Epizootic lymphangitis (pseudo-glanders) is a chronic, insidious and highly contagious fungal disease of equines particularly horse and very rarely of cattle and man. It is caused by Histoplasma farcimininosum. Clinically, the disease is manifested by suppurative lymphangitis, lymphadenitis, ulcers of the skin, pneumonia, conjunctivitis and keratitis. The disease is of great economic importance as the sick animals cannot be utilized for the work. The incubation period is about 90 days and mortality rate goes up to 10-15%. Infection is transmitted directly by contact from the diseased to healthy animal or indirectly through contaminated material such as blanket, harness, grooming kit, bedding and other stable equipments. The fungus penetrates the body through subcutaneous abrasions and produces lesions at the site of entry. Experimentally, the disease can be transmitted to susceptible animals by subcutaneous or intradermal infection of pus from the lesion of diseased subject. Although stable- flies have also been reported as agents in the spread of the infection, their role as a vector in the transmission of the disease is not yet fully established.
Symptoms: The primary lesion occurs in the subcutaneous tissues and later, infection spreads by the lymphatic vessels become enlarged, thickened, and corded; and later show nodules or hard abscesses, which rupture leaving indolent ulcer. Thick, creamy, bloodstained pus is noticed from these ulcers. The affected animals show general swelling of the limb particularly hock joint. Sometimes the infection may occur in nasal mucosa which later extends to pharynx, larynx and trachea. As a result the animal shows signs of sinusitis and primary pneumonia. Bone lesion is seldom seen in epizootic lymphangitis. Ocular form of disease is more common in mules than in other species of animals. The affected animal exhibits watery discharge from one or both the eyes, swelling of the eyelids, conjunctivitis, keratitis besides button-like ulcer on the membrana nictitans. The eye becomes closed due to diffuse swelling of the eyelids.
Diagnosis: Isolation of H. farciminosum on Brain Heart Infusion medium or Sabouraud‘s agar from the infected material confirms the diagnosis. However, the demonstration of gram-positive, oval, globose, pear-shaped, yeast-like cells (2.5-3.5
µm × 22.0 - 3.0 µm) with double - walled capsule in the pus smear may help in early diagnosis. Complement - fixation test and cantaneous test are useful aids in correct diagnosis. The disease is usually confused with ulcerative lymphangitis and cutancous sporotrichosis. In the former case, pus is greenish and lesions occur about fetlock which heal quickly. In sporotrichosis the pus smear reveals cigar-shaped bodies characteristic of the disease.
Treatment and prevention: In the early stage of the disease the affected part may be surgically removed under aseptic condition, and the wound may be dressed with silver nitrate or tincture or iodine or lactic acid or iodoform. Mercuric chloride in the dosage of 30-50 ml (1: 1,000) may be tried intravenously. Daily intravenous injection of formal (5 ml diluted in 25 ml distilled water) for 15-21 days has also shown good result. The advanced cases should be destroyed, and all excreta and discharges properly disposed off. Besides, the bedding, harness, utensils and equipments should be thoroughly disinfected.