M. bovisinfection in stocker cattle

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During the 2008 Midsouth Stocker Conference, attendees had an opportunity to hear from University of Tennessee Extension veterinarian Fred Hopkins, Large Animal Clinical Sciences veterinarian Matt Wellborn and University of Tennessee Extension beef specialist Warren Gill about the impacts of Mycoplasma bovis infections in stocker cattle.

According to the presenters, M. bovis infections can result in pneumonia, joint swelling and middle-ear infections in stocker calves. There are several strains that vary in their ability to cause disease and more than one strain can infect a calf.

The risks of commingled cattle become magnified when there is an M. bovis infection present, as the organism can be spread through aerosol droplets, close contact, as well as contaminated watering troughs or feeders. An outbreak will typically occur two to four weeks after the arrival of new cattle.

Most cattle are exposed to this bacterium at some time in their lives and may spread the disease for weeks after exposure, and, according to Hopkins and his colleagues, the organism can survive for three weeks on hay and two weeks on a waterer. Stress can increase the likelihood of M. bovis infection and the organism often infects cattle in concert with other pneumonia-causing organisms including the bovine viral diarrhea virus, M. hemolytica and P. multocida, which can lead to more severe pneumonia cases.

Detecting an M. bovis infection can be challenging as symptoms can be difficult to recognize early in the disease and hard to differentiate between other causes of pneumonia. You should watch for the following:

  • Low-grade fever
  • Calves that will still eat, but come to the bunk more slowly
  • Calves that are not as depressed as other calves affected with pneumonia
  • Rapid breathing and a moist cough
  • Clear nasal and eye discharge
  • Swelling along the back
  • Tilted head and dropped ears
  • Stiffness and lameness, especially in the upper joints, appears in about 25 percent of affected calves
  • Poor treatment response.

If your calves do become infected with M. bovis, you can expect up to a 30 percent death rate with many calves becoming chronic poor doers. M. bovis infections can be difficult to treat because it mutates easily and many commonly used antibiotics act on bacterial cell walls, while M. bovis does not have a cell wall. The presenters recommend focusing treatment on other sources of pneumonia infections, so that the calves’ immune systems are better able to deal with the M. bovis infection.

Treatment success for an animal with pneumonia complicated with Mycoplasma bovis can only be judged after 10 days to two weeks of therapy. Unfortunately many producers stop or change antibiotic therapy too soon to reap the results.

Prevention of M. bovis is difficult, but some strategies include the following best management practices:

  • Clean and disinfect feeders and waterers before a new group of calves arrives.
  • Buy single-source calves that have been vaccinated prior to arrival.
  • Don’t allow nose-to-nose contact between new calves and calves already on your operation.
  • Manage newly arrived calves so that they eat and drink as soon as possible.
  • Make sure calves are not overcrowded and have adequate feed bunk and watering space.
  • Vaccinate on arrival using a modified live virus vaccine against IBR, BVD, PI3 and BRSV, as well as a vaccine effective against M. hemolytica and P. multocida. Booster vaccinations should be given according to label directions regardless of previous vaccinations.
  • Mycoplasma vaccine may be of some help if the strain on your operation is similar to the vaccine strain.
  • Mass treatment of newly arrived calves using florfenicol, tulathromycin, tilmicosin or long-acting tetracycline may be of some help.
  • Chlorotetracycline in the starter ration may also be of some benefit.

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