The activation of the peptidergic neurosecretory system in Diphyllobothrium dendriticum was studied following cultivation of plerocercoids for short times in vitro and in vivo. In the plerocercoid the neurosecretory cells gave a very weak reaction with paraldehyde fuchsin (PAF). After cultivation for 1 h large numbers of neurosecretory cells filled with PAF-positive granules were evident. The significance of the activation of the neurosecretory system during the transfer of the worm from the cold-blooded fish host to the warm-blooded final host is discussed.

A method using light and electron microscopes is described which is suitable for the examination of gut penetration by juvenile Fasciola hepatica. It involved the ligation of small sections of the small intestine of rats and the introduction of artificially excysted flukes into these gut loops. By restricting the area of infection in this way it was possible to either recover flukes from the gut lumen or to prepare ultrathin sections for electron microscopy of flukes penetrating the gut wall. In addition, flukes were recovered from the body cavity at various times after preparation of loops in resistant and naive rats. It was found that more flukes reached the body cavity in naive rats than in resistant rats, demonstrating a resistance to infection in the gut loops of sensitized rats.

Following infection of rats with Fasciola hepatica, an increase in the number of epithelial cells in the common bile duct, labelled with [3H]thymidine, was detected autoradiographically as early as 5 days post-infection (p.i.). This initial mitogenic effect of the infection was limited to that region of the bile duct lying adjacent to the liver, while the region lying next to the duodenum failed to show any increase in labelling until 41 days p.i. Mechanical contact between the parasite and the biliary epithelium did not occur until 41 days p.i. and the initial hyperplasia was evidently not a result of mechanical irritation. The study serves to emphasize the chemical aetiology of the precocious biliary hyperplasia and to more accurately identify its onset.

Merozoites of 5 species of Eimeria from the chicken were recovered from this host and inoculated into the allantoic cavity of embryonated chicken eggs. The merozoites developed into sexual stages in the chorio-allantoic membranes, and oocysts of all the species which were tested — E. acervulina, E. brunetti, E. maxima, E. necatrix and E. praecox — were recovered. Many of the oocysts of E. maxima and E. necatrix, and a few of those of E. brunetti, sporulated and were found to be infective for chickens.

Three strains of Eimeria acervulina and 3 strains of E. mivati were compared. E. acervulina was characterized by the ovoidal shape of its oocysts and their rapid sporulation, small first-generation schizonts containing few merozoites, and its inability to complete development in the chorio-allantois of chicken embryos. E. mivati had more rounded oocysts with a Longer sporulation time, larger first-generation schizonts containing twice as many merozoites and it developed readily in the chorio-allantois. Pre-patent periods were variable but generally shorter with E. acervulina. A strain of E. mivati attenuated by repeated embryo passage showed a reduced pre-patent period.

A laboratory strain of Eimeria acervulina and 9 field isolates consisting principally of E. acervulina were tested for sensitivity to amprolium (125 p.p.m.) or dinitolmide (125 p.p.m.) in the food and for effects of the drugs on sporulation of oocysts. Judged by weight gains and lesion scores, medicaments were only partially effective against the 9 field isolates, but were highly effective against the laboratory strain. Oocysts were produced in all the infections but the percentage sporulation of oocysts from field isolates was much higher than sporulation of oocysts of the ‘drug sensitive’ laboratory strain. These results show that coccidia that are resistant to either amprolium or dinitolmide are able to cause lesions in the presence of the drugs and the oocysts that are produced will sporulate normally.

The ultrastructure of the macrogamete and developing oocyst of Eimeria maxima (Weybridge strain) was examined in the intestinal cells of chicks fed 3 different anticoccidial drugs. Amprolium at 125 p.p.m., arprinocid at 35 p.p.m. and dinitolmide at 250 p.p.m. caused considerable morphological abnormality and incomplete development of the wall-forming bodies of Type 2 (WFB II), which did not appear able to participate in oocyst wall formation. The wall-forming bodies of Type 1 (WFB I) were able in each case to participate in oocyst wall formation although amprolium and dinitolmide produced morphological abnormalities in them. In birds medicated with dinitolmide, the outer layer of the oocyst wall was formed initially at opposite poles of the macrogame tes rather than as a uniform layer. Other abnormalities resulting from drug treatment are reported and some evidence that intravacuolar tubules may be formed by the parasite pellicle is presented.

