Susceptibility of domestic and other birds to coronaviruses

Everybody in the poultry industry is well aware of infectious bronchitis virus (IBV), the coronavirus of the chicken (Gallus gallus), associated with respiratory disease, but also with disorders of the reproductive and urogenitory systems. US turkey producers are familiar with coronavirus disease (enteric) in turkeys (Meleagris gallopavo), the rest of the world much less so. Studies in the UK have demonstrated that pheasants (Phasianus colchicus) are commonly infected with a coronavirus (respiratory and kidney disease). Very recently scientists in China have isolated coronaviruses from peafowl (Pavo), guinea fowl (Numida meleagris); also in Brasil), partridge (Alectoris) and also from a non-gallinaceous bird, the teal (Anas). All these coronavirus are closely related in genome organisation and, indeed, in gene sequence, to IBV, the prototype virus of the Group 3 coronaviruses. To date this group only contains viruses isolated from birds. Most recently Group 3 coronaviruses have been detected in greylag geese (Anser anser), mallard duck (Anas platyrhynchos) and pigeon (Columbia livia). In my lecture I shall be looking at what we know biologically about these coronaviruses, in the context of host range and interspecies transmission. Twenty years ago a coronavirus was isolated from a shearwater (Puffinus puffinus). This virus was genetically similar to the Group 2 coronaviruses, which up to that point comprised only viruses from mammals. Whilst it is not certain whether that virus was actually from the shearwaters or from the mice that had been inoculated with material from the shearwaters, recent experiments with bovine coronavirus have demonstrated that the bovine virus can not only infect but can also cause enteric disease in turkeys. In other words, birds are not necessarily limited to infection by coronaviruses that we would consider to be avian coronaviruses. Host range studies amongst Group 1 coronaviruses (all from mammals, to date) are very instructive in this regard as, of course, is SARS coronavirus. Clearly there is the potential for the emergence of new coronaviruses diseases in domestic birds, from both avian and mammalian sources. I shall discuss briefly how laboratory diagnosticians might be prepared for such an event.