A producer survey on mycoplasma sheds light on some common misperceptions about the factors that can initiate a flare-up.
For the past four years, reports of mycoplasma have been on the rise, says Mark Spire, a Kansas State University (KSU) veterinarian.
“At first it was individual cattle, then loads of cattle with non-responsive pneumonia and subsequent arthritis syndrome,” Spire says. “This spring we started to see a lot more chronically sick calves. These calves just don't grow, and when they hit the summer heat, they really fade.”
The case reports have come from producers, consulting vets and diagnostic lab personnel across Texas, Oklahoma, Kansas and Nebraska. Most of the cattle have been stockers, but feedyards also have reported problems.
The progression of the disease usually unfolds like this:
Two weeks after arrival, the calves pulled for treatment of pneumonia show no response, even after treatment with two different antibiotics. The calves often eat well, but those pulled are depressed, have clear nasal discharge and often seek shade.
Three weeks after arrival, arthritic calves are being pulled. Lameness doesn't always occur in a group. But if it does, the calves exhibit lameness and joint swelling in the knee, elbow or fetlock joints. At times, several joints are involved simultaneously.
The conditions are progressive. Affected calves end up thin, dehydrated and depressed. Most death loss occurs between three and six weeks after arrival. By six to seven weeks after arrival, the outbreak stops with little additional sickness or death loss.
Most often, these sick cattle are diagnosed with pneumonia and undergo a regular pneumonia treatment routine, Spire says. A mycoplasma diagnosis generally isn't made until a postmortem is performed.
In fact, Spire says the KSU Vet Diagnostic Lab has found Mycoplasma bovis organism in more than 70% of lungs from pneumonic calves submitted for culture work. Just what initiates an outbreak of mycoplasmosis, however, is still undetermined.
“The organism appears to be ubiquitous and an opportunist,” Spire says. “And, about anything and everything has been blamed as a contributing factor to initiating this syndrome,” he says.
In actuality, little is known about the management factors that play a role in initiating a mycoplasma outbreak. So, Spire, his KSU colleagues Dale Blasi and Jan Sargeant, and Ricardo Rosenbusch of Iowa State University decided to survey Kansas stocker operators.
A total of 887 producers were given the disease descriptor listed above and asked if they had received loads of cattle within the past 12 months with those clinical signs. A total of 228 returns were analyzed.
The key findings were:
Heifers and steers are affected about the same.
The syndrome was reported across all operation sizes. The bigger the operation, the more likely they are to have a problem.
Though reported across all weight classes, the problem is more likely in lighter weight cattle.
As the number of loads received during winter increases, the more likely an outbreak will occur.
The syndrome was reported in cattle received from all areas of the U.S, but cattle received from the western U.S. were not as likely to have a problem.
If an operator buys from a single source regardless of the region of the country (Southeast, Southwest or Northeast), they are less likely to have reported a problem than if they buy from multiple sources across several states.
Home-raised calves or cattle sourced in Kansas are less likely to have a problem. Spire attributes this to less shipping stress.
The type of antibiotic used in metaphylaxis or treatment programs does not appear to be a reason for an outbreak.
Use of modified-live viral vaccines does not appear to be a factor in outbreaks.
Herds reporting as having the problem have twice the incidence of pneumonia than herds reporting not having a problem.
Increasing stress by castrating and dehorning may increase the likelihood of having a problem.
Single Sourcing Helps
Spire says the operators responding to the survey handled an average of 1,140 stockers/year and received nearly 15 loads of cattle. Calves were received year round, with the majority (63%) received in spring and fall. Half the calves were of Kansas origin. Average weight was 493 lbs., and most were steers.
“In this survey, we found that the folks who had mycoplasma in their cattle on average received cattle from 2.7 states. Those with the lowest incidence received cattle on average from 1.8 states,” Spire says. Of operations reporting mycoplasma, Spire adds that on average 15% of the loads had outbreaks.
The results, Spire says, indicate that operators would benefit most by single-sourcing cattle. Reducing stress at incoming also should be emphasized.
“You also need to vaccinate those cattle to control other respiratory pathogens and make sure that cattle go on feed well and are receiving a balanced trace mineral program,” Spire says.
“The lighter the cattle, the better the chance they'll have a mycoplasma problem,” he adds. “Older cattle seem to handle the stresses of transportation and dietary changes better. Older cattle also seem to build up some immunity.”
Much is yet to be learned about mycoplasmosis, Spire adds. He says that due to the complexity of the organism, vaccines are generally ineffective or will require two to three doses to work at optimum.
“Number two is that we don't have antibiotics that are highly effective against this organism, either. And, number three is that because the organism is found in a high percentage of ‘normal’ cattle, we don't understand what necessarily triggers it to make it virulent,” he says.
Normally, Spire says 75% of sick cases in stocker cattle are respiratory in nature, and 1% are due to lameness, mostly lower foot. Of these respiratory cases, 85-90% can be expected to respond to first treatment.
“In mycoplasma, however, only 50% will respond to first treatment because the effectiveness of drugs has really been diminished. There is also lameness as high as 20% in mycoplasma cattle, and the lameness occurs higher on the leg,” Spire says.
“And, where we'd expect 1.5% death loss as average, mycoplasma will push it to 3-5%. That's one factor that always gets the diagnostic laboratories suspicious of mycoplasma.”