Controller-approved source entry - manual-review caution required Ovine/Caprine Infectious Disease Manual reviewFlock biosecurity

Ovine and Caprine Caseous Lymphadenitis

Recognize chronic lymph-node abscess disease and choose flock-level biosecurity, diagnosis, and control instead of casual drainage.

⏱ 6-7 min read · Topic of

Practice Qs

Traps

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Study step

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Overview

Caseous lymphadenitis is chronic Corynebacterium pseudotuberculosis infection with external lymph-node abscesses or internal wasting disease.

Signalment / Epidemiology

Sheep and goats acquire infection through wounds, shearing, equipment, contaminated environment, and draining abscesses.

Pathophysiology

The organism survives within abscesses and spreads through drainage, fomites, wounds, and chronic internal lesions.

Clinical Signs

Firm peripheral lymph-node abscesses, draining thick material, poor production, weight loss, or chronic ill thrift are typical.

Diagnostics

Culture purulent material from an intact or properly controlled active lesion; interpret serology with age, vaccination, and flock history.

Differential Diagnoses

Separate CL from tooth-root abscess, injection-site abscess, Trueperella or mixed bacterial abscess, Johne disease, parasitism, and small-ruminant lentivirus.

Treatment

Prioritize isolation, culture, controlled drainage only where contamination can be contained, culling decisions, and flock-level prevention.

Prognosis

External lesions can be contained, but internal CL, chronic shedders, and endemic environmental contamination make eradication difficult.

NAVLE Pearls

A draining lymph-node abscess is a flock biosecurity and zoonotic-handling problem, not just an individual animal lesion.

Common NAVLE Traps

Do not lance abscesses in shared spaces, overtrust one serology result, vaccinate clean herds reflexively, or ignore species-specific vaccine labels.

Core decision

Isolate, culture, contain drainage, protect handlers, and decide whether the flock-control answer is segregation, culling, quarantine, or vaccination.

High-yield takeaways

Start with the safest next step, then narrow the case using signalment, timeline, exam findings, diagnostics, and response to treatment.
Use the traps, differentials, and practice questions to rehearse NAVLE-style reasoning instead of memorizing isolated facts.
This educational study page is not a clinical protocol; confirm patient-specific decisions with current references and clinician judgment.

30-second revision

OverviewChronic lymph-node abscess disease in sheep and goats.

DiagnosticsCulture intact active lesion; serology needs age, vaccine, and flock context.

TreatmentIsolation, contamination control, handler protection, flock plan, often culling.

PrognosisFlock eradication is difficult after internal disease or endemic contamination.

TrapDo not lance a suspect CL abscess in shared space or use vaccine as cure.

Exam core — read this first

NAVLE pearl → Thick, nonodorous caseous pus in peripheral lymph nodes is the classic external CL clue.

Internal pearl → Chronic weight loss, poor production, cough, or ill thrift without obvious abscesses can be internal CL, especially in sheep.

Diagnostic pearl → Culture from an intact active abscess is the cleanest confirmation; serology can reflect exposure, vaccination, active disease, or timing artifacts.

Control pearl → Uncontrolled drainage contaminates facilities and equipment; casual lancing in the barn is a board trap.

Vaccine pearl → Vaccines are not 100% protective and do not clear infected animals; use only species-labeled products and flock-specific plans.

Zoonotic pearl → Purulent exudate is a handler-risk material, so PPE and controlled disposal are part of the clinical answer.

Flock Biosecurity And Handler Safety

Protect handlers and prevent contamination during abscess handling

CL exudate has zoonotic potential and can contaminate facilities, clothing, shears, needles, and handling equipment. Use PPE, isolation, controlled disposal, and veterinarian-directed flock biosecurity.

Pattern recognition

Core pattern

adult goat or sheep with firm lymph-node swelling that becomes abscessedthick white-green caseous pus from a peripheral nodechronic weight loss or ill thrift with possible internal abscess diseasehistory of shearing, equipment sharing, abscess drainage, or new animal introductionquestion asks whether to lance, isolate, culture, cull, vaccinate, quarantine, or manage flock risk

Supporting clues

species and external versus internal formabscess location and drainage statusculture result from intact or controlled active lesionflock prevalence and replacement sourcingserology timing, vaccination status, and age of animalcontamination risk in shearing or handling areas

NAVLE trigger: The exam trigger is chronic abscess plus flock-control reasoning, not simple wound drainage.

Decision core — what NAVLE actually asks

Draining or mature abscess

Isolate, protect handlers, contain exudate, and culture appropriately; do not open it in a shared barn or shearing area.

