Climate warming and disease risks for terrestrial and marine biota

Landscape Seroprevalence of Three Hemorrhagic Disease-Causing Viruses in a Wild Cervid

Disease plays a major role in shaping wildlife populations worldwide, and changes in landscape conditions can significantly influence risk of pathogen exposure, a threat to vulnerable wild species. Three viruses that cause hemorrhagic disease affect cervid populations in the USA (Odocoileus hemionus adenovirus, bluetongue virus, and epizootic hemorrhagic disease virus), but little is known of their distribution and prevalence in wild populations. We explored the distribution and co-occurrence of seroprevalence of these three pathogens in southern mule deer (Odocoileus hemionus fuliginatus), a subspecies of conservation concern and a harvested species native to southern California, to evaluate the distribution of exposure to these pathogens relative to landscape attributes. We found that habitat type, level of development, and proximity to livestock may affect hemorrhagic disease seroprevalence in southern mule deer. Continued monitoring of hemorrhagic disease-causing viruses in areas where deer are in proximity to cattle and human development is needed to better understand the implications of future outbreaks in wild populations and to identify opportunities to mitigate disease impacts in southern mule deer and other cervid species.

Evolutionary rescue in host-pathogen systems

Natural populations encounter a variety of threats that can increase their risk of extinction. Populations can avoid extinction through evolutionary rescue (ER), which occurs when an adaptive, genetic response to selection allows a population to recover from an environmental change that would otherwise cause extinction. While the traditional framework for ER was developed with abiotic risk factors in mind, ER may also occur in response to a biotic source of demographic change, such as the introduction of a novel pathogen. We first describe how ER in response to a pathogen differs from the traditional ER framework; density-dependent transmission, pathogen evolution, and pathogen extinction can change the strength of selection imposed by a pathogen and make host population persistence more likely. We also discuss several variables that affect traditional ER (abundance, genetic diversity, population connectivity, and community composition) that also directly affect disease risk resulting in diverse outcomes for ER in host-pathogen systems. Thus, generalizations developed in studies of traditional ER may not be relevant for ER in response to the introduction of a pathogen. Incorporating pathogens into the framework of ER will lead to a better understanding of how and when populations can avoid extinction in response to novel pathogens.

The effect of host community functional traits on plant disease risk varies along an elevational gradient

Quantifying the relative impact of environmental conditions and host community structure on disease is one of the greatest challenges of the 21st century, as both climate and biodiversity are changing at unprecedented rates. Both increasing temperature and shifting host communities toward more fast-paced life-history strategies are predicted to increase disease, yet their independent and interactive effects on disease in natural communities remain unknown. Here, we address this challenge by surveying foliar disease symptoms in 220, 0.5 m-diameter herbaceous plant communities along a 1100-m elevational gradient. We find that increasing temperature associated with lower elevation can increase disease by (1) relaxing constraints on parasite growth and reproduction, (2) determining which host species are present in a given location, and (3) strengthening the positive effect of host community pace-of-life on disease. These results provide the first field evidence, under natural conditions, that environmental gradients can alter how host community structure affects disease.

Climate change is causing shifts in the ecology and biodiversity of different world regions at unprecedented rates. Global warming is also linked with changes in the risk for certain infectious diseases in humans, but also in animals and plants. There are several possible mechanisms for this. For one thing, changing weather patterns may affect how pathogens grow and reproduce. For another, the distribution ranges of animal and plant hosts of certain disease-causing pathogens are changing because of global warming. This means that the distributions of pathogens are also changing, and so is the severity of the diseases that they cause.

Increasing temperatures may also influence the physiological traits that make host species suitable for pathogens. This is because the traits that allow species to survive or adapt to changes in their environment may also make them better at hosting and transmitting the pathogens that cause disease. For example, in plant communities, rising temperatures could favor species with faster growth rates, quicker reproduction and high dispersal, and these traits are often associated with more efficient spread of disease.

Despite a lot of research into the effects of climate, it remains unclear how temperature, pathogen growth and reproduction, and host species’ traits and distributions combine and interact to alter infectious disease risk, especially in wild plant communities. To investigate this, Halliday, Jalo and Laine studied an area in southeast Switzerland where natural temperature and biodiversity change gradually through the region. The aim was to explore how relationships between plant biodiversity, pathogens and disease risk change with temperature, and to understand whether environmental or biological factors influence infectious disease risk more.

Halliday, Jalo and Laine measured the levels of fungal diseases found in the leaves of plant communities spanning 1,100 meters of elevation, showing that higher temperatures increase disease risk both directly and indirectly. Directly, higher temperatures increased pathogen growth and reproduction, and indirectly, they influenced which plants were present and therefore able to act as disease hosts. The results also indicated that temperature can affect how the traits of plants drive the transmission rates of fungal pathogens. Important predictors of disease risk were traits relating to the growth rate of host plants, which tended to increase in areas with low elevation where the surface of the soil was warm.

This study represents the first analysis, in wild plants, of how changing temperatures, the traits of shifting host species, and resident parasite populations interact to impact infectious disease risk. The insights Halliday, Jalo and Laine provided could aid in predicting how global climate change will influence infectious disease risk.

Development of duplex TaqMan-based real-time PCR assay for the simultaneous detection of Perkinsus olseni and P. chesapeaki in host Manila clam tissue samples

The aetiological agent Perkinsus olseni is globally recognised as a major threat for shellfish production considering its wide geographical distribution across Asia, Europe, Australia and South America. Another species, Perkinsus chesapeaki, which has never been known to be associated with significant mortality events, was recently detected along French coasts infecting clam populations sporadically in association with P. olseni. Identifying potential cryptic infections affecting Ruditapes philippinarum is essential to develop appropriate host resource management strategies. Here, we developed a molecular method based on duplex real-time quantitative PCR for the simultaneous detection of these two parasites, P. olseni and P. chesapeaki, in the different clam tissues: gills, digestive gland, foot, mantle, adductor muscle and the rest of the soft body. We firstly checked the presence of possible PCR inhibitors in host tissue samples. The qPCR reactions were inhibited depending on the nature of the host organ. The mantle and the rest of the soft body have a high inhibitory effect from threshold of host gDNA concentration of 2 ng.µL^-1, the adductor muscle and the foot have an intermediate inhibition of 5 ng.µL^-1, and the gills and digestive gland do not show any inhibition of the qPCR reaction even at the highest host gDNA concentration of 20 ng.µL^-1. Then, using the gills as a template, the suitability of the molecular technique was checked in comparison with the Ray's Fluid Thioglycolate Medium methodology recommended by the World Organisation for Animal Health. The duplex qPCR method brought new insights and unveiled cryptic infections as the co-occurrence of P. olseni and P. chesapeaki from in situ tissue samples in contrast to the RFTM diagnosis. The development of this duplex qPCR method is a fundamental work to monitor in situ co-infections that will lead to optimised resource management and conservation strategies to deal with emerging diseases.

