June 2014
Contact: Your local PIRSA office, local private veterinary practitioner or phone
Biosecurity - SA Animal Health at Glenside on 8207 7900.
Footrot in Sheep
Footrot is a contagious disease of sheep caused by the bacterium, Dichelobacter nodosus (D. nodosus).
Other bacteria are often present in an outbreak.
Virulent footrot is a most serious disease. It generally causes severe lameness resulting in significant
economic loss from reduced wool growth, poor ewe fertility, reduced growth rates and lower prices for
sale sheep.
Footrot
The Cause
For the development of footrot in sheep it is essential that both the correct infective factor and
environmental factors are present.
Infective Factor
The infective factor is the presence of D. nodosus. However for infection to occur there must be
dermatitis present between the claws (interdigital dermatitis). The bacteria will not invade healthy feet
and will not survive more than 5 to 7 days in the environment under ideal conditions. The organism can
persist for many years in the feet of infected sheep, even under dry conditions. Footrot is generally
introduced into a flock via introduced infected sheep. However, in some cases a clean flock can be
infected by walking on pasture where infected sheep have recently grazed.
Environmental Factors
The three main environmental factors required for the establishment and transmission of footrot are:

An average temperature of 10 degrees C or higher for 4 – 5 days; and

Adequate moisture; and

Adequate pasture length and density to make feet susceptible to infection.
Footrot is a problem in areas with greater than 500 mm/year of average annual rainfall. In South
Australia, high risk environmental areas include the South East, Fleurieu Peninsula, Adelaide Hills,
Kangaroo Island, parts of the mid-North and the lower part of the Eyre Peninsula.
In most years suitable conditions exist from September to November for the spread of the disease. In
some years, where there has been an early autumn break, suitable conditions for expression and
spread can exist in April and May.
Symptoms
Footrot is classified as either virulent or benign.
A clinical diagnosis is based on the Edgerton Foot Scoring System whereby a clean (non-infected) foot
has a Foot Score of 0 and a severely affected foot has a Foot Score of 5. Examples of each score are
shown on page three.
For regulatory purposes in South Australia, virulent footrot is defined as a flock having greater than 1%
of Score 4 and 5 foot lesions. However, where significant levels of Score 3 lesions are present, virulent
footrot may be a possibility.
Resolution of such suspect cases may depend on laboratory virulence testing.
Benign Footrot
Benign footrot generally causes minimal economic losses. However in some situations it can predispose
animals to grass seed penetration which can cause severe lameness.
The interdigital skin between the claws becomes moist and inflamed. This is known as interdigital
dermatitis. A high percentage of the flock may be affected under favourable conditions and more than
one foot is generally affected.
When affected sheep are grazed on dry pastures under dry weather conditions, the disease can
spontaneously disappear without any treatment.
Early stages of virulent footrot will have identical symptoms to benign footrot.
Virulent Footrot
Virulent footrot starts with interdigital dermatitis and loss of hair between the claws. The disease then
progresses to the sole of the foot and separation of the horn of the hoof from the underlying tissues.
In some sheep, the disease develops rapidly in warm moist conditions to the whole of the sole (Score 4)
and can extend up the wall (Score 5).
Usually both claws are affected and often in more than one foot.
Severe lameness is frequently a feature of virulent footrot.
When footrot is caused by a milder strain, there are fewer sheep affected and these may be infected in
only one or two feet.
In dry conditions, or following footrot treatments, all of the above typical signs can be supressed.
Detection of virulent footrot in these circumstances can be very difficult.
Chronically affected hooves may become blackened, distorted and overgrown before the shell peels off
completely. Flystrike is common at this stage, especially during summer. Severely affected sheep
become very lame and may suffer extensive skin damage to the knees and brisket due to grazing on
their knees. If the disease progresses to this stage, it can have severe animal welfare implications.
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Distinguishing Between Footrot and Foot Abscess
In a field situation it is very important to distinguish between footrot and foot abscess. Foot abscess is
caused by the bacteria Fusobacterium necrophorum and Actinomyces pyogenes. Both footrot and foot
abscess can cause severe lameness. Table 1 shows some identifying characteristics of footrot, heel
abscess and toe abscess.
Table 1
Clinical characteristics of footrot, heel abscess and toe abscess
Footrot
Heel Abscess
Toe Abscess
Usually affects more than one foot.
Usually affects one hind foot which is
Usually affects front feet.
carried.
Usually affects both claws
Generally one claw affected
Generally one claw affected
No swelling.
Swelling – usually spreading to the toes.
Swelling is not a feature.
No pus discharge, but a black-grey slime
Creamy-white pus discharge.
May be pus/fluid from point of the toe when
like substance may be present.
Heat may be present in some cases
pared/trimmed
Hot to touch, particularly at the site of the
May be hot to touch.
swelling.
Lesions have a putrid odour and may be
Lesions can have a slight odour, but are
Odour distinct from footrot. Lesions may be
flyblown.
rarely flyblown.
flyblown.
Spreads rapidly to sheep of all ages,
Usually confined to heavy sheep such as
Affects all classes of sheep.
including lambs, when conditions are
rams and pregnant ewes.
favourable.
No break in the coronet skin, but separation
Abscess usually breaks out at the coronet or
Abscess usually occurs under the horn at
of the inner sensitive horn and outer hard
in the interdigital skin. Resolving abscess-
the front of the toe. May open in a line
horn.
defined area granulated.
above the coronary band. Can cause
separation of the front half of the sole in
chronic cases.
Regulation of Footrot
Virulent footrot is a notifiable disease in South Australia. Once virulent footrot has been diagnosed in a
flock, quarantine Order issued under the Livestock Act 1997. This Order, once imposed, prohibits the
sale of sheep to other graziers, allowing sheep to stray and the selling of sheep from the quarantined
flock in a public market. Animals may be sent direct to an abattoir for slaughter. The aim of these
restrictions is to prevent the spread of virulent footrot to other graziers.
The quarantine Order will be released 10 days after all sheep are sold for slaughter. With flocks
undergoing treatment for eradication purposes, the quarantine Order will be released in the following
spring if there is no evidence of virulent footrot present after animals have grazed during a suitable
spread period.
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It is an offence under the Livestock Act to put sheep with virulent footrot in a public market. Detection
can lead to a fine or prosecution.
On-farm Eradication Programs
Important Points to Consider for an Eradication Program

