Calves can be a target for middle ear infections due to Mycoplasma bovis, which can cause ear droop, excessive discharge from the eye, facial paralysis, head tilt and purulent material in the external ear canal.

Editor’s note: Second in a Mycoplasma bovis series.

Mycoplasma bovis infections can be deceiving in that it’s easy to recover this ubiquitous organism from cattle, but it may not always be the cause of infection. Outside of mastitis, some of the more common infections from Mycoplasma bovis include otitis, arthritis and respiratory syndromes.

Middle ear infections (otitis media)
In calves and even lightweight stockers, middle ear infections due to Mycoplasma bovis can cause ear droop, excessive discharge from the eye, facial paralysis, head tilt and purulent material in the external ear canal.

Alvin Baumwart, DVM, Highland Veterinary Clinic, Arapaho, Okla., says he has seen a lot of middle ear infections in calves. “This year’s increased price of cattle has many producers seeking more veterinary care for their cattle than they do when prices are low,” he says. “People are spending money and bringing cattle to us, and as a result, we’re seeing things we haven’t seen in the past, such as a lot of ear infections.” If Baumwart doesn’t find ticks in the ears, then he wonders if Pasteurella or Mycoplasma is the culprit.

What Baumwart typically sees in a middle ear infection case is a discharge, which he believes indicates the ear drum is probably broken. “I have a hard time identifyingthe tympanic membrane when it all looks like soup in there.”

Richard Sommers, DVM, Silver Lake Veterinary Clinic, Inc., Silver Lake, Ind., works with a lot of veal and feeder calves and commonly sees middle ear infections. He assumes that if there’s a lot of discharge out of the ear, the tympanic membrane is broken. “And that’s good. The success rate on treatment of calves whose ears are draining is going to be a lot higher.”

Though typically a young calf problem, middle ear infections can affect feedlot cattle right up to slaughter. “We recently had a feedlot that was having significant rejections at slaughter because of head tilt,” adds Bob Glock, DVM, PhD, Arizona Veterinary Diagnostic Laboratory. “That gets expensive. We did a number of head salvages and dissected them, and there was a lot of otitis. We grew Mycoplasma and Pasteurella multocida out of them.”

Glock notes that a decades-old article by Rue Jensen at Colorado State University surveyed some feedlot animals with no clinical history of an otitis problem, but a very high percentage of them had otitis lesions and a few of them still had some remaining Mycoplasma organisms, even though they had no clinical disease. “It may be this otitis is more common than we know clinically, and it probably does persist,” says Glock.

Diagnosing Mycoplasma as a factor in otitis can be difficult. “The Mycoplasma world knows that if you stick a swab into a healthy ruminant, you’re going to come back with Mycoplasma – seven or eight different species,” says Ricardo Rosenbusch, DVM, PhD, Iowa State University. “So what are they doing there, and how did they get there?”

 

Joint fluid aspirate samples from a field case of Mycoplasma bovis arthritis. The fluid is clear to sanguinolent, not purulent.

Photo credit: Ricardo Rosenbusch, DVM, PhD

Etiological diagnosis for a Mycoplasma middle ear infection is a separate matter. “That presents as an abscess,” says Rosenbusch. “The problem we have with the abscess is that to make an immunohistochemistry section out if it, you have to decalcify it, and when you decalcify, you lose the immuno-histochemistry signal. Because of the situation of bone mixed with soft tissue, we have not been able to say that M. bovis is causing the abscess. We rely on isolation or PCR, and that’s as good as it gets. It just shows that Mycoplasma is there.”

Treating middle ear infections
When he encounters middle ear infection cases, Sommers automatically treats them for Pasteurella multocida. “I can’t do anything other than administer antibiotics if they’ve got Mycoplasma. However, if it has concurrent Pasteurella multocida infection, I vaccinate as well for Pasteurella. I give it the P. multocida, Mannheimia hemolytica, Hemophilus somnus vaccine after the fact. That’s the old-style cellular Pasteurella vaccine, and I get quite an immunologic boost out of it. Most calves with ear infections also have pneumonic involvement or soon will have. You can detect audible improvement post-vaccination in 48 to 72 hours if there’s not a whole lot of prior chronic damage there.”

One of his clients automatically gives a repull animal a vaccination with a killed Pasteurella multocida vaccine. “It cuts down our chances of repeat pulls and chronic middle ear infection,” says Sommers. “I think P. multocida may be the most underlying cause of some of the ear infections. Just as soon as that ear starts to droop, we treat them with a dose of penicillin and the killed vaccine, and we get a good response.”

