Precocious egg production, i.e. progenesis, has been documented for a number of species in scattered reports throughout the trematode literature. The last 2 extensive studies on the subject date from Buttner in the early 1950s (in French) and from Tang in the early 1980s (in Chinese). Overall, 43 species were then known for their ability to produce eggs at the metacercarial stage while still in the second intermediate host. Here, we update the list, and document the existence of progenesis in a total of 79 digenean trematode species, for which we provide information on the taxonomy of the hosts, the facultative or obligate character of progenesis, relevant references, as well as some other pertinent biological information. We then review the subject by asking 7 questions of fundamental evolutionary importance. These include: What favours progenetic development? What are the associated costs and benefits? How are progenetic eggs released from the host? While exposing the various opinions of previous authors, we attempt to give a synthetic overview and stress on the importance of the metacercarial cyst wall (whether it is present, and if so its thickness) in the evolution and the adoption of a progenetic life-cycle.

Mycoplasmas are common contaminants of eukaryotic cells grown in tissue culture. A commercially available Mycoplasma Removal Agent (MRA) was therefore assessed for its effect on tachyzoites of Neospora caninum, in order to determine its suitability for further use in parasite cell cultures. Analyses of tachyzoite and excreted-secreted proteins and antigens by SDS-PAGE and Western blotting show that MRA treatment results in the rapid selection of a mutant population that differs from the control and parental lines in its protein and antigen content. The treatment of N. caninum cultures with MRA is therefore not recommended for the eradication of Mycoplasma.

Leishmania infantum has been described as a highly polymorphic group of parasites, responsible for visceral leishmaniasis and cutaneous leishmaniasis. In this paper we report the life-cycle of L. (L.) infantum in an endemic area of visceral leishmaniasis in Venezuela, by using molecular diagnosis and characterization of parasites isolated from dogs, humans with visceral leishmaniasis and sand flies. The molecular characterization was carried out by use of kDNA restriction analysis, dot-blot hybridization with species-specific probes and RFLP of the PCR products. The results demonstrated that L. (L.) infantum is the parasite responsible for VL in the island. The parasites were revealed to be genetically homogeneous with no intra-specific differences between isolates from different individuals. The highest homology of the isolates was with L. (L.) infantum from the Old World rather than with L. (L.) chagasi from the New World. Additionally, we report the geographical distribution of Lutzomyia longipalpis, and the relationship with the transmission of L. (L.) infantum in the studied area.

Between 20% and 60% of the population of most countries are infected with the protozoan Toxoplasma gondii. Subjects with clinically asymptomatic life-long latent toxoplasmosis differ from those who are Toxoplasma free in several behavioural parameters. Case-control studies cannot decide whether these differences already existed before infection or whether they were induced by the presence of Toxoplasma in the brain of infected hosts. Here we searched for such morphological differences between Toxoplasma-infected and Toxoplasma-free subjects that could be induced by the parasite (body weight, body height, body mass index, waist-hip ratio), or could rather correlate with their natural resistance to parasitic infection (fluctuating asymmetry, 2D[ratio ]4D ratio). We found Toxoplasma-infected men to be taller and Toxoplasma-infected men and women to have lower 2D[ratio ]4D ratios previously reported to be associated with higher pre-natal testosterone levels. The 2D[ratio ]4D ratio negatively correlated with the level of specific anti-Toxoplasma antibodies in Toxoplasma-free subjects. These results suggest that some of the observed differences between infected and non-infected subjects may have existed before infection and could be caused by the lower natural resistance to Toxoplasma infection in subjects with higher pre-natal testosterone levels.

Lymphocytes infected with the protozoan parasite Theileria parva are transformed to permanently proliferating cells, an event underlying the pathology of the disease. However, the molecular signalling mediating this process is complex and poorly understood. Here, we show that down-regulation of JNK signalling by transient over expression of a dominant-negative mutant of JNK (JNK-APF) significantly increases Annexin-V-phycoerythrin (V-PE) labelling on infected B cell populations observed using flow cytometry. To establish whether this increase was specifically due to apoptosis, we used a novel single-cell imaging method: micro-rotation (MR)-imaging, designed to allow high-resolution 3-dimensional imaging of single cells in suspension. With this method we visualized subcellular patterns of V-PE uptake and chromatin organization in lymphocytes co-transfected with JNK-APF and GFP-tagged histone-H2B. This single-cell approach allowed us to clearly reveal characteristic apoptotic phenotypes, whose patterns reflected progressive states of programmed cell death due to JNK down-regulation. Our results strongly suggest a role for JNK in the survival of Theileria-infected B cells, and demonstrate the powerful utility of a new and unique 3-dimensional imaging method for living cells in suspension.

