The structure of the digestive tract of Euclinostomum multicaecum (Digenea: Euclinostomatidae) is unusual, comprising several main lateral caeca which extend posteriorly and further divide, giving rise to numerous smaller branches which are widely distributed throughout the fluke. These multicaeca presumably promote nutrient absorption during rapid and prolonged feeding directly following excystment. The caecal wall consists of a syncytial gastrodermal epithelium, bearing loop-like lamellae which extend into the lumen and enclose spherical inclusion bodies and presumably also, increase the absorptive surface area. There was no evidence of endo- or exocytosis, nor were lysosomes, phagosomes or residual bodies observed. The gut caeca are supported by a fibrous basal lamina and an underlying layer of muscle fibres, while parenchymal cells occupy much of the extracellular space. The protonephridial system resembles that observed in other digeneans consisting of flame cells and collecting ducts which join to form a bladder that opens externally through a single excretory pore. The syncytial epithelium of the collecting ducts is elevated by numerous lamellae while the basal lamina is highly infolded. The luminal contents of these ducts comprise bar-shaped crystalline structures, lipid droplets and electron-dense inclusion bodies. The excretory system is supported by a network of muscle fibres and parenchymal cells.

Adult Strongylus vulgaris, collected from the caecum of infected horses and embedded in paraplast using standard methods, were sectioned for immunohistochemistry (IHC) studies. Antibodies were raised in rabbit against the excretory–secretory product (ESP) and against two constituent protein bands (28–30 kDa). The use of sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE), enzyme-linked immunosorbent assay (ELISA) and immunoblotting indicated the immunogenicity of ESP and of the subunits (28–30 kDa). In ELISA, both rabbit hyperimmune sera recognized the ESP and (28–30 kDa) bands consistently and strongly. Both hyperimmune sera recognized most ESP subunits (80, 60, 54, 42, 35, 30, 20 and 15 kDa) in immunoblots. IHC, using light microscopy, suggested that the following worm tissues reacted strongly and positively with both antisera: amphids, tooth core, intestine, excretory gland and ducts, and hypodermis. Thus, either these are antigen-producing tissues, or antigens sharing common epitopes occur in them. The following tissues reacted weakly: body cuticle, buccal capsule cuticle, oesophagus, and also somatic muscle (non-contractile portion) perhaps due to diffusion of antigen from adjacent tissues. Preimmune serum gave a negative reaction with most worm tissues.

The distribution of two acanthocephalan species (Pomphorhynchus laevis and Acanthocephalus anguillae) in the chub (Leuciscus cephalus) was studied in foriver reaches characterized by different levels of pollution: the River Ticino ne Abbiategrasso (unpolluted), the Naviglio Grande Canal, in Milano (slightly polluted), the River Lambro near Merone village (polluted) and the Riv Lambro near Monza (severely polluted).

Pomphorhynchus laevis was restricted to the unpolluted and the slight polluted sites, while the intensity of A. anguillae increased proportionally water pollution. These differences were partially explained by the variation in abundance of their intermediate hosts (Echinogammarus stammeri for P. lavis and Asellus aquaticus for A. anguillae). Data on the occurrence of P. laevis at A. anguillae showed a significant negative binomial frequency distributic suggesting their tendency to be aggregated within the host populations L. cephalus.

Experimental infection of larval Echinococcus multilocularis in the rodent brain was attempted to establish a murine model for cerebral alveolar echinococcosis. Balb/c mice and jirds were injected intracranially with 10% of a homogenated hydatid cyst mass. Small cystic larvae were observed macroscopically in the cranial cavity 1, 2 and 5 months post-infection in both mice and jirds. Some larval cysts from both rodents contained mature or immature protoscoleces. In mice, the laminated layer was found in the lateral ventricle 2 months post-infection but without protoscoleces. At five months post-infection, larger larval cysts were found in the cranial cavity of a mouse, which also demonstrated partial palsy of the legs. A laminated layer with mature protoscoleces was observed in the third ventricle and the mouse also harboured, in the left lung, a larval cyst containing protoscoleces surrounded by lymphocytes. Jirds were also found to be infected with metacestodes in the cranial cavity, but neither unusual behaviour nor establishment of cysts inside the brain was observed in jirds during the course of infection.

