now threatens poultry production and requires a new vaccine strategy. Live vaccines have been used for more than 50 years to protect commercial poultry against fowl pox - a slow-spreading infection in birds for which there is no treatment. A new viral strain, carrying genes from an unrelated avian virus, has arisen to cause disease in previously vaccinated chickens in several American states. Deoki N. Tripathy, a professor of veterinary pathobiology in the University of Illinois​ College of Veterinary Medicine, summarised the situation in a presentation during the 50th Western Poultry Disease Conference in March at the University of California at Davis: "In most of these occurrences, the diphtheritic form of the disease, which attacks the eyes, throats and trachea, results in high mortality… Reduced egg production with significant economic losses in affected layer flocks also has been observed."​ A molecular analysis of the new form of the virus in the United States and in Australia shows the integration of a retrovirus, avian reticuloendotheliosis virus (REV), into its genome. While fowl pox virus vaccines carry a portion of REV, the new strains contain intact REV. Since fowl pox is among the largest of viruses - more than 200 genes encoding for essential and non-essential proteins - it is not surprising to find "spontaneous, natural genetic engineering"​ occurring between distinct viruses attacking the same birds, he said. In large poultry operations, birds face multiple pathogens. Fowl pox occurs as a dry pox, resulting in wart-like nodules on the skin that turn to scabs, and/or a usually fatal wet pox affecting the oral cavity and upper respiratory system. Most birds recover from dry pox within three to five weeks but not without losses in egg production or growth. The scabs from dry pox that fall from infected birds can contain millions of virus particles and survive for months in the poultry environment. Infection can spread into injured or lacerated skin, and by birds inhaling dust containing the particles. Mosquitoes also can transmit the disease. Tripathy and his colleagues are researching a new generation of poultry vaccines. Source: University Of Illinois At Urbana-Champaign​