By interactions with other microbes, free-living amoebae play a significant role in microbiology, environmental biology, physiology, cellular interactions, ecology and evolution. Here, we discuss astonishing interactions of bacteria and amoebae, in the light of evolution and functional aspects impacting human health. In favourable environmental conditions, the interaction of Acanthamoeba with non-virulent bacteria results in lysis of the bacteria. However, the interaction with weak-virulent bacteria results in a symbiotic relationship or amoebal lysis may occur. The microbial survival of amoebae in harsh environments, ability to interact with bacteria, and their ability to aid transmission to susceptible hosts is of great concern to human, animal and ecosystem health.

Toxoplasma gondii and Sarcocystis neurona are protozoan parasites with terrestrial definitive hosts, and both pathogens can cause fatal disease in a wide range of marine animals. Close monitoring of threatened southern sea otters (Enhydra lutris nereis) in California allowed for the diagnosis of dual transplacental transmission of T. gondii and S. neurona in a wild female otter that was chronically infected with both parasites. Congenital infection resulted in late-term abortion due to disseminated toxoplasmosis. Toxoplasma gondii and S. neurona DNA was amplified from placental tissue culture, as well as from fetal lung tissue. Molecular characterization of T. gondii revealed a Type X genotype in isolates derived from placenta and fetal brain, as well as in all tested fetal organs (brain, lung, spleen, liver and thymus). This report provides the first evidence for transplacental transmission of T. gondii in a chronically infected wild sea otter, and the first molecular and immunohistochemical confirmation of concurrent transplacental transmission of T. gondii and S. neurona in any species. Repeated fetal and/or neonatal losses in the sea otter dam also suggested that T. gondii has the potential to reduce fecundity in chronically infected marine mammals through parasite recrudescence and repeated fetal infection.

Psoroptic sheep scab and psoroptic otoacariasis of domestic rabbits occur in the same geographical regions of Switzerland. To address the question as to whether Psoroptes mites are naturally transmitted between sheep and rabbits, we determined the sequences of the rDNA second internal transcribed spacer (ITS-2) from psoroptic mites from sheep (5 field isolates from Switzerland and 2 laboratory isolates from Ireland and the UK) and from rabbits (8 field isolates from Switzerland). The ITS-2 sequences for all Psoroptes mites originating from sheep were identical and differed at 1 nucleotide position from all the sequences of the rabbit-derived isolates. A statistically significant difference between a rabbit-derived isolate and isolates originating from sheep was also obtained by morphometric analysis of the lengths of the outer opisthosomal setae. For comparative purposes, the ITS-2 sequences from Chorioptes and Sarcoptes collected in Switzerland were also determined. No intraspecies variation was found in 6 sarcoptic isolates from red foxes, with a sequence identity of 41% as compared to Psoroptes. The ITS-2 sequences of 3 chorioptic isolates differed by 24–29% from the Psoroptes sequence. Identical sequences were found for the Chorioptes isolates from sheep and a camel, which differed by 18% from the sequence of an isolate from a cow. These genetic data of psoroptic mites originating from sheep and rabbits from the same geographical area suggest the existence of epidemiologically separated populations.

Biological invasions expose parasites to new invasive hosts in addition to their local hosts. However, local parasites are often less successful in infecting and exploiting their new hosts. This may have major consequences for the competitive ability of hosts, and finally on the fate of the parasite-host community. In Burgundy (Eastern France), the acanthocephalan parasite, Pomphorhynchus laevis, infects 2 amphipod species living in sympatry: the native Gammarus pulex and the invasive Gammarus roeseli. While P. laevis affects the behaviour and the immunity of G. pulex, G. roeseli seems unaffected by the infection. In this study, we examined in detail the ability of the parasite to affect the immune system and resource storage of both gammarid species. We found that the infection was associated with a general decrease of the prophenoloxidase activity, haemocyte density, resistance to an artificial bacterial infection and level of sugar reserves in G. pulex, but not in G. roeseli. These results demonstrate a differential ability of P. laevis to exploit its local and its invasive gammarid hosts. Potential mechanisms of these differential physiological alterations and their potential consequences on the coexistence of both gammarid species in sympatry are discussed.

