Does avian malaria infection affect feather stable isotope signatures?

It is widely accepted that stable isotope ratios in inert tissues such as feather keratin reflect the dietary isotopic signature at the time of the tissue synthesis. However, some elements such as stable nitrogen isotopes can be affected by individual physiological state and nutritional stress. Using malaria infection experiment protocols, we estimated the possible effect of malaria parasite infections on feather carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope signatures in juvenile common crossbills Loxia curvirostra. The birds were experimentally infected with Plasmodium relictum (lineage SGS1) and P. ashfordi (GRW2), two widespread parasites of passerines. Experimental birds developed heavy parasitemia of both parasites and maintained high levels throughout the experiment (33 days). We found no significant difference between experimental and control birds in both δ¹³C and δ¹⁵N values of feathers re-grown. The study shows that even heavy primary infections of malaria parasites do not affect feather δ¹³C and δ¹⁵N isotopic signatures. The results of this experiment demonstrate that feather isotope values of wild-caught birds accurately reflect the dietary isotopic sources at the time of tissue synthesis even when the animal’s immune system might be challenged due to parasitic infection.     

Pathways activated during human asthma exacerbation as revealed by gene expression patterns in blood

Background

Asthma exacerbations remain a major unmet clinical need. The difficulty in obtaining airway tissue and bronchoalveolar lavage samples during exacerbations has greatly hampered study of naturally occurring exacerbations. This study was conducted to determine if mRNA profiling of peripheral blood mononuclear cells (PBMCs) could provide information on the systemic molecular pathways involved during asthma exacerbations.

Methodology/Principal Findings

Over the course of one year, gene expression levels during stable asthma, exacerbation, and two weeks after an exacerbation were compared using oligonucleotide arrays. For each of 118 subjects who experienced at least one asthma exacerbation, the gene expression patterns in a sample of peripheral blood mononuclear cells collected during an exacerbation episode were compared to patterns observed in multiple samples from the same subject collected during quiescent asthma. Analysis of covariance identified genes whose levels of expression changed during exacerbations and returned to quiescent levels by two weeks. Heterogeneity among visits in expression profiles was examined using K-means clustering. Three distinct exacerbation-associated gene expression signatures were identified. One signature indicated that, even among patients without symptoms of respiratory infection, genes of innate immunity were activated. Antigen-independent T cell activation mediated by IL15 was also indicated by this signature. A second signature revealed strong evidence of lymphocyte activation through antigen receptors and subsequent downstream events of adaptive immunity. The number of genes identified in the third signature was too few to draw conclusions on the mechanisms driving those exacerbations.

Conclusions/Significance

This study has shown that analysis of PBMCs reveals systemic changes accompanying asthma exacerbation and has laid the foundation for future comparative studies using PBMCs.     

Two new species of Haemoproteus Kruse, 1890 (Haemosporida,Haemoproteidae) from European birds,with emphasis on DNA barcoding for detection of haemosporidians in wildlife

Two new species of Haemoproteus Kruse, 1890 (Haemosporida, Haemoproteidae) are described: Haemoproteus (Parahaemoproteus) homovelans n. sp. from Grey-faced Woodpecker, Picus canus Gmelin, and Haemoproteus (Parahaemoproteus) concavocentralis n. sp. recorded in Hawfinch, Coccothraustes coccothraustes (Linnaeus), both sampled in Bulgaria. The morphology of the gametocytes and their host-cells are described and mitochondrial cytochrome b (cyt b) gene sequences are generated. Haemoproteus homovelans possesses circumnuclear gametocytes lacking volutin granules. This parasite is particularly similar to Haemoproteus velans Coatney & Roudabush, 1937 also possessing circumnuclear gametocytes that are, however, overfilled with volutin. Haemoproteus concavocentralis can be readily distinguished from all described avian haemoproteids due to the presence of an unfilled concave space between the central part of advanced gametocytes and erythrocyte nucleus. Bayesian phylogenetic analyses of 40 haemosporidian cyt b lineages showed close relationships of H. concavocentralis (hHAWF2) with a group of Haemoproteus spp. possessing gametocytes that are pale-stained with Giemsa. The lineage hPICAN02 of H. homovelans clustered with parasites infecting non-passerine birds. Phylogenetic analyses support the current subgeneric classification of the avian haemoproteids and suggest that cyt b lineage hPIPUB01 (GenBank EU254552) has been incorrectly assigned to Haemoproteus picae Coatney & Roudabush, 1937, a common parasite of corvid birds (Passeriformes). This study emphasises the importance of combining molecular techniques and light microscopy in the identification and field studies of avian haemosporidian parasites. Future development of barcodes for molecular identification of haemoproteids will allow better diagnostics of these infections, particularly in veterinary studies addressing insufficiently investigated tissue pathology caused by these parasites.     

