Ask the Expert: Managing Mycoplasma

A: Mycoplasma bovis is a common problem in calves, contributing to pneumonia, the classic ear infections with dropped ears, and joint infections. Whenever a herd has cows diagnosed with Mycoplasma, the calves are considered to be at-risk too. And, just as important, any time a calf is diagnosed with a positive culture for Mycoplasma, at the very least bulk tank screening should be done because the cows are often the source of the infection in the calf.

The organism is slow growing, taking three to seven days in the lab to identify, but it makes up for this slow growth by producing huge numbers of organisms so that a single drop of milk is a risk to cows milked after an infected cow as well as calves fed raw milk or raw colostrum. That single drop of milk can be on a milker’s hands, calf feeding equipment, a fresh cow bucket, or a calf pail, and infect several calves.

The good news is the organism is easy to kill with disinfectants and pasteurization because it lacks a cell wall. The bad news is that many of the antibiotics used to treat bacterial infections work by damaging the bacterial cell wall, so they do nothing to the Mycoplasma organism.

Once calves are infected again, the infection is often slow to express itself, so it may be several weeks before we see the symptoms. Dropped ears is an easy way to diagnose and I assume that any calf with an ear infection has Mycoplasma.

With calf pneumonia, Mycoplasma likes to team up with other bacteria and there is no way to tell what bugs are actually involved in the pneumonia without good samples for a diagnostic lab. That said, I like to use an antibiotic that has a label claim for Mycoplasma when I’m treating calves with respiratory problems. With joint infections, I usually do a joint tap and culture the fluid to identify the cause.

Remember, the best medicine is prevention. Because pasteurization kills Mycoplasma, it is a valuable tool in keeping your calves healthy while they are at risk if they are fed any fresh milk or colostrum.