With Mycoplasma middle ear infections, Sommers says it’s important whether or not the ear drum has broken on its own. “If it’s draining, the treatment’s got a chance of being successful, especially if you eliminate secondary infection with P. multocida.”

Tom Noffsinger, DVM, Twin Forks Clinic, Benkelman, Neb., says in most of the middle ear infections he sees, the ear drums are not broken. “Response is slow but positive. If there’s facial nerve paralysis, we still can quiet the ear down with systemic antibiotics and care, and it’s not a big issue.”

Baumwart ear flushes using lincomycin, spectinomycin and DMSO, with a bulb syringe and an otoscope. “We have to make sure we don’t have any dead ticks in the ear, and ticks are a big problem in our area. Often we don’t know which came first – the ear infection or the ticks, so we have to flush them very well.” He estimates he can clear 90 percent of the infections, depending on what stage they are in.

“The real bugaboos are the show cattle,” he adds. “Those ears have to be perfect, and we’ll clear most of them. The feedlot cattle we sometimes don’t clear, and they’ll often have a head tilt and some facial paralysis.”

 

Tom Noffsinger, DVM, says Mycoplasma bovis lesions can be present in animals on arrival to the feedlot and may or may not affect performance, depending on factors like weather and stress.

Rosenbusch adds that he has seen U.S. and Canadian operations heavily use spectinomycin or penicillin and a dose of killed P. multocida vaccine with a good success rate for middle ear infections. One operation he dealt with was raising Holsteins for feeders and had ear infections starting in at 3 and 4 weeks of age. “They can have as many as 80 percent of animals infected. As soon as they see conjunctivitis at 1 week of age, they assume they have Mycoplasma bovis. They go right in with a spectinomycin treatment – a 10-day treatment, injectable and in the feed. They save some – not all – but it’s better than not doing it. And an important addition is to manage those calves all-in, all-out.”

Arthritis in stockers
Cattle with arthritis may exhibit stiffness, lameness, difficulty when rising, swollen joints and tendon sheaths, decreased appetite and weight loss (Step, et al, Bovine Practitioner, June 2001). Arthritis caused by Mycoplasma bovis can be a serious problem, but many veterinarians are unsure whether M. bovis is a primary or secondary cause.

“We don’t know if it came in first or second,” says Baumwart. “It’s the same thing with the lungs. Did a virus set the thing up? Mycoplasma is an opportunist. I tell my clients that arthritis is a lung infection that’s settled in the joints. The pathogen got in the lung somehow and became septicemic, got in the joints, and now we can’t get a high enough blood value of any type of any antibiotic, any antimicrobial, to completely wipe it out.”

Baumwart notes that when he sees polyarthritis as a primary clinical presentation in stockers, he also sees evidence of pulmonary lesions or pneumonia on necropsy. However, “we can see polyarthritis without picking up abnormal respiratory sounds or nasal/ocular discharge. That form of the disease is far-reaching.”

 

Though typically a young calf problem, ear infections can affect feedlot cattle right up to slaughter, says Bob Glock, DVM, PhD.

Last year Baumwart’s clients had excellent quality cattle and excellent quality pasture. “The weather was not bad, either. Our problem did not occur days after processing, but at six weeks. We saw three or four separate operations breaking with the arthritic form of Mycoplasma, and I had not seen that before. These were not chronic cattle, nor had they been treated.”

Baumwart says that these particular clients vaccinated and revaccinated with modified-live viral vaccines in addition to Pasteurella vaccine. “It was only about 10 animals out of 500 to 1,000 head, but it was something we hadn’t seen. It was a clinical observation. With the arthritis, sometimes you’re better off going ahead and euthanizing them because you’re going to see a chronic problem.”

As far as distribution of lameness, Baumwart has seen more shoulder and high rear-end lamenesses. Rosenbusch agrees. “Hardly ever do we get isolations from lower joints. When we deal with experimental animals, we’ll go with a syringe and hit every joint, and we hardly ever get the Mycoplasma out of the digital joints. It’s going to be the intermediate and higher joints – the tarsus, carpus and so on.”

Dan Grooms, DVM, PhD, Michigan State University, notes that invariably it may look like it’s just one joint or one leg involved, but if you really look at all the joints, you find there’s involvement of multiple joints. “It may be that one joint is so sore that it’s predominant. We’ve seen it in all joints.”

Sometimes you get a tenosynovitis with very little arthritis. “The articular surfaces are not affected,” says Rosenbusch. “But the tendon sheaths are very swollen, and because of the swelling, you get an immobilized joint.”

