Parasite Tolerance Research Articles

Transient Adaptation of Toxoplasma gondii to Exposure by Thiosemicarbazone Drugs That Target Ribosomal Proteins Is Associated with the Upregulated Expression of Tachyzoite Transmembrane Proteins and Transporters.

Thiosemicarbazones and their metal complexes have been studied for their biological activities against bacteria, cancer cells and protozoa. Short-term in vitro treatment with one gold (III) complex (C3) and its salicyl-thiosemicarbazone ligand (C4) selectively inhibited proliferation of T. gondii. Transmission Electron Microscopy (TEM) detected transient structural alterations in the parasitophorous vacuole membrane and the tachyzoite cytoplasm, but the mitochondrial membrane potential appeared unaffected by these compounds. Proteins potentially interacting with C3 and C4 were identified using differential affinity chromatography coupled with mass spectrometry (DAC-MS). Moreover, long-term in vitro treatment was performed to investigate parasitostatic or parasiticidal activity of the compounds. DAC-MS identified 50 ribosomal proteins binding both compounds, and continuous drug treatments for up to 6 days caused the loss of efficacy. Parasite tolerance to both compounds was, however, rapidly lost in their absence and regained shortly after re-exposure. Proteome analyses of six T. gondii ME49 clones adapted to C3 and C4 compared to the non-adapted wildtype revealed overexpression of ribosomal proteins, of two transmembrane proteins involved in exocytosis and of an alpha/beta hydrolase fold domain-containing protein. Results suggest that C3 and C4 may interfere with protein biosynthesis and that adaptation may be associated with the upregulated expression of tachyzoite transmembrane proteins and transporters, suggesting that the in vitro drug tolerance in T. gondii might be due to reversible, non-drug specific stress-responses mediated by phenotypic plasticity.

No evidence of adaptive tolerance of parasitism in a cavity-nesting brood parasite host

Abstract Acceptance of avian brood parasitism by hosts is one of the most enigmatic aspects of brood parasite–host coevolution. The most common explanation for acceptance of parasitism by hosts of the brown-headed cowbird (Molothrus ater) is evolutionary lag, which suggests that hosts have not had enough time to evolve defenses against parasitism. Alternatively, acceptance may be the optimal strategy when the costs of rejecting parasitism exceed the benefits. The lack of nest site hypothesis applies to secondary cavity-nesting birds that cannot excavate their own nests and predicts that hosts accept parasitism instead of deserting a parasitized nest when there are no vacant nest sites available in which to renest. I tested this hypothesis using the prothonotary warbler (Pronotaria citrea), a commonly parasitized, cavity-nesting cowbird host. I used a paired nest box design and predicted that if hosts accept parasitism because of a lack of alternative nest sites, they should desert parasitized nests and renest in the vacant nest box on their territory. I recorded 37 cases where a nest was parasitized and warblers only deserted 2 parasitized nest boxes for a vacant nest box. Both desertions were attributable to factors other than parasitism and the rate of desertion did not differ from controls that only had a single nest box. Moreover, 7 of the warblers initiated clutches in nest boxes that already contained cowbird egg despite having vacant nest boxes available on their territories. These results indicate that warblers do not accept parasitism because of tolerance, but likely due to evolutionary lag.

Do sexual differences in life strategies make male lizards more susceptible to parasite infection?

