For the past five years, there have been large outbreaks of infectious laryngotracheitis (ILT) in chickens in Australia. ILT is a highly contagious herpesvirus, and one of a group that includes herpes and chickenpox. The chickens become very ill with red and swollen eyes, along with sneezing, coughing and gasping, while occasionally producing a bloody nasal discharge. Mortality is quite high, and surviving chickens produce fewer eggs, which, of course, is very bad for chicken farmers.
The diseases are usually prevented by a vaccine against ILT. Many vaccines against viruses, including the ILT version, contain live attenuated viruses (LAV), which are viruses that have reduced virulence, though still alive, so that the immune system recognizes it to develop an immune response. Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. Continue reading “Chicken vaccine viruses recombine in wild, anti-vaccine conspiracies abound”