“Classically,” adds Grooms, “the joint involvement is defined as a synovitis and not a typical arthritis.”

“We see arthritis in a number of different ways, but we diagnose it when it’s in multiple joints,” says Baumwart. “Many other things might cause an inflammation of a single joint. We have clients that have to pay the bill. Some of them say don’t investigate, and some of them say do. We’re not fooling ourselves. You can spend a lot of money and wait a long time, and sometimes you get a negative response. Owners don’t like that. They like to have answers. We like to know what we’re sending in, and if we’re going to get good answers.”

Baumwart had an unusual case with a good client. The client had 32 arthritis cases out of about 300 300-350-pound stocker cattle. “They weren’t the best-quality cattle, but he’d always gotten by with them. Thirty-two came down with multiple-joint infections. He tried treating them with tetracyclines for a week and gave up.”

The client then brought the cattle to Baumwart’s clinic and left them for two weeks. “We took two typical cases and confirmed Mycoplasma. The owner’s bill was tremendous. It was very labor-intensive to care for 32 cattle. We sent vaccine home with him for him to vaccinate his whole bunch, and then to revaccinate the 32 cattle. He didn’t have any more repeats, but what surprised me was that two died and the rest walked without problems. That was almost phenomenal to me. Most of those cases you just want to get rid of because it’s going to be high dollar, and they want good results.”

Baumwart says usually the septic joint situation involves long, heavy levels of oxytetracyclines and lincomycin for cattle to get back to normal.

The quality of the cattle, stress and the environment may play a role in the expression of Mycoplasma-induced arthritis. “We see it during stress situations, and we’ve seen it in the craziest times,” notes Baumwart. “We’ve seen it with calves already out on wheat pasture and doing very well, not in a concentrated situation. We’d like to think they were treated calves that didn’t completely clear. With this disease, you can throw everything out and have a hard time finding your way back to how this thing came on.”

Baumwart says stressful weather patterns are probably the biggest predictor of Mycoplasma problems in stocker cattle. “Weather patterns such as rain really affects them,” he says. “We’ve always felt that if there’s good wheat pasture out there, it doesn’t make any difference what you do to them or do for them, they’ll do well. But that came back to bite us. We had excellent wheat pasture and some excellent-quality cattle that came down with septic joints. It had a tremendous impact.”

Mycoplasma bovis and respiratory disease
In some feedlot operations, the respiratory syndrome of a Mycoplasma infection can be more significant than the arthritic form. “The challenge that an order buyer or a feedlot operator has with visually identifying problems with this organism is that adrenaline hides its presence,” Noffsinger points out. “We can have young animals arrive that appear to be happy and healthy, and they can be carrying this organism. My perception in certain locales is that it’s a normal inhabitant in all the cattle. Mycoplasma lesions can be present on arrival, and under certain weather conditions and certain management systems, they may not affect performance. At other times, it’s an absolute disaster.”

Noffsinger adds that there’s obviously more risk for a feedlot in buying long-haul highly-stressed animals, “but the potential for risk still exists in calves coming from a single ranch to the feedyard if they are mismanaged.”

He also believes that hot and humid weather seems to be a risk factor. “We see more problems from June to October. As we ask people to examine calves on arrival and at processing, these stress factors seem to dictate whether calves with lesions have an effect on their herdmates. How the other pathogens and immune system interactions happen dictate whether we see a Mycoplasma or not. I don’t think it’s a primary pathogen, but I think we see it in almost all of the animals.”

Does size matter? As far as Mycoplasma problems go, these veterinarians don’t believe the size of an operation influences disease outbreaks. “The size of the operation has little effect,” says Noffsinger. “It’s the quality of management. It has to do with pen space and bunk space, pen conditions and so on.”

Grooms refers to the 2001 Kansas Stocker Mycoplasma survey (Bovine Veterinarian, January 2005). “In the Kansas survey, they said most of the problems occurred in times when they were getting the most cattle in. Management during those times probably becomes a bigger issue. They couldn’t get cattle processed or they had to commingle more, which adds stress. I agree with Noffsinger that usually where we see the worst problems is where we find the worst operators. It doesn’t mean the best operators are immune because they can get bit, too.”

Treatment in the feedlot
Noffsinger’s treatment regimen for a suspected Mycoplasma respiratory disease involves using florfenicol through day three and then switching to spectinomycin. “That’s the only way we’ve gotten these animals back. With hospital chutes that have scales on them, you can actually see these animals start to perform. We see these cattle settle out into long-term recovery, and our challenge there is to not give up on these animals. If we do the right things, we’ll have the responses the client wants.”

