We have all heard of corona virus being one of the main causes of viral scours in our newborn calves.
It and a couple of strains of rotavirus are the two main viruses we see in our scours vaccines. (It also causes a winter dysentery bloody diarrhea in mature cattle, especially housed dairy cattle in the winter.) What you also may not have known is this same virus can be involved in the bovine respiratory disease complex.
The respiratory syndrome is often masked by the other much more prominent viruses such as IBR and BRSV or the main bacterial causes of pneumonia that being Mannheimia Hemolytica, Pasteurella Multocida and finally Histophilus Somnus. Often it may be involved with the respiratory disease complex with these other components, but is generally less serious. There is no respiratory vaccine on the market that has the corona virus antigen in it, but in the future — as the vaccines become broader and broader spectrum — a company may put in the corona virus to bolster the immunity to more respiratory pathogens once again.
Respiratory disease is the No. 1 economic disease in feedlots across Canada so anything we can do to reduce cases is beneficial. Cattle have a lot less lung capacity than other species but the big rumen and digestive process require a lot more oxygen. So technically the lungs have very little reserve in them, and that leads to more issues with respiratory disease.
A few separate outbreaks of corona virus respiratory disease have occurred and you generally see some slight depression, but overall animals will still look bright. There may be increased nasal secretions and feed intake may go down significantly. In fact, it may be this feed decrease is the first thing that is experienced. One still has to treat the sick calves for secondary bacterial infection. It can also occur if there is suppression of the immune system because of vitamin or mineral deficiency, internal parasites or a concurrent disease. You may even have some cattle infected with corona and have the enteric form as well. You would then expect to have diarrhea accompany some of the other clinical signs in a small percentage of infected cattle.
So if a group of cattle seems to be sicker than in the past — in spite of vaccinating for pneumonia — have them checked out, as the corona virus may be the culprit.
Another bacterial cause of pneumonia presents itself a different way and may be an emerging disease in the United States — which means we should keep our eyes open in Canada because of all the trading of cattle and other livestock that goes on.
The bacterium is Bibersteinia trehalosi and is very closely related to M. Hemolytica that is the key bacteria involved in the whole bovine respiratory disease complex. It presents itself as sudden death and in the U.S. has involved Holstein cows primarily and is significant at causing pneumonia and blood infection (septicemia) in sheep. The pneumonia veterinarians see on a post-mortem is really indistinguishable from the M. Hemolytica form and it is indistinguishable on routine lab submissions. So unless the lab does special testing it is hard to identify. It may be another emerging component to the whole respiratory disease complex.
U.S. veterinarians noticed this form of pneumonia was different because it was a quick killer of cows and was fairly unresponsive to antibiotics. Part of the reason was its acute nature — the antibiotic simply doesn’t have enough time to work. Also, we generally are not expecting full-grown cows to develop respiratory disease and so it catches us off guard. In some cases, this organism can be quite resistant to many different antibiotics when we culture it.
Even though now there are several good long-lasting macrolide antibiotics for treating groups of high-risk calves, this should not reduce our vigilance in watching for unusual respiratory disease. If the incidence of treatment or death loss is higher than expected or there have been sudden deaths, then have some of the animals autopsied by your veterinarian. Finding the root cause will definitely help them determine better treatment, biosecurity and preventive measures for your farm.
Cow-calf, feeders and feedlot operators have definitely reduced the incidence of pneumonia deaths in Canada over the last decade through a combination of using vaccines with broader coverage, using metaphylactic antibiotics, better treatment antimicrobials, and anti-inflammatory drugs.
Feed conversion is better with less chronics present. So if your response to vaccines seems poor; pulls are too high; or death rates are unacceptable, get the cattle checked and post-mortem any recently dead ones (especially sudden deaths). One of these emerging pathogens (especially B. trehalosi) could be present and you need to do a culture to find out.
Be aware of new advances in the early detection prevention and treatment of respiratory disease. Different vaccination combinations are always presenting themselves and there is always going to be continued research in this area of cattle medicine.