The Growing Problem of Mycoplasma bovis

Q: What is Mycoplasma bovis?

A: Mycoplasma organisms cause some of the most serious and costly cattle

diseases. Of these, Mycoplasma bovis seems to be the most common cause of clinical problems. Research has shown that Mycoplasma bovis is a major, but often overlooked pathogen, which causes respiratory disease, arthritis and mastitis in cattle. When it was first isolated in the U.S. in the 1960s, it seemed to occur infrequently, but now the infection has become widespread. Today, many cattlemen are seeing substantial rises in death rates and chronics from Mycoplasma bovis in beef cattle of all ages. Once established in a herd, it is almost impossible to eradicate.

Q: What is Mycoplasma bovis costing the industry?

A: In this country, economic damages to the beef industry have been estimated at $32 million a year, mostly through losses in weight gain and carcass value. For the dairy industry, losses that come largely from therapy-resistant mastitis infections are estimated to be $108 million per year.

Q: How is Mycoplasma bovis transmitted?

A: Mycoplasma bovis is commonly found in the upper respiratory tracts of cattle, and can also often be found in their urinary and reproductive tracts. It is highly contagious and moves between animals in several ways. Most common is aerosol transmission: through the air by nasal secretions and coughing. Routes for oral ingestion can include fences, troughs, nipples, and buckets. It can travel from infected animals to uninfected ones through direct contact, milk, or with infected semen.

Infected cattle shed Mycoplasma bovis via the respiratory tract for months and even years, acting as reservoirs of infection. While it’s unclear what causes it to become virulent, stress seems to be an important factor in the induction of disease.

Q: What are the symptoms and effects of Mycoplasma bovis?

A: In beef cattle, a Mycoplasma bovis infection may begin as part of a general respiratory problem that doesn’t respond to the usual courses of antibiotics. The symptoms of these pneumonic cattle may differ from those of other types of pneumonia. The animals may stay bright and alert much longer. The muzzle, instead of becoming dry and cracked, drips with a clear, or nearly clear, thin mucous. Eyes may remain bright. A harsh, hacking cough is common and breathing may not be labored at first, but is more rapid than normal.

After entering the respiratory tract, Mycoplasma bovis can invade tissues and liberate toxins that can cause severe tissue damage. It can enter the bloodstream and spread to other tissues or body systems: joints, ears, eyes, and udders. Once in the joints and tendons it can cause arthritis/tenosynovitis. The conditions are progressive and can result in death.

Q: What options are available to treat Mycoplasma bovis?

A: Treating Mycoplasma bovis is problematic for several reasons. The first issue is that early treatment is essential to any degree of success, but early diagnosis is extremely difficult. Because it is generally a secondary infection, its symptoms can be masked by those of the primary infection. In fact, a Mycoplasma bovis diagnosis isn’t usually made until lab cultures are confirmed — often in a postmortem exam.

The next issue is the lack of effective antibiotics. Because the Mycoplasma bovis bacteria lack a cell wall, they are resistant to most antibiotics, which kill bacteria by destroying their cell walls. And evidence is accumulating that strains of Mycoplasma bovis are becoming resistant to the antibiotics traditionally used for their control.

Some experts suggest that long-acting oxytetracycline be given three to four times at 72-hour intervals in order to maintain optimum drug levels for 10 to 14 days, though clinical trials have not been done to validate this.  Finally, even if animals do recover from a Mycoplasma bovis infection, they are likely to remain unproductive and to lag behind their healthy counterparts. Because effective treatment is elusive and Mycoplasma bovis is common in cattle, managing to prevent an outbreak is the most practical solution for producers. Now control efforts can also include vaccination with Pulmo-Guard™ MpB, a new vaccine from Boehringer Ingelheim, to avoid costly outbreaks of Mycoplasma bovis.

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