Taxonomic characters of the male posterior end and the body cuticle of Euchordodes nigromaculatus (Nematomorpha) were described by scanning electron microscopy (SEM) and compared with the original description by Poinar (1991a) and with other Euchordodes species. Intraspecific variation was found in the body length, the distance between the cloacal opening and the posterior end and especially in the form of the male posterior end. The latter either possesses two short lobelike structures and a ventral groove or lacks these structures. The importance of SEM investigations and observations of intraspecific variation is stressed for the taxonomy of nematomorph species.

Early studies by light microscopy provided preliminary data on the fine structure of Strongylus vulgaris (Looss 1900). The present study employed transmission electron microscopy to investigate particular structures in the buccal capsule especially the dorsal gutter (DG) and teeth. The DG is a tube containing the terminal duct of the dorsal oesophageal gland (DOG) surrounded by two concentric canals. Putative pores indicated in the wall of the DG seen in other studies are revealed as honey-combed, fibrous, structures on each side of the ventral lamella. This lamella is formed by the wall of the DG internal canal running the length of the DG. Secretions of the DG canals are released through the dorsal gutter duct (DGD) which passes through the teeth bases at the base of the buccal capsule. Teeth have a vesicular cytoplasmic core containing various organelles.

Echinococcus granulosus is widely distributed throughout Iran, where a variety of animals act as intermediate hosts. In this study, the development and morphological characteristics of E. granulosus of sheep, cattle and camel origin were compared and, overall, the characteristics of larval and adult isolates from sheep and cattle, although similar, showed significant differences from those of the camel isolates, especially with respect to the size of rostellar hooks. Differences in the fertility rates of hydatid cyst in sheep, cattle and camel were recorded as 88%, 19% and 70% respectively.

In dogs experimentally infected with the three ‘strains’ of E. granulosus, the rate of development was more rapid in the camel than in the sheep and cattle ‘strain’. In addition, adult E. granulosus derived from the camel demonstrate differences in worm length, segmentation and size, shape, number and arrangement of the genitalia when compared with worms derived from sheep and cattle. The epidemiological significance of these findings is discussed in relation to human hydatid infections in Iran.

Metacercariae of Plagiorchis muris, obtained from naturally infected dragonflies, Sympetrum eroticum, successfully established in 4-week-old albino rats up to 14 days post-infection (p.i.) but by day 28 p.i. the recovery rate had significantly decreased. The genital primordia in excysted metacercariae were differentiated into those of metraterm, Mehlis' gland, ovary and cirrus pouch, with the primordial testes appearing on day 1 p.i. The vitellaria and eggs in the uterus were present in flukes on days 2 and 4 p.i., respectively. Mature flukes were established in the lower part of the small intestine on day 5 p.i., with the peak of egg production occurring on day 14 p.i. Growth of the flukes continued up to day 28 p.i.

This study investigates the use of texture, i.e. the grey level variation in digital images, as a basis for identification of strongylid eggs. Texture features were defined by algorithms applied to digital images of eggs from the bovine parasitic nematodes, Ostertagia ostertagi, Cooperia oncophora, and Oesophagostotnum radiatum. The resulting data served to establish classification criteria by linear discrimination analysis, and the criteria were subsequently evaluated by crossvalidations. From 25 texture features, ten features were selected by their significant discriminatory powers. Using a classification criterion based on these ten texture features, an average of 91.2% of eggs from the three species were correctly classified. All O. radiatum eggs were correctly classified, 11.8% of O. ostertagi and C. oncophora were reciprocally misclassified, and 2.9% of O. ostertagi were identified as O. radiatum. When the ten texture features were used singly an average of 51.2 to 37.9% of the species could be classified correctly. When texture was used together with the shape and size features, a higher percentage of eggs were correctly classified compared with the classification based on either texture, or shape and size. Hence, all O. radiatum were correctly classified as well as 88.3% of O. ostertagi and 91.2% of C. oncophora, resulting in an average of 93.1% correctly classified eggs. The rapid and accurate measurements of texture features may serve as a basis for identification or enhance performance of classification criteria based on egg shape/size.

A single oral dose of an aqueous suspension containing 11,350,000 chlamydospores of a Mexican isolate of Duddingtonia flagrans (FTHO-8) given to sheep, resulted in a maximum reduction of 88% (range 86.7–90.4%) of the population of Haemonchus contortus infective larvae in the faeces. The effect of this treatment continued for 4–5 days after administration of the suspension. The possible use of this treatment as a method of control of ovine haemonchosis is discussed.

