Search

Coccidia infections in wild birds rarely cause clinical signs; however, disease and mortality can occur with predisposing environmental and host conditions. The Yellow-eyed Penguin (Megadyptes antipodes) is an endangered species endemic to New Zealand that has seen significant ongoing population decline. The aim of this study was to examine the host–pathogen dynamics of coccidian parasites in two wild populations of Yellow-eyed Penguin: the mainland (South Island) population and the sub-Antarctic (Enderby Island) population. There was weak evidence for a difference in the prevalence of the Eimeria sp. in birds from Enderby Island (76.6%; 36/47; 95% confidence interval [CI] 62.78–86.4%) and the South Island of New Zealand (58.54%; 24/41; 95% CI 43.37–72.24%). The mean pathogen load in penguins on Enderby Island was 9,723 oocysts/g of feces (SE=5831 oocysts/g) and from the South Island of New Zealand was 1,050 oocysts/g (SE=398 oocysts/g). No evidence of an association was found between pathogen load and body weight in either study population. The morphology of the sporulated coccidial oocysts was consistent with a novel species of Eimeria. There was statistically significant variation between the oocysts collected from the two sites in all measurements apart from the oocyst wall thickness. However, the standard technique of assessing linear regressions of the length and width of oocysts from both sampling sites was 0.80, and therefore above the standard R2>0.5 used to indicate variation within a single population of oocysts, suggesting that only a single species of Eimeria was present at both sampling locations. The prevalence and pathogen load of Eimeria sp. was substantially higher than previous reports of coccidial oocysts in Yellow-eyed Penguins and free-living Sphenisciformes globally. This host–parasite relationship deserves further investigation, as the impact of this novel organism on the population remains unclear. [ABSTRACT FROM AUTHOR]

Influenza virus has a high mutation rate, such that within one host different viral variants can emerge. Evidence suggests that influenza virus variants are more prevalent in pregnant and/or obese individuals due to their impaired interferon response. We have recently shown that the non-allergic, paucigranulocytic subtype of asthma is associated with impaired type I interferon production. Here, we seek to address if this is associated with an increased emergence of influenza virus variants. Compared to controls, mice with paucigranulocytic asthma had increased disease severity and an increased emergence of influenza virus variants. Specifically, PB1 mutations exclusively detected in asthmatic mice were associated with increased polymerase activity. Furthermore, asthmatic host-derived virus led to increased disease severity in wild-type mice. Taken together, these data suggest that at least a subset of patients with asthma may be more susceptible to severe influenza and may be a possible source of new influenza virus variants.

Anthropogenic changes create evolutionarily novel environments that present opportunities for emerging diseases, potentially changing the balance between host and pathogen. Honey bees provide essential pollination services, but intensification and globalization of honey bee management has coincided with increased pathogen pressure, primarily due to a parasitic mite/virus complex. Here, we investigated how honey bee individual and group phenotypes are altered by a virus of concern, Israeli acute paralysis virus (IAPV). Using automated and manual behavioral monitoring of IAPV-inoculated individuals, we find evidence for pathogen manipulation of worker behavior by IAPV, and reveal that this effect depends on social context; that is, within versus between colony interactions. Experimental inoculation reduced social contacts between honey bee colony members, suggesting an adaptive host social immune response to diminish transmission. Parallel analyses with double-stranded RNA (dsRNA)- immunostimulated bees revealed these behaviors are part of a generalized social immune defensive response. Conversely, inoculated bees presented to groups of bees from other colonies experienced reduced aggression compared with dsRNA-immunostimulated bees, facilitating entry into susceptible colonies. This reduction was associated with a shift in cuticular hydrocarbons, the chemical signatures used by bees to discriminate colony members from intruders. These responses were specific to IAPV infection, suggestive of pathogen manipulation of the host. Emerging bee pathogens may thus shape host phenotypes to increase transmission, a strategy especiallywellsuited to the unnaturally high colony densities of modern apiculture. These findings demonstrate how anthropogenic changes could affect arms races between human-managed hosts and their pathogens to potentially affect global food security. [ABSTRACT FROM AUTHOR]

