The major muscle systems of the metacercaria of the strigeid trematode, Apatemon cobitidis proterorhini have been examined using phalloidin as a site-specific probe for filamentous actin. Regional differences were evident in the organization of the body wall musculature of the forebody and hindbody, the former comprising outer circular, intermediate longitudinal and inner diagonal fibres, the latter having the inner diagonal fibres replaced with an extra layer of more widely spaced circular muscle. Three orientations of muscle fibres (equatorial, meridional, radial) were discernible in the oral sucker, acetabulum and paired lappets. Large longitudinal extensor and flexor muscles project into the hindbody where they connect to the body wall or end blindly. Innervation to the muscle systems of Apatemon was examined by immunocytochemistry, using antibodies to known myoactive substances: the flatworm FMRFamide-related neuropeptide (FaRP), GYIRFamide, and the biogenic amine, 5-hydroxytryptamine (5-HT). Strong immunostaining for both peptidergic and serotoninergic components was found in the central nervous system and confocal microscopic mapping of the distribution of these neuroactive substances revealed they occupied separate neuronal pathways. In the peripheral nervous system, GYIRFamide-immunoreactivity was extensive and, in particular, associated with the innervation of all attachment structures; serotoninergic fibres, on the other hand, were localized to the oral sucker and pharynx and to regions along the anterior margins of the forebody.

Although purely vertically transmitted parasites are predicted to cause low pathogenicity in their hosts, the effects of such parasites on host fitness under stressful environmental conditions have not previously been assessed. Here, we investigate the effects of Nosema granulosis, a vertically transmitted, microsporidian parasite of the brackish water amphipod Gammarus duebeni, on host growth and survival under conditions of host–host competition and limited food. The parasite had no effect on host survival, but caused a reduction in juvenile growth. Stressful environmental conditions also led to a reduction in G. duebeni growth. However, we found no evidence to support the prediction that parasitized hosts would suffer a greater reduction in fitness than uninfected hosts under adverse environmental conditions. We interpret our results in the context of selection for successful vertical parasite transmission.

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 biological parameters which generate seasonal fluctuations in the size of populations of Caryophyllaeus laticeps are examined in detail. A mathematical model is formulated to describe the dynamics of the adult parasite within the fish host Abramis brama, and the predictions of the model are compared with observed population data.

The seasonality of parasite population size is shown to be caused by the combined effects of a temperature dependent mortality rate and fluctuations in host feeding activity, which controls the immigration rate of larval parasites. The observed overdispersed distribution of adult parasite numbers within the host population is shown to be generated by variability in feeding habits between individual members of the fish population.

The theoretical population model is used as a framework for the investigation of, among other factors, the comparative influences of the immigration and death rates on the dynamics of the adult parasite, the future behaviour of the system under altered environmental conditions and the importance of chance effects in the dynamics of individual parasite populations within a single host.

The stability of the dynamics of the complete life-cycle of C. laticeps is discussed in relation to the inherent biological complexity of host/helminth parasite interactions.

Observations have been made on the distribution of faecal deposits on a number of small fields of varying size stocked with varying numbers of sheep. These studies were undertaken to examine certain hypotheses proposed in the construction of mathematical models for the distribution of strongyloid nematode infective larvae in pastures grazed by sheep.

The negative binomial distribution was found to provide a reasonable empirical description of the distribution of faeces, although there was evidence of departure from the negative binomial on the largest field.

Although, tentatively, the distributions were additive with respect to the number of sheep, there was evidence of departure from additivity in respect of field area and time. The implications of these findings for the model are discussed.

Significant positive correlations were found between successive time intervals in the number of faecal deposits present in individual subplots of the majority of fields. It is suggested that these arise from the tendency of sheep to use the same portion of a field for resting and rumination when heavy concentrations of faeces are deposited. The effects of this and other possible patterns of grazing and faecal deposition are discussed in relation to the intake of strongyloid infective larvae.

The average number of discrete deposits of faeces on pasture produced per sheep per day was greater in flocks producing faeces in pellet form than in flocks producing soft faecal masses. However, within faeces types, there was evidence that the expected number of deposits produced per sheep per day could reasonably be assumed constant.

The greater part of this work was carried out while one of us (A.D.D.) was the holder of a C.S.I.R.O. Overseas Research Studentship. For his advice and constructive criticism I am much indebted to Dr H. D. Crofton, under whose supervision this study was undertaken. My thanks go also to Professor J. E. Harris, C.B.E., F.R.S., for the provision of facilities in the Department of Zoology, and to Professor T. K. Ewer and Mr M. R. McCrea for their willing co-operation in the provision and handling of pastures and sheep at the School of Veterinary Science, Langford.

