Novel Mastitis Solutions -
Researchers Developing Vaccinations and Other Defences to Enhance Udder Health

Table of Contents

• Mastitis Control in a Nutshell
• Fighting Infection
• S. aureus Vaccination
• Reducing Mammary Damage

Vaccination against Staphylococcus aureus-the bacterium that causes arguably the most difficult type of mastitis to deal with-has been investigated in the past, with disappointing results. That could change, however, if a Canadian research team, led by Dr. Pierre Lacasse of Agriculture and Agri-Food Canada, proves successful.

Any mastitis can prove costly when you tally up treatment costs, revenue losses from reduced milk production, discarded milk and the loss of animals culled because of recurrent infection. Infections due to infection with S. aureus can be the worst. It responds poorly to conventional treatment and this bacterium is at risk of spreading on most farms. Preventing the spread of infection requires careful attention to postmilking teat dipping and other hygienic milking practices.

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Mastitis Control in a Nutshell

• Have a program to monitor udder health status
• Milk only clean, dry teats.
• Use separate paper towels for prepping each cow.
• Dip the teats of all cows post-milking with a licensed teat dip.
• Milk infected cows last or with a separate unit.
• Dry treat all cows.
• Maintain equipment to reduce liner slips and keep teat ends healthy.
• Keep bedding clean and dry in lactating and dry cow environments.
• Calve cows in a clean, dry box stall or on pasture.
• Keep yards, pastures and laneways dry.
• Balance lactating and dry cow rations to meet NRC recommendations.
• Purchase uninfected cows or heifers.
• Prevent teat injuries.
  

Reduce or eliminate environmental stress.

For more information on these and other prevention strategies, visit The National Mastitis Council (www.nmconline.org) and see the OMAFRA Factsheet, Mastitis Prevention: Environmental Control (www.omafra.gov.on.ca/english/livestock/dairy/facts/90-104.htm).

The researchers are investigating novel ways to fight S. aureus infection as well as reduce mammary gland damage from endotoxins released by bacteria such as E. coli when udder infections occur. Let's take a look at what Lacasse's team has been doing:

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Fighting Infection

Lactoferrin, a protein synthesized in the cow's mammary gland, is present in variable concentrations in milk. When animals metabolize this protein, it's converted to lactoferricin. Both lactoferrin and lactoferricin have antibiotic properties, although lactoferricin has been identified as being the more potent molecule.

Researchers have investigated both molecules coupled with antibiotics such as penicillin, ampicillin, novobiocin, erythromycin and neomycin as mastitis treatments. Small experimental studies have shown that an antibiotic's effectiveness is substantially greater when used in combination with lactoferricin or lactoferrin.

When a strain of penicillin-resistant S. aureus was exposed to various treatments-including penicillin alone, lactoferricin or a combination of lactoferricin and penicillin-the latter treatment was able to stop the bacteria from proliferating.

These findings suggest that micro organisms seemingly resistant to penicillin may become susceptible when lactoferricin is part of the treatment. Furthermore, the research could open the way to new therapeutic strategies that might cure bacterial infections caused by other antibiotic-resistant micro-organisms. Work is underway to bring these findings one step closer to a solution.

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S. aureus Vaccination

Traditional methods for creating vaccines to prevent S. aureus udder infections have failed in the past. A new method using DNA techniques looks more promising.

DNA is the building block of the genetic material contained in every cell of the body. A gene controls the transmission of a hereditary trait by specifying the structure of a particular protein.

The researchers are studying a new concept identifying one or more genes specific to the bacteria they want to control. These genes are inserted into the cow. The cow's immune system can then create anti bodies to fight invading bacteria such as S. aureus. Essentially, the cow can now make her own vaccine.

This theoretical approach was tested in mice. A specific gene derived from s. aureus was introduced into the mice. Their immune systems produced a substantial response and destroyed the cells infected by the bacteria. Following these encouraging findings, the next step was testing the technique on cows. Eight heifers of the same age were used in this trial. A DNA vaccine with two genes was injected into four of the heifers precalving. The remaining four formed the unchanged control group. The response in the treated heifers was promlsing.

The bigger question, then, was to know if this response would have an effect when infection with S. aureus occurred in these heifers. Three weeks after calving, three out of four quarters of each heifer were inoculated with S. aureus bacteria. All inoculated quarters in all the heifers developed mastitis.

However, three weeks after the planned infection, the number of infected quarters had decreased gradually in the vaccinated group. The number infected in the control group remained the same.

This suggests that the treated heifers were able to clear the infection. Although these results look promising, a lot more research and testing needs to be done to find new genes that can be used to create a multiple antigen vaccine and optimize the vaccine's usefulness. After all this experimental work, a lot more research using a lot more cows in a variety of different herds will have to be done to prove that this vaccination method will work under field conditions.

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Reducing Mammary Damage

When mastitis occurs, the cow's defense mechanism often harms the cells lining the inside of the udder. White blood cells that fight infections, called neutrophils, migrate out of the bloodstream and move to the site where infection has occurred. Their role is to kill bacteria.

Neutrophils use two mechanisms to do this killing. Massive production and release of destructive free radicals is the first. The second is releasing a variety of other destructive enzymes. The free radicals are toxic molecules that kill bacteria but also damage surrounding mammary gland cells. To reduce the loss of milk-producing tissue and mammary cells, researchers have sought methods to minimize the damage.

A research project evaluated a wide range of substances for their ability to protect the mammary gland epithelial cells in the laboratory. One stood out as being promising. Further testing showed this substance reduced the number of bacteria in the milk and the amount of cell damage in cows with E. coli mastitis. Researchers call it Substance X and have filed an application to patent it.

Although a lot of work still needs to be done, the researchers have identified encouraging avenues. These studies reflect the long-term investment needed to change the way we deal with mastitis.

While the industry has great expectations of breakthroughs in this field, the key components of a good mastitis control program for now are still teat dipping, good milking hygiene and milking routine, clean and dry housing with fresh bedding, and dry cow treatment.

This article first appeared in the Ruminations column of The Milk Producer Magazine, October, 2005

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