Experimental infection of different species of birds with pigeon paramyxovirus type 1 virus--evaluation of clinical outcomes, viral shedding, and distribution in tissues.

Abstract

The virulence of pigeon paramyxovirus type 1 (PPMV-1) for different species of birds was investigated in two independent sets of experiments in which groups of pigeons, chickens, turkeys, quails, and geese (10 birds per group) were inoculated with 10(6) median embryo infectious doses of PPMV-1 isolate: 1) nonpassaged (nPPMV-1, intracerebral pathogenicity [ICPI] value = 1.27) and 2) after six passages in specific-pathogen-free chickens (pPPMV-1, ICPI = 1.46) via the oculonasal route. Naive birds were placed in contact with infected birds (two birds per group) to monitor virus transmission. Clinical observation was performed daily. Additionally, cloacal swabs, oropharyngeal swabs, and selected organ samples were collected on days 2, 4, 7, 10, and 14 postinfection and tested by real-time reverse transcriptase-PCR for estimation of viral shedding and distribution in tissues. Infected pigeons exhibited nervous and digestive tract symptoms, mortality, shedding, and transmission to contact birds. Chickens, turkeys, quails, and geese did not exhibit any clinical signs regardless of the PPMV-1 strain used for inoculation. However, in contrast to quails and geese, chickens and turkeys shed the virus via the oral cavity and cloaca, and transmission to contact birds was also observed. Viral RNA was identified in tissues collected from all pPPMV-1-infected birds, whereas negative results were obtained in the case of tissues taken from nPPMV-1-infected quails and geese. We conclude that the PPMV-1 used in this study was most virulent to pigeons, followed by chickens and turkeys, while quails and geese seem to have the highest level of innate resistance to this strain. However, passaging of PPMV-1 in chickens resulted in the increase of ICPI and noticeable but sometimes contrasting changes in the replication capacities of the virus.