Human fascioliasis is a worldwide, pathogenic food-borne trematodiasis. Impressive clinical pictures comprising puzzling polymorphisms, manifestation multifocality, disease evolution changes, sequelae and mortality, have been reported in patients presenting with neurological, meningeal, neuropsychic and ocular disorders caused at distance by flukes infecting the liver. Proteomic and mass spectrometry analyses of the Fasciola hepatica excretome/secretome identified numerous, several new, plasminogen-binding proteins enhancing plasmin generation. This may underlie blood-brain barrier leakage whether by many simultaneously migrating, small-sized juvenile flukes in the acute phase, or by breakage of encapsulating formations triggered by single worm tracks in the chronic phase. Blood-brain barrier leakages may subsequently occur due to a fibrinolytic system-dependent mechanism involving plasmin-dependent generation of the proinflammatory peptide bradykinin and activation of bradykinin B2 receptors, after different plasminogen-binding protein agglomeration waves. Interactions between diverse parasitic situations and non-imbalancing fibrinolysis system alterations are for the first time proposed that explain the complexity, heterogeneity and timely variations of neurological disorders. Additionally, inflammation and dilation of blood vessels may be due to contact system–dependent generation bradykinin. This baseline allows for search of indicators to detect neurological risk in fascioliasis patients and experimental work on antifibrinolytic treatments or B2 receptor antagonists for preventing blood-brain barrier leakage.

Strongyloides stercoralis is a parasite that can cause death in immunocompromised people. A proper diagnosis is hence essential. The real-time polymerase-chain reaction (RT–PCR) is a novel, promising diagnostic method, that detects the DNA of the parasite in stool samples. In this retrospective study, we compared the sensitivity of agar plate coproculture (APC), an in-house immunofluorescence test (IFAT) and an in-house RT–PCR for the diagnosis of S. stercoralis infection. The study sample was composed by 223 samples. Samples resulting positive to APC, IFAT and RT–PCR were 20, 140 and 25, respectively. When sensitivity was calculated against a composite reference standard, serology confirmed the best performance (sensitivity 95%), followed by RT–PCR (57%) and APC (45%). In conclusion, in a non-endemic setting, serology is the best screening method, while the combination of APC and RT–PCR does not seem a reasonable approach to increase sensitivity. Both methods can have a role as confirmatory tests for selected cases.

The microscopical examination of Giemsa-stained thin blood smears and a nested PCR were performed to detect avian Plasmodium in 275 passerine birds from small and large fragments of Atlantic Forest, Minas Gerais, Brazil. The 275 blood smears were used both for the microscopical examination and nested PCR providing the DNA template used for the reactions. The sensitivity of the nested PCR assay was higher than that observed for blood smears through microscopical examination. High prevalence (39·6%) of Plasmodium infections was detected by nested PCR while the microscopical examination detected only 16·5% positive birds. Poor agreement was observed between the results of the two different tests. The PCR data obtained were correlated to the forest fragment size of the Atlantic Forest and also correlated to the biological characteristics of the birds (nest type construction, diet, participation in mixed-species flocks, age and sex). Birds captured in the large forest areas were more infected than birds captured in the small areas (51·9% and 28·5%, respectively). Diet and participation in mixed-species flocks were correlated to the Plasmodium parasitism. The insectivorous birds and those that participated in mixed-species flocks were more frequently infected (47% and 41·5%, respectively) than the other groups.

Infectious agents have considerable potential to regulate or constrain the population growth of vertebrate hosts in natural habitats. A broad theoretical framework provides many insights into how the biology of the parasite and the demography of the host interact to determine this impact. It may manifest itself as a steady influence over time via stable endemic infection or in a recurrent epidemic fashion, sometimes with unpredictable intervals between epidemics depending on the generation time of the pathogen (time from infection to recovery or host death), its ability to induce lasting immunity and the population growth rate of the host species. Building on these notions, the paper focuses on recent work on the population dynamics of genetically variable pathogen populations and examines the factors that determine the evolution of virulence and the maintenance of genetic diversity in both host and pathogen. Recent research extends conventional theoretical templates to include population genetic elements and the within-host dynamics of the parasite and its interaction with the vertebrate immune system.

