Effect van vermindering diercontacten op pleuritis bij vleesvarkens = Effect of less animal contacts on pleuritis in growing and finishing pigs

In opdracht van het Productschap Vee en Vlees hebben de Animal Sciences Group van Wageningen UR, de Faculteit Diergeneeskunde, Veterinair Centrum Someren en Intervet onderzocht of het aantal vleesvarkens met pleuritis aan de slachtlijn verminderd kan worden. Reden voor het onderzoek is de toename van het aantal vleesvarkens met pleuritis aan de slachtlijn. Het doel van het onderzoek was nagaan of door strikte toepassing van all in – all out en het niet mengen van dieren (dieren blijven van geboorte tot afleveren als toom bij elkaar) het aantal dieren met pleuritis aan de slachtlijn verminderd kan worde

Neonatal diarrhoea in pigs: alpha- and beta(2)-toxin produced by Clostridium perfringens

Since 2001 the Pig Health Unit of Utrecht University has been consulted by various pig farms regarding neonatal diarrhoea. When preventive measures against E. coli-induced diarrhoea had no or limited results, the diarrhoeic piglets were investigated further. The microbiological and pathological findings were indicative of infection with Clostridium perfringens. Toxin typing by polymerase chain reaction led to the detection of genes encoding a-toxin (cpa) and beta2-toxin (cpb2). Surprisingly, alpha- and beta2-toxin-producing C. perfringens was isolated from all tested herds with piglets with neonatal diarrhoea. From our observations, it is likely that many herds in the Netherlands are infected with beta2-toxin-producing C. perfringens strains. As present vaccines lack beta2-toxoid and thus do not provide piglets with protection against beta2-induced diarrhoea

Dual infections of PRRSV / influenza or PRRSV / Actinobacillus pleuropneumoniae in the respiratory tract

To study the effect of a previous porcine respiratory and reproductive syndrome-infection (PRRS) of the respiratory tract on influenza virus and Actinobacillus pleuropneumoniae (App) infections, 3-week-old specific-pathogen-free (spf) piglets were intranasally infected with PRRS virus. One week later, when the lung alveolar macrophages of PRRSV infected pigs were lowest in number, a second infection was applied by intranasal aerosol of influenza virus H3N2 or by endobronchial instillation of a mildly virulent App. The first experiment consisted of two groups (only influenza infection or dual PRRSV/influenza infection). A second experiment consisted of 4 groups (only influenza infection, only PRRSV infection, dual PRRSV/influenza infection and uninfected controls). At day 2, 4, 14 and 21 after influenza infection, two pigs were killed and sampled for virological and histopathological examination. Influenza H3N2 virus caused only a mild inflammation of the smaller bronchioli. Previous PRRSV infection did not influence clinical signs during influenza infection. Next, we studied in two experiments the effect of dual PRRSV/App infection during the acute stage at two days after App infection. In a third experiment, the influence of PRRSV on more chronic stages of App infection was studied at two weeks after the App infection. At the end of the experiments, the pigs were killed. Lungs were ranked according to size and kind of the lesions. Lesions were cut and measured, samples were taken for virological and histopathological examination. Statistical analysis of the ranked lung-lesions in the first experiment showed a distinct but small effect of previous PRRSV infection on the development of App-lesions. In PRRSV infected pigs, App produced a more severe disease. The second and third experiment however failed to show any influence of the previous PRRSV infection on the App infection. We conclude that previous PRRSV infection of the respiratory tract of spf pigs does not necessarily enhance the severity of secondary infections of the respiratory tract. Author Keywords: Porcine reproductive and respiratory syndrome virus; Swine influenza virus; Actinobacillus pleuropneumoniae; Dual infections; Pig

Convalescent pigs are protected completely against infection with a homologous Actinobacillus pleuropneumoniae strain but incompletely against a heterologous-serotype strain

To study whether Actinobacillus pleuropneumoniae induces a species- specific immunity, we infected pigs in the left lung with serotype 3 or 9 and after 3 weeks we infected their right lungs with serotype 9. Convalescent pigs were protected against homologous strain reinfection, but after heterologous strain reinfection the degree of protection varied. Neutralizing antibodies were not essential for protection

Convalescent pigs are protected completely against infection with a homologous Actinobacillus pleuropneumoniae strain but incompletely against a heterologous-serotype strain

To study whether Actinobacillus pleuropneumoniae induces a species- specific immunity, we infected pigs in the left lung with serotype 3 or 9 and after 3 weeks we infected their right lungs with serotype 9. Convalescent pigs were protected against homologous strain reinfection, but after heterologous strain reinfection the degree of protection varied. Neutralizing antibodies were not essential for protection