The gene encoding an antigenic polypeptide of Trichinella spiralis infective larvae was studied using recombinant DNA techniques. cDNA synthesized from poly(A)-rich mRNA from T. spiralis infective larvae was ligated into phage vector λgt11 DNA and packaged in vitro. The phages were propagated on Escherichia coli and a λgt11 expression library was constructed. A cDNA clone encoding a 46 kDa antigenic polypeptide was selected by immunoscreening of the library and identified by the epitope selection method. A clone containing nearly full-length cDNA for a 46 kDa protein was isolated. The gene encoding this 46 kDa antigenic polypeptide was characterized by DNA and RNA blot analysis using the cDNA as a probe. The gene was transcribed to mRNA with approximately 1400 nucleotides and translated to 46 kDa polypeptide. The antigenic polypeptide was excreted/secreted as a 46 kDa native antigen. The antigenic β-galactosidase fusion protein synthesized by bacteria had no cross-reactivity with other parasite-infected sera.

Groups of ferrets inoculated with Dracunculus insignis were treated with various anthelminthic compounds to evaluate the potential use of drugs in controlling the human parasite D. medinensis. The three primary compounds tested were diethylcarbamazine (DEC), albendazole (ALBZ), and ivermectin (IVER); they were administered in dosages of 60 mg/kg, 10 mg/kg, and 1 mg/kg, respectively. Groups of animals received treatment either once at 60 days after inoculation, once at 60 and 90 days, or for 3 days at either 60 or 90 days postinoculation. The most marked decrease occurred in the animals that received treatment once at 60 and at 90 days after inoculation. This was observed for all three drugs tested. Increased dosages, i.e., 3 days of treatment at 60 or 90 days did not result in decreased worm burdens. In no group was there a statistically significant reduction in worm burden when compared with controls. Two other compounds, metrifonate and CGP 6140, were tested in a more limited manner, but again the worm recovery rates were comparable with those in control groups. It would appear that existing drugs commonly used to treat helminthic infections are poor candidates for use in the campaign to eradicate guinea worm disease.

Fertile eggs of Toxocara pteropodis, passed in the faeces of juvenile flying-foxes, were ovoid to spheroid in shape with a diameter range of 80–110 µm. The shell was often seen to comprise 4 layers: a fine inner lipid layer, a thicker clear chitinous layer, an equally thick outer vitelline layer and a pitted outermost, proteinaceous uterine layer of variable thickness. Infertile eggs were less uniform in shape and generally did not have well-defined shell layers, the formation of which is triggered by sperm penetration of the oocyte. The eggs of this species are bulkier than those of related ascaridoids, apparently because of a thicker external coat which, while not providing mechanical strength, is thought to protect against desiccation. Scanning electron microscopical findings suggest that the outer layer is not applied directly by uterine cells, but forms by the gradual deposition of secretions in the uterine lumen, regardless of whether the oocyte has been fertilized.

Since Fasciola sp. contained proteolytic enzyme(s), it was confirmed that degradation took place in protein components in extracts of the liver flukes, which resulted in lack of clarity of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Degradation was shown to occur mostly during a heating process of the extract samples. The proteolytic activity in the extracts was completely blocked and electrophoretic patterns were improved only by the use of cysteine proteinase inhibitor N-[N-(L-3-trans-carboxyoxiran-2-carbonyl)-L-leucyl]-agmatine (E-64). Great improvement was also noted in electrophoretic patterns of the extracts of other trematodes, such as Paragonimus westermani, P. miyazakii and Clonorchis sinensis, when their extracts were treated with E-64.

Oesophagostomum radiatum developed to fourth stage larvae after 14 days in in vitro culture. However, development was totally inhibited if the standard 50% foetal calf serum in the medium was replaced by newborn calf serum. Inhibition did not occur with serum from cattle immune to O. radiatum through natural infection or experimental vaccination irrespective of the titre of specific antibodies to O. radiatum in each serum. The inhibitory action of NCS could be abolished by heat treatment at 56°C for 1 h but not by dialysis or repeated freeze-thawing. The inhibition was not consistent with observed differences in the activity of 19 enzymes in the various sera or the absence of various thiol-containing stimulants of worm development.

