Previous studies on infection of Trypanosoma cruzi in the Poço das Antas Biological Reserve population of wild free-ranging Leontopithecus rosalia have shown the presence of genotype T. cruzi II, associated in Brazil with human disease. Herein, this study has been extended, the infection being evaluated in L. rosalia of 3 different tamarin populations, inhabiting distinct forest areas located in the same Atlantic Coastal Rainforest. Edentata, Marsupialia, Rodentia and Chiroptera were examined exclusively in the Poço das Antas Biological Reserve. Excluding Chiroptera, T. cruzi infection was found in all orders. Biochemical and molecular characterization demonstrated that golden lion tamarins maintained stable infections by T. cruzi II. The isolates from the other mammals corresponded to T. cruzi I, suggesting independent transmission cycles occurring among the sylvatic mammals inside Poço das Antas Biological Reserve. Significant differences in the infection patterns presented by the 3 populations of wild and captive-born golden lion tamarins were noticed. In Poço das Antas a considerably higher number of positive haemocultures from tamarins with positive serological titres was observed in comparison to those obtained from other areas. The implications for conservation and public health of an active sylvatic cycle in the Atlantic Coastal Rainforest of Rio de Janeiro are discussed.

The fact that the Schistosoma mansoni egg has two ATP diphosphohydrolase (EC 3.6.1.5) isoforms with different net charges and an identical molecular weight of 63000, identified by non-denaturing polyacrylamide gel electrophoresis and immunological cross-reactivity with potato apyrase antibodies, is shown. In soluble egg antigen (SEA), only the isoform with the lower net negative charge was detected and seemed to be the predominant species in this preparation. By confocal fluorescence microscopy, using anti-potato apyrase antibodies, the S. mansoni egg ATP diphosphohydrolase was detected on the external surface of miracidium and in von Lichtenberg's envelope. Intense fluorescence was also seen in the outer side of the egg-shell, entrapped by the surface microspines, suggesting that a soluble isoform is secreted. ATP diphosphohydrolase antigenicity was tested using the vegetable protein as antigen. The purified potato apyrase was recognized in Western blots by antibodies present in sera from experimentally S. mansoni-infected mice. In addition, high levels of IgG anti-ATP diphosphohydrolase antibodies were detected by ELISA in the same sera. This work represents the first demonstration of antigenic properties of S. mansoni ATP diphosphohydrolase and immunological cross-reactivity between potato apyrase and sera from infected individuals.

Tick toxicoses, of which paralysis is the most widespread and dominant form, are important elements of pathogenesis induced by ticks. Tick paralysis is the most widespread and dominant form of tick toxicoses. Non-paralytic forms of tick toxicoses do occur and evidence suggests that these forms of toxicoses are not evolutionary related. While functional significance has been suggested for tick toxins, the advantages for tick survival in general are not clear. This review considers the molecular nature of tick toxins, the possibility that tick toxins have originated more than once independently and whether these toxins could have unrecognized benign functions.

To adapt to different environmental conditions between poikilothermic and homeothermic hosts, the plerocercoid of Spirometra erinacei (sparganum) might express a variety of biologically active molecules. We have identified a 78 kDa glucose-regulated protein of the sparganum (SpGrp78) by differential display of mRNA, employing RNAs each from sparganum adjusted at 9 °C and 37 °C. A full-length cDNA of 2148 bp encodes for a protein of 651 amino acids with a predicted molecular mass of 71 610 Da and shares molecular characteristics with heat-shock protein 70, including a putative ATP binding site, signal peptide cleavage site and endoplasmic reticulum retention signal. Phylogenetic analysis revealed that SpGrp78 was mostly related to those of Echinococcus multilocularis and E. granulosus. Expression of SpGrp78 mRNA increased approximately 7-fold by inhibition of glycosylation by tunicamycin, 2-fold by temperature-shift from 9 °C to 37 °C and slightly by pH-shift to 4·0 or 5·5. These results suggested that induction of SpGrp78 mRNA is related to the functional role of SpGrp78 as a molecular chaperone when the parasite adapts to a new host environment.

