Molecular Epidemiology of Enteric Viral Infections in Poultry Flocks in Southern Germany and the First Complete Genome Sequence of Avian Sicinivirus

Enteric viral infections represent a major concern for poultry production, causing growth retardation, impaired feed conversion, and increased mortality, particularly in young birds. To investigate the involvement of RNA and DNA enteric viruses in flocks exhibiting growth problems, seven poultry farms in southern Germany, including broiler, pullet, and breeder operations, were examined for the presence of chicken astrovirus (CAstV), avian reovirus (ARV), and fowl adenovirus-1 (FAdV-1) by means of RT-PCR. All farms exhibited growth retardation, diarrhea, and enteritis-associated lesions. Histopathology revealed features of runting–stunting syndrome in most of the broiler farms and depletion of lymphatic tissue in most of the pullet farms. CAstV was detected in all flocks, ARV in six, and FAdV-1 in four farms. To further characterize the viral agents, metagenomic sequencing of cecal tonsils from one severely affected broiler flock confirmed the presence of a CAstV strain identical (100%) to CAV/Belgium/4134_001/2019. In addition, the complete genome of avian Sicinivirus was assembled for the first time in Germany, showing 96.8% nucleotide identity with a Dutch strain (Chicken/NLD/2019/V_M_056_picorna_2). These findings demonstrate the widespread circulation and co-infection of enteric viruses on German poultry farms and underline the transboundary nature of these infections, emphasizing the need for enhanced surveillance and biosecurity measures to mitigate their impact on poultry health and productivity.