The vectorial capacity of Biomphalaria pfeifferi from Ndiangue, Senegal, was investigated with an allopatric isolate of Schistosoma mansoni from Nkolbisson, Cameroon. The snail infection rate after exposure to a single miracidium per snail (MD1) was 56·3%, and 91·6% for snails exposed to 5 miracidia per snail (MD5). The minimum pre-patent period was 21 days. The mean total cercarial production for the MD1 group was 18511 cercariae per snail, and 9757 cercariae for the MD5 group. The maximum production of cercariae for 1 day was 4892 observed in a snail from the MD1 group at day 43 post-infection. The mean longevity of snails was higher in group MD1 (88 days p.i.) than in group MD5 (65 days p.i.). The chronobiological emergence pattern revealed a circadian rhythm with one shedding peak at mid-day. Comparisons are made with the vectorial capacity of the sympatric combination of B. pfeifferi Senegal/S. mansoni Senegal.

An account is given of some Microsporidia found in certain fishes and insects in eastern Canada, among which are new species of Nosema, Perezia and Gurleya.

Nosema pimephales n.sp. produces large cysts or tumours in the abdomen of Pimephales promelas, one out of a large number from Lake Guindon, Province of Quebec, being infected.

Nosema branchiale Nemeczek has been observed from a cod, Gadus callarias. The organism is shown to be a Nosema, though the incomplete original description has caused doubts as to whether some other genus was involved. Further details are now given.

Nosema apis Zander and N. bombi Fantham & Porter have been found in Canada in hive-bees and humble-bees respectively, the latter being recorded from a new host, Bombus vagans.

Glugea hertwigi n.var. canadensis is described from Osmerus mordax from Lake Edward.

Perezia aeschnae n.sp. has been found in nymphs of the large dragonfly, Aeschna grandis, collected near Montreal and is described and illustrated.

Perezia legeri Paillot has been observed in larvae of Pieris brassicae.

These appear to be the first records of Perezia from insects in North America, and the zoogeographical distribution of the genus is extended to the Odonata.

Gurleya aeschnae n.sp, is described from a nymph of Aeschna grandis. It is the first species of Gurleya to be described from the Odonata and the first record of the genus from the North American continent.

Thelohania corethrae Schuberg & Rodriguez is described from the larvae of Chaoborus flavicans. Measurements of the parasite, which were lacking in the original description, are now supplied.

Thelohania bracteata from larvae of Simulium bracteatum and larvae and one adult S. venustum and Thelohania fibrata from larvae of Simulium venustum are recorded from places in the Province of Quebec. The need of reinvestigation of the species of Thelohania from various Simulium and the possibility of there being but one species, Thelohania varians Debaisieux, are indicated.

Thelohania legeri Hesse is recorded as a parasite of larvae of Anopheles punctipennis in Quebec Province and of A. gambiae in Zululand. It is probably the most widely distributed species of Thelohania, occurring in Anophelines in Europe, Asia, Africa and North America.

Some general remarks regarding zoogeographical distribution, habitat, host-specificity and possible origin of species and varieties in connexion with Gurleya, Perezia and Thelohania are presented.

Extensive cross-reactions have been found between cultural forms of trypanosomes of the ‘brucei’ group by the agglutination reaction. The antigen (or antigens) responsible for agglutination are apparently specific to the ‘brucei’ group of trypanosomes. These antigens are also quite stable to the presence of specific antiserum in contrast to the serotype of the blood trypanosomes which are known to be altered in the presence of specific antiserum.

Red fox (Vulpes vulpes) is the most widely distributed canid in the world and an important source of multiple zoonotic pathogens capable of causing life-threatening diseases, such as rabies and alveolar echinococcosis. Informing general public of potential risks related to foxes is becoming more important since the fox densities have increased in many countries and the species is colonizing urban areas in Europe and around the world with increasing pace, bringing zoonotic pathogens to the immediate neighbourhood of humans and their companion animals. The aim of this study was to examine the parasite fauna of red foxes in Estonia. We found in Estonian foxes a total of 17 endoparasite taxa, including ten zoonotic species. All the analysed individuals were infected and the average parasite species richness was 6·37. However, the infection rates varied to a very large extent for different parasite species, ranging from 0·9 to 91·5%. Of zoonotic species, the highest infection rate was observed for Alaria alata (90·7%), Eucoleus aerophilus (87·6%) and Uncinaria stenocephala (84·3%). The prevalence of tapeworm Echinococcus multilocularis, a causative agent for alveolar echinococcosis, was also relatively high (31·5%), presenting a potential risk to human health.

