Variability of Schistosoma intercalatum eggs in shape and size, and their similarity to those of S. haematobium presented a problem of species identification when egg morphology was the diagnostic criterion used in a study of human schistosomiasis conducted on São Tomé and Principe. More than 2500 egg measurements were obtained by light micoscopy to gather data relating to size variability of S. intercalatum eggs, to evaluate whether factors such as age of host, sex of host and intensity of infection are correlated with variability, and the data were compared with previously published measurements on different isolates and strains of S. intercalatum: the range in length (104–203 μm) embraces most of the measurements reported in other studies of S. intercalatum eggs. There was no correlation either between age and sex of the host, or intensity of infection with variability of egg size. Comparison between measurements of the eggs of S. haematobium, S. intercalatum and S. bovis eggs are presented.

An examination of the effects of Pomphorhynchus laevis cystacanths on the haemolymph and midgut gland carbohydrate titres of its intermediate host, Gammarus pulex (Crustacea) was undertaken. In the haemolymph, infection with cystacanths did not alter the relationship between haemolymph carbohydrate titres and body wet weight. However, in the midgut glands, infection did alter the relationship between gammarid wet weight and titres of glucose and trehalose (P<0.05, Chow test). The linear relationship between gammarid size and midgut glycogen titre was also significantly altered by infection. Thus circulating carbohydrate titres are unaltered in infected gammarids but storage ones are. The changes in carbohydrate titres and the relationship between individual titres and body wet weight are discussed, especially regarding parasite index.

A study on the seroprevalence of toxocariasis, using ELISA with Toxocara larval excretory-secretory antigens, was carried out on human populations in two regions of Spain. Sera from a population of 195 children from Madrid and 143 children from Santa Cruz de Tenerife (Canary Isles), showed a prevalence of 0% and 4.2% respectively. Sera from a population of 272 adults from Madrid and 803 adults from Santa Cruz de Tenerife showed a prevalence of 3.6% and 17.4%. Reasons for these differences in the seroprevalence of Toxocara in the different age groups from the two regions are discussed.

Mucosal glycoconjugates were examined in C3H mice and in hamster small intestines infected with Echinostoma trivolvis and in uninfected rodents, using periodic-acid Schiff (PAS) and high-iron diamine-alcian blue (HID-AB) staining and three different fluorescein-conjugated lectins: Triticum vulgaris agglutinin (WGA), Helix pomatia agglutinin (HPA) and Griffonia simplicifolia agglutinin (GSA-II). Lectin-labelling by electron microscopy was also undertaken with WGA and HPA lectin-gold probes. HID-AB stain demonstrated that the most mature goblet cells of the mouse villi contain sulfomucins, whereas those of hamsters contain sialomucins. The expression of lectin-binding sites and the intensity of the lectin binding in the small intestines were changed by echinostome infection. Specific differences in the reaction to mucin glycoproteins were clearly observed between the mouse and hamster intestines infected with E. trivolvis; lectin-binding to hyperplastic goblet cells and crypts in the infected mice increased, while no marked increase in the number of goblet cells and reaction to the glycoconjugates were observed in the infected hamsters. These findings indicate that the expression of terminal N-acetyl-D-galactosamine, sialic acid and N-acetyl-D-glucosamine increased in mucins secreted from hyperplastic goblet cells associated with E. trivolvis infection in mice. No marked increase in these glycoconjugates occurred in hamster infections. These findings reflect clear differences in infectivity of E. trivolvis in C3H mice versus hamsters.

Nucleotide sequence data from the Internal Transcribed Spacer 1 (ITS1) in the ribosomal RNA (rRNA) gene cluster were used to determine the utility of molecular data to discriminate species and genera of pseudocerotid turbellarians. We sequenced 388,379 and 415 bp from the ITS1 of Pseudoceros jebborum, Pseudoceros paralaticlavus and Pseudobiceros gratus respectively, to give an aligned sequence for this region of 421 positions. The nucleotide sequence of the ITS1 of Pseudoceros jebborum differed from that of Pseudoceros paralaticlavus by 6% (24/421 positions) and from that of Pseudobiceros gratus by 36% (152/421 positions). These results indicate that sequence data from the ITS1 will be a useful taxonomic tool to discriminate pseudocerotid flatworms.

