The humoral innate immune response of gilthead seabream (Sparus aurata L.) against the myxozoan Enteromyxum leei has been studied. At 10, 22, 38, 52 and 108 days of cohabitation fish were sampled to examine gut histology and to determine serum innate immune parameters and the mRNA expression of pro-inflammatory cytokines (IL-1β and TNFα) in head-kidney. The parasite was successfully transmitted to 45% of the recipient fish and prevalence reached a maximum (62·5%) at the last sampling time (108 days). Recipient fish started to die after 74 days of cohabitation. In general, alternative complement activity was higher whereas the peroxidase level was lower in recipient fish than in controls. Moreover, IL-1β mRNA expression increased while the TNFα gene expression decreased in recipient fish. These data demonstrate the involvement of complement activity in the defence mechanisms of the gilthead seabream against the myxosporean E. leei. Within the recipient fish group, few differences were observed in the studied immune parameters between E. leei-parasitized and non-parasitized recipient fish. Parasitological and immunological implications of E. leei infections in Mediterranean fish farms are discussed.

There is unequivocal evidence that parasites influence the immune activity of their hosts, and many of the classical examples of this are drawn from assessment of helminth infections of their mammalian hosts. Thus, helminth infections can impact on the induction or course of other diseases that the host might be subjected to. Epidemiological studies demonstrate that world regions with high rates of helminth infections consistently have reduced incidences of autoimmune and other allergic/inflammatory-type conditions. Here I review and assess the possible ways by which helminth infections can block or modulate concomitant disease processes. There is much to be learned from careful analysis of immuno-regulation in helminth-infected rodents and from an understanding of the immune status of acutely and chronically infected humans. The ultimate reward from this type of investigation will likely be a more comprehensive knowledge of immunity, novel ways to intervene in the immune response to alleviate autoimmune and allergic diseases (growing concerns in economically developed areas), and perhaps the development of helminth therapy for patients suffering from specific inflammatory, autoimmune or allergic disorders.

The effect of acquired immunity on the duration of Plasmodium falciparum infections is unclear, although this is an important term in models of malaria transmission. It is problematical to determine the duration of infections because of the difficulty of distinguishing persisting infections from new ones, and because parasite densities are often transiently below the limit of detection. We recently developed a dynamic model for infection incidence, clearance and detection of multiple genotype P. falciparum infections and fitted it to a panel dataset from a longitudinal study in Northern Ghana. We now extend this model to allow for seasonal and age variation in infection rates and also age dependence in clearance and in detectability of infections. These models indicate that there is seasonal variation in the infection rate, and age dependence in detectability. The best fitting models had no age dependence in infection or clearance rates, suggesting that acquired immunity mainly affects detectability.

Multiple infections, those by more than one parasite in the same erythrocyte, may be adaptive for the malarial parasite as a means to ensure fertility. Alternatively they may simply be the consequence of a non-adaptive process forcing several parasites to compete for resources in one host cell. Avian hosts infected with Haemoproteus were medicated with primaquine or injected with saline solution and the density of infection and number, maturity and sex of mature multiple infections counted. Multiple infections depend on density of infection, and maturity is attained rarely and usually by gametocytes of the same sex. The role of multiple infections for fertility insurance is not supported by these results.

Neospora caninum and Toxoplasma gondii are closely related intracellular protozoan parasites associated with bovine and ovine abortion respectively. Little is known about the extent of Neospora/Toxoplasma co-infection in naturally infected populations of animals. Using nested PCR techniques, based on primers from the Nc5 region of N. caninum and SAG1 for T. gondii, the prevalence of N. caninum and its co-infection with T. gondii were investigated in populations of Mus domesticus, Rattus norvegicus and aborted lambs (Ovis aries). A low frequency of infection with N. caninum was detected in the Mus domesticus (3%) and Rattus norvegicus (4·4%) populations. A relatively high frequency of infection with N. caninum was detected in the brains of aborted lambs (18·9%). There was no significant relationship between N. caninum and T. gondii co-infection. Investigation of the tissue distribution of Neospora, in aborted lambs, showed that Neospora could not be detected in tissues other than brain and this was in contrast to Toxoplasma where the parasite could be frequently detected in a range of tissues.

