Mastitis in sheep

Page last updated: Wednesday, 21 November 2018 - 7:41am

Mastitis is the term for a bacterial infection of the udder. It is most common in ewes raising multiple lambs or with high milk production. Most cases occur during the first weeks after lambing or immediately before weaning. Good ewe nutrition and providing a clean lambing environment are important factors in reducing the incidence of mastitis.

Producers play a vital role in the early detection of exotic diseases in Australia
Western Australia exports about 80% of its livestock and livestock products. These markets are underpinned by producers reporting unusual disease signs, abnormal behaviour or unexpected deaths in stock to their private veterinarian, the local DPIRD Veterinary Officer or the Emergency Animal Disease hotline on 1800 675 888, so that DPIRD can rule out any exotic or trade-sensitive diseases. Ruling out these diseases supports WA's continuing access to livestock markets worth $2 billion in 2015/16.

What is mastitis?

Mastitis occurs when a bacterial infection enters the udder through injured teats.

Which breeds are most affected?

Mastitis is most commonly associated with ewes raising multiple lambs or high milk producing breeds, including Poll Dorset and Suffolk. The disease is less common in Merino ewes rearing single lambs.

When are ewes most susceptible?

Most cases of mastitis occur during the first weeks after lambing or immediately before weaning. Cases often occur following adverse weather events or when sheep are grazed at high stocking densities.

What causes mastitis?

Two bacterial species are responsible for causing more than 80% of mastitis cases. Both are normal inhabitants of the skin and oral cavities of both the lamb and the ewe. Heavily stocked paddocks or yarding for extended periods increases the prevalence of the two bacterial species. The bacteria are resistant to a number of commonly used antibiotics so it is recommended that producers seek veterinary advice before treating affected animals.

Ewes are more susceptible to mastitis if they have some physical injury to their teats, such as:

  • those produced by shearing cuts
  • from the lamb suckling, especially when the ewe has poor milk production
  • from a viral infection such as scabby mouth.

Ewes in wet, dirty or crowded conditions are more likely to be exposed to sufficient concentrations of bacteria to initiate mastitis.

Forms of mastitis

There are two forms of mastitis: clinical and subclinical.

Subclinical mastitis may be difficult to identify. The udder may be firm and hot and lambs of affected ewes may have poor growth rates with occasional deaths in twin lambs.

In clinical mastitis, the infection rapidly progresses over several days to blackening of the udder, which feels cold to the touch due to the death of udder tissue (often called 'black mastitis'). The ewe may appear lame or continually lie down and the lambs become hollow and depressed. Lambs may die from lack of milk or from a bacterial infection from consuming infected milk. Poor weather or inadequate nutrition may trigger the progression from subclinical to clinical mastitis.

Producers should consider humane euthanasia of ewes with black mastitis that do not show an immediate response to veterinary treatment, and culling of recovered ewes after weaning as they may have permanent damage to one or more teats.

How will a veterinarian treat mastitis?

A veterinarian can help by correctly diagnosing the condition and determining the infectious agent. Seek veterinary advice on specific treatments for mastitis in sheep as antibiotic therapy will often be required. Antibiotic choice needs to be made on the basis of laboratory testing as many bacteria that cause mastitis are resistant to common antibiotics.

How can I prevent mastitis?

Good ewe nutrition and providing a clean lambing paddock are important factors in reducing the incidence of mastitis.

Maintain good hygiene if sheep are housed, and avoid prolonged periods in muddy yards and laneways during the first six weeks of lactation.

Depending on the severity of the mastitis, ewes may have permanent damage to the udder after an infection. Culling these ewes after their lambs have been weaned will help to prevent a recurring problem with mastitis in the flock.

Report mastitis signs to rule out market-sensitive diseases

Mastitis has similar signs to some diseases that have market implications or are exotic to (not present in) Australia, including scabby mouth and contagious agalactia. In outbreaks of mastitis where multiple ewes are affected, contact your nearest DPIRD veterinary officer or private vet for advice.

Scabby mouth

Some of our live sheep export markets reject animals that have scabby mouth and require animals to be vaccinated. If mastitis in ewes is caused by scabby mouth, it is likely some of the lambs will contract scabby mouth. When ready to export, inspect these lambs closely to ensure they do not have any signs of scabby mouth.

Contagious agalactia

Contagious agalactia is exotic to Australia. This status is important for some of our export markets for semen and embryos. Contagious agalactia can cause mastitis, conjunctivitis and arthritis in sheep and goats. To help maintain Australia's proof of freedom from contagious agalactia, it is important to ask a veterinarian to investigate any cases of mastitis associated with lamb or kid deaths, arthritis, or conjunctivitis.

Producers play a vital role in the early detection of exotic diseases in Australia

Western Australia exports about 80% of its livestock and livestock products. These markets are underpinned by producers reporting unusual disease signs, abnormal behaviour or unexpected deaths in stock to their private veterinarian, the local DPIRD Veterinary Officer or the Emergency Animal Disease hotline on 1800 675 888, so that DPIRD can rule out any exotic or trade-sensitive diseases. Ruling out these diseases supports WA's continuing access to livestock markets worth $2 billion in 2015/16.

DPIRD Veterinary Officer contacts

DPIRD Field Veterinary Officers can provide more information about mastitis in sheep. To find the contact details of your closest DPIRD Field Veterinary Officer, go to the Livestock Biosecurity program contacts page.