Little is known of the prevalence and life-cycle of trypanosomes in mammals native to Australia. Native Australian trypanosomes have previously been identified in marsupials in the eastern states of Australia, with one recent report in brush-tailed bettongs (Bettongia penicillata), or woylie in Western Australia in 2008. This study reports a novel Trypanosoma sp. identified in blood smears, from 7 critically endangered Gilbert's potoroos (Potorous gilbertii) and 3 quokkas (Setonix brachyurus) in Western Australia. Trypanosomes were successfully cultured in vitro and showed morphological characteristics similar to members of the subgenus Herpetosoma. Phylogenetic analysis of 18S rRNA gene sequences identified 2 different novel genotypes A and B that are closely related to trypanosomes previously isolated from a common wombat (Vombatus ursinus) in Victoria, Australia. The new species is proposed to be named Trypanosoma copemani n. sp.

Mathematical models predict that the future of epidemics of drug-resistant pathogens depends in part on the competitive fitness of drug-resistant strains. Considering metacyclogenesis (differentiation process essential for infectivity) as a major contributor to the fitness of Leishmania donovani, we tested its relationship with pentavalent antimony (SbV) resistance in clinical lines. Different methods for the assessment of metacyclogenesis were cross-validated: gene expression profiling (META1 and SHERP), morphometry (microscopy and FACS), in vitro infectivity to macrophages and resistance to complement lysis. This was done on a model constituted by 2 pairs of reference strains cloned from a SbV-resistant and -sensitive isolate. We selected the most adequate parameter and extended the analysis of metacyclogenesis diversity to a sample of 20 clinical lines with different in vitro susceptibility to the drug. The capacity of metacyclogenesis, as measured by the complement lysis test, was shown to be significantly higher in SbV-resistant clinical lines of L. donovani than in SbV-sensitive lines. Together with other lines of evidence, it is concluded that L. donovani constitutes a unique example and model of drug-resistant pathogens with traits of increased fitness. These findings raise a fundamental question about the potential risks of selecting more virulent pathogens through massive chemotherapeutic interventions.

The development and survival of the eggs and larvae of O. circumcincta was studied by spreading the daily faecal output of a sheep over a 2 m square grass plot for 1 week. Observations were carried out for 3 years on material spread at 4-weekly intervals and broadly similar results were obtained in each year. Development time was long in eggs placed outside in January, February, March, November and December. Yields of larvae were small and all were dead within 5 months. During the rest of the year development time was about 2 weeks, yields of larvae were high and larvae survived until July or August of the following year. The significance of these findings in devising systems of grazing management to control parasitic gastroenteritis is discussed.

Orgyia leucostigma haemocytes were able to encapsulate and destroy eggs of Hyposoter species, thereby preventing successful parasitism. When host larvae had previously been parasitized by Cotesia melanoscela, however, this response was not observed, and 3 different Hyposoter species could be reared to maturity in the normally non-permissive host. Appropriate injection experiments established that C. melanoscela virus and venom were both required in order for successful parasitism by Hyposoter to occur. Covalent cross-linking of C. melanoscela viral DNA led to an immune response against Hyposoter larvae, but not eggs, suggesting that an active viral genome may be required for complete development of Hyposoter species in tussock moth larvae.

The habitat of patients with L. minor infection in Trinidad, Tobago and Surinam is described. Three species of Lagochilascaris are redescribed and compared. A new species from Felis concolor is described and a synopsis, with a key to the genus is provided.

The development of L. minor is described from eggs and larval stages obtained from neck lesions of patients. The developmental pattern through third- and fourth-stage larvae was found to conform closely to that of other ascaridoid species, but the tail of the second-stage larva showed a unique conformation.

The earliest stage of development found in human lesions was the third stage, the smallest larva being 1·8 mm in length. The third moult was observed at about 5 mm and the fourth moult at 8 mm. Adult worms were observed with a minimum length of 5 mm in the male and 6 mm in the female. Eggs were present in some females of 8 mm length.

The observations are discussed in relation to previous concepts concerning the affinities, host specificity and evolution of this group of nematodes.

The writer takes pleasure in acknowledging the considerable help he received in this work from several colleagues and friends: Professor J. J. C. Buckley for sending specimens of L. minor and L. buckleyi from the Department of Helminthology, London School of Hygiene and Tropical Medicine; Drs A. G. Chabaud and Marie-Claude Durette from the Museum national d'Histoire naturelle, Paris for sending specimens of L. major; Dr P. Araujo from the Universidade de São Paulo, Faculdade de Farm´cia e Bioquímica for sending specimens of L. minor; Dr J. F. Teixeira de Freitas of the Instituto Oswaldo Cruz, Rio de Janeiro for sending specimens of L. turgida; Drs M. D. Little and P. C. Beaver from the Department of Tropical Medicine, Tulane University New Orleans, for sending specimens of L. minor and notes on their observations relating to L. minor. Grateful acknowledgement is also due to Dr O. H. Siung of the Ministry of Health, Port of Spain, Trinidad, and Dr Cox, Chief Medical Officer, Tobago, Dr A. H. Jonkers and his colleagues at the Trinidad Regional Virus Laboratory, and to His Excellency Dr B. F. J. Oostburg, Minister of Health of Surinam, for their considerable help and co-operation which enabled the writer to observe patients and examine specimens in Trinidad and Surinam. The able technical assistance of Miss Mary Cremin, Mrs A. McKeown and Mrs A. Green is gratefully acknowledged. Financial assistance for this study was provided under grants from the Australian Research Grants Committee, the U.S. Dept. of Health, Education and Welfare no. A. 107023–02, and the University of Queensland Research Grant.