There comes a time, however, when enough is enough. In Noffsinger’s case, if the animal can’t get up on arthritic joints, that’s enough. Treatment of lung infections is very similar. “Our treatment crews identify or try to make a judgment on what percentage of lung capacity they think is left in that animal. As they care for these animals, they monitor them for other factors or other diseases coming in, such as a relapse to P. multocida or M. hemolytica. They treat those, but predominately, those animals are just allowed time to recover.”

As a result of an outbreak, Rosenbusch found that it’s possible to suppress M. hemolytica with a strong metaphylactic approach with tilmicosin. “It does a wonderful job, but the Mycoplasma bovis will cruise right along,” he says. “You can bat the Mycoplasma bovis down if you give a fluoroquinolone at the right time. However, if you give a fluoroquinolone in a single dose at the wrong time, it does nothing because it’s a 24-hour antibiotic.”

Rosenbusch says it’s typical to give a fluoroquinolone on day seven or eight when the animals look the worst and you believe you have a Mycoplasma. “You’ll have a fluoroquinolone effect on the M. hemolytica for 24 hours, but the Mycoplasma is going to come right back on days 9, 10 and 11. Those short-term antibiotics like the fluoroquinolones would have to be given at the critical point, which can vary with each group – in general on day 12 or 14.”

He notes that therapies for Mycoplasma bovis have to be delayed until a large number of animals are infected. “Then you have to have cowboys who can find the affected animals. They’ll be low fever-affected and slightly depressed. They’re not anorexic. They’re just slower coming to the bunk. If you have any kind of shade, they seek it.”

The key to effective treatment is catching them early. “In groups of cattle that we think are at high risk for getting Mycoplasma, we’ve been going in with a mass treatment with chlortetracycline in the feed or with oxytetracycline multiple times,” says Grooms. “It’s a late metaphylaxis, but it has to be a long-term thing. We’ve had success with that. It may be that nothing would have happened because we haven’t done a controlled study, but in farms where we’ve had previous Mycoplasma problems, we’ve been able to slow problems down. This is two to four weeks into the feeding period when we typically see Mycoplasma.” Grooms adds that these are typically non-Mycoplasma-vaccinated cattle.

Glock’s concern is that multiple treatments may stress the cattle more, but Noffsinger says that doesn’t seem to be a problem. “If we’ve got a pen of calves we’re suspicious of, our treatment crew is dedicated to try to find these animals that are harboring Mycoplasma, along with M. hemolytica, for instance, on day one of treatment,” Noffsinger explains. “We would never expect that animal to respond to a single one- or two-day therapy. That’s a little bit of a change within the industry. We’ve had to dedicate some recovery pens and hospital pens to that. With some management systems, that works. With others, you cannot achieve that.”

Sommers vaccinates all of his feedlot cattle with two doses of Mycoplasma bovis vaccine. “In the past, when we’ve had some arthritis problems, we’ve come back with the newer vaccine. We vaccinate them three times and put them on chlortetracycline, and in most cases they are walking better six weeks later.”

Baumwart is still in the evaluation stage of using Mycoplasma bovis vaccine. “Routinely, our cattle come in and we try to evaluate by metaphylaxis choice,” he says. “We try not to leave too many choices on vaccines. We believe in revaccination, and we believe in using modified-live viruses in the sick pen. I think that’s one of the cheaper things we can do. We just keep challenging that animal, maybe in a different way, and try to stimulate some immunity. Sooner or later, those antibiotics are going to wear off.”

Rosenbusch suggests that in stockers, where M. hemolytica can be a severe problem, tilmicosin plus vaccination for M. hemolytica can be a good combination to significantly reduce Mycoplasma problems. “First attack the Gram-negatives, which are going to be rapid attack organisms. Then reserve a more direct attack at the Mycoplasma a week or 10 days later, when the problem is, hopefully, reduced in size.”

“We all know the importance of diagnosis of bovine respiratory disease in the early stage and treating with the right drug for the right amount of time,” Baumwart continues. “We have producers out there who are trying to do that themselves. They try to cut some corners sometimes, but we can’t predict that the penny-pinchers are the ones who will have problems. It’s an unpredictable disease.”

This information is from a Bovine Veterinarian Mycoplasma bovis roundtable sponsored by Boehringer Ingelheim and moderated by Bob Glock, DVM, PhD.

Can mycoplasma infections be treated successfully?