Female and male hosts may maximise their fitness by evolving different strategies to compensate for the costs of parasite infections. The resulting sexual dimorphism might be apparent in differential relationships between parasite load and body condition, potentially reflecting differences in energy allocation to anti-parasitic defences. For example, male lacertids with high body condition may produce many offspring while being intensely parasitised. In contrast, female lacertids may show a different outcome of the trade-offs between body condition and immunity, aiming to better protect themselves from the harm of parasites. We predicted that females would have fewer parasites than males and a lower body condition across parasitaemia levels because they would invest resources in parasite defence to mitigate the costs of infection. In contrast, the male strategy to maximise access to females would imply some level of parasite tolerance and, thus, higher parasitaemia. We analysed the relationship between the body condition of lizards and the parasitemias of Karyolysus and Schellackia, two genera of blood parasites with different phylogenetic origins, in 565 females and 899 males belonging to 10 species of the Lacertidae (Squamata). These lizards were sampled over a period of 12 years across 34 sampling sites in southwestern Europe. The results concerning the Karyolysus infections were consistent with the predictions, with males having similar body condition across parasitaemia levels even though they had higher infection intensities than females. On the other hand, females with higher levels of Karyolysus parasitaemia had lower body condition. This is consistent with the prediction that different life strategies of male and female lacertids can explain the infection patterns of Karyolysus. In contrast, the parasitaemia of Schellackia was consistently low in both male and female hosts, with no significant effect on the body condition of lizards. This suggests that lizards of both sexes maintain this parasite below a pathogenic threshold.

Effects of predation risk on parasite-host interactions and wildlife diseases.

Landscapes of fear can determine the dynamics of entire ecosystems. In response to perceived predation risk, prey can show physiological, behavioral, or morphological trait changes to avoid predation. This in turn can indirectly affect other species by modifying species interactions (e.g., altered feeding), with knock-on effects, such as trophic cascades, on the wider ecosystem. While such indirect effects stemming from the fear of predation have received extensive attention for herbivore-plant and predator-prey interactions, much less is known about how they alter parasite-host interactions and wildlife diseases. In this synthesis, we present a conceptual framework for how predation risk-as perceived by organisms that serve as hosts-can affect parasite-host interactions, with implications for infectious disease dynamics. By basing our approach on recent conceptual advances with respect to predation risk effects, we aim to expand this general framework to include parasite-host interactions and diseases. We further identify pathways through which parasite-host interactions can be affected, for example, through altered parasite avoidance behavior or tolerance of hosts to infections, and discuss the wider relevance of predation risk for parasite and host populations, including heuristic projections to population-level dynamics. Finally, we highlight the current unknowns, specifically the quantitative links from individual-level processes to population dynamics and community structure, and emphasize approaches to address these knowledge gaps.

Current Therapeutic Strategies for Chagas Disease

Abstract: Trypanosoma cruzi, the parasite that causes Chagas disease, can only be cured with one of two drugs, benznidazole or nifurtimox. The main disadvantages of these drugs include their ineffectiveness outside of the acute or early infection phase, their unpleasant effects, and the parasite's tolerance to their activities. On the other hand, several institutions and research groups have been working on a number of ways that can help find a solution to the problem. These strategies have evolved over the last few years. Several examples of such advancements include the utilization of combination therapy, the repurposing of current treatments, and the change of dosages for traditional drugs. Research has also been conducted on antiparasitic plants and the substances that may be obtained from them, and it makes use of existing knowledge gathered through medical procedures. Some works have studied the parasite in order to identify important genes that have the potential to be used as therapeutic targets in the development of novel targeted medications. Even though a lot of these studies have shown promising results, only a small fraction of them make it to the clinical testing phase of the study. Institutions and research organizations should be rewarded for coordinating their efforts and addressing all areas of drug development, given their resources and information. Last but not least, distributing this information will result in novel Chagas disease therapies, which would assist impacted populations.

Oxidative stress changes the effectiveness of artemisinin in Plasmodium falciparum.

Emerging resistance to the frontline antimalarial drug artemisinin represents a significant threat to worldwide malaria control and elimination. The patterns of parasite changes associated with emerging resistance represent a complex array of metabolic processes evident in various genetic mutations and altered transcription profiles. Genetic factors identified in regulating P. falciparum sensitivity to artemisinin overlap with the parasite's responses to malarial fever, sickle trait, and other types of oxidative stresses, suggesting conserved inducible survival responses. In this study we show that intraerythrocytic stress conditions, oxidative stress and heat shock, can significantly decrease the sensitivity of the parasite to artemisinin and lumefantrine, respectively. These results indicate that an intraerythrocytic oxidative stress microenvironment and heat-shock condition can alter antimalarial drug efficacy. Evaluating efficacy of antimalarial drugs under ideal in vitro culture conditions may not accurately predict drug efficacy in all malaria patients.