• Target enrichment can directly sequence host-associated fungal pathogens. • Fungal pathogen load is positively associated with enrichment success. • Resulting genetic data can identify phylogenetic placements of fastidious strains. • Salamander at US zoo was infected with Asian-origin Batrachochytrium strain. • Method can be applied to other unculturable fungal samples to identify cryptic strains. The chytrid fungus Batrachochytrium dendrobatidis (Bd) was discovered in 1998 as the cause of chytridiomycosis, an emerging infectious disease causing mass declines in amphibian populations worldwide. The rapid population declines of the 1970s-1990s were likely caused by the spread of a highly virulent lineage belonging to the Bd-GPL clade that was introduced to naïve susceptible populations. Multiple genetically distinct and regional lineages of Bd have since been isolated and sequenced, greatly expanding the known biological diversity within this fungal pathogen. To date, most Bd research has been restricted to the limited number of samples that could be isolated using culturing techniques, potentially causing a selection bias for strains that can grow on media and missing other unculturable or fastidious strains that are also present on amphibians. We thus attempted to characterize potentially non-culturable genetic lineages of Bd from distinct amphibian taxa using sequence capture technology on DNA extracted from host tissue and swabs. We focused our efforts on host taxa from two different regions that likely harbored distinct Bd clades: (1) wild-caught leopard frogs (Rana) from North America, and (2) a Japanese Giant Salamander (Andrias japonicus) at the Smithsonian Institution's National Zoological Park that exhibited signs of disease and tested positive for Bd using qPCR, but multiple attempts failed to isolate and culture the strain for physiological and genetic characterization. We successfully enriched for and sequenced thousands of fungal genes from both host clades, and Bd load was positively associated with number of recovered Bd sequences. Phylogenetic reconstruction placed all the Rana -derived strains in the Bd-GPL clade. In contrast, the A. japonicus strain fell within the Bd-Asia3 clade, expanding the range of this clade and generating additional genomic data to confirm its placement. The retrieved ITS locus matched public barcoding data from wild A. japonicus and Bd infections found on other amphibians in India and China, suggesting that this uncultured clade is widespread across Asia. Our study underscores the importance of recognizing and characterizing the hidden diversity of fastidious strains in order to reconstruct the spatiotemporal and evolutionary history of Bd. The success of the sequence capture approach highlights the utility of directly sequencing pathogen DNA from host tissue to characterize cryptic diversity that is missed by culture-reliant approaches. [ABSTRACT FROM AUTHOR]

Host-parasitoid systems are characterized by a continuous development of new defence strategies in hosts and counter-defence mechanisms in parasitoids. This co-evolutionary arms race makes host-parasitoid systems excellent for understanding trade-offs in host use caused by evolutionary changes in host immune responses and parasitoid virulence. However, knowledge obtained from natural host-parasitoid systems on such trade-offs is still limited. In this study, the aim was to examine trade-offs in parasitoid virulence in Asecodes parviclava (Hymenoptera: Eulophidae) when attacking three closely related beetles: Galerucella pusilla, Galerucella calmariensis and Galerucella tenella (Coleoptera: Chrysomelidae). A second aim was to examine whether geographic variation in parasitoid infectivity or host immune response could explain differences in parasitism rate between northern and southern sites. More specifically, we wanted to examine whether the capacity to infect host larvae differed depending on the previous host species of the parasitoids and if such differences were connected to differences in the induction of host immune systems. This was achieved by combining controlled parasitism experiments with cytological studies of infected larvae. Our results reveal that parasitism success in A. parviclava differs both depending on previous and current host species, with a higher virulence when attacking larvae of the same species as the previous host. Virulence was in general high for parasitoids from G. pusilla and low for parasitoids from G. calmariensis. At the same time, G. pusilla larvae had the strongest immune response and G. calmariensis the weakest. These observations were linked to changes in the larval hemocyte composition, showing changes in cell types important for the encapsulation process in individuals infected by more or less virulent parasitoids. These findings suggest ongoing evolution in parasitoid virulence and host immune response, making the system a strong candidate for further studies on host race formation and speciation. [ABSTRACT FROM AUTHOR]

The increasing availability of novel molecular techniques has transformed the study of human health and disease epidemiology. However, uptake of such approaches has been more conservative in the field of wildlife disease epidemiology. We consider the reasons for this and discuss current and potential applications of molecular techniques in a variety of relevant areas within the field of wildlife disease research. These include conducting wildlife disease surveillance, identifying sources of pathogen emergence, uncovering host-pathogen dynamics and managing current outbreaks, including the development and monitoring of wildlife vaccines. We highlight key examples of applications of molecular epidemiological approaches to wildlife disease scenarios and draw parallels from human disease research to suggest potential future directions. The potential value of next generation sequencing technologies to the field of wildlife disease research is discussed, and initial applications are highlighted, balanced against consideration of the challenges involved. Using a wide range of examples drawn from research into human, livestock and wildlife diseases, we demonstrate the value of using molecular epidemiological approaches at all scales of wildlife disease research, from pathogen strains circulating at a global scale to intra-individual host-pathogen dynamics. The potential future contribution of these technologies to the field of wildlife disease epidemiology is substantial. In particular, they are likely to play an increasingly important role in helping us to address a principal challenge in the management of wildlife diseases which is how to tease apart the transmission dynamics of complex multi-host systems in order to develop effective and sustainable interventions. [ABSTRACT FROM AUTHOR]

