Caseous lymphadentitis (CLA)

General description

Cheesy Gland (also known as CLA) is a contagious bacterial disease that produces lymph node abscesses in sheep and goats. It can have significant economic impact at slaughter through trimming of carcases and carcase contamination.
Where multiple abscesses are present, carcases will be condemned.
On farm impacts can include reduced wool production and weight loss or reduced growth rates. Most flocks have at least one animal affected with cheesy gland.
The prevalence of cheesy gland can be as high as 30% in unvaccinated flocks, but as low as 3% in vaccinating flocks. Up to 8% of carcases are identified with cheesy gland at meat inspection.
The estimated annual cost to industry is $23 million.

Cause

A bacterial (Corynebacterium pseudotuberculosis) infection of sheep that causes abscesses in the lymph nodes and lungs.

Clinical signs

Most sheep with cheesy gland will show no obvious signs but it is readily detected in the carcase after slaughter.
Recently formed abscesses contain thick yellow-green pus.
With time the pus dries out and the abscess looks like an onion with concentric layers of solid pus.
The most common sites for abscesses are in the lymph nodes on the point of the shoulder, in the groin and in the lungs.

Diagnosis

Treatment

Prevention

Vaccination is the most effective strategy. Consider boosters if flock under high challenge.
Hygiene at shearing and dipping are also key controls.
Shear young sheep first, minimise handling (and treatment) of sheep with wounds (e.g. off shears) and use hygienic methods to handle and treat sheep.
Don’t plunge or shower dip sheep without good reason and ensure good dipping hygiene, including time for shearing wounds to heal.
Keep time in the yards for recently shorn sheep to a minimum.
If an abscess is ruptured at shearing or crutching ensure the handpiece, floor or anything else that is contaminated is disinfected.
Maintain good hygiene at marking.

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