The burrowing mite Sarcoptes scabiei is the causative agent of the highly contagious disease sarcoptic mange or scabies. So far, there is no in vitro propagation system for S. scabiei available, and mites used for various purposes must be isolated from infected hosts. Lack of parasite-derived material has limited the possibilities to study several aspects of scabies, including pathogenesis and immunity. It has also hampered the development of high performance serological assays. We have now constructed an S. scabiei cDNA expression library with mRNA purified from mites isolated from red foxes. Immunoscreening of the library enabled us to clone a full-length cDNA coding for a 102.5 kDa protein. Sequence similarity searches identified the protein as a paramyosin. Recombinant S. scabiei paramyosin expressed in Escherichia coli was recognized by sera from dogs and swine infected with S. scabiei. We also designed a small paramyosin construct of about 17 kDa that included the N-terminal part, an evolutionary variable part of the helical core, and the C-terminal part of the molecule. The miniaturized protein was efficiently expressed in E. coli and was recognized by sera from immunized rabbits. These data demonstrate that the cDNA library can assist in the isolation of important S. scabiei antigens and that recombinant proteins can be useful for the study of scabies.

Previous studies from this laboratory have suggested the presence of antibody-binding molecules on the surface of Taenia crassiceps metacestodes. We now report the purification of a T. crassiceps Fcγ -binding protein which has an equivalent molecular size (96 kDa), is antigenically similar and exhibits significant amino acid sequence homology to schistosome paramyosin. The similarities in molecular weight of the T. crassiceps protein, Schistosoma mansoni paramyosin and antigen B of T. solium, the close amino acid sequence homologies between the T. crassiceps protein and S. mansoni paramyosin and between S. mansoni paramyosin and antigen B of T. solium, and the antigenic similarity of the T. crassiceps protein with paramyosin indicates that this family of platyhelminth proteins are closely related. The known characteristics of T. solium antigen B (collagen binding affinity; disruption of complement function) and the Fcγ -binding activity of the T. crassiceps molecule suggests that this class of proteins may be multifunctional, fulfilling not only a structural role but also as components interacting with the host immune system to increase parasite survival.

The biosynthesis of phospholipids is extensive in Plasmodium knowlesi-infected simian erythrocytes due to the synthesis of membranes by this single-cell eukaryote in a host erythrocyte devoid of any pathway for lipid biosynthesis. In the present paper, we show that the incorporation of [3H]glycerol, which reflects de novo biosynthesis, is better studied at 300 μM−1 mM than at the trace doses, since this non-physiological precursor does not modify the amount of phosphatidylcholine biosynthesis from [3H]choline. Time-course incorporation of radioactive glycerol, oleate, lysophosphatidylcholine, choline, and inositol in RPMI 1640 medium containing nutrients for lipid synthesis showed that the optimum incubation time for phospholipid studies is 60–90 min, after which radioactive incorporation slows considerably. On the other hand, studies with [14C]serine revealed that incubation for 2–3 h is necessary for isotopic labelling of phosphatidylcholine via phosphatidylserine decarboxylation and phosphatidylethanolamine N-methylation. Incorporation of the various fatty acids into individual lipids was related to the molecular species composing each of them. Studies with [14C palmitoyl] lysophosphatidylcholine showed a very fast intracellular release of radioactive fatty acids, which indicates a potent lysophospholipase activity. Taken together, these data define the indispensable conditions for an experimental system suitable for further studies.

Using groups of 4 baboons (Papio anubis), 21·0% of a trickle exposure of 480 Schistosoma mansoni cercariae/baboon (10/week for 48 weeks) were recovered as adult worms (Group A) compared with 72·6% from a single massive exposure of 2500 cercariae/baboon (Group C). Group B, exposed first to the trickle and then to the massive exposure simultaneously with Groups A and C, yielded a worm recovery of 54% which was slightly but significantly less than Group C. The trickle infection apparently induced a substantial resistance to light re-exposure, but only a partial, although significant, resistance to a massive re-exposure. In Group B, however, there was a marked reduction in the degree of gross pathology, despite high tissue egg production by the mature challenge worms. The parasitological results, in terms of resistance to reinfection by and development of pathology to a trickle infection, are not materially different from those obtained in studies using conventional heavy primary and challenge exposures with S. mansoni. The significance of these findings is discussed in relation to the epidemiology of human schistosomiasis mansoni in which heavy exposures are believed to be the exception rather than the rule.

