Environmental Streptococci and Enterococcus spp.: A Practical Summary for Controlling Mastitis

The implementation of control measures for contagious mastitis pathogens has successfully reduced the prevalence of these organisms in U.S. dairy herds. However, controlling environmental pathogens remains a daunting task. Environmental streptococci and Enterococcus spp. are bacteria with similar biochemical and structural characteristics. These bacteria are Gram-positive, with a cell wall structure similar to Staphylococcus spp., as well as streptococci such as S. agalactiae and S. uberis. Not all milk culture laboratories across the United States distinguish between environmental streptococci and Enterococcus spp. However, this document will address the inherent differences between these pathogens as well as the similarities.

Where are these organisms found?

These are environmental organisms commonly found in organic matter, including bedding. Enterococci are also commonly found in silage inoculants and are associated with plant matter, such as dairy feed. Because streptococci bacteria are common in dairy cattle manure, they are often found in the bedding. Poor udder cleanliness, inadequate stall management, and damaged teat ends also appear to increase the risk of spreading Enterococcus spp. and environmental streptococci to uninfected cows.

How do environmental streptococci and Enterococcus spp. spread to the mammary gland?

Environmental streptococci and Enterococcus spp. will spread to uninfected cows through environmental contact. As with all environmental organisms, maintaining a clean and dry environment for cows to lie in is of utmost importance. In particular, the use of inorganic bedding (sand) will reduce the environmental contamination with these bacteria. However, it is important to remember that recycled sand can still serve as a source of environmental contamination because the organic matter builds on the bedding material. 

How can you prevent and control mastitis caused by environmental streptococci and Enterococcus spp.?

The control of environmental streptococci and Enterococcus spp. includes maintenance of a clean and dry housing environment and implementation of proper milking procedures. At milking time, all quarters should be forestripped, which will begin the milk let-down process. Following forestripping, the use of an FDA-approved and efficacious pre-milking teat disinfectant is particularly important for this mastitis-causing pathogen. The pre-milking teat disinfectant should remain on the teats for 30 seconds prior to removal with either a paper towel or a single-use clean and dry cloth towel. Following these guidelines, the time from start of manual stimulation (forestrip or wipe) to unit attachment should be in the range of 60 to 120 seconds. This will allow the appropriate time for milk let down. 

Following unit detachment, the application of an FDA-approved and efficacious post-milking teat disinfectant should be applied with coverage over at least two-thirds of the teat barrel. In herds with a particular environmental mastitis problem, the use of a barrier teat dip is recommended. 

In addition, reducing teat end exposure between milkings by scraping the back of cow stalls (where the udder rests) and applying fresh bedding frequently is imperative. The application of bedding conditioners such as hydrated lime is effective at reducing the bacterial load in the bedding. However, the activityapplication is required. It is recommended that 2 pounds be applied per stall, and it must be applied every other day.

The use of blanket dry cow therapy with a long-lasting antibiotic preparation is an effective way to cure existing infections at drying off. Furthermore, studies report the use of an internal teat sealant will significantly reduce the new intramammary infection (acquired during the dry period) caused by environmental streptococci. Using an internal teat sealant in conjunction with blanket dry cow therapy will double the cost of dry cow treatment. However, in herds where environmental streptococci are the predominant bacteria isolated from clinical mastitis, this is an effective way to prevent new infections and cure existing infections during the dry period. As a reminder, it is recommended to consult with your veterinarian before beginning any antibiotic treatment protocol.

When are environmental streptococci and Enterococcus spp. infections most likely to occur?

New infections can occur at any time during lactation and can also occur during the dry period. However, cows in early lactation are at an increased risk for new infections due to the increased stress and immune suppression associated with the postpartum period. Additionally, cows are also at an increased risk for mastitis immediately after drying off. Following milk cessation, cows do not experience the daily flushing of the gland and are at an increased risk for mastitis in the early dry period. Cows with high milk production are not at greater risk than cows with low milk production.

How likely are environmental streptococci and Enterococcus spp. infections to cure?

These infections are often difficult to cure with traditional intramammary antibiotic preparations. Some veterinarians have had greater success with systemic administration of penicillin. However, veterinary consultation is recommended prior to the start of any treatment protocol. Due to the nature of these bacteria, emphasis needs to be placed on prevention of these infections, rather than focused on treatment.

Quick Notes

• Environmental streptococci and Enterococcus spp. are environmental organisms found commonly in manure and bedding.
  
• It is imperative to keep bedding clean and dry.
• The use of washed sand bedding that is properly dried will help reduce the environmental load of environmental streptococci and Enterococcus spp.
• Proper milking procedures, including predip and postdip applications, are extremely important in the prevention of these infections.