The humoral immune response in the two eel species, Anguilla japonica and Anguilla anguilla against two fractions of antigens in Anguillicola crassus were studied.Within species, both eel species showed significantly elevated titres compared with controls when immunized with antigens from Anguillicola crassus.In interspecific comparison, Anguilla japonicashowed significantly elevated titres in comparison with Anguilla anguilla. Immunization of Anguilla anguillacaused a significantly decrease in the plasma levels of protein in comparison with control fish and all groups of Anguilla japonica. In contrast, Anguilla japonica showed significantly lower plasma levels of Ig in all groups compared with Anguilla anguilla.The different susceptibilities to Anguillicola crassus between the natural host, Anguilla japonica, and the naı¨ve, Anguilla anguilla, is partly due to differences in the ability of the two eel species to mount a humoral immune response.

Comparative morphometric and morphological studies of microfilariae and infective stages were undertaken in nocturnally periodic and subperiodic Wuchereria bancrofti. For microfilariae, the body dimensions of nocturnally periodic (NP) were significantly smaller than nocturnally subperiodic (NSP), i.e. body length 268.03 ± 14.75 μm (NP), 307.61 ± 11.52 μm (NSP); cephalic space length 4.21 ± 0.62 μm (NP), 5.32 ± 0.79 μm (NSP); head to nerve ring 49.39 ± 5.43 μm (NP), 57.40 ± 4.46 μm (NSP); innenkörper length 33.05 ± 5.89 μm (NP), 44.02 ± 8.71 μm (NSP); cephalic space width 4.28 ± 0.59 μm (NP), 6.04 ± 0.68 μm (NSP); body width at nerve ring 5.01 ± 0.57 μm (NP), 7.45 ± 0.75 μm (NSP). The number of nuclei between the cephalic space and nerve ring of NP (66.67 ± 5.19) was also significantly less than in NSP (94.74 ± 6.95). For infective stages, the body dimensions of NP were significantly smaller than NSP, i.e. body length 1632.50 ± 131.48 μm (NP), 2002.63 ± 222.60 μm (NSP); head to nerve ring 103.09 ± 7.47 μm (NP), 122.44 ± 9.62 μm (NSP); head to oesophago-intestinal junction 567.69 ± 94.84 μm (NP), 666.75 ± 110.08 μm (NSP); body width at oesophago-intestinal junction 23.15 ± 1.55 μm (NP), 26.78 ± 1.62 μm (NSP). It is too early to infer the NP type as an additional sibling species of W. bancrofti but it is reasonable to treat it as a new variety and additional work is needed to clarify its status.

Seventy female lambs (6–7 months old) which were exposed to natural infections of Haemonchus contortus were designated as responders or non-responders on the basis of 10 weekly cumulative faecal egg counts. Selected responder and non-responder lambs were treated with ivermectin, housed separately and 6 weeks post-housing, seven lambs from each group were given a trickle infection of Haemonchus contortus at 1000 L3 daily for 5 days per week up to 2 weeks and examined weekly for 10 weeks after first infection. Analysis of data revealed significantly lower mean faecal egg counts and non-significantly less weight loss in responder than non-responder lambs. Mean values of haemoglobin, packed cell volume, total serum protein and peripheral eosinophil counts were significantly higher in responders than non-responders. In contrast, serum pepsinogen concentration was significantly less in responders than in non-responders. At 10 weeks post-infection, there were fewer pathological lesions and significantly lower worm burdens in responders than in non-responders. These results demonstrate a distinct resistance in responders to Haemonchus contortus infection.

