The newly formed egg-shell from eggs in the proximal part of the uterus of Paraplerurus sauridae is colourless and transparent, whereas the shell from eggs in the distal uterus is golden yellow in colour. Histochemical tests reveal the presence of phenol, protein and phenolase in the freshly formed egg-shell. The egg-shell from eggs in the distal uterus shows the property of sclerotin. Histochemical reactions, chromatography and spectrum analysis reveal the presence of a dityrosyl linkage in the egg-shell. The nature of the protein component in the egg-shell is discussed.

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.

We are advised by Drs Sinden and Smalley that in their paper which appeared in Parasitology79, 277–96, the drug concentrations in Tables 1–5 were given as mg/ml but should read μg/ml.

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.

The shore crabs, Hemigrapsus oregonensis and H. nudus, sometimes kill the female endoparasitic entoniscid isopod, Portunion conformis, a parasitic castrator. Studies of host populations from Baja California, Mexico to Vancouver Island, Canada, show that the incidence of parasitized hosts with dead parasites and the percentage of the parasite population found dead vary markedly with locality but only occasionally with season. Both higher incidences of hosts with dead P. conformis and higher proportions of the total parasite population found dead are associated with (1) high prevalence of parasitism, (2) female hosts and (3) large hosts. Within a host, the proportion of the parasites that are dead is not related to the degree of multiple infection. Typically, either all or none of the parasites in a multiple infection are dead. Supernumerary juvenile parasites do not suffer differential mortality. The developmental stage of the female parasite does not seem to influence the likelihood of death. The presence of dead parasites may not confer an acquired immunity to re-infection. These features suggest that parasite death is typically the result of activation of a successful host defensive process rather than indicative of a defect on the part of the parasites. Parasitized female hosts can regain their reproductive capabilities following death of the parasite. Post-parasitic broods are smaller than normal. Reproductive recovery is presumed to provide the selective pressure favouring evolution of a lethal host response. The host-produced sheath surrounding female parasites is a haemocytic response. Sheaths enclosing dead parasites are thicker and more electron dense than those containing healthy parasites. The sheath of a healthy P. conformis may actually protect the parasite from a more intense host response.

The epidermis of Diplectanum aequans has, in general, been found to be similar to the epidermis of other monogeneans, consisting of a syncytial outer epidermis and sunken sub-epidermal nucleated regions. However, the epidermis of D. aequans differs from that of other monogeneans in 3 respects. These are, the presence of large areas of granular cytoplasm within the outer epidermis, the presence of myofibres invaginating into the epidermal matrix and, in the posterior regions of the epidermis, the presence of epidermal scales. These scales occur within the epidermal cytoplasm, beneath the outer membrane, and are composed of moderately electron-dense material. Also present beneath the outer membrane in the more anterior regions of the epidermis are small scale-like sclerites of a similar electron density to the epidermal scales.

The response of Awassi sheep to primary infection with 10000 Haemonchus contortus larvae and subsequent challenge with 20000 larvae was studied. Two types of response to re-infection were observed. The first, characterized by a sharp decline in egg counts, progressive improvement in packed cell volume (PCV) and a marked loss of adult worms and challenge larvae, was considered as self-cure and protection. In the second type of response there was a temporary decline in egg counts, no improvement in PCV and necropsy findings indicated hyperinfection with challenge larvae.

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.

Acid phosphatase activity was demonstrated in the intact blood nematodes, Dirofilaria immitis and Angiostrongylus cantonensis. Biochemical studies on acid phosphatase, using intact females and whole worm, body-wall and visceral homogenates were undertaken to clarify the characteristics and the distribution of the enzyme. In D. immitis, high acid phosphatase activity was observed at pH 3·8–5·8 and in A. cantonensis, at pH 4·5–6·0. Molybdate, fluoride, copper and zinc ions and L(+)-tartrate were effective inhibitors of the enzymes of both parasites while cobalt and magnesium ions and D(−)-tartrate had no noticeable effect on the activity. When the effect of substrate concentration on the phosphatase activity was studied, kinetic curves of Michaelis–Menten type were obtained with the 2 species of intact worms as well as their homogenates. The reproductive organs and body wall of D. immitis showed high total acid phosphatase activity. In A. cantonensis, the majority of the enzyme was localized in the body wall. The activity of intact A. cantonensis expressed as μg Pi/h/mg dry weight decreased with increase in mean worm weight. The characteristics of the acid phosphatase of the 2 nematodes are compared with those of other parasitic helminths and of acid phosphatase of mammalian origin. The localization of the phosphatase responsible for the hydrolysis of the external substrate has been discussed for D. immitis and A. cantonensis based on results of the kinetics and distribution of the enzyme.

