Bonus Tydskrif Winter 2023

Cheesy gland, also known as caseous lymphadenitis (CLA), is a chronic infection caused by the bacteria Corynebacterium pseudotuberculosis in small ruminants. This bacteria can be found in the environment on soil and contaminated food. It can also contaminate fomites such as boots, overalls, shearing blades, bedding, handling facilities etc. Animals can be infected by inhaling the bacteria or through wounds or abrasions on their skin and/or mucous membranes. From there, the bacteria can spread to lymph nodes where it forms encapsulated abscesses. There are two forms of the disease that can be present at the same time: • External, affecting the superficial lymph nodes or subcutaneous tissue. • Internal, affecting the internal lymph nodes and organs. Importantly, this disease is a zoonosis, meaning it can be transmitted to humans from infected animals. Risk factors associated with cheesy gland The risk of contracting cheesy gland is proportional to the infection pressure. In other words, if there is abundant bacteria in the environment, other animals in the flock can more easily inhale or come into direct contact with the contaminated material. Infection pressure is increased when buying in infected animals and introducing them into a naïve herd, or when an abscess on an infected animal bursts and contaminates the environment. Abscesses that burst can release significant amounts of bacteria onto the fleece of the affected animal and its immediate environment. It has been reported that the bacteria can survive for almost two months in organic material in the environment and eight months in soil, especially during lower temperatures. Once the bacteria has established itself on a farm, it easily becomes endemic and is very hard to eradicate. Shearing animals with abscesses can also lead to the infection being spread throughout the flock. If an abscess is nicked by accident, the infection can be spread if the same shearing blades are used on other sheep. If infected sheep are sent through a plunge dip, for example after shearing, they can contaminate the dip. It has been said that the bacteria can survive in dip for up to two hours after contamination. Hence, if the same contaminated plunge dip is used for uninfected and infected animals, there is also an increased risk of spreading the disease. Other management processes that puts animals at risk in an infected By Dr Chantelle Erwee, Zoetis South Africa (Pty) Ltd, Technical Manager: Ruminants Cheesy gland in small ruminants Winter 2023 BONUS www.agribonus.co.za 26