Should the disease be transmitted to our flocks, not only would there be major health and welfare problems, but research may need to be terminated. The costs in terms of the number of birds which may have to be killed, and the wasted research time and effort, would be major. The disease is caused by a virus of the Paramyxovirus family of viruses. The virus can infect and multiply in up to 155 avian species, as well as a similar number of non-avian species of animals. The chicken is the most important natural host, developing the disease fully with virulent infections, while most other species show few or no signs of infection.
Younger chickens are more susceptible, with sudden deaths a common finding.
In adult birds, signs from depressed birds with ruffled feathers, to respiratory distress with sneezing and diarrhoea are found, as well as soft eggs and reduced production. With certain strains of the virus, nervous signs and twisted necks can be seen. Transmission of the virus is most common through bird to bird contact, commonly via droplets from the respiratory tract or through the faeces. The virus is shed from infected birds in all secretions and excretions. In dry conditions, dust will pick up infected particles and promote the spread.