CASEOUS LYMPHADENITIS
(CL)
Pseudotuberculosis or cheesy glands.
Definition

It is a chronic debilitating infectious disease of
sheep and goats, caused by corynebacterium
pseudotuberculosis, characterized by
suppurating, necrotizing inflammation of one or
more lymph nodes (abscessation of lymph
node).
Etiology
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Corynebacterium (C) pseudotuberculosis is the specific cause
of the disease. There are two proposed biotypes,
ovine/caprine and equine/bovine.
Variation in toxin production between strains may be
related to differences in pathogenicity.
C. pseudotuberculosis is intracellular, Gram positive,
polymorphic rods, coccoid to filamentous, non-acid fast,
aerobic to facultative anaerobic.
It grow on blood agar giving pin point colonies of white or
creamy-opaque, flat of matted surface with narrow zone of
hemolysis within 1-2 days of incubation.
Predisposing factors

Dirty condition at shearing time, faulty shearing,
dipping where the organism still lives for 24 h in
sheep dip, abrasions, wounds from fighting or grass
seeds.
Epidemiology


Distribution: Caseous lymphadenitis occurs in the
major sheep-producing countries in the world
including Australia, New Zealand, South Africa, the
Middle East including Egypt
Animal susceptibility: Sheep and goats of all ages
but adults are more affected than young because
repeated exposure to infection at shearing. CL is
more serious in goats than in sheep.
Epidemiology
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Mode of infection:
Source of infection: The discharges from ruptured
abscessed superficial lymph nodes and the nasal and
oral secretions from animals with pulmonary abscesses
draining into the bronchial tree. It contaminated
shearing tools, dipping fluid, contaminated soils or
contaminated surgical tools.
Mode of transmission:
Infection of an animal is facilitated by the presence of skin
wounds but the organism can invade through intact skin.
 Transmission is by direct contact with infective discharges or
mediated by contaminated shearing equipment,
contaminated shearing shed boards or holding pens,
contaminated dipping or shower fluids, or dust from
contaminated shearing sheds and yards.

Pathogenesis

After infection, the organism is drain to local lymph nodes (within
leukocytes),


it multiply resulting in inflammation and multiple abscess formation which
coalesce with each other and undergo encapsulation, the infected lymph
node become consists of central necrotic mass of ct in the center surround by
capsule from ct, inflammatory cells, the cells of inner layer of connective
tissue capsule is killed by bacterial toxins and thus add a new layer of
suppuration to the central necrotic mass and a new capsule, these process
repeated resulting in onion ring appearance of the lesion.
Blood born infection results in septicemia of lambs or abscess
formation in adults in many organs as lung, liver, kidney, brain and
spinal cord without appearance of lymphadenitis of superficial lymph
nodes as in "Thin ewe syndrome" which is diagnosed in slaughter
house.
Clinical signs


IP is unknown naturally (long up to 90 d), MB may
be high in sheep (15-70%), Mt rate is low and
course of the disease is long.
Sheep
 Superficial
form: There is palpable enlargement of one
or more of the superficial lymph nodes (commonly
affected are the submaxillary, prescapular, prefemoral
and supramammary).
 The
abscesses commonly rupture and thick green to
caseated pus, with no odor, is discharged and onion-like
which is soft firstly and then become dried later.
Clinical signs

Internal or Visceral form: In cases in which systemic
involvement occurs, chronic pneumonia, pyelonephritis,
ataxia. The debilitating disease of adult ewes
commonly referred to as 'thin ewe syndrome' is often
associated with the occurrence of internal abscesses.
 In
ewes, local spread from the supramammary lymph node
to the mammary tissue is common. The resulting fall in milk
yields leads to poor growth and even death of lambs and
this may be a serious economic feature in badly affected
flocks.
Clinical signs
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Goat:
Abscess or scar tissue from
healed abscess may be
present under ears,
superficial lymph nodes is
enlarged (common
affected lymph nodes is
parotid), abscessate and
may discharge greenish
creamy pus
Postmortem lesions:
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Carcass is emaciated, caseous abscess filled with greenish
yellow pus chiefly in lymph nodes, in early stage pus is soft
and pasty but later on become firm dry and characteristic
laminated or onion-ring like appearance with layers of
caseous materials separated by fibrous band on incision
Abscess formation to lesser extent in internal organs as lung.
Diagnosis

Field diagnosis: It depends on clinical signs as
suppurative lymphadenitis of superficial lymph
nodes especially after shearing, docking, castration
beside postmortem lesions, epidemiology of the
disease and field allergic skin test.
Laboratory diagnosis:
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Samples: Pus, biopsy of lymph nodes, parts of lymph nodes,
blood and serum.
Laboratory procedures:
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Examination of pus smears after staining with Gram stain to detect
Gram positive, polymorphic rods organism.
Culture on blood agar, incubation for 1-2 days at 37 C, colony
appear as small pin point and off-white faintly hemolysis.
Detection of toxins by inoculation of suspected materials I/D into
rabbits, resulting in dermal necrosis. G. Pig inoculation I/V by pus,
death after 4-10 days, with absecessation of lung and liver while
I/P injection produce orchitis with abscess formation.
Detection of antitoxins by IHT, ELISA, CFT or agglutination tests.
Hematological and serum biochemical analysis.
Treatment:
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The treatment is not satisfactory due to suppuration
and cell wall lipids of organism.
The C. pseudotuberculosis is susceptible to many
antibiotics in vitro as pencillin, oxytetracyclin 10
mg/kg or procaine pencillin 22.000 IU/kg for 3-5
days.
Surgical treatment, complete evacuation of pus and
washing with antiseptic or total extraction of the
infected nodes
Control:
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Proper management:
 Isolation and culling of infected sheep.
 Sanitary care during shearing, castration or docking and use
skin disinfection and disinfection of surgical instrument.
 Avoid contamination of dipping fluids so, dipping of lamb
firstly, and then adult due to decrease chance of lamb
infection.
Vaccination:
 Immunization of goats or lambs with killed whole organism or
with toxoid may helpful in limiting infection, sheep of one
month age vaccinated by BCG show decrease incidence of
the disease. There is no a available vaccine produced and
used in Egypt.