Parasite Fauna and Coinfections in Urban Rats Naturally Infected by the Zoonotic Parasite Angiostrongylus cantonensis.

When the zoonotic parasite of rodents that can cause human neuroangiostrongyliasis, i.e., Angiostrongylus cantonensis, is found in its natural definitive hosts, it is usually reported in isolation, as if the rat lungworm were the only component of its parasite community. In this study, we report the coinfections found in rats naturally infected by A. cantonensis in urban populations of Rattus norvegicus and Rattus rattus in Valencia, Spain. In addition to the rat lungworms, which were found in 14 of the 125 rats studied (a prevalence of 11.20%), 18 other parasite species (intestinal and tissular protists, microsporidia and helminths) were found, some of them with high burdens. Fourteen of these nineteen species found are potential zoonotic parasites, namely Blastocystis, Giardia duodenalis, Cryptosporidium spp., Enterocytozoon bieneusi, Encephalitozoon hellem, Toxoplasma gondii, Brachylaima spp., Hydatigera taeniaeformis s.l. larvae, Hymenolepis nana, Hymenolepis diminuta, Angiostrongylus cantonensis, Calodium hepaticum, Gongylonema neoplasticum and Moniliformis moniliformis. The total predominance of coinfected rats as well as their high parasite loads seem to indicate a trend towards parasite tolerance.

Hair sheep in the Americas: economic traits and sustainable production

The relevance of hair sheep and their place in animal agriculture in the United States is expanding. Fueled by the exigency of sustainable agricultural practices, the integration of hair sheep to replace their wool breed counterparts is essential. Approximately 10% of all sheep globally are hair sheep but they are growing in numbers and production each year. Hair sheep breeds are widely diverse but share a common origin in tropical countries. Most of the prominent breeds were mindfully developed and crossed with wool breeds (namely, the Mouflon sheep) to improve the economically important traits of the animal. This genetic development has proven successful; hair sheep are considered highly advantageous in carcass quality, meat taste, litter size, and leather quality. Aside from those economically important traits, hair sheep are also advantageous in production traits, such as parasitic resistance, disease resistance, heat tolerance, sperm quality, and nutritional efficiency. These identified traits of hair sheep are highly desirable and contribute to the hair sheep’s positive reputation. However, hair sheep pose some disadvantages, such as an average or below average scrotal circumference, lower meat yield (although high in quality), meat with higher cholesterol than that of the wool breeds, and the lack of wool leaving the hair sheep susceptible to cold stress. These disadvantages can be mitigated with genetic selection and production techniques. The importance to further developing hair sheep is irrefutable. This review focuses on the fundamental and applied science of the most common hair sheep breeds and is expected to be useful for students, scientists, and producers of hair sheep.

High temperatures augment inhibition of parasites by a honey bee gut symbiont.