Host nutrition plays an important role in determining the development and success of parasitic infections. While studies of vertebrate hosts are accumulating, little is known about how host nutrition affects parasites of invertebrate hosts. Crithidia bombi is a gut trypanosome parasite of the bumble bee, Bombus terrestris and here we use it as a model system to determine the impact of host nutrition on the population dynamics and development of micro-parasites in invertebrates. Pollen-starved bees supported significantly smaller populations of the parasite. In pollen-fed bees the parasite showed a temporal pattern in development, with promastigote transmission stages appearing at the start of the infection and gradually being replaced by choanomastigote and amastigote forms. In pollen-starved bees this developmental process was disrupted, and there was no pattern in the appearance of these three forms. We discuss the implications of these results for parasite transmission, and speculate about the mechanisms behind these changes.

Trypanosomatids are early divergent parasites which include several species of medical interest. Trypanosoma rangeli is not pathogenic for humans but shows a high immunological cross-reactivity with Trypanosoma cruzi, the causative agent of Chagas' disease that affects more than 17 million people throughout the world. Recent studies have suggested that T. cruzi KMP-11 antigen could be a good candidate for the induction of immunoprotective cytotoxic responses against T. cruzi natural infection. In the present paper the genes coding for the T. rangeli kinetoplastid membrane protein-11 have been characterized. The results show that the locus encoding this protein is formed by 4 gene units measuring 550 nucleotides in length, organized in tandem, and located in different chromosomes in KP1(+) and KP1(−) strains. The gene units are transcribed as a single mRNA of 530 nucleotides in length. Alignment of the T. rangeli KMP-11 deduced amino acid sequence with the homologous KMP-11 protein from T. cruzi revealed an identity of 97%. Interestingly, the T and B cell epitopes of the T. cruzi KMP-11 protein are conserved in the T. rangeli KMP-11 amino acid sequence.

Cyphocarax gilbert (Szidat, L., 1948) is a fish commonly found in coastal drainage of eastern Brazil. This fish is sometimes caught with signs of infection by the crustacean Riggia paranensis, a haematophagous parasite. A remarkable feature of infected fish is that they lack gonads. In this paper we have analysed the frequency of parasitism, the gonadal development of non-infected fish and the profile of plasma proteins in both infected and non-infected specimens. Two reproductive periods/year were observed, beginning in February and August. On average, 40% of fish were infected, in the Itabapoana River (Brazil). Sex-specific proteins were identified by electrophoresis. SDS-PAGE analysis demonstrated that a 143 kDa female-specific glycolipoprotein (FSP) is a calcium-binding phosphoprotein. FSP was isolated through ultracentrifugation and SDS-PAGE analysis showed that the native protein is composed of three polypeptides of 143, 100 and 70 kDa. Both FSP and a 33 kDa male-specific protein (MSP) are absent from infected fish plasma. FSP levels in female plasma changes with the developmental stage of gonads. Altogether these data suggest that the FSP corresponds to fish vitellogenin. Furthermore, the absence of the above-mentioned proteins in infected fish suggests that R. paranensis might interfere with the regular hormonal process of fish vitellogenesis.

