Mastitis is an infuriating disease that more often than not occurs with no warning signs. It can strike in the immediate period pre- and post-lambing and frequently presents as an issue in the first six weeks of lactation but can also hit right up to, and after weaning.
While ewes with damaged teats or udders pose the greatest risk, it can also arise in first-crop sheep that are lambed a few weeks and making a good job of their progeny. As can be imagined, this is often the greatest source of irritation as along with the risk of mortality in productive ewes, it regularly presents challenges in trying to switch lambs over to artificial rearing.
Causative factors
The Journal Vet lists bacteria gaining entry to the mammary gland as the number one cause of mastitis but notes that the disease can also be caused by physical injury. The bacteria that cause the disease include streptococcus and staphylococcus species along with pasteurella species and coliforms such as E coli, which raises the importance of a robust health programme and implementing high standards of hygiene at lambing.
Hygiene in lambing pens is vital to prevent the entry of bacteria into the mammary gland.
The fact that many of these causative factors can be so readily present around lambing heightens the importance of doing your best to take risk factors out of the equation. Aspects such as too little milk production, stemming either from inadequate nutrition or a ewe not being capable of producing sufficient milk for two, or in particular three lambs, is also a major risk factor.
This is due to lambs sucking frequently and increasing the risk of a ewe’s teats being damaged or her udder becoming sore and creating an opportunity for bacteria to enter the mammary gland. As such, orf is also a significant risk factor if contracted on the teats or udder. Some ewes with a greater milk yield potential also have a higher risk of bacteria entering the mammary gland, a risk similar to high versus lower yielding cows.
Once established, bacteria can be spread from hungry lambs trying to suck other ewes or from farmers handling ewes with mastitis or a contaminated environment and not taking the appropriate hygiene measures. Where farmers are facing challenges in getting young ewes with lambs out to grass, the use of sufficient straw bedding and disinfection of lambing pens cannot be stressed enough.
Telltale signs
There are three main types of mastitis infections – peracute or gangrenous, acute mastitis and chronic mastitis, with subclinical mastitis another type that is less clear to identify. The clinical signs of each are listed as follows.
Peracute or gangrenous mastitis
As the name suggests, gangrenous mastitis is a nasty ailment. It is characterised by a swollen mammary gland that is warm when the disease is in its infancy. When drawn, milk from the gland may be a deep yellow or blood-stained and is usually accompanied by a foul smell. The gland quickly progresses from warm to a blue-black discolouration, with heat quickly leaving the gland. The gland frequently rots away or can burst and fall off. Bacteria associated with this type of mastitis is mainly Staphylococcus aureus, although Pasteurella multocida, Pasteurella (mannheimia) haemolytica and E coli have also been reported.
Acute mastitis
This type of mastitis is best characterised by the gland becoming swollen, reddened and very painful. When drawn, the milk can be quite normal or abnormal looking and the gland is usually quite warm.
The high level of pain leads to a characteristic sign of ewes not being inclined to walk or walking very slowly, often dragging her leg due to the soreness of the leg brushing against a swollen mammary gland.
Like gangrenous mastitis, affected ewes are lethargic, showing depression and quickly progress to anorexia, dehydration and an inability to stand, with fever also present. The organisms listed under peracute mastitis above are also associated with acute mastitis. For both acute and peracute, prompt treatment is required to prevent losses.
Chronic mastitis
As the name suggests, chronic mastitis is generally a longer-lasting ailment that sometimes goes unnoticed. It is generally caused by a previous case that has not progressed to as serious a stage as described above but is still present. It is identifiable by the udder developing an internal lump which is caused by a fibrous nodule or abscess. The udder may become smaller but it often not identified until checking ewes at shearing or post-weaning.
The pathogens most commonly associated with chronic mastitis include Staphylococcus aureus and Arcanobacterium pyogenes.
Subclinical mastitis
Like chronic mastitis, this is hard to identify. The mammary glands will be warm and firm but often the only signs are lambs being hungry or performing poorly. Subclinical mastitis can progress to a more serious type listed above. The progression is often linked to inadequate nutrition or poor weather putting additional strain on the animal and overcoming its immune system.
Route of treatment
Antibiotics are the primary treatment. Care should also be taken to manage the ewe in a comfortable manner. This may include housing in an isolated area if weather is harsh or removing to a small paddock. Depending on the severity, lambs may need to be temporarily or permanently removed for artificial feeding. Administering electrolytes may be recommended if the ewe is dehydrated. Cases are usually sporadic in flocks but if an outbreak occurs it is important to get to the root of the cause so that the best course of action can be taken. This includes collecting milk samples carefully and relaying via your vet to the local regional veterinary laboratory. Veterinary advice is important and this may include administration of anti-inflammatory drugs to provide pain relief. A course of antibiotics that usually last a week should be adhered to.
Longer-term, it is important to check udders at weaning and before breeding.
Adequate nutrition will help to eliminate some of the risk factors associated with mastitis.
Watch: ewe gives birth to six healthy lambs in Teagasc Athenry