Temperature affects growth, metabolism, and interspecific interactions in microbial communities. Within animal hosts, gut bacterial symbionts can provide resistance to parasitic infections. Both infection and populations of symbionts can be shaped by the host body temperature. However, the effects of temperature on the antiparasitic activities of gut symbionts have seldom been explored. The Lactobacillus-rich gut microbiota of facultatively endothermic honey bees is subject to seasonal and ontogenetic changes in host temperature that could alter the effects of symbionts against parasites. We used cell cultures of a Lactobacillus symbiont and an important trypanosomatid gut parasite of honey bees to test the potential for temperature to shape parasite-symbiont interactions. We found that symbionts showed greater heat tolerance than parasites and chemically inhibited parasite growth via production of acids. Acceleration of symbiont growth and acid production at high temperatures resulted in progressively stronger antiparasitic effects across a temperature range typical of bee colonies. Consequently, the presence of symbionts reduced both the peak growth rate and heat tolerance of parasites. Substantial changes in parasite-symbiont interactions were evident over a temperature breadth that parallels changes in diverse animals exhibiting infection-related fevers and the amplitude of circadian temperature variation typical of endothermic birds and mammals, implying the frequent potential for temperature to alter symbiont-mediated resistance to parasites in endo- and ectothermic hosts. Results suggest that the endothermic behavior of honey bees could enhance the impacts of gut symbionts on parasites, implicating thermoregulation as a reinforcer of core symbioses and possibly microbiome-mediated antiparasitic defense. IMPORTANCE Two factors that shape the resistance of animals to infection are body temperature and gut microbiota. However, temperature can also alter interactions among microbes, raising the question of whether and how temperature changes the antiparasitic effects of gut microbiota. Honey bees are agriculturally important hosts of diverse parasites and infection-mitigating gut microbes. They can also socially regulate their body temperatures to an extent unusual for an insect. We show that high temperatures found in honey bee colonies augment the ability of a gut bacterial symbiont to inhibit the growth of a common bee parasite, reducing the parasite's ability to grow at high temperatures. This suggests that fluctuations in colony and body temperatures across life stages and seasons could alter the protective value of bees' gut microbiota against parasites, and that temperature-driven changes in gut microbiota could be an underappreciated mechanism by which temperature-including endothermy and fever-alters animal infection.

Population-level variation in insecticide tolerance across three life stages of the trematode Echinostoma trivolvis

Ecotoxicological studies using single test populations may miss the inherent variation of natural systems and limit our understanding of how contaminants affect focal species. Though population-level variation in pesticide tolerance is commonly observed in host taxa, few studies have assessed population-level differences in the tolerance of parasites to different contaminants. We investigated population-level variation in insecticide tolerance of three Echinostoma trivolvis life stages (egg, miracidium, and cercaria) to three insecticides (carbaryl, chlorpyrifos, and diazinon). We tested two relevant metrics of insecticide tolerance—baseline and induced—across up to eight different parasite populations per life stage. Across all life stages, the insecticide treatments tended to reduce survival, but the magnitude of their effects often varied significantly among populations. Surprisingly, we found that exposure to chlorpyrifos increased the hatching success of echinostome eggs relative to the control treatment in three of six tested populations. We also found that cercariae shed from snails previously exposed to a sublethal concentration of chlorpyrifos had a significantly lower mortality rate when subsequently exposed to a lethal concentration of chlorpyrifos relative to individuals from snails that were not previously exposed; this suggests inducible tolerance in cercariae. We found no evidence that insecticide tolerance is correlated across parasite life stages within a population. Together the findings of our study demonstrate that single-population toxicity assays may greatly over- or underestimate the effects of pesticides on the survival of free-living parasite stages, insecticide tolerance levels may not be predictable from one parasite life stage to the next, and insecticides can have both expected and counterintuitive effects on non-target taxa.

