Susceptability of Ascaridia galli to benzimidazole (BZ) was investigated using faecal egg count reduction test (FECRT), in ovo larval development test (LDT) and genetic markers (mutations at codons 167, 198 and 200 of β-tubulin gene). Six flocks (F1−F6) of a commercial laying hen farm with different number of exposure to BZ were recruited. The FECR was calculated by analyzing individual faeces (F1, F2, F4 and F5) before and 10 days after treatment. The LDT was performed on parasite eggs from pooled samples from F1 to F6 and LC50 and LC99 were calculated. DNA was extracted from 120 worms and sequenced for β-tubulin gene. In all flocks, the FECRs were above 95% (lower CI above 90%). No significant difference was observed (p > 0·05) among obtained LC50 (F1/F4 and F2/F5 vs F3/F6) in the LDT. However, LC50 and LC99 were higher than suggested values for declaration of resistance in other nematode species. No variation was observed in codon positions involved in BZ resistance. Overall, our results indicated lack of evidence of resistance to BZ in A. galli. More research is needed to confirm these results and to further optimize the existing tools for detection and monitoring of anthelmintic resistance in A. galli.

The ultrastructural and cytochemical changes accompanying intracellular digestion and cellular defecation in the haematin cell of Diclidophora merlangi have been described. Blood proteins of the host-fish are sequestered by endocytosis and degraded within an interconnecting network of channels that form an integral, but changing, part of the cell. The digestive enzymes involved originate in the granular endoplasmic reticulum and are packaged in the Golgi apparatus and transferred to the channels in Golgi vesicles. The rate of haemoglobin absorption and the activity of the Golgi, as judged by vesicle counts and staining intensities for thiamine pyrophosphatase activity, are stimulated by the introduction of host protein into the gut lumen. The haematin residues of digestion are extruded periodically into the lumen by exocytosis involving membrane fusion. The process is a continuous one and, in worms starved of food, can result in the complete evacuation of pigment from the cell. It is suggested that a lysosomal system operates in the digestive cycle of the haematin cell.

On parasitization with larval Brugia pahangi the infected flight muscle fibres of ‘resistant’ Anopheles labranchiae atroparvus undergo the following ultrastructural changes. The fibres become almost totally devoid of glycogen, their sarcoplasmic reticulum becomes elongate and closely associated with muscle fibrils. These fibrils degenerate and vesicles appear both within the degenerate fibril and within elements of the sarcoplasmic reticulum. Vesicles accumulate around the worm and degenerate to a uniform mass which eventually becomes melanized from its inner edge (next to the parasite) outwards.

The infected flight muscle fibres of both ‘resistant’ Aedes aegypti and ‘susceptible’ Aedes togoi are almost totally devoid of glycogen granules, but show no other ultrastructural change from the uninfected state.

The normal position of attachment of the scolex of H. diminuta from day 6 to day 27 in single worm infections in male Wistar rats was determined. A migration forward from a position of attachment 30–40% down the length of the small intestine to the 10–20% region during day 7 to day 14 was confirmed. A concomitant and slightly faster movement backwards of the posterior of the worm led to the mid-point of the strobila changing from 35 to 50% down the intestine. By day 18 the worms were mature and occupied the whole small intestine except the anterior 10% and the posterior 5–10%. The worms weighed approximately 350 mg dry weight (= 1550 mg fresh weight) at maturity, no significant weight increase occurred thereafter.

6½ and 7½ day-old worms were transplanted from donor rats into the duodenum or posterior ileum. Nearly 100% recovery of the single worm transplants in recipient rats was obtained. Both anterior and posterior implanted worms returned to the region of the intestine from which they had been removed. Migration was measured over periods of 13–72 h and was found to be complete within 24 h. Worms transplanted into the duodenum continued to grow at nearly the normal rate but worm transplants into the posterior ileum lost nearly a day's growth. The significance of this point is discussed.

Opium was found to prevent migration of the tapeworm, but ligation of the bile duct did not prevent the tapeworm migrating forward from a point of insertion near the ileo-caecal junction.

The evidence confirms the concept that a tapeworm is a dynamic organism capable of recognizing a specific region of the intestine, of detecting when it is not in this region, of being able to interpret one or more stimuli to indicate direction and of having a motor system sufficiently coordinated to overcome peristalsis.

