NADIS disease bulletins are written specifically for farmers, to increase awareness of prevalent conditions and promote disease prevention and control, in order to benefit animal health and welfare.

Farmers are advised to discuss their individual farm circumstances with their veterinary surgeon

Toxic mastitis

The NADIS data show that cases of toxic mastitis begin to rise significantly in October, and remain high until May.

What is toxic mastitis?

Toxic mastitis occurs when mastitis bacteria invade the udder, and produce toxins. In classic toxic mastitis, these toxins come from the cell wall of the bacteria and are released as the bacteria die. In most cases the bacteria, such as E.coli and Klebsiella, that cause toxic mastitis come from the environment of the cow. This is the reason why levels increase in the early autumn as more cows are housed.

The toxins are absorbed from the udder and cause a whole range of effects in the body including medical shock and clotting of blood in the blood vessels, in addition to damaging organs such as the kidney and the liver as well as the udder.

A study carried out in Northern Ireland showed that around 14% of cows with toxic mastitis die while a further 43% are either culled prematurely or lose a quarter.

Toxic mastitis is not just a dairy problem. The Northern Ireland survey found that 1 in 7 cases occurred in suckler cows.

Clinical signs

· Depression and loss of appetite

· Rapid drop in milk yield with discoloured milk (usually straw coloured)

· Scour (in around 20% of cases)

· Staggering and collapse

Treatment

Veterinary treatment is essential for these sick cattle. Early treatment has much better success rate than delayed treatment. A cow that is still standing when the vet starts treatment is 12 times more likely to survive than a cow that has collapsed.

Veterinary treatment usually consists of one or more of intravenous fluids, antibiotics and anti-inflammatories. Of the three, fluids are the most important, particularly in collapsed cows.

Stripping the quarter to remove as much of the abnormal milk as possible is also extremely important. Stripping helps to remove the bacterial toxins from the udder, preventing their absorption into the body. Hourly stripping with udder massage can significantly improve survival.

Prevention

Almost two thirds of cases of toxic mastitis occur in the first month after calving, with almost half of those cases in the first four days after calving. Thus managing the environment of the late dry cow and freshly calved cow is extremely important in preventing toxic mastitis. The environment of the dry cow and freshly calved cow must be kept as clean and dry as possible. Overstocked straw yards, short uncomfortable cubicles and wet bedding all increase the risk of toxic mastitis

Dry cow therapy still remains an important part of any toxic mastitis control regime. However it is important to ensure that cows are dried off hygienically, as dirty antibiotic tubes can introduce infection into the udder and thus lead to the toxic mastitis that they’re designed to prevent. This is particularly important with the introduction of internal teat sealants, as, because they contain no antibiotic, the risk of sealing-in infection is much higher with these products if they’re not used properly.

Other control measures include giving time for the teat canal to close after milking before cows are returned to housing, preventing milk fever and other calving diseases and reducing lameness (as lame cows lie down more and increase the risk of bacteria entering the udder.

A vaccine is now available which can significantly reduce the severity of toxic mastitis. Because toxic mastitis is such an expensive disease it is worth considering even if you only get one or two severe cases every year. Ask your vet for advice as to whether vaccination would be of benefit on your farm. Like all vaccines, it works best if you use it in combination with other prevention strategies

Richard Laven PhD BVetMed MRCVS