Biological diversity has long been used to measure ecological health. While evidence exists from many ecosystems that declines in host biodiversity may lead to greater risk of disease emergence, the role of pathogen diversity in the emergence process remains poorly understood. Particularly, because a more diverse pool of pathogen types provides more ways in which evolutionary innovations may arise, we suggest that host-pathogen systems with high pathogen diversity are more prone to disease emergence than systems with relatively homogeneous pathogen communities. We call this prediction the diversity-emergence hypothesis., To show how this hypothesis could be tested, we studied a system comprised of North American shorebirds and their associated low-pathogenicity avian influenza ( LPAI) viruses. These viruses are important as a potential source of genetic innovations in influenza. A theoretical contribution of this study is an expression predicting the rate of viral subtype reassortment to be proportional to both prevalence and Simpson's Index, a formula that has been used traditionally to quantify biodiversity. We then estimated prevalence and subtype diversity in host species at Delaware Bay, a North American AIV hotspot, and used our model to extrapolate from these data., We estimated that 4 to 39 virus subtypes circulated at Delaware Bay each year between 2000 and 2008, and that surveillance coverage (percentage of co-circulating subtypes collected) at Delaware Bay is only about 63·0%. Simpson's Index in the same period varied more than fourfold from 0·22 to 0·93. These measurements together with the model provide an indirect, model-based estimate of the reassortment rate. A proper test of the diversity-emergence hypothesis would require these results to be joined to independent and reliable estimates of reassortment, perhaps obtained through molecular surveillance., These results suggest both that subtype diversity (and therefore reassortment) varies from year to year and that several subtypes contributing to reassortment are going undetected. The similarity between these results and more detailed studies of one host, ruddy turnstone ( Arenaria interpres), further suggests that this species may be the primary host for influenza reassortment at Delaware Bay., Biological diversity has long been quantified using Simpson's Index. Our model links this formula to a mechanistic account of reassortment in multipathogen systems in the form of subtype diversity at Delaware Bay, USA. As a theory of how pathogen diversity may influence the evolution of novel pathogens, this work is a contribution to the larger project of understanding the connections between biodiversity and disease. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to test the hypothesis that exposure to a directly transmitted human pathogen—flu virus—increases human social behavior presymptomatically. This hypothesis is grounded in empirical evidence that animals infected with pathogens rarely behave like uninfected animals, and in evolutionary theory as applied to infectious disease. Such behavioral changes have the potential to increase parasite transmission and/or host solicitation of care. Methods: We carried out a prospective, longitudinal study that followed participants across a known point-source exposure to a form of influenza virus (immunizations), and compared social behavior before and after exposure using each participant as his/her own control. Results: Human social behavior does, indeed, change with exposure. Compared to the 48 hours pre-exposure, participants interacted with significantly more people, and in significantly larger groups, during the 48 hours immediately post-exposure. Conclusions: These results show that there is an immediate active behavioral response to infection before the expected onset of symptoms or sickness behavior. Although the adaptive significance of this finding awaits further investigation, we anticipate it will advance ecological and evolutionary understanding of human-pathogen interactions, and will have implications for infectious disease epidemiology and prevention. [ABSTRACT FROM AUTHOR]

Pathogens cause damage, and their elimination requires activation of the costly immune response. A highly economic defense strategy should thus be the behavioral avoidance of pathogens, as manifested in humans by all aspects of hygiene or revulsion at pathogen-rich material. Despite its potential importance, behavioral defenses have as yet received only little attention in biomedical research in stark contrast to the physiological immune system. In the present study, the genetics of such behavioral defenses are elucidated in a simple model organism, the nematode Caenorhabditis elegans. We show for the first time that mutations in the insulin like receptor (ILR) pathway lead to two distinct behavioral responses against pathogenic swains of the Gram-positive bacterium Bacillus thuringiensis (BT), including the physical evasion of pathogens and their reduced oral uptake. Since this pathway also contributes to nematode stress resistance, the results surprisingly reveal a genetic link between physiological and behavioral defenses. Considering that many signaling pathways have conserved their functions across evolution, including the ILR pathway, this signaling cascade may represent an interesting candidate regulator for behavioral defenses in more complex organisms, including humans. [ABSTRACT FROM AUTHOR]