Novel Mastitis Solutions -
Researchers Developing Vaccinations and Other Defences to Enhance Udder
Health
Table of Contents
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.
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:
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.
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.
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