The ultrastructure of the cuticle of infective juveniles (IJs) of Steinernema carpocapsae (newly emerged and 80-day-old) and newly emerged IJs of S. riobravis, S. feltiae and S. glaseri was examined using transmission electron microscopy. The thickness of four distinctive layers of the cuticle was measured: epicuticle, cortical and median layer, striated layer and fibrous mat. The thickness of the cuticle was correlated with the size of the IJ. In the case of newly emerged IJs, the smallest species, S. carpocapsae, had a cuticle thickness of c. 270 nm compared with c. 460 nm for S. glaseri, the largest of the four species. The overall thickness of the cuticle or the thickness of the cuticle layers was not correlated with the ability of the IJs of the four species to survive desiccation per se. The major difference between newly emerged IJs of the four species was that S. carpocapsae had a proportionately thicker striated layer compared with the other three species. The significance of this is not known but it may be an adaptation involving the nictation behaviour of this species. A substantial change was observed in the cuticle of aged (80-day-old) IJs of S. carpocapsae, whereby the thickness of the cortical and median layer increased by more than 100% and the overall thickness of the cuticle increased by about 50%. Two possible explanations for this increase are: (i) new material was synthesized; or (ii) the fluid content of this layer increased due to an increase in the permeability of the outer layers of the cuticle. The ultrastructure of the sheaths of S. feltiae and S. glaseri was also examined and, apart from S. glaseri having a thicker sheath, the structure of the sheath in both species was similar, with the epicuticle and striated layer still visible.

Most carcinogens and xenobiotics are metabolized primarily by the mixed function oxidase system which includes cytochrome P450, cytochrome b5, NADPH-cytochrome c reductase and aryl hydrocarbon [benzo(a)pyrene] hydroxylase. The present study investigates the influence of infection with different levels of Schistosorna mansoni cercariae on the hepatic levels of reduced glutathione, glutathione S-transferase and glutathione reductase in addition to the enzymes of mixed function oxidase. Cercariae infection levels of 60, 120, 180, 300 and 600 per mouse increased: (i) the hepatic content of cytochrome P450 by 27%, 38%, 72%, 57%, 48% respectively; (ii) the aryl hydrocarbon hydroxylase activity by 44%, 64%, 76%, 90%, 51% respectively; and (iii) the hepatic level of reduced glutathione by 67%, 83%, 103%, 60%, 38% respectively. The cytochrome b5 content did not change at the lowest level of infection but increased at the other four levels by 45%, 76%, 49% and 38% respectively. The activity of glutathione S-transferase increased at the first three levels by 42%, 40%, 27% respectively and decreased at the last two levels by 28% and 52% respectively. On the other hand, the activity of glutathione reductase did not change at any level, whereas, NADPH-cytochrome c reductase activity decreased at the last two levels by 44% and 54%. The alterations in the activities of phase I & II of drug-metabolizing enzymes as a result of infection with different levels of S. mansoni may thus change the liver's capacity to detoxify many endogenous compounds and may also potentiate the deleterious effects of aromatic hydrocarbons, e.g. benzo(a)pyrene, upon the liver and probably other organs. Such alterations may also change the therapeutic actions of drugs that are primarily metabolized by the P450 system, when administered to patients with schistosomiasis.

Malacological samplings were made from January 1994 to December 1996 in the Albufera Natural Park (Valencia, Spain) to trace the dynamics of molluscan populations and the prevalence and intensity of infection by larval trematodes. A total of 10,533 freshwater gastropods belonging to seven species (Lymnaea auricularia, L. truncatula, L. palustris, L. peregra, Bithynia tentaculata, Physa acuta and Gyraulus chinensis) was examined, and 110 (1.04%) were found to harbour some of the nine distinguishable types of cercariae, namely four echinostome cercariae (Hypoderaeum conoideum, Echinoparyphium recurvatum, Euparyphium albuferensis, and Echinostoma sp.), four furcocercous cercariae, and one xiphidiocercous cercaria. This study shows that the composition of the snail and trematode communities may be determined by the particular environmental conditions present and the human intervention in the area.

