The efficacy of the salt flotation technique using saturated solutions of sodium nitrate (specific gravity 1.30) and zinc sulphate (specific gravity 1.16) for separating Ascaris lumbricoides eggs from clay, loamy and sandy soils has been investigated. Ten samples of each of the egg concentrations of 100, 500, 2500, 5000 and 10,000 eggs/25 g of soil were used for each soil type. Using T-test and ANOVA, the number of eggs recovered from sand was significantly higher than from loam and the number from loam significantly higher than from clay. With sodium nitrate, the maximum egg recovery rate was 25.04% from sandy soil at a concentration of 500 eggs/25 g soil while with zinc sulphate it was 13.88% also from sandy soil and concentration of 500 eggs/25 g soil. While the number of eggs recovered increased with soil egg concentration, the percentage of eggs recovered is inversely proportional to egg concentration. The number of eggs recovered with sodium nitrate was significantly higher than with zinc sulphate solution in the three soil types.

Faeces containing a mixture of Hyostrongylus rubidus and Oesophagostomum spp. eggs were mixed with vermiculite and water and set up at combinations of different relative humidities (65.5%, 79.5%, 90.0% and 100%) and temperatures (5°C, 10°C, 15°C, 20°C, and 25°C) in order to study the rate of egg hatching and larval development. The study established that the development from egg to infective larva showed similar patterns for the two parasites. Optimum development and survival was in the temperature range from 15°C to 20°C and ata humidities from 79.5 to 95.5%.

A mitochondria-rich fraction isolated from the cuticle-hypodermis-muscie system of Setaria cervi, a bovine filarial parasite, possessed substrate-coupled cytochrome c reductases and cytochrome c oxidase in appreciable activities. All these activities were located predominantly in the membranes. NADH-coupled cytochrome c reductase was more prominent than NADPH- and succinate-coupled reductases. All the three reductases exhibited marked sensitivity to rotenone and antimycin A. Salicylhydroxamic acid strongly inhibited succinate requiring reductase and cytochrome c oxidase, but the other two reductases only mildly. Sodium azide activated the reductases but substantially inhibited the oxidase activity. Potassium cyanide activated the succinate requiring reductase but did not cause any noticeable change in the activities of pyridine nucleotide linked reductases. Anthelmintics also influenced these activities but no definite correlation could be drawn regarding their mode of action.

Mice were infected percutaneously with cercariae of Schistosoma japonicum or S. mansoni and parasites recovered by tissue-mincing from the skin or lungs or by perfusion of the mesenteric veins. S. japonicum had a narrow peak of recovery (up to 30%) from the lungs 3 days after infection, whereas lung recovery of S. mansoni peaked only on day 6 and levelled off during the following week. Infection with S. japonicum induced lung petechiae, but only after most of the parasites had left the lungs. The axillary lymph nodes draining the infection site increased in weight after infection and this effect was much greater and longer with S. mansoni than with S. japonicum. S. japonicum was perfusable from the mesenteric veins earlier (from day 3 onwards) and in higher number (40–60% from days 6 to 10) than S. mansoni (20% on day 20). The percentage of cercariae developing to adult worms was 57% for S. japonicum and 33% for S. mansoni. The data demonstrate that S. japonicum might escape from local tissue reactions in the skin and lungs and, due to its rapid migration, might induce only poor lymphocyte proliferation. As a possible consequence, S. japonicum may establish more efficiently in mice than S. mansoni.

Entomopathogenic nematodes were isolated from soil samples collected during three separate surveys, two in the United Kingdom and one in the Netherlands. The nematodes were identified by their restriction fragment length polymorphisms on hybridization of Southern blots with a ribosomal DNA repeat unit clone. A total of eight steinernematid species/RFLP types and two heterorhabditids were isolated. The distributions of the majority of these species/RFLP types were significantly different between the three surveys and some of the species displayed a close association with certain habitat types.

Four muscle groups are responsible for the eversion and retraction of the apical denticles and enlarged pseudolabia in Skrjabinoptera goldmanae (Nematoda: Physalopteridae), which occurs in the lizards Chlamydosaurus kingii, Pogona spp. and Varanus gouldii in Australia. These muscles enable the nematode to bury its anterior portion in the gastric submucosa of its hosts. They comprise three sets which are derived from the somatic musculature and are inserted in the oesophagus and associated organs, and a fourth set of muscles which appears to be derived from the muscular oesophagus itself. These accessory muscle groups are described and illustrated, and from this their mode of action in everting and retracting the pseudolabia is derived. Possible selection pressures which led to their evolution are reviewed.

