Pasteurella Hemolytica Pneumonia

Causative agent: Pasteurella hemolyticum
In cattle there are many viruses, bacteria and various stressors associated with pneumonia. Pasteurella hemolytica has been associated with pneumonia in weaned bison calves (27). P. hemolytica has been found in the tonsils and upper respiratory tract of clinically normal bison (28,29,30). In cattle, it is thought that stressors such as shipping, weaning, mixing, overcrowding, starvation, water deprivation, and handling reduces the effectiveness of the lung’s protective mechanisms. This allows viruses and bacteria to invade the lung and cause pneumonia. Pneumonia in bison calves has been associated with similar stresses (27).

Clinical signs:
The clinical signs of pneumonia in bison calves has not been described (27). In cattle, the clinical signs include: increased respiratory rate, cough, nasal discharge, depression, anorexia and weight loss (9). Pneumonia can be a frequent cause of sudden death in cattle (9).

Postmortem findings:
The pathological changes associated with P. hemolytica pneumonia in bison can be described as fibrinopurulent bronchopneumonia, with fibrinous pleuritis and pericarditis (27).

In cattle, the presence of pneumonia can be determined in live animals by clinical signs. Bison tend to mask clinical signs of disease. Typical clinical signs such as anorexia, depression and an increase in respiratory rate may not be easily observed in bison with pneumonia. Anorexic bison calves will often stand along side of their pen mates with their heads in grain or hay feeders and mimic eating.
Postmortem examination and submission of samples to a diagnostic pathology laboratory for bacterial culture and identification of the causative agent may make the diagnosis. Careful consideration should be given to nutritional changes, handling procedures, transportation, weather, and any other stressors that may be identified as possible contributors to the outbreak of pneumonia.

Treatment protocols for bison with pneumonia have not been reported (27). In cattle, many broad-spectrum antibiotics have been used to treat individuals and to mass medicate pens of cattle (9). If possible, long acting, broad-spectrum antibiotic preparations should be selected for use in bison. During an outbreak, careful surveillance of bison calves at risk with little or no intervention is critical to minimizing the mortalities caused by pneumonia. Keen observation by ranchers who are familiar with the behavior of bison calves will be essential for the identification of sick bison calves. Sick calves should be carefully removed from the group, treated and then returned to the group. Mass medication with long acting, broad-spectrum injectable antibiotics or through the feed or water with broad-spectrum oral antibiotics may be considered.


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