The poultry red mite (PRM) is an obligatory haematophagous pest that causes substantial economic losses in poultry worldwide. The PRM does not live on the host but in the bird's environment and must find its host remotely. Hence, manipulating chicken odours is of interest. Several crude plant-originating volatile organic compounds (VOCs) have already been shown as repellent to Dermanyssus gallinae. We aimed to test whether these VOCs can interfere with PRM host-seeking behaviour by their oral administration to the poultry. The objectives were to determine (1) if hen odours are modified by supplemented feed ingestion and (2) if such treatment makes hens less attractive to the PRM. Chemical characterization by gas chromatography–mass spectrometry of the hen odour was conducted before and after the hens ingested the supplemented feed. The chromatograms obtained show that hen odour was substantially modified after the hens consumed it. Among the molecules recurrently detected from the supplemented hens, 26% were nearly absent in the unsupplemented hens. Behavioural choice tests to compare the effect of the modified and unmodified-host odours on the PRM show that some of the plant-originating emitted VOCs and the modified whole-hen odours were repellent to the PRM.

The ecological ubiquity of parasites and their potential impacts on host behaviour have led to the suggestion that parasites can act as ecosystem engineers, structuring their environment and physical habitats. Potential modification of the relationship between parasites and their hosts by climate change has important implications for how hosts interact with both their biotic and abiotic environment. Here, we show that warming and parasitic infection independently increase rates of bioturbation by a key detritivore in aquatic ecosystems (Gammarus). These findings have important implications for ecosystem structure and functioning in a warming world, as alterations to rates of bioturbation could significantly modify oxygenation penetration and nutrient cycling in benthic sediments of rivers and lakes. Our results demonstrate a need for future ecosystem management strategies to account for parasitic infection when predicting the impacts of a warming climate.

Hairy nightshade is a common weed in potato rotations in the western United States. As a close relative of potato, hairy nightshade can host numerous potato nematodes, diseases, and insect pests. Hairy nightshade hosts three common parasitic nematodes of potato, Columbia and northern root-knot nematodes, and stubby root nematode. Tubers of a potato breeding line with roots that are resistant to Columbia root-knot nematode—race 1, were damaged when grown in the presence of hairy nightshade. The weed provided an alternate host for the nematode, which then allowed the nematode to infect susceptible tubers. Stubby root nematodes transmit tobacco rattle virus (TRV), the causal agent for corky ringspot disease (CRS) of potato. CRS disease was maintained in soil when hairy nightshade was present in rotation crops of alfalfa or Scotch spearmint that otherwise eliminated the disease. Hairy nightshade also is a host of potato leaf roll virus (PLRV), which is transmitted by green peach aphids (GPA). GPA preferentially land and readily reproduce on hairy nightshade. Aphid transmission of PLRV from hairy nightshade to potato was four times greater than the virus transmission rate from potato to potato. Integrated management of these potato nematodes, diseases, and insect pests also should include strategies to control hairy nightshade in potato and rotation crops.

The impact of haematozoan infection on host fitness has received substantial attention since Hamilton and Zuk posited that parasites are important drivers of sexual selection. However, short-term studies testing the assumption that these parasites consistently reduce host fitness in the wild have produced contradictory results. To address this complex issue, we conducted a long-term study examining the relationship between naturally occurring infection with Haemoproteus and Plasmodium, and lifetime reproductive success and survival of Mountain White-crowned Sparrows. Specifically, we tested the hypothesis that birds infected with haematozoan parasites have reduced survival (as determined by overwinter return rates) and reproductive success. Contrary to expectation, there was no relationship between Haemoproteus and Plasmodium infection and reproduction or survival in males, nor was there a relationship between Plasmodium infection and reproduction in females. Interestingly, Haemoproteus-infected females had significantly higher overwinter return rates and these females fledged more than twice as many chicks during their lifetimes as did uninfected females. We discuss the impact of parasitic infections on host fitness in light of these findings and suggest that, in the case of less virulent pathogens, investment in excessive immune defence may decrease lifetime reproduction.