We gratefully acknowledge financial support by the Medical Research Council (London) and technical assistance from Miss Helen Stallard, B.Sc., Miss Pat Grant and Miss Gillian Moore. One of us (Trond Braten) wishes also to thank the University of Glasgow for the award of a Visiting Fellowship.

Orangutans (Pongo spp.), Asia's only great apes, are threatened in their survival due to habitat loss, hunting and infections. Nematodes of the genus Strongyloides may represent a severe cause of death in wild and captive individuals. In order to better understand which Strongyloides species/subspecies infect orangutans under different conditions, larvae were isolated from fecal material collected in Indonesia from 9 captive, 2 semi-captive and 9 wild individuals, 18 captive groups of Bornean orangutans and from 1 human working with wild orangutans. Genotyping was done at the genomic rDNA locus (part of the 18S rRNA gene and internal transcribed spacer 1, ITS1) by sequencing amplicons. Thirty isolates, including the one from the human, could be identified as S. fuelleborni fuelleborni with 18S rRNA gene identities of 98·5–100%, with a corresponding published sequence. The ITS1 sequences could be determined for 17 of these isolates revealing a huge variability and 2 main clusters without obvious pattern with regard to attributes of the hosts. The ITS1 amplicons of 2 isolates were cloned and sequenced, revealing considerable variability indicative of mixed infections. One isolate from a captive individual was identified as S. stercoralis (18S rRNA) and showed 99% identity (ITS1) with S. stercoralis sequences from geographically distinct locations and host species. The findings are significant with regard to the zoonotic nature of these parasites and might contribute to the conservation of remaining orangutan populations.

Studies of population genetic structure of parasites can be used to infer which parasite genes are under selection. Here, the population structure of 4 genes associated with drug resistance of Plasmodium falciparum (the chloroquine resistance transporter, pfcrt, dihydrofolate reductase, dhfr, dihydropteroate synthase, dhps, and multi-drug resistance, pfmdr-1) were examined in parasite populations in 3 villages in eastern Sudan and in an urban area of Khartoum, the capital. In order to differentiate the effects of drug selection from neutral influences on population structure, parasites were also genotyped for 3 putatively neutral microsatellite loci (polyα, TA81 and pfg377), and for 2 antigenic loci that are either under balancing selection or neutral, merozoite surface protein 1 and 2, (MSP-1 and MSP-2). Cross-sectional surveys were carried out during the peak transmission (wet) season and in the ensuing dry season. No significant variation in frequencies of MSP-1 and MSP-2 alleles was seen among villages in the eastern region and between the villages and Khartoum, nor between the wet and dry season. However, the drug resistance genes, pfmdr-1, pfcrt and dhfr and to a lesser extent the microsatellite loci showed high FST values when comparing villages with Khartoum, indicating strong geographical differentiation at these loci. Moreover, variation in frequencies of the drug resistance genes, pfmdr-1, pfcrt and dhfr, was observed between the wet and dry season. These differences most probably reflect the variation in drug pressure between each region, and in drug usage between the wet and dry season in a given region.

Prolonged diapause is usually interpreted as an adaptation to unpredictable environmental conditions and resource availability. Many parasites usually face highly unpredictable environments, therefore prolonged diapause should be common among these organisms. Here we examine the occurrence and frequency of prolonged diapause in the ectoparasite Carnus hemapterus (Diptera: Cyclorrhapha, Acalyptratae). We found that the studied population is polymorphic with respect to diapause duration. Emergence of carnid flies after 2 and 3 wintering seasons was therefore detected in around 17% and 21% of the samples respectively. The number of flies with prolonged diapause ranked 0·88–50% with respect to the number of flies emerging during the first spring. Both the occurrence of prolonged diapause and the number of flies with a long life-cycle are related to the number of flies emerging during the first spring. The emergence pattern of flies with prolonged diapause was very similar to that observed for flies with a short cycle and occurred in synchrony with the occurrence of hosts. Prolonged diapause has been frequently reported in plant-feeding insects and in some host-parasitoid systems, but this is, to our knowledge, the second report ever on prolonged diapause in true parasites of animals. We discuss the reasons for the apparent rarity of prolonged diapause among these organisms.

