Testing of remedial measures in fattening pig herds affected with subclinical infections of Actinobacillus pleuropneumoniae serotype 2.

The present investigation comprised 5 specialized herds of slaughter pigs, each with a production of 1,500 to 4,000 fatteners per year. High prevalence of pleuritis was demonstrated in all herds at slaughter. Serological investigations by means of ELISA were carried out to determine antibody titres to Actinobacillus pleuropneumoniae (A. pl.) serotype 2 during the fattening period and at slaughter. The investigations showed that this agent was a predominant cause of the subclinical pleuritis although A. pl. was difficult to isolate. An environment study was performed in all herds and major environmental deficiencies were corrected during the course of the investigation. Similarly, all herds changed to a strict routine of batch rearing. In 4 herds out of 5, the animals were vaccinated on arrival to the growing-finishing units and again generally 3-4 weeks later with an inactivated vaccine against A. pl. serotype 2. The prevalence of pleuritis decreased with 25-75% during the three-year observation period. Also the prevalence of pneumonia decreased at the same time. Conversely, daily weight gain and feed conversion improved. The prevalence of pleuritis and pneumonia registered at slaughter was lower in three-breed crosses (including Hampshire, Landrace and Yorkshire) than in the two-breed crosses with Landrace and Yorkshire.