Rely on the experts. An on-farm eradication program that is undertaken under close supervision
of an experienced person (such as experienced veterinarians or Biosecurity SA - Animal Health
Advisors), or with the assistance from an experienced footrot contractor has the greatest
probability of success.

There are no short cuts to eradication. Relying on cheap treatments or missing treatments will
result in failure. Retaining infected animals that do not respond to early treatment will result in a
breakdown of the eradication program.

The eradication program must be planned. Plan your eradication program as early as possible in
conjunction with an experienced veterinarian or Biosecurity SA - Animal Health Advisors. Allocate
suitable periods to undertake control and eradication programs in the flock. Prepare contingency
plans following the eradication phase in case the disease breaks out again in one or two mobs.
Allocate separate areas on the property for clean mobs and infected mobs with separate handling
areas wherever possible.

Maintain Facilities. Eradication is assisted by having sound fencing and good facilities for the
handling, inspection and treatment of sheep.

Do not attempt an eradication program while the disease is still spreading. The disease will
spread at a faster rate than it can be cured. The disease can spread if there is moisture on your
boots when walking through pasture and the average temperature is above 10 degrees C.

Footrot is eradicated mainly by culling. The sooner treatment of infected sheep can be terminated
in non-spread conditions and replaced by culling, the better the chances of eradication.

Slaughter all infected sheep as soon as possible. While infected sheep remain on the property,
they are a threat to clean sheep. Many eradication programs fail because infected sheep stray
into a clean flock or because graziers spend too much time trying to cure infected sheep and not
enough time ensuring that non-infected sheep are, in fact, clean.

