VMC 311: Systematic Veterinary Bacteriology and Mycology (2+1)

DIAGNOSIS

Diagnosis

• Laboratory tests used in the diagnosis of epizootic lymphangitis include isolation of the causative agent by culture and tests for the presence of antibodies in the blood.
• Haemalological picture showed leucocytosis, neutrophilia and an increase in the erythrocyte sedimentation rates.
• Direct smear examination and culture technique
  • Diagnosis is usually based upon demonstration of the typical yeast-like, double-contoured cells in pus collected aseptically from the lesion and confirmed by culturing the pathogen.
  • H. farciminosum is a Gram-positive organism and is successfully cultivated on a vanety of media.
  • Growth is relatively slow; most isolates require from four to eight weeks for development of characteristic colonies.
• Serological tests
  • In the absence of positive culture of H. farciminosum, a presumptive diagnosis is usually made, based on the presence of antibodies in the serum.
  • Although several serological tests have been used for the diagnosis of epizootic lymphangitis, none of the tests are sufficiently sensitive or specific to confirm diagnosis.
  • The four serological tests such as FAT, AGID, ELISA and serum agglutination are relevant.
• Electron microscopic examination
  • Tissues taken from cutaneous lesions revealed the presence of oval bodies.
  • Most of the details of the fine internal structures could be observed.
• Animal inoculation
  • Experimental transmission of H. farciminosum has been attempted in mice, guinea-pigs and rabbits.
  • Imnunosuppressed mice were highly susceptible to experimental infection and can be used for diagnostic purposes.
  • Intra dermal test
  • An accurate and reliable method of skin testing is the intradermal test.
  • This consists of intradermal injection of 0.1 ml of soluble antigen prepared from H. farciminosum.
  • An increase in the thickness of the skin of 8 mm to 20 mm, 24 h after injection of the antigen can be regarded as a positive result.

Differential diagnosis

• A number of diseases may be confused with epizootic lymphangitis (e.g. glanders, strangles, ulcerative lymphangitis and sporotrichosis), especially when these diseases occur under the same environmental conditions.