The potential of biological invasions to threaten native ecosystems is well recognized. Here we describe how an introduced species impacts on native host-parasite dynamics by acting as an alternative host. By sampling sites across an invasion front in Ireland, we quantified the influence of the introduced bank vole (Clethrionomys glareolus) on the epidemiology of infections caused by flea-transmitted haemoparasites of the genus Bartonella in native wood mice (Apodemus sylvaticus). Bartonella infections were detected on either side of the front but occurred exclusively in wood mice, despite being highly prevalent in both rodent species elsewhere in Europe. Bank vole introduction has, however, affected the wood mouse-Bartonella interaction, with the infection prevalence of both Bartonella birtlesii and Bartonella taylorii declining significantly with increasing bank vole density. Whilst flea prevalence in wood mice increases with wood mouse density in areas without bank voles, no such relationship is detected in invaded areas. The results are consistent with the dilution effect hypothesis. This predicts that for vector-transmitted parasites, the presence of less competent host species may reduce infection prevalence in the principal host. In addition we found a negative relationship between B. birtlesii and B. taylorii prevalences, indicating that these two microparasites may compete within hosts.

Sequences of the first internal transcribed spacer (ITS-1) and the D1-D3 domains of the large subunit (LSU) of the ribosomal DNA (rDNA) were determined for multiple specimens of 4 operational taxonomic units (OTUs) of the monogenean, Pseudorhabdosynochus lantauensis. OTUs were defined based on their collecting localities, host and/or morphological characteristics. All P. lantauensis specimens of one group (OTUs 1 and 3) differed in their sequences of the ITS-1 and partial LSU rDNA when compared with specimens of a second group (OTUs 2 and 4) by 12% and 2%, respectively. Results of the phylogenetic analyses of the LSU rDNA sequence data showed total (100%) bootstrap support for the separation of P. lantauensis into 2 distinct clades. At least 11 of the 18 nucleotide differences in the LSU sequence between the two P. lantauensis clades were derived (i.e. autapomorphic) characters when the morphologically distinct species, P. epinepheli and P. coioidesis, were used as outgroups. Furthermore, there were several autapomorphic character states for each P. lantauensis clade. This provides sufficient evidence to reject the null hypothesis that P. lantauensis represents a single species. Morphological and morphometric differences between these two clades provided additional strong support for the separation of P. lantauensis into two species. These two parasite species were found to co-exist on one of the two species of serranid fish (i.e. Epinephelus coioides) examined in the South China Sea (Guangdong Province, China).

European eels Anguilla anguilla from the rivers Thames and Test, in the south of England, were examined between 2000 and 2003 for infection with the swim-bladder nematode Anguillicola crassus. Since its introduction to Thames eels at tidal estuarine locations circa 1987, A. crassus has become established in non-tidal freshwater stretches upriver and data from these locations are reported for the first time. The prevalence of infection at Thames estuary locations was higher during 2000–2003 than for the period 1987–1992. By 2003, similar prevalences were observed at freshwater and estuarine locations, but infection intensities were significantly higher in freshwater. Eels from the river Test appear to have been recently colonized by A. crassus (circa 2000). Parasite population establishment within these eels was uncharacteristically slow during 2000–2001, with low prevalence and intensity of infection, and few gravid females during this period. By 2003, infection levels in Test eels were similar to those in Thames eels. The expansion of the A. crassus population in Test eels has occurred in the absence of the paratenic host ruffe Gymnocephalus cernuus, and at suboptimal pH for the survival and infectivity of free-living larvae. The epidemiology of A. crassus in Test eels demonstrates that transmission of A. crassus by ruffe is not required for high prevalence and intensity of infection in eels. However, the consistently low and atypical levels of infection in Test eels during 2000 and 2001 suggests that paratenic transmission by ruffe may provide a substantial contribution to the dynamics of A. crassus in eels in the early years following introduction, by facilitating the rapid increase in prevalence and intensity of A. crassus infection that typically occurs during this time.

A copper/zinc superoxide dismutase (Cu/ZnSOD) gene and a manganese superoxide dismutase (MnSOD) gene of the human parasite Clonorchis sinensis have been cloned and their gene products functionally characterized. Genes Cu/ZnSOD and MnSOD encode proteins of 16 kDa and 25·4 kDa, respectively. The deduced amino acid sequences of the two genes contained highly conserved residues required for activity and secondary structure formation of Cu/ZnSOD and MnSOD, respectively, and show up to 73·7% and 75·4% identities with their counterparts in other animals. The genomic DNA sequence analysis of Cu/ZnSOD gene revealed this as an intronless gene. Inhibitor studies with purified recombinant Cu/ZnSOD and MnSOD, both of which were functionally expressed in Escherichia coli, confirmed that they are copper/zinc and manganese-containing SOD, respectively. Immunoblots showed that both C. sinensis Cu/ZnSOD and MnSOD should be antigenic for humans, and both, especially the C. sinensis MnSOD, exhibit extensive cross-reactions with sera of patients infected by other trematodes or cestodes. RT-PCR and SOD activity staining of parasite lysates indicate that there are no significant differences in mRNA level or SOD activity for both species of SOD, indicating cytosolic Cu/ZnSOD and MnSOD might play a comparatively important role in the C. sinensis antioxidant system.