The effect of flubendazole orally administered at 10 mg/kg/day for 5 consecutive days (the 11th, 20th or 40th post-infection) on the number of first-stage larvae (L1) of Angiostrongylus cantonensis released in the faeces of rats each infected with 40 third-stage larvae was determined. Faecal examination for 5 months, the period from medication to dissection of rats, showed that L1 release ceased in all the rats of medicated groups by about 1 week after the termination of dosing and resumed 1–2 months later in 86% of the rats which were dissected at the end of experiments with the recovery of adult worms of both sexes. Throughout the period of 5 months, about 2–4×104 L1/gram of fresh faeces was recorded in non-medicated control groups. There was a 38–79% reduction in adult worms at the dissection. Microscopic examination of the uteri of the remaining adult worms and lung tissues of rats confirmed no normal egg production in the adult worms from rats of medicated groups, except the rats with the resumption of faecal L1 release.

Conventional methods for percutaneous infection of rats using third-stage juveniles of Nippostrongylus brasiliensis which have been artificially stimulated to exsheath lead to highly variable, and relatively poor, establishment in the intestine. A new system has been developed in which larvae applied to the skin still remain partially sheathed, as they would be in nature. Cultures of the freeliving stages of the parasite contain an annulus of clear, colourless polythene film to which some of the third-stage juveniles attach. Rats are infected with an individually counted, exact dose applied to the skin on polythene. Using this technique (‘EDT20Nb’), consistently high values for the mean proportion of the dose that becomes established have been obtained, along with a variance well below the normally accepted level ( from a total of 73 rats in 12 separate assays). In particular, the added component of variance between assays in this study was insignificant, so that the probability of quantitative agreement in replicate experiments based on the method is high. It is recommended for an experimental design in which small numbers of parasites can be used.

The known filaricides, suramin and diethylcarbamazine citrate, were tested against subperiodic Brugia malayi infection in the leaf-monkey, Presbytis cristata. As expected, intravenous suramin at 10 mg/kg daily × 5 days or 17 mg/kg weekly × 5 weeks, did not show any microfilaricidal activity, but substantially reduced the recovery of live adult worms to 50·6% and 13·6% of controls respectively. Oral diethylcarbamazine citrate at 6 mg/kg daily × 6 or 10 days reduced final microfilarial counts to 30% of initial counts four weeks post-treatment and adult worm recovery was reduced to 4·5% and 0% of controls respectively. Although the antifilarial activity of these drugs against the infection in this non-human primate model appears to be similar to that seen in man, these results have to be confirmed using larger groups of animals.

Parasitism by the larval phase of Toxocara canis is a chronic process in which the larvae survive in the tissues, resulting in the constant stimulation of the immune system. As a result, the detection of specific antibodies may not reflect the active state of the parasite. We have studied the dynamics of the production of specific immune complexes by ELISA with the monoclonal antibody TC-1 in rabbits inoculated with single and multiple doses of T. canis eggs. We also compared this with the production of specific antibodies and their possible modification after treatment with mebendazole. The specific antibodies against excretory-secretory antigen were detected with peaks at 10 and 12 weeks depending on the dose and remained positive during the entire experiment (62 weeks). Treatment caused an increase in the level of detectable antibodies dropping to similar levels to the controls. Specific immune complexes were detected only in multiple doses, and were then positive during the entire experiment. From the beginning of treatment the values of immune complexes fell quickly, remaining at undetectable levels during the rest of the experiment. For this reason the detection of specific immune complexes is a valid technique for monitoring the efficiency of treatment.

The technique of allozyme electrophoresis was applied to three species of Teladorsagia present in sheep to determine the extent of genetic variation among species. Thirty-four enzyme loci were established of which 22 were invariant and 12 were shown to be polymorphic. No fixed allelic differences were detected among the species and the level of polymorphism was within the range found commonly between populations of a single species. Therefore, the genetic data support breeding data and existing morphological evidence that T. circumcincta, T. davtiani and T. trifurcata as currently recognized do in fact belong to a single species.

Ultrastructural studies were undertaken on a discrete peri-vulval area of cuticular modification in the parasitic female of Strongyloides cebus. Cilium-like arrangements of microtubules were observed which suggested that this region was sensory in nature. The possible function of this is discussed.

Transmission electron microscopy shows that the uterus of female Schistosoma margrebowiei possesses the same ultrastructure as that of the tegument but lacks spines and sense organs. It does not possess secretory cells and opens at the gonopore which by scanning electron microscopy was seen to be composed of numerous leaf-like protrusions. The morphology of the ovary is comparable with that of other Digenea. Immature and mature ova possess cortically arranged granules and occur within the posterior zone of the ovary. Cilia and lamellae line the luminal surface of the oviduct and ootype, the lamellae running unidirectionally along the duct. Only a single type of secretory cell is seen within Mehlis' gland and this produces dense bodies which are associated with Goldi bodies. Narrow cytoplasmic channels supported by microtubules deliver these secretory bodies to the ootype. The vitelline duct is lined with cilia and lamellae and the vitelline gland contains four types of cells, S1, S2, S3 and S4. Calcareous corpuscles are found within mature S4 cells.

