Common diseases affecting sheep

“The biggest threat to your sheep is another sheep. The second biggest threat is a person,” warned George Saperstein, DVM of the Tufts University Cummings School of Veterinary Medicine’ Sheep School. Participants were asked to scrub their boots before and after visiting the farm to minimize disease risks. The bacteria that cause sheep foot rot can live in soils, or on boots, for as long as 14 days.


Dr. Saperstein advised all farmers to provide a footbath and/or disposable booties for any farm visitors, especially farm and livestock dealers. Insist everyone participate. Vets should arrive with their own bucket and brush, and they should use it without being asked. “Vets and all farm visitors should enter the farm clean,” recommended Dr. Saperstein.

According to Dr. Saperstein, when sourcing animals it is nearly impossible to find 100% guarantee of healthy sheep. They are all potentially carrying some organism that may or may not be causing illness at the time of the exam. Vet certificates help, but all any vet can really say is that there a no signs of disease on that day, and there is no history of illness. Without extensive testing, vets may not see signs of many diseases or internal parasites. Farmers may or not share information about field or show exposures.

Your best biosecurity is to breed your own animals. Realistically, after about five years, chances are all your sheep will be too closely related and you will need at least a new ram for genetic diversity. Dr. Saperstein recommends a four to six week quarantine for all new animals. This will allow you to watch for any symptoms and arrange for a second set of tests (blood and parasites). Be sure your new animal is well, before adding it to your herd.


Healthy sheep are “B A R or Bright, Alert and Responsive,” said Herdsman, Scott Brundage of Tufts University Cummings School of Veterinary Medicine Risks of illness rise with poor diet, management or daily care. Risk factors include genetics, reproductive problems, transportation stress and extreme weather. Watch for drool, skin discharges, lumps/bumps/bruises, behavioral changes or breeding problems.

Make sure your “sick sheep pen” is not a “dying sheep pen.” Clean out and sanitize every surface, and install new bedding between patients. Quatricide is recommended as a sanitizer and zinc sulfate for footbath treatments for foot scald and foot rot

Foot Scald is common in wet seasons like the spring of 2012. If untreated, or if sheep are genetically vulnerable, this disease can progress into foot rot. Sheep are skittish about walking through or standing in a footbath for the five minutes needed for effective treatment. Tom Colyer, sheep farmer at Greenwood Hill Farm in Hubbardston, MA, and President of the Massachusetts Federation of Sheep Association, shared his success with laying wool in a footbath next to a grain trough.

Soremouth looks like blisters on the lips or udder, and is a common sheep disease, often causing lambs to nurse less, decline or even die. Infected older sheep tend to eat less than usual. Soremouth generally goes away by itself in about two weeks, but once a farm or sheep has soremouth, the virus may never go away. A vaccine is available and protects sheep for one to two years at a time. Exposure is most common at shows.

One other problem with soremouth is that the virus can be transferred to humans where it can cause painful sores that may last up to two months. Luckily, it does not transfer between people. Staff should cover all cuts if working around animals. Regular hand washing is recommended for all farm staff.

CLA (Caseous lymphadenitis) can be diagnosed when lymph nodes at the neck and shoulder swell and become abscessed. It can be hard to detect CLA when sheep are covered in thick wool, but opened abscesses make a mess of wool during shearing. Be sure to ask about flock history of CLA when buying new animals. Be sure your shearer sanitizes equipment between farms, (ideally between animals) or use another shearer who does!

Flystrike, or maggots can be a problem when sheep have long, wet wool. The moisture attracts flies that can spread secondary illnesses. Dr. Saperstein recommended, “Keep your animals clean and dry for better health.”

Pregnancy Toxemia happens when blood is low in glucose concentration and animals break down too much body fat to compensate. “Ketones” are a toxic by-product of fast fat breakdown. This disease is also called Ketosis, Pregnancy Disease, Twin Lamb Disease and Lambing Paralysis. Use urine tests to detect Ketosis. To get a urine sample, pinch a sheep’s nose.

Overly large or fat sheep often develop toxemia late in their pregnancies (110 to 120 days) Small or thin sheep carrying twins or triplets can also develop Toxemia and lose one on more lambs preterm. Watch for unusual behavior or symptoms like weight loss, weakness, little or no appetite and isolation. Treatments may include feeding corn meal, which is high in energy, or supplements of 10 to 20 ml of propylene glycol several times a day. This type of sugar precursor can be readily processed for energy in ruminants. Other sugars just sit in a sheep’s stomach and ferment.

Brundage recommends daily checks on each animal, noting of any changes and offered helpful mnemonics. For daily checks: “A D R” – Ain’t Doing’ Right. At purchase time, use: “F A M E” – Free (of physical defects), Alert, Mobile and Eating. Sick sheep can be difficult to recognize because survival instincts have evolved in these prey animals that prevents them from showing weakness until the disease has progressed. Farmers need to be vigilant to spot declining animals early so treatments have the best chance of effectiveness.

