Other than fowlpox in chickens and turkeys, infections with avian poxviruses have been observed in a variety of wild and pet birds, including songbird, mynah, quail, condor, flamingo, pigeon, junco, penguin, sparrow, starling, and psittacine species. Avian poxvirus infection has been considered a population-limiting factor in endangered Hawaiian forest birds.
Several canarypox virus–vectored vaccines expressing genes of mammalian pathogens are available commercially.
Etiology of Poxviral Infections in Birds Other Than Chickens and Turkeys
Avian pox is caused by viruses of the genus Avipoxvirus in the family Poxviridae. The fowlpox virus is the prototypical virus of the genus.
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.
Genomic profiles of canarypox, mynahpox, and quailpox viruses show marked differences from fowlpox virus when their DNA is compared by restriction fragment length polymorphism (RFLP) after restriction endonuclease digestion. Quailpox virus shows marked antigenic differences from fowlpox virus and, although some cross-reacting antigens are present, antibodies against quailpox virus provide limited or no cross-protection against fowlpox virus.
Poxviruses isolated from psittacines appear to be antigenically different from poxviruses of other avian species.
Avian poxviruses isolated from Hawaiian crows (Corvus hawaiiensis), Hawaiian geese (Branta sandvicensis), palila (Loxioides 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.
These viruses have higher genome size than the fowlpox virus genome and show more genetic similarity to canarypox virus than fowlpox virus. Like fowlpox virus, these viruses appear to be suitable vectors for expression of foreign genes toward development of genetically modified live virus vaccines for mammalian species.
Epidemiology of Poxviral Infections in Birds Other Than Chickens and Turkeys
Morbidity and Mortality: Canarypox virus infection is usually associated with severe morbidity. Mortality rates sometimes approach 100%.
Host Range: Some isolates are primarily infectious for only the homologous host, whereas others are infectious for one or more additional species.
Clinical Findings of Poxviral Infections in Birds Other Than Chickens and Turkeys
Cutaneous lesions may develop in avipoxviral infections, as may systemic infection. Canarypox virus infection is usually severe. Poxvirus infection in psittacines may also be severe, especially in blue-fronted Amazon parrots.
Courtesy of Dr. Deoki Tripathy.
Diagnosis of Poxviral Infections in Birds Other Than Chickens and Turkeys
Courtesy of Dr. Deoki Tripathy.
A presumptive diagnosis of avian poxviral infection can be made based on characteristic skin lesions. Diagnosis should be confirmed by means of laboratory testing. Cytoplasmic inclusion bodies may be detected in lesions on histologic examination. Strains can be differentiated on the basis of molecular diagnostic testing such as PCR assay.
Treatment and Prevention of Poxviral Infections in Birds Other Than Chickens and Turkeys
No treatment exists for birds infected with avian poxviruses; therefore, prevention is key.
A commercial vaccine for canaries is available in the US.