Parasitism often influences the phenotype of individuals. Many of the resulting changes are due to changes in resource allocation that come with infection. Here we examine the effect of a trematode parasite on the shape and defence morphology of a New Zealand freshwater snail, Potamopyrgus antipodarum. The trematode Microphallus sp. asexually produces hundreds of metacercarial cysts in the snail. The length, width and 2-dimensional area of each snail were measured. Snails were also assessed for their degree of spininess. Snails were dissected to determine gender, brooding condition and parasitism. Snails infected with Microphallus sp. were found to be significantly less spiny than uninfected snails. Microphallus-infected snails were also found to have a significantly greater width to length ratio at larger sizes than their uninfected counterparts. These trends could be explained in at least 3 ways. (1) Infection causes the snails to not produce spines and to become wider. (2) Spiny and narrower snails are more likely to die when they become infected. (3) Spiny and narrower snails are more resistant to infection. The changes in phenotype observed are unlikely to be adaptive for either the host or parasite and probably represent physiological by-products of the host-parasite relationship.

Different animal species have different probabilities of being discovered and described by scientists, and these probabilities are determined to a large extent by the biological characteristics of these species. For instance, species with broader geographical ranges are more likely to be encountered by collectors than species with restricted distributions; indeed, the size of the geographical range is often the best predictor of a species' date of description. For parasitic organisms, host specificity may be similarly linked to the probability of a species being found. Here, using data on 170 helminth species parasitic in freshwater fishes, we show that host specificity is associated with the year in which the helminths were described. Helminths that exploit more host species, and to a lesser degree those that exploit a broader taxonomic range of host species, tend to be discovered earlier than the more host-specific helminths. This pattern was observed across all helminth species, as well as within the different helminth taxa (trematodes, cestodes, nematodes and acanthocephalans). Our results demonstrate that the parasite species known at any given point in time are not a random subset of existing species, but rather a biased subset with respect to the parasites' biological properties.

The complete Taenia asiatica mitochondrial genome was amplified by long extension polymerase chain reaction (long PCR) to yield overlapping fragments that were then completely sequenced. The whole mitochondrial genome was 13703 bp long and contained 12 protein-encoding, 2 ribosomal RNA (small and large subunits), 22 transfer RNA genes and a short non-coding region. Thus, its gene contents are like those typically found in metazoan animal mitochondrial genomes (apart from the absence of atp8). All the genes were transcribed from the same strand. The 3′ end 34 bp region of nad4L overlapped with the 5′ end portion of nad4. The tRNA genes were 61–69 bp long, and the secondary structures of 18 tRNAs had typical clover-leaf shapes with paired DHU arms. However, trnC, trnS1, trnS2 and trnR had unpaired DHU arms that were 7–12 bp in length. The tRNAs that transferred serine lacked a DHU arm, as is also observed in a number of parasitic platyhelminths and metazoans. However, the trematode trnRs have paired DHU arms. The T. asiatica mtDNA non-coding region was like that in other cestodes since it was composed of a short non-coding region of 72 nucleotides and a long non-coding region of 176 nucleotides separated by a trnL1/, trnS2/, trnL2/, trnR/, nad5 gene cluster. The sequences of the cox1 genes between T. asiatica and T. saginata differ by 4·6%, while the T. asiatica cob gene differs by 4·1% and 12·9% from the cob genes of T. saginata and T. solium, respectively. In conclusion, the T. asiatica mitocondrial genome should provide a resource for comparative mitochondrial genomics and systematic studies of parasitic cestodes.