Scanning electron microscopy (SEM) was used to study the collar region of Deropristis inflata (Molin, 1858), an intestinal digenean of fish, and Echinostoma revolutum (Froelich, 1802), an intestinal digenean of birds. The results showed basic differences in the following morphological features. The collar of D. inflata was open ventrally and dorsally whereas that of E. revolutum was closed dorsally and ventrally, forming a kidney-like ring. The collar of D. inflata was located posterior to the oral sucker, some distance behind the anterior end of the body. That of E. revolutum was located terminally around the oral sucker. The collar of D. inflata had numerous collar spines which varied in size, shape and position. That of E. revolutum had 37 collar-spines, mainly homogenous in their general morphology and with a typical arrangement pattern for 37-collar-spined echinostomes. The collar of D. inflata had few tegumentary papillae whereas that of E. revolutum had abundant papillae. A ventral depressed area occurred in D. inflata, between the acetabulum and oral sucker, dividing the collar into two left and right independent parts. The ventral depression in E. revolutum extended from the ventral sucker to the posterior end of the collar, and was not divided. In D. inflata, tegumentary spines were located on the oral sucker, and the collar was posterior to the sucker. In E. revolutum, the oral sucker and the collar lacked tegumentary spines. The region immediately posterior to the collar also lacked spines in E. revolutum. The collar pattern of D. inflata is undoubtedly more primitive than that of E. revolutum.

The potential influence of second intermediate host species on the infectivity of metacercarial cysts of Echinoparyphium recurvatum to the definitive host Anas platyrhynchos was examined experimentally. Echinoparyphium recurvatum metacercarial cysts were obtained from the following experimentally infected second intermediate hosts 14 days post expsoure to cercariae: Lymnaea peregra; Physa fontinalis; L. stagnalis; Planorbis planorbis; Biomphalaria glabrata; tadpoles of the amphibian Rana temporaria. Metacercarial cysts from each of these hosts were fed, in doses of 50 cysts per individual, to separate groups composed of between four and eight, 3-day-old A. platyrhynchos ducklings. All A. platyrhynchos were necropsied 15 days post-infection and the number, size, and reproductive status of E. recurvatum worms in the intestine was recorded. Analyses of variance on the number (transformed log (x + 1)) and size of worms revealed no significant differences in worms originating from metacercariae formed in the different second intermediate hosts (worm number P > 0.05, and worm size P > 0.05). All worms recovered were found to be gravid. It is therefore concluded that the species of second intermediate host utilized does not influence the infectivity of the metacercarial cyst of E. recurvatum, nor the subsequent establishment and reproductive status of the parasite in A. platyrhynchos.

Photoperiodic emergence patterns of the cercariae of two digeneans, Echinoparyphium recurvatum (Echinostomatidae) and Plagiorchissp. (Plagiorchiidae), were studied experimentally using a photoperiodic regime of 12 h light: 12 h dark at a constant 18°C. In single species infections of the first intermediate host snail Lymnaea peregra, the cercariae of E. recurvatum emerged exclusively during the light phase and those of Plagiorchis sp. emerged exclusively during the dark phase. In double infections, each species retained its own discrete photoperiodic emergence pattern. This result demonstrates the absence of interference between the mechanisms responsible for the photoperiodic emergence pattern of each species. A degree of interference between the two parasites in double infections of L. peregra was evident. The presence of E. recurvatum significantly reduced the number of Plagiorchis sp. cercariae emerging in a 24 h period and also delayed the mean peak emergence time of Plagiorchissp. cercariae by 2 h. This result is consistent with the well documented antagonistic effect that the redial stages of echinostomes are known to have against the sporocysts of other digeneans within the same host mollusc.

Results are presented of 90 children aged 1–15 years hospitalized with toxocariasis. Blood count analysis and laboratory examination were done by routine clinical laboratory methods. Anti-Toxocara antibodies were detected in the serum of patients using an ELISA method. Demographic analysis of the children's families exposed to the risk of disease allowed estimation of age-specific rates for clinical toxocariasis. The probability of toxocaral infection and the intensity of its clinical manifestations in children are determined by the epidemiology of this zoonosis and by the risk factors in the family. The presence of high titres of specific IgG antibodies in all age categories correlates with the clinical manifestations of toxocariasis. The highest admission rate is in the age categories of 3–5 years (43.3%) and 6–10 years (36.7%). Laboratory findings show that the most conspicuous changes occur in the age category 1–5 years. The high percentage of seropositive dog-keeping and puppy-breeding families and the possibility of infection with repeated doses of larvae stimulate eosinophilia, which prevails in children under the age of five years. We present the percentage of patients whose parameters showed deviations from the reference values for a particular age category. Analyses of laboratory indices and of clinical manifestations will contribute to the accuracy of diagnosis and effectiveness of treatment of this disease.