Characterization of the microbiome and immune response in corals with chronic Montipora white syndrome

Coral diseases have increased in frequency and intensity around the tropics worldwide. However, in many cases, little is known about their etiology. Montipora white syndrome (MWS) is a common disease affecting the coral Montipora capitata, a major reef builder in Hawai'i. Chronic Montipora white syndrome (cMWS) is a slow-moving form of the disease that affects M. capitata throughout the year. The effects of this chronic disease on coral immunology and microbiology are currently unknown. In this study, we use prophenoloxidase immune assays and 16S rRNA gene amplicon sequencing to characterize the microbiome and immunological response associated with cMWS. Our results show that immunological and microbiological responses are highly localized. Relative to diseased samples, apparently healthy portions of cMWS corals differed in immune activity and in the relative abundance of microbial taxa. Coral tissues with cMWS showed decreased tyrosinase-type catecholase and tyrosinase-type cresolase activity and increased laccase-type activity. Catecholase and cresolase activity were negatively correlated across all tissue types with microbiome richness. The localized effect of cMWS on coral microbiology and immunology is probably an important reason for the slow progression of the disease. This local confinement may facilitate interventions that focus on localized treatments on tissue types. This study provides an important baseline to understand the interplay between the microbiome and immune system and the mechanisms used by corals to manage chronic microbial perturbations associated with white syndrome.

Viral susceptibility across host species is largely independent of dietary protein to carbohydrate ratios

The likelihood of a successful host shift of a parasite to a novel host species can be influenced by environmental factors that can act on both the host and parasite. Changes in nutritional resource availability have been shown to alter pathogen susceptibility and the outcome of infection in a range of systems. Here, we examined how dietary protein to carbohydrate altered susceptibility in a large cross-infection experiment. We infected 27 species of Drosophilidae with an RNA virus on three food types of differing protein to carbohydrate ratios. We then measured how viral load and mortality across species was affected by changes in diet. We found that changes in the protein:carbohydrate in the diet did not alter the outcomes of infection, with strong positive inter-species correlations in both viral load and mortality across diets, suggesting no species-by-diet interaction. Mortality and viral load were strongly positively correlated, and this association was consistent across diets. This suggests changes in diet may give consistent outcomes across host species, and may not be universally important in determining host susceptibility to pathogens.

Shifts in global bat diversity suggest a possible role of climate change in the emergence of SARS-CoV-1 and SARS-CoV-2

Bats are the likely zoonotic origin of several coronaviruses (CoVs) that infect humans, including SARS-CoV-1 and SARS-CoV-2, both of which have caused large-scale epidemics. The number of CoVs present in an area is strongly correlated with local bat species richness, which in turn is affected by climatic conditions that drive the geographical distributions of species. Here we show that the southern Chinese Yunnan province and neighbouring regions in Myanmar and Laos form a global hotspot of climate change-driven increase in bat richness. This region coincides with the likely spatial origin of bat-borne ancestors of SARS-CoV-1 and SARS-CoV-2. Accounting for an estimated increase in the order of 100 bat-borne CoVs across the region, climate change may have played a key role in the evolution or transmission of the two SARS CoVs.

Intense nocturnal warming alters growth strategies, colouration and parasite load in a diurnal lizard

In the past decades, nocturnal temperatures have been playing a disproportionate role in the global warming of the planet. Yet, they remain a neglected factor in studies assessing the impact of global warming on natural populations. Here, we question whether an intense augmentation of nocturnal temperatures is beneficial or deleterious to ectotherms. Physiological performance is influenced by thermal conditions in ectotherms and an increase in temperature by only 2°C is sufficient to induce a disproportionate increase in metabolic expenditure. Warmer nights may expand ectotherms' species thermal niche and open new opportunities for prolonged activities and improve foraging efficiency. However, increased activity may also have deleterious effects on energy balance if exposure to warmer nights reduces resting periods and elevates resting metabolic rate. We assessed whether warmer nights affected an individual's growth, dorsal skin colouration, thermoregulation behaviour, oxidative stress status and parasite load by exposing yearling common lizards (Zootoca vivipara) from four populations to either ambient or high nocturnal temperatures for approximately 5 weeks. Warmer nocturnal temperatures increased the prevalence of ectoparasitic infestation and altered allocation of resources towards structural growth rather than storage. We found no change in markers for oxidative stress. The thermal treatment did not influence thermal preferences, but influenced dorsal skin brightness and luminance, in line with a predicted acclimation response in colder environments to enhance heat gain from solar radiation. Altogether, our results highlight the importance of considering nocturnal warming as an independent factor affecting ectotherms' life history in the context of global climate change. ​.

Metabarcoding of environmental samples suggest wide distribution of eelgrass (Zostera marina) pathogens in the north Pacific

Seagrass meadows provide important ecological services to the marine environment but are declining worldwide. Although eelgrass meadows in the north Pacific are thought to be relatively healthy, few studies have assessed the presence of known disease pathogens in these meadows. In a pilot study to test the efficacy of the methods and to provide foundational disease biodiversity data in the north Pacific, we leveraged metabarcoding of environmental DNA extracted from water, sediment, and eelgrass tissue samples collected from five widely distributed eelgrass meadows in Alaska and one in Japan and uncovered wide prevalence of two classes of pathogenic organisms – Labyrinthula zosterae and other associated strains of Labyrinthula, and the Phytophthora/Halophytophthora blight species complex – known to have caused decline in eelgrass (Zostera marina) elsewhere in the species’ global distribution. Although the distribution of these disease organisms is not well understood in the north Pacific, we uncovered the presence of at least one eelgrass pathogen at every locality sampled.

First record of Ornithonyssus bursa (Berlese, 1888) (Mesostigmata: Macronyssidae) parasitizing invasive monk parakeets in Santiago, Chile

Myiopsitta monachus is an invasive psittacine with wide distribution due to the pet trade. Its large communal nests and synanthropic nature contribute to its successful colonization of cities, from where it seems to be expanding in range and numbers. This is relevant with regard to pathogens that invasive species may harbor, especially when host populations thrive. We aimed to identify an abundant mite found in invasive monk parakeet chicks that had been collected in Santiago during 2017 and 2018. Through morphological and molecular identification of the 18S ribosomal RNA gene, we confirmed the presence of Ornithonyssus bursa. This was the first report of this mite in Chile. This mite is common in native and invasive monk parakeet populations and may affect other birds, including domestic fowl. Further, this mite bites people and can be a potential vector of pathogens such as bacteria or viruses. We conclude that this parasite was likely introduced with the parakeet and discuss possible ecological, health and economic consequences of this new potential pest.

Parasitism and host behavior in the context of a changing environment: The Holocene record of the commercially important bivalve Chamelea gallina, northern Italy

Rapid warming and sea-level rise are predicted to be major driving forces in shaping coastal ecosystems and their services in the next century. Though forecasts of the multiple and complex effects of temperature and sea-level rise on ecological interactions suggest negative impacts on parasite diversity, the effect of long term climate change on parasite dynamics is complex and unresolved. Digenean trematodes are complex life cycle parasites that can induce characteristic traces on their bivalve hosts and hold potential to infer parasite host-dynamics through time and space. Previous work has demonstrated a consistent association between sea level rise and increasing prevalence of trematode traces, but a number of fundamental questions remain unanswered about this paleoecological proxy. Here we examine the relationships of host size, shape, and functional morphology with parasite prevalence and abundance, how parasites are distributed across hosts, and how all of these relationships vary through time, using the bivalve Chamelea gallina from a Holocene shallow marine succession in the Po coastal plain. Trematode prevalence increased and decreased in association with the transition from a wave-influenced estuarine system to a wave-dominated deltaic setting. Prevalence and abundance of trematode pits are associated with large host body size, reflecting ontogenetic accumulation of parasites, but temporal trends in median host size do not explain prevalence trends. Ongoing work will test the roles of temperature, salinity, and nutrient availability on trematode parasitism. Parasitized bivalves in one sample were shallower burrowers than their non-parasitized counterparts, suggesting that hosts of trematodes can be more susceptible to their predators, though the effect is ephemeral. Like in living parasite-host systems, trematode-induced malformations are strongly aggregated among hosts, wherein most host individuals harbor very few parasites while a few hosts have many. We interpret trace aggregation to support the assumption that traces are a reliable proxy for trematode parasitism in the fossil record.

