Expansion of the free-range chicken sector has led to the resurgence of some old diseases. That was one topic debated at Chicken 2008, as Richard Allison discovered.
It is obviously more difficult to prevent disease in free-range birds than those raised solely indoors, as they are outside exposed to adverse weather and predators, as well as having access to watercourses and other livestock.
So as the number of free-range table birds increases, it’s no surprise that vets are seeing some older diseases that they shouldn’t be seeing, warned Peter Cargill of Wyatt Poultry Veterinary Services at Chicken 2008, held at Stoneleigh Park in Warwickshire.
“Old diseases which were are now seeing include pasturella, erysipelas, blackhead, Marek’s, avian leukosis and worms.”
Looking at pasturella, this condition can be acute or chronic and in some cases, 100% of the flock can be affected. The good news is that the bacteria responsible for the disease is easily killed by disinfectants, “but the problem is that you get reservoirs of infection in rodents, cats and possibly pigs and sheep.”
He believes the recent increase in cases is due to exposure of birds to other farm species.
Similarly, erysipelas is associated with pasture used for pigs and sheep, and it can lie dormant in soil for some time. The problem with this disease is that this bacteria is much more difficult to kill than the one causing pasturella, being resistant to disinfectants. It can be treated, but success is variable due to re-infection.
Avian leukosis is another disease that has re-emerged. Mr Cargill outlined a case where it occurred in a small flock of niche breed birds with the tell-tale tumours found in most tissues. This case, he warned, highlighted that some niche breeds may not be avian leukosis virus free.
In conclusion, he predicted that the broiler sector will see big changes in disease dynamics with more birds being outside. “We need to avoid multi-species farms and ensure good biosecurity measures are in place.
One problem hampering the treatment of these forgotten diseases is that products once available for their treatment are no longer available, as licences lapsed with new EU rules. One example is blackhead, where there is no longer an effective treatment since the withdrawal of products such as nitroimidazoles.