Systems biology aims to integrate multiple biological data types such as genomics, transcriptomics and proteomics across different levels of structure and scale; it represents an emerging paradigm in the scientific process which challenges the reductionism that has dominated biomedical research for hundreds of years. Systems biology will nevertheless only be successful if the technologies on which it is based are able to deliver the required type and quality of data. In this review we discuss how well positioned is proteomics to deliver the data necessary to support meaningful systems modelling in parasite biology. We summarise the current state of identification proteomics in parasites, but argue that a new generation of quantitative proteomics data is now needed to underpin effective systems modelling. We discuss the challenges faced to acquire more complete knowledge of protein post-translational modifications, protein turnover and protein-protein interactions in parasites. Finally we highlight the central role of proteome-informatics in ensuring that proteomics data is readily accessible to the user-community and can be translated and integrated with other relevant data types.

The 3 post-marsupial juvenile stages of the gnathiid isopod, Paragnathia formica, are haematophagous ectoparasites of fishes that may, in heavy infestations, cause host mortality. Protein digestion in fed stage 3 juveniles is accomplished by cysteine proteinases, but what bioactive compounds attenuate host haemostatic, inflammatory and immunological responses during feeding is unknown. Trypsin inhibitory activity and anticoagulant activity were detected in crude extracts of unfed P. formica stage 1 juveniles; fractionation of stage 1 crude extracts by ion exchange chromatography resulted in 3 preparations each displaying these bioactivities. Further characterization revealed anti-thrombin activity in 2 of these preparations, whilst the third displayed the strongest anticoagulant activity that targeted a factor of the intrinsic coagulation pathway. Three trypsin inhibitors (18 kDa, 21 kDa, and 22 kDa) were also detected using reverse zymography. In parallel, homogenates of fed stage 2 and 3 juveniles were used to identify their fish hosts by amplifying the 16S mitochondrial rDNA and 18S genomic rDNA vertebrate gene regions. Blood from at least 4 fish families had been ingested by separate individuals during feeding. This study demonstrates that trypsin inhibitors and anticoagulants are present in P. formica juveniles which could suppress host haemostatic, inflammatory and immunological responses during feeding, and that juveniles are not host specific.

The transmission of parasites takes place under exposure to a range of fluctuating environmental factors, one being the changing levels of solar ultraviolet radiation (UVR). Here, we investigated the effects of ecologically relevant levels of UVR on the transmission of the intertidal trematode Maritrema novaezealandensis from its first intermediate snail host (Zeacumantus subcarinatus) to its second intermediate amphipod host (Paracalliope novizealandiae). We assessed the output of parasite transmission stages (cercariae) from infected snail hosts, the survival and infectivity of cercariae, the susceptibility of amphipod hosts to infection (laboratory experiments) and the survival of infected and uninfected amphipod hosts (outdoor experiment) when exposed to photo-synthetically active radiation only (PAR, 400–700 nm; no UV), PAR+UVA (320–700 nm) or PAR+UVA+UVB (280–700 nm). Survival of cercariae and susceptibility of amphipods to infection were the only two steps significantly affected by UVR. Survival of cercariae decreased strongly in a dose-dependent manner, while susceptibility of amphipods increased after exposure to UVR for a prolonged period. Exposure to UVR thus negatively affects both the parasite and its amphipod host, and should therefore be considered an influential component in parasite transmission and host-parasite interactions in intertidal ecosystems.

For Isospora (Protozoa: Eimeriidae) parasites of passerine birds, diurnal periodicity of oocyst output is a well-described phenomenon. From the temporal zone to the tropics, oocyst production is correlated with the light-dark cycle, peaking in the afternoon hours. However, nothing is known about the existence of diurnal periodicity of these parasites in the birds of High Arctic environments, under permanent light during summer. We sampled free-ranging Snow Bunting (Aves: Passeriformes), on Svalbard in summer and tested oocysts output of Isospora plectrophenaxia. Here we show that under the permanent light conditions of Arctic summer in the wild, Isospora plectrophenaxia, a parasite of the Snow Bunting, still keeps the 24-h rhythm of oocyst output with the peak in the post-meridiem hours, despite the absence of diurnal periodicity in host's activity. Our findings prove the ability of avian Isospora to invoke alternative cues for synchronizing the circadian rhythms. Possible cues and adaptive significance of diurnal periodicity of parasite output in High Arctic are discussed. The maintenance of synchronization and timing of the parasite life-cycle stages is under positive selection pressure even in permanent daylight in the Arctic.