The anticoccidial effect of narasin against Eimeria flavescens, E. intestinalis, E. magna, E. perforans and E. stiedai was tested in experimentally infected rabbits. The drug was highly effective in reducing oocyst output and in preventing clinical signs. Maximum activity as measured by oocyst discharge was achieved with feed levels from 12 to 24 p.p.m.; there was no influence on oocyst sporulation. Optimal weight gain and food consumption were obtained with levels between 8 and 12 p.p.m.; at higher levels there was an adverse effect on growth, food intake, relative liver and heart weights and on serum potassium and glucose.

Mice experimentally infected with the hydatid parasite Echinococcus granulosus (secondary echinococcosis), were used as spleen cell donors for hybridoma production. Two hybridomas were produced which secreted antibody with anti-E. granulosus cyst fluid (EgCF) activity. Radio-immunoassays comparing the binding of these hybridoma-derived antibodies to E. granulosus versus several other antigen preparations from sheep parasites showed that the antibodies had a high degree of specificity for the hydatid parasite. However, using a panel of clinically defined sheep sera in a competitive radio-immunoassay, the binding of the hybridoma-derived antibodies to EgCF was inhibited strongly by sera from sheep infected with the common parasites Fasciola hepatica and Taenia hydatigena. When the hybridoma-derived antibodies were conjugated to CNBr-activated Sepharose and the crude EgCF applied to the affinity column, the ‘run through’ antigen preparation showed a significant increase in specificity for experimental E. granulosus infection. A useful means of applying the hybridoma technology in the development of new immunodiagnostic reagents may be to select those murine hybridomas which produce high-affinity, cross-reacting antibodies and to use these antibodies in the processing of homologous antigen by affinity chromatography.

The successful cellular immune response of larvae of D. melanogaster against A. tabida is characterized by an increase in the number of blood cells, a premature transformation of spherical plasmatocytes to flattened, disc-shaped lamellocytes, and the lysis of crystal cells. The plasmatocytes and transformed lamellocytes rapidly aggregate around the eggs of the parasite to form a cellular capsule, while the lysing crystal cells release substances causing the melanization of the capsule. The early appearance of large numbers of transformed blood cells in the haemolymph prior to their involvement in capsule formation suggests that transformation is independent of cell contact with the parasite and may be due instead to biochemical stimuli emitted from the parasite and/or by hormonal changes. Quantitative blood cell studies of hosts exhibiting no encapsulation and melanization response indicate that successfully developing parasites are recognized by the immune system but are able sufficiently to block the blood cell transformation and thus prevent capsule formation.

A new microsporidian parasite of a freshwater cladoceran from southern Sweden is described using light and electron microscopical methods. Development comprises 2 merogonial sequences, the first resulting in a cluster of 8 merozoites, the second in a chain of 4 merozoites. Each secondary merozoite develops into a sporont which divides into 2 sporoblasts, each of which develops into a spore. The spores are broadly oval and in fresh smears measure about 6 μm in length, with a single nucleus and a posterosome. The polar filament is about 40 μm long, of even thickness throughout, and appears as 15—18 coils in a single layer. The anchoring disc is small and the polaroplast is composed of 2 lamellar parts. Outside the plasma membrane of the sporont a 5-layered, electron-dense substance is produced, which further differentiates into endo- and exospore, an electron-dense substance occurring patchily on the exospore and a pansporoblast membrane. During development the sporoblasts and the young spores are connected by a dense substance. Mature spores appear single or paired. The pansporoblast membrane is composed of 2 structurally different layers, namely a thin outer, single membrane and an inner layer composed of tubular structures. It is connected to the spore coat by patches of the dense substance. The new microsporidium is considered to belong to a new genus of the family Telomyxidae, and its systematic relationship with this and the related family Tuzetiidae is discussed. A survey of microsporidia from Cladocera is included.

Two groups of goldfish maintained at 20°C were experimentally infected with two different sized inocula of Trypanosoma danilewskyi. One group was inoculated with 380000 trypanosomes/fish and the other with 3800. Forty and 90% of the fish, respectively, survived. All surviving fish challenged 190 days post-infection were protected from re-infection. The plasma of these fish when inoculated into another group of fish also protected them from infection. Finally, trypanosomes incubated in vitro in immune plasma at 20°C for 2 h were not infective; however, incubations at 5°C or for 1 h were not as effective.