Mr David Culpin and Mrs Jean Williams, of the Division of Mathematical Statistics, were responsible for programming and organizing the calculations on the CDC 3200 Computer, and were consistently helpful in proposing and criticizing tests and procedures.

The results of ultrastructural studies and histochemical tests on the capsule of Trichinella spiralis are given. The capsule wall is shown to consist of two layers, an outer region of tightly compacted fibrils and an inner region of fibrils dispersed through matrix cytoplasm. Histochemical tests show the capsule wall to consist mainly of collagen and cystine. The appearance of the matrix, which is packed with mitochondria, rough endoplasmic reticulum, smooth reticulum and Golgi complexes, together with the histochemical reaction to the five enzymes tested, strongly suggests that the matrix is a region of high metabolic activity. Although there are several very large nuclei in the matrix there is no evidence of cell walls; consequently the matrix is a syncytium.

I wish to thank the A.R.C. for financial support while this work was carried out. I should also like to thank Dr D. L. Lee for his advice on many occasions and the late Professor Boyd of the Anatomy Department, University of Cambridge, for the use of the electron microscope in that Department.

Single percutaneous immunizations of Fischer rats with 1000 ultra-violet attenuated Schistosoma japonicum cercariae induced 52–88% resistance to challenge 4 weeks later. Increasing this to 3 immunizations induced 90% resistance to challenge, and this level of protection remained undiminished for up to 40 weeks after vaccination. Rats vaccinated with gamma-irradiated S. mansoni cercariae were resistant to challenge with S. mansoni but not S. japonicum. Similarly rats vaccinated with u.v.-attenuated S. japonicum cercariae were not resistant to heterologous challenge. Thus irradiated vaccines are species-specific in both permissive and non-permissive hosts.

Mice infected heavily with Schistosoma mansoni cercariae were treated 6 days later with Praziquantel and the parasites studied 1 h post-treatment. Immunofluorescence experiments showed that parasite surface antigens became available for labelling in larvae harvested from Praziquantel-treated mice, but not from untreated mice. Red blood cell antigens acquired from the host were localized on all lung worms studied. The distribution of each set of antigens, as revealed by fluorescence-labelling was, however, quite different. The lungs of heavily infected, drug-treated mice, exhibited severe haemorrhages which occurred in a dose-dependent manner. Fewer haemorrhages were found when heavily infected mice were treated simultaneously with Praziquantel and Aprotinin, a proteinase inhibitor. These results indicate that Praziquantel treatment in vivo induces the exposure of parasite antigens on lung-stage worms and may cause the release of parasite-derived enzymes which induce haemorrhages in the lung tissue of the host.

Six different histochemical techniques were employed to study the sites of deposition of glycogen, other carbohydrates, and carbohydrate complexes in uninfected Crassostrea virginica and those parasitized by the larvae of the trematode Bucephalus sp. The carbohydrate and carbohydrate complexes occurring in the parasites were also studied.

In uninfected oysters, glycogen is stored in the digestive diverticula, in Leydig cells located between the diverticula in the digestive gland, in the matrices of the palps, mantle, and gills, in walls of blood vessels, and in ova. There is a marked reduction of stored glycogen at these sites in infected oysters. In addition, the glycogen-storing diverticular cells and the interdiverticular Leydig cells are ruptured and/or lysed and the enclosed glycogen is expelled to the exterior.

Glycogen is found in the sporocysts; however, very little if any is present in cells comprising young germ balls. It is only after the elongate germ balls commence differentiating into cercariae that glycogen appears in their bodies.

In uninfected oysters, glucose deposits are present in the same Leydig cells in which stored glycogen is found. Glucose is believed to be the hexose from which the stored glycogen is synthesized. In infected oysters, the reduction of glucose in Leydig cells is almost complete.

There are histochemically demonstrable amounts of glucose in the blood vessels and sinuses of infected oysters while such is not the case in uninfected ones. This phenomenon is explained by the destruction of the sites of glycogen synthesis and storage in infected oysters, thus bringing about hyperglycaemia resulting from the accumulation of glucose taken in from the exterior.

The presence of glucose deposits adhering to the gill surfaces of infected oysters may represent the direct absorption of glucose from the environment and contribute to the hyperglycaemic conditions.

The absorption of glucose by sporocysts is suggested by the finding of this hexose adhering to the exterior and in the wall of certain sporocysts.

Gamma metachromatic globules are present in the digestive diverticula of uninfected oysters. Their number is increased in infected oysters. In addition, the connective tissue layers abutting the base of the epithelial lining of the stomach and intestine and the fibres at the base of the surface epithelium of the gills of uninfected and infected oysters are metachromatic. Metachromasia at these sites is believed to be due to acid mucopolysaccharides.

