New insights on Avian orthoreovirus and Chicken astrovirus co-infection in an Italian broiler flock: preliminary biomolecular and pathological results.

Common pathogens of intensive poultry farms, either parasitic or bacterial, such as Coccidiaor Salmonella, are well known and strictly controlled by veterinary management. This case study reports an unusual case of runting stunting syndrome (RSS) observed on a Sicilian poultry farm of broiler chickens during 2019. The investigation was carried out on five chickens which present delayed in body weight and growth performance. Animals showed also difficulty in deambulation and diarrhea. At necropsy, intestinal lesions were detected in three of the five clinical cases. Gut samples were collected and analyzed to identify potential pathogens responsible for the RSS. Presence of viruses was detected by using quantitative reverse transcription PCR (RT­qPCR), while selected tissues were fixed and embedded in paraffin wax according to routine procedures. All histological sections were stained with hematoxylin­eosin. RT­qPCR successfully detected both Chicken astrovirus (CAstV) and Avian orthoreovirus (ARV). Histology evidenced severe specific lesions on the intestinal mucosa in liver and kidneys. Chicken astrovirus and Avian orthoreovirus RNA was also detected in cecal tonsils, kidney and liver, thus implying their possible primary role in inducing the disease. Further studies are needed to evaluate the role of other possible factors (low biosecurity measures, e.g.) and, most of all, the consequences in terms of economic losses and animal health impairment.