In previous studies, we showed that Herpetomonas samuelpessoai produced a large amount of a surface-located metallopeptidase that presented similar biochemical properties to that of gp63 from Leishmania spp., which is a well-known virulence factor expressed by these digenetic parasites. The present study aims to identify the proteolytic activity released by living H. samuelpessoai cells. In this context, the parasites were incubated in phosphate buffer up to 4 h, and the supernatants were obtained by centrifugation and filtration steps and were then applied on SDS–PAGE to determine the secretory protein profile and on gelatin-SDS–PAGE to identify the proteolytic activity. The results demonstrated that H. samuelpessoai secreted at least 12 polypeptides and an extracellular peptidase of 66 kDa. This enzyme had its activity diminished by 1,10-phenanthroline, EDTA and EGTA. This metallopeptidase was active in a broad spectrum of pH, showing maximum activity at pH 6·0 at 37 °C. Casein was also cleaved by this secretory proteolytic enzyme, while bovine serum albumin and haemoglobin were not degraded under these conditions. Fluorescence microscopy and flow cytometry using anti-gp63 antibody against leishmanolysin of L. amazonensis demonstrated the presence of similar molecules on the cell-surface of H. samuelpessoai. Moreover, immunoblot analysis showed the presence of a reactive polypeptide in the cellular extract and in the supernatant fluid of H. samuelpessoai, which suggests immunological similarities between these two distinct trypanosomatids. The zinc-metallopeptidase inhibitor 1,10-phenanthroline was able to inhibit the secretion of the 66 kDa metallopeptidase in a dose-dependent manner, while the phospholipase C inhibitor (p-CMPS) did not alter the secretion pattern. Additionally, anti-cross-reacting determinant (CRD) antibody failed to recognize any secreted polypeptide from H. samuelpessoai. Collectively, these results suggest that the gp63-like molecule was released from the H. samuelpessoai surface by proteolysis instead of phospholipolysis, in a similar mechanism to that observed in Leishmania.

The outcome and the evolution of host-symbiont associations depend on environmental constraints, but responses are difficult to predict since they arise from a complex interaction between the host, the parasite and the environment. The situation can be even more complex when multiple parasite genotypes, with potentially different responses to environmental changes, coexist within a single host. In this paper, we investigated the effect of the temperature (from 14 to 26 °C) during the host development on the density of 3 strains of the intracellular bacterium Wolbachia that coexist within the wasp Leptopilina heterotoma. In this species, Wolbachia induces cytoplasmic incompatibility, a sperm-egg incompatibility that allows it to spread and persist in host populations. Using real-time quantitative PCR we found that (i) Wolbachia density is temperature-specific and highest at 26 °C; (ii) the order of the abundance of the 3 Wolbachia strains does not vary with temperature changes; (iii) the response of bacterial density to temperature occurs within a single insect generation, during the egg-to-adult developmental period; (iv) in this species, temperature-related changes in Wolbachia density do not influence cytoplasmic incompatibility.

This study applied improved DNA extraction and polymerase chain reaction strategies for screening and identification of Trypanosoma cruzi lineages directly from faeces of triatomines collected in a well-defined rural area in northwestern Argentina. Amplification of the variable regions of the kinetoplastid minicircle genome (kDNA-PCR) was performed in faecal lysates from 33 microscope (MO)-positive and 93 MO-negative Triatoma infestans, 2 MO-positive and 38 MO-negative Triatoma guasayana and 2 MO-positive and 73 MO-negative Triatoma garciabesi. kDNA-PCR detected T. cruzi in 91% MO-positive and 7·5% MO-negative T. infestans, which were confirmed by amplification of the minicircle conserved region. In contrast, kDNA-PCR was negative in all faecal samples from the other triatomine species. A panel of PCR-based genomic markers (intergenic region of spliced-leader DNA, 24Sα and 18S rRNA genes and A10 sequence) was implemented to identify the parasite lineages directly in DNA lysates from faeces and culture isolates from 28 infected specimens. Two were found to be infected with TCI, 24 with TCIIe, 1 with TCIId and 1 revealed a mixed TCI+TCII infection in the faecal sample whose corresponding culture only showed TCII, providing evidence of the advantages of direct typing of biological samples. This study provides an upgrade in the current diagnosis and lineage identification of T. cruzi in field-collected triatomines and shows T. cruziII strains as predominant in the region.

