Feb. 25 2013 07:48 AM

Klebsiella, Prototheca and Serratia infections are replacing those we've become accustomed to dealing with. There are no known cures for this group of three.

by Amanda Smith, Hoard's Dairyman Associate Editor

Focusing on "the other bacteria," or emerging mastitis pathogens, Pam Ruegg, University of Wisconsin-Madison, addressed those gathered at the Wisconsin Dairy Field Representative Conference. "Cows are different than they were 30 years ago. They are producing more milk with a shorter unit on time. Teat ends have gotten bigger and looser – we can't get more milk in less time from the same sized hole."

Opportunistic, or environmental, pathogens have become more prevalent. Over time we have learned how to control infections caused by Staph. aureus and Strep. ag. Simultaneously, mastitis infections caused by Klebsiella, Prototheca and Serratia have been on the rise.

In a Wisconsin study with 51 farms, Klebsiella, a gram-negative bacterium, was the third most isolated mastitis pathogen. Contrary to popular belief, in only 30 percent of clinical Klebsiella cases will the cow become very ill. The majority, 80 percent, of E. coli infections last fewer than 30 days in the udder. Compare this to Klebsiella, where only half of the infections last fewer than 30 days.

Thirty percent of infections will remain subclinical for more than 100 days. During this subclinical phase, the infection penetrates deep into secretory tissue, destroys cells and milk yield plummets. While the infection persists, it can be shed and spread in a contagious fashion at milking.

To control Klebsiella, it is imperative to reduce teat-end exposure to environmental sources and improve milking hygiene. There are currently no antibiotics labeled for the treatment of Klebsiella.

Unlike Klebsiella, Prototheca is not bacteria, but water-borne algae. Overall, recovery from milk samples is low but some herds have a high percentage of cows with apparent infection. If an outbreak occurs you should look at sources of moisture, organic matter, spoiled feed or feces.

The progression, duration and treatment of a Prototheca infection are unknown. A key suspect in its proliferation is the improper use of intramammary treatments. To combat this, no unapproved drugs should be infused into the udder, teat sealants should not be warmed in water and extreme hygiene should be observed.

Serratia is also a gram-negative pathogen found in organic bedding sources that often cause long duration subclinical infections. Several outbreaks have been associated with chlorhexidine teat dips. Based on DNA fingerprinting, this is not a manufacturing problem; contamination occurs on farm – each fingerprint was farm specific.

There is no effective treatment against Serratia. Half of cows will spontaneously cure, while the other half will remain subclinically infected. Bedding management is critical to reduce the environmental sources and you may need to switch to iodine teat dips.

"Culturing is essential to identify if one of these bugs is plaguing your herd," concluded Ruegg.