A major goal of community ecology is to identify and explain non-random patterns of species composition. To date, the search for nested patterns in parasite component communities of the same fish host species has not been attempted, despite the fact that this higher hierarchical level is more relevant to nestedness analyses. The aims of this study are first, to determine the structure of component communities – considering ectoparasites and endoparasites separately – of a marine fish (Sebastes capensis) with an extended geographical distribution along the southeastern Pacific and, second, to explain these patterns by taking into account the extrinsic factors associated with the distribution of this host fish. From April to September 2003 and from April to August 2004, 537 fish were captured from different latitudes along the southeastern Pacific. The component communities of both ectoparasites and endoparasites of this fish host showed significant nested subset patterns. However, the type of nestedness pattern differed between ectoparasites and endoparasites. Ectoparasite component communities of S. capensis show higher species richness between latitude 30°S and 40°S, whereas endoparasite component communities show higher species richness between 40°S and 52°S. A nested pattern in ectoparasite component communities of S. capensis result from the gradual loss of some ectoparasites species southward and northward of the central part of their latitudinal distribution, which can be explained by the interaction of S. capensis with other host fish species from the central Chilean coast. Nestedness in endoparasite component communities of S. capensis is produced by the gains and losses of species toward the south of their latitudinal distribution, caused by changes in their prey-items (intermediate hosts) along their latitudinal distributional range.

Leishmania produce several types of mucin-like glycoproteins called proteophosphoglycans (PPGs) some of which are secreted while others are found on the surface of promastigotes and amastigotes. These proteins are thought to be important in the transmission, invasion and subsequent intracellular survival of parasites. The structure and function of PPGs are species and stage-specific in the case of L. major and L. mexicana, but no such information has hitherto been available for L. donovani. This study presents, for the first time, an initial characterization (localization) of PPG in sodium stibogluconate (SSG)-resistant and sensitive clinical isolates of L. donovani from Bihar (India) by confocal microscopy, flow cytometry and Western blotting using antibodies to L. major PPG. Confocal microscopy analysis revealed that both promastigotes and amastigotes possess PPG on their cell membrane and flagellar pocket membrane but its expression was variable in different isolates. The quantitative analysis by FACS and Western blotting showed that the expression and intensity of PPG bands was higher in SSG-resistant isolates. This study suggests the possibilities of involvement of PPG in drug-resistant mechanisms and of using PPG abundance as a marker for identifying drug-resistant clinical isolates in Indian kala azar.

The age dependency of the mortality, spontaneous de-tailing and infectivity of cercariae of Schistosoma mansoni has been determined at 25 °C. Infectivity was assessed with respect to stratum corneum-like differentiated human keratinocyte cultures (validated by comparison with fresh human skin samples) and displayed a complex age-dependent pattern. From 1 to 9 h post-emergence cercariae showed a plateau of maximal infectivity (around 90% attachment). Thereafter, infectivity declined. Immediately after release, infectivity at around 60% was significantly lower than the plateau values and this could be an adaptation for spatial dispersal of cercariae. Age-dependent patterns of cercarial mortality and spontaneous de-tailing closely mirrored the infectivity pattern except in relation to the low initial infectivity value. These findings suggest that, at a population level, the age-dependent decline in cercarial infectivity towards human skin is essentially driven by cercarial mortality. The recently described phenomenon of delayed tail loss (DTL) in S. mansoni cercariae infecting human skin is confirmed in the present study. For cercariae aged up to 13·5 h post-emergence, 90% or more of invading cercariae took their tails with them into the keratinocyte culture. The infection dynamics described in this study suggest that diurnally shed S. mansoni cercariae, with peak emergence around mid-day, will have near maximal infectivity towards humans in contact with water through all remaining daylight hours in the tropics.

Parasites should be better at infecting hosts from sympatric populations than allopatric populations most of the time (parasite local adaptation). In a previous study of a population of snail parasites (Microphallus sp.) from Lake Alexandrina, New Zealand, we found that Microphallus was more infective to snails (Potamopyrgus antipodarum) in shallow water but not in deep water. Here, we repeated the original study and also monitored the development of the parasite. We found that parasites from shallow water were more infective to hosts from shallow water and developed more rapidly in these hosts. In contrast, parasites from deep water were not more infective to hosts from deep water and did not develop more rapidly in them. These results suggest clinal variation in the susceptibility of these snails, with shallow-water snails more susceptible than deep-water snails. We offer 2 possible explanations for these results. First, gene flow in the Microphallus population is primarily from shallow to deep water, leading to an asymmetric pattern of local adaptation. Alternatively, snails from shallow water may be more susceptible for reasons independent of gene flow, perhaps due to differences in host condition between habitats.

