Feed Lot Magazine Online, The Mycoplasma Problem in Stocker/Feeder Cattle

Mycoplasmosis has assumed crisis proportions in some groups of calves. Reports of death, chronic respiratory and crippling lameness losses in excess of four percent are frequent and horror stories of eight to 12 percent losses are not uncommon.

The disease was first reported in the seventies. It occurred only infrequently and sporadically in stocker/feeder calves until the last couple of years. Today, while clearly not all cattle have the problem, many do. The infection is wide spread and at times may be devastating.

In the past two years Texas Vet Lab, Inc. has received samples that were positive for Mycoplasma from over 88 herds of stocker/feeder calves from sixteen states. Sixty-eight isolates were tested for specific identification and Mycoplasma bovis was identified in all of those samples.

Mycoplasma bovis is a tiny, tiny bacteria. It is smaller than some viruses. It is transmitted calf to calf, nose to nose, and through the air. It enters the respiratory tract and causes progressive bronchopneumonia. The organism may -- and frequently does -- migrate through the blood to the joints and tendons where it causes a crippling arthritis/tendosynovitis.

The symptoms differ from those of Pasteurella haemolytica and Haemophilus somnus pneumonia. The calves stay bright and alert much longer. The muzzle does not become dry and cracked; in fact a drippy nose, with clear or nearly-clear, fairly thin mucous, and a bright, clear eye are characteristic. Coughing is also common. The cough is a harsh hacking cough. Old timers may think it sounds like calves used to sound with lungworms. Early on the calves do not exhibit labored breathing, but they do breathe more rapidly than normal.

They will move with the herd, but they tend to lag behind. Their appetites are depressed; they go off feed and shrink. Advanced cases draw down almost to nothing, get weak, and die. Some folks have called it the "dry-up disease."

The temperatures tend to be not as high as with Pasteurella haemolytica or Haemophilus somnus, 103.5 to 105, being common. Intercurrent infection with Pasteurella haemolytica or other agents may make the temperature higher.

Lameness due to Mycoplasma bovis infection in the joints and tendons may occur in up to ten percent of the cattle. Lameness is not, however, a feature in all instances.

Ear infection, characterized by a drooped ear or ears, may also occur, but seems to be less common than lameness. The drooped ear makes you think that there are ticks in the ear, but when examined no ticks are found, only large amounts of cheesy waxy exudate. The scat of lameness is in the knee or hock or above, in the hip, stifle, shoulder or elbow. The lameness is often so severe that the muscles perish and just wither away. The affected calf may get so lame that it won't go to feed or water. It gets down, dries up and dies. Lameness and ear infections are just the tip of the iceberg. Pneumonia is the main problem and generally the biggest cause of loss.

The pathology in the lungs is different from that of Pasteurella haemolytica or Haemophilus somnus. It is a very distinct broncho-pneumonia with abundant exudate and limited or no fibrin deposit. The bronchioles and alveoli (air sacks) become filled with a yellow cheesy exudate.

Multiple abscesses which vary from the size of a pinhead (probably start the size of a pinpoint) to a diameter of an inch or more are characteristic of chronic cases. In protracted cases, the bulk of the lung may become filled with yellow cheesy exudate. Acute cases are a bit more difficult to understand. Large areas of the lung may become hyperemic and turn a plum-purple color. There may be white areas interspersed in the purple areas. These occur as a result of disruption of the blood supply. Subacute and chronic cases with accumulation of the yellow cheesy exudate are much more commonly seen.

Treatment is a problem. Early treatment is essential to success. It is very easy to overlook early cases, or to put them off to treat another day because they don't look all that sick. A day later the infection is much more en-trenched and difficult to deal with. To make matters worse, Mycoplasma bovis is usually resistant to most antibiotics. Veterinary consultation and sensitivity testing are of paramount importance in selecting the best treatment program.

The old adage "an ounce of prevention is worth a pound of cure" has never been more true than it is with the management of Mycoplasfmosis. Stressed cattle are considerably more susceptible to Mycoplasmosis than non-stressed cattle. Everyone in the industry knows about stress so there is no point in belaboring the issue, but it is worthwhile to note that trucks are not the only things that stresses cattle. Intercurrent disease such as sale barn scours, Pasteurella pneumonia, excessively strong virus vaccination programs, bad water and improper nutrition all add insult to injury and make calves much more susceptible to Mycoplasmosis.

Incorporating autogenous Myco-plasma bacterin into an appropriate vaccination program combined with good management and care has been beneficial. An over-the-counter Mycoplasma bacterin which will be readily accessible to all producers from local animal health dealers and veterinarians is expected to be available soon. Vaccination by itself will not and probably never will completely control this disease; however, an appropriate vaccination program coupled with good management and a dedicated effort of all concerned can yield gratify- ing results.