In a study presented at the 2004 American Association of Bovine Practitioners meeting, Ricardo Rosenbusch et al found that florfenicol, enrofloxacin and spectinomycin were active in vitro against all of 223 Mycoplasma bovis isolates recently recovered from 26 states and from various disease forms.

Oxytetracycline and, to a lesser extent, chlortetracycline were active in vitro against half or most of the isolates, depending on interpretive criteria used. Very few isolates were inhibited by tilmicosin, and none by erythromycin, ampicillin or ceftiofur. No regional differences were detected in susceptibility profiles. Likewise, no differences in profile were detected among mastitis isolates versus pneumonia, arthritis or middle ear cases.

“While there are no validated breakpoint values for Mycoplasma bovis, the data suggests that treatment may be successful with certain antimicrobials under optimal treatment conditions,” says Rosenbusch.

The BRD connection

Mycoplasma is the classic “chicken or the egg” disease – does it appear first or is it truly an opportunist that either waits in the wings (or the respiratory tract) or comes in after an infection by something else? Richard Sommers, DVM, believes that Pasteurella multocida is every bit as big a culprit and it works synergistically with Mycoplasma. “Every time I think I’ve got a straight Mycoplasma problem, I almost always have Pasteurella multocida included. If I could control the P. multocida, I could be much more successful in attacking the Mycoplasma.”

Ricardo Rosenbusch, DVM, PhD, believes there are two different views on this subject. “Canadian researchers tie bovine viral diarrhea (BVDV) together with Mycoplasma bovis,” he explains. “The observations in Saskatchewan are that you don’t see Mycoplasma bovis coming into a diagnostic lab without a significant component of BVDV. Their lab is one of the few that consistently uses immunohistochemistry for both of those agents, so they have data that looks a little different from what other diagnostic labs have, simply because methodologies are different.”

In 1998 Rosenbusch did a survey with the Iowa State Diagnostic Laboratory. For a two-month period, any bovine pneumonic case that came into the diagnostic lab was investigated for all possible agents of respiratory diseases that the diagnostic lab could handle. “We found in that group of 100 that we had about 16 we could clearly say were a Mycoplasma bovis outbreak. The immunohistochemistry was there, and culture indicated very high titers.”

In six out of those 16, Mycoplasma bovis was the only significant pathogen isolated. Not surprisingly, P. multocida did come in with some frequency, and so did BVDV. “You can have it both ways,” says Rosenbusch. “It can be a primary, it can be a secondary, it can work by itself or it can work with other agents. Working with other agents would probably be the most common way you would see it.”

Dan Grooms, DVM, PhD, has been closely following the BVDV issue. “We’re trying to find the same things that folks are finding in Western Canada that is evidence that BVDV and Mycoplasma bovis may often work synergistically together.”

One case Grooms worked up involved 144 high-risk calves. Four weeks into the feeding period, the operation started losing calves – 58 out of 144, almost 50 percent. “We did full necropsies on 33 of them, and we isolated Mycoplasma bovis out of 29 of the 33 calves,” says Grooms. “But from 17 out of those 33, we also virus-isolated BVDV. We also found some Pasteurella multocida and M. hemolytica, but not nearly as much as the BVDV and Mycoplasma. Based on this one severe outbreak, we’re more convinced those two pathogens work synergistically.”

Grooms adds that there were other problems in the herd, including that the high-risk, sale-barn calves had never been vaccinated and were put in a poor environment. “But I believe Mycoplasma and BVDV, in some cases, do work synergistically. I believe this is an opportunistic pathogen. It’s looking for an opportunity to set up camp in the lungs and cause damage. If we create the opportunity, whether it’s a viral infection or a poor environment, lack of immunity or poor nutrition, that gives the bacteria a chance to get a foothold in the lungs and start replicating.”

Rosenbusch offers some explanations for how it may work. BVDV is a significantly immunosuppressive agent and will depopulate lymph nodes. “When you depopulate the tonsils, particularly, and then you present Mycoplasma bovis to that animal, that animal is going to have Mycoplasma bovis disease.” The tonsil is a significant route of entry for Mycoplasma bovis.

BVDV is one of those agents that is not necessarily going to be upfront like IBR or BRSV, says Rosenbusch. BVDV will recrudesce, and not nec-essarily because of a persistently infected animal. “I believe BVDV infections flare up and can cause a temporary shedding in feces maybe two to four months into feeding. You can get a wave of BVDV infecting at least some of the population, and that could set the stage for some other pathogens, like Mycoplasma, to flare up.”