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Understanding the risk of virulent footrot

Virulent footrot has been detected sporadically in flocks across the South East area including the Monaro. Although we have a number of flocks infected in the South East area they only represent a small percentage of the nearly three thousand flocks in the region, and all owners of infected flocks are working towards eradication.

Why are we seeing virulent footrot again?

Footrot requires the right combination of warmth, moisture and pasture growth to develop. Seasonal conditions in both the autumn and spring of 2014 were very suitable for full expression of both benign and virulent footrot disease. Feet also remained wet during the milder winter of 2014 further adding to expression. Footrot ranges along a spectrum, in the severity of disease and lameness it causes, from benign through to severely virulent. This variation is in the speed in which it causes underrunning, the extent of this underrunning, and the percentage of the flock affected. 

All forms of virulent footrot will cause underrunning of the horn of the heel and lameness in the affected foot in warm and wet conditions. The less virulent forms need better expression conditions to show their full potential. So to some extent these less virulent forms of footrot were lying latent during the drier times and are becoming more obvious now that conditions are more suitable for expression. What we are seeing at present is a final mopping up of flocks infected with less virulent strains, now that conditions are more suitable for expression. These virulent strains still cause pain, economic loss and are a huge disruption to farm management and eradication is the best option. Some footrot outbreaks have also been caused by purchases of sheep from interstate where there have not been footrot eradication programs.

What is occurring to keep the outbreaks under control and restricting the spread?

Footrot policy and procedures have been in place in NSW since the late 80s which have resulted in a dramatic decline in virulent footrot across the state and the amount of disease detected. Producers in NSW should feel suitably protected by the current policies and regulations and the support of the Local Land Services Veterinarians and Biosecurity officers. As a notifiable disease producers are obliged to notify the Local Land Services if they are concerned about lameness in their sheep. As a quarantined disease infected properties must keep straying stock at home, engage in a program to eradicate the disease and may only sell direct to slaughter. All neighbours of infected properties are notified and checked for disease and sheep sales are both traced forward and backwards. There is also ongoing surveillance across the state in the form of inspections of sheep at the saleyards and investigations of reports of lame stock.

What is the recommended procedure if lame sheep are seen?

If a producer is aware that they have lame sheep and footrot is a possibility they must notify the Local Land Services Veterinarian for advice. An assessment of the flock and situation can then be made. If virulent footrot is diagnosed eradication by either complete or partial destocking is recommended, followed by repeat inspections during both a non spread period and a spread period to ensure the disease is eradicated. Footrot should be controlled during spread periods as much as possible to minimise the impact of the disease. Your LLS veterinarian will help you develop a footrot eradication plan for your property.

How does virulent footrot impact on sheep producers?

The diagnosis always causes concern as finding the disease drops a physical, emotional and financial burden on landholders. Eradicating footrot from an infected property involves a lot of planning and difficult decision making, hard physical work and financial input. However living with the disease costs producers far more. Footrot causes pain and lameness in affected sheep and goats and has an enormous impact on flock productivity and profitability by reducing wool production, causing poor growth rates, lowering ewe fertility and restricting the sale options of infected sheep.

How can producers keep footrot out?

All producers purchasing sheep should be aware of and wary of footrot. It is unwise and untrue to think that footrot has been completely eradicated in NSW, it continues to be a real biosecurity risk. Producers need to maintain their farm biosecurity to keep footrot out. This involves maintaining and checking external fences and vigilance on stray sheep. It also involves great care when purchasing sheep, a sheep health statement should be requested and if sheep cannot be inspected before purchase they should be inspected as soon as they get off the truck. A minimum of 30 sheep should be inspected, with particular focus on anything that is lame. It is also best practice to keep these sheep separate from your own until after a spread period. This management decision has kept a number of local flocks protected from the devastating effects of disease introduction. 

Alex Stephens
District Veterinarian 
02 6118 7700