An 8-week-old hand-reared sloth bear at Smithsonian’s National Zoo in Washington DC presented with respiratory signs in February 2014. Nasal swabs were tested for influenza A virus (IAV) by rRT-PCR and virus isolation. IAV viral RNA was detected and subtype H1N1 was isolated. Sequence analysis confirmed pandemic (H1N1) 2009 lineage which has zoonotic potential.
Within one month prior to the onset of respiratory signs in the cub, several of its caretakers developed influenza-like illness and subsequently the juvenile and adult sloth bears housed separately in the same building developed signs of respiratory disease. Human-to-bear transmission of the H1N1 virus, concurrently circulating in the human population, was strongly suspected. Bear-to-bear or bear-to-human transmission could not be confirmed. The cub was treated with supportive care and respiratory signs resolved within two weeks.
Additional nasal swabs and serum from the cub and banked sera from six other collection sloth bears dating back to 2002 were tested. Serologic evidence revealed introduction of H3N2 IAV (also a predominant subtype in humans) into the sloth bear collection prior to this 2014 introduction of H1N1.
The influenza A pandemic (H1N1) 2009 virus has demonstrated infectivity in a broad array of domesticated species as well as black-footed ferrets, skunks, cheetah, giant anteater, badger, binturong and giant pandas. In many of these exotic species, infection was suspected to have been transmitted from human caretakers, suggesting that revised biosecurity measures be considered to protect human and animal health and to minimize opportunities for development of new reservoir species and subsequent emergence of novel strains. This is the first report of infection in sloth bears, listed in Appendix I of CITES and as vulnerable and decreasing by the IUCN primarily due to habitat loss and poaching.