By incubating total protein extracts of Schistosoma mansoni with 3H-17-β-estradiol and 20-hydroxyecdysone, steroid binding proteins were detected in both male and female worms. The interaction of nuclear proteins with a restriction fragment of the gender and stage-specific gene F-10 was investigated using the ‘band-shift’ technique. Male and female nuclear proteins bound in a distinct way to the fragment of this gene containing putative regulatory consensus motifs. Among the nuclear proteins, only those rich in cysteine residues bound to DNA. In vitro incubation of live worms with the oestrogen antagonist Tamoxifen, altered the pattern of the DNA binding proteins, producing in females a profile similar to that obtained with male worm protein extracts. This effect of Tamoxifen could not be correlated to inhibition of protein biosynthesis. These results suggest that the regulation of transcription of the F-10 gene might involve steroid receptors.

Three types of vaccine (1) a sonicated extract of killed larvae, (2) 5-fluorouracil-treated larvae and (3) 40 krad. X-irradiated larvae have been evaluated. Pups aged 3–4 months, weighing 2± 0·5 kg and free of natural hookworm infection were selected for experimental studies. The sonicated extract was given either in a single dose or as 2 doses at weekly intervals, whereas the 5-fluorouracil-treated and X-irradiated larvae were given in a single dose only. After completion of the vaccination schedule, the pups were challenged with filariform larvae and were sacrificed 3 weeks after challenge. Non-vaccinated pups and those vaccinated with a single dose of sonicated extract lost weight and had diarrhoea or dysentery after challenge. Furthermore, in non-vaccinated pups, haemoglobin levels fell and at autopsy the intestinal mucosa was found to be grossly congested and free blood was present in the lumen of the intestine. Such findings were not obtained in pups vaccinated with the other types of vaccines. The percentage of infective larvae which developed to the adult stage in non-vaccinated pups was 82·7 ± 9·53 compared with 45·1 ± 12·33, 30·1 ± 10·05, 20·6 ± 10·60 and 8·0 ± 7·46 %, respectively in pups vaccinated with a single dose of sonicated extract, double dose of sonicated extract, 5- fluorouracil-treated and 40 krad. X-irradiated larval vaccines. While the irradiated larval vaccine provided maximum protection against clinical ancylostomiasis, 2 doses of the sonicated larval vaccine could also afford almost equal protection to pups.

Seven daily injections of betamethasone given early in the infection adversely affect the immune response of rats and mice to Babesia microti and B. rodhaini. Betamethasone given late in the infection, when the parasitaemias are declining, causes recrudescences. The effects of betamethasone are reversible and those animals which survive the primary parasitaemia recover even if further courses of drug treatment are given. Betamethasone causes recrudescences of parasitaemia in some voles and field mice harbouring subpatent infections. Attention is drawn to the possibility that the therapeutic use of corticosteroids may enhance piroplasm infections and that elevated corticosteroid levels, resulting from stress situations, may affect latent piroplasmosis in wild caught rodents.

We describe a new, improved test for the detection of intestinal infection by Entamoeba histolytica. The test depends upon immunoadsorption of the E. histolytica cysteine proteinase, histolysain, from faecal samples, and subsequent visual detection of the enzyme by a colour reaction. With samples from 200 volunteers, results agreed closely with those obtained by the conventional microscopic technique, and there were no false positive reactions with samples containing other parasites. The test is suitable for use either in the laboratory or in the field.

Toxoplasma ‘Nicolle et Manceaux’ has been examined in the electron microscope in in toto preparations from tissue cultures.

The extracellular as well as the intracellular forms of the parasite are too thick for an adequate penetration of the electron beam, and the inner structure of Toxoplasma is not revealed in these preparations.

The whole parasite is covered by a very delicate, transparent mantle which may extend to form large membranes. They show no structure in the electron microscope. No sheath has been observed which protects the shape of the parasite. Most of the free forms have an irregular surface and tend to become flat and large.

Several pictures illustrate the way in which Toxoplasma penetrates the tissue cells. In the beginning of parasitism the limits between cytoplasm and parasite are difficult to recognize. The region of the cytoplasm around the parasite is gradually dissolved and a vacuole is formed.

