title: The comparative pathogenicity of four serovars of Actinobacillus (Haemophilus) pleuropneumoniae.
abstract: The pathogenicity of 2 isolates of each of serovars 7, 3, 1 and 2 of Actinobacillus pleuropneumoniae was tested by intranasal inoculation into 60, 6-week-old large white pigs. Four dose rates varying from 0.27 to 560 x 10(6) organisms per pig with 10-fold serial dilutions were used. Surviving pigs were necropsied 7 days after inoculation. The proportion of pigs dying and developing gross lesions following infection was significantly greater for pigs given serotype 1 than for each of the other 3 serotypes, which did not differ significantly from each other. Twelve of 16 pigs given either of the 2 isolates of serovar 1 died after acute illness and 1 of 44 pigs given either of the 2 isolates each of serovars 7, 3 and 2 died. Pigs given serovar 1 showed high temperatures, severe respiratory distress, frothy haemorrhagic nasal discharge and weight loss. Lung lesions were produced in all 16 pigs given serovar 1, in 7 of 14 pigs given serovar 7, 7 of 14 pigs receiving serovar 3 and in 5 of 16 pigs given serovar 2. The lethal infections were characterised by a severe acute fibrinohaemorrhagic necrotising pleuropneumonia, whereas non-lethal cases had lung lesions ranging from necrotising purulent pleuropneumonia to abscessation. Significant differences between isolates in proportions of tissues culture positive for A. pleuropneumoniae for serovars 7 and 2, but not for serovars 3 and 1 suggested that isolates may vary in virulence within serovars, but more detailed studies are needed to clarify this point.
authors.affiliation: Department of Primary Industries, Animal Research Institute, Yeerongpilly, Queensland.
authors.forename: R J
authors.initials: RJ
authors.lastname: Rogers
authors.forename: L E
authors.initials: LE
authors.lastname: Eaves
authors.forename: P J
authors.initials: PJ
authors.lastname: Blackall
authors.forename: K F
authors.initials: KF
authors.lastname: Truman
mesh_terms: D000188:Actinobacillus / Q000145:classification / Q000472:pathogenicity*; D000189:Actinobacillus Infections / Q000382:microbiology / Q000662:veterinary; D000818:Animals; D005260:Female; D006190:Haemophilus / Q000145:classification / Q000472:pathogenicity*; D006192:Haemophilus Infections / Q000382:microbiology / Q000662:veterinary; D008168:Lung / Q000473:pathology; D008297:Male; D009175:Mycoplasma Infections / Q000662:veterinary*; D011002:Pleuropneumonia, Contagious / Q000382:microbiology*; D012703:Serotyping; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D014774:Virulence