Showing is a biosecurity risk
Show ram with abscess
Shearing can introduce diseases
Maintain a closed flock
AI can reduce the spread of diseases
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 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
You should not purchase animals from flocks or farms in which
you observe lameness, abscesses, soremouth, 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 in the U.S. 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 USDA certified 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.
Caseous lymphadenitis (CL)
Club lamb fungus (ringworm)
Epididymitis (B. ovis)
Ovine progressive pneumonia (OPP)
Pink eye (infectious keratoconjunctivitis)
Rift valley fever
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
confinement, 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 foot rot. 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 foot rot. Footrot is usually introduced (via bacteria) to a farm
through the introduction of infected animals. Foot scald, on the other hand, is caused by a 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 soremouth, 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 sale
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.
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
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 foot-and-mouth disease,
it is best to leave your protective clothing and shoes there.
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
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 which eat infected
placentas can pass the infective organism in their feces, further
infecting the premises and other sheep.
Preventative health management
A vaccination program provides inexpensive insurance against
common sheep diseases. It is generally recommended that all
sheep and lambs be vaccinated for clostridial diseases. CDT provides protection against the most common clostridial diseases: clostridium perfringins type C & D (overeating disease) and tetanus. Covexin®-8 confers protection for additional clostridial diseases. The use of Covexin®-8 and other vaccines depends upon the disease risk and
diagnosis of particular diseases in the flock.
Vaccines are available for soremouth, caseous lymphadenitis,
vibrio and chlamydia abortion, epididymitis, and rabies.
There is limited availability of a vaccine for foot rot. Some vaccines (e.g. soremouth, caseous lymphadenitis)
should not be used unless the disease is already present on
the farm because vaccination will introduce the disease to the
farm. Such vaccines are advocated to reduce the incidence of
disease, not prevent it in its entirely.
Gastro-intestinal parasites (worms) are the primary health problem affecting
sheep raised in warm, moist climates or during periods of warmth and moisture. A parasite
control program that integrates management practices with targeted selective deworming (using the FAMACHA© system, 5-point check©, or performance indicators) should
be implemented. Regular deworming of all animals in the
flock or in a management group is no longer recommended due to the widespread existence of drug-resistant
worms. To slow the development of resistant worms, it is now recommended that clinically parasitized animals be given combination treatments (dewormers from different chemical classes).
Fecal egg count reduction tests
should be conducted to determine which dewormers are effective
on a farm. If natural products are used in the internal parasite control program, animals should be regularly monitored to see which ones require treatment with "chemical" dewormers.
When a ewe experiences an abortion, she should be isolated from
the rest of the flock. The dead fetues, placenta, and fetal
tissues should be removed immediately and buried or composted.
The lambing area should be disinfected. Antibiotics should be
given (fed or injected) during an abortion storm to prevent
further losses. Chlorotetracycline is FDA-approved for this
purpose. However, a written script must be obtained from a veterinarian. Including monensin (Rumensin®; Rx) or Decoquinate (Deccox®)
in the feed or mineral during the last third of pregnancy may
help to prevent abortions caused by toxoplasmosis.
Maintain a closed flock
The best way to maintain a healthy flock is to maintain a closed
flock. Once the genetics of the ewe flock has been established,
replacement females should be selected from within the flock
and new acquisitions should be limited to rams. Unfortunately,
artificial insemination (AI) is not a very viable option for most
U.S. shepherds, making introduction of new rams periodically necessary.
It may be possible for large flocks to select their own ram
replacements, but for most shepherds, outside ram purchases
are necessary to avoid unacceptable levels of inbreeding. Fortunately,
rams spread fewer diseases than ewes. While rams
can still introduce soremouth, footrot, pinkeye, or caseous
lymphadenitis to a flock, they are not likely to introduce vibrio
or chlamydia. They are not believed to transmit scrapie, though
the use of RR rams will ensure the birth of lambs that are scrapie-resistant.
Epididymitis (caused by Brucella ovis) is a concern in some geographic locations.
You should not loan your ram(s) to another farm, unless the
health status of the flock is equivalent to yours (or better). You should not allow
other producers to bring ewes (or does) to your farm for breeding,
unless the health status of their flock is equivalent. There
are other ways to help 4-Hers and new shepherds besides making
your farm and animals available to them.
Producers are encouraged to develop a written biosecurity plan and to follow it to prevent the introduction of diseases and other problems.
<== SHEEP 201 INDEX