Effects and interaction of meteorological factors on hemorrhagic fever with renal syndrome incidence in Huludao City, northeastern China, 2007-2018

Background

Hemorrhagic fever with renal syndrome (HFRS), a rodent-borne disease, is a severe public health threat. Previous studies have discovered the influence of meteorological factors on HFRS incidence, while few studies have concentrated on the stratified analysis of delayed effects and interaction effects of meteorological factors on HFRS.

Objective

Huludao City is a representative area in north China that suffers from HFRS with primary transmission by Rattus norvegicus. This study aimed to evaluate the climate factors of lag, interaction, and stratified effects of meteorological factors on HFRS incidence in Huludao City.

Methods

Our researchers collected meteorological data and epidemiological data of HFRS cases in Huludao City during 2007–2018. First, a distributed lag nonlinear model (DLNM) for a maximum lag of 16 weeks was developed to assess the respective lag effect of temperature, precipitation, and humidity on HFRS incidence. We then constructed a generalized additive model (GAM) to explore the interaction effect between temperature and the other two meteorological factors on HFRS incidence and the stratified effect of meteorological factors.

Results

During the study period, 2751 cases of HFRS were reported in Huludao City. The incidence of HFRS showed a seasonal trend and peak times from February to May. Using the median WAT, median WTP, and median WARH as the reference, the results of DLNM showed that extremely high temperature (97.5^th percentile of WAT) had significant associations with HFRS at lag week 15 (RR = 1.68, 95% CI: 1.04–2.74) and lag week 16 (RR = 2.80, 95% CI: 1.31–5.95). Under the extremely low temperature (2.5^th percentile of WAT), the RRs of HFRS infection were significant at lag week 5 (RR = 1.28, 95% CI: 1.01–1.67) and lag 6 weeks (RR = 1.24, 95% CI: 1.01–1.57). The RRs of relative humidity were statistically significant at lag week 10 (RR = 1.19, 95% CI: 1.00–1.43) and lag week 11 (RR = 1.24, 95% CI: 1.02–1.50) under extremely high relative humidity (97.5^th percentile of WARH); however, no statistically significance was observed under extremely low relative humidity (2.5^th percentile of WARH). The RRs were significantly high when WAT was -10 degrees Celsius (RR = 1.34, 95% CI: 1.02–1.76), -9 degrees Celsius (1.37, 95% CI: 1.04–1.79), and -8 degrees Celsius (RR = 1.34, 95% CI: 1.03–1.75) at lag week 5 and more than 23 degrees Celsius after 15 weeks. Interaction and stratified analyses showed that the risk of HFRS infection reached its highest when both temperature and precipitation were at a high level.

Conclusions

Our study indicates that meteorological factors, including temperature and humidity, have delayed effects on the occurrence of HFRS in the study area, and the effect of temperature can be modified by humidity and precipitation. Public health professionals should pay more attention to HFRS control when the weather conditions of high temperature with more substantial precipitation and 15 weeks after the temperature is higher than 23 degrees Celsius.

Climate change impacts vector-borne disease incidence by influencing vectors’ habitat and behaviors. As a rodent-borne disease, HFRS’s incidence rate fluctuates with the change of meteorological factors. In this study, we model the meteorological factors and time-series cases to explore the exposure-lag-response effect and interaction between meteorological factors on the risk of HFRS, respectively. The result showed there exist a lag effect between meteorological factors and the occurrence of HFRS and we find that a temperature higher than 23 Celsius degrees resulted in a significantly higher HFRS incidence after 15 weeks; a relative humidity higher than 93% led to a significantly higher incidence after 10 weeks. Also, a synergistic interaction between high temperature and high precipitation on HFRS risk was detected, this effect can be attributed to increased animal reproduction and food resources under this environment. This study provides a basis for in-depth evaluating the impact of meteorological factors and their interaction on HFRS.

The Pacific Oyster Mortality Syndrome, a Polymicrobial and Multifactorial Disease: State of Knowledge and Future Directions

The Pacific oyster (Crassostreae gigas) has been introduced from Asia to numerous countries around the world during the 20th century. C. gigas is the main oyster species farmed worldwide and represents more than 98% of oyster production. The severity of disease outbreaks that affect C. gigas, which primarily impact juvenile oysters, has increased dramatically since 2008. The most prevalent disease, Pacific oyster mortality syndrome (POMS), has become panzootic and represents a threat to the oyster industry. Recently, major steps towards understanding POMS have been achieved through integrative molecular approaches. These studies demonstrated that infection by Ostreid herpesvirus type 1 µVar (OsHV-1 µvar) is the first critical step in the infectious process and leads to an immunocompromised state by altering hemocyte physiology. This is followed by dysbiosis of the microbiota, which leads to a secondary colonization by opportunistic bacterial pathogens, which in turn results in oyster death. Host and environmental factors (e.g. oyster genetics and age, temperature, food availability, and microbiota) have been shown to influence POMS permissiveness. However, we still do not understand the mechanisms by which these different factors control disease expression. The present review discusses current knowledge of this polymicrobial and multifactorial disease process and explores the research avenues that must be investigated to fully elucidate the complexity of POMS. These discoveries will help in decision-making and will facilitate the development of tools and applied innovations for the sustainable and integrated management of oyster aquaculture.

Thermal performance of the Chagas disease vector, Triatoma infestans, under thermal variability

Vector-borne diseases (VBD) are particularly susceptible to climate change because most of the diseases' vectors are ectotherms, which themselves are susceptible to thermal changes. The Chagas disease is one neglected tropical disease caused by the protozoan parasite, Trypanosoma cruzi. One of the main vectors of the Chagas disease in South America is Triatoma infestans, a species traditionally considered to be restricted to domestic or peridomestic habitats, but sylvatic foci have also been described along its distribution. The infestation of wild individuals, together with the projections of environmental changes due to global warming, urge the need to understand the relationship between temperature and the vector's performance. Here, we evaluated the impact of temperature variability on the thermal response of T. infestans. We acclimated individuals to six thermal treatments for five weeks to then estimate their thermal performance curves (TPCs) by measuring the walking speed of the individuals. We found that the TPCs varied with thermal acclimation and body mass. Individuals acclimated to a low and variable ambient temperature (18°C ± 5°C) exhibited lower performances than those individuals acclimated to an optimal temperature (27°C ± 0°C); while those individuals acclimated to a low but constant temperature (18°C ± 0°C) did not differ in their maximal performance from those at an optimal temperature. Additionally, thermal variability (i.e., ± 5°C) at a high temperature (30°C) increased performance. These results evidenced the plastic response of T. infestans to thermal acclimation. This plastic response and the non-linear effect of thermal variability on the performance of T. infestans posit challenges when predicting changes in the vector's distribution range under climate change.

