Avian Hepatitis E virus: Preliminary investigations in layer hens and broiler breeders

Avian Viral hepatitis E (VHE), also called Big Liver and Spleen disease (BLS) is caused by a Hepevirus of the Orthohepevirus family.  It is characterized by sudden death in laying and breeding hens, associated with an egg drop and no degradation of egg quality.  It is of recent occurrence and has been reported in only a few countries including the US, Canada, Hungary, Spain, China and Poland.  During latest years, sudden mortalities of up to 0.3% per week and drops in production of up to 12-15% have been regular reasons for consultations.  The macroscopic pathologic diagnosis was not obvious because of similarities between lesions observed on livers of VHE affected birds and those encountered in the case of hepatic steatosis, pathology with which the differential diagnosis is essential.  The lesions found generally consisted of hepatomegaly with or without the presence of steatosis. However, hepatic bleeding is constant always present with varying splenomegaly. The present work describes preliminary results of investigations carried out on several farm-cases of laying hens and breeders presenting the aforementioned clinical signs and lesions.  In addition to the epidemiological aspects and macroscopic changes observed, the investigations performed included histopathological examinations, Elisa serology carried out on sera from the affected farms, as well as specific real-time PCR testing on liver and spleen samples.  In parallel, a sero-epidemiological analysis focused on a batch of 9,255 sera harvested from layers and breeders during the years 2018 to 2020.  The preliminary results are mixed up but point out more the need to broaden the field of investigation by developing serological and molecular diagnostic tools more specific to the Moroccan epidemiological context.  This study reports the first descriptions of the disease in Morocco. 

Key words: Hepatitis E virus, Big liver and spleen, Fatty liver, anatomopathology, RT-PCR, ELISA