Spontaneous and electric field–controlled front–rear polarization of human keratinocytes

It has long been known that electrical fields (EFs) are able to influence the direction of migrating cells, a process commonly referred to as electrotaxis or galvanotaxis. Most studies have focused on migrating cells equipped with an existing polarity before EF application, making it difficult to delineate EF-specific pathways. Here we study the initial events in front–rear organization of spreading keratinocytes to dissect the molecular requirements for random and EF-controlled polarization. We find that Arp2/3-dependent protrusive forces and Rac1/Cdc42 activity were generally required for both forms of polarization but were dispensable for controlling the direction of EF-controlled polarization. By contrast, we found a crucial role for extracellular pH as well as G protein coupled–receptor (GPCR) or purinergic signaling in the control of directionality. The normal direction of polarization toward the cathode was reverted by lowering extracellular pH. Polarization toward the anode was also seen at neutral pH when GPCR or purinergic signaling was inhibited. However, the stepwise increase of extracellular pH in this scenario led to restoration of cathodal polarization. Overall our work puts forward a model in which the EF uses distinct polarization pathways. The cathodal pathway involves GPCR/purinergic signaling and is dominant over the anodal pathway at neutral pH.     

Co‐infections by malaria parasites decrease feather growth but not feather quality in house martin

During moult, stressors such as malaria and related haemosporidian parasites (e.g. Plasmodium and Haemoproteus) could affect the growth rate and quality of feathers, which in turn may compromise future reproduction and survival. Recent advances in molecular methods to study parasites have revealed that co‐infections with multiple parasites are frequent in bird–malaria parasite systems. However, there is no study of the consequences of co‐infections on the moult of birds. In house martins Delichon urbica captured and studied at a breeding site in Europe during 11 yr, we measured the quality and the growth rate of tail feathers moulted in the African winter quarters in parallel with the infection status of blood parasites that are also transmitted on the wintering ground. Here we tested if the infection with two haemosporidian parasite lineages has more negative effects than a single lineage infection. We found that birds with haemosporidian infection had lower body condition. We also found that birds co‐infected with two haemosporidian lineages had the lowest inferred growth rate of their tail feathers as compared with uninfected and single infected individuals, but co‐infections had no effect on feather quality. In addition, feather quality was negatively correlated with feather growth rate, suggesting that these two traits are traded‐off against each other. We encourage the study of haemosporidian parasite infection as potential mechanism driving this trade‐off in wild populations of birds.     

Malaria infection and feather growth rate predict reproductive success in house martins

Carry-over effects take place when events occurring in one season influence individual performance in a subsequent season. Blood parasites (e.g. Plasmodium and Haemoproteus) have strong negative effects on the body condition of their hosts and could slow the rate of feather growth on the wintering grounds. In turn, these winter moult costs could reduce reproductive success in the following breeding season. In house martins Delichon urbica captured and studied at a breeding site in Europe, we used ptilochronology to measure growth rate of tail feathers moulted on the winter range in Africa, and assessed infection status of blood parasites transmitted on the wintering grounds. We found a negative association between haemosporidian parasite infection status and inferred growth rate of tail feathers. A low feather growth rate and blood parasite infections were related to a delay in laying date in their European breeding quarters. In addition, clutch size and the number of fledglings were negatively related to a delayed laying date and blood parasite infection. These results stress the importance of blood parasites and feather growth rate as potentially mechanisms driving carry-over effects to explain fitness differences in wild populations of migratory birds.     

