Other Management Articles
- Building A Herd of High-Producing, Healthy Cows with Low Involuntary Culling
- Culling Heifers: When and Why and the Impact on Herd Economics
- Economics Matter in Culling Decisions
- What is an ideal BCS at calving?
- Facts about Somatic Cell Counts
- First Layer of Defense Against Mastitis
- The When and Why of Milking Procedures
- Are Mastitis Vaccines a “Cure All”?
- Growing Heifers to Be Your Best Cows
- A Look in the Mirror
- Fertility Potential: The Bull + The Cow + The Inseminator + The Environment
A vaccine against mastitis has been the magic that producers have long sought. Imagine a vaccine that eliminates the need for equipment maintenance, proper milking procedures, genetic improvement, and environmental management. Is that too good to be true?
Yes, but there are areas where specific vaccines can be integrated into mastitis management practices. The goal of a vaccine is to prepare the udder to fight the disease faster and more effectively by signaling local cells to quickly respond to infection and create an immunoglobin (antibody) response that reaches into the milk and udder, helping white blood cells (which form the majority of a cow’s SCC) to clear up the infection.
Different vaccines have different levels of protection. Management must consider the level of protection that can be achieved with a mastitis vaccine, provided they choose to integrate it in their mastitis control plan. The gold standard, highest level, is prevention of infection. This would prevent all colonization or replication of the mastitis agent. To assume this, there should be an extremely high degree of confidence based on research. This level of protection is hard to achieve with vaccines against mastitis. Many producers assume their vaccine is achieving this level, but most are not.
Reducing the severity of the disease is the next highest level of protection. This would mean that bacteria still enter the udder and replicate there, but do not cause clinical mastitis or illness. These mastitis vaccines would be highly effective in preventing clinical disease in vaccinated cows. We should expect about 80% prevention of disease compared to a control (placebo) group if the vaccine claims this level of protection. This is another example where dairies often assume higher prevention levels than most vaccines provide. Coliform vaccines can provide this, but few other vaccines achieve this level of protection.
An aid in disease prevention is the most common level of protection of many mastitis vaccines. For example, Staph aureus vaccines are extremely poor in their ability to provide protection in lactating cows but may have some benefit in pregnant heifers. These vaccines offer some prevention of mastitis in vaccinated animals but are weaker than the strong threshold we expect for full prevention of infection or disease. Many mastitis vaccines may be effective at this level of disease control. These mastitis vaccines alleviate disease severity, reduce disease duration, or delay the progression of disease and reduce mortality.
Some mastitis vaccines may have claims beyond direct disease control, such as control of or reduction in shedding of contagious mastitis-causing bacteria. This can be a benefit or a hindrance in a mastitis control program in that it may prevent the identification of infection carrying cows.
The safest and most tested vaccines will be commercially available vaccines. Some herds choose to create autogenous vaccines in response to a specific pathogen on their farm. Autogenous vaccines take an infectious agent from a particular farm and create a vaccine for that specific infection. Mastitis protection is hard to achieve with this type of vaccine, and the outcome is extremely hard to measure.
The choice to use a mastitis vaccine usually depends on the problem a farm is encountering. A review of each type of mastitis agent will give us ideas on how vaccination may fit into management choices.
Staphylococcus aureus (S. aureus) is a contagious mastitis pathogen that has poor response to treatment. As the duration of infection increases, this bacterium can avoid being killed by antibiotics and the immune system by creating tiny abscesses with walls around them. Abscess formation reduces the effectiveness of treatment and any immune response, including from a vaccine. There is a high variation in strains of S. aureus, making a universal vaccine difficult. The ability to survive inside the cells of the udder prevents the bacteria from being exposed to antibodies. It is also difficult to assess an infection or cure because S. aureus are shed in milk from an infected udder in cyclic fashion and may test negative for three to four weeks and then return as a positive. Most S. aureus vaccines stimulate an antibody response but because of its evasion abilities, an antibody response alone is insufficient to cure most infections. S. aureus vaccines can reduce clinical severity, and while they may reduce the number of clinical infections, they are not good at preventing infection. Commercially S. aureus vaccines used in heifers may reduce new infections (efficacy 44% to 66%).
Mycoplasma is an untreatable contagious mastitis. Changing surface proteins, protective coating and its ability to hide within cells all contribute to the resistance of Mycoplasma infections to antibiotics and vaccines. Commercial vaccines can cause high milk antibodies but have not been able to show decrease in the impact of mastitis.
Streptococcal mastitis can be environmental (Streptococcus uberis more so than Streptococcus dysgalactiae) or contagious (Streptococcus agalactiae, also Streptococcus dysgalactiae, and Streptococcus uberis, depending on circumstances). Within herds there can be multiple Strep strains isolated from clinical mastitis cases, which minimizes the impact of any vaccine against one strain. S. uberis may persist inside mammary epithelial cells and paralyze some white blood cell function, which makes it hard to treat and hard for a vaccine to impact. At this point there is one commercial vaccine available in select countries. This vaccine shows about 50% reduction in clinically affected animals/clinical cases, which is much better than what the Staph aureus vaccines have shown. This is a new vaccine, and the future will reveal more.
The gram-negative vaccines are the most proven and effective mastitis vaccines. Gram-negative vaccines against E. coli are some of the more successful mastitis vaccines. A high proportion of severe coliform mastitis cases become bacteremic and toxic. The vaccines neutralize the toxin associated with gram negative bacteria by producing antibodies against a core antigen in the bacterial cell wall. They are cross-protective against many gram-negative mastitis infections. The result is reduced clinical severity and reduced losses in production (yield and solids), but not a reduction in infections. There is a significant reduction in deaths from toxic coliform mastitis with this vaccine, which may be an animal welfare benefit even if low levels of the mastitis make it a marginal economic win. While the short duration of protection is a drawback, repeated vaccination can extend the protection period. These vaccines are the most proven of the mastitis vaccines and are good for use in herds facing these problems.
Prevention of mastitis should focus first on consistent application of proper milking procedures and a clean, dry environment for the cow, combined with adequate nutrition and good dry cow management. Without integration of these practices, use of a vaccine for reduction of mastitis issues will result in failure to achieve improvement.
The Genetic Connection
High mastitis rates are seldom solved with a vaccine alone. However, combination of vaccination and control procedures can promote a significant reduction in the incidence and duration of intramammary infections. When used along side genetic selection for reduced somatic cell score (SCS) and increased resistance to mastitis (Zoetis and CDCB Mastitis), dairy producers can reduce both the immediate and long-term impacts of mastitis.