A summary of selected papers presented at the 2002 National Mastitis Council Meeting
Dr Ingalls summarizes the following papers presented at the 2002 National Mastitis Council Meeting
Staph. Vaccines: What are the New Strategies?
Phil Sears, Michigan State University
East Lansing, Michigan
Vaccines for Streptococcal Pathogens Have Arrived
Andy Potter, Veterinary Infectious Disease Organization
Saskatoon, Saskatchewan, Canada
Novel Applications for Coliform Vaccine Programs
Jeanne Burton, Michigan State University
East Lansing Michigan
Contagious mastitis is a problem on a number of farms. Prevention is often a successful approach; however, complete elimination may not be practical in expanding herds. A frequent management suggestion is to cull or segregate infected animals. Because this approach is not always feasible, vaccines for contagious mastitis are desirable.
Staph. aureus vaccines:
Dr. Phil Sears, of Michigan State University, summarized the state of Staph aureus vaccine development. A number of approaches are currently in the testing stages, varying in how they interfere with Staph aureus’ ability to infect the mammary tissues.
Staph aureus, through special mechanisms, is able to avoid attack by neutrophils (somatic cells). This means that somatic cell action may be ineffective in killing Staph aureus. Study of these mechanisms has led to production of experimental vaccines. These experimental vaccines are designed to prevent Staph aureus from resisting neutrophil action.
Staph aureus rely on a skin attachment mechanism to attach to skin and milk secreting tissue. This is the first step in establishing a new infection.
Vaccines aimed at blocking this attachment have been tested with some positive results.
Staph aureus tend to produce capsules around themselves that help protect them from somatic cells. These capsules have been widely studied and anti-capsule vaccines have been tested with some encouraging results.
There is no vaccine that provides absolute protection against Staph aureus at this time. Currently, a combination of dry cow treatment, post-milking teat dipping with effective products, and segregating and/ or culling chronically infected cows are still the main defenses against Staph aureus. Vaccines may provide additional safeguards in the future but a diversified defense will likely remain the best approach.
Environmental Strep vaccines:
Streptococcal species of bacteria such as Strep uberis and Strep dysgalactiae have come to be major mastitis threats. Conventional methods of mastitis control are often ineffective, since these bacteria are common in the cows’ environment. As a result, cows are continuously re-exposed to these bacteria. These facts make a vaccine development particularly critical in reducing mastitis caused by environmental Streps.
Understanding the mechanism of infection for environmental Strep. species is critical to developing a preventive vaccine. Dr. Andy Potter and his group at the Veterinary Infectious Disease Organization in Saskatchewan, Canada, have identified features in these bacteria that may allow for vaccine development. A major objective of their work has been to identify antigens for Strep. dysgalactiae and Strep. uberis that will provide protection against a wide variety of strains. Their experimental results have identified some promising antigens. This research group is optimistic that effective vaccines against environmental Strep. species will be available in the not too distant future.
Vaccines effective against coliform mastitis are currently available and commonly used to protect cows around time of calving. Several studies have suggested that efficacy of the current “J5” vaccines are decreasing. The antibody response produced by these vaccines appears to vary considerably in quality, quantity, and consistency. Michigan State University researchers have proposed that increasing milk yields might be diluting the antibodies produced by J5 vaccination, thus reducing effectiveness. Additionally, there is some evidence that the currently recommended vaccination schedule for J5 vaccine does not allow adequate time for the cow’s immune system to respond fully.
In the 2002 NMC proceedings, Dr. Burton et al. of Michigan State University presented ideas on improving the efficacy of existing J5 vaccines to prevent coliform mastitis. Hyperimmunization was one method that was tested. In hyperimmunization, at least 5 vaccinations were used to stimulate the immune system. Initial results are promising, although more thorough testing is required. Additionally, the cost-benefit ratio for hyperimmunization has not been determined.
A second procedure tested by this Michigan State group was to generate highly purified antibodies to use for passive immunization. The preparation of purified antibodies is to be infused into the mammary gland to provide protection against coliform mastitis organisms. Testing has not been concluded; however, the researchers hope for nearly complete protection against coliform mastitis for cows at freshening.
British Mastitis Council
This link takes you to the British Mastitis Council site where you can find articles from previous meetings as well as the program for the 2002 meeting