Vaccination against Mycoplasma hyopneumoniae is an important tool for controlling the economic impact of the disease, says Professor Dominiek Maes, from the Faculty of Veterinary Medicine at Ghent University, Belgium.

Weight losses due to enzootic pneumonia are greater if pigs are infected early in life, says Professor Maes, speaking at a recent symposium in Barcelona.

One-shot vaccination at one week of age has proved beneficial, he says, although double vaccination of pigs in the farrowing or nursery unit is frequently used. Piglets can become infected in the farrowing unit by direct nose-to-nose contact with the sow or by aerosol transmission.

He believes vaccination can improve daily weight gain (2-8%) and feed conversion (2-5%), reduce time to slaughter, improve carcass quality and sometimes reduce mortality.

He recommends that a number of different parameters should be considered before deciding how to use vaccination most effectively as part of an overall disease management programme. First, the severity of the disease and the infection pattern should be assessed by evaluating the clinical signs, serology, and lung pathology at slaughter.

The best results are obtained using a sustained, high level of vaccination within the pig herd, but the maximum benefit is not seen for several months after start of a M hyo vaccination programme. Vaccination should not be used to cover up poor management; since EP is a multi-factorial disease, additional control strategies based on animal management, housing and strategic medication are also needed.

Professor Maes says that M hyo is a primary pathogen, which by itself generally has relatively little impact on production. However, the organism damages the cells of the respiratory tract and lowers the natural defence mechanisms, leaving the animal vulnerable to other pathogens.

Under experimental conditions, the incubation period is 10 to 16 days, he adds, with the first sign usually a dry cough peaking after 4 to 5 weeks and decreasing after 10 weeks. However, under natural conditions the disease course varies greatly.