Ulcerative Lymphangitis:

Synonym: Ulcerative cellulitis, Caseous lymphadenitis

• It is an infectious disease of cattle and horse characterized by formation of skin ulcers with involvement of lymph vessels of lower limbs.

Etiology:

• Corneybacterium pseudotuberculosis
• Pleomorphic, non-motile, non-spore forming, non-capsulated gram+ve rod
• Corneybacterium equi and Pseudomonas aeruginosa have also been isolated from lesion.

Epidemiology:

• Disease is worldwide in distribution.
• It is primarily disease of horse but has also been recorded in cattle.
• The disease is more common in tropical and subtropical regions with hot, humid conditions.
• Pectoral, ventral midline, abdominal and inguinal abscesses are frequent presentations in areas of the western USA, whereas ulcerative lymphangitis is more typical elsewhere.
• The incidence of disease varies from year to year, and outbreaks can occur.
• Common names for the abscess form of the disease are “pigeon fever”, “pigeon breast”, “dry-land distemper” or “Colorado distemper”.
• Disease is usually associated with poor sanitation. Open draining tracts can be source of environmental contamination.

Pathogenesis

Clinical Findings:

• Typical abscess formation occurs most commonly in pectoral region and occasionally in abdomen along ventral midline or in inguinal region.
• Abscess are often thick walled
• Ventral or inguinal edema can be seen in association with abscess.
• Depression, fever and anorexia may be present but are atypical.
• Diffuse swelling on one or both limbs causing lameness.
• Nodules formed on the legs break down leading to the formation of ulcers.
• Thick greenish exudates mixed with blood appear from such ulcers.
• Lymphatics draining the area may become enlarged and firm.

PM Findings:

• Lesion usually heals up in one week.
• Thick walled abscess are typical PM findings
• Abscess contain tan colored liquid exudate whereas pustules may contain whitish-green pus.
• Abscess are identified along lymphatics in peripheral limbs.

Diagnosis:

• Based on history, clinical findings
• Examination of blood: Elevation in WBC, RBC normal in chronically diseased animals.
• Isolation and identification of organism through bacterial culture.
• USG are helpful in identifying deep abscess in abdominal or axillary regions.
• PCR testing of abdominal fluid for C pseudotuberculosis

Differential Diagnosis:

1. Pyoderma, abscess or lymphangitis due to other bacteria.

• Lesion is localized
• It is usually caused due to Staphylococcus or Streptococcus

2. Dermatophytosis:

• Circular patches of alopecia with scaly, crusty margin
• They are usually dry not purulent
• Lesion are found in face, neck, trunk, saddle area; not confined to lymphatics.

3. Sporotrichosis:

• Discharge are less purulent than ulcerative lymphangitis.
• Lesion may appear on limbs, head, tail base; not limited to lower limbs
• Cytology or histopathology shows cigar-shaped yeast forms; culture on SDA
• It is caused by fungi.

4. Onchocerciasis:

• Firm, non-painful subcutaneous nodules (onchocercomas) containing adult worms.
• Pruritus, alopecia, dermatitis—especially along ventral midline, chest, neck, face, or withers.
• Lesions may be dry or exudative if secondarily infected, but not organized along lymphatics.
• Ocular involvement possible (iritis, keratitis).

Treatment:

• Surgical incision into and open drainage of abscess is often required.
• Daily flushing and local therapy may be required to maintain open drainage.
• Procaine benzylpenicillin (20 000 IU/kg IM b.i.d.), potassium penicillin (20 000–40 000 IU/kg IV q.i.d.) and sulfa-trimethoprim (5 mg/kg of the trimethoprim portion b.i.d.) are commonly used.
• Rifampicin (5 mg/kg PO b.i.d.) and erythromycin (20–30 mg/kg PO q.i.d.) have also been recommended for treatment.
• Ulcers are to be treated with antiseptic solution.
• Analgesic and anti-inflammatory drugs; flunixin meglumine @1.1 mg/kg, IM may be used to reduce pain.

Control Measures:

• All contaminated materials should be properly disinfected or disposed.
• Good hygiene is to be maintained.
• No vaccine is available for the disease.
• Quarantine or culling of infected horses reduces environmental contamination.
• Fly control and the use of screened stalls may reduce insect vector spread.
• Preventing skin abrasions from tack or harness is useful.