The pathognomic, serologie and morphometric identity of a Babesia sp. recently isolated from sheep in Argyllshire was studied. Initially, problems were encountered due to the occurrence of Eperythrozoon ovis as a contaminant of the isolate and treatment with neoarsphenamine failed to remove it. Finally, a combination of oxytetracycline therapy and rapid passage allowed isolation of the Babesia sp. and its preservation in the form of a glycerolized, infected blood stabilate. Inoculation of the stabilate into splenectomized sheep produced a mild non-pyrogenic disease. Serologically the parasite was seen to have no affinity with either of the two Babesia recognized as parasitizing sheep, but some affinity with the cattle parasite B. divergens. Morphometrically it was seen to have affinity with the deer parasite B. capreoli and with the Babesia sp. isolated from red deer in Scotland, and the low number of budding forms of the parasite seen suggested that the parasite might be reproducing slowly in an alien host. It was concluded that the parasite was likely to be B. capreoli derived from red deer via the tick Ixodes ricinus.

The levels of erythrocyte membrane sialic acid from 17 patients with Plasmodium falciparum malaria and 1 with Plasmodium vivax malaria, in Papua New Guinea, have been compared with 9 uninfected controls. The amounts of radioactivity incorporated into the major erythrocyte glycoproteins by the periodate/NaB3H4 or galactose oxidase plus neuraminidase/NaB3H4 methods were unchanged by malaria infection. The electrophoretic mobilities of these proteins also were unaffected. Several new glycoprotein bands with molecular weights (mol. wt) of 160000, 89000, 46000, 42000 and 33000 Daltons were labelled on the surface of erythrocytes from infected individuals; however, none of these bands appeared in all malarious samples. Sialic acid levels on the erythrocyte membrane were also measured by exhaustive neuraminidase treatment and quantitative assay of released sialic acid. The amount of sialic acid was raised in 1 infected individual, within the normal range for Europeans in 4 others, and below this range with 3 patients. Apparently, extensive removal or modification of sialic acid on the surface of uninfected erythrocytes does not occur in human malaria, in contrast to the results obtained in earlier studies with the lethal murine malarias.

In 1977, a parasitological survey was undertaken of stool samples collected from 335 people from 5 villages in semi-arid regions of peninsular India. Stools, which were collected from various individuals in a stratified sample of 40 matched households from each village, were examined by standard diagnostic procedures. Eggs of Ascaris lumbricoides and protozoan cysts, which were identified on morphological grounds as belonging to Entamoeba spp., were most common. Other protozoan cysts were considered to be those of Balantidium coli, and eggs of hookworm and Hymenolepis nana were also observed in some of the stool specimens. The prevalence of parasitic infections varied between villages. The village with the highest prevalence of Ascaris (70%) appeared to have the greatest demands made on its meagre drinking-water supply. This village is located in a dry, windy and dusty region and it is speculated that, in addition to well-established transmission mechanisms, the villagers may be exposed, perhaps through contamination of uncovered drinking-water wells and inhalation, to wind-borne Ascaris eggs. In 1967, a WHO Expert Committee Report on the Control of Ascariasis pointed out that information on the frequency of dust-borne infection with Ascaris in man was inadequate.

Between August 1978 and July 1979, freshwater gastropods were collected at monthly intervals from 9 different non-lacustrine habitats in the Mwanza region of Tanzania. Of a total of 11708 gastropods representing 14 species, 1748 (14–9%) were infected with trematode sporocysts and/or rediae. Altogether 38 morphologically distinguishable ‘species’ of cercariae were recovered (13 furcocercous, 10 xiphidiocercaria, 6 echin-ostome, 4 cystophorous, 3 gymnocephalous and 2 amphistome species), 22 of which did not conform to previously described African species. The majority (63–8%) of all mature infections were xiphidiocercariae. Biomphalaria pfeifferi, B. sudanica and Ceratophallus natalensis each yielded 11 species of cercariae. Lymnaea natalensis had the highest overall prevalence of infection (36–9%). Cercaria guttera from L. natalensis accounted for 20–4% of all recovered trematode infections and C. blukwa from Biomphalaria accounted for 18–4% of all infections; the high prevalence of these two xiphidiocercariae may alter the transmission patterns of Fasciola gigantica and Schistosoma mansoni, respectively. S. mansoni was recovered from both B. sudanica (22 of 2393 infected) and B. pfeifferi (79 of 1913 infected); S. haematobium (or related species) was recovered from Bulinus (Physopsis) nasutus (50 of 1503 infected) and to a lesser extent from B. (P.) africanus (6 of 186 infected). The findings are discussed in relation to the biological control of trematode diseases in Tanzania.

