| Exotic birds, Psittaciformes in particular, continue to rise in popularity in North America, and such animals represent a small but growing and significant fraction of companion animal accessions to diagnostic laboratories (O'Toole et al., 1992). Consequently, Pacheco's disease, a psittacine herpesvirus infection, has become of increased concern to breeders and veterinarians. Mortality from Pacheco's disease can be very high and results in considerable economic loss to the pet bird industry. Often, captured young birds are quarantined together, under stressful conditions which promote the shedding of the virus from the pharynx and in the feces. Although the clinical signs are variable, infected birds are often lethargic, have inconstant diarrhea, and exhibit various lesions and hemorrhages of the liver and spleen. Secondary respiratory and renal complications may occur and mortality often approaches 100%.; Utilizing the recent advances in the expanding fields of bioinformatics and genomics technology, we have sequenced and characterized the causative agent for Pacheco's Disease virus (PDV), hereby designated PsHV-1 (Psittacid herpesvirus 1).; The PsHV-1 genome was determined to be 163,025 bp in length with a base composition of 60.95% G+C. The genome consists of two unique sequences, the long or UL (119,146 bp) and the short or US (16,405 bp), with the US region being flanked by inverted (IR) and terminal (TR) repeat elements 13,737 bp in length.; The PsHV-1 genome contains 73 putative genes and shares conserved homology with 70 of 77 genes identified within the genome of Infectious Laryngotracheitis virus (ILTV), an avian alphaherpesvirus. Similarities between PsHV-1 and ILTV can be seen in an inversion between UL44 and UL22 in the UL region, the absence of repeats flanking the UL region, the conserved structure of the US region, and a conserved cluster of 5 unique ORFs in the UL region. PsHV-1 and ILTV also share positionally conserved genes in the US region that are novel to these virus genomes.; The similarity of the PsHV-1 (psittacid) and ILTV ( gallid) genome structure and content, combined with phylogenetic analysis, suggests that PsHV-1 and ILTV represent a unique clade of avian alphaherpesviruses that are distinct from the Marek's family of alphaherpesviruses. We therefore recommend that PsHV-1 be classified as an avian alphaherpesvirus, genus Iltovirus. |
