From the NMC Newsletter "Udder Topics", October-November 1999

Source
The primary sources of Mycoplasma species are infected udders, respiratory tracts, and urogenital tracts.

Means of spread
Mycoplasma spp. are spread from cow to cow at milking. Other sources include contaminated intramammary treatments and treatment devices, contaminated hands, and airborne transmission in poorly ventilated barns. Mycoplasma mastitis can result from hematogenous spread from the respiratory or urogenital tract to the udder.

Basic prevention and control measures
Maintain a closed herd. If animals are purchased, buy replacements from known Mycoplasma-free herds. Culture all replacements before commingling with the herd, and pregnant cows and heifers at calving. Extreme hygiene is necessary in both milking and management practices to control the spread within a herd. Segregate and milk infected cows last or with a separate milking unit. Use an efficacious pre- and post-milking germicidal teat disinfectant. Remove infected cows from the herd when conditions do not allow for segregation. Bulk tank samples may be cultured periodically to monitor for presence of Mycoplasma spp. in a herd.

Miscellaneous information
No treatment is effective against mycoplasmal mastitis. Mycoplasmal mastitis is characterized by:

-- Cows have clinical mastitis in more than one quarter at the same time.
-- Milk samples from clinical cases of mastitis are negative on routine culture.
-- An increase in the number of severe clinical cases of mastitis that resist antibiotic treatment.
-- Milk production of affected cows decreases dramatically and in severe cases some cows may cease lactating.
-- The mastitis outbreak was preceded by respiratory disease in bovines of different ages on the farm.

Sample collection
Milk samples collected for culturing Mycoplasma spp. should be kept cool and plated within a few hours of collection to maximize isolation. If delay of more than a day is anticipated, samples should be frozen or stored in liquid nitrogen.

Culturing comments
Mycoplasma spp. will not grow on blood agar incubated aerobically. When grown on mycoplasma medium, Mycoplasma spp. colonies usually have a fried-egg appearance.

Source: NMC Publication "Laboratory and Field Handbook on Bovine Mastitis" (1999) pg. 151.