Mean villus height, crypt depth and the number of 5-HT-positive enterochromaffin (EC) cells have been examined in two regions of the small intestine (20–30° and 60–70° distance from the pylorus) of male, 6 to 8-week-old, C57 mice following a 5-cysticercoid infection of the rat tapeworm, Hymenolepis diminuta. Test mice and sham-infected controls were autopsied 0, 4, 8, 10, 14 and 28 days post-primary infection (p-1°-i) and 2, 4, 5, 7 and 14 days post-secondary infection (p-2°-i), administered 28 days p-1°-i. Morphometric analysis revealed a statistically significant increase in crypt depth in the 60–70°o intestine region in infected mice during both primary and secondary infections; no significant deviation from the control was observed for villus height in infected mice. Statistical analysis showed a significant increase in the number of 5-HT-positive EC cells in infected mice. This response occurred in the lower portion of the intestine on days 10-p-1°-i and 5-p-2°-i, and was not due to increased mucosal surface area in this region. Results are discussed with reference to murine cestode rejection and the possible involvement therein of the neuroendocrine system.

Based on 18S rRNA sequence analyses 2 distinct genotypes of piroplasms have been described in raccoons. One genotype resides in the Babesia sensu stricto clade and the other in the Babesia microti-like clade. Since these organisms appear morphologically indistinguishable, it is unclear which strain is responsible for the majority of the infections in raccoons. In order to overcome these limitations we performed a molecular survey of raccoons using polymerase chain reaction assays specific for each genotype. We tested blood samples from 41 wild raccoons trapped in eastern North Carolina using PCR assays and found that 95% (39/41) had detectable piroplasm DNA. Ninety percent (37/41) of the samples contained Babesia sensu stricto DNA and 83% (34/41) samples contained Babesia microti-like DNA. DNA from both genotypes was present in 76% (31/41) samples suggesting a very high rate of co-infections. The presence of dual piroplasma infections in carnivores appears to be an uncommon finding. This study highlights the need for molecular assays for the accurate identification of piroplasma. Further studies are indicated to investigate the ability of these parasites to infect domestic animals as well as their zoonotic potential.

Trophically transmitted parasites are likely to strongly influence food web-structure. The extent to which they change the trophic ecology of their host remains nevertheless poorly investigated and field evidence is lacking. This is particularly true for acanthocephalan parasites whose invertebrate hosts can prey on other invertebrates and contribute to leaf-litter breakdown. We used a multiple approach combining feeding experiments, neutral lipids and stable isotopes to investigate the trophic ecology of the freshwater amphipod Gammarus roeseli parasitized by the bird acanthocephalan Polymorphus minutus. Infected compared to uninfected amphipods consumed as many dead isopods, but fewer live isopods and less leaf material. Infection had no influence on the total concentration of neutral lipids. Contrary to what we expected based on laboratory findings, the nitrogen isotope signature, which allows for the estimation of consumer's trophic position, was not influenced by infection status. Conversely, the carbon isotope signature, which is used to identify food sources, changed with infection and suggested that the diet of infected G. roeseli includes less perilithon (i.e. fixed algae on rocks, stones) but more terrestrial inputs (e.g. leaf material) than that of uninfected conspecifics. This study shows evidence of changes in the trophic ecology of P. minutus-infected G. roeseli and we stress the need to complement feeding experiments with field data when investigating top-down effects of infection in an opportunistic feeder which adapts its diet to the available food sources.

Detection of taeniasis carriers of Taenia solium is essential for control of cysticercosis in humans and pigs. In the current study, we assessed the positive detection rate of a self-detection tool, stool microscopy with direct smear and coproPCR for taeniasis carriers in endemic Tibetan areas of northwest Sichuan. The self-detection tool through questioning about a history of proglottid expulsion within the previous one year showed an overall positive detection rate of more than 80% for Taenia saginata, T. solium and T. asiatica. The positive detection rate was similar for T. saginata and T. solium. In 132 taeniid tapeworm carriers, 68 (51·5%) were detected by microscopy and 92 (69·7%) were diagnosed by coproPCR. A combination of microscopy and coproPCR increased the positive detection rate to 77·3%. There remained 10 cases (7·6%) coproPCR negative but microscopy positive. Due to the high cost and complicated process, coproPCR is required for the identification of Taenia species only when necessary, though it had a significant higher positive detection rate than microscopy. Combined use of self-detection and stool microscopy are recommended in community-based mass screening for taeniases in this Tibetan area or in other situation-similar endemic regions.

