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1. Host Controls of Within-Host Disease Dynamics: Insight from an Invertebrate System

   https://doi.org/https://doi.org/10.1086/715355  

   Stewart Merrill, Tara E.; Rapti, Z.; Caceres, Carla E. (September 2021, The American naturalist)

   null (Ed.)
2. Asymmetric host movement reshapes local disease dynamics in metapopulations

   https://doi.org/10.1038/s41598-022-12774-5  

   Michalska-Smith, Matthew; VanderWaal, Kimberly; Craft, Meggan E. (December 2022, Scientific Reports)

   Abstract Understanding how the movement of individuals affects disease dynamics is critical to accurately predicting and responding to the spread of disease in an increasingly interconnected world. In particular, it is not yet known how movement between patches affects local disease dynamics (e.g., whether pathogen prevalence remains steady or oscillates through time). Considering a set of small, archetypal metapopulations, we find three surprisingly simple patterns emerge in local disease dynamics following the introduction of movement between patches: (1) movement between identical patches with cyclical pathogen prevalence dampens oscillations in the destination while increasing synchrony between patches; (2) when patches differ from one another in the absence of movement, adding movement allows dynamics to propagate between patches, alternatively stabilizing or destabilizing dynamics in the destination based on the dynamics at the origin; and (3) it is easier for movement to induce cyclical dynamics than to induce a steady-state. Considering these archetypal networks (and the patterns they exemplify) as building blocks of larger, more realistically complex metapopulations provides an avenue for novel insights into the role of host movement on disease dynamics. Moreover, this work demonstrates a framework for future predictive modelling of disease spread in real populations. 

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3. Disease tolerance alters host competence in a wild songbird

   https://doi.org/10.1098/rsbl.2021.0362  

   Ruden, Rachel M.; Adelman, James S. (October 2021, Biology Letters)

   Individuals can express a range of disease phenotypes during infection, with important implications for epidemics. Tolerance, in particular, is a host response that minimizes the per-pathogen fitness costs of infection. Because tolerant hosts show milder clinical signs and higher survival, despite similar pathogen burdens, their potential for prolonged pathogen shedding may facilitate the spread of pathogens. To test this, we simulated outbreaks of mycoplasmal conjunctivitis in house finches, asking how the speed of transmission varied with tissue-specific and behavioural components of tolerance, milder conjunctivitis and anorexia for a given pathogen load, respectively. Because tissue-specific tolerance hinders pathogen deposition onto bird feeders, important transmission hubs, we predicted it would slow transmission. Because behavioural tolerance should increase interactions with bird feeders, we predicted it would speed transmission. Our findings supported these predictions, suggesting that variation in tolerance could help identify individuals most likely to transmit pathogens. 

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4. Seasonality of host immunity in a tropical disease system

   https://doi.org/10.1002/ecs2.4158  

   Rosa, Gonçalo M.; Perez, Rachel; Richards, Lora A.; Richards‐Zawacki, Corinne L.; Smilanich, Angela M.; Reinert, Laura K.; Rollins‐Smith, Louise A.; Wetzel, Daniel P.; Voyles, Jamie (July 2022, Ecosphere)

   Abstract Infectious disease systems frequently exhibit strong seasonal patterns, yet the mechanisms that underpin intra‐annual cycles are unclear, particularly in tropical regions. We hypothesized that host immune function fluctuates seasonally, contributing to oscillations in infection patterns in a tropical disease system. To test this hypothesis, we investigated a key host defense of amphibians against a lethal fungal pathogen,Batrachochytrium dendrobatidis(Bd). We integrated two field experiments in which we perturbed amphibian skin secretions, a critical host immune mechanism, in Panamanian rocket frogs (Colostethus panamansis). We found that this immunosuppressive technique of reducing skin secretions in wild frog populations increasedBdprevalence and infection intensity, indicating that this immune defense contributes to resistance toBdin wild frog populations. We also found that the chemical composition and anti‐Bdeffectiveness of frog skin secretions varied across seasons, with greater pathogen inhibition during the dry season relative to the wet season. These results suggest that the effectiveness of this host defense mechanism shifts across seasons, likely contributing to seasonal infection patterns in a lethal disease system. More broadly, our findings indicate that host immune defenses can fluctuate across seasons, even in tropical regions where temperatures are relatively stable, which advances our understanding of intra‐annual cycles of infectious disease dynamics. 

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5. Why disease ecology needs life‐history theory: a host perspective

   https://doi.org/10.1111/ele.13681  

   Valenzuela‐Sánchez, Andrés; Wilber, Mark Q.; Canessa, Stefano; Bacigalupe, Leonardo D.; Muths, Erin; Schmidt, Benedikt R.; Cunningham, Andrew A.; Ozgul, Arpat; Johnson, Pieter T.J.; Cayuela, Hugo (April 2021, Ecology Letters)

   Hodgson, Dave (Ed.)