The protective efficacy of a Schistosoma japonicum, Chinese strain, triose-phosphate isomerase (TPI) plasmid DNA vaccine was examined in naïve pigs. Pigs were vaccinated with the TPI DNA-plasmid alone, or in conjunction with IL-12 as pcDNA3.1-P35, pcDNA3.1-P40 plasmids via intramuscular injection. Control pigs were immunized with equivalent amounts of pcDNA3.1. Pigs were immunized 3 times at 21-day intervals and challenged 30 days after the final boost. Forty-five days post-challenge, pigs were sacrificed and perfused to compare adult worm burdens, female worm burdens, liver egg burdens and granuloma size. We found that pigs vaccinated with SjCTPI DNA alone had adult worm burdens reduced by 48·3% and that a further decrease in adult worm burdens was not seen in the group vaccinated with SjCTPI DNA in conjunction with IL-12 (46·2% reduction). The SjCTPI DNA vaccines had a more pronounced effect on reducing female worm burdens i.e. 53·6% SjCTPI alone and 59·6% for SjCTPI+IL-12. Vaccination with SjCTPI-DNA reduced liver eggs by 49·4% and this response was significantly enhanced by the addition of IL-12 (65·8% reduction in liver eggs). In addition to the dramatic protective effects seen in vaccinated pigs, we also noted that granuloma size was reduced by 42% in both groups. Thus, vaccination of pigs and other large animals in China with SjCTPI DNA vaccine will likely reduce transmission by reducing adult worm burdens and worm egg output and simultaneously reduce hepatic egg-associated pathology.

Our preliminary observation, that sera from schistosomiasis patients react with carcinomas, raised the possibility of antigenic cross-reactivity. We here extend this observation to show that mice experimentally infected with Schistosoma mansoni react with human urothelial and transitional bladder carcinomas and also with a gastric carcinoma cell line, AGS. To identify cross-reacting epitopes, we looked for the expression of carcinoma markers in schistosome worms and eggs using monoclonal antibodies against tumour antigens MUC1, Tn and TF (also known as the oncofetal Thomsen-Friedenreich antigen or T antigen). Immunohistochemical staining showed that the TF-epitope is present in adult intravascular S. mansoni worms and eggs deposited in tissues of infected animals. The localization of TF-immuno-reactive material in schistosomes was seen at the parasite surface between male and female worms and around trapped eggs in the liver. This localization is consistent with the antigen being secreted. Mice experimentally infected with S. mansoni, developed circulating antibodies against the TF-epitope (identified as Gal(beta1-3) GalNAc-O-R) as seen in ELISA using TF-expressing asialoglycophorin (AGP) as antigen. The observed anti-TF response in S. mansoni-infected mice reflects the complexity of host-parasite interactions in this infection.

The present study aimed to search for and characterize parasite molecules, whose expression levels correlate with the viability and growth activity of Echinococcus multilocularis metacestodes. We focused on the expression profiles of 2 parasite-derived genes, 14-3-3 and II/3-10, as putative molecular markers for viability and growth activity of the larval parasite. In experiments in vivo, gene expression levels of 14-3-3 and II/3-10 were relatively quantified by real-time reverse transcription-PCR using a housekeeping gene, beta-actin, as a reference reaction. All three reactions were compared with growth activity of the parasite developing in permissive nu/nu and in non-permissive wild type BALB/c mice. At 2 months p.i., the transcription level of 14-3-3 was significantly higher in parasites actively proliferating in nu/nu mice compared to parasites moderately growing in wild type mice. Immunoblotting experiments confirmed at the protein level that 14-3-3 was over-expressed in parasites derived from nu/nu mice at 2 months p.i. In vitro treatment of E. multilocularis with an anti-echinococcal drug nitazoxanide resulted in a significant decrease of both 14-3-3 and II/3-10 transcription levels found after 8 days of treatment, which correlated with the kinetics of a housekeeping gene, beta-actin. The conclusion is that 14-3-3, combined with II/3-10, exhibits good potential as a molecular marker to assess viability and growth activity of the parasite.

We investigated population differences in immunological adaptation of three-spined sticklebacks (Gasterosteus aculeatus) to one of their most abundant macroparasites, the eye fluke Diplostomum pseudospathaceum. We compared infection success in lab-bred fish of 2 populations in northern Germany, from a lake, where eye flukes are prevalent, and a river, where these parasites do not occur. In order to discriminate between protection through innate and acquired immunity, we exposed fish either only once or repeatedly. Lake fish were significantly less susceptible than river sticklebacks already after a single exposure, indicating that in sympatric hosts innate immunity plays the major role in the defence against this helminth infection. In both habitat types, previous exposures only marginally decreased infection rates within 12 weeks. Lake fish showed higher immunocompentence by means of respiratory burst activity and spleen size, regardless of the infection status. Furthermore, they were in a better energy status than river fish, as indicated by a higher hepatosomatic index and haematocrit value. Interestingly, F1 hybrid fish of both populations ranged between the pure habitat types in parasite susceptibility as well as in immunological and condition parameters. Our results suggest that sticklebacks from lakes are better adapted to cope with higher parasite abundance in this habitat.