15 Search for Non-Genomic Markers as Puberty Predictors inBos Indicus Cattle

Abstract Brahman cattle are used for crossbreeding due to their maternal ability, heat, and parasite tolerance. Brahman displays delayed attainment of puberty compared with taurine breeds. The objective was to identify molecular markers in the blood of prepubertal heifers and bulls that predict early puberty attainment. We hypothesize that Brahmans that attains puberty have a blood metabolite signature that differs from animals that remain prepubertal. Plasma was collected 90 (-90d) and 30 (-30d) days prior to the beginning of the breeding season from 156 yearling Brahman heifers and 28 bulls. Animals were classified as pubertal (pub) or prepubertal (prepub) based on reproductive variables such as the reproductive tract score and pregnancy to insemination for heifers and scrotal circumference and semen quality for bulls. Plasma from 48 pub and 48 prepub heifers and 9 pub and 7 prepub bulls were submitted for quantitative mass spectrometry metabolomics analysis. There was a clear clustering of animals according to puberty status (orthogonal projections of latent structures discriminant analysis). Concentrations of the top three metabolites explaining clustering were analyzed by t-tests. As heifers approached maturity, there was a 3.03-, 11.76- and 2.08-fold change (P < 0.0001) in the concentrations of PC ae C42:3, ProBetaine, and PC ae C42:2 measured at -30 vs. -90 days. Similarly, for bulls, concentrations of HipAcid, C4 and SM (OH) C24:1 were 1.52-, 1.53-, and 1.45-fold greater (P < 0.0001), respectively. Comparing pub vs. prebub heifers on -90 d, there was a 1.26- (P < 0.001), 0.62- (P < 0.01) and 1.11-fold change (P < 0.05) for hArg, Putrescine and AABA concentrations, respectively. Regarding bulls on -90 d, there was a 1.57- (P < 0.01), 1.32- (P < 0.03) and 1.15-fold change (P < 0.03) for FA(18:1), FA(18:2) and DG(16:1_18:2) concentrations, respectively. In conclusion, we discovered potential markers for the prediction of puberty attainment based on plasma metabolomic signatures in Brahman.

Sequence of introduction determines the success of contrasting root symbionts and their host

Many crop species play host to a diverse range of soil-borne symbionts ranging from parasitic, such as potato cyst nematodes (PCN), to mutualistic, including arbuscular mycorrhizal fungi (AMF). Each of these organisms may establish symbiosis with the host prior to the arrival of another which may impact the fitness of all parties involved. We simulated a range of arrival time scenarios for both AMF and PCN and determined their consequences on potato host plants and subsequent symbionts to reflect the likely complexity of symbioses that occur in the field. Simulations were focussed on the first few weeks of plant growth to identify the importance of symbiont interactions during early plant development. Our data indicate that the order in which symbionts are introduced to crop roots is not only important for their own success, but also for that of the host and its additional symbionts. The presence of AMF increased the PCN population on the host, with earlier introduction of AMF increasing the magnitude of the effect. However, presence of AMF also increased the potato's tolerance to PCN, ameliorating the negative effects of the increased PCN burden. This tolerance was stronger the earlier the AMF were introduced and was sustained even when AMF were introduced after PCN. Overall, we show that the initial few weeks of crop emergence and growth may reflect a window of opportunity where the prosperity of the crop and its tolerance of parasites can potentially be influenced by coordinating application of AMF propagules. Additionally, these timings impact the success of below-ground plant parasites that can persist and impact crops for several years.

Host Developmental Stage Effects on Parasite Resistance and Tolerance.

AbstractHosts can defend themselves against parasites either by preventing or limiting infections (resistance) or by limiting parasite-induced damage (tolerance). However, it remains underexplored how these defense types vary over host development with shifting patterns of resource allocation priorities. Here, we studied the role played by developmental stage in resistance and tolerance in Atlantic salmon (Salmo salar). This anadromous fish has distinct life stages related to living in freshwater and seawater. We experimentally exposed 1-year-old salmon, either at the freshwater stage or at the stage transitioning to the marine phase, to the trematode Diplostomum pseudospathaceum. Using 56 pedigreed families and multivariate animal models, we show that developmental transition is associated with reduced resistance but does not affect tolerance. Furthermore, by comparing tolerance slopes (host fitness against parasite load) based on additive genetic effects among infected and unexposed control relatives, we observed that the slopes can be largely independent of the infection, that is, they may not reflect tolerance. Together, our results suggest that the relative importance of different defense types may vary with host development and emphasize the importance of including control treatments for more confident interpretations of tolerance estimates.

Naturally Acquired Kelch13 Mutations in Plasmodium falciparum Strains Modulate In Vitro Ring-Stage Artemisinin-Based Drug Tolerance and Parasite Survival in Response to Hyperoxia.

