 AMV is a multipartite virus and is composed of 4 particles (3 bacilliform and 1 spheroidal) with a diameter of 18 nm.The genetic material of AMV consists of 3 linear single strands RNAs (RNA 1, RNA 2 and RNA 3) and a subgenomic RNA (RNA 4) which is obtained by transcription of the negative- sense strand of RNA 3.RNA 1 and 2 encode proteins needed for replication.