The specific objectives of this study were to elucidate metal toxicity to hatching, survival and avoidance behaviour of Schistosoma mansoni miracidia. The toxicity of cadmium, zinc, and cadmium/zinc mixtures at concentrations ranging from 10000 to 10μg/l was investigated. Metal mixture toxicity investigation was undertaken with equal concentrations of the metals. The hatching of miracidia from eggs was inhibited by concentrations of 1000–10000μg/l of single metals. Metal mixtures had no effect on egg hatching. Survival of miracidia was reduced by increasing metal concentration except at concentrations of 10μg/l for single metal toxicity where survival was increased above the control. Miracidia demonstrated a rapid avoidance behaviour when briefly exposed to heavy metals. The mechanisms of metal toxicity to miracidia are briefly discussed.

Neobenedenia girellae, a capsalid monogenean, is a destructive fish parasite. We studied the lipid content and fatty acid composition of N. girellae and the skin and cutaneous mucus of a host fish, the amberjack Seriola dumerili (Carangidae). The lipid content of adult N. girellae was less than one-fourth that of both the skin and cutaneous mucus of its host. Adult N. girellae, S. dumerili skin and mucus had a relatively high weight-percentage of C16:0, C18:1(n-9), C18:0 and C22:6(n-3) fatty acids. When S. dumerili were fed a diet supplemented with [13C] fatty acids, [13C] fatty acids were detected in S. dumerili skin and adult N. girellae on S. dumerili, but no [13C] fatty acids were detected in the S. dumerili cutaneous mucus. In addition, the epidermis of S. dumerili, attached with N. girellae, was markedly thin. These results suggest that N. girellae feeds primarily on host epithelial cells. We then infected 2 host fishes, S. dumerili and the spotted halibut Verasper variegatus (Pleuronectidae; a host less susceptible to N. girellae infection), and compared the fatty acid composition of N. girellae with that of the skin and cutaneous mucus of the hosts. The fatty acid profiles from all samples were qualitatively and quantitatively similar. Thus, the fatty acid composition of the host may not contribute to the difference in susceptibility between S. dumerili and V. variegatus. These results may serve to develop new strategies for the control of N. girellae infections.

Although the rumen fluke, Calicophoron daubneyi is now very common and widespread throughout Western Europe, reports of clinical cases are still rare. This study explores the epidemiological background to a severe rumen fluke outbreak in 6-month-old heifers on a dairy farm in Ireland. Sequence analysis of the cytochrome oxidase subunit 1 (Cox1) gene of the rumen fluke metacercariae on pasture failed to identify predominant, possibly pathogenic subtypes. However, estimates of metacercarial load indicated that the animals were exposed to a daily dose of about 5334 C. daubneyi metacercariae for a period of 3 weeks resulting in the build-up of very large numbers of immature worms in the small intestine. It is hypothesized that specific environmental conditions may favour this parasite over its competitor, the liver fluke, Fasciola hepatica, possibly by allowing it to emerge earlier. The possibility that C. daubneyi may be better adapted to the Irish climate than F. hepatica together with the fact that selective treatment against F. hepatica effectively frees the niche for C. daubneyi, may result in the gradual replacement of F. hepatica by C. daubneyi.

The possibility that much of the spatial and temporal variation in helminth communities in freshwater fish can be explained in terms of metapopulation theory was tested by examining helminth component communities of eels sampled from 3 localities in the River Exe and 5 of its tributaries on 2 occasions at an interval of 3 years. Four specific predictions of metapopulation theory in relation to community dynamics were tested. The prediction that parasite species could be recognized as common and rare and that this was sensitive to scale was met. The prediction that core species would be more widely distributed and have a higher dispersal ability was met only in part. The prediction that similarity between communities would increase with connectivity and decrease with distance apart was not met. The final prediction that species would go locally extinct and be replaced by rescue effects was not met. There was evidence of local extinctions; not of eel specialists but of species using other fish species as their principal definitive hosts. Eel helminth communities were heavily dominated by 3 species of eel specialists which were relatively stable and responsible for most of the similarity and its changes in space and time. It was concluded that metapopulation theory did not provide a very satisfactory explanation for the changes in the helminth communities in eels and reasons for this included the inherent difficulty of applying metapopulation theory to parasites and the fact that the helminth communities in eels in the River Exe were atypical in being dominated by eel specialists.