Marine leech parasitism of sea turtles varies across host species, seasons, and the tumor disease fibropapillomatosis

Fibropapillomatosis (FP) is a tumorous disease affecting all species of sea turtles and is associated with the pathogen chelonid alphaherpesvirus 5 (ChHV5). Hypothesized ChHV5 vectors include the marine leeches Ozobranchus branchiatus and O. margoi, but data on their associations with FP and ChHV5 are minimal. To establish relationships between leech parasitism, turtle hosts, and FP, we compared green and loggerhead turtles from the Indian River Lagoon (IRL), Florida, USA, in terms of (1) the presence or absence of ChHV5 within associated leeches, (2) the association between leech parasitism and host FP status, and (3) seasonal variation in leech presence. We identified 55 leeches collected from green turtles as O. branchiatus and 22 leeches collected from loggerhead turtles as O. margoi. Of 77 sequenced leeches, 10 O. branchiatus and 5 O. margoi were ChHV5 positive. ChHV5-positive O. branchiatus trended towards coming from FP-positive hosts. Using 12 yr of turtle capture data from the IRL, we found that leech parasitism was significantly correlated with FP and capture month in green turtles but not in loggerhead turtles. These results suggest that O. branchiatus and O. margoi may differ in their ability to transmit ChHV5 or to encounter and remain on FP-positive hosts. Alternatively, potential immunological differences between green and loggerhead turtles may explain the observed relationships. This study is the first to provide robust statistical evidence of an association between leeches and FP, as well as seasonal fluctuations in leech presence, in green turtles but not in loggerhead turtles.

Cold water reduces the severity of parasite-inflicted damage: support for wintertime recuperation in aquatic hosts

The reduction in host fitness caused by parasite infections (virulence) depends on infection intensity and the degree of damage caused per parasite. Environmental conditions can shape both virulence components, but in contrast to infection intensity, environmental impacts on per-parasite damage are poorly understood. Here, we studied the effect of ambient temperature on per-parasite damage, which is jointly determined by the ability of parasites to induce harm (per-parasite pathogenicity) and the ability of hosts to limit damage (tolerance). We experimentally exposed two salmonid species, Atlantic salmon (Salmo salar) and sea trout (Salmo trutta), to replicated genotypes of the eye fluke Diplostomum pseudospathaceum. After development of health damage (eye cataracts) in warm water (16 °C) during the first 12 weeks post exposure, we maintained the fish at either 5 °C (cold water) or 16 °C for another 8 weeks and quantified changes in cataracts as a function of parasite load. We found that per-parasite damage was reduced in cold compared to warm water, suggesting that cold temperatures improved host health. Per-parasite damage was also affected by parasite genotype and host species, but these effects did not change with temperature. Our findings suggest that cold-water seasons, which are often neglected in host-parasite studies due to low infection risk, could allow hosts to recuperate and thus, may have important implications for the ecology and epidemiology of parasite infections.

Testing the developmental hypothesis of the HPA axis in a tropical passerine: Dampened corticosterone response and faster negative feedback in nestling lance-tailed manakins (Chiroxiphia lanceolata)

When vertebrates are exposed to stressors, the subsequent acute increase in glucocorticoids by the hypothalamic-pituitaryadrenal (HPA) axis triggers a suite of adaptive responses, including mobilization of stored energy and repression of non-essential processes. However, chronic exposure to high concentrations of glucocorticoids can lead to metabolic dysregulation, impaired immune function, and cognitive decline. In developing young, this hormonal stress response shows considerable variation. Generally, the physiological stress response of young of precocial species is comparable to that of adults, whereas offspring of altricial species exhibit an attenuated response compared to adults. The developmental hypothesis of the HPA axis proposes that the dampened stress response in dependent offspring is an adaptive response to avoid the negative effects of elevated glucocorticoids, particularly in altricial species where young lack the ability to mitigate stressful stimuli.We aimed to test the developmental hypothesis in a tropical avian species, the lance-tailed manakin (Chiroxiphia lanceolata). We predicted that nestlings of this altricial species should have a dampened corticosterone response, in both magnitude and duration, compared to that of adults. We also predicted that recently fledged hatch-year birds would display a response intermediate to that of adults and nestlings. We quantified circulating corticosterone levels in adults, recently fledged hatch-year birds, and 11-day-old nestlings using a standardized capture and restraint protocol. Nestlings showed a lower maximal corticosterone response and faster negative feedback compared to adults. Further, five post-fledging hatch-year birds showed a feedback response intermediate to those of nestlings and adults. However, we caution against generalizing about fledgling responses beyond this study due to the small sample (n = 5). Interestingly, lance-tailed manakin nestlings appear to return to baseline concentrations faster than nestlings of temperate species. These results support the developmental hypothesis of the HPA axis explaining variation in stress response. This study is the first to assess the development of the hormonal stress response in nestlings of a tropical bird, which is of interest because of our still-developing understanding of how tropical and temperate species differ physiologically. Finally, findings here underscore the importance of validating and adjusting sampling protocols that quantify nestling stress responses, as sampling timelines identified for adults may underestimate the magnitude of the nestling stress response.

Marine Parasites and Disease in the Era of Global Climate Change

Climate change affects ecological processes and interactions, including parasitism. Because parasites are natural components of ecological systems, as well as agents of outbreak and disease-induced mortality, it is important to summarize current knowledge of the sensitivity of parasites to climate and identify how to better predict their responses to it. This need is particularly great in marine systems, where the responses of parasites to climate variables are less well studied than those in other biomes. As examples of climate's influence on parasitism increase, they enable generalizations of expected responses as well as insight into useful study approaches, such as thermal performance curves that compare the vital rates of hosts and parasites when exposed to several temperatures across a gradient. For parasites not killed by rising temperatures, some simple physiological rules, including the tendency of temperature to increase the metabolism of ectotherms and increase oxygen stress on hosts, suggest that parasites' intensity and pathologies might increase. In addition to temperature, climate-induced changes in dissolved oxygen, ocean acidity, salinity, and host and parasite distributions also affect parasitism and disease, but these factors are much less studied. Finally, because parasites are constituents of ecological communities, we must consider indirect and secondary effects stemming from climate-induced changes in host-parasite interactions, which may not be evident if these interactions are studied in isolation.

Invertebrate health in marine protected areas (MPAs)

Marine protected areas (MPAs) consist of various categories of safeguarded areas in the marine environment, from semi-protected areas to total no take zones. The reported effects of MPAs are overwhelmingly positive, with numerous reports of fish size (biomass), abundance (recovery) and diversity increases, however, literature is lacking on the role and consequences of MPAs on parasite and disease dynamics, and in particular, invertebrate health. The implementation of MPAs has been known to alter trophic cascades and community dynamics, and with invertebrates commonly at the base of these systems, it is vital that their status is investigated. Overcrowding in areas closed to fishing is known to have parasitological consequences in some scenarios, and land/water use change has been known to alter host and vector communities, possibly elevating disease risk. Equally, reserves can be used as tools for alleviating impacts of marine disease. This review aims to consolidate extant literature and provide a comprehensive viewpoint on how invertebrates (and their health status) can be affected by MPAs, which are increasingly being implemented based on the relative urgency now being placed on protecting global biodiversity. In highlighting the paucity of knowledge surrounding MPAs and disease, especially that of the unenigmatic invertebrate groups, this review, published in the Special Issue on 'Invertebrates as One Health Sentinels', provides an opportunity for wide dissemination and provocation of further research in this area.