An ELISA was developed for serological detection of Echinococcus granulosus infection in dromedary camels. Antigen B (AgB) partially purified from hydatid cyst fluid of camels or sheep naturally infected with cystic echinococcosis (CE) due to E. granulosus, as well as a recombinant antigen B product (r-AgB) were used in an ELISA to screen panels of serum samples from slaughtered camels naturally infected with CE. Native hydatid cyst fluid antigen preparations were able to detect antibodies in sera from a significant proportion of camels with CE, as confirmed at post-mortem. Seroreactivity however, was variable. ELISA specificity for sera from naturally infected camels versus inspection-negative animals ranged from 90 to 99%. Native antigen B gave the highest sensitivity (97%) in ELISA for camel CE confirmed at slaughter. In contrast, r-AgB gave lower sensitivity for camel (84%) and sheep (28%) CE. The r-AgB-ELISA was, however, highly specific (90 and 95%) respectively for both camel and sheep natural CE infection. These results indicate that an ELISA based on serum antibody detection to AgB could be developed for immunodiagnosis of cystic echinococcosis in camels.

The flagellated parasite Giardia duodenalis is known as one of the most common causes of protozoal diarrhoea in both humans and animals worldwide. The aim of the present work was to perform the first study of G. duodenalis in rodents in the Canary Islands (Spain) and analyse the level of genetic variation and the potential zoonotic role of the isolates. Stool samples were collected from 284 wild rodents and Giardia cysts were detected by light microscopy. The overall prevalence of giardiasis was 25·4% and ranged from 19·4% in El Hierro to 34% in Gran Canaria. Positive samples were further characterized by PCR and nucleotide sequencing of the triose phosphate isomerase (TPI), β-giardin (BG) and glutamate dehydrogenase (GDH) genes. Our study revealed assemblage G as the most frequent genotype and identified two rodent-infecting G. duodenalis haplotypes of this assemblage, HI and HII. Phylogenetic analysis supported the monophyly of haplotype HI, which we suggest to be considered as a novel G. duodenalis sub-assemblage GII, due to the high genetic distances among this sub-genotype and assemblage G. Furthermore, G. duodenalis assemblage B was detected in an inhabited area in La Palma, a fact that may pose a potential risk of G. duodenalis transmission from rodents to humans.

Parasitic infection often results in alterations to the host's phenotype, and may modify selection pressures for host populations. Elucidating the mechanisms underlying these changes is essential to understand the evolution of host–parasite interactions. A variety of mechanisms may result in changes in the host's behavioural phenotype, ranging from simple by-products of infection to chemicals directly released by the parasite to alter behaviour. Another possibility may involve parasites freely moving to certain sites within tissues, at specific times of the day to induce behavioural changes in the host. We tested the hypothesis that parasites shift to certain sites within the host by quantifying the location and activity of the trematode Tylodelphys sp., whose mobile metacercarial stages remain unencysted in the eyes of the second intermediate fish host, the common bully (Gobiomorphus cotidianus). This parasite's definitive host is a piscivorous bird feeding exclusively during daytime. Ocular obstruction and metacercarial activity were assessed within the sedated host's eye at three time points 24 h−1 period, using video captured via an ophthalmoscope. Although observed metacercarial activity did not change between time periods, ocular obstruction was significantly reduced at night. Increased visual obstruction specifically during the foraging time of the parasite's definitive host strongly suggests that the parasite's activity pattern is adaptive.

Franz cells (2-chambered, air/fluid phase static diffusion devices, previously used for the study of drugs across viable human skin) are utilized for the first time to investigate the process of infection of human skin by Schistosoma mansoni cercariae. Skin obtained from cosmetic surgery sources was used in the Franz cells to describe the temporal dynamics of the early interaction of cercariae with skin. At 38 °C, about 50% of cercariae applied in water to the epidermal surface of the skin were irreversibly attached within 1 min and after 5 min about 85% were similarly irrecoverable. The technique also provides the means of following the early penetration path of cercariae by histological methods. Franz cell results on the dynamics of attachment/early penetration have been compared with those obtained using artificial skin equivalents and non-human mammalian skin models in the context of the physical and chemical differences between these systems and viable human skin. It is concluded that Franz cells provide a convenient system for directly investigating the early phases of S. mansoni cercariae interaction with human skin.

