Caffy et al. identified man’s best friend, dogs (sorry for all those cat lovers), as a possible source of human norovirus. The UK-based-researcher showed that different genotypes of human norovirus-like particles can bind to canine gastrointestinal tissue, suggesting that infection is (theoretically) possible. In addition, some of the dogs mounted an immune response to human norovirus.
How much of a problem do we actually have? Time to let Bella & Buster go?
In my opinion this seems still to be unclear. Neither do we know whether dogs could shed human norovirus in quantities necessary to cause infections in humans, nor (and most importantly) did the researchers succeed to detected human norovirus in the canine feces samples. Thus, so far no reason to switch your best friend with a gold fish – which, by the way, might carry the risk of atypical mycobacteria!
Evidence for human norovirus infection of dogs
Human noroviruses (HuNoVs) are a major cause of viral gastroenteritis, with an estimated 3 million cases per year in the United Kingdom. HuNoVs have recently been isolated from pet dogs in Europe (M. Summa, C.-H. von Bonsdorff, and L. Maunula, J Clin Virol 53:244-247, 2012, http://dx.doi.org/10.1016/j.jcv.2011.12.014), raising concerns about potential zoonotic infections. With 31% of United Kingdom households owning a dog, this could prove to be an important transmission route. To examine this risk, canine tissues were studied for their ability to bind to HuNoV in vitro. In addition, canine stool samples were analyzed for the presence of viral nucleic acid, and canine serum samples were tested for the presence of anti-HuNoV antibodies. The results showed that seven different genotypes of HuNoV virus-like particles (VLPs) can bind to canine gastrointestinal tissue, suggesting that infection is at least theoretically possible. Although HuNoV RNA was not identified in stool samples from 248 dogs, serological evidence of previous exposure to HuNoV was obtained in 43/325 canine serum samples. Remarkably, canine seroprevalence for different HuNoV genotypes mirrored the seroprevalence in the human population. Though entry and replication within cells have not been demonstrated, the canine serological data indicate that dogs produce an immune response to HuNoV, implying productive infection. In conclusion, this study reveals zoonotic implications for HuNoV, and to elucidate the significance of this finding, further epidemiological and molecular investigations will be essential.