We have previously shown that it is the lung stage schistosomulum which is both the inducer and the target of immunity in rats vaccinated with irradiated cercariae but that rats can also be partially protected by immunization with detergent extracts of mechanically-transformed schistosomula. In the present study we therefore compared the immunogenicity of these and intermediate schistosomular stages. In the first experiment low levels of protection (13–24%) were induced by extracts of mechanically-transformed schistosomula cultured for 3 hours or 2 days but not by extracts of lung schistosomula. In a repeat experiment insignificant levels of protection were induced by extracts of 3 h schistosomula and lung schistosomula were again non-protective. Nevertheless, high levels of anti-schistosomula antibodies were demonstrated and sera from actively immunized rats conferred significant passive protection in five out of six trials. The levels of protection conferred by passive immunization (26–51%) were in each case higher than the levels of protection demonstrated in the respective serum donor groups, showing that some form of immunological blockade suppression is operating to prevent expression of protective immunity in the actively immunized rats.

Migration success (i.e. the proportion of worms that reach the thorax) of Onchocerca lienalis microfilariae (mf) in the haemocoel of Simulium vittatum was studied by inoculating mf into the posterior abdomen, and recording their distribution in the blackfly body at predetermined time points. Mf arrive into the thorax by active locomotion rather than by drifting in haemolymph currents. Migration into the thorax was completed by 12 h post inoculation (pi) but was not continuous throughout this period. Migration proceeded in two phases; the first occurred 0–2 h pi and the second at 6–12 h pi. Overall, migration success 12–24 h pi was only 36%, indicating thata substantial number of mf failed to reach the thorax, either because they were eliminated by the fly's defensive response or because they remained in the abdomen. Migration success was density independent Mf that arrive into the thorax within 2 h pi did not differ in their migration potential from mf that remained in the abdomen at this time. In flies where more mf migrated successfully there was lower mf loss, indicating that migration success was linked to mf loss. Moreover, the proportion of mf in the thorax was not correlated with mf loss, suggesting that mf loss affected the number of mf that migrated successfully, rather than the reverse causal relationship.

In 1988, 1989 and 1990 second year grazing heifers, naturally infected with gastrointestinal nematodes, were separated into two groups, one of which was treated orally with albendazole. In 1988 and 1989 treatment was administered immediately after parturition (February), and in 1990 during the last term of pregnancy (December). Both treated and control animals were grazed on separate plots in a rotational system. Maximum faecal egg counts were observed amund parturition, except in 1990, when treatment was given at the end of gestation. The main genera identified were Cooperia, Trichostrongylus, Ostertagia and Oesophagostomum. The number of Ostertagia larvae in the treated groups increased from 1989 to 1990, while the others decreased. Pasture contamination with third stage larvae (L3) was lower on the piots grazed by treated heifers. Maximum numbers of L3 were found in autumn, at the end of winter, and at the beginning of spring. Mean serum pepsinogen concentrations were significantly higher in the untreated groups. This concurs with the pattern for L3 on pasture. The trial shows that if a single treatment against gastrointestinal nematodes is carried out, and the animals remain on contaminated pastures, the parasitic load tends to level out after 4–5 months under favourable climatic conditions. However, the percentages of nematode genera occurring in the new populations may differ from those in the original infection.

From April 1992 until June 1993, the seasonal dynamics of Rhabdochona hellichi (Šrámek 1901) in its definitive host, the barbel (Barbus barbus), was studied in the Jihlava River (the Danube basin), Czech Republic. The parasite occurred in barbel throughout the year (overall prevalence 93% and intensity of infection 1–1384 [mean 78] nematodes per fish), but there were distinct seasonal fluctuations in prevalence and mean intensity values associated with the parasite's seasonal cycle of maturation. Prevalence was very high (usually 100%) during most months of the year, while lowest values were recorded in August and October. The highest values of mean intensity occurred in April. Both prevalence and mean intensity values increased with the body length of the hosts. The parasite exhibited a distinct annual cycle of maturation with egg-producing females present only fmm June until August, whereas larvae occurred in barbel mostly from September until April of the next year. Trichopteran (caddis-fly) larvae of the genus Hydropsyche (H. angustipennis and H. pellucidula) were found as natural intermediate hosts of R. hellichi (prevalence 4%, intensity 1–10 nematode larvae). The strictly seasonal maturation of this nematode may be associated with the temperature regime in the locality and seasonal cycles of maturation of its intermediate hosts.

