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1. The effects of lifestyle change on indicators of cardiometabolic health in semi-nomadic pastoralists

   https://doi.org/10.1093/emph/eoad030  

   Swanson, Zane S. ; Bethancourt, Hilary ; Nzunza, Rosemary ; Ndiema, Emmanuel ; Braun, David R. ; Rosinger, Asher Y. ; Pontzer, Herman ( September 2023 , Evolution, Medicine, and Public Health)

   Non-communicable disease risk and the epidemic of cardiometabolic diseases continue to grow across the expanding industrialized world. Probing the relationships between evolved human physiology and modern socioecological conditions is central to understanding this health crisis. Therefore, we investigated the relationships between increased market access, shifting subsistence patterns and cardiometabolic health indicators within Daasanach semi-nomadic pastoralists who vary in their engagement in traditional lifestyle and emerging market behaviors.

   We conducted cross-sectional socioecological, demographic and lifestyle stressor surveys along with health, biomarker and nutrition examinations among 225 (51.6% female) Daasanach adults in 2019–2020. We used linear mixed-effects models to test how differing levels of engagement in market integration and traditional subsistence activities related to blood pressure (BP), body composition and blood chemistry.

   We found that systolic and diastolic BP, as well as the probability of having high BP (hypertension), were negatively associated with distance to market, a proxy for market integration. Additionally, body composition varied significantly by socioeconomic status (SES), with significant positive associations between BMI and body fat and higher SES among adults.

   While evidence for evolutionary mismatch and health variation have been found across a number of populations affected by an urban/rural divide, these results demonstrate the effects of market integration and sedentarization on cardiometabolic health associated with the early stages of lifestyle changes. Our findings provide evidence for the changes in health when small-scale populations begin the processes of sedentarization and market integration that result from myriad market pressures.

    

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2. Galectins in Host–Pathogen Interactions: Structural, Functional and Evolutionary Aspects

   https://doi.org/10.1007/978-981-15-1580-4_7  

   Vasta, G ( January 2020 , Advances in experimental medicine and biology)

   Galectins are a family of ß-galactoside-binding lectins characterized by a unique sequence motif in the carbohydrate recognition domain, and evolutionary and structural conservation from fungi to invertebrates and vertebrates, including mammals. Their biological roles, initially understood as limited to recognition of endogenous (“self”) carbohydrate ligands in embryogenesis and early development, dramatically expanded in later years by the discovery of their roles in tissue repair, cancer, adipogenesis, and regulation of immune homeostasis. In recent years, however, evidence has also accumulated to support the notion that galectins can bind (“non-self”) glycans on the surface of potentially pathogenic microbes, and function as recognition and effector factors in innate immunity. Thus, this evidence has established a newparadigm by which galectins can function not only as pattern recognition receptors but also as effector factors, by binding to the microbial surface and inhibiting adhesion and/or entry into the host cell, directly killing the potential pathogen by disrupting its surface structures, or by promoting phagocytosis, encapsulation, autophagy, and pathogen clearance from circulation. Strikingly, some viruses, bacteria, and protistan parasites take advantage of the aforementioned recognition roles of the vector/host galectins, for successful attachment and invasion. These recent findings suggest that galectin-mediated innate immune recognition and effector mechanisms, which throughout evolution have remained effective for preventing or fighting viral, bacterial, and parasitic infection, have been “subverted” by certain pathogens by unique evolutionary adaptations of their surface glycome to gain host entry, and the acquisition of effective mechanisms to evade the host’s immune responses. 

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3. What Does Tolerance Mean for Animal Disease Dynamics When Pathology Enhances Transmission?

   https://doi.org/10.1093/icb/icz065  

   Henschen, Amberleigh E. ; Adelman, James S. ( May 2019 , Integrative and Comparative Biology)

