Introducing live pigs is the most common way of introducing new diseases into a herd. In most herds a totally closed herd policy is not feasible, since introduction of replacement breeding stock is necessary. However, there are a number of precautions pig producers can take to minimise the risk of introducing disease into their herds. Swine dysentery Swine dysentery is considered one of the most economically devastating diseases. The presence of swine dysentery infection in a herd can be masked by some in-feed antibiotics and growth promotants.
Pigs can carry the causal organism without showing signs of the disease.
The severity of the disease in a herd is determined by the environment and animal susceptibility. Even though a herd may have enzootic pneumonia, replacements should be bought from a herd where the disease is controlled. Sarcoptic mange is the most important parasite affecting pigs. It is present in 97 per cent of all Western Australian herds. Eight out of every 10 Western Australian herds have worms in some pigs.