Remember E. coli mastitis bacteria? It’s time to take a closer look to determine if it’s causing losses in your operation and how to deal with this vile environmental pathogen.
E. coli bacteria are gram-negative mastitis pathogens with a cell structure that is fundamentally different than gram-positive bacteria. The cell wall of E. coli is the main toxin that the bacteria contain. It’s called endotoxin or lipopolysaccharide and is a highly potent stimulator of the cow’s inflammatory system. As E. coli bacteria grow and then die, they release their toxin, which can cause more severe systemic disease signs. However, especially when herds use a core antigen vaccine, most cases of E. coli intramammary infections will be mild to moderate.
When a dairy does bacterial cultures on-farm or through a laboratory, the priority is to determine first if the infection is gram-positive or gram-negative, as this is an indicator of treatment considerations. It also helps identify the infection reservoir, where the infection is coming from on the farm.
“For gram-negatives like E. coli, the infection opportunity comes from the cow’s environment. When considering prevention, it comes down to keeping cows as clean and dry as possible,” said John Wenz, associate professor at Washington State University. “When you compare the environmental pathogens E. coli and the environmental streps, they’re different due to their infection reservoir compared to classic contagious pathogens like Staph aureus and Strep agalactiae, which we were constantly battling, but are now under control.”
With contagious pathogens, the industry has a 10-point plan from the National Mastitis Council, explaining how to tackle them, which involves stopping the spread of milk from cow to cow in the parlor and using dry cow treatment. However, with environmental pathogens like E. coli, it’s all about keeping the cows as clean and dry as possible. But that’s not as clearly defined as the 10-point plan. So, the question becomes, “How clean and dry is clean and dry enough? And how do you know it when you see it?”
“You might look at some stalls in a free stall barn, and they look okay to you. Yet, you still have too many environmental mastitis infections in the herd,” he said. “In one study with a small data set, we looked at hygiene scoring of stalls by comparing two pens using recycled manure solids as bedding and found that if you kept the percent soiled stalls below 40%, that was the back one-third of the stall, there is no relationship with the somatic cell count of the pen.”
Thus, keeping soiled stalls below 40% was clean and dry enough, but going above 40% showed a positive relationship with intramammary infection, at least on that farm. Keep in mind, there is a lot of variation in bedding types, management and stall design which can impact what it takes to keep stalls clean and dry enough for each dairy, said Wenz.
E. coli signs:
- substantial drop in milk production
- fever
- dehydration
- severe depression
- lower feed intake
“The majority of E. coli cases do not result in severe disease; but if you have a cow that has severe signs, you’re going to bet on it being an E. coli infection,” he noted.
Preventing E. coli
The challenge for dairies is to determine what’s clean and dry enough on their farms. This can be challenging due to the availability of people, tractors and equipment needed to manage pens. Often, bedding management is done on a schedule, for example, once a week or every other week. If you’re having a problem, it may be time to rethink your schedule and let the stalls tell you when it’s time to replace or add new bedding by doing routine stall or bedding hygiene scoring.
“Use of a core antigen vaccine doesn’t prevent infections, but it does reduce the severity of those that occur and become clinical. Thus, a dairy will have fewer severe cows,” Wenz explained. “On most commercial dairies, producers could easily calculate a cost-benefit of using a core antigen vaccine. If you had more clinical mastitis associated with gram-negatives than you want on the farm, it’s certainly worth considering.”
Wenz reminds that gram-negative bacteria are an environmental problem; it’s in the environment of the cows.
“E. coli live where cows spend most of their time, lying down in a comfortable stall. Don’t go to the milking parlor to solve this problem; go to the stall,” he said.
Headline image of dirty cow with E. coli courtesy of Dr. John Wenz
