Pox in Other Avian Species
Infections with avian poxvirus have been seen in a variety of wild and pet birds. Some isolates are primarily infectious for only the homologous host, whereas others are infectious for one or more additional species. In the absence of genetic information on most of these viruses, classification has usually been based on host pathogenicity or cross-protection studies. The nucleotide sequence of canarypox virus genome has been determined. Canarypox virus infection is usually severe, and mortality sometimes approaches 100%. Cutaneous lesions may develop, as may systemic infection with cytoplasmic inclusion bodies detected in lesions on histologic examination. A commercial vaccine for canaries is available in the USA. Poxvirus infection in psittacines may also be severe, especially in blue-fronted Amazon parrots. Poxviruses isolated from psittacines appear to be antigenically different from poxviruses of other avian species.
Genomic profiles of canarypox, mynahpox, and quailpox viruses show marked differences from fowlpox virus when their DNA is compared by restriction fragment length polymorphism after restriction endonuclease digestion. Quailpox virus shows marked antigenic differences from fowlpox virus and, although some cross-reacting antigens are present, provides limited or no cross-protection against fowlpox virus. Avianpox virus infection has been considered as a population-limiting factor in endangered Hawaiian forest birds. Avianpox viruses isolated from Hawaiian crows (Corvus hawaiiansis), Hawaiian geese (Branta sandvicensis), Palila (Loxiodes bailleui), and Apapane species (Himatione sanguinea) are different from each other and from fowlpox virus. Similarly, a poxvirus isolated from an Andean condor (Vultur gryphus) at the San Diego Zoo is antigenically, genetically, and biologically different from fowlpox virus. Like fowlpox virus, these viruses appear to be suitable vectors for expression of foreign genes toward development of genetically modified virus vaccines for mammalian species. Several canarypox virus vectored vaccines expressing genes of mammalian pathogens are available commercially.