Infection by Opisthorchis viverrini is a strong risk factor for cholangiocarcinoma. However, the mechanism by which the parasite is involved in carcinogenesis is not clear. In addition to the direct damage of the bile duct epithelium via direct contact with O. viverrini, the excretory/secretory (ES) product(s) released from the parasites may play important roles in this process. We therefore investigated the responses of a fibroblast cell line, NIH-3T3, to ES product(s) released from O. viverrini by using a non-contact co-culture technique. In this culture system, the parasites in the upper chamber had no direct contact with the NIH-3T3 cells in the lower chamber of the culture plate. The results indicated a marked increase in NIH-3T3 cell proliferation in the non-contact co-culture condition with either 0% or 10% calf serum in the medium compared with that without parasites. ES product(s) increased cell proliferation by stimulating the expression of phosphorylated retinoblastoma (pRB) and cyclin D1, the key proteins in driving cells through the G1/S transition point of the cell cycle. This led to the induction of cells going into the S-phase of the cell cycle. ES product(s) also changed the morphology of NIH-3T3 cells to a refractive and narrow shape, which allowed the cells to proliferate in the limited culture area. For the first time, we have been able to demonstrate increased cell proliferation induced by the ES product(s) from O. viverrini; this finding may clarify how O. viverrini ES product(s) affect human bile duct epithelium during cholangiocarcinogenesis.

Stage-specific alternative splicing of the heat-shock transcription factor of Schistosoma mansoni (SmHSF) generates isoforms with structural diversity that may modulate the activity of SmHSF at different life-stages, and thus may regulate the expression of different genes at different developmental stages. RT-PCR, cloning and DNA-sequence analyses showed stage-specific alternative splicing inside the DNA-binding domain (DBD) involving introns I1 and I2, and beyond the DBD involving introns I4a and I7. Retention of introns I2 and I4a would inactivate SmHSF since they contain termination codons. Retention of intron I1 would add 11 amino acids inside the DBD and may change the DNA-binding specificity of SmHSF; intron I7 would add 13 amino acids to the effector region of HSF. Retention of introns was more pronounced in cercariae (larval stage living in water) than in adult worms (parasitic form in mammals). The isoforms were expressed in bacteria, but functional evaluation was not feasible, because only the isoform lacking introns was soluble while isoforms with introns were insoluble. However, stage-specific alternative splicing that changed HSF function in vivo was evidenced in intact cercariae. The cercarial SmHSF mRNA was enriched with introns I2 and I4a that contain termination codons. Therefore, translation of the SmHSF mRNA was impaired, and the SmHSF protein was undetectable. Consequently, the HSP70 gene could not be transcribed, and the HSP70 mRNA was missing. Alternative splicing was observed for short DNA segments (33–45 bp) bound by splice signals, located in the coding region. These are not bona fida exons since they are not flanked by introns. Yet, they are not regular introns since they are often found in mature mRNA. Alternative splicing of these DNA segments caused structural diversity that could modulate the function of the gene product.

Knowledge about how parasites choose their hosts is scarce and incomplete. Recent work has primarily focused on host health (i.e. immunocompetence) whereas ecological factors have been largely neglected. Here we investigate whether the immunocompetence, the nutritional condition or body size of nestling European bee-eaters Merops apiaster are used as parameters for habitat choice of the haematophagous fly Carnus hemapterus. We found that (i) flies consistently and non-randomly preferred larger nestlings, even after controlling for differences in habitat availability (host surface), (ii) in the presence of similar-sized hosts, parasites' choice for an individual was less likely than if hosts differed in size, (iii) the more the hosts differed in size, the more the parasites aggregated on the larger nestling and (iv) parasites changed their preference according to size criteria regardless of the identity of the larger host. Neither immunocompetence nor host body condition could account for parasites' preference. Our results do not support the prediction of the Tasty Chick Hypothesis, namely that the poor immunocompetence ability of junior chicks makes them more attractive to parasites. We conclude that basic ecological factors (e.g. body size) can be essential for parasites when choosing a host.

RJLs represent a recently described family of the Ras-related GTP-binding proteins. The Trypanosoma cruzi orthologue, TcRjl, was isolated and its locus was characterized in a region of almost 5 kb. Its 660 bp orf, predicting a protein of 24·13 kDa, is present as a single copy gene in T. cruzi I lineage, and from 1–2 copies in T. cruzi II lineage. TcRjl shares 73% aa sequence similarity with its closest identified orthologue, T. brucei TbRjl. RT–PCR experiments revealed that TcRjl is transcribed in mRNA in the 3 main life forms of the parasite, while Northern hybridization demonstrated that TcRjl is transcribed in T. cruzi epimastigotes as at least 2 transcripts, one of around 950 nt and the other of 1500 nt. Splice-leader addition was mapped to a single site at −69 bp upstream of TcRjl orf indicating that the two mRNA types may derive in differences at the 3′ of TcRjl mRNA. TcRjl locus presents considerable synteny with Rjl loci from Trypanosoma brucei and Leishmania major as available from their respective genome projects.