Acid mucopolysaccharides are present in certain cells intermingled among the ciliated epithelial lining of the gastric and intestinal walls and in secretory cells along the surface of the mantle, gills and palps. The histochemical reactions at these sites remain unaltered in infected oysters.

Only older sporocysts include acid mucopolysaccharides in the walls.

In older germ balls, acid mucopolysaccharides are present in the small somatic cells situated on the surface, beneath the enveloping membrane. These are believed to be cuticle-secreting cells.

In developing cercariae, acid mucopolysaccharides are found in the cuticle and certain parenchymal cells.

There is an increase in the number of ‘brown cells’ in infected oysters. The smallest and largest do not include acid mucopolysaccharides but those that measure between 0·006 and 0·012 mm are partially or totally positive for acid mucopolysaccharide. Slight metachromasia and sphingomyelins also are associated with certain ‘brown cells’ found in the digestive glands of infected oysters.

Large ‘brown cells’ in the intertubular spaces in the digestive glands of both uninfected and infected oysters have been observed to undergo division.

125I-Schistosoma mansoni schistosomulum surface antigens were immunoprecipitated with human antibodies from individual Egyptian patients diagnosed as being either acutely or chronically infected with S. mansoni. Both sets of patients were found to have IgG antibodies in their sera capable of immunoprecipitating the major Mr > 200, 38 and 32K antigens. However, the immunoprecipitation of the Mr 200K antigen was found to constitute a significantly greater proportion of the total precipitate achieved with acute sera than with chronic sera. The Mr 38 and 32K antigens were more variably precipitated by the acute sera than the chronic sera but the proportion of the total precipitation that these two antigens constituted was not found to be significantly different between the two sets of sera. Immunoprecipitation with pooled antibodies absorbed with egg and adult worm homogenates which had been treated to remove either carbohydrate or polypeptide epitopes demonstrated that the Mr > 200K antigen was the principal target of egg-cross-reactive anti-carbohydrate antibody amongst the antigens detected. The Mr 38 and 32K antigens were found to be precipitated by antibodies to protease-sensitive and periodate-insensitive polypeptide epitopes. These results are consistent with egg-cross-reactive anti-carbohydrate IgG antibody making a greater contribution to schistosomulum surface recognition in acute infection than in chronic infection. Indeed the presence of a higher level of egg-cross-reactive and anti-carbohydrate antibody directed against schistosomulum surface epitopes in an acute serum pool than in a chronic serum pool was confirmed by measurement of antibody binding to whole schistosomula.

The frequency distribution of parasites in hosts commonly follows a negative binomial or similar distribution. Under certain conditions the magnitude of parasite-associated host mortality can be estimated by comparing the tail of the observed distribution to that of the distribution predicted from the first few points of the data. For the technique to work the following assumptions need to be met: mortality in lightly infected fish must be rare; infection and consequent mortality occur only in fish younger than those sampled; and the frequency distribution of the parasite at the time of infection should conform to a known probability distribution. The method was applied to frequency distributions of blastocysts of Callitetra rhynchus gracilis in 898 Saurida tumbil (Bloch) and 5013 S. undosquamis (Richardson). Parasite-associated mortality in S. tumbil was calculated to be at least 11 % in males and 2% in females. For S. undosquamis, estimated mortality was about 5% in males and 3% in females. The numbers of parasites estimated to produce a 0·5 probability of death, the parasitological equivalent of an LD50 were 3·4 and 5·7 for S. tumbil males and females, and 18 and 3 for S. undosquamis males and females respectively.

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.

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.

An in vitro investigation has been made of the relative roles of the gut and tegument in the absorption of the neutral amino acids L-alanine and L-leucine by a marine fish-gill parasite, Diclidophora merlangi. The use of ligatures to preclude oral ingestion of trace-labelled medium has proved inadequate, invariably damaging the tegument, as revealed by stereoscan electron microscopy, and resulting in artifactual levels of absorption. Three alternative procedures have given consistently reliable data on the route of entry of low molecular weight substrates. (1) Ultrastructural examination of worms previously incubated in electron-dense cationic tracers has shown that, in vitro, there is no oral intake of sea water. (2) The suspending of worms in trace-labelled medium with the mouth out of the medium and comparing amino acid uptake with that of worms totally immersed in medium has revealed no statistically significant difference in the absorption levels. (3) Application of section (freeze-dried) auto-radiography to detect diffusible isotope has demonstrated directly transtegumental absorption of a neutral amino acid. It is concluded from these experiments that Diclidophora has a tegumental transport system for absorbing certain neutral amino acids, and whilst, clearly, the worm is sanguinivorous and digests blood in a well-developed gut, it may also be capable of supplementing this diet with low molecular weight organic nutrient absorbed directly from sea water via the tegument.

