Sebastián Salgado

Infectious laryngotracheitis virus (ILT) is the pathogen responsible for a respiratory ailment that has resulted in significant economic losses in the poultry industry, primarily due to high morbidity and mortality rates, as well as diminished egg production. However, for small producers living near the coast, where backyard flocks are located in rural areas, respiratory illness may pose a public health risk rather than an economic one, which must be considered in the differential diagnosis of ILT. Therefore, in this research, we focused on developing an efficient tool to detect, quantify, and classify infectious laryngotracheitis virus (ILTV) field variants. Our results demonstrates that qPCR detected positive samples collected between 2019 and 2023 in flocks exhibiting clinical signs of respiratory illness in Valdivia, in the Los Ríos Region of Southern Chile. Furthermore, the molecular characterization of positive samples using dideoxynucleotide sequencing revealed that the detected viruses were similar to tissue culture origin (TCO) vaccines, even though the birds had never been vaccinated. To the best of our knowledge, this is the first report characterizing ILTV variants in Chile using a molecular approach. Our findings indicate that the tool is useful for detecting ILTV and can also be used to quantify viral particles using a standard curve, making it a valuable tool for the differential diagnosis of respiratory pathogens in poultry.

Fish red blood cells (RBCs) are nucleated, transcriptionally active, and key players in both gas transport and immune responses. They are the primary targets of Orthoreovirus piscis (PRV), the etiological agent of heart and skeletal muscle inflammation (HSMI), which includes three genotypes (PRV-1, PRV-2, and PRV-3), linked to circulatory disorders in farmed salmon. In Chile, PRV-3 affects the coho salmon (Oncorhynchus kisutch), but host–pathogen interactions remain poorly characterized. This study compared the interactions of PRV-3 in coho salmon and PRV-1 in Atlantic salmon (Salmo salar) using RBC infection models. RBCs were isolated from healthy juvenile salmon (n = 3) inoculated with either PRV-1 (Ct = 18.87) or PRV-3 (Ct = 21.86). Poly I:C (50 µg/mL) was used as a positive control for the antiviral response. Cells were monitored for up to 14 days post-infection (dpi). PRV-3 infection in coho salmon RBCs caused significant metabolic disruption, apoptosis from 7 dpi, and correlated with increasing viral loads. In contrast, PRV-1 infection in Atlantic salmon RBCs showed limited apoptosis and maintained cell viability. Coho salmon RBCs upregulated rig-i, mx, and pkr transcripts, indicating activation of the type I interferon pathway, whereas Atlantic salmon RBCs exhibited a more attenuated response. PRV-3 induced notable morphological changes in coho salmon RBCs, although neither PRV-3 nor PRV-1 caused hemolysis. These findings highlight species-specific differences in RBC responses to PRV infection and provide new insights into the pathogenesis of PRV-3 and PRV-1.