Histopathological lesions of Actinobacillus pleuropneumoniae serotype 8 in infected pigs

This study aimed to report, for the first time, histopathological lesions caused by an outbreak of acute Actinobacillus pleuropneumoniae serotype 8 infections in two farms in Cyprus. Lung tissue samples were collected from two different affected farms (a total of eight samples) for bacterial culture, multiplex polymerase chain reaction (PCR)-based serotyping and histopathological evaluation. Severe respiratory clinical signs, vomiting, anorexia, sudden deaths, a morbidity rate of around 25.00% and a mortality rate of over 60.00% in the fattening stage were reported. Macroscopic lesions included acute to subacute fibrotic, hemorrhagic and necrotizing pneumonia with occasionally encapsulated nodule-like abscesses and fibrous pleuritis. Histopathological evaluation revealed fibrous exudate between alveolar spaces and connective tissue, areas of necrosis mixed with alveolar macrophages, lymphocytes, plasma cells and necrotic leukocytes surrounding colonies of cocci. The bronchial and bronchiolar epithelia were degenerated and replaced by eosinophilic cell debris mixed with inflammatory cells. Several arteries and capillaries were clotted and/or infiltrated by inflammatory cells. In conclusion, these A. pleuropneumoniae serotype 8 cases were accompanied by acute illness, death and more pronounced bronchitis and bronchiolitis.