Host-parasite interactions are shaped by the co-evolutionary arms race of parasite virulence, transmission success as well as host resistance and recovery. The virulence and fitness of parasites may depend on host condition, which is mediated, for instance, by host energy constraints. Here, we investigated to what extent stress imposed by predation threat and environmental pollutants influences host-parasite interactions. We challenged the crustacean host Daphnia magna with the sterilizing bacterial endoparasite Pasteuria ramosa and simultaneously exposed the host to fish kairomones, the pesticide carbaryl or both stressors. While parasite virulence, measured as impact on host mortality and sterilization, increased markedly after short-term pesticide exposure, it was not influenced by predation threat. Parasite fitness, measured in terms of produced transmission stages, decreased both in fish and pesticide treatments. This effect was much stronger under predation threat than carbaryl exposure, and was attributable to reduced somatic growth of the host, presumably resulting in fewer resources for parasite development. While the indirect impact of both stressors on spore loads provides evidence for host condition-dependent parasite fitness, the finding of increased virulence only under carbaryl exposure indicates a stronger physiological impact of the neurotoxic chemical compared with the effect of a non-toxic fish kairomone.

The Global Program for the Elimination of Lymphatic Filariasis (GPELF) intends to achieve its aims through yearly mass treatments with albendazole (ABZ) combined with ivermectin (IVM) or diethylcarbamazine (DEC). The use of ABZ and IVM separately to combat parasites of veterinary importance has, on many occasions, resulted in widespread drug resistance. In order to help predict the spread of potential ABZ resistance alleles through a population of Wuchereria bancrofti, we have developed a mathematical model that incorporates population genetics into EPIFIL, a model which examines the transmission dynamics of the parasite. Our model considers the effect of the combined treatments on the frequency of a recessive allele, which confers ABZ resistance. The model predicts that after 10 yearly treatments with ALB and DEC, 85% coverage and an initial resistance allele frequency of 5%, the frequency of the resistance genotype will increase from 0·25 to 12·7%. If non-random mating is assumed, the initial genotype frequency will be 2·34% and will increase to 62·7%. ABZ and IVM combination treatment may lead to weaker selection for this genotype. Treatment coverage, initial allele frequencies and number of treatments also affect the rate of selection.

We explored the distribution of Cardicola chaetodontis in chaetodontid fishes from the Great Barrier Reef. We found just four infections of adult worms in 238 individuals of 26 chaetodontid species. By contrast, eggs were present in hearts of 75 fishes (31·5%) and 19 of 26 chaetodontid species (all Chaetodon species). In 10 cases eggs contained moving miracidia; all the others were dead and degenerating. Eggs were sought in the gills of 51 individual fish. There were 17 cases of eggs being present in gills while present in the heart, but also 13 cases where eggs were absent from gills but present in the heart, suggesting that eggs remain longer in heart tissue than in gills. ITS2 rDNA sequences from two adult worms and eggs extracted from gills of five fishes (all different species) were identical to previously reported sequences of C. chaetodontis except for a single base-pair difference in two samples. We conclude that aporocotylid eggs trapped in fish heart tissues may inform understanding of the distributions and host ranges of aporocotylids, especially where adult prevalence is low. The low host-specificity of C. chaetodontis contrasts with higher specificity of trematodes of chaetodontids that have trophic transmission.

Chagas disease, which is caused by the parasite Trypanosoma cruzi, affects approximately 7–8 million people in Latin America. The drugs available to treat this disease are ineffective against chronic phase disease and are associated with toxic side effects. Therefore, the development of new compounds that can kill T. cruzi at low concentrations is critically important. Herein, we report the effects of a novel 3-arylideneindolin-2-one that inhibits sirtuins, which are highly conserved proteins that are involved in a variety of physiological processes. The compound KH-TFMDI was tested against the epimastigote, trypomastigote and amastigote forms of T. cruzi, and its effects were evaluated using flow cytometry, light and electron microscopy. KH-TFMDI inhibited the replication of T. cruzi intracellular amastigotes with an IC50 of 0·5±0·2 μm, which is significantly lower than the IC50 of benznidazole. The compound also lysed the highly infectious bloodstream trypomastigotes (BST) with LC50 values of 0·8±0·3 μm at 4 °C and 2·5±1·1 μm at 37 °C. KH-TFMDI inhibited cytokinesis and induced several morphological changes in the parasite, leading to its death by apoptosis and autophagy. This study highlights sirtuins as a potential new target for Chagas disease therapy.

