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Shipping Fever deaths in yarded yearlings

Unusual presentation: 30 dead in a mob of 800 and another sick.

Time and location: July 2018, top of NT.

Case definition:  Mixed sex brahman weaners and yearlings in good body condition that develop a high temperature, dyspnoea, panting and nasal discharge. Eyelids swollen, eyes okay. Associated with yarding in very dusty conditions.

Gross post mortem findings: One very sick heifer with a temperature of 41oC was euthanased. The main autopsy findings were swelling and inflammation of the retropharyngeal lymph nodes, inflammation of the nasal and pharyngeal membranes, froth in the trachea, and consolidation and oedma of the lower lung lobes. A field diagnosis of Pasteurella multocida pneumonia was made. Fixed and fresh samples including swabs of the lung and eye lesions were sent to the lab, along with an EDTA blood and smear. A treatment regime was started.

Laboratory findings:  Histopathology and bacteriology confirmed a fibrinous pneumonia with growth of Pasteurella multocida (with no evidence of viral involvement). Pink eye was confirmed by eyelid inflammation and abundant small gram negative bacillus in the suppuration (consistent with Moraxella bovis) . Disease exclusion tests were run for Mycoplasma mycoides ss mycoides (contagious bovine pleuropneumonia) and Mycoplasma bovis.

Animal / management / environment risk factors: Pasteurella multocida live in the upper respiratory tract of normal cattle and are kept in check by the body’s defences.  The bacteria can invade lung tissue when animals are stressed, and are easily spread by nasal discharges from infected cattle in crowded or confined conditions. The dusty conditions and high stocking rate will have contributed to the rampant growth of this bacteria and subsequent deaths.

Recommendations to the producer: Treat affected cattle with Vitamin A,D&E injection  AND Anti-inflammatory (flunixin or tolfenamic acid)  AND a course of antibiotics (oxytet or trimethoprim/sulfadoxine).

To prevent further cases: reduce the stocking density to less than 1 beast per 10 square metres; suppress DUST with sprinklers; and give Vitamin A,D&E injection + Dectomax injection. The Mannheimia haemolytica (Bovilis) vaccine is not indicated in this case.