VMC 221: Veterinary Immunology and Serology (1+1)

JOHNIN REACTION

• Animals infected with Mycobacterium avium var. paratuberculosis may develop a delayed hypersensitivity reaction following intradermal inoculation of an extract of this organism called johnin.
• But negative results are obtained in clinical infection. In such cases, intravenous johnin test is done.
• Johnin given intravenously and temperature noted at intervals.
• A rise in temperature of 1 ° C or a neutrophilia after 6 hours is considered positive.
• This test is used for identification of infected herds.