Footrot can be elusive! Under dry conditions, some apparently normal animals can carry virulent
strains of the bacteria as small pockets of disease in the claws of their feet. It is also important to
understand that treatments such as antibiotic and footbathing in zinc sulphate can make the
detection of sheep that are not totally cured, more difficult to detect. Footrot cannot be considered
eradicated until the flock has gone through a season conducive to spread of footrot, without
showing evidence of the disease.

Prevent reinfection. It is important not to neglect the likelihood of reinfection from introduced
sheep or from neighbouring properties. Quarantine all introduced sheep for as long as possible to
ensure freedom from footrot.
Voluntary Destocking
Before undertaking an on-farm eradication program, destocking the whole flock or part of the flock
should be considered.
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Voluntary destocking of the whole flock is the most certain way of eliminating footrot as long as care is
exercised in purchasing clean replacement sheep. However, if this option is exercised, it must be
thought through very carefully. Consider the age of sheep, flock structure and cost of purchasing
replacement sheep/cattle. From the time that the last sheep has left the property, a minimum of 10 days
must have elapsed before the quarantine Order is released.
A partial destock is often worth considering to reduce the number of sheep that need to be treated. This
may be a mob or mobs where infection is most severe or in older age groups where the animals are not
so valuable.
If eradication via an inspection and a treat/salvage/cull program is the preferred option, there are three
phases:

Control Phase. This is undertaken before and during the spread period in order to reduce the
level of infection in the flock to the stage where eradication becomes feasible.

Eradication Phase. This involves the detection and removal of all infected sheep in the flock
during the non-spread period