Conflicting patterns of mitochondrial and nuclear DNA diversity in Phylloscopus warblers

Molecular variation is often used to infer the demographic history of species, but sometimes the complexity of species history can make such inference difficult. The willow warbler, Phylloscopus trochilus, shows substantially less geographical variation than the chiffchaff, Phylloscopus collybita, both in morphology and in mitochondrial DNA (mtDNA) divergence. We therefore predicted that the willow warbler should harbour less nuclear DNA diversity than the chiffchaff. We analysed sequence data obtained from multiple samples of willow warblers and chiffchaffs for the mtDNA cytochrome b gene and four nuclear genes. We confirmed that the mtDNA diversity among willow warblers is low (pi = 0.0021). Sequence data from three nuclear genes (CHD-Z, AFLP-WW1 and MC1R) not linked to the mitochondria demonstrated unexpectedly high nucleotide diversity (pi values of 0.0172, 0.0141 and 0.0038) in the willow warbler, on average higher than the nucleotide diversity for the chiffchaff (pi values of 0.0025, 0.0017 and 0.0139). In willow warblers, Tajima's D analyses showed that the mtDNA diversity, but not the nuclear DNA diversity, has been reduced relative to the neutral expectation of molecular evolution, suggesting the action of a selective sweep affecting the maternally inherited genes. The large nuclear diversity seen within willow warblers is not compatible with processes of neutral evolution occurring in a population with a constant population size, unless the long-term effective population size has been very large (N(e) > 10(6)). We suggest that the contrasting patterns of genetic diversity in the willow warbler may reflect a more complex evolutionary history, possibly including historical demographic fluctuations or historical male-biased introgression of nuclear genes from a differentiated population of Phylloscopus warblers.     

The ecology of emerging infectious diseases in migratory birds: an assessment of the role of climate change and priorities for future research

Pathogens that are maintained by wild birds occasionally jump to human hosts, causing considerable loss of life and disruption to global commerce. Preliminary evidence suggests that climate change and human movements and commerce may have played a role in recent range expansions of avian pathogens. Since the magnitude of climate change in the coming decades is predicted to exceed climatic changes in the recent past, there is an urgent need to determine the extent to which climate change may drive the spread of disease by avian migrants. In this review, we recommend actions intended to mitigate the impact of emergent pathogens of migratory birds on biodiversity and public health. Increased surveillance that builds upon existing bird banding networks is required to conclusively establish a link between climate and avian pathogens and to prevent pathogens with migratory bird reservoirs from spilling over to humans.     

MalAvi: a public database of malaria parasites and related haemosporidians in avian hosts based on mitochondrial cytochrome b lineages

Research in avian blood parasites has seen a remarkable increase since the introduction of polymerase chain reaction-based methods for parasite identification. New data are revealing complex multihost-multiparasite systems which are difficult to understand without good knowledge of the host range and geographical distribution of the parasite lineages. However, such information is currently difficult to obtain from the literature, or from general repositories such as GenBank, mainly because (i) different research groups use different parasite lineage names, (ii) GenBank entries frequently refer only to the first host and locality at which each parasite was sampled, and (iii) different researchers use different gene fragments to identify parasite lineages. We propose a unified database of avian blood parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon identified by a partial region of their cytochrome b sequences. The database uses a standardized nomenclature to remove synonymy, and concentrates all available information about each parasite in a public reference site, thereby facilitating access to all researchers. Initial data include a list of host species and localities, as well as genetic markers that can be used for phylogenetical analyses. The database is free to download and will be regularly updated by the authors. Prior to publication of new lineages, we encourage researchers to assign names to match the existing database. We anticipate that the value of the database as a source for determining host range and geographical distribution of the parasites will grow with its size and substantially enhance the understanding of this remarkably diverse group of parasites.