This study was conducted to determine the presence of Avian encephalomyelitis (AE) virus in Algerian laying farms from different regions of the country and analyse the economic impact of vaccination against the virus. A sentinel veterinarian observed an egg drop in 16 laying farms with 4800-130 000 hens. The capacity strains, vaccination programme, accident laying (percentage drop, and external appearance), clinical aspects, postmortem examination, and mortality rates during the egg drop were observed. Blood samples from the wing vein were collected from 15 birds per farm right at the moment of the egg drop (S1) and after three weeks of first collection (S2). A cost-benefit analysis was performed to determine the gains and losses due to vaccination against AE. Results revealed that AE-positive birds were higher in western and central regions of the country. AE caused egg drop in breeding laying hens for the duration of one to more than three weeks. It was observed that farms with less than one week egg drop duration were AE negative. Farms with egg drop duration between one and two weeks were all serologically AE positive, along with periods between two and three weeks, and even more in areas affected at more than three weeks. The clinical signs of the disease included nasal discharge, infraorbital oedema, conjunctivitis, tracheitis, and renal impairment. AE seroprevalence was very high in farms with or without clinical signs. Farms were AE positive when they had an egg drop of 5 to 15% seroprevalence. Only 57.14% of positive seroprevalence was recorded in farms with egg drop which exceeded 15%. It was noted that of 75% of the farms were not vaccinated against AE. Cost-benefit analysis revealed that farms which vaccinated against AE virus entailed less cost than farms which did not vaccinate against the disease. It is concluded that Avian enceophalomyelitis is present in Algerian laying farms and is a major cause of hen mortality and egg production drop. It is also noted that economic losses are high in farms with unvaccinated birds.