A total of 120 muscle tissues from three horses naturally infected with Trichinella spiralis were examined. The head was the most infected site. In particular, the muscles harbouring the highest number of larvae were: musculus buccinator (12, 411 and 1183 larvae g-1), the tongue (11, 615 and 1749 larvae g-1), m. levator labii maxillaris (17, 582 and 1676 larvae g-1), and the masseter (4.9, 289 and 821 larvae g-1). Compared with the diaphragm, the number of larvae per gram was from 3.5 to 6.8 times higher in the tongue, from 3.5 to 6.5 higher in m. levator labii maxillaris, and from 2.5 to 4.6 higher in m. buccinator. Of the examined muscles, the diaphragm had from the 6th to the 15th highest level of infection (3.1, 166 and 256 larvae g-1). Published data from experimentally infected horses confirm these results, suggesting that efforts to detect predilection sites should focus on the head muscles.

Phototactic responses of cercariae of the echinostome Echinoparyphium recurvatum (Digenea: Echinostomatidae) were investigated during phases of sub-maximal and maximal infectivity using a simple light/dark choice chamber. The phototactic responses of a total of 400 cercariae were examined in 20 replicate experiments during their sub-maxinal infectivity dispersal phase (0.5 h post-emergence from the first intermediate host Lymnaea peregra) and during their maximal infectivity phase (2.5 h post-emergence). Cercariae in the sub-maximal infectivity dispersal phase were found to be positively phototactic, significantly larger numbers of them occurring on the light side of a light/dark choice chamber P < 0.001. Cercariae in the maximal infectivity phase were found to be negatively phototactic, significantly larger numbers of them being found on the dark side of the choice chamber, P < 0.001. This report of ‘phototactic switching’ demonstrated by the cercariae of E. recurvatum from a positively phototactic dispersal phase to a negatively phototactic infection phase constitutes the first record of such behaviour in the cercaria of an echinostome.

Light, scanning, and transmission electron microscopy were employed to provide further data on the putative origins of the immunogenic secretory–excretory product (ESP) of Strongylus vulgaris (Looss 1900). The sharply delineated but superficial attachment to the equine caecum by the mouth leaves behind an oval area devoid of epithelial cells. Attachment does not extend deeply enough to reach the muscularis mucosa layer of the equine intestine. The progressive digestion of the ingested plug of tissue (epithelial cells, blood cells and mucous) was visualized. The coelomocytes, floating cells and membranous structures located in the pseudocoelom and intimately associated with the digestive, excretory and reproductive systems, and with the somatic muscles are described. The secretory–excretory system comprises two, ventrally-located, secretory–excretory glands connected to tubular elements. These glands synthesize granules of various sizes and densities that are delineated.

Young adults of Echinostoma trivolvis and E. paraensei were recovered from hamsters previously infected with metacercarial cysts. Some worms of each species were exposed for 1 h to 3-H-tyrosine to label sperm and transplanted singly to uninfected hamsters with several unlabelled worms of the same or opposite species or both species. After 5 days, recovered worms were processed for paraffin sectioning and autoradiography. The resulting slides were observed for the location of radioactive sperm in the seminal receptacles of donor (labelled) and recipient (unlabelled) worms. When E. trivolvis was the donor with the recipient E. paraensei, self-insemination took place, but only one interspecies mating occurred out of 72 possible recipient worms. When E. paraensei served as the donor, self-insemination again occurred, but no cross-insemination was observed among the 59 E. trivolvis recipient worms. When single donor worms had a choice of either species of recipient worms, no interspecies mating took place, but both self- and cross-insemination occurred in the normal, unrestricted behaviour found in single species mating studies. Rates of both self- and cross-insemination were higher in concurrent infections of both recipient species than in single species mating studies. After transplant, both species localized in their natural habitat within the small intestine, with 1/3 overlapping in the duodenum, making interspecies mating a possibility. The correlation between mating and electrophoretic studies on the genetic relationship between 37-collar-spined echinostomes is discussed.

