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

item Spackman, Erica

Submitted to: Journal of Experimental Zoology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2008
Publication Date: 5/16/2008
Citation: Davis, L.M., Spackman, E. 2008. Do crocodilians get the flu? Looking for influenza A in captive crocodilians. Journal of Experimental Zoology. 309A:571-580.

Interpretive Summary: Since crocodiles eat and share habitats with wild waterfowl and shore birds there is a possibility that they are exposed to the low pathogenicity avian influenza viruses (LPAIV) sometimes carried by these species. In this study blood, serum, and cloacal swab samples were collected from 37 captive crocodiles representing 14 species from two locations in Florida. The specimens were tested for avian influenza virus genetic material and live virus with standard methods and the serum was tested for antibodies to the virus with a standard antibody test. Although no live virus was recovered and antibodies to avian influenza virus could not be detected, four specimens from four species of crocodile tested positive for avian influenza virus genetic material.

Technical Abstract: 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 is the crocodilians. Many crocodilian species share aquatic environments with wild birds that are known to harbor influenza viruses. Also, 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 4 individual crocodilians — Alligator sinensis, Paleosuchus trigonatus, Crocodylus latirostris and Crocodylus niloticus. Of seven serum samples tested with the avian influenza virus agar gel immunodiffusion (AGID) assay, three showed a non-specific reaction to the avian influenza virus antigen— Alligator sinensis, Paleosuchus trigonatus and Crocodylus niloticus (Crocodylus 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.