Pneumonia Epizootics in Norwegian Muskoxen Caused by Mycoplasma Ovipneumoniae

The Norwegian muskox population consists of approximately 300 individuals living on the mountain plateau of Dovre in southern Norway. They originate from 21 muskox calves that were introduced from Greenland between 1947 and 1953. The population is not actively controlled and normally the two main causes of mortality are animals that are killed when the stray from the area and from railroad accidents. During late summer 2006 and 2012, severe outbreaks of pneumonia with die-offs of 25-30% occurred. During the 2012 outbreak, efforts were made to gather high quality microbiological lung samples from sick animals culled in the field. These samples were examined both by bacteriology and modern molecular-biological methods, including high throughput sequencing (pyrosequencing). The study also included retrospective immunohistochemical examination of lung materials from the 2006 epidemic and sera from muskoxen killed in the period 2004-2013, as well as Mycoplasma examinations from sheep flocks that were present in the muskox area during the summer of 2012. This study identified M. ovipneumoniae as the plausible primary cause of the muskox pneumonia epidemics both in 2006 and 2012 and domestic sheep as the likely source of infection introduction.