Thermal sensitivity of Bullfrog's immune response kept at different temperatures

Climate change and emerging infectious diseases are often described as the main factors associated with the worldwide amphibian population decline. In this context, rising temperatures due to global warming might act as a chronic stressor for many amphibians, leading to immunosuppression. This study aimed to characterize the thermal sensitivity of the Bullfrog's (Lithobates catesbeianus) immune response and the effect of acclimation at different temperatures on it. Plasma bacterial killing ability (BKA) and phagocytosis activity of blood leukocytes were measured at different incubation temperatures (5-40°C) in individuals kept at 28°C and 34°C. First, all individuals were held under 28°C and sampled on the 16th day. Subsequently, one group was kept at 28°, and the other one was transferred to 34°C. Both groups were sampled at 83 and 106 days of maintenance. Plasma corticosterone (CORT) and testosterone (T) were assessed to evidence thermal stress and possible endocrine correlates of immune changes over time. The incubation temperature affected BKA both on animals kept at 28°C and 34°C, with maximum values at lower temperatures (5-20°C). Phagocytosis activity was constant over the range of assay temperatures. Immune and endocrine variables decreased over time in both thermal regimes, but frogs maintained at 34°C showed lower T and immunosuppression, evidencing stress response. Therefore, exposure to high temperatures might decrease immune function in bullfrogs due to chronic stress response and by exposition to temperatures of lower performance according to the thermal sensitivity curve, which might increase vulnerability to diseases in this anuran species.

Evolution of Protein Structure and Stability in Global Warming

This review focuses on the molecular signatures of protein structures in relation to evolution and survival in global warming. It is based on the premise that the power of evolutionary selection may lead to thermotolerant organisms that will repopulate the planet and continue life in general, but perhaps with different kinds of flora and fauna. Our focus is on molecular mechanisms, whereby known examples of thermoresistance and their physicochemical characteristics were noted. A comparison of interactions of diverse residues in proteins from thermophilic and mesophilic organisms, as well as reverse genetic studies, revealed a set of imprecise molecular signatures that pointed to major roles of hydrophobicity, solvent accessibility, disulfide bonds, hydrogen bonds, ionic and π-electron interactions, and an overall condensed packing of the higher-order structure, especially in the hydrophobic regions. Regardless of mutations, specialized protein chaperones may play a cardinal role. In evolutionary terms, thermoresistance to global warming will likely occur in stepwise mutational changes, conforming to the molecular signatures, such that each "intermediate" fits a temporary niche through punctuated equilibrium, while maintaining protein functionality. Finally, the population response of different species to global warming may vary substantially, and, as such, some may evolve while others will undergo catastrophic mass extinction.

Differential Mortality and High Viral Load in Naive Pacific Oyster Families Exposed to OsHV-1 Suggests Tolerance Rather than Resistance to Infection

Pacific oysters, Crassostrea gigas, are one of the most productive aquaculture species in the world. However, they are threatened by the spread of Ostreid herpesvirus-1 (OsHV-1) and its microvariants (collectively "µvars"), which cause mass mortalities in all life stages of Pacific oysters globally. Breeding programs have been successful in reducing mortality due to OsHV-1 variants following viral outbreaks; however, an OsHV-1-resistant oyster line does not yet exist in the United States (US), and it is unknown how OsHV-1 µvars will affect US oyster populations compared to the current variant, which is similar to the OsHV-1 reference, found in Tomales Bay, CA. The goals of this study were to investigate the resistance of C. gigas juveniles produced by the Molluscan Broodstock Program (MBP) to three variants of OsHV-1: a California reference OsHV-1, an Australian µvar, and a French µvar. This is the first study to directly compare OsHV-1 µvars to a non-µvar. The survival probability of oysters exposed to the French (FRA) or Australian (AUS) µvar was significantly lower (43% and 71%, respectively) than to the reference variant and controls (96%). No oyster family demonstrated resistance to all three OsHV-1 variants, and many surviving oysters contained high copy numbers of viral DNA (mean ~3.53 × 108). These results indicate that the introduction of OsHV-1 µvars could have substantial effects on US Pacific oyster aquaculture if truly resistant lines are not achieved, and highlight the need to consider resistance to infection in addition to survival as traits in breeding programs to reduce the risk of the spread of OsHV-1 variants.

Foliar fungi and plant diversity drive ecosystem carbon fluxes in experimental prairies

Plant diversity and plant-consumer/pathogen interactions likely interact to influence ecosystem carbon fluxes but experimental evidence is scarce. We examined how experimental removal of foliar fungi, soil fungi and arthropods from experimental prairies planted with 1, 4 or 16 plant species affected instantaneous rates of carbon uptake (GPP), ecosystem respiration (R_e ) and net ecosystem exchange (NEE). Increasing plant diversity increased plant biomass, GPP and R_e , but NEE remained unchanged. Removing foliar fungi increased GPP and NEE, with the greatest effects at low plant diversity. After accounting for plant biomass, we found that removing foliar fungi increased mass-specific flux rates in the low-diversity plant communities by altering plant species composition and community-wide foliar nitrogen content. However, this effect disappeared when soil fungi and arthropods were also removed, demonstrating that both plant diversity and interactions among consumer groups determine the ecosystem-scale effects of plant-fungal interactions.

Transcriptome Analyses of Immune System Behaviors in Primary Polyp of Coral Acropora digitifera Exposed to the Bacterial Pathogen Vibrio coralliilyticus under Thermal Loading

Elevated sea surface temperature associated with global warming is a serious threat to coral reefs. Elevated temperatures directly or indirectly alter the distribution of coral-pathogen interactions and thereby exacerbate infectious coral diseases. The pathogenic bacterium Vibrio coralliilyticus is well-known as a causative agent of infectious coral disease. Rising sea surface temperature promotes the infection of corals by this bacterium, which causes several coral pathologies, such as bacterial bleaching, tissue lysis, and white syndrome. However, the effects of thermal stress on coral immune responses to the pathogen are poorly understood. To delineate the effects of thermal stress on coral immunity, we performed transcriptome analysis of aposymbiotic primary polyps of the reef-building coral Acropora digitifera exposed to V. coralliilyticus under thermal stress conditions. V. coralliilyticus infection of coral that was under thermal stress had negative effects on various molecular processes, including suppression of gene expression related to the innate immune response. In response to the pathogen, the coral mounted various responses including changes in protein metabolism, exosome release delivering signal molecules, extracellular matrix remodeling, and mitochondrial metabolism changes. Based on these results, we provide new insights into innate immunity of A. digitifera against pathogen infection under thermal stress conditions.

Deciphering Coral Disease Dynamics: Integrating Host, Microbiome, and the Changing Environment

Diseases of tropical reef organisms is an intensive area of study, but despite significant advances in methodology and the global knowledge base, identifying the proximate causes of disease outbreaks remains difficult. The dynamics of infectious wildlife diseases are known to be influenced by shifting interactions among the host, pathogen, and other members of the microbiome, and a collective body of work clearly demonstrates that this is also the case for the main foundation species on reefs, corals. Yet, among wildlife, outbreaks of coral diseases stand out as being driven largely by a changing environment. These outbreaks contributed not only to significant losses of coral species but also to whole ecosystem regime shifts. Here we suggest that to better decipher the disease dynamics of corals, we must integrate more holistic and modern paradigms that consider multiple and variable interactions among the three major players in epizootics: the host, its associated microbiome, and the environment. In this perspective, we discuss how expanding the pathogen component of the classic host-pathogen-environment disease triad to incorporate shifts in the microbiome leading to dysbiosis provides a better model for understanding coral disease dynamics. We outline and discuss issues arising when evaluating each component of this trio and make suggestions for bridging gaps between them. We further suggest that to best tackle these challenges, researchers must adjust standard paradigms, like the classic one pathogen-one disease model, that, to date, have been ineffectual at uncovering many of the emergent properties of coral reef disease dynamics. Lastly, we make recommendations for ways forward in the fields of marine disease ecology and the future of coral reef conservation and restoration given these observations.