Arid zones of northern Venezuela are represented by isolated areas, important from an ornithological and ecological perspective due to the occurrence of restricted-range species of birds. We analysed the prevalence and molecular diversity of haemosporidian parasites of wild birds in this region by screening 527 individuals (11 families and 20 species) for parasite mitochondrial DNA. The overall prevalence of parasites was 41%, representing 17 mitochondrial lineages: 7 of Plasmodium and 10 of Haemoproteus. Two parasite lineages occurred in both the eastern and western regions infecting a single host species, Mimus gilvus. These lineages are also present throughout northern and central Venezuela in a variety of arid and mesic habitats. Some lineages found in this study in northern Venezuela have also been observed in different localities in the Americas, including the West Indies. In spite of the widespread distributions of some of the parasite lineages found in northern Venezuela, several, including some that are relatively common (e.g. Ven05 and Ven06), have not been reported from elsewhere. Additional studies are needed to characterize the host and geographical distribution of avian malaria parasite lineages, which will provide a better understanding of the influence of landscape, vector abundance and diversity, and host identity on haemosporidian parasite diversity and prevalence.

In case of cercarial dermatitis after exposure to fresh water lakes, managers responsible for bathing water quality wish to confirm the presence of Trichobilharzia, which substantiates taking measures to protect bathers from further exposure. A novel approach, including concentration of suspected water samples by filtration and PCR detection of the parasite, is proposed. This approach has been applied to bathing sites with a history of cercarial dermatitis, sampled from 2005 to 2008. Examination of snails, the standard procedure for confirmation of the parasite's presence, and analysis of water samples, appear to be complementary procedures that enhance the chance of parasite detection in implicated bathing water. Water analysis is particularly valuable when snails cannot be found; it confirmed the presence of Trichobilharzia on 25% of sampling days with reported skin conditions and no snails found. PCR of the ToSau3A repeat directly confirmed the parasite in the water. The application of the combination of analysis of water samples and examination of snails is suggested when cases of (presumptive) cercarial dermatitis are reported or when lakes with a history of cercarial dermatitis are inspected prior to the bathing season, in order to guide interventions to prevent (further) cases of swimmers' itch.

Cryptosporidium species are protozoan parasites that infect humans and a wide variety of animals. This study was aimed at identifying Cryptosporidium species and genotypes isolated from avian hosts. A total of 90 samples from 37 different species of birds were collected throughout a 3-month period from April 2008 to June 2008 in the National Zoo of Kuala Lumpur, Malaysia. Prior to molecular characterization, all samples were screened for Cryptosporidium using a modified Ziehl-Neelsen staining technique. Subsequently samples were analysed with nested-PCR targeting the partial SSU rRNA gene. Amplicons were sequenced in both directions and used for phylogenetic analysis using Neighbour-Joining and Maximum Parsimony methods. Although 9 (10%) samples were positive for Cryptosporidium via microscopy, 8 (8·9%) produced amplicons using nested PCR. Phylogenetic trees identified all the isolates as Cryptosporidium parvum. Although C. parvum has not been reported to cause infection in birds, and the role of birds in this study was postulated mainly as mechanical transporters, these present findings highlight the significant public health risk posed by birds that harbour the zoonotic species of Cryptosporidium.

Understanding the origin of invasive parasites and ecological transmission barriers on the distribution of mosquito-borne pathogens is enriched by molecular phylogenetic approaches now that large databases are becoming available. Here we assess the biogeographical relationships among haemosporidian blood parasites and an avian host, the New Zealand bellbird (Meliphagidae, Anthornis melanura). Four Plasmodium haplotypes were identified among 93 infected bellbirds (693 screened) using nested PCR of a mitochondrial DNA cytochrome b gene fragment. The most common lineage, LIN1 (11%), is confined to northern New Zealand and falls within a known clade of Plasmodium (subgenus Novyella) sp. infecting Australian meliphagids. LIN1 differs within that clade by 4 9% sequence divergence suggestive of an endemic lineage to New Zealand. The most widespread lineage, LIN2 (2%), is an exact match with a global cosmopolitan (P. elongatum GRW06). Two rare lineages, LIN3 and LIN4 are less abundant, geographically restricted within New Zealand and have <1% sequence divergence with P. (Novyella) sp. (AFTRU08) and P. relictum (LINOLI01) documented from Africa. For the first time, we provide invaluable information on possible rates of entry of invading parasites in New Zealand and their distribution from temperate to cold environments.

