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Mycoplasma, a relatively new but uncommon mastitis

Dairy Pipeline: August 1998

G. M. (Jerry) Jones
Extension Dairy Scientist, Milk Quality and Milking Management
Virginia Tech
540/231-4764, e-mail:

Recently, I have heard of several dairy farms that have experienced mastitis as bad, or worse, than that caused by Staphylococcus aureus. These MYCOPLASMA infections also are contagious, because they are spread from cow to cow at milking, and may occur in cows whose previous cultures were negative. Symptoms include clinical mastitis in more than one quarter, often all four quarters. Milk secretions vary from watery, with a few clots, to colostrum-like or tannish color with sand-like or flaky sediments. DHI has refused to test some samples because of an extremely dirty appearance which would foul their equipment. Response to antibiotic treatment is poor. From a few weeks to almost a year before mastitis begins, increased coughing may occur in cows, heifers, and calves. Animals may have swollen hocks with increased fluid. In addition to mastitis, cows have had abortions and low fertility, arthritis, and pneumonia. Milk production can be drastically affected. Stresses such as calving, extreme temperature variations, and transportation accelerated the development of the condition. The young can become exposed during calving through direct contact with the urogenital tract, nasal discharges, and milk from shedding animals. The infection can be isolated from either bulk tank or samples from cows with clinical mastitis. In one herd, MYCOPLASMA infections were found in four highest SCC cows (over 6 million) and 6 of 13 cows with highest SCC (all above 3,200,000). Special culture media and incubation techniques are required to isolate the infection. Once cows are found positive, they should be considered infected for the rest of their life. Sources of infection include introduction of new cattle into herd from other farms and nonhygienic intramammary treatments. Ohio found that 26% of herds used treatment products not commercially labeled for such use and two out of nine such herds had MYCOPLASMA infections present. Herds with MYCOPLASMA infections need to consider: reducing stress such as overcrowding, milkers wearing gloves, milking cows with separate milking units, units equipped with automatic backflush, manually flushing units after infected cows, milking infected cows last, culling infected animals, and use of commercial treatment products which have been packaged under sterile conditions. It is unknown whether contaminated equipment, clothing, treatment devices, sampling meters, etc. or any type of improperly cleaned materials could bring the organisms onto the farm. Herds should predip and post dip as well as dip teats before and after intramammary treatment using a dip cup rather than teat spray. New animals into the herd should be cultured and isolated until found negative.

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