Types of mastitis

Understanding whether mastitis is environmental or contagious is an important first step in controlling the problem. Looking at when cases occur, which cows are affected, and herd cell count patterns can help identify the likely source. Knowing which type of mastitis you are dealing with allows control efforts to be targeted more effectively and supports better herd health and milk quality.

Ways to prevent environmental mastitis

• Milk cows as soon as possible after calving, ensuring teats are thoroughly cleaned and dried.
• Check for signs of mastitis in the udder and foremilk and identify and treat new mastitis cases early.
• Maintain udder hygiene and regularly trim tails and tail switches to help keep udders clean.
• Keep areas where cows stand and lie down clear of manure and dirt.
• Ongoing cleaning and maintenance of mud-prone areas will also make it easier to keep udders cleaner for longer.

Staphylococcus aureus

Staphylococcus aureus is a common cause of mastitis in New Zealand. Most herds will have some cows with Staph. aureus infections. With good management, these bacteria have minimal impact. But if not well managed, infections may spread from cow to cow. About this bug:

• A bacterium commonly found on skin, in nasal cavities and other sites, of cows and people.
• Can transfer from cows to people (zoonosis) and from people to cows.
• About 85% of herds have some cows with these bacteria in their udders.
• Usually makes up less than 10% of clinical mastitis cases but can be more during outbreaks.

CNS (Coagulase negative-staphlococci)

CNS are most associated with subclinical mastitis, but they can also cause clinical cases. There are over 50 species of CNS and some species are more aggressive than others. These bacteria are commonly found on the skin and coat of cows, as well as in the environment and in infected udders. They are the bacteria commonly found in heifers before calving. The impact on somatic cell count (SCC) is generally mild to moderate, unless clinical mastitis develops. CNS infections can be short-lived or become chronic, lasting for months. However, cure rates for CNS are generally better than for Staph. aureus infections, especially when treated with intramammary antibiotics at dry off. Good post-milking teat disinfection and milking hygiene are important for prevention.

Other types of mastitis bugs

You may come across some less common environmental mastitis bugs such as:

Klebsiella: Found in sawdust or organic bedding, especially on loafing or calving pads, and in muddy, wet, or marshy areas. Cows can shed Klebsiella in their faeces, so bedding contaminated with manure is a risk. It can cause sudden, severe mastitis with toxaemia, high temperature, and sometimes death. Quarters may return to production, but chronic cases are common.

Serratia: Sourced from soil and plants but can also be found in chlorhexidine-based teat disinfectants. Wet, muddy areas and pools of standing water increase risk. It can spread during milking and via damaged teat ends. Often subclinical with high somatic cell counts, but clinical mastitis can occur in over half of infected cows. Usually mild, rarely causes systemic illness, but infections tend to be chronic and intermittent.

Prototheca: An alga, not a bacterium. Found in soil, plants, streams, stagnant ponds, faeces, sheds, and yards. Can be spread cow-to-cow, especially if intramammary treatments are not done hygienically. Can cause clinical or chronic subclinical mastitis. Does not respond to antibiotics, and infection may be worsened by antibiotic use.