"Harvest illness usually rears its ugly head when farms can’t dedicate an employee to calves full-time. It’s also challenging for farms that do their own harvesting. Harvest illness isn't caused by a strain of bug that shows up at a certain time of the year, but is due to the producer needing to direct their attention elsewhere on the farm."
This is a quote from an interesting column that you can access HERE. The author, Rebecca LaBerge, offers several practical steps to minimize this unique kind of illness.
When I was responsible for calves on a 1,200 cow dairy I also found myself "paddling upstream" trying to keep calves healthy for about a month - but in contrast, for me it was in the spring - I called it "Spring Work Blues." It was the same issue of too much work at a peak time and too few folks to maintain high quality care especially for newborn calves.