Abstract
Transmission is a fundamental component of pathogen fitness. A better understanding of pathogen transmission can greatly improve disease management. In particular, controlled studies of multiple rounds of natural transmission (i.e. serial passage) can provide powerful epidemiological and evolutionary inferences. However, such studies are possible in only a few systems because of the challenges in successfully initiating and maintaining transmission in the laboratory. Here we developed an efficient and reproducible cohabitation method for conducting controlled experiments investigating the effects of serial passage on infectious hematopoietic necrosis virus (IHNV) in rainbow trout. This method was used to investigate the transmission efficiency and kinetics of viral shedding of IHNV over 3 serial passages. Transmission efficiency decreased from 100 to 62.5% over the passage steps and was associated with a decrease in virus shedding into water. A shift in the peak of viral shedding was also observed, from Day 2 post immersion for passage 0 to at least 24 h later for all subsequent passages. Finally, the characterization of viruses after 1 round of transmission and propagation on cells showed no change in glycoprotein (G gene) sequences or viral virulence compared to the ancestral virus stock. The methods developed provide valuable tools for reproducible population-level studies of IHNV epidemiology and evolution.
Highlights
Understanding pathogen transmission dynamics can provide powerful insights into infectious disease management
The efficiency of fish-to-fish transmission was investigated by quantifying the number of fish shedding at each of up to 3 passages of infectious hematopoietic necrosis virus (IHNV) in rainbow trout
We successfully developed a method to investigate fish-to-fish transmission of IHNV in rainbow trout and maintain transmission for up to 3 rounds of serial passage with an in vivo cohabitation design
Summary
Understanding pathogen transmission dynamics can provide powerful insights into infectious disease management. Transmission dynamics determine the rate at which pathogens spread and how many hosts become infected (Anderson & May 1992, Nelson & Williams 2013). Despite their epidemiological importance, pathogen transmission dynamics are difficult to study, are rarely quantified, and frequently warrant further investigation. When transmission has been studied, it is typically inferred either from disease dynamics at a host population level, from in vitro studies, or under artificial transmission routes (Wargo & Kurath 2012). These studies can be highly informative, they are often limited in their ability to Publisher: Inter-Research · www.int-res.com. Few studies have directly quantified the transmission dynamics of IHNV, through multiple rounds of transmission (Foreman et al 2015, Dixon et al 2016)
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