Merozoites of 5 species of Eimeria from the chicken were recovered from this host and inoculated into the allantoic cavity of embryonated chicken eggs. The merozoites developed into sexual stages in the chorio-allantoic membranes, and oocysts of all the species which were tested — E. acervulina, E. brunetti, E. maxima, E. necatrix and E. praecox — were recovered. Many of the oocysts of E. maxima and E. necatrix, and a few of those of E. brunetti, sporulated and were found to be infective for chickens.

1. The longevity of the fasting larvae and nymphs of Hyalomma savignyi is investigated under different conditions of temperature and humidity.

2. It is found that both larvae and nymphs are much more sensitive to humidity than to temperature. Their longevity at low humidity is short as compared with that at high humidity at the same temperature. The longevity of the fasting larvae varies between very wide limits. The mean lenght of life varies between 1·25 and 162·6 days, whereas the maximum longevity obtained varies between 2 and 241 days, according to temperature and humidity.

3. The mean longevity of the nymphs varies between 6·8 and 149·2 days. The maximum varies between 10 and 246 days.

4. The relative dispersion of longevity varies within restricted limits under different experimental conditions.

The cell surface properties of Plasmodium gallinaceum sporozoites have been investigated by means of microelectrophoretic and lectin-binding studies. Their electrophoretic mobility has been measured as a function of pH, the results suggesting qualitative and quantitative differences in the surface ionogenic groups between sporozoites from mature oocysts and those from salivary glands. Reaction of sporozoites with citraconic anhydride produced a small but significant increase in mobility, whereas 5,5-dithio-bis-(2-nitrobenzoic) acid had no effect on mobility; thus there appear to be amino groups but not –SH groups at the surface of sporozoites. Treatment of sporozoites with trypsin considerably reduced their mobility and suggests that a significant proportion of the cell surface charge is associated with protein. Incubation with neuraminidase, however, had no effect on sporozoite mobility and indicates that sialic acid residues, responsible for much of the negative charge associated with mammalian cells, are probably not present on the cell surface of sporozoites. Evidence for the presence of carbohydrates on the cell surface membrane of sporozoites was sought using fluorescein isothiocyanate–Concanavalin A. Results demonstrated that ligands similar to α-D-glucose and α-D-mannose are not present in an exposed or reactive form on the cell surface membrane of P. gallinaceum sporozoites.

Hydatidosis is a potential zoonotic helminthic disease affecting a broad spectrum of mammals, including humans, worldwide. The current review was conducted to investigate the genotypic status and prevalence of hydatid disease in camels across the world. For the purpose of the study, the articles addressing the worldwide prevalence of hydatidosis in camels were searched in several English language databases. The search process resulted in the inclusion of 122 papers. Based on the data presented in the reviewed articles, the pooled prevalence of hydatid disease in camels across the world was measured at 23.75% (95% CI 20.15–27.55). Moreover, the subgroup analysis demonstrated significant differences in the overall prevalence of hydatidosis among camels based on year, geographic area, climate parameters, camel population, gender, infected organ, fertility rate of the cyst and laboratory diagnostic technique. Furthermore, the Echinococcus granulosus genotypes identified in camels with hydatidosis included G1, G2, G3, G1–G3, G5, G6, G7, G6–G7 and G6–G10, with G6 being the most common genotype throughout the world. The data obtained from the current study are central to the better conceptualization of the biological and epidemiological characteristics of E. granulosus s.l. genotypes around the world, which can be helpful in the planning and adoption of more comprehensive control strategies.

The first marsupial demodicid, Demodex antechini, is described with notes on its life cycle, sexual dimorphism and pathology. This species is remarkably similar except for the marked sexual dimorphism, to demodicids of eutherian mammals. This suggests an early origin and a long evolutionary history of parallelism within the genus.

Our thanks to Patricia Woolley, Waite Agricultural Institute, Glen Osmond, Australia, for the specimens used in preparing this paper. We would also like to thank Clifford Desch for the photography and the drawings. The work reported here was supported in part by NSF Grant (GB-3516).

Family Diagnosis. Copepoda parasitic dorsally on Polynoid Worms.

Female with body divided into cephalothorax (head and neck) and trunk. No appendages articulated or otherwise on head or neck. No traces of segmentation. No mouth nor alimentary canal. Cuticle thin. Head and neck buried in the tissues of the host; the head converted into a voluminous organ whose only function is to absorb nutritive materials by endosmosis through expansions or rootlets. Head and neck at right angles to the middle of the trunk. A chitinous ring is usually present at the base of the neck at its insertion on the trunk. Genital apertures wide, the pyriform eggstrings issuing therefrom.