ABSTRACTThe ring-stage survival assay was utilized to assess the impact of physiological hyperoxic stress on dihydroartemisinin (DHA) tolerance for a panel of Plasmodium falciparum strains with and without Kelch13 mutations. Strains without naturally acquired Kelch13 mutations or the postulated genetic background associated with delayed parasite clearance time demonstrated reduced proliferation under hyperoxic conditions in the subsequent proliferation cycle. Dihydroartemisinin tolerance in three isolates with naturally acquired Kelch13 mutations but not two genetically manipulated laboratory strains was modulated by in vitro hyperoxic stress exposure of early-ring-stage parasites in the cycle before drug exposure. Reduced parasite tolerance to additional derivatives, including artemisinin, artesunate, and OZ277, was observed within the second proliferation cycle. OZ439 and epoxomicin completely prevented parasite survival under both hyperoxia and normoxic in vitro culture conditions, highlighting the unique relationship between DHA tolerance and Kelch13 mutation-associated genetic background.IMPORTANCE Artemisinin-based combination therapy (ACT) for treating malaria is under intense scrutiny following treatment failures in the Greater Mekong subregion of Asia. This is further compounded by the potential for extensive loss of life if treatment failures extend to the African continent. Although Plasmodium falciparum has become resistant to all antimalarial drugs, artemisinin “resistance” does not present in the same way as resistance to other antimalarial drugs. Instead, a partial resistance or tolerance is demonstrated, associated with the parasite’s genetic profile and linked to a molecular marker referred to as K13. It is suggested that parasites may have adapted to drug treatment, as well as the presence of underlying population health issues such as hemoglobinopathies, and/or environmental pressures, resulting in parasite tolerance to ACT. Understanding parasite evolution and control of artemisinin tolerance will provide innovative approaches to mitigate the development of artemisinin tolerance and thereby artemisinin-based drug treatment failure and loss of life globally to malaria infections.

Great-tailed Grackles (Quiscalus mexicanus) as a tolerant host of avian malaria parasites.

Great-tailed Grackles (Quiscalus mexicanus) are a social, polygamous bird species whose populations have rapidly expanded their geographic range across North America over the past century. Before 1865, Great-tailed Grackles were only documented in Central America, Mexico, and southern Texas in the USA. Given the rapid northern expansion of this species, it is relevant to study its role in the dynamics of avian blood parasites. Here, 87 Great-tailed grackles in Arizona (a population in the new center of the range) were screened for haemosporidian parasites using microscopy and PCR targeting the parasite mitochondrial cytochrome b gene. Individuals were caught in the wild from January 2018 until February 2020. Haemosporidian parasite prevalence was 62.1% (54/87). A high Plasmodium prevalence was found (60.9%, 53/87), and one grackle was infected with Haemoproteus (Parahaemoproteus) sp. (lineage SIAMEX01). Twenty-one grackles were infected with P. cathemerium, sixteen with P. homopolare, four with P. relictum (strain GRW04), and eleven with three different genetic lineages of Plasmodium spp. that have not been characterized to species level (MOLATE01, PHPAT01, and ZEMAC01). Gametocytes were observed in birds infected with three different Plasmodium lineages, revealing that grackles are competent hosts for some parasite species. This study also suggests that grackles are highly susceptible and develop chronic infections consistent with parasite tolerance, making them competent to transmit some generalist haemosporidian lineages. It can be hypothesized that, as the Great-tailed Grackle expands its geographic range, it may affect local bird communities by increasing the transmission of local parasites but not introducing new species into the parasite species pool.

