by Kelly Daynard and Isabel Dopta

Mycoplasma. It’s a disease that is affecting feedlot operators nation-wide. In recent years, it’s been diagnosed more and more often but is it actually becoming more common or are veterinarians and researchers just becoming better at recognizing it?

 The answer to that question differs on whom you ask.

In Canada, Mycoplasma bovis can cause several different diseases – feedlot pneumonia and arthritis are two that can cause severe losses. Morbidity, according to a report by Dr. Rosenbusch of Iowa State University, can vary from 10 to over 80% with overall mortality reaching as high as 10% (including culling).

Clinical signs associated with respiratory infections include nasal discharge, depression, decreased appetite and fever resulting in a chronic, progressive, non-responsive pneumonia. Signs associated with joint infections include stiffness, lameness, swollen joints, weight loss and difficulty when rising.

Last year, Dr. Ken Bateman received $25,000 from the Ontario Cattlemen’s Association’s Research Committee to conduct a one-year project to investigate the role of mycoplasma in Ontario feedlots. Veterinarians and producers from across the province are forwarding carcasses to Bateman’s team at the University of Guelph for testing to determine what feedlot calves are dying of. 

Because mycoplasma isn’t a virus or a bacteria but more like a combination of the two, vaccine development has proved difficult at best. Decades of research in Europe has proved unsuccessful in finding a vaccine for mycoplasma and Dr. Rosenbusch’s work suggests that vaccines may do more harm than good. So, says both Bateman and veterinarian Peter Kotzeff of the Chesley Veterinary Clinic, efficacious vaccines are highly unlikely to be available to producers in the foreseeable future. Instead, they suggest that producers need to re-examine their management practices to see if there are other ways of reducing incidence and impact of mycoplasma in their herds.

Antibiotic treatment – both metaphylactic (just before becoming clinically ill, usually immediately after purchase) and individual therapy at illness – for mycoplasma, has also met with little success.

Bateman knows that the cost of conducting a post mortem is often a deterring factor for cattle producers – another reason he feels his study is so important. He said producers are upset enough over the fact that they’ve just lost an animal worth $800 or more that they often don’t want to spend up to $200 to have tests done. “They often simply cross their fingers and hope another doesn’t die,” he explained. It’s for this reason that Bateman’s planning on testing approximately 100 carcasses from across the province to determine what is killing cattle in Ontario feedlots. 

At the half way point in his project, tests have revealed 16 cases of mycoplasma pneumonia – three quarters of which also had arthritis. These numbers don’t surprise the University of Guelph researcher. 

“Mycoplasma pneumonia and arthritis has been documented since the 1970’s,” Bateman said in a recent interview, “however I believe we’re just getting better at recognizing it. In work that I was involved in back in the early 90’s, we were able to culture Mycoplasma species from the lungs of both healthy and diseased feedlot calves. We have assumed that it was of little significance most of the time.” 

Bateman noted that one of the biggest problems comes from the difficulties of diagnosing the disease while the animals are still alive. “Lungs are such an inaccessible place that it makes it difficult to get a sample from a live animal,” he explained adding that another problem often comes due to the length of time between when the animal begins looking ill and when it either dies or is euthanized. Most calves, he said, are given metaphylactic antibiotics at processing. After a week or ten days, they may be showing symptoms of lameness or other conditions but if they don’t show clear symptoms, but are unwell, they are often treated for respiratory problems – a reasonable assumption. Another 10 days may pass before the symptoms appear again. Then, noted the university researcher, they may be treated with yet another type of antibiotic and the problems continue.

Is mycoplasma contagious and can it be passed through cattle in a herd? “I suspect that the contagious point is often the auction barn or the truck,” Bateman said. “Once they’re out in a spacious feedlot, the odds of transmitting the disease from one respiratory tract to another are actually quite small so I suspect it’s a point source epidemic. All are exposed to weaning, auction barns and trucks at the same time.” He added, “Livestock trucks are the beef industry’s equivalent of a school bus in terms of an inoculation chamber.” There are a lot of potential illnesses that can be spread during transportation.

Dr. Kotzeff deals primarily with beef feedlots in his practice. He has seen a definite increase in the number of mycoplasma cases and now estimates that between 60 and 80% of his post mortem findings involve mycoplasma. As well, virtually all herd wrecks involve mycoplasma.

Feedlot operators John Gillespie of Waterloo County and Harold Klages of Grey County say that having mycoplasma in a herd is a heart breaking experience for feeders. Because of the length of the illness and the obvious suffering of the animals, “You almost need to treat the owner rather than the cattle in many cases,” said Gillespie. “It is just devastating.” Last year Gillespie saw his rate of mycoplasma in his herd go from 0 to 10% in one season. 