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.

In undernourished rats infected with Nippostrongylus brasiliensis partial villus atrophy was observed in large areas of the anterior and posterior regions of the intestine. In addition, the following changes in structure were observed; some areas of the intestine contained misshapen villi which lacked microvilli on the lateral surfaces; cell-like bodies devoid of microvilli appeared to be budded off from the sides and tips of some malformed villi and there appeared to be extensive leakage of blood constituents into the lumen of the intestine. Morphological changes were present up to day 24 of the infection when the experiment was terminated. The possible consequences of the extensive breakdown of villus structure are discussed.

Specimens of Notocotylus attenuatus were examined in life and their ventral papillae studied by scanning and transmission electron microscopy. It was found that the papillae are non-secretory, very mobile and similar in ultrastructure to the papillae of other notocotylids previously described. Worms were removed from the host's caecum and the caecum surface examined where it had been in contact with the papillae; this revealed that the crypts in this region had been distorted and enlarged. It is suggested that the papillae serve to attach the worms to the distinct surface of the distal caecum by acting as hydraulically operated anchors working in conjunction with the lateral margins of the worm and allowing the oral sucker of this monostome fluke to be used for feeding.

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.

During the course of Schistosoma mansoni murine infection there is a dramatic increase of some immunoglobulins and S. mansoni-specinc antibodies. The most substantial response is initiated after 40 days of infection and results in a prolonged increase of total IgG1; IgM and IgA. The maximum increase is respectively 26, 14 and 3-fold the basic immunoglobulin level in control mice. Some anti-S. mansoni classes and sub-classes were studied by an original radio-immunoadsorbent test. Anti-S. mansoni IgG1 and IgM antibodies appear and increase at the same time as that of total IgG1 and IgM. Anti-S. mansoni IgA antibodies appear later (80th day) and correspond to a second peak of total IgA.

In female NIH strain mice, expulsion of a primary infection of the nematode Trichinella spiralis began on day 8 and was virtually complete by day 14 of infection. In secondary and tertiary infections, the number of larvae which established in the intestine was normal, but expulsion began on day 6 and was complete on day 10. In a primary infection the shedding of larvae by female worms began on day 5, reached its peak on days 6–7, began to decrease on day 8 and was minimal by day 10. In secondary and tertiary infections fecundity was depressed. The depression of fecundity occurred slightly in advance of worm loss. During the stable phase of infection, T. spiralis occurred in the anterior half of the small intestine. During expulsion, living worms were found increasingly in more posterior parts of the gut but their fecundity did not vary with position. After direct inoculation into the posterior ileum, adult and larval T. spiralis remained in the posterior half of the small intestine. In this position, larvae established in normal numbers, grew and reproduced normally. Therefore, any part of the small intestine was a suitable site for T. spiralis and expulsion is not merely due to a change in the position of the worms.

A living hamster cheek pouch preparation has been used to study the skin phase of schistosomulum migration. Between 0 and 16 h post-exposure schistosomula become increasingly difficult to see and lateral movement in the skin ceases. Up to 50 h post-exposure they remain poorly visible. They lie in fluid-filled lacunae within the epidermis, external to the basement membrane. The first schistosomula enter the dermis from. 40 h post-exposure, approximately half having done so by 52·5 h. Coincidentally, they can be more easily distinguished from surrounding tissue. Up to 91% of original penetrants have been observed alive in. pouch tissue at 65 h post-exposure. Since only 26% eventually mature in the hepatic portal system there would appear to be considerable attrition subsequent to the skin phase of migration. The mean diameter of venules penetrated was 22·7 μm and the mean time taken to penetrate was 8·01 h. The majority of schistosomula left the pouch between 60 and 80 h post-exposure.