Vertical Oxide Channel Thin Film Transistor for Ultra-High-Resolution Display

The significance of backplane devices for ultra-high-resolution (UHR) display has increased with the recent development of augmented reality (AR) and virtual reality (VR) devices. Since the human visual resolution can distinguish up to 60 pixels per degree (PPD), the AR/VR device panel needs at least 3000 pixels per inch (PPI) to exceed the human retina resolution limit for clear display without screen effect. As a results, the unit pixel pitch of thin film transistor (TFT) for UHR display should be not only smaller than a few micrometers (~3 μm), TFT channel length should also be sub-micrometers level. In active matrix organic light emitting diode (AMOLED) display type, self-aligned top gate (SATG) TFT has been widely used as a planar backplane device structure because of its low parasitic capacitance and tolerance of illumination degradation caused by the light from emitting layer [1-2]. However, SATG TFT has fundamental disadvantages for device miniaturization due to its essentially required area of metallization region for reducing contact resistance and scaling limit of channel induced by carrier diffusion shrinking effective channel length. For this reason, we suggested a size tunable oxide channel VTFT structure that can achieve a high pixel density on account of structural benefit on device footprint.In this work, we fabricated amorphous indium gallium zinc oxide (a-IGZO) based VTFT. The previously published VTFT structure, channel length is determined by the thickness of spacer between source and drain electrodes [3]. Owing to spacer etching process, uneven backchannel roughness and high off current has become well-known issues of VTFT. On the contrary, the proposed VTFT structure has a controllability of effective channel aspect ratio because source and drain electrodes are able to be patterned by photolithography process. Furthermore, the parasitic capacitance is also relatively less than the formerly reported VTFTs controlled by inevitable thickness limit structurally due to the electrodes.To sum up, we not only realized the oxide channel VTFT that meets high performance for AR/VR display, but opened new application possibility to UHR electronic devices platform. Figure 1. (a) Schematic of the proposed VTFT (b) Transfer characteristic of VTFT Acknowledgement This work was supported by the Korea Evaluation Institute of Industrial Technology(KEIT) grant funded by the Korea government (MOTIE) (No. 2021-11-1283) References Kang, Dong Han, et al. "Self-aligned coplanar a-IGZO TFTs and application to high-speed circuits." IEEE electron device letters 32.10 (2011): 1385-1387.Wang, Guoying, et al. "8.3: High Stability Against Light and Heat Based on the Top Gate Self‐Aligned a‐IGZO TFTs under OLED Dislplay." SID Symposium Digest of Technical Papers. Vol. 49. 2018.Petti, Luisa, et al. "Flexible quasi-vertical In-Ga-Zn-O thin-film transistor with 300-nm channel length." IEEE Electron Device Letters36.5 (2015): 475-477. Figure 1

Access to Cleaning Services Alters Fish Physiology Under Parasite Infection and Ocean Acidification.

Cleaning symbioses are key mutualistic interactions where cleaners remove ectoparasites and tissues from client fishes. Such interactions elicit beneficial effects on clients’ ecophysiology, with cascading effects on fish diversity and abundance. Ocean acidification (OA), resulting from increasing CO2 concentrations, can affect the behavior of cleaner fishes making them less motivated to inspect their clients. This is especially important as gnathiid fish ectoparasites are tolerant to ocean acidification. Here, we investigated how access to cleaning services, performed by the cleaner wrasse Labroides dimidiatus, affect individual client’s (damselfish, Pomacentrus amboinensis) aerobic metabolism in response to both experimental parasite infection and OA. Access to cleaning services was modulated using a long-term removal experiment where cleaner wrasses were consistently removed from patch reefs around Lizard Island (Australia) for 17 years or left undisturbed. Only damselfish with access to cleaning stations had a negative metabolic response to parasite infection (maximum metabolic rate—ṀO2Max; and both factorial and absolute aerobic scope). Moreover, after an acclimation period of 10 days to high CO2 (∼1,000 µatm CO2), the fish showed a decrease in factorial aerobic scope, being the lowest in fish without the access to cleaners. We propose that stronger positive selection for parasite tolerance might be present in reef fishes without the access to cleaners, but this might come at a cost, as readiness to deal with parasites can impact their response to other stressors, such as OA.

Parasite resistance and parasite tolerance: insights into transgenerational immune priming in an invertebrate host.