Haemoglobins from three different species of trematodes (Gastrothylax crumenifer, Paramphistomum epiclitum and Isoparorchis hypselobagri) and their respective hosts were digested with papain. Peptides so produced were separated on 10–15% SDS-PAGGE. The probability of coincidence of the peptides was analysed statistically. Oxygen affinity curves of trematode haemoglobins were found to be a rectangular hyperbolic. The Hill coefficient values of all the trematode haemoglobins were found to be 1. The P50 values, at 25°C in 0.2M phosphate buffer pH 7.4, ranged from 0.8 to 1.6 mmHg.

Field study on the biology of Crassicutis cichlasomae Manter, 1936 (Digenea: Homalometridae) was carried out in a small swamp in a limestone factory near Mérida, Yucatán, Mexico. Aquatic snails, Littorina (Littoridinopsis) angulifera, harbouring C. cichlasomae rediae, cercariae and metacercariae, served both as the first and second intermediate hosts. Feeding experiments confirmed the conspecificity of metacercariae from naturally infected snails with adults from naturally infected fish. Gravid C. cichlasomae worms were obtained from experimentally infected fish 19 days post exposure at 22–24°C. Examination of fish from the swamp in Mitza and other localities in the Yucatan Peninsula showed that the cichlids Cichlasoma urophthalmus and C. meeki were definitive hosts of C. cichlasomae. There was no pronounced preference of C. cichlasomae adults for the site of their location in the intestine of the definitive host; a slightly higher proportion (41%) of worms was only found in the anterior third of the gut. The time of miracidium development varied from 18.5 to 27.5 days; different temperature (20.1–35.7°C) or light/darkness regimes influenced only slightly the rate of embryonic development, with shorter development times at higher temperature (34.8–35.7°C) and constant darkness and/or light. With the exception of the sporocyst, all developmental stages are described and figured.

Spermatogenesis and the structure of the spermatozoon of the frog intestinal fluke, Ganeo tigrinum has been examined by electron microscopy. Each testis is covered by a tunica consisting of sustentacular cells and fibrous material. Internally the testis is lined by undifferentiated spermatogonial cells, with cytoplasm rich in free ribosomes. The arrangement of the diverse spermatogonic cell populations is similar to those studied in other digeneans. During spermatogenesis the elongation and spiralling of nuclear materials occurs synchronously in the late spermatid stage. The G. tigrinum spermatozoon appears to be biflagellate due to the presence of two filaments. Between the two filaments is an elongated nucleus; these elements fuse to form the monopartite shaft of the sperm. The spermatozoon of G. tigrinum is characterized by the presence of an unusually long nucleus that even surpasses the length of the mitochondrion. At almost half the length of the spermatozoon there is sharp rotation between first axial filament, mitochondrion and the nucleus. Both the axial filaments show 9+1 arrangement of axonemal units throughout the spermatozoon.

The outer cysts (Oc) of Fasciola gigantica metacercariae (Mc) were separated in an aqueous two-phase system composed of polyethylene glycol and dextran in distilled water. A large number of separated Mc without Oc were recovered in the bottom layer rich in dextran in the system. Ten separated Mc in the layer were used to inoculate the mouse with a syringe and juveniles were recovered from the animals on the 14th day. When the number of juveniles recovered was compared with that from the mice infected orally with the same number of Mc, there was a significant difference between them (P <0.05). The former method is easier than the latter for inoculation.

A simple procedure of gel-filtration was used to purify microfilariae of the cattle parasite, Setaria digitata from its eggs. The eggs of S. digitata were also isolated from the female worms by picking out the uterine canal. Gel-filtration gave a recovery of 70% for microfilariae.

To determine the minimum effective dose of praziquantel against Hymenolepis diminuta in rats, 5.0 mg/kg, 2.5 mg/kg, 1.0 mg/kg, 0.5 mg/kg, 0.1 mg/kg, or 0.05 mg/kg praziquantel were given to each of five experimentally infected rats in six groups. Faecal samples from each rat were examined for worms on day 10. Based on the results of faecal examination and autopsy, the minimum effective dose of praziquantel against Hymenolepis diminuta in rats was determined to be 0.5 mg/kg.

Fifteen female ICR mice, 6–8 weeks old, were each exposed to 25 metacercarial cysts of Echinostoma caproni. To determine the effects of withholding food on survival, size and distribution of E. caproni in ICR mice, two groups of five each were maintained without food for 1 day (group A) or 2 days (group B) prior to necropsy. Group C consisted of five mice maintained with food for the duration of the experiment. All mice were necropsied at 12 days postinfection. There was no significant difference in worm survival, body area or distribution between group A and C or group B and C mice. The results of this experiment show that short-duration removal of food has no effect on worm survival, size or distribution of E. caproni adults in the small intestine of the ICR mouse.