Short communication: Isolation frequency of bacteria causing lymphadenitis and abscesses in small ruminants in central Spain

Infectious lymphadenitis in small ruminants caused by Corynebacterium pseudotuberculosis and Staphylococcus aureus subsp. anaerobius are widely distributed throughout the world, and result in significant economic losses. Trueperella pyogenes has also been associated with lymphadenitis in sheep and goats. In order to determinate the isolation frequency of the different agents associated with lymphadenitis and abscesses, 171 pus samples (135 from sheep and 36 from goats) from 46 flocks were investigated. Isolated bacteria were identified by MALDI-TOF method. S. aureus subsp. anaerobius was the most frequently detected agent. It was identified in 76 animals (59 sheep and 17 goats) from 24 of the surveyed flocks. Of these infected animal, 25 (32,9%) were over one year old, confirming that abscess disease may occur in a significant percentage of adult animals. C. pseudotuberculosis was identified in 45 of the sampled animals (36 sheep and 9 goats) from 24 flocks. Only 5 of animals suffering caseous lymphadenitis were under one year old. T. pyogenes was isolated from 17 animals (13 sheep and 4 goats) in 11 flocks. Seven of these samples were taken from subcutaneous abscesses located in not lymph nodes regions. A notable finding of this work is the isolation of Actinomyces hyovaginalis from 5 of the samples analyzed all of them taken from subcutaneous abscesses located in superficial lymph nodes regions. Thus, T. pyogenes and A. hyovaginalis should be included in the differential diagnosis of lymphadenitis in small ruminants. In 19 of the 46 surveyed flocks at least two of the four agents were detected, which underlines the need to analyze samples from several animals to reach an accurate diagnosis in flocks affected by lymphadenitis.