The diagnosis of the genus Polycliphora gen. nov. is based on the large number of haptoral clamps and on their skeleton. The systematic position of the parasite is discussed. Among the Diclidophoridae, Polycliphora nezumiae gen. et sp. nov., becomes the type of a new sub-family.

Mycoses of the gypsy moth, Lymantria dispar (L.) by two species of entomogenous fungi, Metarrhizium anisopliae (Metschnikoff) Sorokin and Paecilomyces fumoso-roseus (Wize) Brown and Smith were experimentally established. Infected larvae revealed complete disintegration of viscera within 95 h post-inoculation with M. anisopliae and within 120 h with P. fumoso-roseus. Avian safety studies confirmed the tolerance of large dosages of spore suspensions of both species. Some body weight loss was recorded but all other indicators were not significantly different from the control birds.

A technique is described for the recovery of infective larvae of strongyloid nematodes from sediment resulting from the washing of pasture and soil samples. The process of recovery and counting of larvae is described by a model based on the binomial distribution. Tests of the technique have shown that it will recover approximately 50% of the larvae present in samples of pasture sediment of either 7·5 or 12·5 ml in volume after centrifugation. The efficiency of the technique was independent of the number of larvae present in samples of pasture sediment. The technique was shown to be less efficient and more variable in recovery of larvae from samples of soil sediment. Estimations in efficiency of recovery from soil sediment ranged from 64 to 110·2% and a significant effect of volume of sediment on recovery was detected.

The metacestodes of Taenia pisiformis have been shown to contain a protease inhibitor capable of inactivating the esterolysis of N-α-benzoyl-L-arginine ethyl ester (BAEE) and N-benzoyl-L-tyrosine ethyl ester (BTEE) by trypsin and chymotrypsin, respectively, of bovine, dog and rabbit origin, but not affecting the hydrolytic activity of subtilisin, elastase, collagenase, pepsin, rennin and papain. This inhibitor has been demonstrated in whole worm extracts and in the incubation medium of in vitro-maintained, intact living metacestodes. The protease inhibitor which was purified by trichloroacetic acid precipitation, Sephadex G–100 chromatography and affinity chromatography on CNBr-activated Sepharose 4B–bovine chymotrypsin conjugate was soluble in 5% trichloroacetic acid, withstood heat up to 80°C, tolerated the pH range 1·5 to 9·0, was unaffected by 8 M urea or 0·2 m 2-mercaptoethanol and had a molecular weight of about 7000 to 7200, as calculated from its gel chromatographic behaviour. Complex formation between the inhibitor and the enzymes required 3–4 min for completion. The enzyme–inhibitor complex was not dissociated by 4 m KC1. Activity determinations on bovine TPCK–trypsin and bovine chymotrypsin with BAEE and BTEE assays revealed that the inhibitory actions toward both enzymes are functions of the same or closely adjacent sites of the inhibitor molecule. The supposed function of the inhibitor is discussed.

When eggs of Ascaris suum were transferred from glass-distilled water into 0·1–0·4 m NaCl solutions, the water content of the unhatched juveniles fell with increasing concentration of solute. The effect was reversible. The egg-shell was thus permeable to water. The osmotic pressure of the egg fluid was osmotically equivalent to between 0·1 and 0·2 m trehalose. In hatching experiments in Fairbairn's medium containing 0·1 or 0·2 m trehalose, only 5 and 3% respectively of the eggs hatched; 83% of the eggs hatched in the absence of trehalose. The evidence suggests that loss of solutes from the egg fluid permits an increase in the water content of the unhatched juveniles and that this may be responsible for ending their quiescence.

To evaluate their protective potential, excretions and secretions of adult female Angiostrongylus cantonensis were prepared from an in vitro culture fluid and injected together with Freund's complete and incomplete adjuvants into rats and mice. Under appropriate conditions, judging from reduced mortality rates and/or prolonged survival periods, these animals were protected against a lethal challenge infection with 3rd-stage larvae. Although both ‘immunized’ and unimmunized mice died following such a lethal infection, the survival period for the ‘immunized’ group was significantly longer than that of unimmunized controls (40·8 compared with 26·7 days). On the other hand, the mortality rate of ‘immunized’ rats was reduced to 25% as compared with 100% in unimmunized controls. There was also evidence of adverse effects on parasite development in these ‘immunized’ rats. The number of young adult worms recovered from the brain 21 days after challenge infection and both the number and size of mature male and female worms in the lungs 60 days after infection were significantly reduced in the ‘immunized’ rats. Moreover, the reproductive activity of female worms was depressed, as evident from the output of 1st-stage larvae in the faeces and the number of eggs released during maintenance in vitro. The quantity of proteins released during in vitro maintenance of adult worms in a chemically defined serum-free medium was 0·2–0·5 μ/worm/day. The concentrated culture fluid contained at least 7 different antigenic components when analysed with hyperimmune rabbit antiserum to female excretions and secretions (FES) antigen. Polyacrylamidegelelectrophoresis in sodium dodecylsulphate showed the presence of 3 major and at least 12 minor protein components with molecular weights varying from 24000 to 115000 daltons. Different lines of evidence presented in this study show immunological cross-reactivity among antigens from different developmental stages.