The uses of metabolic profiling technologies such as mass spectrometry and nuclear magnetic resonance spectroscopy in parasitology have been multi-faceted. Traditional uses of spectroscopic platforms focused on determining the chemical composition of drugs or natural products used for treatment of parasitic infection. A natural progression of the use of these tools led to the generation of chemical profiles of the parasite in in vitro systems, monitoring the response of the parasite to chemotherapeutics, profiling metabolic consequences in the host organism and to deriving host-parasite interactions. With the dawn of the post-genomic era the paradigm in many research areas shifted towards Systems Biology and the integration of biomolecular interactions at the level of the gene, protein and metabolite. Although these technologies have yet to deliver their full potential, metabolic profiling has a key role to play in defining diagnostic or even prognostic metabolic signatures of parasitic infection and in deciphering the molecular mechanisms underpinning the development of parasite-induced pathologies. The strengths and weaknesses of the various spectroscopic technologies and analytical strategies are summarized here with respect to achieving these goals.

Avian Plasmodium and Haemoproteus parasites are easily detected by DNA analyses of infected samples but only correctly assigned to each genus by sequencing and use of a phylogenetic approach. Here, we present a restriction site to differentiate between both parasite genera avoiding the use of those analyses. Alignments of 820 sequences currently listed in GenBank encoding a particular cytochrome B region of avian Plasmodium and Haemoproteus show a shared restriction site for both genera using the endonuclease Hpy CH4III. An additional restriction site is present in Plasmodium sequences that would initially allow differentiation of both genera by differential migration of digested products on gels. Overall 9 out of 326 sequences containing both potential restriction sites do not fit to the general rule. We used this differentiation of parasite genera based on Hpy CH4III restriction sites to evaluate the efficacy of 2 sets of general primers in detecting mixed infections. To do so, we used samples from hosts infected by parasites of both genera. The use of general primers was only able to detect 25% or less of the mixed infections. Therefore, parasite DNA amplification using general primers to determine the species composition of haemosporidian infections in individual hosts is not recommended. Specific primers for each species and study area should be designed until a new method can efficiently discriminate both parasites.

Parasites are generally found aggregated among hosts. In this paper we propose a method for measuring aggregation at different scales in the host population. We use the method to characterize the pattern of aggregation of the tick Ixodes uriae on chicks of its seabird host, the Kittiwake Rissa tridactyla. We found evidence of aggregation at the among-nest scale, but not among chicks within nests. This shows that the processes leading to aggregation occur at a higher scale than the nest. The methods we develop provide a way to compare parasite aggregation at different scales in a quantitative fashion and can be applied in a large number of epidemiological studies.

The paper examines non-linear dynamical phenomena in host—parasite interactions by reference to a series of different problems ranging from the impact on transmission of control measures based on vaccination and chemotherapy, to the effects of immunological responses targeted at different stages in a parasite's life-cycle. Throughout, simple mathematical models are employed to aid in interpretation. Analyses reveal that the influence of a defined control measure on the prevalence or intensity of infection, whether vaccination or drug treatment, is non-linearly related to the magnitude of control effort (as defined by the proportion of individuals vaccinated or treated with a drug). Consideration of the relative merits of gametocyte and sporozoite vaccines against malarial parasites suggests that very high levels of cohort immunization will be required to block transmission in endemic areas, with the former type of vaccine being more effective in reducing transmission for a defined level of coverage and the latter being better with respect to a reduction in morbidity. The inclusion of genetic elements in analyses of the transmission of helminth parasites reveals complex non-linear patterns of change in the abundance of different parasite genotypes under selection pressures imposed by either the host immunological defences or the application of chemotherapeutic agents. When resistance genes are present in parasite populations, the degree to which abundance can be suppressed by chemotherapy depends critically on the frequency and intensity of application, with intermediate values of the former being optimal. A more detailed consideration of the impact of immunological defences on parasite population growth within an individual host, by reference to the erythrocytic cycle of malaria, suggests that the effectiveness of a given immunological response is inversely related to the life-expectancy of the target stage in the parasite's developmental cycle.

The study of regulatory peptides has its origins in the classical work of Bayliss & Starling (1902). Their pioneering work on the presence of a factor in intestinal extracts which, when injected into the bloodstream of experimental animals, elicited pancreatic secretion, led to the genesis of the concept of the hormone, i.e. a chemical messenger which is released from one part of the body in response to a stimulus to travel in the bloodstream to a distant target tissue where it would elicit a physiological response appropriate to the original stimulus. In keeping with accepted scientific tradition, this concept had its critics. Pavlov, who had been studying secretory stimulation from a different perspective, concluded from his work on salivation in dogs, that this was mediated via neural pathways. With hindsight, and the benefits of knowledge obtained from nearly a century of scientific research, we now know that these pioneers were in actual fact studying different aspects of the same process and that both theories were complementary. In fact, it is becoming increasingly difficult to ascribe secretory control to either circulating or neuronal factors as both appear to be intimately involved in regulation.