The aim of this study was to determine if the plerocercoid larvae of Gymnorhynchus gigas, a common cestode of the ray’s bream (Brama raii), possess antigenic compounds potentially capable of provoking anaphylactic episodes. A murine experimental model, using BALB/c mice, was developed to study the humoral immune response induced by G. gigas extracts. A highly specific humoral immune response was detected and cross-reactions were not observed between parasite and host antigens. The presence of IgM and IgG3 levels suggest the presence of thymus-independent antigens in the parasitic extract. The IgG antibody class showed the highest levels, with the IgG1 the predominant subclass. These IgG1 levels are in accordance with the supposed presence of a type I allergic reaction after the ingestion of G. gigas plerocercoids parasitizing fish, as well as inducing anaphylaxia in fish. These results indicate that somatic products released from ingested larvae of G. gigas could induce the development of a Th2 response capable of causing allergic disorders.

The in vitro nematocide activity of seventeen 6,7-diarylpteridines has been tested using three different experimental models, Caenorhabditis elegans, Nippostrongylus brasiliensis and Heligmosomoides polygyrus. The method of evaluation of inhibition in the secretion of acetylcholinesterase by H. polygyrus seems to be the most indicated to avoid false positives. The in vivo activities, against Trichinella spiralis, of the most in vitro active pteridines have been assayed. All pteridine derivatives bearing 6,7-di-p-bromophenyl substituents have shown in vitronematocide activites in the three experimental models used. Amongst all the pteridines tested in vivo, only 2,4-pteridinedithione derivatives exhibited moderate activity.

Carbon-13 decoupled 1H spin echo NMR spectroscopy, with and without population inversion, was used to study carbon flow between the host, Meriones unguiculatus, and the parasite, Echinococcus multilocularis. This was accomplished by monitoring [2-13C]acetate metabolism in the liver of jirds infected with metacestodes of this parasite. Thirty minutes after injection of labelled acetate solution into the portal vein, 13C enrichment was observed in hepatic acetate, β–hydroxybutyrate, succinate, alanine, lactate and glucose. For E. multilocularis cysts, at this time,13C enrichment was observed in the same metabolites as in livers and, in addition, citrate. At 120 min there was a significant decrease in the amount of label present in all hepatic metabolites whereas more label was found in the majority of the parasite metabolites. The results confirm that exogenous acetate, through randomization of the 13C in biochemical pathways of host liver, ends up in hepatic glucose. As this biosynthetic route is not available to the parasite, the presence of 13C enriched glucose in the cysts clearly indicates that the parasite is siphoning off glucose that is newly synthesized by the host. At 120 min some of this labelled glucose was stored in parasite glycogen whereas some of it had been catabolized to succinate, alanine, lactate and acetate, end products which are excreted back into the host.

The surface topography and ultrastructural changes of Schistosoma mansoni worms developed from ultraviolet-irradiated cercariae were compared with those from non-irradiated cercariae. The tegument of worms developed from irradiated cercariae showed a variety of changes including the occurrence of oedemata and most of the tubercles being torn at the tip and having lost their spines on the dorsal surface of some male worms. In females, parts of the tegument were devoid of spines and surface lesions were present. The range and extent of these changes differed not only among individual worms but also between different regions of individual worms resulting in generalized deformities in those worms originating from irradiated cercariae.

