Outbreak of acute highly lethal phlegmon in the pharynx, associated with a new Pasteurella multocida MLST type ST63, in a limousine herd

Abstract

We report an outbreak of pharyngeal inflammation in an extensive limousine herd, in central Spain, associated with a novel genotype (ST63) of Pasteurella multocida capsular serogroup B (capB). The outbreak affected cattle of all ages, reaching a herd-level death rate of 17.6% and case fatality rate of 93.3%. Affected animals showed throat inflammation, respiratory distress and finally death, without characteristics of depression or haemorrhagic septicaemia in an acute course. Postmortem examination only revealed inflammation, including oedema in the pharynx and surrounding tissues. None of the necropsied animals was septicaemic and none showed multisystem petechial haemorrhages, pneumonia or enteritis characteristics of haemorrhagic septicaemia. P. multocida was isolated, serotyped and characterised as capB and, with the multihost P. multocida multilocus sequence typing database, isolates were assigned to the new sequence type ST63. Results of this study suggest that capB P. multocida type ST63 should be considered in the differential diagnoses of acute throat inflammation in cattle.