Chronic wasting without external abscess

Keep internal CL on the differential and pair imaging, culture opportunities, serology, and exclusion of Johne disease, parasites, and dental disease.

Flock control decision

Use closed-herd discipline, quarantine, equipment disinfection, segregation, and culling strategy before thinking individual cure.

Vaccination question

Check species label and flock status; vaccination can reduce prevalence but does not clear infected animals and is not a clean-herd reflex.

Key interpretation

Caseous pus

CL anchor

Thick nonodorous material from a lymph node is highly suggestive.

Culture

Definitive test

Purulent material from an intact active lesion confirms C pseudotuberculosis.

Serology

Context test

Positive titers may reflect exposure, vaccination, active lesions, or recent infection; early and walled-off disease can mislead.

Internal abscesses

Hidden disease

Chronic ill thrift can occur without visible external lesions.

Vaccine label

Species boundary

Use only species-labeled products and do not expect vaccination to clear infected animals.

Purulent exudate

Zoonotic caution

Protect handlers and prevent environmental contamination.

Use current small-ruminant references for vaccination, antimicrobial use, culling, and flock eradication strategy.

Management and treatment

Immediate control

Isolate animals with draining or mature abscesses, use PPE, contain exudate, and prevent contamination of barns, shearing areas, and equipment.

Environmental containment is the immediate board move.

Diagnostics

Culture active lesions when possible; use serology, imaging, and chronic-wasting differentials to support flock decisions.

Diagnosis should change control, not just label the animal.

Flock management

Use quarantine, closed-herd sourcing, equipment disinfection, needle hygiene, replacement screening, segregation, vaccination where appropriate, and culling strategy.

Control is a long-term flock plan.

When treatment changes

Controlled drainage may be considered only where the animal can be isolated in a disinfectable area and drainage material is collected and disposed of safely.

Casual lancing is the exam mistake.

Prognosis

Guarded for eradication in established flocks; worse with internal disease, chronic shedders, high prevalence, or uncontrolled shearing/equipment spread.

Recurrence and contamination are common concerns.

NAVLE traps — where students lose marks

Lancing in the barn aisle

Draining material can heavily contaminate the environment and expose the flock.

Calling it a simple wound abscess

Peripheral lymph-node location and caseous material point to CL.

Ignoring internal CL

Weight loss and ill thrift may occur without visible external abscesses.

Overpromising cure

Treatment is difficult and flock persistence is common.

Skipping culture

Culture of active lesions is the definitive diagnostic route.

Forgetting equipment spread

Needles, shears, tagging tools, and handling equipment can transmit infection.

Overtrusting one serology result

Titers depend on exposure timing, vaccination, maternal antibody, and chronic walled-off lesions.

Using vaccine as eradication

Vaccination can reduce disease pressure but does not clear infected animals and must follow species label.

Differentials — how to separate these on NAVLE

NAVLE discriminator: a chronic small-ruminant lymph-node abscess is a flock biosecurity and handler-safety problem until proven otherwise.

Differential	Key clue	Decision bias	Trap
Caseous lymphadenitis	Peripheral lymph-node abscess, thick caseous pus, flock history	Isolation, culture, flock control	Casual drainage
Trueperella or mixed bacterial abscess	Wound-related abscess not centered on classic nodes, different odor or character	Culture and local wound management	Assuming all abscesses are CL
Johne disease or parasitism	Weight loss, diarrhea, parasite evidence, or poor dentition without node abscess pattern	GI/herd diagnostics	Missing internal CL in wasting sheep
Small ruminant lentivirus	Chronic wasting, pneumonia, mastitis, arthritis, or neurologic signs without caseous node lesions	Flock testing and chronic disease workup	Attributing every thin ewe to CL
Tooth-root or injection-site abscess	Local anatomy or injection history, not classic lymph-node distribution	Culture and source-specific management	Missing CL when flock pattern exists
Neoplasia	Firm mass, atypical cytology, older animal, nonpurulent lesion	Cytology/biopsy pathway	Not sampling atypical masses

Practice questions

Practice small-ruminant CL recognition and flock-control decisions

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Q1Classic diagnosis

Several adult goats have recurrent prescapular and mandibular lymph-node abscesses containing thick nonodorous caseous material. What is the most likely diagnosis?

Q2Control trap

A goat has a mature draining abscess suspected to be CL. What is the safest first flock-control principle?

Q3Serology trap

A young replacement goat from a CL-vaccinated flock has a positive CL serology result but no abscess. What is the best interpretation?