Allozyme variation within and among populations of 3 species of the genus Lecithochirium (Trematoda: Hemiuridae) was studied by starch gel electrophoresis. In total, 19 loci were analysed in 7 populations. The level of genetic variability was relatively high in all populations. The percentage of polymorphic loci (0·95 criterion) observed per population varied from 21·0% to 55·5%, and expected heterozygosity levels varied from 0·082 to 0·197. All populations showed significant heterozygote deficiencies. In Lecithochirium fusiforme most of the deviations from Hardy–Weinberg proportions were within the populations and this species showed moderate population structuring (FIS=0·486, FST=0·142, Nm=1·51) and accordingly low intraspecific genetic distances (D=0·003 to 0·027). A significant lack of heterozygotes for several polymorphic loci was revealed in Lecithochirium rufoviride and Lecithochirium musculus. The most probable cause of the population genetic subdivision in L. rufoviride is the presence of at least 1 cryptic species in the populations studied. Although the lowest percentage of fixed genetic differences was that between L. fusiforme and L. musculus, two different algorithms for the construction of evolutionary trees on a matrix of genetic distances confirmed that L. fusiforme and L. rufoviride are phenetically the most closely related species.

A nested (non-random) species composition was observed among the intestinal macroparasite communities of European eels, Anguilla anguilla. Nestedness was observed in 8 out of 10 component community samples from the rivers Thames and Test between April 2000 and October 2001. Parasite component communities consisted of mainly generalist and specialist, but also accidental species, and included acanthocephalans, cestodes, nematodes and digeneans. Nestedness was observed when component population size differed markedly between all or most parasite species, but not when the majority of species present was similarly abundant. Nestedness could not be explained in terms of host weight, log normal distribution of parasite species, or mean intensity of infection. It is proposed that nestedness occurred as a result of a sufficiently graded abundance between parasite species, which was established early in the year by colonization processes.

Fasciola hepatica secretes proteolytic enzymes and other molecules that are essential for host penetration and migration. This mixture may include enzymes required for the degradation of supramucosal gels, which defend epithelial surfaces against pathogen entry. These contain hydrated mucins that are heavily glycosylated. Excretory-secretory products (ES) from F. hepatica were examined for a range of glycosidase activities, using synthetic 4-methylumbelliferyl glycosides as substrates. The ES product contained at least 8 different glycosidase activities, the most abundant of which were β-N-acetylhexosaminidase, β-galactosidase and β-glucosidase. Alpha-fucosidase, β-glucuronidase, α-galactosidase, α-mannosidase and neuraminidase were also present. β-N-acetylhexosaminidase and β-galactosidase were present in multiple isoforms (at least 4), whereas β-glucosidase appeared to exist as one isoenzyme with a pI <3·8. All three enzymes had acidic pH optima (4·5–5·0). Ovine small intestinal mucin was degraded by ES at pH 4·5 or 7·0, with or without active cathepsin L, the major protease found in F. hepatica ES. The ability of F. hepatica ES to degrade mucin in the presence or absence of active cathepsin L suggests that cathepsin L is not essential for mucin degradation. The abundance of β-galactosidase and β-hexosaminidase in ES supports a role for these enzymes in mucin degradation.