Successful host invasion by parasitic helminths involves detection and appropriate response to a range of host-derived signals. Insulin signal response pathways are ancient and highly-conserved throughout the metazoans. However, very little is known about helminth insulin signalling and the potential role it may play in host-parasite interactions. The response of Mesocestoides vogae (Cestoda: Cyclophyllidea) larvae to human insulin was investigated, focusing on tyrosine-phosphorylation status, glucose content, survival and asexual reproduction rate. Parasite larvae were challenged with different levels of insulin for variable periods. The parameters tested were influenced by human insulin, and suggested a host-parasite molecular dialogue.†

The adenophorean nematodes are evolutionarily distant from other species in the phylum Nematoda. Interspecific comparisons of predicted proteins have supported such an ancient divergence. Accordingly, Trichinella spiralis represents a basal nematode representative for genome sequencing focused on gaining a deeper insight into the evolutionary biology of nematodes. In addition, molecular characteristics that are conserved across the phylum could be of great value for control strategies with broad application. In this review, we describe and summarize progress that has been made on the sequencing and analysis of the T. spiralis genome. The genome sequence was used in preliminary analyses for the investigation of specific questions relating to the biology of T. spiralis and, more generally, to parasitic nematodes. For instance, we evaluated an unusually large DNase II-like protein family, predicted proteins of prospective interest in the parasite-host muscle cell interaction, anthelmintic targets and prospective intestinal genes, the encoded proteins (potentially) linked to immunological control against other nematodes. The results are discussed in relation to characteristics that are broadly conserved among evolutionary distant nematodes. The results lead to expectations that this genome sequence will contribute to advances in research on T. spiralis and other parasitic nematodes.

Molecular interplay during snail-schistosome interactions is poorly understood and there is much to discover concerning the effect of snail host molecules on molecular processes in schistosomes. Using the Biomphalaria glabrata – Schistosoma mansoni host-parasite system, the effects of exposure to haemolymph, derived from schistosome-resistant and susceptible snail strains, on protein tyrosine phosphorylation in miracidia have been investigated. Western blotting revealed several tyrosine phosphorylated proteins in this larval stage. Exposure of miracidia to haemolymph from susceptible snails for 60 min resulted in a striking, 5-fold, increase in the tyrosine phosphorylation of a 56 kDa (p56) S. mansoni protein. In contrast, haemolymph from resistant snails had little effect on protein tyrosine phosphorylation levels in miracidia. Confocal microscopy revealed that tyrosine phosphorylation was predominantly associated with proteins present in the tegument. Finally, treatment of miracidia with the tyrosine kinase inhibitor genistein significantly impaired their development into primary sporocysts. The results open avenues for research that focus on the potential importance of phospho-p56 to the outcome of schistosome infection in snails, and the significance of protein tyrosine kinase-mediated signalling events to the transformation of S. mansoni larvae.

Echinococcus granulosus and Echinococcus multilocularis are cestode parasites, of which the metacestode (larval) stages cause the diseases cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. Albendazole and mebendazole are presently used for chemotherapeutical treatment. However, these benzimidazoles do not appear to be parasiticidal in vivo against AE. In addition, failures in drug treatments as well as the occurrence of side-effects have been reported. New drugs are needed to cure AE and CE, which are considered to be neglected diseases. Strategies currently being implemented to identify novel chemotherapeutical treatment options include (i) conventional primary in vitro testing of broad-spectrum anti-infective drugs, either in parallel with, or followed by, animal experimentation; (ii) studies of drugs which interfere with the proliferation of cancer cells and of Echinococcus metacestodes; (iii) exploitation of the similarities between the parasite and mammalian signalling machineries, with a special focus on targeting specific signalling receptors; (iv) in silico approaches, employing the current Echinococcus genomic database information to search for suitable targets for compounds with known modes of action. In the present article, we review the efforts toward obtaining better anti-parasitic compounds which have been undertaken to improve chemotherapeutical treatment of echinococcosis, and summarize the achievements in the field of host-parasite interactions which may also lead to new immuno-therapeutical options.

