Caseous lymphadenitis in sheep and goats: signs, spread and prevention

Caseous lymphadenitis is one of the most common chronic diseases in sheep and goat flocks worldwide. It rarely kills animals quickly, but it settles into the flock, spreads silently and causes losses through culling, carcass condemnations at the abattoir, lower production and reduced value of hides and wool. If you have ever found a lump full of thick, greenish pus on the neck or under the jaw of a ewe, you may well be dealing with this disease.

In this guide we explain what causes it, how to recognize it, how it spreads and, above all, what you can do to prevent and control it on your farm.

What is caseous lymphadenitis?

It is a chronic infectious disease caused by the bacterium Corynebacterium pseudotuberculosis. It mainly affects the lymph nodes, where it forms abscesses filled with thick, whitish-green material with a “cheesy” (caseous) appearance, hence the name. It is often abbreviated CLA or CL, and in some regions it is simply called “cheesy gland” or “pseudotuberculosis”.

The bacterium is very hardy: it can survive for months in soil, buildings, bedding and shearing equipment, which explains why it is so hard to eradicate once it enters a flock.

Forms of the disease

External (superficial) form

This is the easiest to spot. Abscesses appear in the superficial lymph nodes: under the jaw, in front of the shoulder (prescapular), around the udder or scrotum, in the flank (prefemoral) and behind the stifle (popliteal). In goats, abscesses on the head and neck are more common, while in sheep they often appear in lymph nodes along the body as well.

Internal (visceral) form

The bacteria can reach the lungs, liver, kidneys and internal lymph nodes. This form is the hardest to detect in live animals and is often linked to so-called “thin ewe syndrome”: animals that progressively lose body condition for no obvious reason, with lower fertility and reduced milk or wool production. It is often discovered only at slaughter or necropsy.

Signs: how to recognize it in your flock

• Firm or fluctuating lumps over the lymph nodes that can grow slowly over weeks or months.
• Abscesses that burst on their own and release thick, whitish-green pus with little odor.
• Weight loss and poor body condition with no apparent cause (internal form).
• Coughing or breathing difficulty when the lungs are affected.
• Lower reproductive and productive performance in affected animals.

Important: not every lump is caseous lymphadenitis. Other causes of abscesses and masses include actinomycosis (“lumpy jaw”), abscesses from poorly given injections, cysts and tumors. A veterinarian should confirm the diagnosis, ideally with bacterial culture of the pus or serological tests.

How does it spread?

The main source of infection is the pus from ruptured abscesses, which contaminates the soil, feeders, waterers, handling races and buildings. The most common routes of entry are:

• Skin wounds, especially those caused during shearing, tail docking, marking, dipping, or by fences and thorns.
• Contaminated shearing equipment, which can carry the bacteria from one animal to another.
• The respiratory route, from animals with lung abscesses that shed bacteria when they cough.
• Purchased animals that carry the disease without visible signs.

That is why the disease tends to increase with age: the more shearings and handling sessions an animal goes through, the more chances it has of becoming infected.

Treatment: can it be cured?

The short answer is that treatment is rarely effective. The thick capsule around the abscesses makes it hard for antibiotics to reach the bacteria, and even if an external abscess resolves, the animal may have others inside. For this reason, most extension services recommend focusing on prevention and control rather than cure.

If your veterinarian decides to drain an abscess, it should be done wearing gloves, away from the rest of the flock, collecting and disposing of all the material (for example, by burning it) and disinfecting the area. Never lance a lump in the pen or the handling area: you would be spreading the bacteria to the whole flock. Any use of antibiotics must be prescribed by a professional, respecting meat and milk withdrawal times.

Prevention and control on the farm

1. Check and separate

Regularly palpate the lymph nodes of your animals, especially before shearing. Animals with abscesses should be separated and shorn last, or evaluated for culling, especially if they have recurrent abscesses or signs of the internal form.

2. Hygienic shearing

Shear young, healthy animals first and suspect animals last. Disinfect combs, cutters and shears between groups, and treat shearing wounds. Avoid dipping animals right after shearing in shared baths, since they can spread the bacteria.

3. Facilities and handling

Keep facilities clean and free of nails, loose wire or splinters that cause wounds. Disinfect needles and equipment used for marking, docking and castration.

4. Buying animals

Examine animals carefully before buying them, ask for health information from the farm of origin and keep newcomers in quarantine before adding them to the flock.

5. Vaccination

In several countries there are vaccines against caseous lymphadenitis, sometimes combined with clostridial vaccines. Availability varies by country, so ask your veterinarian whether one is approved in your area and what the right program is. The vaccine reduces the number of newly infected animals but does not cure those already sick.

Does it affect people?

Corynebacterium pseudotuberculosis can, in rare cases, cause lymphadenitis in people who handle animals or infected pus. That is why it is advisable to wear gloves when examining or draining abscesses and to wash your hands thoroughly afterwards.

Keep each animal’s health record with OvinApp

Controlling a chronic disease like caseous lymphadenitis depends largely on knowing which animals had abscesses, when, and what was done about them. With OvinApp, the free app for managing sheep and goats, you can record treatments and health events for each animal from your phone, check their history and make better culling and replacement decisions.

Conclusion

Caseous lymphadenitis is won through consistency: regular checks, hygienic shearing, separating or culling affected animals, care when buying breeding stock and, where available, vaccination. If you find any suspicious lump, consult your veterinarian to confirm the diagnosis and define the control plan best suited to your flock.

Sources

• MSD Veterinary Manual. Caseous Lymphadenitis of Sheep and Goats. https://www.msdvetmanual.com/circulatory-system/lymphadenitis-and-lymphangitis/caseous-lymphadenitis-of-sheep-and-goats
• Penn State Extension. Caseous Lymphadenitis (CL) in Sheep and Goats. https://extension.psu.edu/
• Sheep 101 / University of Maryland Extension (S. Schoenian). Caseous Lymphadenitis. https://www.sheepandgoat.com/
• INTA (Instituto Nacional de Tecnología Agropecuaria, Argentina). Publications on sheep and goat health. https://www.argentina.gob.ar/inta