The course of primary and secondary infections with Trichostrongylus tenuis in the domestic chicken was investigated. Primary infections were established after the administration of single and trickle doses of infective-stage larvae. The worm burden in the caeca was highest after a single dose of 500 infective-stage larvae; this gave a mean of 87 nematodes per bird on days 8–9 of infection, 20 nematodes on day 14 and 0 on day 28 of infection. Following trickle doses of 60, 100, 200, 300, 400 or 500 infective-stage larvae, there was a rise and then a fall in nematode egg output in all groups. In chickens given a primary dose of 500 infective-stage larvae followed 30 days later by a single secondary dose of 500 infective-stage larvae, the mean worm burden during the secondary infection rose to 57 nematodes on day 9 of infection and then fell rapidly to 18 nematodes on day 15 and to 2 on day 30. Scanning electron microscopy showed changes in the caeca of infected birds, with the caecal surface being covered in a layer of mucus from 12 days after infection. Balls of blood-stained mucus containing nematodes were observed in the caecal droppings from day 9 of infection onwards. It is concluded that chickens rapidly expel an established infection of T. tenuis, unlike the normal host, the red grouse.

The physical nature of the cercarial surface has been observed by several workers to change during the penetration of the cercaria through the skin and its metamorphosis into the schistosomulum. Very little is known about the chemistry of this change. This paper reports the effects of the treatment of the surfaces of cercariae and schistosomula with various reagents as assessed by light microscopy. It was found that there were great differences in the stability of the surfaces of these parasitic forms. The schistosomular surface was stable to 0·2 m acetic acid, 5% calcium chloride and 8 m urea, whereas the cercarial surface was affected by these reagents. 8 m urea completely dissolved the cercarial surface, while it had little visible effect on that of the schistosomulum. This dissolution of the cercarial surface could be prevented by including small quantities of sodium or calcium chloride in the 8 m urea solution. A method has been developed to isolate pure preparations of cercarial and schistosomular surfaces. Hypotheses about the chemical changes in the surface during metamorphosis should be amenable to investigation using this method.

Schistosoma mansoni depends for its survival on glycolysis. Two glycolytic enzymes, glyceraldehyde-3P-dehydrogenase and triose-phosphate dehydrogenase, found in both the adult and schistosomular tegument, have been reported to confer partial protection against cercarial infection. This paper describes the immunogenic properties of phosphofructokinase (PFK), a rate-limiting enzyme of glycolysis, and its localization in the tegument and adjacent tissues. Recombinant schistosome PFK was used as antigen. A polyclonal antibody against purified PFK from Fasciola hepatica was affinity purified using recombinant PFK and used in combination with immunogold labelling to identify PFK by transmission electron microscopy in cryosections. In both adult worms and in schistosomula most immunogold label localized in the cytoplasmic syncytial region with less being found in the tegument. There was no significant PFK localization within or external to the outer membrane. Sera from mice immunized with recombinant S. mansoni PFK with Freund's adjuvant or alum plus rIL-12 demonstrated high titres of anti-PFK IgG, but no protection against cercarial infection. Sera from mice that were acutely or chronically infected or multiply exposed to irradiated cercariae did not recognize recombinant schistosome PFK in either Western blotting or ELISA. Similarly, sera from humans infected with S. mansoni did not recognize PFK. We conclude that in spite of the high immunogenicity of rPFK in mice, it is not a significant immunogen during the course of infection and does not confer protection from schistosomiasis. One main difference between PFK and the other 2 glycolytic enzymes seems to be the inaccessibility of PFK to the outside surface of the tegument.

