is enough available evidence to provide practical control measures. Control, biosecurity and prevention are the key elements of it from a mastitis point of view. His first recommendation is to stop infected cows from enter- ing the herd. Since new stock does not come with a bill of health, the onus is very much on the buyer, said Dr Mason. While it is possible to buy disease-free cattle for some infec- tious diseases, such as BVD and IBR, information on M. bovis is not available at the point of sale just yet. This means that it is risky to introduce new livestock to the herd. “It’s impossible for you to know for sure if you’re buying cattle that are free from Mycoplasma bovis,” said Dr Mason. Currently, researchers don’t even know how many herds are infected in the UK at the moment. “We suspect it’s quite a high number,” Dr Mason added. “But we actually don’t know what the number is.” One way to reduce risk is to screen cows before they enter the herd. The easiest way to screen cows for mastitis-causing M. bovis is to screen their milk upon arrival, said Dr Mason. To further minimise risk, he suggests milking them last, at least until results come back negative. Providing separate space to reduce the risk of spread is an- other good method of control, although this could prove challenging for some farmers. Finally, if it is suspected that M. bovis is the cause of mastitis on the farm, it is important to think about possible pathways for the disease’s spread. The first might seem obvious, but it’s sometimes overlooked. “With the exception of colostrum, don’t feed your milk to calves,” he said. “Because all you’re doing is then setting up a new round of infection.” If M. bovis is already present in the herd, the following con- trols can be used to prevent the spread of disease. Since the disease can be spread via direct contact, milking hygiene is of the utmost importance. Dr Mason promotes the use of sin- gle-use towels, gloves and post-milking teat disinfection. In a 2002 study, five different teat dip classes were tested for efficacy against three bovine M. bovis species. It was shown that M. bovis was susceptible to commercial test disinfect- ants that contained 1% hydrogen peroxide, 1% chlorine di- oxide, and 0.5%-1% Iodofor solutions. Dr Mason notes, though, that these tests were conducted in experimental models only and may not translate well in field conditions in all cases. Regardless, teat disinfection is proven to be an excellent method for controlling the spread of disease. Milking plant wash cycles should also be reviewed and improved where necessary. While there are some reports of animals self-curing, it’s not common. Generally speaking, M. bovis-caused mastitis is not readily treatable. “Ultimately, these animals need to be considered on their mer- its, but a lot of them will end up being culled,” said Dr Mason. Although culling is a recognised strategy to control disease


spread, herd-wide culling is not necessary. New Zealand has presented an intriguing case for mass culling only because the pathogen is so new to the island that eradication and therefore a return to zero status, experts believe, is possible. “They’re in a situation still where the disease is not endemic,” he said. “It’s a low-prevalence situation, and they’ve got a chance of kicking it out.” But a lot of countries are not in that situation, so that cannot be compared. Eradication in the UK, for example, wouldn’t be possible without wiping out a proportion of the national herd. Going forward, knowing herd status could play an important role in curbing the spread of M. bovis. Negative status herds, said Dr Mason, could be used for replacements. Better quality vaccines could play an important role going forward as well.


▶DAIRY GLOBAL | Volume 7, No. 1, 2020


Hygiene is of utmost impor- tance, the use of gloves and post-milking teat disinfection is recommended.


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PHOTO: MARK PASVEER


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