B203 - EPIZOOTIC LYMPHANGITIS

IDevice Icon

B203 - EPIZOOTIC LYMPHANGITIS

Nature of the disease
Epizootic Lymphangitis is a contagious disease of equines due to a fungus, Histoplasma capsulatum farciminosum. 
Classification
OIE, List B disease
Susceptible species
Equines, mainly horses. Rarely it can affect camels, cattle and humans.
Distribution
Currently it is reported from many African regions. However in the past it has been present in several countries from Europe, Asia, and America.
Clinical signs 
  • Initial lesions take few weeks to 3 months to appear and consists of a painless swelling and ulcer of the site of entry. The  nodule is intradermal and is freely moveable over the subcutis. Oedema progresses in the region and the nodule gradually enlarges and ultimately bursts. The surrounding tissues become hard, variably painful, and swollen. 
  • The infection spreads along lymph vessels and causes cord-like lesions, leading to diffuse and irregular involvement of an area of skin. After, a lesion initially increases in size, additional cycles of eruption and granulation lead to progressively smaller areas of ulceration. Spontaneous recovery usually occurs in 3-12 months and leave scars. 
  • Occasionally: 
    • Severe arthritis where lesions are closed to joints,
    • Conjunctivitis or keratoconjunctivitis,
    • A serous or purulent nasal discharge.
Post-mortem findings 
Rarely cause death. Lesions are confined to external tissues and lymph nodes and vessels.
Differential diagnosis 
Specimens required for diagnosis 
Swabs of pus, smears or histological sections of the lesion can be used to demonstrate presence of the fungus by coloration, culture or PCR.

Serological tests are also available and include fluorescent antibody, ELISA and passive haemagglutination tests. Antibodies can develop before the onset of symptoms.

Transmission   
The disease is transmitted by contamination of skin wounds or direct abrasions by flies or grooming objects. The fungus could survive in the soil as a saprophytic organism.
Risk of introduction   
The disease could be introduced via the importation of affected animals or contaminated husbandry material. 
Control / vaccines  
Treatment with Amphotericin B can be efficient. Killed and live vaccines exist but are not readily available.

In case of introduction, eradication of the disease should include slaughtering of infected animals and strict hygiene.

References
  • GEERING WA, FORMAN AJ, NUNN MJ, Epizootic lymphangitis In Exotic Diseases of Animals, Aust Gov Publishing Service, Canberra, 1995, p. 321-323
  • Epizootic lymphangitis, In Veterinary Medicine, Saunders, Eight ed, 1997, London p. 1167-1169
  • Office International des Epizooties, 2002