Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2015
Publication Date: N/A
Technical Abstract: Background. Mycoplasma bovis is a cause of respiratory disease in cattle and the bacterium most frequently isolated from bovine respiratory disease complex. It has recently emerged as a major health problem in bison, causing pharyngitis, pneumonia, arthritis, dystocia and abortion. In cattle, M. bovis is typically identified as one of several infectious agents acting in concert to cause disease but in bison it appears to be a primary pathogen. MLST analysis revealed that genotypes associated with disease in bison differ from those causing disease in cattle. Whether bison-associated genotypes can act as primary disease agents in cattle is unknown. Methods and Results. Healthy cattle (n=6) and bison (n=7), seronegative for anti-M. bovis IgG, were infected intranasally with an atomized suspension containing a mixture of 4 genetically distinct M. bovis bison isolates. Animals were monitored daily for clinical signs of disease and necropsied 4-6 wks post-infection. Blood and nasal swabs were collected from all animals on day 0 (prior to exposure), day 11 and at necropsy (day 28 or later). Tissue samples (lung, lymph node, liver and spleen) were also collected at necropsy. Blood was tested for serum anti-M. bovis IgG. Nasal swabs and tissues were cultured for Mycoplasma-like colonies, which were further evaluated using an M. bovis-specific PCR. Based on group daily averages, core temperature was elevated in bison for roughly 2 wks after exposure. No other clinical signs were noted in bison or cattle. Unexpectedly, M. bovis was cultured from the nasal cavity of 4 cattle and 6 bison on day 0. Except for 1 bison, the nasal cavity of all animals was culture-positive on at least one of the two remaining days sampled, with most positive on both days. M. bovis was cultured from the lungs of 1 of the cattle and 5 bison and from the tracheobronchial lymph node of 2 cattle and 2 bison; M. bovis was not detected in the liver or spleen of any animal from either group. Abscesses or other pathology typical of recent M. bovis infection were found in lungs of 6 bison while the lungs of infected cattle appeared normal. All animals were seropositive on day 11 post-exposure and antibody levels in all increased significantly by the time of necropsy (p = 0.002). These data suggest that M. bovis genotypes acting as primary respiratory pathogens in bison are unlikely to invade or cause disease in the lungs of cattle when other pathogens are absent.