Preparatory immunity: Seasonality of mucosal skin defences and Batrachochytrium infections in Southern leopard frogs

Accurately predicting the impacts of climate change on wildlife health requires a deeper understanding of seasonal rhythms in host-pathogen interactions. The amphibian pathogen, Batrachochytrium dendrobatidis (Bd), exhibits seasonality in incidence; however, the role that biological rhythms in host defences play in defining this pattern remains largely unknown. The aim of this study was to examine whether host immune and microbiome defences against Bd correspond with infection risk and seasonal fluctuations in temperature and humidity. Over the course of a year, five populations of Southern leopard frogs (Rana [Lithobates] sphenocephala) in Tennessee, United States, were surveyed for host immunity, microbiome and pathogen dynamics. Frogs were swabbed for pathogen load and skin bacterial diversity and stimulated to release stored antimicrobial peptides (AMPs). Secretions were analysed to estimate total hydrophobic peptide concentrations, presence of known AMPs and effectiveness of Bd growth inhibition in vitro. The diversity and proportion of bacterial reads with a 99% match to sequences of isolates known to inhibit Bd growth in vitro were used as an estimate of predicted anti-Bd function of the skin microbiome. Batrachochytrium dendrobatidis dynamics followed the expected seasonal fluctuations-peaks in cooler months-which coincided with when host mucosal defences were most potent against Bd. Specifically, the concentration and expression of stored AMPs cycled synchronously with Bd dynamics. Although microbiome changes followed more linear trends over time, the proportion of bacteria that can function to inhibit Bd growth was greatest when risk of Bd infection was highest. We interpret the increase in peptide storage in the fall and the shift to a more anti-Bd microbiome over winter as a preparatory response for subsequent infection risk during the colder periods when AMP synthesis and bacterial growth is slow and pathogen pressure from this cool-adapted fungus is high. Given that a decrease in stored AMP concentrations as temperatures warm in spring likely means greater secretion rates, the subsequent decrease in prevalence suggests seasonality of Bd in this host may be in part regulated by annual immune rhythms, and dominated by the effects of temperature.

Effects of climate change on parasites and disease in estuarine and nearshore environments

Information on parasites and disease in marine ecosystems lags behind terrestrial systems, increasing the challenge of predicting responses of marine host–parasite systems to climate change. However, here I examine several generalizable aspects and research priorities. First, I advocate that quantification and comparison of host and parasite thermal performance curves is a smart approach to improve predictions of temperature effects on disease. Marine invertebrate species are ectothermic and should be highly conducive to this approach given their generally short generation times. Second, in marine systems, shallow subtidal and intertidal areas will experience the biggest temperature swings and thus likely see the most changes to host–parasite dynamics. Third, for some responses like parasite intensity, as long as the lethal limit of the parasite is not crossed, on average, there may be a biological basis to expect temperature-dependent intensification of impacts on hosts. Fourth, because secondary mortality effects and indirect effects of parasites can be very important, we need to study temperature effects on host–parasite dynamics in a community context to truly know their bottom line effects. This includes examining climate-influenced effects of parasites on ecosystem engineers given their pivotal role in communities. Finally, other global change factors, especially hypoxia, salinity, and ocean acidity, covary with temperature change and need to be considered and evaluated when possible for their contributing effects on host–parasite systems. Climate change–disease interactions in nearshore marine environments are complex; however, generalities are possible and continued research, especially in the areas outlined here, will improve our understanding.

Information on parasites and disease in marine ecosystems lags behind terrestrial systems, increasing the challenge of predicting responses of marine host-parasite systems to climate change. This Essay highlights five general principles to guide the study of the response of marine host-parasite interactions to climate change, including the effects of temperature, oxygen, acidity, and salinity.

Some like it hotter: trematode transmission under changing temperature conditions

Climate change-related increases in temperature will influence the interactions between organisms, including the infection dynamics of parasites in ecosystems. The distribution and transmission of parasites are expected to increase with warmer temperature, but to what extent this will affect closely related parasite taxa living in sympatry is currently impossible to predict, due to our extremely limited understanding of the interspecific variation in transmission potential among parasite species in changing ecosystems. Here, we analyse the transmission patterns of four trematode species from the New Zealand mudsnail Potamopyrgus antipodarum with different life cycles and transmission strategies under two temperature scenarios, simulating current and future warmer temperatures. In a comparative experimental study, we investigated the effects of temperature on the productivity, movement and survival of the parasites' transmission stages (cercariae) to quantify the net effect of temperature on their overall transmission potential. Our results show that increases in temperature positively affect cercarial transmission dynamics, yet these impacts varied considerably between the cercariae of different trematode species, depending on their host-searching behaviour. These different species-specific transmission abilities as well as the varying individual patterns of productivity, activity and longevity are likely to have far-reaching implications for disease dynamics in changing ecosystems, since increases in temperature can shift parasite community structure. Due to the parasites' capacity to regulate the functioning of whole ecological communities and their potential impact as disease agents, understanding these species-specific parasite transmission traits remains a fundamental requirement to predict parasite dynamics under changing environmental conditions.

Nutrient and sediment loading affect multiple facets of functionality in a tropical branching coral

Coral reefs, one of the most diverse ecosystems in the world, face increasing pressures from global and local anthropogenic stressors. Therefore, a better understanding of the ecological ramifications of warming and land-based inputs (e.g. sedimentation and nutrient loading) on coral reef ecosystems is necessary. In this study, we measured how a natural nutrient and sedimentation gradient affected multiple facets of coral functionality, including endosymbiont and coral host response variables, holobiont metabolic responses and percent cover of Pocillopora acuta colonies in Mo'orea, French Polynesia. We used thermal performance curves to quantify the relationship between metabolic rates and temperature along the environmental gradient. We found that algal endosymbiont percent nitrogen content, endosymbiont densities and total chlorophyll a content increased with nutrient input, while endosymbiont nitrogen content per cell decreased, likely representing competition among the algal endosymbionts. Nutrient and sediment loading decreased coral metabolic responses to thermal stress in terms of their thermal performance and metabolic rate processes. The acute thermal optimum for dark respiration decreased, along with the maximal performance for gross photosynthetic and calcification rates. Gross photosynthetic and calcification rates normalized to a reference temperature (26.8°C) decreased along the gradient. Lastly, percent cover of P. acuta colonies decreased by nearly two orders of magnitude along the nutrient gradient. These findings illustrate that nutrient and sediment loading affect multiple levels of coral functionality. Understanding how local-scale anthropogenic stressors influence the responses of corals to temperature can inform coral reef management, particularly in relation to the mediation of land-based inputs into coastal coral reef ecosystems.

Understanding how temperature shifts could impact infectious disease

Climate change is expected to have complex effects on infectious diseases, causing some to increase, others to decrease, and many to shift their distributions. There have been several important advances in understanding the role of climate and climate change on wildlife and human infectious disease dynamics over the past several years. This essay examines 3 major areas of advancement, which include improvements to mechanistic disease models, investigations into the importance of climate variability to disease dynamics, and understanding the consequences of thermal mismatches between host and parasites. Applying the new information derived from these advances to climate-disease models and addressing the pressing knowledge gaps that we identify should improve the capacity to predict how climate change will affect disease risk for both wildlife and humans.