Surveillance Phase. This involves careful surveillance of the whole flock to ensure the disease
has been successfully eradicated, and preventing reinfection.
Control Phase
The control phase should be used during a spread period to reduce the effect of footrot on infected
animals and to minimise the number of animals that need to be culled during the eradication phase.
This phase generally involves foot bathing in a 10% zinc sulphate solution (1 kg zinc sulphate
heptahydrate dissolved in 9 litres of water). The frequency of foot bathing required will vary depending
on the severity of the footrot. It can be as often as weekly, but mostly is undertaken as often as
necessary to control lameness.
Bathing time should be a minimum of a slow walk through a 6 metre footbath. Standing in a footbath for
1 – 2 minutes is even better.
An alternative to zinc sulphate is a Radicate®. This is a copper-based footbath solution. Sheep should
be held in this solution for 15 minutes and then their feet allowed to dry for an hour on concrete or
grating. Treatment must be repeated in 1 – 2 weeks. Good cure rates can be expected in a significant
number of sheep. This product has the advantage of creating an artificial non-spread period between
treatments, allowing inspections to continue even when environmental conditions are conducive to
spread. As this product is copper based it can stain the wool on the lower parts of the body. Over time
this staining will disappear.
Formalin has been widely used in the past. However due to it being an occupational health safety and
welfare (OHS&W) risk, it is no longer recommended.
A bi-valent footrot vaccine has been used on a trial basis in South Australia. It can help with footrot
prevention and as a cure. It does require the footrot organisms to be serotyped first and the vaccine to
be “tailor-made” to that flock. It is not widely used at present due to the cost of serotyping. It works best
if only one or two serogroups are present in the flock. It is not economic or practical if more than 4
serogroups are present.
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Eradication Phase
It is important to understand that footrot is best eradicated mainly by culling. Therefore during the control
phase it is important to have reduced the level of infection as much as possible to minimise the number
of culls.
Outlined below are ways of undertaking an eradication program.
Inspect and Cull Option
In situations where the number of infected animals is low, an inspection and cull program can be used.
This involves three inspections being undertaken on all sheep on the property and identifying those
“clean” animals where no definite footrot lesions are detected. It is recommended that two clean
inspections are achieved on each mob before ceasing inspection of that mob during an eradication
program. Two of these “clean” inspections must be conducted prior to the autumn break.
The initial inspection can be regarded as “clean” if the infected sheep are taken out of the flock and sold
for immediate slaughter.
Following the initial inspection, a further inspection is required 4 – 6 weeks later. If any foot lesions are
seen at this point, a further inspection is required 4 – 6 weeks after that.
If no lesions are observed at the second inspection, the sheep must go through a period when spread of
footrot can occur before the third inspection. At the conclusion of spring (generally November onwards),
the third inspection can be undertaken. If no virulent footrot lesions are present, the quarantine Order
will be removed.
If virulent foot lesions are found, repeat the process over the following 12 months or look at another
control option.
Inspect and Treat Option
The inspect and treat option also involves three clean inspections similar to the inspect and cull program.
The initial inspection is used to identify clean from infected animals. Once this has occurred, all clean
sheep must be grazed separately from the infected sheep.
After foot paring, the infected sheep must be treated with long-acting antibiotic or a 10% zinc sulphate
solution. Animals treated with antibiotic need to be kept on grating for 24 hours. Please see separate
Fact Sheets to obtain more detailed information relating to using zinc sulphate solution or antibiotics for
treating footrot.
All sheep are required to be inspected again 4 – 6 weeks later. The clean sheep should be inspected
first followed by the infected sheep. Any sheep showing lesions and particularly those in the infected
mob that did not respond to treatment should be sold for immediate slaughter.
If the non-responder sheep are sold immediately for slaughter this can be counted as the first clean
inspection and another clean inspection is needed 4 – 6 weeks later.
If any lesions are seen at the second inspection, an additional inspection is required another 4 – 6
weeks later.
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If no lesions are observed at the second inspection, the sheep must undergo a ‘spread period’ before
the third inspection. At the conclusion of spring (once pastures have dried off) the third inspection can
be undertaken. If no lesions are present, the quarantine Order will be removed. If lesions are detected,
repeat the process over the following 12 months or examine another option.
For both the options outlined, any additional inspections that can be added before the autumn
break will improve the probability of success.
Five Day Footbathing
Five-day foot bathing is a treatment option that can be used as a disease reduction measure in winter
and early spring, or at the commencement of summer. It involves foot bathing in a 10% zinc sulphate
solution for 10 minutes on 5 successive days. It will not eradicate virulent footrot but will dramatically
reduce the level of benign footrot (Score 1 and 2).
Surveillance Phase
The surveillance phase is for the early detection of any breakdown in the eradication program and
having a contingency plan to deal with any breakdown, and for preventing re-infection from strays or
introductions.
Stock need to be inspected regularly during the months after eradication has occurred. Should any
lameness be observed it is important to have it assessed by an experienced sheep veterinarian or
Biosecurity SA - Animal Health Advisor.
If a breakdown is detected, the contingency plan needs to be implemented in order to minimise the level
of infection in the rest of the flock. This will involve keeping infected mobs separate from clean mobs
and utilising facilities so that the risk of spread from infected sheep to clean sheep is minimised.
Footrot in goats
Footrot in goats appears differently to that in sheep and is usually confined to the interdigital skin underrun and separation of the heel, sole wall and toe of the hoof does occur but not as frequently as in
sheep. Laboratory virulence tests will give a better guide of virulence than clinical signs.
Goats can carry virulent footrot and can transmit it to sheep under suitable environmental conditions.
Any lesions in goats need to be regarded with suspicion.
Footrot in cattle
D. nodosus can occur in cattle. However, the foot lesions are very different in appearance. They appear
as mild inflammation between the claws and do not cause lameness. The strains identified have nearly
always been benign footrot.
If footrot eradication programs are undertaken it is advisable to graze cattle and sheep separately.
During spread periods, cattle movements should be considered as a possible method of mechanical
transfer of the footrot organism between paddocks.
For Further Information
Contact your local private veterinary practitioner or Biosecurity SA - Animal Health Adviser. You may
also phone Biosecurity SA – Animal Health at Glenside on 8207 7900.
Acknowledgement
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Some material in this fact sheet has been taken with permission from NSW DPI Prime Fact 265 “Footrot
in Sheep and Goats” written by J. Seaman and M. Evers.
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