In this study Australorbis glabratus from Puerto Rico, the Dominican Republic, Venezuela, Surinam and Brazil, Biomphalaria pfeifferi from Liberia, and B. boissyi from Egypt were exposed to strains of Schistosoma mansoni from Puerto Rico, Venezuela, Surinam and Egypt, and to seven cross-strains of S. mansoni. In many instances, incompatibilities between vectors and parasites of different endemic areas were noted. It is suggested that these incompatibilities might be accounted for in two ways: (1) interspecific and intraspecific differences between vectors in respect to the physiological factors that are responsible for the development of the parasite in the snail, and (2) physiological differences between strains of the parasite. Evidence would seem to show that there are interspecific physiological differences between Australorbis glabratus and Biomphalaria boissyi; and that there are intraspecific differences between Australorbis glabratus from Brazil and A. glabratus from other countries here dealt with. In addition, it would appear that the parasite of Egypt differs physiologically from the parasites of Puerto Rico, Venezuela and Surinam; and that the parasite of Brazil differs physiologically from the parasites of the latter countries.

We wish to express our gratitude to the following persons for their co-operation in collecting and shipping snails for this study: Drs M. Abdel Azim, C. H. Barlow, J. O. Coutinho, A. Gabaldon, the late W. A. Hoffman, G. W. Luttermoser, J. Oliver-Gonzalez, H. A. Poindexter, Bichat de Almeida Rodriques and A. E. Wolff. We are also indebted to the late Dr W. A. Hoffman, Dr M. Mayer and Dr J. Alves Meira for sending us animals infected with Schistosoma mansoni.

The genetic control of compatibility between laboratory strains of schistosomes and their snail hosts has been studied intensively since the 1970s. These studies show (1) a bewildering array of genotype-by-genotype interactions – compatibility between one pair of strains rarely predicts compatibility with other strains, and (2) evidence for a variety of (sometimes conflicting) genetic mechanisms. Why do we observe such variable and conflicting results? One possibility is that it is partly an artifact of the use of laboratory strains that have been in culture for many years and are often inbred. Here we show that results of compatibility trials between snails and schistosomes – all derived from the same natural population – depend very much on whether one uses laboratory-cultured or field-collected individuals. Explanations include environmental effects of the lab on either host or parasite, and genetic changes in either host or parasite during laboratory culture. One intriguing possibility is that genetic bottlenecks during laboratory culture cause the random fixation of alleles at highly polymorphic loci that control the matched/mismatched status of hosts and parasites. We show that a simple model of phenotype matching could produce dose response curves that look very similar to empirical observations. Such a model would explain much of the genotype-by-genotype interaction in compatibility observed among strains.

Helminth parasites of vertebrates usually select very specific regions or habitats in their hosts, and this is often preceded by a tortuous migration through various host organs. However, the proximate mechanisms of migration and habitat selection have remained enigmatic despite considerable effort by parasitologists. In this paper, a new approach to studying helminth behaviour in the host is proposed. The core idea is that behaviour strategies must be considered from the perspective of the parasites and their perceptions of their environment. A guiding principle is that the environmental features to which an animal responds, and the actions which are required for responding to the environment, form a fundamental unit of behaviour. Thus, we can deduce an animal's behavioural strategy from the details of its response to environmental signals and from its sensory capabilities. The evidence presented suggests that helminth behaviours in the host often occur as fixed (or modal) action patterns which are usually seen in response to constant, or predictable environmental features. Thus, a working hypothesis is that the mechanisms of physiological and biochemical homeostasis within the host provide an extremely predictable environment for the parasite. Under these conditions, a parasite needs to perceive only small subsets of the total information available from the environment to respond appropriately. Studies on sensory and nervous systems of these organisms are critical to understanding parasite perception, but there are formidable technical obstacles that prevent easy access to parasite nervous systems. Therefore, a multidisciplinary approach, using ideas from parasitology, ecology, evolutionary biology and neuroethology, is considered requisite for reconstructing the parasites' behaviour strategies. It is suggested that future directions should pursue integration of studies on sensory physiology with the behavioural ecology of these organisms.