The interaction between Bothriocephalus acheilognathi Yamaguti, 1934 (Cestoda)and pronephric lymphocytes of carp, Cyprinus carpio L. was studied by examining proliferation of lymphocytes isolated from both naïve fish and fish injected intraperitoneally with cestode extract. Lymphocytes from naïve hosts were stimulated to proliferate in the presence of the extract depending upon the extract protein concentrations; lower concentrations (0.01–0.05μg/ml) induced the greatest response, and immunosuppression occurred at higher concentrations. Significant differences were noted in fish that received intraperitoneal injections of parasite extracts. Five days post-injection, lymphocyte proliferation was significantly greater in these individuals compared with sham injected or untreated controls. This difference was reduced at 10 days post-injection, although the response was dependent on the concentration of the parasite extract. The possible significance of the observed stimulation/suppression of lymphocyte activity to establishment of the parasite in the wild is discussed.

Ten-day-old adults of Echinostoma caproni and E. paraensei, some of which had been exposed to 3-H-tyrosine to label sperm, were transplanted to mice in various combinations. Mating behaviour was followed on autoradiograms of worms recovered after 5 days by detecting the transfer of labelled sperm from labelled worms to themselves or to unlabelled worms. When single, labelled E. caproni adults were transplanted with unlabelled E. paraensei, they self-inseminated but did not show evidence of interspecies mating. No interspecies mating but self-insemination was observed when single, labelled E. paraensei and unlabelled E. caproni were transplanted together. When the labelled species had a choice of unlabelled adults of its own species or the opposite species, it mated in similar fashion to that seen in single species infections. The labelled species acted as if the opposite species was not present and showed an unrestricted mating pattern where it would both self- and cross-inseminate. Even though after transplant the E. paraensei adults were found in the duodenum and the E. caproni adults were found in the ileum, approximately 25% of the transplanted worms of both species were found within 1 cm of each other. Thus habitat separation was not a major cause of the lack of interspecies mating. Lack of reproductive recognition is another reason to separate E. caproni and E. paraensei into distinct species.

The surface tegument of G. tigrinum generally resembles that described for other digeneans. It contains surface tubercles and is covered with a glycocalyx. In the anterior region the tegument bears spines while tubular-like canals and occasional deep invaginations are present on the anteroventral surface. Two types of secretory body are present in the tegumental syncytium and produced in separate tegumental cells. Mitochondria are present in the surface syncytium, suggesting active transport occurs across the tegument in non-hibernating frogs.

Computer-assisted microscopy and multivariate statistics were used to establish and evaluate a procedure for identification of bovine strongylid eggs. Ostertagia ostertagi, Cooperia oncophora, Haemonchus placei, Trichostrongylus axei, and Oesophagostomum radiatum eggs were obtained from faeces voided by monospecifically infected calves. Images of single eggs (400× magnification) were recorded by a CCD camera fitted onto a microscope and digitizied on a PC. After separation of eggs from the image background, the pixel (picture element) positions of the egg outline were analysed by algorithms to describe size and shape. A stepwise discriminant analysis was subsequently used to select and rank descriptive features of 4207 eggs according to discriminatory power. Classification criteria were developed by linear discrimination analysis on the basis of selected features, and the criteria evaluated by cross-validation. A maximum average percentage of correct classification of 85.8% resulted when nineteen features were employed in a linear classification criterion. The percentages correct classification for each species were: O. ostertagi 76.3%, C. oncophora 90.8%, O. radiatum 87.8%, H. placei 90.1%, and T. axei 83.8%. Classification based on the five most important features gave an overall correct classification of 81.5%. Images of ‘unknown’ eggs could be identified automatically by the classification criteria after procedural steps performed by PC were linked in a batch program.