Terminal sialic acid residues on surface-associated glycoconjugates mediate host cell interactions of many pathogens. Addition of sialic acid-rich fetuin enhanced, and the presence of the sialidiase inhibitor 2-deoxy-2,3-dehydro-N-acetylneuraminic acid reduced, the physical interaction of Neospora caninum tachyzoites and bradyzoites with Vero cell monolayers. Thus, Neospora extracts were subjected to fetuin-agarose affinity chromatography in order to isolate components potentially interacting with sialic acid residues. SDS-PAGE and silver staining of the fetuin binding fraction revealed the presence of a single protein band of ∼65 kDa, subsequently named NcFBP (Neospora caninum fetuin-binding protein), which was localized at the apical tip of the tachyzoites and was continuously released into the surrounding medium in a temperature-independent manner. NcFBP readily interacted with Vero cells and bound to chondroitin sulfate A and C, and anti-NcFBP antibodies interfered in tachyzoite adhesion to host cell monolayers. In additon, analysis of the fetuin binding fraction by gelatin substrate zymography was performed, and demonstrated the presence of two bands of 96 and 140 kDa exhibiting metalloprotease-activity. The metalloprotease activity readily degraded glycosylated proteins such as fetuin and bovine immunoglobulin G heavy chain, whereas non-glycosylated proteins such as bovine serum albumin and immunoglobulin G light chain were not affected. These findings suggest that the fetuin-binding fraction of Neospora caninum tachyzoites contains components that could be potentially involved in host-parasite interactions.

Parasites are ubiquitous in wild animals, with host-specific life histories considered as major determinants of prevalence and parasite assemblage patterns. It is predicted that habitat differences in logged rain forests influence population performances of small mammals and consequently may change the infection patterns of local animal populations with regard to endo- and ectoparasites. We investigated patterns of helminth species assemblages (Nematoda, Platyhelminthes) in two rat species (Leopoldamys sabanus, Niviventer cremoriventer) and two tree shrew species (Tupaia tana, T. longipes) in three logged and three unlogged rain forests in Borneo by examining 337 faecal samples with non-invasive faecal egg count (FEC). Nematode eggs prevailed in 95% of all samples with up to five (mean 1.9 ± 1.1) morphotypes. Whereas members of Strongylida were most prevalent in L. sabanus, T. tana and T. longipes, Spirurida dominated in N. cremoriventer that revealed at the same time the lowest average nematode prevalence and FEC. Cestode eggs were only found in L. sabanus and T. tana. Composition and abundance patterns of the parasitic helminth assemblages were influenced by logging. As hypothesized, species richness of nematode morphotypes and mean number of infections per host of T. longipes were larger in logged than in unlogged forest. In contrast, L. sabanus was more heavily infected with cestodes in unlogged than in logged forest and also revealed larger egg counts for strongylids and spirurids in unlogged forest. Our results suggest that forest degradation and altered environmental conditions influence helminth diversity and infection patterns of small mammals with contrasting trends among host species. The inconsistent logging-induced changes in helminth assemblages from different hosts indicate that specific sets of habitat-host-parasite interactions are uniquely influenced by the effects of logging. Consequently, predictions on changes of parasite diversity and prevalence with regard to habitat disturbance need to be based on the individual life histories of the hosts (and the parasites).

Multiple invasions (MIs) or infections, i.e. those by more than 1 parasite in the same erythrocyte, could be the result of parasite density or, alternatively, to parasite-related factors or host-related factors. According to the last possibility, to our knowledge, only 3 laboratory studies of malaria have found an increase in the occurrence of MIs when antibodies to parasite antigens were present. Therefore, we tested the possibility that MIs were influenced by the host immune status, using as model the malaria-like parasite Haemoproteus infecting blue tits (Cyanistes caeruleus). Avian hosts infected with Haemoproteus were medicated with primaquine or injected with saline solution and the density of infection and the presence of MIs counted. Medication treatment reduced significantly the density of infection by Haemoproteus in females but not in males. For females, the presence of MIs was positively associated with both the density of infection and the immunoglobulin levels on each capture, but no association was found between the treatment and the presence of MIs. For males, the density of infection but not the immunoglobulin levels was positively associated with the presence of MIs. In addition, medicated males supported more MIs than controls. Our results represent the first line of evidence in the wild for a possible role of the host immune system promoting MIs.