[Pleuropneumonia in swine due to Haemophilus pleuropneumonia s. parahaemolyticus. II. Studies on the epidemiology and the relation to chronic pleuritis (pleural scars) in baconers (author's transl)]

Abstract

Within a Danish practice area a serological examination was made of 268 breeding animals in 25 conventional sow herds with a view to screening for herd infection with haemophilus pleuropneumoniae. Average size of the herds was 76 year-sows including pregnant gilts (8--200). In 23 herds produced weaners were fed for slaughtering. The frequency of chronic pleuritis in slaughtered baconers in these herds was related to the frequency of seropositive sows in the herds. Three SPF-herds were included in the investigation, a SPF baconer herd reinfected with H. pleuropneumoniae, a SPF baconer herd reinfected with Mycoplasma suipneumoniae and a SPF breeding herd infected with Haemophilus parasuis. Complement fixation antibodies against Haemophilus pleuropneumoniae were found in breeding animals in 22 out of the 25 conventional sow herds. The average incidence of seropositive breeding animals in infected herds was 62% (7%--100%), highest in the largest herds. Likewise the highest serotitres were found in the largest herds, as an expression of strong infection pressure in large herds. The highest titre values were found in boars and young sows. The frequency of seronegative sows was the highest among the oldest sows. The registered frequency of chronic pleuritis among baconers from the examined herds was found increasing along with higher frequency of seropositive sows in the herds. On the basis of these observations and on the basis of a comparison of chronic pleuritis frequency among baconers in six herds (two with high frequency of seropositive breeding animals, one with moderate frequency of seropositive breeding animals, and 3 SPF-herds, one of which had been reinfected with Haemophilus pleuropneumoniae, one reinfected with Mycoplasma suipneumoniae and one that had experienced an acute outbreak of Glässer's Syndrome) it is concluded that haemophilus pleuropneumoniae is the absolutely most important cause of chronic pleuritis in baconers. A pronounced seasonal variation was found in the monthly pleuritis frequency among baconers in herds strongly infected with Haemophilus pleuropneumoniae, the minumum frequency being in January-February, and the maximum frequency in July-October. It is supposed that the observed variation in frequency of chronic pleuritis is caused by changes in the environmental climate. High frequency of chronic pleuritis is caused by changes in the environmental climate. High frequency is found in the summer in slaughtered baconers, which have been clinically affected by pleuropneumonia as piglets and weaners under inferior climatic conditions during the colder season of the year.