A total of 444 adult frogs (Rana temporaria) were obtained from three sites in the east of Ireland. Oswaldocruzia filiformis was present at all times of the year; overall, 64% of the frogs were infected, with a mean burden of 5 worms/frog. Most of the parasites were in the first half of the small intestine. A single gross lesion associated with a high worm burden is described. Female parasites were more abundant than males. Most parasitic stages of O. filiformis overwintered in hibernating hosts. Seasonal patterns in the levels of parasitization were not discerned. The intensity of infection was significantly greater in female than male frogs at one of the sites. There was little correlation between the size of host and degree of parasitization. None of the 45 frog tadpoles examined harboured O. filiformis. Frogs became infected by August of their first year.

Paragonimus ohirai-infected rats were treated with cyclosporin A (CyA) at different times during the course of infection. CyA (5×80 mg/kg) affected the worm recovery, growth and maturation rates of P. ohirai with respect to control values. This tendency was most remarkable in animals treated 15 days and more after infection with CyA (groups B, +15 to +19 days; C, +25 to +29; D, +35 to +39 and E, +45 to +49). In group A (0 to +4), however, the drug did not affect markedly the growth and maturation of worms, although it significantly lowered worm recovery rates. CyA administration also affected normal migration of P. ohirai in the highly susceptible host (rat), when the drug was administered during the peritoneal and/or liver phase of infection. Thus, in this P. ohirai/rat model, CyA significantly reduced worm recovery rates, and affected the growth, maturation and migration of the worms depending on the time of administration.

The immune response of hamsters to a chronic hookworm infection has been investigated. Ancylostoma ceylanicum caused long term infections in hamsters which were associated with prominent changes in secondary lymphoid organs. The mesenteric lymph nodes and spleens increased rapidly in size stabilizing at approximately 3–4 times the weight in control animals by weeks 3–7. Cells from both the mesenteric lymph node and spleen, after an initial period of increased blast cell activity, became less reactive in the latter stages of infection. Serum antibody responses were marked, commencing in weeks 3–4 and increasing in intensity throughout the 10 week period of measurement. The results are discussed in relation to their contribution to the understanding of human hookworm infection.

The distribution of zinc in representative groups of parasitic helminths was determined by the use of the atomic absorption spectrophotometer. The results of these analyses have shown that growing flukes (smaller forms) with active oogenesis and spermatogenesis contained more zinc than old (large) or very old adults with an empty uterus and large lobulated testes. In cestodes, the neck region and immature proglottids showed more zinc concentration than mature and gravid proglottids and fully grown cyst walls. Similarly, the youngest endogenous daughter cysts of Echinococcus granulosus contained more zinc in their walls than those of larger/older forms. Zinc was concentrated more in nematode eggs than in adult females.

It has been established that the wall of the metacercarial cyst of the strigeid digenean Apatemon (Australapatemon) minor from the leech Erpobdella octoculata shares with Apatemon (Apatemon) gracilis the remarkable ability to expel the metacercaria forcibly from the cyst, an event which presumably occurs when the cysts are eaten by the bird definitive host. When cysts of A. minor are treated in vitro with a solution containing a mixture of bile salts and trypsin following pretreatment with acid pepsin, the metacercaria is expelled in an explosive manner through a canal at the narrow end of the pear-shaped cyst. This expulsion is produced by a sudden and substantial inward expansion of the birefringent wall, as a consequence of which the cyst lumen is virtually eliminated. Expulsion of the metacercaria in this explosive manner also occurs when similarly pretreated cysts are exposed to either bile salts alone or to trypsin, but cysts treated with the latter take longer to respond. When the cyst wall is perforated with a needle, inward expansion of the wall occurs and the metacercaria is forcibly ejected through the perforation. A variety of other pretreatments and treatments was tested but pepsin appears to be the most effective “primer”, apparently producing localized changes which permit the exit of the metacercaria. These observations are discussed in relation to the mechanism of expulsion.

Analysis of the major biochemical components of Taenia hydatigena cysticerci collected from goats and pigs showed marked differences, particularly in glycogen, protein, lipid and DNA levels. Differences were also detected in the levels of cholesterol, triglycerides, free fatty acids and phospholipids. Furthermore, the profile of phospholipid fractions revealed quantitative differences between the two species. It is concluded that the cysticerci of goat and pig origin probably represent two different strains and possibly follow the same pattern of speciation as reported in the related taeniid, Echinococcus granulosus.

A case is presented of infection by Oesophagostomum, a nematode worm, producing a cutaneous nodule in man. Of the 70 individual cases reported in man it is believed that this is the first in which the worm has produced a lesion outside the gastro-intestinal tract and without evidence of bowel infection. This finding suggests either that the worm is able to achieve direct skin penetration or that it can be disseminated from the bowel via the bloodstream or the lymphatics. The pathology caused by Oesophagostomum and the possible modes of infection are discussed in relation to studies in animals, particularly simians and cattle.

