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1. Environmental Factors and Host Microbiomes Shape Host–Pathogen Dynamics

   https://doi.org/10.1016/j.pt.2020.04.010  

   Bernardo-Cravo, Adriana P.; Schmeller, Dirk S.; Chatzinotas, Antonis; Vredenburg, Vance T.; Loyau, Adeline (July 2020, Trends in Parasitology)
2. The evolution of parasite host range in heterogeneous host populations

   https://doi.org/10.1111/jeb.13608  

   Gibson, Amanda K.; Baffoe‐Bonnie, Helena; Penley, McKenna J.; Lin, Julie; Owens, Raythe; Khalid, Arooj; Morran, Levi T. (March 2020, Journal of Evolutionary Biology)

   Abstract Theory on the evolution of niche width argues that resource heterogeneity selects for niche breadth. For parasites, this theory predicts that parasite populations will evolve, or maintain, broader host ranges when selected in genetically diverse host populations relative to homogeneous host populations. To test this prediction, we selected the bacterial parasiteSerratia marcescensto killCaenorhabditis elegansin populations that were genetically heterogeneous (50% mix of two experimental genotypes) or homogeneous (100% of either genotype). After 20 rounds of selection, we compared the host range of selected parasites by measuring parasite fitness (i.e. virulence, the selected fitness trait) on the two focal host genotypes and on a novel host genotype. As predicted, heterogeneous host populations selected for parasites with a broader host range: these parasite populations gained or maintained virulence on all host genotypes. This result contrasted with selection in homogeneous populations of one host genotype. Here, host range contracted, with parasite populations gaining virulence on the focal host genotype and losing virulence on the novel host genotype. This pattern was not, however, repeated with selection in homogeneous populations of the second host genotype: these parasite populations did not gain virulence on the focal host genotype, nor did they lose virulence on the novel host genotype. Our results indicate that host heterogeneity can maintain broader host ranges in parasite populations. Individual host genotypes, however, vary in the degree to which they select for specialization in parasite populations. 

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3. Host Congestion Control

   https://doi.org/10.1145/3603269.3604878  

   Agarwal, Saksham; Krishnamurthy, Arvind; Agarwal, Rachit (September 2023, SIGCOMM)
4. Host species differences in the thermal mismatch of host–parasitoid interactions

   https://doi.org/10.1242/jeb.245702  

   Malinski, Katherine H.; Sorenson, Clyde E.; Moore, M. Elizabeth; Willett, Christopher S.; Kingsolver, Joel G. (June 2023, Journal of Experimental Biology)

   ABSTRACT Extreme high temperatures associated with climate change can affect species directly, and indirectly through temperature-mediated species interactions. In most host–parasitoid systems, parasitization inevitably kills the host, but differences in heat tolerance between host and parasitoid, and between different hosts, may alter their interactions. Here, we explored the effects of extreme high temperatures on the ecological outcomes – including, in some rare cases, escape from the developmental disruption of parasitism – of the parasitoid wasp, Cotesia congregata, and two co-occurring congeneric larval hosts, Manduca sexta and M. quinquemaculata. Both host species had higher thermal tolerance than C. congregata, resulting in a thermal mismatch characterized by parasitoid (but not host) mortality under extreme high temperatures. Despite parasitoid death at high temperatures, hosts typically remain developmentally disrupted from parasitism. However, high temperatures resulted in a partial developmental recovery from parasitism (reaching the wandering stage at the end of host larval development) in some host individuals, with a significantly higher frequency of this partial developmental recovery in M. quinquemaculata than in M. sexta. Hosts species also differed in their growth and development in the absence of parasitoids, with M. quinquemaculata developing faster and larger at high temperatures relative to M. sexta. Our results demonstrate that co-occurring congeneric species, despite shared environments and phylogenetic histories, can vary in their responses to temperature, parasitism and their interaction, resulting in altered ecological outcomes. 

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5. A multi-scale cholera model linking between-host and within-host dynamics

   https://doi.org/10.1142/S1793524518500341  

   Yang, Chayu; Posny, Drew; Bao, Feng; Wang, Jin (April 2018, International Journal of Biomathematics)

   We propose a multi-scale modeling framework to investigate the transmission dynamics of cholera. At the population level, we employ a SIR model for the between-host transmission of the disease. At the individual host level, we describe the evolution of the pathogen within the human body. The between-host and within-host dynamics are connected through an environmental equation that characterizes the growth of the pathogen and its interaction with the hosts outside the human body. We put a special emphasis on the within-host dynamics by making a distinction for each individual host. We conduct both mathematical analysis and numerical simulation for our model in order to explore various scenarios associated with cholera transmission and to better understand the complex, multi-scale disease dynamics. 

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