[Detection of Actinobacillus equuli ssp. equuli in piglets with purulent polyarthritis and tendovaginitis]

Actinobacillus equuli ssp. equuli is an opportunistic pathogen in horses, mainly known to cause "sleepy foal disease". In comparison to horses, there are only few reports describing diseases in pigs associated with this gram-negative bacterium. This case report describes an outbreak of infection in a combined farrow-to-finish-farm. In September 2018, the following symptoms were noticed in one third of all newborn piglets from gilts and sows: 6-8 hours after birth piglets became weak and developed swollen joints with moderate to severe lameness. The piglets exhibited lethargy, a subset were non-ambulatory. An elevated piglet mortality within the first days within birth was noted. Seven piglets that succumbed to the disease (days 2-3 of life) were submitted for examination, 4 of which underwent pathological examination. The main findings were purulent polyarthritis and tendovaginitis. In addition, purulent inflammation was detected in the brain and kidneys of one animal. In the bacteriological examination A. equuli ssp. equuli was isolated in a total of 18 samples (brain, joints, suppurative structures of limbs), in a subset of cases as pure culture. For identification, cultural and biochemical characteristics were tested and a mass spectrometry analysis (MALDI-TOF MS) was performed. Further laboratory testing included 16 S rRNA-gene sequencing, a PCR in order to examine for special apx toxin genes as well as a PCR differentiating the two subspecies of A. equuli. It was not possible to identify the source of infection and routes of spread within the pig herd. The bacterial isolates were used for the production of an autogenous vaccine.