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Biosecurity on sheep farms

Biosecurity refers to the management practices that are undertaken to prevent the introduction and spread of diseases. Healthy animals are the cornerstone of a successful sheep enterprise, regardless of the reasons for sheep ownership.

These days, there is a heightened awareness of biosecurity due to the risks of bioterrorism and the fear of introducing foreign diseases such as foot-and-mouth disease into the United States. Individual states are also interested in keeping diseases from within their borders.

Biosecurity is important no matter what size flock or farm you have. It only takes one sheep to introduce a new disease and one farm to start a disease epidemic.

Acquisition of new animals

The introduction of new animals poses the single greatest risk to biosecurity on a sheep farm. While livestock may appear outwardly healthy, they could be carrying a wide variety of diseases. Anytime a new animal is introduced to the flock, there is a potential risk of that animal introducing a new disease. It is important to note that sheep and goats share most of the same diseases. Sheep and goats also share some diseases with cattle and camelids.

Before adding new sheep to your farm/flock, it is important to know the health status of the farm/flock(s) from which you are buying or receiving animals. Do not be afraid to ask questions about the farm’s health program and the disease status of the flock.

Only buy sheep from reputable breeders. Ideally, you should purchase sheep from closed or mostly closed flocks. A closed flock is a flock that has not introduced new animals for the past three or more years. It is best to buy sheep from as few sources as possible.

It is generally not recommended that breeding stock be purchased from a sale barn (stockyard, public livestock auction). There is even a risk when you purchase sheep from a consignment sale or fair, as sale animals have contact with other livestock and you do not have a chance to inspect the farm where the sheep originate.

You should not purchase animals from flocks or farms in which you observe lameness, abscesses, sore mouth, ringworm, cloudy eyes, or other clinical signs of disease. While healthy-appearing animals may still be harboring these diseases, many diseases can be avoided by thoroughly observing and inspecting the animals you purchase and the farm from which they originate.

Inspect for soundness

Mature ewes can be a good option when starting or expanding a flock, but you need to make sure they are healthy and sound. When purchasing mature ewes, be sure to palpate their udders to make sure they don’t have any lumps, scar tissue, or hard spots, which could be indicative of mastitis. If both halves of the udder are “hard,” the likely cause is ovine progressive pneumonia (OPP). Examine their teeth to determine their age and soundness. Ewes with broken mouths may only have few productive years left. Palpate the testicles of rams. Do not purchase rams with reproductive abnormalities or structural defects. Make sure their mouths are sound, too.

Ovine progressive pneumonia (OPP)

To prevent the introduction of OPP to your flock, try to purchase animals from OPP-free flocks, as verified by test results. Unfortunately, there are not nearly enough flocks that test and cull for OPP — despite a study showing that 26 percent of sheep are infected with the OPP virus. Cross transmission is possible between OPP and CAE (caprine arthritic encephalitis) so make sure if there are goats on the farm that the goat herd is CAE-free.


To prevent the introduction of scrapie to your flock, try to purchase animals from scrapie-free flocks or enrolled flocks. The purchase of sheep with scrapie-resistant genotypes (RR or QR) will also help to prevent scrapie from occurring on your farm. Fortunately, the prevalence of scrapie in US sheep is low and the country is coming close to eradicating the disease. With this said, the last cases of scrapie will be the hardest to find.

Isolate new sheep

Newly-purchased sheep should be isolated for at least 2 weeks, preferably 30 days, before being co-mingled with other animals on your farm or being turned out to pasture. A period of isolation provides an opportunity to detect a disease problem before the rest of your sheep or premises are exposed.

Isolation/quarantine areas should not share the same space with the rest of the flock. A distance of at least 100 feet is recommended. The farther the isolation pen is from the rest of the flock, the better it is. The isolation area should be confined, ideally another building. If another building is not an option, you should select a corner of your barn for isolating new animals. Isolated animals should not have nose-to-nose contact with the rest of the flock.

While in isolation, new animals should have their hooves trimmed and inspected for footrot and other hoof problems. It is not a bad idea to assume that any new animal has been exposed to footrot. Making the sheep stand in a footbath of zinc sulfate is a good preventative measure to keep footrot off a farm. Koppertox or a zinc sulfate spray can be used on the hooves of individual animals. An antibiotic can be used to treat footrot. Footrot is usually introduced (via bacteria) to a farm through the introduction of infected animals. Foot scald, on the other hand, is caused by bacteria that is already present in sheep (and other livestock).

