This report describes an outbreak of yersiniosis in Egyptian rousette bats (Rousettus aegyptiacus) caused by Yersinia pseudotuberculosis serotype 4b. Twelve of 61 bats died between November and December 2008 or in May 2009. The bats often displayed multiple yellow white nodules in the spleen and liver. Microscopically, these consisted of focal necrosis accompanied by inflammatory cell infiltration and colonies of gram-negative bacilli. The bacterial colonies were identified immunohistochemically as T. pseudotuberculosis 04 and T. pseudotuberculosis serotype 4b was identified by bacteriological examination. Polymerase chain reaction demonstrated that the isolate harboured the virulence genes virF,inv and ypmA. YPMa is as a superantigenic toxin that is associated with acute systemic infection in man and may contribute to the virulence of Y. pseudotuberculosis in bats. (C) 2012 Elsevier Ltd. All rights reserved.