A modified quick-Kato technique and the Stoll dilution method for the diagnosis of Opisthorchis viverrini infection were compared from the standpoints of both replicability and sensitivity. One Stoll dilution preparation and two modified quick-Kato smears were prepared from single stool specimens collected from 221 persons in a village in north-eastern Thailand. Stool examinations were made in duplicate for each technique by two examiners, and the averages of the raw egg counts were used to estimate the intensity of infection. Statistical analyses revealed that the modified quick-Kato technique was slightly more sensitive, and thus would detect more positives, but was lacking in replicability and hence less suitable for measurement of individual intensity of infection. We therefore recommend the Stoll dilution technique for field surveys and measurement of individual intensity of 0. viverrini infection.

The nature of complement binding to the surface to infective larvae of Trichinella spiralis and Nippostronaylus brasiliensis differs. When worms were incubated in serum from uninfected hosts, washed and incubated in fluorescent reagent the whole surface of T. spiralis fluoresced but in N. Brasiliensis fluorescence was confined to the anterior end and some internal organs. The outer structure of the cuticle of the T. spiralis larvae was shown not to contain ATP-ase, thus differing from many cell membranes.

The anterior end of the miracidium of Fasciola hepatica contains a large flask-shaped apical gland and four unicellular lateral glands, all of which have ducts which pass to the tip of the apical papilla. These glands appear to be involved in penetration of the larva into the snail host. The apical gland secretes as the miracidium proves the epidermis of the host before attachment. It seems likely that its secretion is a chemical which lyses the epidermal cells. The lateral glands are PAS-positive and may contain a neutral mucopolysaccharide. They also secrete as the miracidium probes the snail and a layer of PAS-positive material may be seen at the leading edge of the apical papilla as the larva penetrates into the host. Both the apical gland and the lateral glands may be visible in the sporocyst for several days after penetration.

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.

The Introduction should read as follows:

INTRODUCTION

The Transversotrematidae is believed to be the smallest family of marine trematodes and is restricted to the Indo-Pacific region (Cable, 1974). The members of this family occupy an ectoparasitic niche, inhabiting the recesses beneath the scales of freshwater, brackish-water and marine fishes. Of the seven species in the genus Transversotrema Witenberg, 1944, the cercariae of T. patialense (Soparkar, 1924) Yamaguti, 1958, T. laruei Velasquez, 1958, T. soparkari Pande & Shukla, 1972 and T. chackai Mohandas, 1973 are already known. The larval form of the type species T. haasi Witenberg, 1944, and of T. licinum Manter, 1970 and T. chauhani Agarwal & Singh, 1981 and the adult of Cercaria koliensis Olivier, 1947 are yet to be discovered. The known cercariae develop in gastropod molluscs of the genera Melania or Thiara. An interesting feature in this group is the report of natural infections of Transversotrema haasi and T. licinum in marine fishes. As the adults are found in marine, brackish and freshwater fishes but none of the cercariae have been recorded from marine molluscs, it was thought worthwhile to study the effects of salinity, pH and O2 on survival of the cercaria of T. chackai, found in Melania tuberculata and M. scabra living in fresh and brackish water conditions.

By means of scanning electron microscopy, aspects of the attachment of Moniliformis dubius (Acanthocephala) to the intestinal wall of the rat are described together with various changes in the structure and form of the mucosa. Attachment of the parasite results in the formation of a distinct pit around the everted proboscis and a crater around the neck. Contact between the anterior region of the trunk of the worm and the intestine of the host appears to lead to villous fusion so that characteristic grooves are formed in the mucosal tissue. Evidence was also obtained to suggest that host goblet cells may become exhausted during the course of an infection with Moniliformis.

The possibility of cryopreserving the eggs of Angiostrongylus cantonensis collected from the uterus of female worms was investigated. Eggs were cultured in NCTC 109 medium containing 50% rat serum, and various growth stages, from one-cell eggs to embryonated eggs, were used in this study.

As a cryoprotective agent, dimethylsulphoxide (Me2SO) was added to the medium at a final concentration of 1 M. Eggs suspended in 0·2 ml of the medium at 37°C were cooled to 0°C at a rate of l°C min−1, then an equal volume of 2M-Me2SO solution was added. After equilibration for 15min, the freezing procedures were started. In the freezing procedures, the effectiveness of (i) a seeding process, (ii) different cooling and warming rates and (iii) the relationship between the growth stages of the eggs and their tolerance to freezing at −20°C were investigated.

It was found the highest level of survival could be obtained with 32-cell eggs cooled at a rate of 0·3° C min−1 or more slowly with seeding at −4°C and warming at a rate of 5°C min−1. Survival was influenced more by cooling rate than by warming rate.

Using these optimum conditions, the survival of eggs was then investigated following cooling to various temperatures. While more than 50% of eggs were found to survive cooling to −30–C, extremely low survival was noted from lower temperatures.

Metacercariae identified as those of the heterophyid trematode, Galactosomum ussuriense were collected from 3 species of brackish water fishes from Bheemunipatnam. The organization of the the larva is described in detail. This is the first record of the metacercaria of this species although the adult has not so far been recorded from India.

Lyophilized eggs of Schistosoma mansoni, when incubated briefly with serum from infected mice, bind antibodies, as made evident by subsequent binding of flurorescein labelled anti-IgG or 125 I-labelled protein A. On the basis of these findings, a radioimmunoassay was devised which employs whole lyophilized eggs (500 or 250 eggs/serum sample) as antigenic particles and 125 I-labelled protein A as a probe for antibody binding. Only 10 μl of serum are required to obtain 90% of the maximal binding. Kinetic studies indicated that 70% of the maximal seropositivity develops in mice between five and six weeks after a light infection, reaches a maximum at eight weeks and fluctuates around a high plateau thereafter. Pre-incubation of the test serum with soluble egg antigen (sea) considerably inhibits antibody binding to the eggs, suggesting that SEA-like antigens participate in the reaction.

