Reactivation of anaconda paramyxovirus infection after 13 years of latency

From July/2011 to June/2012, 31 green anaconda (Eunectes murinus) juveniles, progeny of a female anaconda purchased from Japan and added to the Ocean Park, Hong Kong collection in May/2011, died over a 12-month period. A novel paramyxovirus, named anaconda paramyxovirus (AnaPV), which belonged to the genus Ferlavirus, was isolated. In July/2015, one of the remaining two green anacondas died at the age of four, probably a result of prolonged incubation or latency of the AnaPV infection. In May/2024, a thorough examination on the ∼25-year-old green anaconda mother revealed multiple abnormalities, including grave anemia and intra-abdominal masses. The animal died shortly afterwards. The most important necropsy findings included an enlarged and unevenly firm pancreas with black pinpoint discolorations and thickened pancreatic duct, with histopathology findings suggestive of exocrine adenocarcinoma infiltrating into the duct and adjacent tissues and metastatic to the spleen; and severe membranous chronic and diffuse glomerulonephritis and severe acute renal tubular degeneration and necrosis. RT-PCR of the 179-bp partial L gene of AnaPV for the lung sample collected from the deceased anaconda mother was positive. Sequencing results showed that the sequence of the positive band was identical to that of AnaPV we previously published. The present study showed that AnaPV was capable of reactivation and causing infection in green anaconda after more than 10 years of latency. Further molecular surveillance studies in snakes of different species, genera and families, particularly in outbreaks due to unknown causes, would be important to discover additional members of the genus Ferlavirus.