Caseous lymphadenitis (CL) is a contagious bacterial infection by corynebacterium pseudotuberculosis in goats and sheep. The infection occurs through wounds caused by head butting, punctures, and shearing, as well as by oral ingestion of the pus from an abscess (a collection of pus that has built up within the tissue of the body) that has ruptured. The sub cutaneous lymph node system filters the bacteria from the goat’s body and pushes it outside into thick-walled encapsulated abscesses so that it can’t harm the goat. Visible abscesses don’t appear for months after infection as the lymph system slowly filters the bacteria.
The clinical signs of the disease are one or more abscesses that are often located just beneath the skin. However if organisms enter the bloodstream abscesses may also develop in internal body organs such as the lungs or liver. In this case external abscesses may not be present and the only thing that modisa (shepherd) notices is a thin weak and infirm animal. CL is an equal-opportunity infection no breed or sex is exempt. The abscesses contain a thick, yellow to white discharge that has a soft pasty consistency much like toothpaste.
- CL is typically transmitted when subcutaneous abscesses are ruptured. Bacteria from ruptured abscesses are released into the environment allowing transmission to susceptible hosts. When an abscess ruptures it can contaminate pens, water buckets, barns, shearing clippers and feed bunks. The pus contains a high number of bacteria and these bacteria can survive for several months in the environment.
- Another concern with CL is that it’s a zoonotic disease meaning it can also infect people. Although human infection is rare take sanitary precautions when treating and handling infected animals.
- Always wear disposable gloves, and wash your hands and clothes after you have been in contact with a suspect animal.
- Flies can carry the bacteria from nearby infected animals and bring it to your goats
Symptoms and Diagnosis
- The first usual indication of CL infection is the presence of an external abscess visible behind the ears, beneath the jaw or neck, on the shoulders, or in the rear flank region. Abscesses may also appear between the hind legs where a scrotal sac or udder attaches.
- Internal abscesses are detectable only through necropsy, an examination after the animal is dead. Unfortunately it is the internal abscesses that are fatal whereas external abscesses are the ones generally responsible for disease transmission.
- Sheep are more prone to internal abscesses and goats are more prone to external abscesses. If an animal is experiencing chronic weight loss it may be carrying internal CL abscesses on vital organs.
- Because the thick pus is enclosed in a tough fibrous capsule which medicine cannot penetrate antibiotic treatment is ineffective against the CL bacteria. Caseous Lymphadenitis is currently considered incurable.
- Autogenous vaccines made from a specific herd’s infectious pus are sometimes helpful but often only slow down the rate of infection.
- Abscesses can be surgically drained and flushed with iodine solution. However, draining the abscess will increase risk of transmission of the organism to other animals if they are exposed to the pus. The discharge that is present in the abscess should be disposed of in such a way as to avoid contamination of the facilities and remaining animal population.
- Unfortunately abscesses may reoccur after such treatment has been attempted.
- In a case where the abscess has ruptured it should be drained immediately and the infected animal moved to an isolation pen to minimize contamination of the environment.
- In sheep, abscesses are usually not found until shearing. During shearing, the shearer may inadvertently nick the wall of an abscess. If this occurs, shearing should be stopped, and the clippers, blades and general area should be disinfected as well as possible. When trying to prevent infection in younger sheep, the shearing order should be the youngest to the oldest in the flock.
Steps to treat the Abscesses
- Immediately isolate the animal from the herd.
- Place the infected animals on a concrete floor or other surface that will make disinfecting easier to avoid spreading the CL micro-organism.
- Wear gloves when draining abscesses to avoid contamination. The abscess is about to rupture when it has lost hair.
- Use a disposable scalpel to cut the surface of the abscess and drain it before it ruptures on its own in the field.
- Create a cross cut (+) to better drain an abscess.
- Completely drain the abscess of its content; a large amount of pus with the consistency of toothpaste may appear. You may wish to collect some of the pus with a new syringe for submission to a diagnostic lab for pathogen isolation and identification.
- Wash the resulting abscess cavity thoroughly with hydrogen peroxide then flush it with an iodine solution.
- Keep the infected animal from the rest of the herd until the abscess is completely healed.
- Disinfect the area where the animals with the abscesses were housed.Keep records of abscess cases.
- Incinerate gloves, napkins, and lining material immediately after use.