From the NMC Newsletter "Udder Topics", April-May 2001

Source
The primary sources of Nocardia species are soil, water, air, grass, and udder skin of cows.

Means of spread
Contaminated treatment or treatment devices, and improper teat sanitation prior to treatment are common means of spread. Nocardia spp. can possibly be transferred from environment to cow, and from cow to cow at milking.

Basic prevention and control measures
Aseptic intramammary treatment infusion and single dose sterile treatment tubes should be used. Eliminate infected cows from the herd and identify sources of infection if multiple cases occur.

Miscellaneous information
Hard nodules or extensive fibrosis may be found during palpation of affected quarters (wood consistency). Udder secretion may be purulent and affected quarters may develop draining sinus tracts. Infected cows may develop mild or high fever. Nocardia spp. infections are refractory to antibiotic treatment.

Culturing comments
If a herd or cow is suspected to have Nocardia mastitis, milk samples must be cultured as soon as possible after collection because storage of samples in a refrigerator or a freezer can jeopardize the isolation of the organism.

Source: NMC Publication "Laboratory and Field Handbook on Bovine Mastitis" (1999) pg. 127.