Conditions ideal for lameness in sheep

Neale WhitsedSMALL FARMS NETWORK - SPRING 2021 - ANIMAL HEALTH & DISEASES

By Neale Whitsed
Senior Biosecurity Officer

P: 02 6051 2205 | M: 0427 362 733 | E: neale.whitsed@lls.nsw.gov.au

Neale Whitsed checking sheep's feet for footrotSpring is the time to look for lameness in your sheep.

There are various causes of lameness in sheep, including ovine interdigital dermatitis, benign footrot, virulent footrot, and foot abscess. Lameness in sheep leads to reduced weight gain and skinny sheep. This can also impact pregnancy rates and if ewes are affected close to lambing, it can cause fatal pregnancy toxaemia ‘preg tox’ also called ‘twin lambs disease’.

Ovine interdigital dermatitis (OID) - also known as ‘scald’ - is a mild infection of the skin between the hooves of sheep. It is usually associated with lush, green, wet paddocks; when a sheep’s feet are constantly exposed to moisture, they become susceptible to bacterial infection. OID can then create a window for other more severe infection, such as footrot and foot abscess. Many sheep producers in the region undertake footbathing programs during winter using zinc sulphate, which acts as a topical disinfectant and has a drying effect on the feet. This practice can help to control OID and prevent more severe foot problems.

Footrot is an infection caused by the bacterium Dichelobacter nodosus, which breaks down the tissue between the horn and the foot and can result in painful separation or ‘underrun’ of the sole. Around 20 different strains of Dichelobacter nodosus have been identified in Australia, and each strain has differing ‘virulence’ or ability to cause disease.  Virulent footrot is the name given to the severe strains, based on how many sheep are affected and how badly. Benign strains cause less of an issue in the flock. All strains of footrot are unable to infect a healthy foot. OID causes the damage to the foot to allow footrot to infect the foot. Good control of OID can reduce the effects of benign footrot in a flock.

Virulent footrot is notifiable in NSW. If you think you have virulent footrot in your flock, you need to notify Local Land Services within 48 hours. LLS vets and biosecurity staff will then make a thorough assessment on the cause of lameness and can advise you on how best to manage the lameness and reduce impacts.

Other states have different levels of regulation in relation to footrot. As such, it is a requirement to have a Sheep Health Declaration stating that sheep are free of virulent footrot when sheep enter NSW from interstate.

On-farm biosecurity is the best defence against introducing diseases and treatment-resistant parasites. This includes assessing the risk prior to purchase and isolating or quarantining newly acquired stock from the existing flock. Boundary fences should also be well maintained to reduce the risk of disease spread by stray sheep.

Footrot needs the right conditions - warm and wet - to cause disease. This could mean you may need to isolate newly introduced sheep for extended periods to monitor them for lameness during the winter/spring risk period.

Current conditions are conducive to lameness issues in sheep. Regular monitoring is important, especially in newly acquired sheep. If you have any issues or concerns, please call your local District Vet or Biosecurity Officer to discuss.

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