Pneumonia in cattle is a common yet dreadful condition. In addition to compromising the health of the animal, raging inflammation in the lungs can reduce growth and production, decrease animal welfare and may even cause death.
Clinical signs of pneumonia include fever, widespread front legs (trying to give the chest as much room as possible to expand), difficult and rapid breathing, coughing and snotty noses. Affected animals are often depressed and may go off feed.
A lot of research attention and funding is put toward investigating causes of pneumonia in feedlot calves, and rightly so because it is one of the most important disease issues to face cattle in these settings.
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However, pneumonia can strike cattle of any age or production system.
A new study by researchers at the Ontario Veterinary College examined cases of bacterial pneumonia in adult dairy cows that were submitted for autopsy examination. Between 2007 and 2020, there were 115 cases available for this retrospective study that was published in the Canadian Veterinary Journal.
While there are obvious differences between dairy cow management and cow-calf beef operations, the results of this study have several interesting applications to our beef herds.
First, most cases were submitted in the winter (between November and February). This is consistent with the pattern of disease we expect following inclement weather. Weather is a known predisposing factor for pneumonia in calves, so it makes sense it can similarly affect mature cows. Winter is the time to be extra vigilant for signs of pneumonia in our herds.
Secondly, viral causes of pneumonia were rarely identified in this study, even though we know they are an important predisposing factor for bacterial pneumonia. Respiratory viruses reduce lung defenses and make animals susceptible to developing serious bacterial lung infections. Viruses do this by damaging airways, allowing bacteria to take hold deep in the lungs, causing severe inflammation and compromising the cow’s ability to breath.
However, even though a viral cause is often to blame, it can be challenging to pin down the virus using laboratory testing after the animal has died. That is because by the time a cow dies or is euthanized due to pneumonia, the virus has done its work and may be long gone from the system.
The bacterial species identified as causing disease in the cows of this study were consistent with those we expect in feedlot calves, including Mannheimia haemolytica, Trueperella pyogenes and Pasteurella multocida. Importantly, resistance to antibiotics did not appear to be a main reason why these cows didn’t respond to treatment and ended up dying of pneumonia.
The authors suggest that early detection and treatment of pneumonia cases would likely improve response to treatment.
It remains critical that we use antibiotics carefully, even if resistance among respiratory bacteria does not appear to be causing death of animals in this context. Since antibiotics affect the whole body and the bacteria everywhere in the system, we need to use them carefully and appropriately.
Because of the way the study data was collected, it was difficult to understand the role of predisposing factors. However, veterinarians who saw the cases on farm were able to submit what they thought had possibly brought on the pneumonia in the cows.
Factors included mixing cattle or introducing new cows from another herd (and potentially introducing viruses and bacteria with them), other diseases in the cow such as mastitis or twisted stomachs, being close to or having just calved, poor barn ventilation and bad weather.
While we can’t say for sure what caused each case, there is good reason to consider these as reasonable factors, some of which are under management control.
This OVC study is another great example of Canadian research that helps us better understand the causes and types of diseases affecting our Canadian herds.