Third larval stages (L3) removed from fish fillets, fourth larval stages (L4) raised in in vitro culture, and adults of Pseudoterranova decipiens, collected from grey seal (Halichoerus grypus) stomachs, were exposed to the broad spectrum anthelmintic, ivermectin. L3 and L4 parasites were exposed, in vitro, to 500, 100, 50, 20, 5 and 1 μg/ml concentrations of the drug, in culture media. Adult P. decipiens were exposed in vitro to a concentration of 500 μg/ml ivermectin, only. Controls consisted of parasites placed in culture media alone or culture media plus drug vehicle. These three developmental stages of P. decipiens were all found to be susceptible to the effects of ivermectin.

In the presence of glucose and galactose, the incorporation of radioactive inorganic phosphate (32Pi) into phosphatidylcholine of Hymenolepis diminuta was significantly lowered as compared to the control, whereas other phospholipids remained unaffected. α-methyl-D-glucoside, however, significantly lowered the amount of 32Pi incorporated into phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine and phosphatidic acid. Mannitol did not have any effect on the incorporation of 32Pi into the phospholipids of H. diminuta. The effect of glucose and α-methylglucoside on phospholipid metabolism was both time and concentration dependent. The inorganic, organic, total and phosphatidylcholine-bound phosphate of H. diminuta in the presence of various substrates were not significantly different from the control values under all incubation conditions. The results indicate that the observations made in the presence of external glucose, galactose and α-methylglucoside were due to their physical interaction with the transport mechanism in the tegumental membrane of H. diminuta and also their being subsequently metabolized in the cases of the former two hexoses.

Hydatid fluid collected from the lungs and livers of sheep and humans was analysed for protein and lipid composition. There were no marked differences in the composition of these parameters and the major lipids were triglycerides and diglycerides. The phospholipids, which formed the minor fraction, were mainly phosphatidyl choline and phosphatidyl inositol. Cholesterol present was in the free form.

Metacercariae of Plagiorchis species 1 were observed to hatch by an active mechanism in a medium free of enzymes. A hatching opening in the bilayered cyst wall was formed by the combined action of caecal fluid extruded by the activated larva through the mouth opening and an internal pressure due to the tendency of the cyst wall to contract on hatching, resulting in an explosive expulsion of part of the metacercarial body. The cyst wall was apparently pierced at any place where the larva delivered its caecal fluid. After excystation the hatching medium contained high phosphatase and proteinase activities and was able to dissolve the inner walls of empty cyst envelopes. The phosphatase activity assayed on 4-methylumbelliferyl phosphate was optimal at pH 3–5. The proteolytic activity was demonstrable on photographic film, Azocoll, and synthetic chromogenic and fluorogenic peptides. A preference for peptides was found which are also susceptible to plasmin. The proteolytic activity was optimal at pH 3–9 and 40–45°C and, when assayed on Suc-Ala-Phe-Lys-MCA, was only due to thiol proteinase(s) according to inhibitor studies. It is suggested that the proteinase(s) represent the hatching enzyme(s) of the metacercaria, because (a) only proteolytic activity was detectable in the pH range optimal for excystment, (b) the inner cyst wall is stabilized by proteins, and (c) the inner wall is dissolved by other proteinases such as trypsin. Enzyme histochemical investigations of metacercariae showed that, in the caeca, acid phosphatase was present mainly before hatching and non-specific esterase developed after hatching. Proteolytic activity was not localized with the methods used although it was suggested that it derived from the caecal fluid. A possible relationship of the thiol proteinase(s) detected in the hatching medium to haemoglobin-digesting proteinases from the gut of schistosomes is discussed.

Inorganic analysis of Ascaridia galli has shown the levels of sodium, potassium, copper, magnesium, calcium, zinc, iron, nitrogen, phosphorus, sulphur, chlorine and cobalt (expressed as percentage of dry weight) to be higher in females than in males.

Peritoneal Echinococcus granulosus in gerbils was treated with albendazole. Both early and late infections were studied; response to albendazole therapy and the ability of the parasite to recover after treatment was found to depend on dose and length of therapy. Even after treatment at 50 mg/kg for 2 months late infections retained the ability to recover over 3 months.

Volume 63, page 48. Table I.

No. of animals examined in April should read 108.

No. of animals examined in May should read 121.

A simple method for the collection of third-stage larvae of Necator americanus has been described. This technique provides repeated recovery of very clean larvae from cultures in moderate numbers.