Interactions between infections of Trichinella spiralis and Nippostrongylus brasiliensis were studied in the NIH strain of mouse which is known to react strongly to T. spiralis. The course of N. brasiliensis infection in this strain of mouse is described and expulsion is shown to be accelerated in immunized mice and inhibited in cortisone-treated mice. There was no evidence of inter-specific competition between the two species of worm in concurrent infections; the number and location of adults of both species were normal and T. spiralis was able to grow and reproduce normally. No evidence was found of direct immunological cross-reaction between N. brasiliensis and T. spiralis as assessed by the kinetics of adult worm numbers on heterologous challenge of immunized mice 90 days after the initiation of the last of 3 immunizing infections. Interaction was observed only when the timing of concurrent infections was such that one species was established in the intestine immediately before the beginning of expulsion of the second species. Interaction was manifested as a premature loss of worms and, in addition, as impairment of growth and fecundity of T. spiralis. These effects on T. spiralis were similar to those observed as a consequence of a specific immune response to T. spiralis. The rapidity of appearance of these effects and the lack of direct cross-immunity between the two species of worm suggest that the events involved in interaction were non-specific in action and possibly due to environmental changes in the gut caused by the immune response. These non-specific effects are therefore analogous, but not necessarily homologous, to the expulsion of these parasites in single species infections.

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.

Adult Haemonchus contortus worms simultaneously excrete and fix CO2. Their initial content of CO2 was measured as 4·55 μmoles/100mg wet weight and their excretion rate in air as 1 μmole/100 mg wet weight/h for at least 4 h. When the worms were incubated either aerobically or anaerobically with 14CO2 most of the metabolized radioactivity was associated with propan-1-ol and propionate but small amounts were found in succinate and lactate. No radioactivity was associated with ethanol or acetate, two major catabolites of glucose. Stepwise degradation of the metabolized radioactive propanol and propionate showed that all the radioactivity in both compounds was associated with carbon atom no. 1. These results show that H. contortus has much in common with the anaerobic energy metabolism of Ascaris lumbricoides but they are not inconsistent with the utilization of the tricarboxylic acid cycle by the worm. H. contortus worms were found to metabolize their excretory products. When they were incubated with either [2,3-14C]succinate or [2-14C]acetate, 14CO2 was excreted under aerobic but not under anaerobic conditions. These results are consistent with a pathway similar to that used by Ascaris operating alone under anaerobic conditions and together with the tricarboxylic acid cycle under aerobic conditions.

The pattern of recovery of schistosomula from the lungs of mice, hamsters and rats is described following normal percutaneous infection via the abdominal skin. Peak numbers were found in hamsters and rats on day 5 and in mice on day 6 post-exposure. Schistosomula were recovered from the lungs up to approximately day 20 post-exposure in all 3 species. None were found in pleural washings and only 2 were recovered following mincing and incubation of host diaphragms. The pattern of recovery of schistosomula from the lungs of mice was also described following the injection of a pulse of parasites into the tail vein. Approximately 54% of these injected schistosomula eventually reached maturity in the hepatic portal system. The ability of schistosomula to migrate and mature following their injection into unusual locations was tested. Small numbers reached maturity in the hepatic portal system following injection into the pleural cavity or subcutaneously, more when injected intra-peritoneally and largest numbers following intravenous injection. Small numbers of schistosomula were recovered by mincing and incubation of systemic organs such as the kidney and spleen. Schistosomula injected into the left ventricle of hamsters were able to migrate via the systemic organs to the lungs and 47% eventually matured in the hepatic portal system. The pattern of schistosomulum accumulation in the hepatic portal system of mice, hamsters and rats is described. Following normal percutaneous infection, schistosomula were first detected in this site from day 6 to day 9 depending on the host species. In mice, migration was complete around day 20 but continued in hamsters up to day 40 post-exposure. Following injection of schistosomula into the tail veins of mice, the first arrivals in the hepatic portal system were detected 12 h later and were found to lose their ability to migrate shortly after arrival. However, a proportion of lung schistosomula injected directly into the hepatic portal system were able to traverse hepatic sinusoids and reach the lungs. It was concluded that the route of migration of schistosomula from lungs to liver was entirely intravascular, with potentially several passages round the pulmonary-systemic circulation, before chance entry into arteries leading to the hepatic portal system. The proportion of schistosomula exiting from the pulmonary-systemic circuit was estimated as 0·14/day. A computer simulation produced values of 11 h and 5 h for the duration of migration through pulmonary and systemic capillary beds. The time for 1 complete circuit would thus be 16 h and the proportion of schistosomula exiting per circuit would be 0·095. This approximates to the proportion of cardiac output going to splanchnic organs in the resting rat (0·128). The narrowness of hepatic sinusoids may be one factor contributing to the sequestration of schistosomula in the hepatic portal system.