Populations of Pasteuria penetrans isolated from root-knot nematodes (Meloidogyne spp.) and cyst nematodes (Heterodera spp.) were tested for their ability to adhere to a limited selection of sheathed and exsheathed animal parasitic nematodes, free living nematodes, including Caenorhabditis elegans wild type and several srf mutants, and plant parasitic nematodes. The attachment of spores of Pasteuria was restricted and no spores were observed adhering to any of the animal parasitic nematodes either with or without their sheath or to any of the free living nematodes including C. elegans and the srf mutants. All spore attachment was restricted to plant parasitic nematodes; however, spores isolated from cyst nematodes showed the ability to adhere to other genera of plant parasitic nematodes which was not the case with spores isolated from root-knot nematodes. The results are discussed in relationship to cuticular heterogeneity.

The cytotaxonomical characteristics of parthenitae of Apatemon gracilis (Rudolphi, 1819) Szidat, 1928 were studied using karyometric analysis to extend our knowledge of chromosome morphology and karyosystematics among trematodes. The karyotype, reported here for the first time, consists of ten pairs (2n = 20) of chromosomes divided into two size groups: five pairs of comparatively large and five pairs of small chromosomes. Biarmed chromosomes prevail in the chromosome set. According to centromere index values, chromosome 1 is submetacentric to metacentric, 2 is subtelocentric, 3 and 5 are acrocentric, 4, 9 and 10 are metacentric, 6 is submetacentric and 7 and 8 are submeta-subtelocentric. The small uniarmed B-chromosome was found in the chromosome set of parthenitae of A. gracilis from one snail. Data are discussed with reference to the karyotypes previously described within the Strigeidae.

The muscular distribution of Trichinella spiralis or T. britovi was studied by digestion in 59 experimentally infected pigs and seven wild boars. Crus muscle was the predilection site in 89.3% of 28 heavily infected swine with 146–3634 larvae per gram (lpg), but in 51.6% of middle to light infections (0.005–59 lpg) the basis of the tongue showed higher larval densities than the crus muscle. The basis of the tongue was also the predilection site in 71.4% of wild boars. Highest counts in other muscles were found only in lightly infected pigs. The influence of intensity of infection, host species, and Trichinella species on muscle distribution is discussed.

The effect of transportation and confinement stress on Dicrocoelium dendriticum egg production was investigated. Sheep passing a minimum of 200 eggs g-1 of faeces were selected from a naturally infected flock. A group of six ewes (group A) was transferred to the laboratory premises and kept indoors for 28 days, while another group (B) of six ewes remained on pasture and was used as a control. Faecal examinations and egg counting were performed weekly, on all sheep, from one week before to 28 days after the transportation of the animals. Comparison of faecal egg counts between groups revealed higher (P < 0.01) counts in transported sheep sampled on days 7, 14 and 28 of the trial. Furthermore, egg counts obtained from sheep that were transferred remained consistently high while the ones from sheep that remained on pasture showed significant variation. Therefore, it is concluded that stress-inducing factors, such as transportation and confinement may enhance egg production of D. dendriticum.

The viability of metacercariae of Fasciola gigantica was tested by in vitro and in vivo methods. In vitro testing was based upon the motility of juvenile flukes within the inner cyst as examined under the light microscope. In vivo testing was undertaken through experimental infections of rabbits (two groups) and natural definitive hosts, lambs (one group). In the first group, out of six rabbits each given 25 metacercariae, worm establishment only took place in one rabbit with a single fluke recovery on 60 days post infection. In the second group of six rabbits each given 200 metacercariae, five were infected, with two or three flukes per host. All the lambs given 250 metacercariae became infected showing prevalences of 7.2–40% in comparison with rabbits in which low prevalences (0–4%) were recorded. The results indicated that even viable metacercariae which were already tested in vitro could not readily establish in rabbits. Such variability in worm establishment suggests that immunological and chemotherapeutic studies in rabbits infected with F. gigantica are likely to be unreliable.