Each transmission event in complex, multi-host life cycles create obstacles selecting for adaptations by trematodes. One such adaptation is life cycle abbreviation through progenesis, in which the trematode precociously matures and reproduces within the second intermediate host. Progenesis eliminates the need for the definitive host and increases the chance of life cycle completion. However, progenetic individuals face egg-dispersal challenges associated with reproducing within metacercarial cysts in the tissues or body cavity of the second intermediate host. Most progenetic species await host death for their eggs to be released into the environment. The present study investigated temporal variation of progenesis in Stegodexamene anguillae in one of its second intermediate fish hosts and the effect of the fish's reproductive cycle on progenesis. The study involved monthly sampling over 13 months at one locality. A greater proportion of individuals became progenetic in the gonads of female fish hosts. Additionally, progenesis of worms in the gonads was correlated with seasonal daylight and temperature changes, major factors controlling fish reproduction. Host spawning events are likely to be an avenue of egg dispersal for this progenetic species, with the adoption of progenesis being conditional on whether or not the parasite can benefit from fish spawning.

Immunoprophylactic products against neosporosis during pregnancy should induce an appropriately balanced immune response. In this respect, OprI, a bacterial lipoprotein targeting toll like receptor (TLR)2, provides promising adjuvant properties. We report on the manipulation of the innate and the T-cell immune response through the fusion of OprI with the Neospora caninum chimeric protein Mic3-1-R. In contrast to Mic3-1-R, OprI-MIC3-1-R significantly activated bone-marrow dendritic cells from naïve mice. Mice immunized with OprI-Mic3-1-R induced an immune response with mixed T helper (Th)1 and Th2 properties (high levels of both immunoglobulin (Ig)G1 and IgG2a and of interleukin (IL)-10, IL-12(p70) and interferon-γ responses) whereas Mic3-1-R+saponin induced a clear Th2-biased response (low IgG2a and high IL-4 and IL-10). After mating and challenge with N. caninum, increased expression of interferon-γ was only found in placentas from OprI-Mic3-1-R immunized dams. However, no protection against vertical transmission and neonatal mortality was observed in either of the two groups. These results indicated that more exhaustive studies must be done to elucidate the immune mechanisms associated with transplacental transmission. Antigen linkage to TLR2-ligands, such as OprI, is a useful tool to investigate this enigma by reorienting the innate and adaptive immune responses against other candidate antigens in future studies.

Acquisition of acute toxoplasmosis during the first trimester of pregnancy can have catastrophic consequences for the foetus. Diagnosis is routinely based on the detection of maternal Toxoplasma gondii – antibodies using whole parasite extracts as detection antigen. While such assays are sensitive, they show no specificity for the stage of infection. We hypothesized diagnosis might be improved using recombinant antigens for detection, particularly if antibodies to certain antigen(s) were associated with early or late stages of infection. To address this, protein microarrays comprising 1513 T. gondii exon products were probed with well-characterized sera from seronegative (‘N’) controls, and acute (‘A’), chronic/IgM-persisting (‘C/M’) and chronic (‘C’) toxoplasmosis cases from Turkey. Three reactive exon products recognized preferentially in A infections, and three recognized preferentially in C/M infections, were expressed in Escherichia coli and tested for discrimination in IgG ELISAs. The best discriminators were exon 1 of TGME49_086450 (GRA5) which detected C/M infections with 70·6% sensitivity and 81·8% specificity, and exon 6 of TGME49_095700 (ubiquitin transferase domain-containing protein) which detected A infections with 84·8% sensitivity and 82·4% specificity. Overall, the data support a recombinant protein approach for the development of improved serodiagnostic tests for toxoplasmosis.