We have cloned a cDNA encoding a novel antigen from a Sarcoptes scabiei (Acari) cDNA library by immunoscreening with sera from S. scabiei-infected dogs. The antigen is encoded by a 2157 bp mRNA with a predicted open reading frame of 719 amino acids (molecular weight 79 kDa). Our sequence analysis identified the presence of a MADF domain in the N-terminus, and downstream of this domain there was a region of low sequence complexity. This latter region contained several blocks of triplets and quadruplets of polar amino acids (Asn, Gln and Ser), and these 3 amino acids represented 39·7% of all amino acids. The antigen was named Atypical Sarcoptes Antigen 1 (ASA1) since the MADF domain normally is found in proteins involved in transcriptional regulation. In addition, 15 out of 62 S. scabiei-infected dogs reacted with a purified recombinant version of ASA1 in Western blot analysis. With immunohistochemistry we could show that ASA1 is expressed throughout the parasite, and that IgG specific for ASA1 binds to the inside wall of the mite's burrow. To our knowledge, this is the first description of an antigen containing an MADF domain.

Trypanosomosis is a major cause of mortality for dogs in Nigeria and treatment with diminazene aceturate has steadily become less effective, either as a result of low quality of the locally available diminazene preparations or of drug resistance. To investigate these alternatives, samples of locally obtained drugs were analysed for diminazene aceturate content and a strain of Trypanosoma brucei brucei was isolated from a diminazene-refractory dog in Nsukka, south-eastern Nigeria, and used to infect albino rats. The quality of diminazene aceturate-based preparations was variable, with two preparations containing less than 95% of the stated active compound. Rats infected with T. brucei isolated from the dog were treated 7 and 10 days after infection either with 7 mg/kg diminazene aceturate (intraperitoneally, once) or with 4 mg/kg pentamidine isethionate (intramuscularly, 7 consecutive days). Relapse rates were 100% for both trypanocides in the groups of rat treated 10 days post-infection, and 83% and 50% of rats treated 7 days after infection relapsed to diminazene aceturate and pentamidine isethionate, respectively. Careful consideration of physiological parameters showed that pentamidine was only marginally superior to diminazene aceturate as applied in this study. It was concluded that dogs in Nigeria are infected with genuinely diminazene aceturate-resistant trypanosomes that appear to be cross-resistant to pentamidine isethionate.

Alternative transmission strategies are common in many parasitic organisms, often representing discrete phenotypes adopted in response to external cues. The facultative truncation of the normal 3-host life-cycle to a 2-host cycle in many trematodes provides an example: some individuals mature precociously, via progenesis, in their intermediate host and produce eggs without the need to reach a definitive host. The factors that determine how many and which individuals adopt the truncated life-cycle within a parasite population remain unknown. We investigated the occurrence of progenesis in the trematode Stegodexamene anguillae within its fish intermediate host. Location within the host was a key determinant of progenesis. Although the size and egg output of progenetic metacercariae encysted in host gonads did not differ from those of the few progenetic metacercariae in other host tissues, the likelihood of metacercariae becoming progenetic was much higher for those in the gonads than those elsewhere in the host. Progenetic parasites can only evacuate their eggs along with host eggs or sperm, providing a link between the parasite's transmission strategy and its location in the host. Host size and sex, and the presence of other parasite species in the host, did not affect the occurrence of progenesis in S. anguillae. However, the proportion of metacercariae in host gonads and the proportion of progenetic metacercariae both decreased with increasing numbers of S. anguillae per host. These results suggest that progenesis is adopted mostly by the parasites that successfully establish in host gonads. These are generally the first to infect a fish; subsequent arrivals settle in other tissues as the gonads quickly become saturated with parasites. In this system, the site of encystment within the fish host both promotes and constrains the adoption of a facultative, truncated life-cycle by the parasite.

