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The effect of vaccination on milk production was evaluated in vaccinated and control cows experimentally challenged in two of four quarters with live Mycoplasma bovis. During the first three weeks after experimental challenge, six of eight unchallenged quarters on vaccinated cows and seven of eight unchallenged quarters on control cows became infected. Most of these quarters secreted normal milk, with negative California Mastitis Test scores and maintained normal milk production throughout most of the study (although some quarters on control cows remained infected). All challenged quarters became infected, had strong California Mastitis Test reactions, and had a drastic (greater than 85%) loss in milk production. Thereafter, four of eight challenged quarters on control cows remained infected, had mostly positive California Mastitis Test scores, produced mostly normal-appearing milk, and recovered some productive capabilities. By the end of the study no M. bovis could be recovered from challenged quarters on vaccinated cows and the milk appeared mostly normal. The California Mastitis Test scores on these quarters, however, remained elevated and milk production remained very low.

Typical mycoplasma mastitis spread to all four quarters in each of four cows after each cow was inoculated in one quarter with 70 colony-forming units of Mycoplasma bovis. Up to 50 days after inoculation, immunoglobulin (Ig) M was the predominant Ig responsible for serum indirect hemagglutination titers. After 57 days, IgG was predominant. Milk whey indirect hemagglutination titers did not distinguish between quarters resolving the infection and those that did not. Milk whey IgG and IgA concentrations increased in quarters that resolved the infection and in quarters that did not. In the initially inoculated quarters, total daily production of IgG was greater in the quarter resolving the infection than in the three quarters not resolving the infection. Total IgA production was also higher at and after the peak of infection in the quarter resolving the infection than in the quarters that did not.

Most bovine mastitis due to mycoplasmas is initiated by passage of mycoplasmas through the teat canal into the teat and gland cisterns. Within a few days, mycoplasma numbers increase to as much as 10(6) or 10(8), and the cows react with a strong inflammatory response. Alveolar epithelium undergoes degenerative changes and exudate replaces milk secretion. The interstitium between alveoli is invaded with lymphocytes, macrophages, plasma cells and fibroblasts. The extent and duration of these changes vary greatly. In milder cases, they may be reversed within days or weeks with a return to normal or reduced milk production. Often, destruction and atrophy of alveoli are complete with extensive fibrosis throughout the udder. Milk ducts may undergo invasive and obliterative fibrosis. Cell-mediated responses are suppressed, while hypersensitivity is suspected of enhancing the adverse responses. Immunity in cows that recover is variable and of limited duration.

Seven teat dip and sanitizer products were tested in vitro and in vivo for mycoplasmacidal activity against Mycoplasma agalactiae subsp. bovis (M. bovimastitidis). Most, but not all products tested appeared to kill the mycoplasma at satisfactory dilutions. These mycoplasma survived longer on teat skin during humid, rainy weather than during warm, dry weather. Acholeplasma laidlawii was frequently found on normal teat skin.

This study characterized the immune responses in four vaccinated and four control cows in response to vaccination and experimental intramammary inoculation with Mycoplasma bovis. Specific antibody responses occurred in serum and milk in response to vaccination and experimental infection. Lymphocytes from peripheral blood, but not from the mammary gland of vaccinated cows had increased responsiveness to mitogens. No lymphocytes tested were responsive to M. bovis antigen. Both vaccination and experimental infection resulted in skin test reactivity. These results imply that vaccination results in immune responses which may alter the course of experimental M. bovis mastitis, but may contribute to cellular inflammation.

Rabbits were given 3 serologically-related trains of mycoplasma isolated from mastitic bovine udders. Growth inhibiting antibodies were not found. High-titered sera from each rabbit immunized with each strain developed at least 4 precipitin lines to each organism and at least one line of identity was demonstrated between the organisms. Significant indirect hemagglutination titers were found in all rabbits in 1 week, with titers reaching 1.0 X 10(5) to 3.3 X 10(5) in 4 to 6 weeks but despite continued intravenous antigenic stimulation, titers quickly fell to low levels thereafter.

Coliform organisms were isolated from bedding, udders of cows exhibiting acute or chronic mastitis, and milk of cows tested for udder pathogens. The bactericidal activity of standard bovine serum was tested on 362 isolates, of which 2.4% were killed at a serum dilution of less than 1:5; 2.7% were killed at a dilution of 1.5; 3.0% were killed at a dilution of 1:12.5; and 4.4% were sensitive to a dilution of 1:25. Organisms isolated from mastitic udders were not killed by serum. Sensitivity to agglutination in 1:500 solution of acriflavine was tested on 157 isolates, and only 54 had any degree of agglutination. Of these 54, only 4 organisms had any susceptibility to killing by serum. Results suggest that most organisms in the environment of the cow are resistant to serum, few serum-sensitive coliforms cause mastitis, and agglutination in acriflavine (indicating organisms in the rough phase) does not correlate with sensitibity to serum.

A dairy herd having a high incidence of coliform mastitis was observed by means of pre- and post-milking samples and teat apex culture. Infected quarters were the major source of teat apex contamination with coliform bacteria and therefore constituted a risk to unifected quarters and to other cows. Coliform populations on the apex from environmental sources appeared to be transitory.