Temporal characterization of the viral load of psittacine beak and feather disease virus in rosy-faced lovebirds (Agapornis roseicollis)

Psittacine beak and feather disease virus (PBFDV) is a widespread and highly pathogenic virus in parrots (Psittaciformes), threatening both captive and wild populations over the world. The disease typically presents with feather and beak abnormalities, along with possible immune system suppression. No cure or commercialized vaccine is currently available. Our understanding of the Psittacine beak and feather disease often come from infected individuals with visible symptoms. Limited knowledge exists regarding the pathology and role of asymptomatic individuals in disease transmission. Asymptomatic individuals could shed virus in their crop secretion, feces, or feathers. In this study, we investigated the temporal change in viral load in feather and fecal samples from 17 asymptomatic rosy-faced lovebirds (Agapornis roseicollis). We developed a qPCR assay for PBFDV viral load quantification in the studied lovebirds. Our results showed that most of the individuals had very low viral load, while three individuals with high viral load at the beginning of the experiment were observed to exhibit a decreasing trend in viral load in both fecal and feather samples. Surprisingly, the viral load in an individual can drop from a high level to an undetectable level within three months, which is contrary to the prevailing notion that the disease is highly lethal with few reports of complete recovery. We also showed that viral load in feathers was higher than in feces. Our study provides valuable insights into the infection dynamics of PBFDV in asymptomatic individuals and contribute to the understanding of disease transmission in parrots.