Autoradiography of compressed mouse tissues has been used to estimate the numbers of Se-labelled schistosomula present in different mouse organs. Day 7 parasites extracted from the lungs of donor mice were delivered by injection to the lungs, systemic organs and liver of recipient mice as a discrete pulse. The numbers detected in various locations with time post-injection were then used to analyse the dynamics of intravascular migration. Approximately 98% of cercaria-associated label was lost during the first 14 days of parasite life, two-thirds of this in the first 7 h post-infection. Nevertheless, 99–113% of schistosomula could be detected 30 min post-injection into the locations chosen. The efficiency of the parasite delivery system was 95%. The time required for the number of foci in the lungs to decline to 50%, after injection of parasites via the femoral vein, was 55 h. Adjustment of this data to allow for parasites returning to the lungs after passage round the systemic vasculature gave a value of 30–35 h for the true mean time of lung transit. The distribution of parasites to systemic organs after their exit from the lungs was proportional to the fractional distribution of cardiac output. The probability (P) of a schistosomulum being distributed to splanchnic beds was estimated at 0·32 and its P of being trapped in the hepatic portal distributaries within the liver as 0·72–0·86. On this basis, the entire hepatic portal population of adult schistosomes would be recruited during 2–3 circuits of parasites around the pulmonary-systemic vasculature. The mean transit time of schistosomula through intestinal capillaries was 6·5 h whilst that through other systemic organs combined (muscles, kidneys, brain, etc) was 16 h, considerably more rapid than lung transit. The time taken for schistosomula to pass between organs, in arterial and venous blood, was shown to be less than 30 min in both cases (probably much less).

Observations were made on the histology of tissues from the first 6–10 m of the small intestine from both sheep infected with Trichostrongylus colubriformis and from uninfected controls. In uninfected animals, and in distal samples from infected lambs, villi were tall and covered by tall columnar epithelium, the intestinal crypts were convoluted and the lamina propria was only moderately cellular.In tissues with sub-total villus atrophy and a convoluted surface, the superficial epithelium was usually low columnar, often with an indistinct brush border. More severely affected mucosa was flat, with low surface epithelium and protruding crypt openings. The flat surfaces frequently had leaks of eosinophilic material and polymorphonuclear cells between enterocytes, or through erosions in the epithelium. Such defects were smaller and less frequent in mucosa with a convoluted surface. There were increased mitoses in intestinal crypts and a heavy inflammatory cell infiltrate in the lamina propria. Mast cell, globule leucocyte and theliolymphocyte numbers were not increased in infected sheep.

Fascioliasis pathogenesis depends on fluke burden. In human hyperendemic zones, individual infection intensities reach very high levels and the majority of infected subjects should be in the advanced chronic phase. The rat model offers a useful approach for pathological research in the advanced chronic period. The influence of infection intensity per rat on fluke development, pre-patent period and egg shedding (eggs/g faeces/worm) was analysed in 3 groups (I: 1–3 worms/rat; II: 4–6; III: 7–9). Ontogenetic trajectories of fluke body measures followed a logistic model. Results showed that when the burden increases, the maximum values of fluke measures decrease. The crowding effect is manifest when fluke measures approximate their maximums in the advanced chronic stage. The pre-patent period and egg production decrease when the burden increases. This means that measurements of eggs per gramme of faeces tend to underestimate the fluke burden. The present study demonstrates how to quantify the fascioliasis experimental rat model crowding effect on adult growth, pre-patent period and egg production. This quantification may be of great interest in epidemiological studies and in experimental research on the in vivo actions of different anthelminthic drugs and vaccines, pathology, immunology and resistance studies.

Infection of barbel with 10 species of metazoan parasites including 3 trematodes, 3 acanthocephalans and 4 nematodes was observed in fish collected from 3 localities in the Bulgarian part of the river Danube between summer 2004 and summer 2007. The composition as well as the diversity characteristics of the parasite communities were analysed seasonally and showed a clear correlation with the composition of the invertebrate fauna and water quality. The most prevalent species was the acanthocephalan Pomphorhynchus laevis, which was also the dominant species of the intestinal component communities at all sampling sites. The second most frequent parasite at all Danube localities was Rhabdochona hellichi, which occurred in significantly higher numbers at the less polluted sites. Overall, the diversity of helminth communities increased with decreasing levels of nutrients and pollutants at all sampling sites. Therefore, the composition and diversity of parasite communities may be used to characterize ecosystem health and integrity.

