A retrospective study (1998-2013) of avian lympho-proliferative diseases in Morocco

The objective of this work was to depict the situation about avian neoplastic diseases that occurred in Morocco and to highlight different episodes of their occurrence from 1998 to 2013. It was based on field cases and data collected at the Unit of Histology and Veterinary Pathology of the Veterinary Teaching Hospital at Hassan 2^nd Institute of Agronomy and Veterinary Medicine, Rabat and those provided by 3 veterinary poultry practitioners. A total of 189 cases (1 case = 1 affected flock) during the period of 1998 to 2013 were investigated. The results showed that neoplastic diseases were still encountered during the study period. Among these, Marek’s disease (MD) represented 90% of the total cases studied, of which 37% was diagnosed within the period 2004-2006. However, leukosis/sarcoma tumors constituted only 10% of the cases that all were diagnosed between 1998 and 2000, and one case of myxosarcoma in 2008. MD was more common in laying hens (69% of cases) than in breeders (31% of cases) and affected more frequently the 19-36 week-age group in both breeders and laying hens with 67% and 58% of cases, respectively. The most prevalent clinical form of MD disease was the visceral form alone (20% of cases) or associated with the nervous and cutaneous forms (72% of cases). The nervous form alone (classical form) occurred only in 8% of cases. Among diagnosed leucosis/sarcoma tumors, myeloid leucosis represented 69% (13/19) from which 11/13 cases were myeloblastosis and 2/13 cases were myelocytomas. The other 21% of tumors were erythroid leucosis and myxosarcoma. These tumors were observed in broiler breeders (74% of cases), layers (21% of cases) and broilers (5% of cases). In broiler breeders, the age of affected birds was from 17 to 50 weeks with a mean age of tumor appearance of 31 weeks while in layers, this mean age was 27 weeks.

Key words: avian neoplastic diseases, Marek’s disease, leukosis/sarcoma group, Morocco