Global warming can affect the world's biota and the functioning of ecosystems in many indirect ways. Recent evidence indicates that climate change can alter the geographical distribution of parasitic diseases, with potentially drastic consequences for their hosts. It is also possible that warmer conditions could promote the transmission of parasites and raise their local abundance. Here I have compiled experimental data on the effect of temperature on the emergence of infective stages (cercariae) of trematode parasites from their snail intermediate hosts. Temperature-mediated changes in cercarial output varied widely among trematode species, from small reductions to 200-fold increases in response to a 10 °C rise in temperature, with a geometric mean suggesting an almost 8-fold increase. Overall, the observed temperature-mediated increases in cercarial output are much more substantial than those expected from basic physiological processes, for which 2- to 3-fold increases are normally seen. Some of the most extreme increases in cercarial output may be artefacts of the methods used in the original studies; however, exclusion of these extreme values has little impact on the preceding conclusion. Across both species values and phylogenetically independent contrasts, neither the magnitude of the initial cercarial output nor the shell size of the snail host correlated with the relative increase in cercarial production mediated by rising temperature. In contrast, the latitude from which the snail-trematode association originated correlated negatively with temperature-mediated increases in cercarial production: within the 20 ° to 55 ° latitude range, trematodes from lower latitudes showed more pronounced temperature-driven increases in cercarial output than those from higher latitudes. These results suggest that the small increases in air and water temperature forecast by many climate models will not only influence the geographical distribution of some diseases, but may also promote the proliferation of their infective stages in many ecosystems.

Vector biology has become a fast moving field. Spurred on by the recent exciting advances in the molecular biology, genomics and latterly proteomics of vector insects and their pathogens, researchers are using new approaches and our knowledge is rapidly increasing. The second edition of this volume very much reflects these advances. The editor, William Marquardt, has assembled a team of section editors to oversee the production of 57 short chapters, divided into 7 parts. With a few exceptions, these experts are drawn from the USA, a reflection no doubt of the history of the first edition which was produced to accompany the Biology of Vector Disease course, given at Colorado State University. The text is aimed at post-graduate and post-doctoral researchers, working in a range of areas associated with vector biology and vector-borne diseases. It provides an excellent opportunity to obtain an initial overview of a new area or to dip into a field that may be peripheral to the topic under investigation.

Trematodes (flukes or digeneans) are by far the most abundant group of parasitic flatworms (Neodermata), and their importance for human and animal health is indisputable. In addition, they exhibit a variety of unique adaptations to parasitism and, probably most remarkably, possess extraordinarily complicated life-cycles. Classification of trematodes represents a very difficult task due to the huge number of existing species and variety of morphological forms, sites of infection within invertebrate and vertebrate hosts and ability to infect a wide spectrum of animals. Therefore, identification of any trematode may represent a problem even for an experienced specialist. This is the reason why I appreciated so much the publication of the first volume of the Keys to the Trematoda in 2002.

Fish parasitology has become an enormous field. The preface to this volume explains that the scope has been trimmed by focusing on those parasites most likely to be encountered by aquarists, anglers and naturalists – the external parasites; this approach excludes tapeworms, nematodes and most protozoans. The examples are mainly taken from the British fauna, but readers from other regions will find the subjects familiar.

This book is dedicated to my Ph.D. advisor, Neil Croll (1941–1981), whose seminal text “The Behaviour of Nematodes” launched the field in 1970. The current effort is a thick, heavy tome when compared to Croll's slim and elegant little book, directly reflecting the explosion of interest in the topic, due in no small part to a single nematode Caenorhabiditis elegans. However, C. elegans is not the star of this book. The present effort is meant to be broad in its taxonomic scope, attempting to consolidate disparate nematode behaviours into a comprehensive up-to-date volume. Indeed, this is a formidable task in a world in which 4 out of every 5 metazoans is a nematode, and the end result is a bit uneven. To cover the taxonomic breadth, several chapters focused on simply describing proximate behaviours. Thus, Chapter 1 – Ecological and behavioural adaptations; Chapter 3 – Orientation; Chapter 4 – Feeding; Chapter 7 – Osmoregulation; and Chapter 8 – Physiological and biochemical basis of behaviour, were generally not synthetic, and read like catalogues of behaviour descriptors, often with little context on the natural history or biology of the responses. These chapters are not accessible to the non-specialist student, and their value lies primarily in their extensive literature searches. On the other hand, there are several wonderful pieces, including Chapter 5 – Reproductive behaviour and Chapter 6 – Ageing and development, whose compelling and clearly written stories cut across the artificial lines of plant, insect, animal, and parasite designations, to address the essence of our understanding of nematode behaviour. In this group, I particularly liked Chapter 2 – Locomotion, for the succinct incorporation of historical ideas into the growth of current thinking in this area. Chapter 9 – Molecular basis of behaviour, was an excellent presentation of behaviour in the C. elegans model system, and the authors did an outstanding job making the concepts and techniques in this high-tech area accessible to students of general biology. The remaining 4 chapters fell somewhere in the middle of the continuum. Overall, I think this a good effort, and I recommend this book for the shelves of every nematode biologist. It is valuable because of the sheer amount of information on nematode behaviour that it contains, and especially for the reference lists. For the 4 or 5 well-written chapters, this book is priceless!