Do crocodilians get the flu? Looking for influenza A in captive crocodilians

It is well established that several wild aquatic bird species serve as reservoirs for the influenza A virus. It has also been shown that the influenza A virus can be transmitted to mammalian species such as tigers and domestic cats and dogs through ingestion of infected birds. Another group of animals that should also be considered as potential hosts for the influenza A virus are the crocodilians. Many crocodilian species share aquatic environments with wild birds that are known to harbor influenza viruses. In addition, many large crocodilians utilize birds as a significant food source. Given these factors in addition to the close taxonomic proximity of aves to the crocodilians, it is feasible to ask whether crocodilian species may also harbor the influenza A virus. Here we analyzed 37 captive crocodilians from two locations in Florida (plus 5 wild bird fecal-samples from their habitat) to detect the presence of influenza A virus. Several sample types were examined. Real-time RT-PCR tests targeting the influenza A matrix gene were positive for four individual crocodilians--Alligator sinensis, Paleosuchus trigonatus, Caiman latirostris and Crocodylus niloticus. Of the seven serum samples tested with the avian influenza virus agar gel immunodiffusion assay, three showed a nonspecific reaction to the avian influenza virus antigen-A. sinensis, P. trigonatus and C. niloticus (C. latirostris was not tested). Viable virus could not be recovered from RT-PCR-positive samples, although this is consistent with previous attempts at viral isolation in embryonated chicken eggs with crocodilian viruses.