Eosinophil counts, interleukin 5 (IL-5) concentrations in peripheral blood and larval recovery after infection with Toxocara canis were compared between IL-5 transgenic (Tg) and nontransgenic counterparts, C3H/HeN mice. In Tg mice characterized by a constant high level of peripheral eosinophils, eosinophils in peripheral blood fell to the lowest level on day 4 of a T. canis infection and then returned to the preinfection level on day 14. Serum IL-5 level fell to the lowest level on day 4 of infection, then recovered rapidly and peaked on day 14 postinfection. In contrast, the eosinophil and IL-5 levels in the peripheral blood peaked on days 11 and 7 of infection, respectively in C3H/HeN mice. The degree of eosinophil infiltration into the lung 4 days after infection was far more pronounced in Tg than C3H/HeN mice. The highest number of larvae recovered from the lungs of infected Tg and C3H/HeN mice occurred on day 4 postinfection. Strains of Tg and C3H/HeN mice vaccinated with excretory and secretory (ES) antigens of T. canis larvae were infected with T. canis and the recovery of larvae on day 21 analysed. There were no significant differences in the mean number of larvae recovered from nonvaccinated Tg and C3H/HeN mice or vaccinated Tg and C3H/HeN mice. However, significant differences were demonstrated in the mean total number of larvae recovered from vaccinated and nonvaccinated Tg or C3H/HeN mice. These results suggest that immunocompetent cells other than eosinophils may play a significant role in the expulsion and killing of T. canis larvae in infected mice.

The induction of acquired resistance to H. polygyrus, following treatment of mice by a 6 day immunizing infection abbreviated with the anthelmintic drug ivermectin (6d I-AI), was investigated. Four worms were sufficient to elicit >80% protection against challenge and immunizing infections >50 worms generated >95% protection in female NIH mice. A few worms were recovered during the second week from immunized challenged mice but these were rapidly expelled from the gut lumen. Treatment with hydrocortisone from day 10 postinfection, permitted worm burdens to accumulate over the following 2 weeks. The 6d I-AI protocol enabled females of strains previously designated as weak responders to develop potent acquired resistance to challenge (CBA mice showed >90% protection), although weak responder strain male mice were not significantly protected. Delaying treatment with ivermectin by as little as 24 h resulted in poorer expression of acquired resistance. A positive correlation between the increasing interval from infection to treatment with ivermectin and worm burdens after challenge, and the negative correlation with IgGl antibody responses after challenge indicated that the immunodepressive activities of 7 day and older worms down-regulated local intestinal immune responses. Mice characterized by weak responder phenotype were significantly more sensitive to downregulation than mouse strains showing strong responder phenotype. In consequence, optimal timing of treatment with anthelmintics during exposure to the immunizing infection, intending to minimize exposure to the immunodepressive stages of the parasite, is sufficient to overcome reported genetic constraints on the development of resistance in this system.

The tail chamber's role in the survival and infectivity of Proterometra macrostoma (Digenea: Azygiidae) was investigated. Intact cercariae and cercarial bodies dissected from tails were incubated for 14 h in artificial pond water (APW) and cercarial infectivity was assessed in laboratory infections of the bluegill sunfish, Lepomis macrochirus. Although most cercariae stopped swimming and settled to the bottom after 14 h, survival and infectivity of bodies from intact cercariae did not decrease significantly during this period. All isolated bodies survived in APW, but they were 54% less infective. By contrast, infectivity of isolated bodies did not decrease significantly in an artificial snail saline. The results indicate that maximum infectivity in P. macrostoma is sustained throughout the swimming phase because of the tail chamber which protects the body from the effects of osmotic stress.

The cestocidal activity of Acacia auriculiformis was evaluated using rats each harbouring a single adult worm of Hymenolepis diminuta. The ethanol extract (300 mg/kg/day) and the saponins (200 mg/kg/day) obtained from the funicles of A. auriculiformis, were administered orally to two groups each of 10 rats, respectively, on day 20 after oral inoculation with a single cysticercoid of H. diminuta. Adult worms were expelled within 5 days from rats treated with the ethanol extract and within 3 days from those treated with saponins. No appreciable side effects were observed in the treated rats.

Third-stage larvae of Angiostrongylus costaricensis were cultured to young adult stages in Waymouth's chemically defined medium MB 752/l, which comprises higher concentrations of the essential components histidine, lysine, methionine, tryptophan, choline chloride and glucose than various other chemically defined media. The present study has shown that choline chloride and tryptophan are required at relatively higher concentrations for worm development than those of the other essential components.