Parasites impose different selection regimes on their hosts, which respond by increasing their resistance and/or tolerance. Parental challenge with parasites can enhance the immune response of their offspring, a phenomenon documented in invertebrates and termed transgenerational immune priming. We exposed two parental generations of the model organism Daphnia magna to the horizontally transmitted parasitic yeast Metschnikowia bicuspidata and recorded resistance- and tolerance-related traits in the offspring generation. We hypothesized that parentally primed offspring will increase either their resistance or their tolerance to the parasite. Our susceptibility assays revealed no impact of parental exposure on offspring resistance. Nonetheless, different fitness-related traits, which are indicative of tolerance, were altered. Specifically, maternal priming increased offspring production and decreased survival. Grandmaternal priming positively affected age at first reproduction and negatively affected brood size at first reproduction. Interestingly, both maternal and grandmaternal priming significantly reduced within-host–parasite proliferation. Nevertheless, Daphnia primed for two consecutive generations had no competitive advantage in comparison to unprimed ones, implying additive maternal and grandmaternal effects. Our findings do not support evidence of transgenerational immune priming from bacterial infections in the same host species, thus, emphasizing that transgenerational immune responses may not be consistent even within the same host species.

Punch in the gut: parasite tolerance of phytochemicals reflects host diet.

Gut parasites of plant-eating insects are exposed to antimicrobial phytochemicals that can reduce infection. Trypanosomatid gut parasites infect insects of diverse nutritional ecologies as well as mammals and plants, raising the question of how host diet-associated phytochemicals shape parasite evolution and host specificity. To test the hypothesis that phytochemical tolerance of trypanosomatids reflects the chemical ecology of their hosts, we compared related parasites from honey bees and mosquitoes - hosts that differ in phytochemical consumption - and contrasted our results with previous studies on phylogenetically related, human-parasitic Leishmania. We identified one bacterial and 10 plant-derived substances with known antileishmanial activity that also inhibited honey bee parasites associated with colony collapse. Bee parasites exhibited greater tolerance of chrysin - a flavonoid found in nectar, pollen and plant resin-derived propolis. In contrast, mosquito parasites were more tolerant of cinnamic acid - a product of lignin decomposition present in woody debris-rich larval habitats. Parasites from both hosts tolerated many compounds that inhibit Leishmania, hinting at possible trade-offs between phytochemical tolerance and mammalian infection. Our results implicate the phytochemistry of host diets as a potential driver of insect-trypanosomatid associations and identify compounds that could be incorporated into colony diets or floral landscapes to ameliorate infection in bees.

The behaviour of infected guppies depends on social context, parasite tolerance and host sex

How infected hosts behave critically affects both their fitness and the transmission, and thus fitness, of their parasites. Understanding host–parasite coevolution therefore requires understanding the factors affecting infected host behaviour. This can usefully be decomposed into the current behavioural expression level and any infection-induced changes in that expression: each of these may have different implications for host and parasite fitness. For example, from the perspective of socially transmitted parasites, the more contacts infected hosts make with susceptible conspecifics, the better, regardless of their pre-infection contact behaviour. For social hosts, however, minimizing infection-induced changes to fitness-enhancing behaviours (‘behavioural tolerance’) may reduce the risk of social exclusion and its associated costs. Here, we tested how the presence of conspecifics (‘social context’) affects the behaviour and behavioural tolerance of guppies, Poecilia reticulata, infected with the socially transmitted ectoparasite Gyrodactylus turnbulli. In the absence of a stimulus shoal of three females, males that lost the most mass over the course of infection (i.e. had lowest tissue-specific tolerance) were significantly less active, whereas in the presence of the shoal, male activity levels were high and not correlated with tissue-specific tolerance. Females were consistently active, regardless of their tissue-specific tolerance or social context. Behavioural tolerance, quantified as the per-parasite change in activity level, also differed between the sexes in the absence of the shoal: among females, behavioural tolerance was negatively correlated with tissue-specific tolerance, whereas in males the correlation was strikingly positive. In the presence of the shoal, however, tolerance components were not correlated in either sex. Overall, these sex differences in behaviour and behavioural tolerance indicate that females are highly competent at transmitting this parasite, and that males can conceal their disease when in the presence of females. Our results contribute to the growing literature on factors affecting variation between infected hosts, which fundamentally affects epidemiological predictions.