Using DBA/2J mice, tissue homogenates of larval Echinococcus multilocularis were injected into the mesenteric veins to generate the liver infection. Mice were treated with either albendazole or mebendazole for prolonged periods to examine the morphological changes of the metacestode. Albendazole induced disorganization of both laminated and germinal layers and suppressed the maturation of vesicles. Amorphous but loosely laminated PAS-positive material was observed inside the damaged vesicles, although new vesicles slightly developed inside or outside of the damaged ones. Active proliferation of vesicles occurred after treatment with albendazole was terminated. Hydatid cysts were more severely damaged in mice treated with mebendazole and new vesicles did not develop around the damaged ones. Also, hydatid cysts reappeared after treatment with mebendazole was terminated. These results indicate that these drugs do not eliminate larval E. multilocularis in the long-term, but mebendazole has a higher suppressive effect on multivesiculation than albendazole.

A data set comprising individual host/parasite lists from 100 Lacerta viridis (Reptilia: Lacertidae) belonging to four isolated populations in Bulgaria was studied. A total of seven helminth species was recovered (Leptophallus nigrovenosus, Plagiorchis molini, Oswaldocruzia filiformis, Spauligodon extenuatus, Skrjabinelazia hoffmanni, Physaloptera clausa and Mesocestoides sp.). Lacerta viridis is a new host record for the first five of these species. Communities of intestinal helminths of L. viridis consist of a few species which resulted in a low species richness, abundance and diversity of infracommunities, which exhibit substantial homogeneity among the four samples. A similar pattern of dominance of two nematode species leading to a relatively high community similarity at both infra- and component community levels was observed. While intestinal helminth communities in lizards from ‘marginal’ habitats were dominated by the host generalist, O. filiformis, those in hosts from ‘typical’ habitats were dominated by the lizard specialist S. extenuatus. The results indicate that the characteristics of the host's habitat are important in determining the composition rather than structure of intestinal helminth communities in L. viridis.

Acid-isolating and acid digestion techniques were used to recover the larvae of T. canis from the tissues of mice and the acid-isolating technique in particular proved to be an effective method.

Histochemical glycogen and neutral lipid studies were conducted on Echinostorna trivolvis cercariae maintained in artificial spring water (ASW) at 24–25°C for up to 24 h after emergence from host snails. Treatment of whole cercariae by the periodic acid Schiff (PAS) reagent with or without 1% malt diastase showed that cercariae depleted glycogen mainly from the tail by 6 to 24 h postemergence. The posterior tip of the tail remained PAS positive and diastase fast suggesting the presence of mucopolysaccharides there. Fresh cercariae or those stained up to 24 h postemergence with Oil Red 0 showed the presence of neutral lipid droplets in the excretory system. There was no discernible difference in the size, abundance, or distribution of these droplets in fresh or aged cercariae. Cercariae maintained in ASW plus 1% glucose for 12 or 23 h showed no evidence of resynthesizing glycogen. Nevertheless, cercariae survived longer in 1% glucose than in either 0.0, 0.1 or 0.5% glucose; but only at 23 h were any differences statistically greater (one way ANOVA, P <0.05).

A comparative study of eosinophil chemotactic factors was carried out using cysticercoids and oncospheres of Hymenolepis nana. Cysticercoids showed twice the chemotactic activity for eosinophils than the oncospheres. Eosinophilia induced by oncospheres and cysticercoids observed in secondary and primary infections, respectively, were discussed from the view point of the immunobiology of this parasite.

High performance thin layer chromatography (HPTLC) was used to determine phospholipids and sphingolipids in the intestinal mucosa of ICR mice infected with Echinostoma caproni for two weeks. The major phospholipids detected in both infected and non-infected mucosa were phosphatidylcholine (PC) and phosphatidylethanolamine (PE). HPTLC-densitometric analysis showed that there was a significant decrease in the weight of both PC and PE in the intestinal mucosa of infected mice compared to that of the uninfected controls. Cerebrosides and sulphatides, but not sphingomyelin, were identified in the intestinal mucosa of both infected and uninfected hosts. There was an apparent increase in the cerebroside content of the mucosa of infected versus control mice. The pathobiochemical changes seen in the polar lipid content of infected hosts probably reflect the feeding and behavioural activities of E. caproni in the mouse intestine.