A study was made of the protective effects of plasma (CMP) from mice convalescent from infection with Trypanosoma cruzi. A single dose of CMP was injected into mice infected with blood trypomastigotes of 1 of each of 5 strains of T. cruzi. Protection was greatest with strains BG, M1 and Y, and least with strain Peru. Strain Tulahuen was of intermediate susceptibility. The protective effect of CMP was found to be similar in mice infected by metacyclic trypomastigotes harvested from vector bugs and mice infected by blood trypomastigotes. Plasma (IMP) from mice hyperimmunized with 6 doses of a killed T. cruzi epimastigote vaccine with saponin as an adjuvant gave no protection against challenge with strain Y, although a group of mice hyperimmunized in parallel with those from which IMP was taken were strongly resistant to challenge.

Homologous and heterologous resistance in Echinostoma revolutum infections was studied in mice. A high level of homologous resistance was demonstrated in mice harbouring a 13-day-old primary E. revolutum infection with 9–10 and 11–15 worms, corresponding to a 70·0 and 66·7% reduction in the size of the established worm burden as compared with that of the challenge control group. A 14- and 20-day-old primary infection with 3–4 worms induced a level of resistance of 61·7 and 81·8% respectively, while higher worm levels of 9–10 and 11–15 induced almost complete resistance corresponding to a 95·1–100% reduction in the size of the established worm burden. Complete resistance was also demonstrated in mice challenged 8 days after elimination of a 20-day-old primary infection with 11–15 worms by anthelmintic treatment. A primary 43-day-old Schistosoma mansoni infection induced a 73·1% reduction in the size of the established E. revolutum challenge infection while infections of an age of 79 and 99 days conferred complete resistance to heterologous challenge with E. revolutum. Primary pre-patent S. mansoni infections and a patent S. bovis infection of an age of 56 days did not induce any resistance to challenge with E. revolutum. A primary 14- and 21-day-old infection of E. revolutum did not stimulate any significant level of resistance to heterologous challenge with S. mansoni.

Circumstantial evidence suggests that the earlier detachment of Boophilus microplus larvae from highly resistant cattle follows the release of histamine at the attachment site. In vivo and in vitro experiments show that a proportion of the larvae will detach following injection or infusion of histamine. Other mediators such as bradykinin, prostaglandin E2, 5-hydroxytryptamine and dopamine have little or no effect on tick behaviour in vivo. Sensitivity to histamine declines as larval attachments stabilize, and repeated injections have no effect on the weight of larvae after 3 days on the host. Response to histamine is discussed in relation to host resistance, histology of the feeding lesion and larval behaviour.

The influence of Meloidogyne javanica on cytokinins in the host Lycopersicon esculentum has been studied at different stages of the nematode's life-cycle. Marked differences were detected in cytokinin content of root homogenates between infected and control plants, particularly at the 3rd (32 day), 4th (39 day) and 5th (55 day) harvests. Most of the cytokinin detected appeared to be associated with root homogenates in which the nematode was in the rapid post-moult growth stage. The influence of these nematodes on cytokinins in the host's xylem exudate was not nearly so pronounced. The freshly hatched 2nd-stage infective larvae of M. javanica were themselves capable of exuding cytokinin-like substances.

A procedure is described for the isolation of sub-cellular fractions from bloodstream forms of Trypanosoma brucei. The method leaves intact most of the nuclei, mitochondria and microbodies. All the fractions have been chemically characterized and tested for 10 enzymatic markers. About 5% of total cell protein was isolated as a microsomal fraction containing mostly plasma membranes and endoplasmic reticulum vesicles. Plasma membranes were purified by high-speed centrifugation on magnesium-containing Dextran, and on linear sucrose-density gradients. The yield of membranes was approximately 0·3% of the total cell protein. The purified material had a sucrose density of 1·14 g/cm3 and consisted of smooth vesicles. Specific activity of the membrane markers Na+, K+, ouabain-sensitive ATPase and adenylate cyclase were 26-and 20-fold higher, respectively, than in total cells. Neither DNA nor RNA was detected. The sum of the cholesterol and phospholipid content was 0·99 mg/mg protein. The cholesterol/phospholipid molar ratio was 1 : 2.