Considering that both infection and dominance status can be conveyed through urinary odours and both are thought to affect mate choice, the present study assessed the role of infection and male dominance status on female mate choice in arena enclosures. Three male CD-1 mice were simultaneously introduced into each of 4 spatially complex arenas (3·0×0·6×0·4 m high) for 24 h prior to introduction of 5 females into each arena. During the first mating sequence (i.e. Mating 1), all 3 males were uninfected. Prior to Mating 2, the dominant male in each arena was infected with 200 L3 of Heligmosomoides polygyrus (Nematoda). Prior to Mating 3, the dominant male was drug-treated to remove the parasite. Dominance was assessed by the absence of rump or tail wounds (Freeland, 1981). Females were removed from the arena when visibly pregnant, and returned for subsequent mating 2 weeks following parturition. Paternity was determined by microsatellite analysis of each pup. Multi-male mating (i.e. mating with 2 or all 3 males) was a common strategy among females as littermates were sired by 2 or all 3 males in 64% of the litters. Contrary to expectation, the dominant male did not sire the majority of offspring in any of the mating sequences, and infection and subsequent drug treatment of the dominant male did not have a significant impact on female mate choice. In addition to methodological differences in paternity determination (i.e. DNA analysis versus behavioural observations and/or phenotypic traits), these findings may be further explained by the spatial complexity of the experimental arenas.

The acanthocephalan parasite Acanthocephalus dirus induces a colour change in the intermediate host, the aquatic isopod Caecidotea intermedius, which increases transmission to definitive hosts (creek chub, sunfish). We examined the potential for conflict to occur between infective (cystacanth) and non-infective (acanthor, acanthella) stages of A. dirus over the level of colour modification that should be induced when these stages share a host. Using a field survey, we showed that host sharing by infective and non-infective stages was relatively common and that infective and non-infective stages differed in their effects on colour modification. Non-infective stages induced a colour change over 40% of the body, whereas infective stages induced a colour change over 80%. Thus, conflict could occur between stages over the level of modification that should be induced. We then showed that mixed-stage infections induced a colour change in the host that was consistent with the level of modification induced by the infective stage. We discuss the potential significance of these results to patterns of host modification and their effects on stage-related survival in nature.

Most studies on the effects of tanniferous plants on nematodes have examined forages but have neglected the woody plants. Therefore, in vitro effects of extracts from 3 woody plants (Rubus fructicosus, Quercus robur, Corylus avellana) have been tested on trichostrongyles and compared to sainfoin, a legume forage. Because some in vivo results indicated that the effects of tannins differed depending on the parasitic species and/or stages, the effects were measured on 3rd-stage larvae (L3) and adult worms of Teladorsagia circumcincta, Haemonchus contortus and Trichostrongylus colubriformis. The effects of plant extracts varied according to the plant sources, the parasite species and stages. For the woody plants, significant inhibitory effects were obtained on both stages of abomasal species. Results for T. colubriformis were more variable. Effects of sainfoin extracts were significant on T. colubriformis and H. contortus L3, and on abomasal adult worms. In order to assess the implications of tannins, polyethylene glycol (PEG), an inhibitor of tannins, was added to hazel tree, oak and sainfoin extracts. Without PEG, significant inhibitory effects on L3 and adult worms were confirmed. After addition of PEG, the larval migration and motility of adult worms were restored in most cases. These results confirm variations in effects depending on factors related to plants or parasites and suggest that tannins are partly responsible for the effects.

Few papers have been published on tick lectins so far, and therefore more data are needed to complete the mosaic of knowledge of their structural and functional properties. Tissue-specific lectin/haemagglutinin activities of both soft and hard ticks have been investigated. Some tick lectins are proteins with binding affinity for sialic acid, various derivatives of hexosamines and different glycoconjugates. Most tick lectin/haemagglutinin activities are blood meal enhanced, and could serve as molecular factors of self/non-self recognition in defence reactions against bacteria or fungi, as well as in pathogen/parasite transmission. Dorin M, the plasma lectin of Ornithodoros moubata, is the first tick lectin purified so far from tick haemolymph, and the first that has been fully characterized. Partial characterization of other tick lectins/haemagglutinins has been performed mainly with respect to their carbohydrate binding specificities and immunochemical features.

Pre-natal infection of Schistosoma japonicum in pigs may prove to be a useful model in shedding light on human pre-natal schistosomiasis. This study describes the effects of immune colostrum on worm burdens, tissue egg counts, liver pathology and crude worm or egg antigen-specific IgG and IgA responses, in groups of pigs pre-natally, pre-natally+post-natally or post-natally exposed to S. japonicum. Results suggest that pre-natal exposure and immune colostrum did not affect the establishment of a post-natal challenge infection. However, immune colostrum seemed to increase the levels of septal fibrosis in pre-natally exposed pigs. These findings indicate that further investigations will prove valuable, elucidating the influence of the parasitological and immunological status of the sow, on pre-natally exposed pigs, and on the ability of these pigs to develop resistance against S. japonicum later in life.

