Fowlpox virus: The type species of the genus AVIPOXVIRUS. It is the etiologic agent of FOWLPOX.Fowlpox: A poxvirus infection of poultry and other birds characterized by the formation of wart-like nodules on the skin and diphtheritic necrotic masses (cankers) in the upper digestive and respiratory tracts.Poxviridae: A family of double-stranded DNA viruses infecting mammals (including humans), birds and insects. There are two subfamilies: CHORDOPOXVIRINAE, poxviruses of vertebrates, and ENTOMOPOXVIRINAE, poxviruses of insects.Avipoxvirus: A genus of the family POXVIRIDAE, subfamily CHORDOPOXVIRINAE, comprising bird poxviruses. The type species is FOWLPOX VIRUS. Transmission is mechanical by ARTHROPODS.Vaccinia virus: The type species of ORTHOPOXVIRUS, related to COWPOX VIRUS, but whose true origin is unknown. It has been used as a live vaccine against SMALLPOX. It is also used as a vector for inserting foreign DNA into animals. Rabbitpox virus is a subspecies of VACCINIA VIRUS.Reticuloendotheliosis Viruses, Avian: A group of viruses in the genus GAMMARETROVIRUS comprising a few isolates from birds, with no known corresponding endogenous relatives.Antigens, CD58: Glycoproteins with a wide distribution on hematopoietic and non-hematopoietic cells and strongly expressed on macrophages. CD58 mediates cell adhesion by binding to CD2; (ANTIGENS, CD2); and this enhances antigen-specific T-cell activation.Atadenovirus: A genus of ADENOVIRIDAE that comprises viruses of several species of MAMMALS and BIRDS. The type species is Ovine adenovirus D.Vaccines, Synthetic: Small synthetic peptides that mimic surface antigens of pathogens and are immunogenic, or vaccines manufactured with the aid of recombinant DNA techniques. The latter vaccines may also be whole viruses whose nucleic acids have been modified.Viral Vaccines: Suspensions of attenuated or killed viruses administered for the prevention or treatment of infectious viral disease.Reticuloendotheliosis virus: A species in the group RETICULOENDOTHELIOSIS VIRUSES, AVIAN of the genus GAMMARETROVIRUS that causes a chronic neoplastic and a more acute immunosuppressive disease in fowl.Immunization, Secondary: Any immunization following a primary immunization and involving exposure to the same or a closely related antigen.Chickens: Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA.Reticuloendotheliosis, Avian: A group of pathologic syndromes found in avian species caused by RETICULOENDOTHELIOSIS VIRUS. The distinct syndromes include non-neoplastic runting, acute neoplastic disease, and chronic neoplastic disease. Humans and mammals appear resistant.Chick Embryo: The developmental entity of a fertilized chicken egg (ZYGOTE). The developmental process begins about 24 h before the egg is laid at the BLASTODISC, a small whitish spot on the surface of the EGG YOLK. After 21 days of incubation, the embryo is fully developed before hatching.