Mycoplasma

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Description:

Mycoplasma is a group of bacteria that lack a cell wall, are smaller than most bacteria, and need cholesterol to survive. Mycoplasma bovis is known to cause respiratory infection in cattle and has been associated with pneumonia, arthritis, tensynovitis and other disorders such as mastitis, otitis and sinusitis. Mycoplasma bovis is commpnly isolated from both dairy and beef claves suffering from non-responsive respiratory infections and pneumonia.

Etiology:

Mycoplasma bovis can act as a primary or secondary respiratory pathogen. Most often, Mycoplasma infects an already weakened calf suffering from a viral infection such as IBR. However, there is evidence showing that Mycoplasma bovis can infect otherwise healthy calves and cause clinical signs of disease. Mycoplasma can be found in the respiratory secretions of normal healthy cattle and sick cattle. Even dairy calves with no signs of respiratory disease can have mycoplasma present in their respiratory tract. It is believed that mycoplasma can spread from a few animals carrying the bacteria to other animals within the herd via respiratory secretions, direct contact and aerosol. An additional source of mycoplasma infection comes from feeding calves milk infected with M. bovis.

Symptoms:

The signs of respiratory disease caused by Mycoplasma bovis include fever, rapid respiratory rate, inappetence, coughing, and nasal discharge. Infection with mycoplasma can occur as an outbreak in dairy calves with a portion of the affected animals developing ear infections or arthritis. Weaned beef calves entering feedlots may develop arthritis and tenosynovitis secondary to mycoplasma-related respiratory infection. The typical presentation of a Mycoplasma bovis infection would be to see animals failing to respond to treatment and instead remaining chronically ill and unthrifty. Necropsy finding suggestive of Mycoplasma bovis infection include dark red, firm, consolidated lobules within the crainioventral lung along with raised white or yellow nodules. Infected animals also often have arthritis in at least one joint characterized by lots of yellow fluid and fibrin within the joint capsule.

 Diagnosis:

Mycoplasma bovis can be diagnosed using bacterial culture or IHC along with clinical signs and necropsy findings. It is best to identify the organism in a number of postmortem cases to help prove Mycoplasma bovis is the causative agent in a respiratory disease outbreak in calves. Identifying Mycoplasma bovis is not the same as identifying Mycoplasma spp so one must specifically request that the organism be identified to the level of genus. This can be done with PCR or immunoflourescence. Given that Mycoplasma bovis can be isolated from healthy calves, culturing this organism from nasal secretions does not necessarily mean that it is the cause of a given respiratory disease. Thus it is useful to look for arthritis or other associated conditions when trying to determine whether Mycoplasma bovis is responsible.

Treatment:

Mycoplasma bacterial infection can be treated with antibiotics. Mycoplasma infection can be treated with several antibiotics, including the tetracyclines and macrolides. Draxxin (Pfizer), Nuflor, and Batril have all been effective in treating mycoplasma in cattle, but Draxxin (Tulathromycin) is the only drug approved for treating Mycoplasma bovis in cattle. The most important things to keep in mind when treating mycoplasma infections is that treatment is most effective if infection is identified early and treatment is prolonged (often 10-14 days of antibiotic therapy).

Prevention:

The most important aspect of prevention of Mycoplasma pneumonia is to reduce the stressors to which cattle are exposed. This is because most mycoplasma infections are secondary to a virus or other infection such as occurs with bovine respiratory disease complex or shipping fever. Thus, the same practices that lower the risk of BRDC work best to decrease the risk of Mycoplasmosis. These strategies include good vaccination, nutrition, and mineral programs to strengthen the immune system of calves and avoiding stressful situations such as overcrowding. Vaccines against Mycoplasma bovis are available, but have not been proven effective in beef cattle. Some vaccines available are Pulmo-Guard and MpB Guard.
  

Sources: 

Anderson, D.E., Rings M.D. Current Veterinary Therapy: Food Animal Practice, 5th Ed. Saunders, St. Louis MO. 2009. pp. 192-193.

Smith, B.P. Large Animal Internal Medicine, 3rd Ed. Mosby-Elsevier Publishing. St. Louis, MO. 2009. pp.621-625.

Merck Veterinary Manual Online: http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/121217.htm&word...
 

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