Footrot in Sheep
Of the many diseases sheep can catch, footrot can have the greatest economic impact and can be contracted rather easily.
There are many diseases sheep can catch. Many are frequently written about but I would like to emphasize one that in my experience and opinion may have the greatest economic impact and can be contracted rather easily. That disease is called footrot.
My flock of White Dorper sheep is free of footrot (also known as hoof rot) and always has been. I wish to keep it that way. However, in my almost 40 years of being a shepherd and sheep farmer, I experienced many flocks with footrot and gained more skill cutting diseased hooves than I ever wanted to gain.
A footbath with a zinc sulfate solution can be used for both prevention and treatment of footrot. Ulf Kintzel / White Clover Sheep Farm
Footrot in sheep is a contagious disease, caused by two different bacteria, which must be present simultaneously to cause the disease. The first is Fusobacterium necrophorum. These bacteria are normally present in the pasture. They alone will not cause footrot, but they may cause foot scald, especially in muddy and rainy conditions when temperatures are above 50 degrees. Foot scald is an inflammation between the cloven hoofs and makes sheep limp. It rarely spreads further by causing cavities in the hoof. If it does, it usually undermines the horn just a bit. Foot scald is classified as a disease but for practical purposes, I’d like the reader to look at it as something that is a “condition.” That means, if you remove the conditions for foot scald, you will eliminate additional cases of foot scald. While affected animals need to be treated, it is not contagious, which is often evident in the fact that one sheep’s hoof is affected but not two or three or even four. A footbath with a solution of zinc sulfate is the treatment of choice. Sometimes a sheep’s hoof needs to be cut back and the cavity cut out since the bacteria may continue to thrive if the zinc sulfate solution does not reach all of the cavity. A solution of zinc sulfate can also be put directly on the infected hoof if a foot bath is not a workable solution.
I am addressing foot scald in such length because it can be confused with footrot. Note, foot scald does not cause an offensive or strong odor as footrot does, which has been described like the smell of rotten cheese. That is a clear indication that the disease you are dealing with is scald and not footrot.
The second bacteria to cause footrot in tandem with Fusobacterium necrophorum is Dichelobacter nodosus. How do you get Dichelobacter nodosus onto your farm? Contrary to popular belief, it doesn’t come in by birds or some other airborne means. It comes in by either a purchased animal that was affected (the most likely scenario) or an outside source carried affected material onto the farm, e.g., manure on shoes or on a trailer.
Footrot is highly contagious. There are different strains, some considered benign, some considered virulent, but they are all contagious and problematic. It makes sheep limp rather heavily. Very often, sheep are affected on several or all of their hooves and they may then not want to walk at all.
The lifetime of Dichelobacter nodosus in the soil and manure is relatively short. On pasture, it lives up to two weeks. In muddy areas that remain wet it may live up to several months. It is in the sheep’s hooves where the bacteria can survive the longest, up to a few years. Some sheep, seemingly unaffected, are latent carriers that will keep the disease present during dormancy.
The level of infections goes cycles. Warm, wet, and humid weather, muddy conditions, or having the sheep in the barn will lead to another outbreak. Dry and cold weather will help to reduce the number of infections. A downturn in infections will not mean that the disease is gone. It will come back when the conditions for the bacteria are more favorable. The disease will not go away on its own. Sheep do not build true resistance or immunity.
Treatment
To treat sheep with footrot successfully, the first step is to cut the hooves and remove with surgical precision all horn that is undermined by the bacteria, has been separated from the flesh, and caused cavities. If a cavity is not entirely removed, the infection may continue. Any bleeding must be avoided, or it will be difficult to see the cavity and if its removal has been complete. This requires a certain skillset, which will take years to acquire. Any subsequent treatment will not be successful without removing the cavities.
Infected sheep can then be treated afterwards with a solution of zinc sulfate or copper sulfate. Oxytetracycline, either put on the hoof directly or given as an injection, also curbs the infection.
An additional footbath for the entire flock after treatment as described helps heal the diseased hooves and curbs further spread. It can also be used in a preventative way if another outbreak is suspected.
I use five plastic footbaths in a tight row in my chute for preventative measures. I purchased them at Premier One Supplies, the only supplier of footbaths for sheep in the US. They are 47″ long, and 18″ (at the bottom) to 20.5″ (at the top) wide. They are made of extremely durable plastic. The width matches the width of my chute. That means there is no room to the left or right of the footbaths and thus the sheep are forced to go through them, cannot sidestep them to avoid them. Why do I have a need to run my flock at times through a foot bath? On occasion, I have a few animals with foot scald and the foot bath stops such infection immediately. In addition, it is a great tool to not let footrot take hold in the first place.
There are three possible active ingredients that can be used for the footbath as treatment of footrot that will kill the bacteria causing footrot:
- Zinc sulfate. Zinc sulfate is in my view the substance of choice to treat footrot. It can be purchased in a fifty-pound bag (often labeled as feed grade zinc sulfate) or in liquid form in a jug. It is non-corrosive to metal and does not stain.
- Copper sulfate. Copper sulfate comes in the form of a blue salt or salt crystals, also available in a 50-pound bag at some farm or feed stores. It is corrosive to metal, and it stains wool green
- Formaldehyde/Formalin. Formaldehyde is very effective but potentially environmentally problematic and harmful to people. It also hardens the hoof, which makes additional hoof cutting difficult. I advise against using it.
Any of the above ingredients will be mixed with water in a foot bath. I put a good feed scoop of zinc sulfate in each footbath and add a little dish soap to aid penetration. Each of these foot baths holds 25 gallons of water but I do not fill them to the top, especially if I have small lambs in the flock. Each sheep should stand for a prolonged while in the footbath. It should be a minimum of a few minutes. Longer is better.
Lastly, if you see that the same sheep get reinfected first if there is a new outbreak, cull these animals now no matter how productive they are otherwise.
If you wonder if it is even possible to eradicate the disease, especially if you have a sizable flock, then I don’t have encouraging news for you. It is very labor intensive and not always successful. This is why I am so afraid of it. I know a few who succeeded and many who didn’t. In addition, a vaccine against it is not available in the U.S.
What is an alternative solution when you don’t acquire the skillset necessary to cut hooves properly, removing all cavities almost surgically? What if you have a very virulent strain of footrot in your flock? If your flock is small or not very valuable, you may want to consider starting over. After you culled your flock, let the farm and barns rest for a few months, to be safe a full season if possible. The winter months are ideal to rid your place of Dichelobacter nodosus. Remove thoroughly all manure in the barn. Leave no wet or moist or muddy spots in place. Spread lime in the barn, barnyard and places around structures that could contain bacteria. When you purchase a new flock, ask if the breeder’s flock is free of footrot. A flock owner who doesn’t have it in his flock will gladly volunteer that information. I certainly do.
Prevention
It pays to put some simple biosecurity protocol in place to avoid an outbreak of footrot. The first and most important part of it is knowing where your animals come from. Buy from a trusted source, don’t source breeding stock at the livestock auction for slaughter animals. Quarantine purchased animals for a few weeks when you bring them home in a place where hoofrot can be contained if there is an outbreak. Know who enters your barn and your pasture, don’t allow access without permission. People who are allowed to enter should wear clean shoes. If your animals get picked up by a livestock hauler, ask them to come with a clean trailer, especially if they recently have transported sheep or goats for other people.