Exploring the association between childhood diarrhea and meteorological factors in Southwestern Ethiopia

Childhood diarrhea has been one of the major public health concerns in countries that have limited resources like Ethiopia. Understanding the association between childhood diarrhea and meteorological factors would contribute to safeguard children from adverse health effects through early warning mechanisms. Thus, this study aimed at exploring the association between childhood diarrhea and meteorological factors to enable reducing health risks. A retrospective study design was used to explore the association between meteorological factors and childhood diarrhea in southwestern Ethiopia from 2010 to 2017. Mann Kendall trend test and Spearman's correlation were computed to test the association of childhood diarrhea and meteorological factors. The space-time permutation model was used to identify the risky periods, seasons with most likely clusters, and high childhood diarrhea. Similarly, a negative binomial regression model was fitted to determine the predictability of meteorological factors for childhood diarrhea. The highest childhood diarrhea morbidity was 92.60 per 1000 per under five children. The risk of childhood diarrhea increased by 16.66% (RR: 1.1666; 95% CI: 1.164-1.168) per increase in 1 °C temperature. Furthermore, rainfall was found to be a significant risk factor of childhood diarrhea, with 0.16% (RR: 1.00167; 95% CI: 1.001306-1.001928) per 1 mm increase in rainfall. The temperature was positively correlated with the occurrence of childhood diarrhea. But the association with rainfall showed spatial variability. The space-time permutation model revealed that dry season was found to be a high-risk period with excess childhood diarrhea. The results showed that the observed association between meteorological factors and childhood diarrhea could be used as evidence for early warning systems for the prevention of childhood diarrhea.

Characterization of south central Pacific Ocean wind regimes in present and future climate for pearl farming application

In the South Pacific (SP) pearl farming atolls, wind is the main driver of lagoon water circulation, affecting dispersal and survival of pearl oyster larvae. To characterize typical wind conditions in the SP, wind regime classifications are performed from regional climate simulations using the WRF model, for present-day and for the end of the 21st century under RCP8.5 scenario conditions. At the daily time-scale, 4 regimes are identified: a trade-wind, a north-easterly, and two easterly regimes. Their characteristics are driven by large-scale circulation and climate modes of variability. In future projection, all regimes are characterized by a ~15% wind speed increase, while directions and occurrence frequencies undergo marginal changes. At the monthly time-scale that corresponds to pearl oyster pelagic larval duration, nine wind regimes are determined including three regimes with wind reversals. These regimes can be used to model typical lagoon conditions during larval dispersal.

Characterization of orange-spotted grouper (Epinephelus coioides) interferon regulatory factor 4 regulated by heat shock factor 1 during heat stress in response to antiviral immunity

Interferon regulatory factor 4 (IRF4), in conjunction with thermogenic regulation, is a negative regulator of immune responses. Therefore, we examined whether temperature changes regulated the antiviral response of IRF4 in nervous necrosis virus (NNV)-infected orange-spotted groupers. We found that osgIRF4 mRNA expression was responsive to poly I:C stimulation and NNV infection. In vitro overexpression of osgIRF4 caused a marked decrease in the promoter activity of the antiviral protein Mx1, and magnified NNV replication. Notably, we showed that the IAD domain of osgIRF4 exerted a dominant inhibitory effect on the Mx1 promoter. Furthermore, on exposure to high temperatures, the action of osgIRF4 was dependent on heat shock factor 1 (HSF1) expression. Additionally, small interfering RNA knockdown of HSF1 abrogated high temperature-mediated osgIRF4 activity. These findings suggest that osgIRF4 is an essential negative regulator of innate antiviral immunity and enhances viral replication during heat stress in the orange-spotted grouper.

Association of Short-Term Exposure to Meteorological Factors and Risk of Hand, Foot, and Mouth Disease: A Systematic Review and Meta-Analysis

(1) Background: Inconsistencies were observed in studies on the relationship between short-term exposure to meteorological factors and the risk of hand, foot, and mouth disease (HFMD). This systematic review and meta-analysis was aimed to assess the overall effects of meteorological factors on the incidence of HFMD to help clarify these inconsistencies and serve as a piece of evidence for policy makers to determine relevant risk factors. (2) Methods: Articles published as of 24 October 2020, were searched in the four databases, namely, PubMed, Web of Science, Embase, and MEDLINE. We applied a meta-analysis to assess the impact of ambient temperature, relative humidity, rainfall, wind speed, and sunshine duration on the incidence of HFMD. We conducted subgroup analyses by exposure metrics, exposure time resolution, regional climate, national income level, gender, and age as a way to seek the source of heterogeneity. (3) Results: Screening by the given inclusion and exclusion criteria, a total of 28 studies were included in the analysis. We observed that the incidence of HFMD based on the single-day lag model is significantly associated with ambient temperature, relative humidity, rainfall, and wind speed. In the cumulative lag model, ambient temperature and relative humidity significantly increased the incidence of HFMD as well. Subgroup analysis showed that extremely high temperature and relative humidity significantly increased the risk of HFMD. Temperate regions, high-income countries, and children under five years old are major risk factors for HFMD. (4) Conclusions: Our results suggest that various meteorological factors can increase the incidence of HFMD. Therefore, the general public, especially susceptible populations, should pay close attention to weather changes and take protective measures in advance.

Long-term survey of sea turtles (Caretta caretta) reveals correlations between parasite infection, feeding ecology, reproductive success and population dynamics

Long-term monitoring of host-parasite interactions is important for understanding the consequences of infection on host fitness and population dynamics. In an eight-year survey of the loggerhead sea turtle (Caretta caretta) population nesting in Cabo Verde, we determined the spatiotemporal variation of Ozobranchus margoi, a sanguivorous leech best known as a vector for sea turtle fibropapilloma virus. We quantified O. margoi association with turtles’ δ¹⁵N and δ¹³C stable isotopes to identify where infection occurs. We then measured the influence of infection on reproduction and offspring fitness. We found that parasite prevalence has increased from 10% of the population in 2010, to 33% in 2017. Stable isotope analysis of host skin samples suggests transmission occurs within the host’s feeding grounds. Interestingly, we found a significant interaction between individual size and infection on the reproductive success of turtles. Specifically, small, infected females produced fewer offspring of poorer condition, while in contrast, large, infected turtles produced greater clutch sizes and larger offspring. We interpret this interaction as evidence, upon infection, for a size-dependent shift in reproductive strategy from bet hedging to terminal investment, altering population dynamics. This link between infection and reproduction underscores the importance of using long-term monitoring to quantify the impact of disease dynamics over time.

Increasing temperatures accentuate negative fitness consequences of a marine parasite

Infectious diseases are key drivers of wildlife populations and agriculture production, but whether and how climate change will influence disease impacts remains controversial. One of the critical knowledge gaps that prevents resolution of this controversy is a lack of high-quality experimental data, especially in marine systems of significant ecological and economic consequence. Here, we performed a manipulative experiment in which we tested the temperature-dependent effects on Atlantic salmon (Salmo salar) of sea lice (Lepeophtheirus salmonis)—a parasite that can depress the productivity of wild-salmon populations and the profits of the salmon-farming industry. We explored sea-louse impacts on their hosts across a range of temperatures (10, 13, 16, 19, and 22 °C) and infestation levels (zero, ‘low’ (mean abundance ± SE = 1.6 ± 0.1 lice per fish), and ‘high’ infestation (6.8 ± 0.4 lice per fish)). We found that the effects of sea lice on the growth rate, condition, and survival of juvenile Atlantic salmon all worsen with increasing temperature. Our results provide a rare empirical example of how climate change may influence the impacts of marine disease in a key social-ecological system. These findings underscore the importance of considering climate-driven changes to disease impacts in wildlife conservation and agriculture.