Factors which influence the establishment of tetrathyridia of Mesocestoides corti in mice following inoculation per os were examined. Only a proportion of the tetrathyridia penetrate the gut wall and gain access to the peritoneal cavity and liver, and most of these penetrate through the wall of the small intestine. It appears that tetrathyridia must attach to the intestinal mucosa and commence penetration immediately or they pass into the large intestine and are voided. Establishment was not influenced by strain, sex or age of host. However, the temperature at which tetrathyridia were maintained before inoculation did influence their ability to penetrate the intestinal wall. Additionally it appears that tetrathyridia have to undergo a morphological change before or during, this penetration phase.

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.

Congenially athymic nude mice (BALB/c-nu/nu) and BALB/c-nu/+ were infected with 500 embryonated Toxocara canis eggs. Six weeks later they were reinfected with the same number of eggs. The liver and other organs were examined for numbers of 2nd-stage larvae at 2,4, and 6 weeks after reinfection. Far more larvae were trapped in the liver after reinfection than after the primary infection but fewer were found in the livers of BALB/c-nu/nu than in BALB/c-nu/+ mice.

Monoamine oxidase (MAO), catalysing oxidative deamination of biogenic monoamines, has been detected in adult Ascaridia galli. MAO was present in mitochondria and deaminated noradrenaline at the maximal rate, although serotonin, adrenaline, tyramine and dopamine were also degraded but more slowly. Of the organs studied, the body wall, female reproductive organ and intestine, the body wall (containing neuronal structures) showed highest MAO activity. Km value for chick ascarid mitochondrial MAO using tyramine as substrate was 1·66 x 10−3 M and it was most active at 2·5 mm tyramine concentration, pH 7·5 and 40°C. MAO of A. galli appeared to be thermolabile as nearly 80% of its activity was lost when the incubation temperature was increased 5° above optimum.

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.

Larval Anisakis 7·7 to 23·6mm long from euphausiids, and larvae 18·0 to 21·9mm long from a teleost fish were morphologically and morphometrically alike and fitted the description by Beverley-Burton, Nyman & Pippy (1977) of A. simplex L3. Three small larvae, 4·2 to 5·9mm long, from euphausiids resembled L3 in anterior but not in posterior morphology; their tails lacked a mucron but, in two of them, cuticular separation at the posterior extremity revealed clearly the mucron characteristic of L3 within. These small larvae are identified as L2 of A. simplex in the process of moulting to L3. Japanese reports of typical L3 from 6·9 to 32·7 mm long in euphausiids, the occurrence in teleosts of typical L3 from only 8·8 to over 30 mm long, and the present observations strongly suggest that the moult from L2 to L3 occurs in euphausiids and begins when the larvae are about 4–6 mm long. Although it appears, therefore, that only one moult occurs in the egg of A. simplex (i.e. ensheathed L2 hatches), two moults there have been reported for various terrestrial and certain aquatic ascaridoids (i.e. ensheathed L3 hatches). The morphology and homology of the lips and associated sense organs of A simplex L3 are discussed relative to that of a ‘typical’ adult ascaridoid.

A main conclusion is that euphausiids in the North-East Atlantic and northern North Sea, and perhaps universally, are major intermediate hosts of A simplex. The status as hosts of squid and teleosts harbouring L3 is discussed. An extensive literature is reviewed in relation to the present observations.

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.

Experimental investigations of the subcutaneous infection of third-stage larvae of Nippostrongylus brasiliensis reveal discrepancies between the actual and intended inoculum, and also variability between replicate inocula. Emphasis is thus placed on the importance of obtaining accurate estimates of the level of confidence associated with inoculum size. Under specified laboratory conditions, the retention of infectivity of N. brasiliensis larvae was found to be age-dependent, with a maximum of between 120 and 156 days. The motility of the larvae was not found to be indicative of their ability to complete migration and to become established in the small intestine of the host following subcutaneous inoculation.

Electron microscopic observations were made on unhatched eggs of Taenia crassiceps in utero. The outermost envelope consists of a thin, relatively smooth capsule over a highly convoluted outer envelope which contains a highly granulated cytoplasm and numerous mitochrondria. The inner envelope, consisting of a thick embryophore and the cytoplasmic component of the embryophore cell, resembles that found in most other taeniids. Three epithelial layers separate the oncosphere from the embryophore. While these layers are narrow and difficult to distinguish, the ‘oncospheral membrane’ is distinct, darkly stained and relatively thick. The oncospheral hook lies within the oncoblast with its blade portion held by cytoplasmic folds within a modified ‘sheath’ in the ‘basal epithelial layer’. Round, dense bodies are concentrated at the epithelial membranes around the ‘sheaths’. Hook muscles insert on the basal lamina at the ‘collar’ region of the hooks. Penetration gland cells are packed with numerous dense disc-shaped secretory bodies.

Microfilariae of Dirofilaria immitis retained their infectivity for susceptible mosquitoes after cooling to −196°C in the presence of 5% dimethylsulphoxide (Me2SO) using a two-step cooling sequence. Motility and in vitro development of cryopreserved microfilariae also compared favourably with unfrozen controls. Third-stage larvae frozen by the same cooling sequence in the presence of either 5% Me2SO or 16% hydroxyethyl starch were motile upon thawing. Thawed larvae completed the third- to fourth-stage moult in vitro at a frequency approximately 5 to 10% of that seen in unfrozen controls.