Last winter set a record, the record for the most cases of calf coronavirus disease in my veterinary career (16 years if you are counting). Historically coronavirus infection in calves has been characterized by severe
diarrhea and dehydration in calves 7-14 days of age. Coronavirus essentially destroys most of the absorptive
cells in the calf’s intestine so they cannot absorb milk or electrolytes very well. The damage is so severe that
many calves will die within 48 hours of the initial diarrhea, especially if they are cold or are not treated
aggressively with a well-balanced electrolyte. Coronavirus is typically seen more frequently in the winter
because it loves cool, moist environments. Facilities can be harder to disinfect between calves in the winter
and the calves are also temperature stressed, reducing their ability to fight disease.
What made last winter so different was that we saw a secondary, unresponsive pneumonia on many of the
farms that had coronavirus diarrhea issues. This pneumonia occurred within several weeks of the diarrhea and calves did not perform very well and had high death loss. Scientifically we call that the double whammy. For many years, coronavirus has been found in some cases of bovine pneumonia but its significance has been questioned. Does it really cause disease or is it just present? We have been doing more deep nasopharyngeal swabs in the last few years to determine what viruses and bacteria are present in calves with acute cases of pneumonia. We have found very high levels of coronavirus in some of these samples. The researchers tell us that coronavirus will damage the cells that line the airways, making it easier for other viruses and bacteria to cause damage. I definitely believe it is a player in the pneumonia issues on some farms.
Unfortunately, there is no commercial vaccine labeled to prevent coronavirus pneumonia. The first step is to control as many factors as possible to prevent the other causes of pneumonia, diarrhea, and calf stress.
Sanitation is key, especially around group water tanks and shared nipples.
If you have any concerns about the pneumonia incidence on your farm, what viruses, bacteria, and other
factors are involved, and how to control them, please give us a call.