Pentameric ligand-gated ion-channels rapidly transduce synaptic neurotransmitter signals to an electrical response in post-synaptic neuronal or muscle cells and control the neuromusculature of a majority of multicellular animals. A wide range of pharmaceuticals target these receptors including ethanol, nicotine, anti-depressants and other mood regulating drugs, compounds that control pain and mobility and are targeted by a majority of anthelmintic drugs used to control parasitic infection of humans and livestock. Major advances have been made in recent years to our understanding of the structure, function, activity and the profile of compounds that can activate specific receptors. It is becoming clear that these anthelmintic drug targets are not fixed, but differ in significant details from one nematode species to another. Here we review what is known about the evolution of the pentameric ligand-gated ion-channels, paying particular attention to the nematodes, how we can infer the origins of such receptors and understand the factors that determine how they change both over time and from one species to another. Using this knowledge provides a biological framework in which to understand these important drug targets and avenues to identify new receptors and aid the search for new anthelmintic drugs.

A cDNA encoding the immunogen Pso o 1 from Psoroptes ovis was obtained by polymerase chain reaction (PCR) amplification. The amplicon contained the entire coding sequence for the prepro-enzyme in an open reading frame (ORF) of 966 bp. This gene encoded a predicted protein of 322 amino acids (aa) with 64% aa identity (80% similarity) to the major house dust mite faecal allergen Der f 1. The pro-enzyme form of Pso o 1 was expressed as a recombinant protein in the Pichia pastoris-eukaryotic expression system. Maturation of the recombinant pro-enzyme by autocatalytic activation was not observed, and such maturation could not be achieved using a number of techniques known to activate recombinant Der p 1 and Der f 1 expressed in the same system. Serum raised against recombinant Pso o 1 cross-reacted with mature Der p 1 and allowed Pso o 1 to be immunolocalized to the gut of P. ovis.

A study has been carried out to determine whether the action of triclabendazole (TCBZ) against the liver fluke, Fasciola hepatica is altered by inhibition of the cytochrome P450 (CYP 450)-mediated drug metabolism pathway. The Oberon TCBZ-resistant and Cullompton TCBZ-susceptible fluke isolates were used for these experiments, the basic design of which is given in the paper by Devine et al. (2010a). Piperonyl butoxide (PB) was the CYP P450 inhibitor used. Morphological changes resulting from drug treatment and following metabolic inhibition were assessed by means of transmission electron microscopy. After treatment with either TCBZ or TCBZ.SO on their own, there was greater disruption to the TCBZ-susceptible than TCBZ–resistant isolate. However, co-incubation with PB+TCBZ, but more particularly PB+TCBZ.SO, led to greater changes to the TCBZ-resistant isolate than with each drug on its own, with blebbing of the apical plasma membrane, severe swelling of the basal infolds and their associated mucopolysaccharide masses in the syncytium and flooding in the internal tissues. Golgi complexes were greatly reduced or absent in the tegumental cells and the synthesis and production of secretory bodies were badly disrupted. The mitochondria were swollen throughout the tegumental system and the somatic muscle blocks were disrupted. With the TCBZ-susceptible Cullompton isolate, there was a limited increase in drug action following co-incubation with PB. The results provide evidence that the condition of a TCBZ-resistant fluke can be altered by inhibition of drug metabolism. Moreover, they support the concept that altered drug metabolism contributes to the mechanism of resistance to TCBZ.

The parasitic roundworms Strongyloides stercoralis (in man) and Strongyloides ratti (in rats) employ environmentally controlled XX/XO sex determination with a pair of X chromosomes and two pairs of autosomes. Strongyloides papillosus (in sheep) has only two pairs of chromosomes, one of which combines the genetic material homologous to the S. ratti chromosomes X and I. This species creates males through the elimination of one copy of the portion related to the X chromosome (chromatin diminution). It is not clear which one of these two sex-determining mechanisms is ancestral. We demonstrate that Strongyloides vituli (in cattle) has two pairs of chromosomes like its very close relative S. papillosus whereas Parastrongyloides trichosuri, a closely related out-group to Strongyloides spp. in Australian brushtail possums, has three chromosome pairs and employs XX/XO sex determination. The X chromosome of P. trichosuri is homologous to the X chromosome of S. ratti. Our data strongly suggest that the last common ancestor of Strongyloides spp. and Parastrongyloides spp. had two pairs of autosomes along with two or one X chromosome in females and males, respectively. The situation with two pairs of chromosomes is likely derived and occurred through the fusion of the X chromosome with an autosome.