This Methodological Instruction stipulates that the method for diagnosing cattle leucosis shall be serological examination – diffusion precipitation reaction, also known as immunodiffusion reaction in agar gel. Animals infected with leucosis shall be identified from among cattle that test positive using haematological methods. Seropositive animals shall be considered infected by leucosis based on any one of the following indices: (a) positive results of a haematological examination for of leucos