The new organic arsenical R7/45 is a rapidly acting and very potent anthelmintic against adult Brugia pahangi in jirds. Against adult worms implanted into the peritoneal cavity 5 subcutaneous (SC) injections at 2·5 mg/kg of R7/45 killed 100% of adult worms. A single dose SC of 20 mg/kg was 100% effective and 10 mg/kg 76% effective against adult worms. When jirds were autopsied at different times after treatment at 20 mg/kg SC 89% of worms were dead within three days. R7/45 was not active when given by stomach intubation. Pretreatment of jirds with R7/45 had no effect on adult worms subsequently implanted into jirds. R7/45 was highly active against third and fourth stage larvae of B. pahangi in jirds.

The direct action of diethylcarbamazine (DEC) on the infective larvae of Brugia pahangi was studied. The larvae were cultured in RPMI 1640 supplemented with foetal bovine serum and antibiotics for 22 days. Most of the larvae remained alive for 8 days, but survival rate of larvae decreased rapidly from day 10 onwards. The larvae did not grow in the culture system. The addition of DEC did not affect the morbidity of the larvae and no difference was observed in the morphological characteristics between the larvae cultured in the presence or absence of DEC.

The infective larvae were cultured in vitro for 5 days in the presence or absence of DEC, and inoculated into jirds. The animals were necropsied at intervals, and developing larvae and adult worms were recovered. When the larvae were cultured without DEC and then inoculated subcutaneously into jirds, 29.8% of the inoculum was recovered 3–15 days, and 25% 19–22 weeks, post-inoculation. However, when the larvae were exposed to DEC in vitro and inoculated into jirds, the rate of recovery was reduced to 25% 3–15 days post-inoculation and 2% after 19–22 weeks. When the control larvae cultured in vitro were inoculated intraperitoneally into jirds, 41·3% of inoculum was recovered 3–15 days, and 42·8% 19–22 weeks, post-inoculation. Again the corresponding value for larvae exposed to DEC in vitro was reduced to 19.8% 3–15 days, and 8% 19–22 weeks, post-inoculation. It was observed that the larvae exposed to DEC in vitro were retarded in their development in jirds. These results indicate that DEC has a direct action against the infective larvae of B. pahangi.

This report describes a case of fatal enterobiasis caused by Enterobius sp. in the mesenteric lymph nodes, lymphatic vessels of mesentery, blood vessels of the liver and lungs of a chimpanzee from Qingdao Zoo, China. Based on pathological findings, it is likely that the pinworms obtained access to these organs via the lymphatic or haematogenous pathway. As far as we are aware, this is the first reported case of Enterobius sp. in the mesenteric lymph nodes and blood vessels of the lungs and veins of the hepatic triad in a chimpanzee.

Previously undescribed cystophorous cercariae which develop in sporocyst germinal sacs in the tectibranch opisthobranch Philine denticulata (Adams) are shown to be cercariae of Hemiurus luehei Odhner, 1905 (Hemiuridae), a common stomach parasite of clupeid and salmonid fishes off the Atlantic coast of Europe, in the Baltic and the Mediterranean Sea. The free-swimming cercariae are seized by calanoid copepods. Temora longicornis (Müller) and Acartia tonsa Dana acted as suitable experimental intermediate hosts. Pressure by the copepod mouth appendages causes delivery tube eversion and the injection of the cercarcial body into the haemocoel. Sagitta sp. was found naturally infected with a metacercaria of H. luehei. The cystophorous cercaria and metacercaria are described using light and scanning electron microscopy. Adults from herring were examined under the stereoscan electron microscope.

The surface antigens of the bovine filarial parasite Setaria digitata were isolated by EDTA extraction and purified by affinity chromatography using sepharose bound human filarial (Wuchereria bancrofti) antibodies obtained from chronic human filarial sera. The purified and crude antigens were used in enzyme-linked immunosorbent assay (ELISA) for the detection of serum antibodies in bancroftian filariasis. The purified antigen showed sensitive and specific reactions in ELISA for the detection of antibodies in filarial sera and showed least cross reactivity with other parasitic infections. The crude and purified antigens showed about 18 and 6 peptide bands respectively in SDS-PAGE and about 11 and 6 antigenic bands respectively in enzyme-linked immunoelectrotransfer blot (EITB). The purified antigen was observed to be glycoprotein in nature. It was possible to identify the stage-specific infection in human filariasis by using the crude and purified antigens in EITB.