Klages has also had the problem in his herd and said that while “avoiding it is the best treatment, there is no recipe for keeping it out of your herds.” 

Fortunately, Klages has experienced an 80% to 90% cure rate in those animals affected by mycoplasma arthritis by isolating the animals and feeding them away from competition by the other animals. He also beds them down well but says that the effort it takes to nurse the animals back to health is significant and requires a huge time commitment.

While he knows many veterinarians in the province may not agree with his theory, Bateman has also wondered if aggressive antibiotic programs given stocker calves upon arrival, to help prevent shipping fever pneumonia, may, in fact, be giving a competitive edge to mycoplasma in the respiratory tract.

“What’s been emerging in the last few years is an increased use of antibiotics especially for metaphylaxis. I too have recommended the practice. Little else has changed significantly in feedlot management so I have to wonder could the use of metaphylaxis be the cause, somehow, of the problem. Antibiotics at arrival help to prevent shipping fever but may, also, be creating favourable conditions for mycoplasma to take hold.” 

It’s a controversial theory at best and one not expounded by some veterinarians who encourage their producers to treat their cattle with long-acting antibiotics upon arrival. Gillespie said that while producers don’t like using mass treatments of antibiotics, many will do anything to keep their herd healthy. “We consider beef to be a natural product. We don’t like to give them antibiotics every day.”

Kotzeff said that antibiotics, administered upon arrival, clearly help control cases of shipping fever pneumonia but he agrees with Bateman that they do nothing for mycoplasma. 

“Does antibiotic use produce cases of mycoplasma through preferential selection? Possibly,” Kotzeff commented, “but antibiotic use definitely cannot control or prevent mycoplasma problems.” He added that much more research needs to be done before we can be certain of the causes of the disease.

Bateman added, “I don’t think we’re going to defeat Mycoplasma bovis by antibiotic use. Bathing them in drugs won’t solve the problem.” 

Both Bateman and Kotzeff are intrigued by work from the University of Saskatchewan that suggests that there’s a link between BVD and mycoplasma given the number of cases of both that are being seen in post mortem findings. Because something can be done about BVD, this may be where to start.

What has also caused Bateman some concern is that in the first 50 autopsies there have been 16 cases of BVD. Thirteen of the 16 cases were so-called persistently infection with BVD. This occurs because the calf became infected as a fetus during the first third of gestation. As such, these calves do not recognize the virus as foreign and are “destined to die” usually after movement to the feedlot and before reaching slaughter weight. Nothing can be done to prevent that. Significantly then, about 25% of the deaths could not have been prevented by either prevaccination before sale or by anything the feedlot operator does post-arrival. The only hope of preventing persistent infection with BVD lies with proper vaccination of heifers before breeding and the cowherd annually.

“What we do know is that mycoplasma does not respond to mass medication techniques. Instead we need to find different management practices to control the problem.” Kotzeff noted.

In speaking with his clients, the Chesley vet encourages them “to go back to square one – re-evaluate how they purchase and handle their cattle.” By buying animals that have been vaccinated against BVD and by reducing stress on cattle, he’s convinced that the incidence of both BVD and mycoplasma will be reduced. He also encourages cow-calf producers to vaccinate their cows against BVD to help prevent problems further down the chain. Bateman and Kotzeff are both adamant that proper vaccination of the cowherd is just as important as prevaccination of the calves before sale.

Gillespie gets frustrated when cow/calf producers tell him that the reason they don’t vaccinate their cows and calves against BVD is because “they’re not paid to do so.”
Bob Dobson of Renfrew County implemented a strict vaccination protocol for his entire cow herd ten years ago and says for him “the equation is simple. More vaccinations used reduces the antibiotic use that is required later.” This year, he noted that producers in Eastern Ontario participated in their first sale where all calves had to be completely vaccinated. Producers participating in the sale did see a small premium on their calves but even more important, said Dobson, was the message that was sent to the rest of the industry. Said Dobson, “We’re going to see a time when feedlot buyers look unfavorably on animals that haven’t been vaccinated.

For those cow/calf farmers that don’t vaccinate their calves, Gillespie has a solution. He’d like to show them photos of their sick calves, two weeks after they leave their herds of origin. “They wouldn’t believe these are the same calves – they’ve got their heads down, have high fevers, and are on the verge of death.” Gillespie’s now buying yearlings and hasn’t had any more problems. He noted, “I’m scared to buy calves ever again.”