Avian influenza, migratory birds and emerging zoonoses: Unusual viral RNA, enteropathogens and Cryptosporidium in poultry litter

The last decade has witnessed the emergence of several new viral infectious agents, most notably avian influenza H5N1, SARS and West Nile Virus. The emergence of these agents is heavily associated with zonotic animal hosts, as well as migratory pathways of infected bird vectors. The environmental survival and persistence of nucleic acid associated with these viral agents may be important for both the detection as well as the occurrence of related diseases. Our hypothesis suggests that nucleic acid from such emerging viruses may enter into a virus-parasite surrogate relationship to aid in viral persistence. We suggest that Cryptosporidium and other gastrointestinal parasites, including Giardia, could be a) a reservoir of genetic material and a environment where assortment between that genetic variation can occur and, b) a source of zoonoses through infection of the ‘target’ animal (including humans). One example which illustrates this may be the uptake dsRNA from rotavirus into cryptosporidial oocysts, as this parasite has previously been shown to contain dsRNA viral-like particles. The importance of such a surrogate relationship is discussed and its implications for human and animal health highlighted.