The transmission of Hyostrongylus rubidus and Oesophagostomum spp. following anthelmintic treatment was studied over a period of two years in a herd of sows kept out-of-doors on a commercial farm in south-eastern England. The sows were moved on to a clean pasture each autumn and at the same time were treated with an anthelmintic. The treatment was repeated six months later when the faecal worm egg count was rising. Contamination of the pasture with worm eggs was both light and intermittent. The pasture herbage remained free of infective larvae until the early summer; subsequently the herbage became lightly infected with larvae so that transmission of the parasites was possible, but limited. The level of infection on the herbage was much lower than was seen in earlier observations when the more commonly used system of treating groups of sows at different times of the year, in between farrowings, was used.

Histochemical techniques have been used to study the chemical composition of the oesophageal gland secretions of Orthocoelium scoliocoelium and Paramphistomum cervi. Results suggest that the secretions contain numerous enzymes, e.g., non-specific alkaline and acid phosphatases, ATPase, TPPase, esterase (Cathepsin C like), β-galactosidase, β-glucuronidase and N-acetyl-β-glucosaminidase. The role of these enzymes in the digestion of food in these amphistomes is discussed.

On the basis of histological and histochemical studies the caecal epithelium of the two amphistomes has been found to be syncytial bearing regularly arranged numerous, long but equal-sized and closely packed cylindrical microvilli. The role of various hydrolytic enzymes in well fed and starved flukes in relation to their gastrodermis and microvilli has also been discussed.

The survival characteristics of Cercaria chackai, the larval form of the curious ectoparasitic digenetic trematode Transversotrema chackai, in sea water, sea water diluted with deionized water in different proportions, deionized water, pond water and tap water were studied. Naturally shed, fresh cercariae had the maximum life span of 20 h 40 min in pond water at salinity 17·8‰, pH 6·45, O2 5·76ml/l and temperature 31·5°C. With increase in salinities beyond 17·8‰, survival time was drastically reduced and beyond 23·58‰,, was restricted to a few minutes. In sea water with a salinity of 38·3‰, the maximum survival time was only 8 min. Below 17·8‰ salinity, although the survival time was less, the difference was not very marked and even in tap water with no salinity, the cercariae lived up to 19 h 50 min. In deionized water the maximum survival time was only 3 h 15 min. Since pond water at pH 6·45 allowed maximum survival time, it is presumed that the cercariae preferred a slightly acidic medium. As temperature was maintained constant and oxygen was available, neither of these two factors, apparently, affected the survival pattern. It is concluded that C. chackai is a typical freshwater form showing considerable tolerance to fluctuations in salinity although the family Transversotrematidae is considered to have a marine origin.

Isozyme patterns of six enzymes, glucose-6-phosphate dehydrogenase, glucosephosphate isomerase, hexokinase, malate dehydrogenase, 6-phosphate dehydrogenase and phosphoglucomutase were examined in electrophoresed homogenates of adult male worms of Schistosoma japonicum and S. mansoni. In general, enzyme patterns obtained from the parasite homogenates differed from that of host (mouse) blood and muscle, indicating that electrophoretic patterns from parasite extracts are most probably of parasite origin. Adult male and female S. mansoni worms yielded identical patterns. However, all six enzyme patterns showed distinct differences between S. japonicum and S. mansoni. These results suggest that S. japonicum is clearly distinguishable from S. mansoni at the molecular level.

The activity, in terms of speed of action, of three anticestode drugs against Hymenolepis nana, both in vivo and in vitro, was investigated. Praziquantel was most effective in vivo, but had little action on adult worms and cysticercoids in vitro. Niclosamide, the least effective in vivo, was highly toxic in vitro. Compound 77–6 killed adult worms and cysticercoids in vitro in 10 min and 15 min respectively at 1000 μg/ml of drug concentration, but its in viro effect was intermediate between that of praziquantel and niclosamide.