The toxicity of cadmium and zinc at concentrations ranging from 0·1 to 10 000 μg/l to the life-span of decaudised cercarial bodies (cercariae that have shed their tails) of Diplostomum spathaceum was investigated. The effects of metal exposure at 3 temperatures (12, 20, and 25 °C) and 3 levels of water hardness (distilled water, soft water and hard water) were studied. In general, under most experimental conditions increasing metal concentrations reduced the life-span of decaudised cercariae. Increasing water hardness and decreasing water temperature caused an increase in the life-span of both control and metal exposed decaudised cercariae. However, at certain isolated metal concentrations, associated with a specific level of water hardness and temperature, increased survival above controls occurred. Differences in the relative toxicity of cadmium and zinc were dependent on the environmental conditions of exposure. The decaudised cercarial life-span under metal exposure was found to be generally independent of the overall cercarial survival and tail loss in most experimental conditions. Prolonged exposure to cadmium and zinc caused changes in the decaudised cercarial life-span when compared to individuals decaudised during the initial 24 h exposure period to those which were decaudised during the final 24 h period of cercarial survival. The validity of studying the decaudised cercarial life-span as an indicator of ‘fitness’ of larvae to migrate through the tissues of the target fish host, in terms of glycogen utilization, was assessed for those cercariae decaudised during the initial 24 h exposure period only. A limited reduction in the decaudised cercarial life-span during this period compared to controls was recorded, which may possibly indicate a reduced penetration ‘fitness’ of cercariae exposed to cadmium and zinc. The importance and relevance of these findings to parasite migration and establishment in the fish host are discussed.

In Parasitology, vol. xv, p. 340 (20. ix. 1923), I described a genus of nematodes from the rabbit for which I proposed the name Obeliscus. Dr Paul Bartsch, of the Smithsonian Institution, has called my attention to the fact that this name is preoccupied, having previously been used for genera of Mollusca by Humphreys in 1797, by Agassiz in 1837, and by Beck in 1837. I therefore propose the new name Obeliscoides, type cuniculi, to replace Obeliscus Graybill, 1923.

Various biological mixtures commonly used as microbiological nutrients were added to a chemically defined medium, containing 0·2% (w/v) albumin, in order to assess their ability to support maturation of eggs deposited by adult Schistosoma mansoni in vitro. Of the supplements tested, only lactalbumin hydrolysate and casein hydrolysate stimulated egg deposition and subsequent egg development in vitro. Upon addition of foetal calf serum, further stimulation was noted only in casein hydrolysate-containing media. The addition of mouse red blood cells did not significantly improve the system. Some miracidia which hatched from eggs derived from casein hydrolysate-fortified cultures displayed normal behavioural characteristics, penetrated susceptible snails and established patent infections. These results provide an experimental system for exploring the nutritional requirements of developing miracidia, and the physiological determinants that influence miracidial penetrative capacity and subsequent ability to develop in a susceptible intermediate host.

In Trypanosome congolense, the surface antigens expressed by cultured metacyclic forms are a limited and serodeme-specific subset of variable antigen types (VATs). Experiments were carried out in mammalian-form (MF) cultures, comprising dividing trypanosomes which express metacyclic VATs (M-VATs) maintained in vitro with a mammalian cell feeder layer, or in mice following infection with cultured metacyclic populations. Selective neutralization experiments were performed by incubating populations of trypanosomes with one or a combination of McAbs to remove their respective M-VATs. Deletion of one M-VAT from the population had no effect on expression and growth of other unrelated M-VATs. Deleted M-VATs were detected in very small proportions of the total population 2–7 days following neutralization. Subsequent incubation of neutralized cultures resulted in growth of deleted M-VATs which, in most cases, reached pre-neutralization levels. It appears, therefore, that in conditions where expression of M-VATs on dividing trypanosomes occurs, removal of individual M-VATs results in their re-expression within the population.

The accumulation of heavy metals in macroparasites of fish has been widely studied in freshwater environments. Less is known about metal uptake in cestodes parasitizing marine fish. Lacistorhynchus dollfusi is a common larval cestode parasite of Pacific sanddab (Citharichthys sordidus), a flatfish species inhabiting Santa Monica Bay. The ability of this cestode to concentrate metals in its tissues was compared with metal levels in its sanddab host. Fish and cestode tissue were analysed for 14 elements using Inductively Coupled Plasma Mass Spectrometry. The elements analysed were silver (Ag), arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), potassium (K), lead (Pb), rubidium (Rb), selenium (Se), strontium (Sr), titanium (Ti) and zinc (Zn). Three of the 14 metals (Cu, Hg and Zn) were significantly greater in concentration in L. dollfusi compared with their levels in the liver, intestine and muscle of their fish host. They ranked in concentration from highest to lowest as follows: Zn > Cu > Hg. The ability of the cestode L. dollfusi to uptake metals at higher concentrations than its host warrants its consideration as a candidate for a heavy metal accumulation indicator of pollution exposure in Pacific sanddab.