Caseous Lymphadenitis or "CL" is a bacterial infection which causes abscesses to form in the skin of the infected animal. It can lead to chronic weight loss and loss of productivity. Infection is generally spread through contact with the contents of the abscesses, so care is needed, especially during shearing, to disinfect anything that opened an abscess. When buying animals, run your hands over them to feel for lumps, and examine those lumps to see if they may be CL. It cannot be cured through antibiotics.

Foot and Mouth, or Hoof and Mouth as it is known in the US, is a highly contagious disease which causes severe productivity losses in farm animals. Sheep are considered 'carriers' of the disease in that they rarely show much sign of infection themselves, but can carry the virus for many months, infecting other animals exposed to them.

North America is free of Foot and Mouth, but in Central and South America, Africa, Asia, and parts of Europe, it is endemic, meaning that it's so entrenched in the animal population that it can't be eradicated, only controlled. Freedom from Foot and Mouth is important economically, as countries which have Foot and Mouth cannot export meat to countries which are F&M free.

Foot rot is the common name for a bacterial infection of the foot which causes the sheep to become lame. Check the hoof for soft places and a really bad smell. If you suspect foot rot, remove the sheep immediately to an area you won't be using for sheep again for a long time, or can decontaminate, as the bacteria can hang around in the environment for years. Consult with your vet for treatment options. Often this consists of a footbath the sheep walk through. The entire flock should be treated, as more sheep may pick up the infection from the ground. The bacteria which cause foot rot are anerobic, meaning they live in oxygen-free conditions. Trimming your sheep's hooves regularly can help prevent infection.

Johnne's (pronounced yonnie's with a long "o") Disease, or paratuberculosis, is a chronic bacterial infection of the mucus membranes and lining of the intestines. Symptoms include chronic diarrhea and gradual loss of condition, leading to death. Some people believe Johnne's can be cured with adjusting the copper intake upwards slightly, while providing additional vitamin C and B complex. We've never had Johnne's on our farm, so we just present this information in case you want to give it a try.

OPP is short for Ovine Progressive Pneumonia, a viral infection seen in older (over 2 years old) sheep. In other countries it's called Maedi Visna. Progressive weight loss and difficulty in breathing are two symptoms. It is possible to test for OPP, but false negatives do occur, so it's best to have two or more successive whole-flock tests to see if your flock is really free of this disease. Afterwards, test all incoming animals and test older animals randomly. No vaccine exists to prevent this disease.

Orf, or soremouth, is a viral infection causing lesions, or sores, in the sheep's mouth. Although it can cause the sheep to go off its feed, Orf is not life-threatening as long as the sheep are carefully managed to avoid secondary infections.

Orf is highly contagious, can live in the environment for years, has several strains, and can be transmitted to humans, causing very painful sores at the site of the contagion. Wear examination or household rubber gloves when working with sheep who have, or have been exposed to, Orf, and be very careful about touching the sheep. Disinfect all equipment prior to working with healthy sheep. The scabs are particularly infectious. Shearing and washing sheep after they have healed can help remove the scabs, but wherever they end up on the soil will remain a source of contagion for years.

Once they've recovered, sheep will be immune to that particular strain of Orf in the future. Although immunizations are available, they are considered unnecessary in most situations, unless the disease is endemic in your flock. Consult with your vet if you think Orf might be a problem for your flock.

Internal parasites can be a problem in the best-managed flocks. Virtually all sheep carry some parasites in their guts all the time. Some controversy surrounds methods of controlling these parasites. Some worms are developing resistance to the drugs used, while those drugs, in many cases, were developed for cattle and use on sheep is extra-label and therefore somewhat experimental. Some shepherds swear by the use of organic methods of control, such as using diotomaceous earth, while others believe DE is quite ineffective.

About the only thing that's certain is that careful management of feeding practices can at least lessen the impact of intestinal parasites. The worm's living cycle is the key: Interrupt the cycle, and you will reduce the wormload on your sheep. You probably will not eliminate them, but you can select sheep who are thrifty and healthy in spite of a moderate load.

Worms are shed as eggs in the sheep's manure. If a sheep grazes that area within about 10 days after the egg landed on the grass, the sheep can accidently eat the egg. Some worm eggs may last longer than that; check your vet for information about the particular type you suspect or have identified in your flock. Once ingested, it lands in the intestines and hatches out to become a worm, feeding on the blood of the sheep. The worm lays some eggs, which are shed again, and the cycle continues.

If the sheep are moved frequently, and not brought back to graze a given area for at least 10 days, the eggs will die as their host is not available. Worms may still live in the sheep, but the wormload will be greatly less than if the sheep is continuously ingesting eggs.

External parasites include keds, a small tick-like creature, and biting and sucking lice. Most shepherds control blood-sucking insects with an oral or injectible medication. Biting insects need an external, pour-on medication to eradicate them, which is best done soon after shearing to get the best coverage of the skin.

Pregnancy Toxemia, or ketosis, is a non-infectious condition which can occur during late gestation. When the ewe doesn't get enough energy in her feed to make up for the demands of pregnancy and sometimes environmental stress such as severe cold, she will begin to use her fat stores for energy, which can cause a build up of ketones. She will go off her feed first, and you may smell something like nail-polish remover on her breath. If she goes down, it's an emergency situation. To prevent toxemia, keep ewes in good condition as they go into pregnancy (both thin and fat ewes are more likely to have problems with ketosis), provide shelter (a windbreak may be sufficient) from severe cold, and adjust their feed to provide more calories in late pregnancy, particularly to ewes suspected of carrying triplets or more. Often it's as simple as offering some corn each day.