A dihydrofolate reductase has been isolated from free-parasite preparations of the primate malarial parasite, Plasmodium knowlesi. Its properties are similar to those reported for the enzyme from the rodent malarial parasite, P. berghei, even though the base compositions of the DNA of these two species are quite different. The Kms for substrate and cofactor are 3 × 10−6M and 1 × 10−6M respectively and the molecular weight is ˜ 200000. Concentrations of pyrimethamine and trimethoprim as low as 1 × 10−9M and 3 × 10−8M respectively are sufficient to cause 50% inhibition of enzyme activity. The sensitivity to inhibition by pyrimethamine and trimethoprim of growth of cultures of P. knowlesi has also been investigated. Preliminary experiments showed that it was only the schizont stage that was susceptible to the action of the drugs and that in their presence, normal nuclear divisions and segmentation did not occur and subsequently, no reinvasion of fresh red cells took place. The minimum concentrations of drug required to produce these effects were 10−9M for pyrimethamine and 10−7M for trimethoprim. Thus, there is a close correlation between the concentrations of pyrimethamine and trimethoprim required to inhibit the dihydrofolate reductase in a cell-free system and the growth of the parasite in vitro. Pyrimethamine (10−9M) did not, however, affect the incorporation of radioactive precursors into DNA, RNA or protein of schizont stage parasites until after morphological damage could be seen and reinvasion was complete in control cultures. The time courses of incorporation of [14C]algal protein hydrolysate into protein in the presence (10−9M) or absence of pyrimethamine are the same as those described recently with immune serum. The possibility is thus raised as to whether pyrimethamine and immune serum act in the same way.

One of us (P.I.T.) received financial assistance from the World Health Organization. We thank Dr F. Hawking for many helpful discussions, Miss Jane Dunnett and Mr T. Scott-Finnigan for technical assistance and Dr O. D. Standen for samples of pyrimethamine and trimethoprim.

Neospora caninum, the causative agent of neosporosis, is a recently identified apicomplexan parasite which is structurally and biologically closely related to, but antigenically distinct from, Toxoplasma gondii. Molecules associated with the surfaces of N. caninum tachyzoites are likely to participate in the host cell entry process, could be involved in the interaction of the parasite with the immune system, and they could influence the pathogenesis of neosporosis. Isolated N. caninum tachyzoites were extracted with the non-ionic detergent Triton X–114 and were further analysed using a polyclonal anti-N. caninum antiserum. Immunoblots revealed several reactive bands, 1 of which represented a glycoprotein of approximately 36 kDa (Nc-p36). This molecule was present in 2 isolates of Neospora (NC-1 and Liverpool), but was absent in Toxoplasma (RH-strain) tachyzoites. Immunofluorescence and pre-embedding immunogold transmission electron microscopy employing affinity-purified anti-Nc-p36 antibodies showed that the Nc-p36 is a cell surface-associated protein. Immunogold on-section labelling of LR-White-embedded parasites, fixed prior and at defined time-points after host cell entry, demonstrated the presence of this molecule on the surface as well as within the dense granules of N. caninum tachyzoites.

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.

In the present study, polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) analysis was developed to identify 5 species (Trichinella spiralis, Trichinella britovi, Trichinella nativa, Trichinella nelsoni and Trichinella pseudospiralis) and 3 phenotypes of uncertain taxonomic status (Trichinella T5, T6, and T8). Eleven restriction endonucleases were used to restrict 3 DNA fragments (1) a 2800 bp fragment of the 43 kDa excretory–secretory (E–S) protein gene, (2) a 1250 bp fragment amplified with the primer pair SB147A and (3) a 372 bp fragment amplified with the primer pair SB372A. This RFLP method allows the identification of the 8 Trichinella phenotypes as follows: T. spiralis by the HinfI or DdeI endonuclease restriction of the 2800 bp fragment; T. nativa by the RsaI restriction of the 2800 bp fragment, or by the AluI restriction of the 1250 bp fragment; T. britovi and Trichinella T8 by the AluI restriction of the 1250 bp fragments, and can be discriminated between them by the SspI restriction of the 2800 bp fragment; T. pseudospiralis by the MspI restriction of the 372 bp fragment; T. nelsoni by the HhaI or AluI restriction of the 2800 bp fragment; Trichinella T5 by the HhaI restriction of the 2800 bp fragment; Trichinella T6 by the AluI restriction of the 1250 bp fragment; and Trichinella T8 by the SspI or RsaI restriction of the 2800 bp fragment. This study reveals also an intraspecifies polymorphism in the 2800 bp and 1250 bp fragments for T. britovi, Trichinella T5 and T6.