Dealing with clinical mastitis

Carole Curtis
Now Media Group


When it comes to clinical mastitis, there is a danger of taking the known information a little too casually.

'We need to think very seriously before we approach treatment in the correct fashion,' Dr. Pamela Ruegg, DVM, professor and Extension milk quality specialist in the Department of Dairy Science at the University of Wisconsin Madison, said during 'Five Keys To Maximizing Success for Clinical Mastitis.'

The presentation was the final installment of 'Healthy Udders, Optimal Milk,' a three-part World Class Webinar presented by Professional Dairy Producers of Wisconsin. It was geared toward helping dairy producers minimize udder challenges and lead to more comfortable cows.

For instance, when a third-lactation cow shows flakes in the morning milking and has a slightly swollen right front quarter, the most common reaction on Wisconsin dairy farms is to grab an intramammary tube and treat her for four to five days.

Ruegg urged dairy producers to slow it down and take a step back from the usual approach. 'The questions you should be asking are: will the antibiotics help? Do they need to be given immediately? How many treatments should this cow get and will more treatments improve the cure rate?' she asked.

Take five

Ruegg laid out five key concepts to improve mastitis treatments and minimize unnecessary antibiotic usage.

The first is to milk in the milking parlor and treat cows elsewhere. Milking technicians are simply not able to answer all the questions, Ruegg explained. Their job is to properly prepare the teats, attach the milking units and detect abnormal milk. They don't have the time or the ability to assess the situation.

'Detection of clots or flakes doesn't necessarily mean that infection is actively present in the udder,' she underlined. 'You need a little time to review that cow and make an assessment of what the appropriate treatment is.'

When cows are treated in the parlor on detection of abnormal milk, it's highly likely that a large proportion of the treatments being administered are incorrect, she said.

It's important to remember that mastitis is based on the detection of inflammation, not detection of infection, Ruegg said, explaining that inflammation is the body's response to infection and its purpose is to kill bacteria.

Most infections are identified after the cow's immune system is already actively killing bacteria. 'We can't tell if there is still active infection in the udder. Sometimes, by the time we notice the symptoms, the bacteria have already been killed by the cow's immune system and treatment is unnecessary,' she said. 'That requires a deeper look at the cow before we treat.'

Usually, milk will remain abnormal for four to six days, regardless of bacteriological cure.

'The take-home message here is don't treat simply based on the appearance of the milk,' Ruegg urged.

Surveys show few mastitis cases, usually between 5-15 percent, are really medical emergencies. Any cow with systemic symptoms including fever, being off feed, depressed and unable to rise, does require immediate treatment.

Immediate treatment isn't as critical as once thought, since the cow's immune system has already detected the mastitis and is working on it.

'It's not like nothing is going on, and that gives us a little bit of time,' Ruegg observed.

There are several options. Ideally, the milking technician should be detecting cases of mastitis and assigning a severity score. They should aseptically collect a sample of milk, discard the milk from the affected quarter and send the cow to the hospital or segregation pen for review by a trained animal health worker who works closely with the local vet to set up an appropriate treatment protocol.

When considering treatments, Ruegg said, there are at least four options.

The cow might be treated using only intramammary antibiotic, which raises the question of how many days of treatment.

The second option is to use injectable antibiotics, which Ruegg pointed out is an extra-label treatment for mastitis and should be rarely used.

A third option is 'watchful waiting and milk discard.' In these cases, antibiotics are not used initially. 'In about 40-50 percent of the cases, we can make a judgment call that the case is not active infection and the cows won't benefit from antibiotics,' she explained.

Another option, reserved for a minority of cases, is to dry off the affected quarter or dry off the cow. She might also, in the case of repeated treatments for clinical mastitis, need to be culled.

'In this case she has clearly told you she is not adapted to the environment and is much better suited to a career as a beef cow,' Ruegg observed.

Key No. 2

Ruegg's second key is to 'avoid the insanity' of doing the same thing over and over and expecting different results. On dairy farms, this form of insanity is practiced when a cow is continually coming down with mastitis, given antibiotics and sent back to her pen.

Ruegg does not recommend using antibiotics on a chronic cow unless she's sick.

'There is no evidence that repeated use of intramammary antibiotics will change outcomes of cows that have chronic mastitis,' she said.

Research clearly shows that certain cows will not benefit from antibiotic therapy. The list includes cows chronically infected with staph aureus or Mycoplasma bovis mastitis, as well as cows with multiple infected quarters, cows with damaged teats and cows with repeated previous treatment failures or a long history of chronically high somatic cell counts.

Key No. 3

Ruegg considers a diagnosis of the pathogen involved as one of the most important keys to maximizing success with mastitis.

'Get a diagnosis before giving a drug,' she advised. 'Mastitis symptoms are not specific to a particular bacteria. You can't tell by looking at the milk or the cow.'

Some cases of mastitis will benefit from antibiotics; others won't. Between 25-40 percent of cases will be culture-negative, Ruegg said, and most culture-negative cases will not require antibiotics.

Cases that will benefit from antibiotics have active bacterial infections, are caused by organisms that are susceptible to an available drug, and are not chronically distributed throughout the mammary gland.

'When possible, determine the bacteria before treatment and also to modify treatment duration.' she said.

If on-farm culturing is not an option and the case is not severe, she advised collecting a milk sample and starting a short duration treatment. Run the sample to the local vet clinic for a text response 24 hours later.

'If there's no bacterial growth, why continue the therapy? Discard the milk until normal,' Ruegg said

If the message comes back with a diagnosis, that information can be used in further treatments.

Key No. 4

In general, treat short unless there is a reason to treat long.

Bacteria that cause mastitis infect different parts of the udder. Those that invade tissues, including staph aureus, Klebsiella ssp. and some steph uberis, are more difficult to treat and have a bigger impact on the milk yield. 'These are the bacteria that benefit from longer treatments,' Ruegg said.

Bacteria that infect mucosal surfaces, including coagulated negative staff (CNS) and most E. coli, are easier to cure and there is no need for extended duration treatment. CNS, E. coli and 'no growth' amount to 70 percent of cases on a typical farm, she pointed out.

In addition, bacteria that have been subclinical for a long time are more likely to require antibiotic treatments, as compared to those with shorter subclinical phases.'That's why it's good to have individual cow somatic cell counts,' she pointed out.

Key No. 5

Read the drug labels, and know the rules.

It's important to know if the pathogen will be killed by the drug being used. For example, Pirsue@ only has the ability to bind with gram-positive bacteria. If given to an animal with E. coli, it has absolutely no ability to act on and kill that bacteria, Ruegg pointed out.

She also advised reserving the broadest spectrum drugs for cases that will benefit.

Drug labels have three key sections: dosage, indications for use and residue warnings. Any treatment that does not follow the label instructions is extra-label and must be done under supervision of a veterinarian, Ruegg said.