To prevent the introduction of drug-resistant worms, new animals should be dewormed with dewormers from all three dewormer classes: albendazole + moxidectin + levamisole. A fecal egg count 10 to 14 days after treatment will indicate whether or not the treatment was effective. A negative or near zero fecal egg count is the goal. It will be helpful to learn the deworming history of the farm from which you purchase or receive new animals: which dewormers have they used and how often do they deworm.

Buying animals at a sale barn

Purchasing animals at sale barns (or stockyards) greatly increases the risk of a new disease entering your farm and infecting your flock. When you buy animals at a sale barn, there are no guarantees, written or otherwise, that the animals are free from contagious diseases.

Since there are no health requirements to sell at a sale barn, it is possible to take animals infected with sore mouth, pinkeye, caseous lymphadenitis, footrot, or other contagious diseases to a sale barn. These animals can expose healthy animals at the sale barn. In addition, most producers take their cull animals to sell barns. An animal that looks okay may actually be harboring a disease or other problem that will prevent it from being a productive animal. Buyer beware!

Despite the risks, sale barns can be a viable source of slaughter and feeder lambs and even breeding stock. However, sale barn animals should only be purchased for breeding by experienced shepherds who know what they are doing. It is best to purchase ewe lambs and ram lambs for breeding since there is less chance of them introducing reproductive diseases or problems.

If you purchase animals from a sale barn and bring them to your farm, be sure to keep them separate from the rest of your flock. Separate barns and pastures for sale barn animals will lessen the chances that you will introduce a new disease to your farm. If you plan to add sale barn animals to your flock, you should quarantine them for at least 60 days.

The risk of showing

Taking your animals to shows and other exhibitions greatly increases the risk that you will introduce a new disease to your farm. Contact with other animals at a fair can expose your animals to various infectious agents. Try to minimize the nose-to-nose contact your animals have with other animals at the fair.

While at the fair, try not to share equipment, waterers, or feeders with other exhibitors. If you loan your equipment to someone, make sure it is disinfected before you use it on your animals. When you return from a show, isolate your show animals from the rest of your flock. Treat them as if you just purchased them.


Some diseases can be introduced and spread by shearing. Of particular concern is caseous lymphadenitis, an infectious, contagious disease that is the third leading cause of carcass condemnation in cull ewes. To prevent infections from being introduced and/or spread, shearers should disinfect their equipment between flocks and between sheep. Shearing the youngest sheep first will also help to prevent the spread of disease.

Club lamb fungus (ringworm) has become common among show lambs. Shearing equipment and frequent close shearing are the primary reasons for the disease’s spread. Good hygiene, careful shearing, and less frequent grooming may help to limit the spread of the disease to other sheep and people. Do not share equipment without proper disinfecting.

Limit access to your farm and flock

Some diseases can be spread by contaminated footwear and vehicles. By limiting access to your farm and sheep, you can limit the risk of introducing and spreading diseases. When people are given access to your sheep flock, they should not have been on another sheep farm for several days. They should be required to wear plastic boots or thoroughly disinfect their footwear before entering your sheep-raising areas. Make sure trucks and trailers are clean.

Persons who have been in foreign countries within the prior 5 days should not be allowed to visit your farm. If you travel to a country that has the foot-and-mouth disease, it is best to leave your protective clothing and shoes there.

Good management

Rodents, cats, and other wildlife can harbor infectious agents. Some method of rodent control should be employed on the farm. Usually, this is cats. To prevent ewes from becoming infected with toxoplasmosis, one of the leading causes of abortion in sheep, young cats should be kept away from stored hay and grain. It is best to neuter and vaccinate any cats on the farm and maintain a healthy, stable, adult population of cats.

Dead carcasses, and placenta, and fetal tissues should be removed immediately from the sheep-raising areas to prevent the introduction and/or spread of diseases. The ewe should not be permitted to eat her placenta, as this can spread diseases, such as scrapie and abortion. Composting is often the best way to dispose of reproductive wastes.

Under no circumstances should carcasses and other waste products be left for dogs or wild animals to eat. This attracts predators and scavengers and can spread diseases. Sheep measles (cysts in the meat) is perpetuated when dogs and other canines are allowed to consume sheep carcasses. Dogs that eat infected placentas can pass the infective organism in their feces, further infecting the premises and other sheep.

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