The sexual life-history traits of Schistosoma mansoni have been reviewed to compare male and female performance and pathogenicity against Biomphalaria glabrata during the life-cycle. A meta-analysis was used on pooled results from different experiments. In most cases, there was no difference between males and females but male cercariae were significantly more infectious than female cercariae. Conversely, cercarial production and cercarial life-span were significantly greater for females than for males; furthermore, females have a tendency to occur in molluscs of larger size. Each difference is discussed and interpreted when possible in terms of male and female differences in transmission strategies. The female strategy may consist of producing many long-living larvae. The male strategy may consist of producing few short-living larvae and would invest in the quality of these larvae instead of their quantity or their life-span.

Leishmania parasites are able to survive in host macrophages despite the harsh phagolysosomal vacuoles conditions. This could reflect, in part, their capacity to secrete proteins that may play an essential role in the establishment of infection and serve as targets for cellular immune responses. To characterize Leishmania major proteins excreted/secreted early after promastigote entry into the host macrophage, we have generated antibodies against culture supernatants of stationary-phase promastigotes collected 6 h after incubation in conditions that partially reproduce those prevailing in the parasitophorous vacuole. The screening of an L. major cDNA library with these antibodies led us to isolate 33 different cDNA clones that we report here. Sequence analysis revealed that the corresponding proteins could be classified in 3 groups: 9 proteins have been previously described as excreted/secreted in Leishmania and/or other species; 11 correspond to known proteins already characterized in Leishmania and/or other species although it is unknown whether they are excreted/secreted and 13 code for unknown proteins. Interestingly, the latter are transcribed as shown by RT-PCR and some of them are stage regulated. The L. major excreted/secreted proteins may constitute putative virulence factors, vaccine candidates and/or new drug targets.

Host–parasite associations are complex interactions dependent on aspects of hosts (e.g. traits, phylogeny or coevolutionary history), parasites (e.g. traits and parasite interactions) and geography (e.g. latitude). Predicting the permissive host set or the subset of the host community that a parasite can infect is a central goal of parasite ecology. Here we develop models that accurately predict the permissive host set of 562 helminth parasites in five different parasite taxonomic groups. We developed predictive models using host traits, host taxonomy, geographic covariates, and parasite community composition, finding that models trained on parasite community variables were more accurate than any other covariate group, even though parasite community covariates only captured a quarter of the variance in parasite community composition. This suggests that it is possible to predict the permissive host set for a given parasite, and that parasite community structure is an important predictor, potentially because parasite communities are interacting non-random assemblages.

Temperature is an important factor influencing the biology of organisms and is intrinsically linked to climate change. The establishment of trematodes in target hosts is potentially susceptible to temperature changes effecting parasite infectivity or host susceptibility, and therefore in order to develop predictive frameworks of host–parasite dynamics under climate change large-scale analyses are required. The present study analyses the thermodynamics of the infectivity of larval trematodes including miracidia, cercariae and metacercariae from experimental data contained in the scientific literature using the Arrhenius critical incremental energy of activation (E*), an accurate measure of temperature-driven reaction rates. For miracidia and cercariae, infectivity increases as the temperature rises reaching a plateau over optimal thermal ranges before declining at higher temperatures. In contrast, metacercarial infectivity is at its greatest at low temperatures, declining with increasing temperature.

Amoebiasis, infection by the protozoan parasite Entamoeba histolytica, remains a global health problem, despite the availability of effective treatment. While improved sanitation could lead to the eradication of this disease, it is unlikely that this will occur worldwide in the foreseeable future; thus alternative measures must be pursued. One approach is to develop a vaccine to prevent this deadly disease. Clinical studies indicate that mucosal immunity may provide some protection against recurrent intestinal infection with E. histolytica, but there is no clear evidence that protective immunity develops after amoebic liver abscess. Over the past decade, progress in vaccine development has been facilitated by new animal models that allow better testing of potential vaccine candidates and the application of recombinant technology to vaccine design. Oral vaccines and DNA-based vaccines have been successfully tested in animals models for immunogenicity and efficacy. There has been significant progress on a number of fronts, but there are unanswered questions regarding the effectiveness of immune responses in preventing disease in man and, as yet, no testing of any of these vaccines in humans has been performed. In addition, there are strong economic barriers to developing an amoebiasis vaccine and questions about how and where an effective vaccine would be utilized.