Specific and non-specific esterases have been localized in sections and whole mounts of Avitellina lahorea, an intestinal parasite of sheep and goats. Non-specific esterases (NSE) were found in the sucker muscles, post-acetabular ganglia, nerve trunks, tegument, excretory canals, cirrus sac, vagina, uterus and the inner membrane of the embryophore. Acetylcholinesterase (AChE) was observed in all the above organs, including vas deferens and sperm ducts, but was absent from excretory canals and eggs. Tests with acetylthiocholine iodide (AThChI) revealed the nervous system, vas deferens, sperm ducts, uterus, cirrus sac and the vagina. The intensity of activity of AChE and AThChI was weak compared to NSE.

The development of lymphoid cells reactive to tapeworm-associated antigens during the course of Hymenolepis diminuta rejection from mice was studied using an in vitro tapeworm extract (TWE)-induced cell proliferation culture system. Mice infected with three cysticercoids on day 0 developed three adult worms by day 7 but worms were rejected by day 21 post-infection. Concomitant with worm rejection was the development of TWE-sensitized lymphoid cells which responded by proliferation when stimulated in vitro with TWE. Sensitized cells were detected in gut-associated mesenteric lymph nodes but were not detected in spleen, axillary lymph nodes, or peyer's patches of infected mice, or in lymphoid organs of non-infected mice. These studies suggest that rejection of H. diminuta from mice is associated with the activities of gut-associated, tapeworm antigen-sensitized immune cells localized in the mesenteric lymph nodes.

Acerylcholinesterase (EC 3:1:1:7) and alkaline phoshatase (EC 3:1:3:1) were detected in secretions of Moniezia expansa maintained in vitro. Ultrastructural cytochemical studies demonstrated acetylcholinesterase activity on the surface of the microtriches at the base of the interproglittidal glands and in the gland lumen but not in the distal tegument or the gland cells. Alkaline phoshatase activity was demonstrated in the cytoplasm of the gland cells and especially in their protoplasmic connections with the distal tegument. Activity was also found in the distal tegument and the microtriches. It is suggested that the acetylcholinesterase secreted by M. expansa performs a metabolic role at the worms's surface.

The histochemical site and distribution of hexokinase, glycogen phosphorylase (GP Rylase), lactate dehydrogenase (LDH) (key enzymes of glycolysis), glucose-6-phosphate dehydrogenase (GPD) and 6-phosphogluconate dehydrogenase (6PGD) (pentose phosphate shunt enzymes), isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), and α-ketoglutarate dehydrogenase (α-KDH) (key enzymes of Krebs' cycle), malate synthetase (MS) and isocitrate lyase (IL) (enzymes of glyoxylate shunt) in various tissues of Ganeo tigrinum from hibernating and non-hibernating Rana cyanophlyctis and R. tigrina were studied. Differences in their intensities were revealed. Weak activity of GP Rylase and strong activity of hexokinase in flukes from non-hibernating hosts indicates that they utilize glucose through glycolysis for energy turnover. Intense GP Rylase and weak hexokinase activity in worms from hibernating hosts indicates the utilization of glycogen. Strong activity of IDH, SDH, MDH, α-KGD, MS and IL was demonstrable in the tissues of flukes from non-hibernating hosts, suggesting that Krebs' cycle and glyoxylate shunt, respectively, were operating. Tissues of the fluke from hibernating hosts, on the other hand, displayed positive activity only for SDH and MDH; no activity for MS and IL, the enzymes of glyoxylate shunt, was observed, The activity of the above enzymes was found to be relatively low in worms from hibernating hosts.

Another species in the genus Heterocheilus Diesing, 1839, collected from Trichechus senegalensis, is described. It differs from H. tunicatus in possessing elongate cuticular plaques on the body surface in the oesophageal region, a cuticle-lined vestibule between mouth and oesophagus, and triangular interlabial structures. A comparison is made between specimens of H. tunicatus from T. manatus and the specimens from T. inunguis described in a previous paper (Sprent, 1980).