No vaccines or safe chemotherapy are available for Chagas disease. Pentamidine and related di-cations are DNA minor groove-binders with broad-spectrum anti-protozoal activity. Therefore our aim was to evaluate the in vitro efficacy of di-cationic compounds – DB1645, DB1582, DB1651, DB1646, DB1670 and DB1627 – against bloodstream trypomastigotes (BT) and intracellular forms of Trypanosoma cruzi. Cellular targets of these compounds in treated parasites were also analysed by fluorescence and transmission electron microscopy (TEM). DB1645, DB1582 and DB1651 were the most active against BT showing IC50 values ranging between 0·15 and 6·9 μm. All compounds displayed low toxicity towards mammalian cells and DB1645, DB1582 and DB1651 were also the most effective against intracellular parasites, with IC50 values ranging between 7·3 and 13·3 μm. All compounds localized in parasite nuclei and kDNA (with greater intensity in the latter structure), and DB1582 and DB1651 also concentrated in non-DNA-containing cytoplasmic organelles possibly acidocalcisomes. TEM revealed alterations in mitochondria and kinetoplasts, as well as important disorganization of microtubules. Our data provide further information regarding the activity of this class of compounds upon T. cruzi which should aid future design and synthesis of agents that could be used for Chagas disease therapy.

We describe the infectivity, virulence, cultivating conditions, and phylogenetic positions of naturally occurring oomycete parasites of Daphnia, invertebrates which play a major role in aquatic food webs. Daphnia pulex individuals were found dead and covered by oomycete mycelia when exposed to pond sediments. We were able to extract 4 oomycete isolates from dead Daphnia and successfully cultivate them. Using the ITS and LSU rDNA sequences, we further showed these isolates to be distinct species. The isolates were experimentally demonstrated to be parasitic and not saprobic. After exposure to the parasites, Daphnia mortality was much higher than that reported for Daphnia infected with other known parasite species. Therefore, it is likely that oomycete parasites are important selective pressures in natural Daphnia populations. Moreover, their close phylogenetic relationship to parasites of fish and algae suggests that the stability of aquatic food webs (i.e. fish–Daphnia–algae) might be influenced by the shared parasite communities.

In parasites with complex life cycles the transmission of free-living infective stages can be influenced by ambient community diversity, in particular via predation. Here, we experimentally investigated whether parasite density and the presence of alternative prey can alter predation rates on free-living cercarial stages of a marine trematode by several non-host predators. All four predator species consumed increasing numbers of cercariae with an increase in cercarial density, indicating that the removal of cercariae by predators is effective over a range of natural densities as well as in the presence of alternative prey for a number of predators typical of marine ecosystems. However, the relative removal rates and the effects of cercarial density and alternative prey differed among predator species. In barnacles and shrimps, significant interactive effects of cercarial density and alternative prey on cercarial predation occurred while in oysters and crabs cercarial removal rates were unaffected by both factors. As changes in cercarial densities directly translate into changes in infection levels in down-stream hosts in this parasite–host system, the observed predator-specific responses suggest that cercarial predation effects on disease risks will depend on the specific species composition of ambient communities and not on non-host biodiversity per se.

A footpad assay was used to measure the DTH of mice to soluble worm antigens (SWAP), and to living day 7 lung schistosomula, following vaccination and challenge infections with Schistosoma mansoni. DTH to SWAP was first observed on day 10, and reached its maximum on day 17 post-vaccination. Treatment of mice with anti-CD4 antibody on the 3 days prior to footpad challenge completely abrogated this response. Reactivity to living parasites was of a lower order than that to SWAP; it also peaked earlier, on day 10 post-vaccination. By day 35, responsiveness to both sets of antigens had declined almost to control levels. There was no correlation between the level of DTH to living schistosomula, at any time, and the degree of resistance subsequently developed. Percutaneous challenge of vaccinated mice was followed by a resurgence of reactivity to SWAP. This secondary response occurred more rapidly than the primary response, peaking on day 7 post-challenge, and was of a similar magnitude. We were unable to detect a similar recall of DTH to living schistosomula, possibly because the assay was insufficiently sensitive. We conclude that the intensity and kinetics of DTH responsiveness are crucial features of the irradiated vaccine model, and suggest that further investigation of cell-mediated immune reactions, particularly those occurring in the lungs, is vital to a better understanding of events underlying the development and expression of immunity.