A model has been developed to simulate the surface of an antibody-coated schistosomulum. It consists of a layer of agar, containing antigen (tetanus toxoid) and a chemotactic factor (ECF). Some layers were coated with human anti-tetanus immunoglobulin. The mode of adherence of human eosinophils and neutrophils to these agar layers and the subsequent degranulation of the cells exactly paralleled the interaction of these cell types with antibody-coated schistosomula of Schistosoma mansoni. In particular, eosinophils made much more intimate contact than did neutrophils, and lysosomal enzymes were secreted extracellularly by direct fusion of granules with the plasma membrane of the cell. Biochemical evidence was also obtained for the secretion of enzymes during degranulation and the rate of enzyme release was found to be enhanced in the presence of specific antibody. This model, non-phagocytosable surface has the potential to provide basic information on the mode of action of effector cells in cell-mediated cytotoxic reactions against a wide range of parasites by incorporation of different factors into the agar layers.

Plasmodium knowlesi merozoites were prepared by the polycarbonate sieving method of Dennis, Mitchell, Butcher & Cohen (1975). Merozoite function was assayed by their attachment to and invasion of rhesus erythrocytes at 37 °C. The early merozoites from the culture chamber were the most invasive, although maximum numbers of merozoites appeared later. Merozoites were most stable when incubated at room temperature (23 °C). At 37 and 0 °C invasiveness rapidly declined to zero. Attachment was rapidly lost at 37 °C but was retained at 0 °C. Attachment was unchanged in the pH range 6·8–7·9 but invasion was reduced at pH 7·9. The presence of l-fucose, d-galactose, d-glucose, d-mannose, N-acetyl-d-galactosamine or N-acetyl-D-glucosamine did not reduce invasion. Attachment and invasion were greatly reduced or abolished by the presence of 2·5 mm EDTA or EGTA, by lactoper-oxidase-catalysed iodination of the merozoites, or by treatment of the merozoites with trypsin at a concentration of 1 μg/ml or greater for 10 min at 23 °C.

A staining technique was developed for locating the sporozoites of Eimeria spp. in both mammalian and avian hosts. Bouin-fixed tissues embedded in Paraffin wax and cut at a thickness of 3 μg were stained by a controlled sequence of Ehrlich's haematoxylin, acid fuchsin and aniline blue–orange G–acetic acid which took only 30 min to perform. The refractile globule of the sporozoite stained a brilliant crimson whilst the tissue had an overall blue colour, thus enabling rapid scanning of material under low-power magnification. The granules of eosinophils and heterophils also stained a brilliant crimson and their significance in immunological responses indicates a wider application for this technique.

The in vitro absorption of glucose and l-methionine in the intestine of broiler chickens was measured 7, 14 and 21 days post-inoculation (p.i.) with sporulated oocysts of Eimeria acervulina, E. mivati, E. maxima or E. brunetti. The small intestine of each bird was divided into 8 regions of equal length and absorption was measured on 3 tissue disks of equal size from each region. The absorption rate of each substrate with each coccidial species was measured based on (1) an equal area from each region, (2) an equal weight from each region, (3) the total absorption in each region and (4) the total potential absorption in the intestine. Comparisons of absorption rate of equal areas in each intestinal region demonstrated that infected birds at 7 days p.i. absorbed significantly less substrate per unit area in the regions of maximum infection than uninfected controls. Malabsorption was less apparent when the weight of the region was used as the unit of measurement. Compensatory absorption was seen in some uninfected regions with E. acervulina. The total potential intestinal absorption at 7 days p.i. was reduced with E. mivati, E. maxima and E. brunetti but not with E. acervulina. At 14 days p.i., total l-methionine and glucose absorption in some regions of the intestine was significantly increased with E. acervulina but not with E. mivati, E. maxima or E. brunetti. No absorption differences were seen at 21 days p.i. with any species.

Recent microscopic studies of Theilerial parasites in. ticks appear to provide convincing evidence for a sexual cycle for these parasites. This evidence would remove most of the objections to placing piroplasms in the same class as malarial and coccidial parasites. It is suggested, therefore, that the class Piroplasmasida (Piroplasmea) be abolished and that piroplasms be located in a sub-order Piroplasmorina alongside Haemosporina within the class Sporozoa (Teleospora).

If the close relationship of Theilerial and malarial parasites is correct then by analogy meiotic or reduction division of Theileria probably occurs during sporogony in the tick salivary gland acinar cells. This means that all bovine stages are haploid. If these can be cloned and characterized by isoenzyme or drug resistance markers, then genetic recombinant studies, similar to those performed with malarial and coccidial parasites, could be conducted.

The potential of genetic recombination greatly increases the scope of the parasite for developing new variants. This potential is greatest in areas where there is a variety of tick and host species which apply different types of selection pressure to parasites. Atypical strains of Theileria are usually isolated from such areas, and although the characteristics of these strains may not be expressed in the wild, unnatural selection by laboratory passage may reveal their presence. The apparent lability of such strains may simply be cloning of different genetic recombinants.

If different strains can be cloned and characterized it may be possible by genetic recombination techniques to develop new clones which retain desired characters for use as avirulent protective vaccines, but from which undesirable characters have been eliminated.