Blue Bag or Mastitis is an udder infection of the mammary glands causing swelling and soreness. Farmers will find the udder hot, hard and swollen. Brundage recommends gently warming the medicine, especially in winter, to avoid injecting a cold treatment into a hot utter. On selecting a treatment, Saperstein advised, “If the udder is sick, treat the udder; if a sheep is sick, treat the whole sheep.”

Haemonchus contortus or barberpole worm is a common internal parasite in the northeast. This bloodsucker weakens sheep and sets up secondary infections that can kill. Other parasites can include ticks, lice and sheep keds and mites that can affect wool quality because infested animals scratch against fences and trees, decreasing fleece quality and value. After identification of the exact pest, treatments should be carefully timed to that pest’s life cycle. Most treatments interrupt the molting cycle between the second and third instar stages. Use the FAMACHA chart to help determine worming needs. To minimize the risk of treatment-resistant parasites, only deworm sheep in need of treatment using feces testing.


If castrating rams, be sure to give one tetanus antitoxin at that time. As a public safety, keep show animals current with rabies shots. There is a soremouth inoculation available as a swab of mild, live virus delivered at a deliberate skin abrasion site.

All sheep should get CD-T toxoid vaccines annually, after two shots the first year, to protect against Tetanus and enterotoxemia type C. (also known as Hemorrhagic Enteritis or Bloody Scours) infected lambs under one month will have bloody infections in their small intestines. Older lambs are vulnerable to Enterotoxemia type D, (overeating disease or pulpy kidney disease). This affects large, fast-growing lambs when a sudden change in their feed causes gut bacteria to multiply to toxic, often fatal, levels.

Vaccinating pregnant ewes four weeks before lambing gives lambs passive protection as long as they get colostrum. First time moms should get two shots: one at eight weeks and one at four weeks before lambing.

Mineral Needs/Toxins

Free choice salt is critical to helping sheep (especially rams) drink enough water. Be sure there is free choice water year round; run a heater as needed to prevent ice forming in bowls, troughs and lines. Tufts uses an automatic waterer.

Sheep cannot tolerate as much copper in their grain or salt blocks like horses or other ruminants. Farmers must insist on low copper sources as sheep quickly accumulate a fatal level of copper in their systems.

Recommended Reading

Dr. Saperstein ­­­recommended the “SID Sheep Production Handbook” put out by the American Sheep Industry Association, Inc. This has been the best reference available for raising sheep for many years. It is available in print and on CD.

Annual Livestock Workshops

Each year, New Entry Sustainable Farming Project and the Tufts Cummings School of Veterinary Medicine offer a variety of livestock training workshops for beginning and experienced farmers. The public is also welcome. Workshops may include topics like these:

  • Livestock Farm Day
  • Sheep School
  • Internal Parasite Management for Small Ruminants
  • Pastured Poultry Farm Tour
  • Feeds, Forage and Nutrition
  • Cattle Behavior and Handling

The New Entry Sustainable Farming Project helps beginning farmers gain the skills to be successful, builds local food security in participants’ communities and grows local food networks. To learn about upcoming workshop and programs, join the New Entry email list at, like their Facebook page or contact Sam Anderson at or 978-654-6745. For other questions on the Tufts Cummings School of Veterinary Medicine in North Grafton, MA, see You can visit the Tufts Cummings School of Veterinary Medicine at 200 Westboro Road, North Grafton, MA 01536.


About Sanne Kure-Jensen

Sanne Kure-Jensen is a frequent contributor to Country Folks, Country Folks Grower and Wine & Grape Grower bringing regional and national attention to agriculture in RI and across southern New England. She has also written for newsletters of the Northeast Organic Farming Association (NOFA), Holistic Management International (HMI), RI Beekeepers Association and RI Tree Council. Read Sanne’s work at her Sustainable Living page at Sanne has written successful grant applications for alternative energy projects, staff and board training, products and services. Clients include agricultural businesses, farm stand/markets and non-profit organizations. Recent successful grant projects include a $90,000 USDA Rural Development‘s Rural Energy For America Program (REAP), $10,000 Sustainable Agriculture Research and Education (SARE) Farmer and $20,000 Natural Resources Conservation Service (NRCS) Conservation Innovation Grant (CIG). Sanne is the part-time Administrator for NOFA/RI, a Rhode Island Certified Horticulturist and beekeeper. She is a NOFA Accredited Organic Land Care Professional and has lectured across southern New England on Beekeeping, Native Pollinators and Ecological Landscape Design. Learn more about the NOFA’s Land Care programs or contact Sanne for a garden consultation through the NOFA/RI website.
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