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Caseous Lymphadenitis
(CL) in Goats and Sheep |
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Introduction
Caseous Lymphadenitis or CL is a highly contagious bacterial
disease that affects sheep and goats. CL is characterized
by abscess formations in the skin, internal and external lymph
nodes, and internal organs. CL is a worldwide chronic disease
in goats and sheep; however, some animals within a herd appear
to be very resistant to this disease. |
CL abscess |
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Diagnosis, Prevention
& Treatment
Corynebacterium pseudotuberculosis causes CL. Goats and sheep
can be infected by direct contact with this microorganism.
The CL bacteria can be found in the soil of contaminated pens
and pastures on feed and water troughs, and in shelters and
other congregation points. The source of contamination is
usually an abscess that has ruptured and drained onto various
surfaces. Direct contact with a ruptured abscess by herd-mates
will also spread the infectious bacteria from animal to animal.
Animals can acquire infection orally when ingesting contaminated
feed or grass. Upon infection, C. pseudotuberculosis will
multiply and spread throughout the body via the bloodstream.
Subsequently, lymph nodes and internal organs including the
lungs, kidney and liver become infected and develop abscesses.
The spinal cord can also develop CL abscesses. Once infected
the animal is considered to be a carrier for life. |
Clinical Signs
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 shoulder, or in the rear flank region.
They may also develop between the hind legs where scrotal
sac or udder attaches. Internal abscesses are detectable only
through necropsy (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. |
Diagnosis
Not all abscesses or cases of chronic weight loss in sheep
and goats are associated with CL. Diagnosis is based on clinical
signs detected by sight and by physical examination. Abscesses
range from firm to soft swelling, and some are well-defined
with rounded shapes on the surface of the animal's body. The
CL abscess typically contains pasty, thick, yellow-green pus
with a foul odor. Internal abscesses cannot be seen, except
by X-ray, biopsy, or postmortem examination. Serologic tests
are available, but their reliability is questionable. |
CL abscess as swelling on the
surface of the body |
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| When you suspect CL, you should confirm the presence
of the C. pseudotuberculosis microorganisms by submitting a
sample of the abscess content to a diagnostic lab for analysis.
If the laboratory result is positive, then CL is deemed responsible
for the abscess. |
| If you have an animal that develops an abscess: |
| Immediately isolate the animal from the herd. |
| Isolate from the herd |
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Wear surgical gloves to drain abscesses.
Use a disposable scalpel to cut the surface of the abscess and
drain it before it ruptures on its own in the field. The abscess
is about to rupture when it has lost hair. |
Incision to drain an abscess |
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| 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. |
| Completely drain the abscess |
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| Wash the resulting abscess cavity thoroughly with
hydrogen peroxide then flush it with iodine. |
Wash the abscess cavity |
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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. |
The abscess is rich in the
C. paratuburculosis microorganism. To avoid spreading the
CL microorganism, place the infected animals on a concrete
floor or other surface that will make disinfecting easier.
Clean the floor immediately with a potent disinfecting solution,
such as bleach. Always wear gloves when draining the abscess.
Other microorganisms, such as Arcano bacterium
(Actinomyces) pyogenes, entering an animal's skin the same
way the CL microorganisms enter can also cause abscesses.
Using non-sterile needles can cause infection at injection
sites. |
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Internal CL abscess in goat liver and lung |
| Preventing CL Through Management |
| There is not an effective treatment for CL. Antibiotics
are ineffective. However, certain management practices can help
to minimize the impact of CL on the herd or flock. |
Conduct routine, visual examinations
of the herd, noting the presence of abscesses. This may require
a closer inspection in wool sheep and fiber goat breeds where
long course hair or wool can hide abscesses. The same is true
of long-eared goats such as Boer and Nubian, where submandibular
abscesses can be hidden under the ears.
Avoid purchasing animals with visible abscesses or abscess
scars.
Examine males before introducing them to the doe herd. A male
with erupted abscess can contaminate the females.
Avoid giving injections in the shoulder region where an injection-site
reaction can be confused with a CL abscess.
Use a clean needle with each animal to prevent the spread
of C. paratuberculosis from asymptomatic carriers to non-infected
animals. This would be of particular concern with the use
of automatic syringes.
Always disinfect equipment such as ear taggers, tattooing
needles, hoof trimmers, or wool shears that might break the
skin of animals when used. Shearing equipment is of special
concern as a hidden abscess might be ruptured during shearing.
Cull infected animals from the herd to help reduce the risk
of CL infection.
Consider maintaining a closed herd.
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| Vaccinating Against CL |
Control of the CL disease
by vaccination remains controversial, although toxoid vaccines
are now commercially available in some countries. A vaccine
for sheep is commercially available in the United States.
This vaccine is made with killed germs and seems to be effective
in decreasing the incidence and severity of the disease in
sheep herds. However, the vaccine is not approved for use
in goats. Autogenous vaccines (vaccines made from bacteria
strains isolated from a specific herd) are another source
of available immunization in sheep and in goats. However,
a reputable certified laboratory must produce the vaccine.
Before using an autogenous vaccine, test it in several animals
for adverse side effects. Goats seem to be more sensitive
to the side effects of these types of vaccines. |
| References |
Ayres, J. L. (1977). Caseous lymphadenitis
in goats and sheep: A review of diagnosis,pathogenesis, and
immunity. Journal of the American Veterinary Medical Association,
171(12), 1251-1254.
Batey, R. G. (1986). Pathogenesis of caseous lymphadenitis
in sheep and goats. The Australian Journal of Experimental
Biology and Medical Science, 63(9), 269-272.
Cetinkaya, B., Karahan, M., Atil, E., Kalin, R., De Baere,
T., & Vaneechoutte, M.
(2002).Identification of Corynebacterium pseudotuberculosis
isolates from sheep and goats by PCR. Veterinary Microbiology,
88(1), 75-83.
Gilmour, N. J. (1990). Caseous lymphadenitis: A cause for
concern. The Veterinary Record, 126(23), 566.
Brown, C. C., Olander, H. J. & Alves, S. F. (1987). Synergistic
hemolysis-inhibition titersassociated with caseous lymphadenitis
in a slaughterhouse survey of goats and sheep in Northeastern
Brazil. Canadian Journal of Veterinary Research, 51(1), 46-49.
ter Laak, E. A., & Schreuder, B. E. (1991). Serological
diagnosis of caseous lymphadenitis ingoats and sheep. The
Veterinary Record, 128(18), 436.
Schreuder, B. E., ter Laak, E. A., & Dercksen, D. P.
(1994). Eradication of caseouslymphadenitis in sheep with
the help of a newly developed ELISA technique. TheVeterinary
Record, 135(8), 174-176.
Williamson, L. H. (2001). Caseous lymphadenitis in small
ruminants. The Veterinary Clinicsof North America: Food Animal
Practice, 17(2), 359-371, vii.
Maria Lenira Leite-Browning, DVM, Extension Animal Scientist,
Alabama A&M University. |
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