Interleukin (IL)-13-associated signal pathway plays an important role in schistosomiasis hepatic fibrosis. In this study we tried to investigate the effects of corilagin to ameliorate schistosomiasis hepatic fibrosis through regulating IL-13-associated signal pathway in vitro and in vivo. Cellular model was set up with hepatic stellate cells-T6 cells stimulated by rIL-13 and male Balb/c mice were infected with Schistosoma japonicum cercariaeas as animal model. Liver histological changes were observed with haematoxylin and eosin staining. Masson staining was employed to observe the change of egg granulomas. Expression of Col (collagen) and Col III were examined with Immunohistochemistry. Western bolt was employed to detect the JAK-1 and IL13Rα1 proteins. The mRNA expression of Col I, Col III, IL-13, JAK-1 and IL13Rα1 were tested by quantitative polymerase chain reaction. As a result, less inflammatory changes were found in all corilagin groups compared with model group and praziquantel group. The mRNA levels of Col I, Col III, IL-13, JAK-1 and IL13Rα1 were significantly decreased after corilagin intervention (P < 0·01). JAK-1 and IL-13Rα1 protein levels were also greatly decreased in the corilagin groups (P < 0·01). In conclusion, corilagin could ameliorate schistosomiasis hepatic fibrosis by down-regulating the expression of IL-13 and signal molecules in IL-13 pathway.

Immunity to Hymenolepis nana was adoptively transferred to recipient mice of 4 strains using mesenteric lymph node cells (MLNC), spleen cells (SC), and/or serum taken from infected donor mice. Donor cells capable of transferring immunity appeared in the mesenteric lymph nodes and spleen at an early stage (5 days) after infection. Immunity was most effectively transferred with MLNC and immune serum did not enhance this effect. It is suggested that effective immunity to H. nana involves both antibody and T cell-mediated inflammatory events.

Evidence for the existence of 2 first intermediate host-specific sibling species of the 45 collar-spined echinostome Echinoparyphium recurvatum is presented. Experimental studies on their life-cycles were carried out under controlled laboratory conditions. The two entities were found to be morphologically indistinguishable in all major respects, yet they exhibited distinct biological characteristics. One of the sibling species utilizes the freshwater lymnaeid pulmonate snail Lymnaea peregra as first intermediate host, and the adults occur in the anterior small intestine of the wildfowl experimental definitive host Anas platyrhynchos. The other utilizes the freshwater mesogastropod prosobranch snail Valvata piscinalis as first intermediate host, and the adults occur in the posterior small intestine and rectum of A. platyrhynchos. The existence of the two sibling species in sympatry may be explained by the fact that the life-cycles of the two forms represent two distinct cycles of transmission serving to reduce excessive competition between them.

A technique is described for the recovery of infective larvae of strongyloid nematodes from sediment resulting from the washing of pasture and soil samples. The process of recovery and counting of larvae is described by a model based on the binomial distribution. Tests of the technique have shown that it will recover approximately 50% of the larvae present in samples of pasture sediment of either 7·5 or 12·5 ml in volume after centrifugation. The efficiency of the technique was independent of the number of larvae present in samples of pasture sediment. The technique was shown to be less efficient and more variable in recovery of larvae from samples of soil sediment. Estimations in efficiency of recovery from soil sediment ranged from 64 to 110·2% and a significant effect of volume of sediment on recovery was detected.

Extensive insecticide use has led to the resistance of mosquitoes to these insecticides, posing a major barrier to mosquito control. Previous Solexa high-throughput sequencing of Culex pipiens pallens in the laboratory has revealed that the abundance of a novel microRNA (miRNA), miR-13664, was higher in a deltamethrin-sensitive (DS) strain than a deltamethrin-resistant (DR) strain. Real-time quantitative PCR revealed that the miR-13664 transcript level was lower in the DR strain than in the DS strain. MiR-13664 oversupply in the DR strain increased the susceptibility of these mosquitoes to deltamethrin, whereas inhibition of miR-13664 made the DS strain more resistant to deltamethrin. Results of bioinformatic analysis, quantitative reverse-transcriptase polymerase chain reaction, luciferase assay and miR mimic/inhibitor microinjection revealed CpCYP314A1 to be a target of miR-13664. In addition, downregulation of CpCYP314A1 expression in the DR strain reduced the resistance of mosquitoes to deltamethrin. Taken together, our results indicate that miR-13664 could regulate deltamethrin resistance by interacting with CpCYP314A1, providing new insights into mosquito resistance mechanisms.