The role of acquired immunity in lymphatic filariasis is uncertain. Assuming that immunity against new infections develops gradually with accumulated experience of infection, models predict a decline in prevalence after teenage or early adulthood. A strong indication for acquired immunity was found in longitudinal data from Pondicherry, India, where Mf prevalence was highest around the age of 20 and declined thereafter. We reviewed published studies from India and Subsaharan Africa to investigate whether their age-prevalence patterns support the models with acquired immunity. By comparing prevalence levels in 2 adult age groups we tested whether prevalence declined at older age. For India, comparison of age groups 20–39 and 40+ revealed a significant decline in only 6 out of 53 sites, whereas a significant increase occurred more often (10 sites). Comparison of older age groups provided no indication that a decline would start at a later age. Results from Africa were even more striking, with many more significant increases than declines, irrespective of the age groups compared. The occurrence of a decline was not related to the overall Mf prevalence and seems to be a chance finding. We conclude that there is no evidence of a general age-prevalence pattern that would correspond to the acquired immunity models. The Pondicherry study is an exceptional situation that may have guided us in the wrong direction.

Ecdysteroids (moulting hormones), juvenoids and neuropeptides in ticks are reviewed but, by far, the emphasis is on the former since this class of hormones has been the subject of most investigations. In immature stages of ticks, ecdysteroids have been shown to regulate moulting and to terminate larval diapause. Although there is a paucity of information on the molecular action of ecdysteroids in ticks, their action appears to be via a heterodimeric ecdysone/ultraspiracle receptor, as in insects. The role of ecdysteroids in sperm maturation in adult males is considered. In females, ecdysteroids function in the regulation of salivary glands, of production of sex pheromones and of oogenesis and oviposition. There is evidence for ecdysteroid production in the integument and pathways of hormone inactivation are similar to those in insects. Ecdysteroids also function in embryogenesis. Although evidence for the occurrence and functioning of juvenile hormones in ticks has been contradictory, in recent thorough work it has not been possible to detect known juvenile hormones in ticks, nor to demonstrate effects of extracts on insects. Factors (neuropeptides) from the synganglion affect physiological processes and limited immunocytochemical studies are reviewed. Sigificantly, a G-protein-coupled receptor has been cloned, expressed, and specifically responds to myokinins.

Here, the validity of the assumption of concerted evolution of ribosomal regions in larval and adult Cooperia oncophora was assessed. In each of 4 individuals of this parasitic nematode, at least 78% of the sequences comprised different ITS variantsNucleotide sequence data are available in the DDBJ/EMBL/GenBank databases under the Accession numbers AJ544390–AJ544465.. This implies that concerted evolution is not acting, which is corroborated by the scarcity of signatures of gene conversion and recombination. Mis-incorporation of nucleotides and illegitimate PCR-induced recombination turned out to be unlikely, and positions with substantial frequencies of alternative nucleotides corresponded to ambiguous positions in published ITS2 sequences of this and other Cooperia species based on direct sequencing. The ITS regions of each individual C. oncophora displayed a significant excess of unique mutations in agreement with expansion of the ribosomal gene family. Interesting corollaries of the inferred size changes of this gene family are genomic rearrangements that occur during larval development such as multiple rounds of endoduplication (in Rhabditidae), chromatin diminution (in Ascaris), and non-compensatory mutations on the secondary structure of the ITS2. It is yet unknown which process is important in trichostrongylids. Finally, although it can not be rigorously assessed in Cooperia, the ITS polymorphisms can readily be envisioned to affect phylogenetic reconstructions of closely related nematodes.

We examined the parasite-induced cataract formation in rainbow trout (Oncorhynchus mykiss) using slit-lamp microscopy to determine the relationship between cataract intensity and number of Diplostomum spathaceum parasites that were established in the lens. Cataract intensity increased significantly with parasite burden, but was also affected by the pattern of exposure to the parasite cercariae. The slit-lamp methodology proved useful in scoring the cataracts since it provides a 3-dimensional view into the lens and gives an actual picture of the location and intensity of the cataracts, which allows detailed investigations of mechanisms underlying cataract formation in various fish species. Potential applications of the method in fish farming and parasitological studies are discussed.