   Host competence, or how well an individual transmits pathogens, varies substantially within and among animal populations. As this variation can alter the course of epidemics and epizootics, revealing its underlying causes will help predict and control the spread of disease. One host trait that could drive heterogeneity in competence is host tolerance, which minimizes fitness losses during infection without decreasing pathogen load. In many cases, tolerance should increase competence by extending infectious periods and enabling behaviors that facilitate contact among hosts. However, we argue that the links between tolerance and competence are more varied. Specifically, the different physiological and behavioral mechanisms by which hosts achieve tolerance should have a range of effects on competence, enhancing the ability to transmit pathogens in some circumstances and impeding it in others. Because tissue-based pathology (damage) that reduces host fitness is often critical for pathogen transmission, we focus on two mechanisms that can underlie tolerance at the tissue level: damage-avoidance and damage-repair. As damage-avoidance reduces transmission-enhancing pathology, this mechanism is likely to decrease host competence and pathogen transmission. In contrast, damage-repair does not prevent transmission-relevant pathology from occurring. Rather, damage-repair provides new, healthy tissues that pathogens can exploit, likely extending the infectious period and increasing host competence. We explore these concepts through graphical models and present three disease systems in which damage-avoidance and damage-repair alter host competence in the predicted directions. Finally, we suggest that by incorporating these links, future theoretical studies could provide new insights into infectious disease dynamics and host–pathogen coevolution.

    

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4. Individual variation in feather corticosterone levels and its influence on haemosporidian infection in a Neotropical bird

   https://doi.org/10.1111/ibi.12709  

   Bosholn, Mariane ; Anciães, Marina ; Gil, Diego ; Weckstein, Jason D. ; Dispoto, Janice H. ; Fecchio, Alan ( February 2019 , Ibis)

   Corticosterone (CORT) is the main glucocorticoid hormone of amphibians, reptiles, birds and some mammals. This hormone may have evolved as an adaptive metabolic mechanism, in part because increased concentrations ofCORTare essential for individuals to manage energy resources and thus cope with negative perturbations such as predation and storms. The benefits ofCORTare offset by costs, because elevated levels can suppress inflammatory responses of individuals, making them more susceptible to parasites and pathogens. In this study, we investigated the relationships between featherCORTlevels, infection status and diversity of haemosporidian parasites in the Blue‐crowned ManakinLepidothrix coronata, considering possible effects related to the sex and age of individuals. We predicted higher levels of featherCORTin infected individuals. We observed that featherCORTlevels were similar among individuals of different sexes and ages. Although haemosporidian infection status did not vary among sexes, occurrence probability was higher among younger individuals, which may indicate that the less developed immune system of these individuals makes them more susceptible to avian malaria. Contrary to expectations, we found that featherCORTlevels were not associated with the infection status and diversity of haemosporidian parasites. That haemosporidian occurrence probability does not increase with elevated featherCORTlevels suggests that individuals are not immunosuppressed by elevated levels of this hormone, at least to the extent that featherCORTtruly reflects individual differences in the level of this hormone.

    

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5. An aphid symbiont confers protection against a specialized RNA virus, another increases vulnerability to the same pathogen

   https://doi.org/10.1111/mec.16801  

   Higashi, Clesson H. ; Nichols, William L. ; Chevignon, Germain ; Patel, Vilas ; Allison, Suzanne E. ; Kim, Kyungsun Lee ; Strand, Michael R. ; Oliver, Kerry M. ( February 2023 , Molecular Ecology)

   Insects often harbour heritable symbionts that provide defence against specialized natural enemies, yet little is known about symbiont protection when hosts face simultaneous threats. In pea aphids (Acyrthosiphon pisum), the facultative endosymbiontHamiltonella defensaconfers protection against the parasitoid,Aphidius ervi, andRegiella insecticolaprotects against aphid‐specific fungal pathogens, includingPandora neoaphidis. Here, we investigated whether these two common aphid symbionts protect against a specialized virusA. pisum virus(APV), and whether their antifungal and antiparasitoid services are impacted by APV infection. We found that APV imposed large fitness costs on symbiont‐free aphids and these costs were elevated in aphids also housingH. defensa. In contrast, APV titres were significantly reduced and costs to APV infection were largely eliminated in aphids withR. insecticola. To our knowledge,R. insecticolais the first aphid symbiont shown to protect against a viral pathogen, and only the second arthropod symbiont reported to do so. In contrast, APV infection did not impact the protective services of eitherR. insecticolaorH. defensa. To better understand APV biology, we produced five genomes and examined transmission routes. We found that moderate rates of vertical transmission, combined with horizontal transfer through food plants, were the major route of APV spread, although lateral transfer by parasitoids also occurred. Transmission was unaffected by facultative symbionts. In summary, the presence and species identity of facultative symbionts resulted in highly divergent outcomes for aphids infected with APV, while not impacting defensive services that target other enemies. These findings add to the diverse phenotypes conferred by aphid symbionts, and to the growing body of work highlighting extensive variation in symbiont‐mediated interactions.

    

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