Micro- and Macroenvironmental Conditions and Stability of Terrestrial Models

Environmental variables can have profound effects on the biological responses of research animals and the outcomes of experiments dependent on them. Some of these influences are both predictable and unpredictable in effect, many are challenging to standardize, and all are influenced by the planning and conduct of experiments and the design and operation of the vivarium. Others are not yet known. Within the immediate environment where the research animal resides, in the vivarium and in transit, the most notable of these factors are ambient temperature, relative humidity, gaseous pollutant by-products of animal metabolism and physiology, dust and particulates, barometric pressure, electromagnetic fields, and illumination. Ambient temperatures in the animal housing environment, in particular those experienced by rodents below the thermoneutral zone, may introduce degrees of stress and thermoregulatory compensative responses that may complicate or invalidate study measurements across a broad array of disciplines. Other factors may have more subtle and specific effects. It is incumbent on scientists designing and executing experiments and staff responsible for animal husbandry to be aware of, understand, measure, systematically record, control, and account for the impact of these factors on sensitive animal model systems to ensure the quality and reproducibility of scientific studies.

Connectivity over a disease risk gradient enables recovery of rainforest frogs

Chytridiomycosis has been a key driver of global frog declines and extinctions, particularly for high-altitude populations across Australia and the Americas. While recent evidence shows some species are recovering, the extent of such recoveries and the mechanisms underpinning them remain poorly resolved. We surveyed the historical latitudinal and elevational range of four Australian rainforest frogs that disappeared from upland sites between 1989 and 1994 to establish their contemporary distribution and elevational limits, and investigate factors affecting population recovery. Five rainforest streams were surveyed from mountain-base to summit (30 sites in total), with swabs collected from the target species (Litoria dayi, L. nannotis, L. rheocola, and L. serrata) to determine their infection status, and data loggers deployed to measure microclimatic variation across the elevational gradient. Infection probability increased with elevation and canopy cover as it was tightly and inversely correlated with stream-side air temperature. Occupancy patterns suggest varying responses to this disease threat gradient. Two species, L. rheocola and L. serrata, were found over their full historical elevational range (≥1,000 m above sea level [asl]), while L. dayi was not detected above 400 m (formerly known up to 900 m asl) and L. nannotis was not detected above 800 m (formerly known up to 1,200 m asl). Site occupancy probability was negatively related to predicted infection prevalence for L. dayi, L. nannotis, and L. rheocola, but not L. serrata, which appears to now tolerate high fungal burdens. This study highlights the importance of environmental refuges and connectivity across disease risk gradients for the persistence and natural recovery of frogs susceptible to chytridiomycosis. Likewise, in documenting both interspecific variation in recovery rates and intraspecific differences between sites, this study suggests interactions between disease threats and host selection exist that could be manipulated. For example, translocations may be warranted where connectivity is poor or the increase in disease risk is too steep to allow recolonization, combined with assisted selection or use of founders from populations that have already undergone natural selection.

Microbiome dynamics and genomic determinants of bovine mastitis

The milk of lactating cows presents a complex ecosystem of interconnected microbial communities which can influence the pathophysiology of mastitis. We hypothesized possible dynamic shifts of microbiome composition and genomic features with different pathological conditions of mastitis (Clinical Mastitis; CM, Recurrent CM; RCM, Subclinical Mastitis; SCM). To evaluate this hypothesis, we employed whole metagenome sequencing (WMS) in 20 milk samples (CM, 5; RCM, 6; SCM, 4; H, 5) to unravel the microbiome dynamics, interrelation, and relevant metabolic functions. The WMS data mapped to 442 bacterial, 58 archaeal and 48 viral genomes with distinct variation in microbiome composition (CM > H > RCM > SCM). Furthermore, we identified a number of microbial genomic features, including 333, 304, 183 and 50 virulence factors-associated genes (VFGs) and 48, 31, 11 and 6 antibiotic resistance genes (ARGs) in CM, RCM, SCM, and H-microbiomes, respectively. We also detected different metabolic pathway and functional genes associated with mastitis pathogenesis. Therefore, profiling microbiome dynamics in different conditions of mastitis and associated microbial genomic features contributes to developing microbiome-based diagnostics and therapeutics for bovine mastitis.

Using Digital Image Analysis to Quantify Small Arthropod Vectors

Quantifying arthropod vectors can be a time-consuming process. Here, we describe a technique to count large samples of small arthropods using ImageJ. ImageJ is an open source image processing software, produced by the National Institutes of Health, with a straightforward interface that has proven useful in quantifying small organisms (i.e., cells, pollen, eggs). In 2017, we deployed CDC light traps baited with carbon dioxide among seven sites to capture black flies (Diptera: Simuliidae). Samples of the captured specimens were photographed, and then quantified manually and automatically, using ImageJ. We compared the accuracy of three types of automated counts to manual counts of black flies using an information-theoretic approach. We found that changing the particle size produced counts closest to those obtained by manual counts. Even over a large range of values, from tens to thousands of flies, our automated counts were often identical to and almost always within 5% of the manual counts. When different, automated counts were usually slightly less than manual counts, and thus conservative estimates. This automated technique is simple, repeatable, requires minimal training, and can reduce the time needed to quantify small arthropods such as black flies.

Temperature-parasite interaction: do trematode infections protect against heat stress?

Blue mussels (Mytilus edulis) are important ecosystem engineers along Atlantic coastlines, where they are regularly subjected to rapid changes in temperature during the transition between tides. Global climate change and more frequent extreme weather events are expected to intensify this thermal stress even further. These increases in temperatures will not only affect intertidal mussels directly but also increase transmission dynamics of their parasites. Together, the effects of rises in temperature and parasitism will likely result in higher pressure on M. edulis and their ability to perform vital ecosystem services. In a set of experiments, we tested the effects of infections with the trematode Himasthla elongata and high temperatures during low tide air-exposure. Overall, we hypothesised that temperature and parasite infection intensity would each have significant negative effects on M. edulis survival, and that both stressors together would have a synergistic detrimental impact. Overall, high temperature levels had a strong negative effect on mussel survival. However, our results revealed a surprisingly more complex picture in infected individuals. While moderate parasite loads and increased temperature showed additive negative effects on mussel survival, high parasite infection intensities appeared to nullify the detrimental effects of temperature stress on mussels. Under climate warming, these benefits of parasites might actually outweigh the costs of infection and prove beneficial. Overall, these results suggest that the interactions between host-parasite systems and their changing environment are much more complex than a simple additive effect of multiple stressors.

The Ecological Importance of Amphipod–Parasite Associations for Aquatic Ecosystems

Amphipods are a key component of aquatic ecosystems due to their distribution, abundance and ecological role. They also serve as hosts for many micro- and macro-parasites. The importance of parasites and the necessity to include them in ecological studies has been increasingly recognized in the last two decades by ecologists and conservation biologists. Parasites are able to alter survival, growth, feeding, mobility, mating, fecundity and stressors’ response of their amphipod hosts. In addition to their modulating effects on host population size and dynamics, parasites affect community structure and food webs in different ways: by increasing the susceptibility of amphipods to predation, by quantitatively and qualitatively changing the host diet, and by modifying competitive interactions. Human-induced stressors such as climate change, pollution and species introduction that affect host–parasite equilibrium, may enhance or reduce the infection effects on hosts and ecosystems. The present review illustrates the importance of parasites for ecosystem processes using examples from aquatic environments and amphipods as a host group. As seen from the literature, amphipod–parasite systems are likely a key component of ecological processes, but more quantitative data from natural populations and field evidence are necessary to support the results obtained by experimental research.