The effects of prednisolone were investigated in C57B1/6 mice infected with Strongyloides ratti. In primary infections, the numbers of adult worms in the small intestine and larvae in the stools were increased and there was a slight delay in the spontaneous expulsion of worms. In secondary infections, there was an initial suppression of acquired resistance, with larvae appearing normally in the stools on the 5th day after infection. This was followed, however, by a rapid development of resistance and expulsion of worms over the next few days. Prednisolone treatment did not alter fecundity in primary or secondary infections. There was no evidence of autoinfection in control or corticosteroid-treated animals. Prednisolone abrogated innate resistance to infection in C3H mice. It is concluded that prednisolone probably facilitated infection by non-specific mechanisms as well as by suppressing specific acquired immunity.

The fluid layer within the cuticle of the nematode Nippostrongylus brasiliensis contains haemoglobin. The absorbance spectra of the haemoglobins extracted from whole nematodes were measured spectrophoto-metrically and the spectra of cuticular haemoglobin in individual living nematodes was obtained by microdensitometry. Adult female nematodes were confined under cover-slips in oxygenated saline and measurements of optical density of a small area of the cuticular haemoglobin were taken at 10 sec intervals. The optical density decreased over a period of 4 min at 543 nm and increased at 553 nm indicating deoxygenation of the cuticular haemoglobin; irrigation with fresh saline restored the haemoglobin to its oxygenated state. This demonstrates that cuticular haemoglobin loads and unloads oxygen in the living animal. Isoelectric focusing showed that mature nematodes have haemoglobins which are isoelectric around pH 7·0 and at pH 9·8. Isolated cuticular fluid contained the haemoglobin which was isoelectric at pH 9·8, but no other haemoglobin, and immature adults, which do not have cuticular haemoglobin, contained only those haemoglobins which were isoelectric at pH 7·0. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and column chromatography showed that the molecular weight of the cuticular haemoglobin sub-unit is 16·9–17·5 × 103 Daltons and that the haemoglobin exists primarily as a tetrameric molecule with a molecular weight of 65–75 × 103 Daltons. The presence of cuticular haemoglobin may allow adult Nippostrongylus to exploit oxygen-deficient areas within the environment of the rat's intestine where it would otherwise be unable to survive for prolonged periods.

The adenosine nucleotide and adenylate energy charge values of Nematospiroides dubius and Trichostrongylus colubriformis maintained in vitro under aerated and under near-anoxic conditions have been measured. Maintenance of the nematodes in both conditions had an adverse effect on their energy metabolism, but in comparing these effects it was found that the changes were more significant in those nematodes maintained in near-anoxic conditions and that the changes were more apparent in male nematodes. The smaller changes in the energy charge values of female worms, particularly N. dubius where there was no difference between worms in aerated conditions and those in near-anoxic conditions, were explained by the presence of eggs in the nematodes. At no time did the energy charge of nematodes in near-anoxic conditions fall below 0·50 but, whereas nematodes in aerated conditions were able to continue moving throughout the experiment, those in near-anoxic conditions stopped moving during the first 3 h. It is suggested that in the absence of sufficient oxygen the nematodes were able to maintain their energy charge above 0·50 by removal of AMP from the adenylate pool, resulting in the depletion of their total adenylate. The changes in the energy charge and behaviour of the nematodes are related to the survival of the nematodes in the oxygen-deficient environment which they inhabit in vivo.

Investigations of nematode hatching have concentrated on the parasitic forms, especially on synchronization between host and parasite life-cycles which, in some species, is so close that the parasite is dependent on the host for the hatching stimulus. Research into nematode hatching reflects the artificial separations created throughout nematology by defining research groups and their activities in terms of the host; consequently, useful comparisons between hatching of plant and animal parasitic nematodes have been few. With the increasing use by geneticists of nematodes as model animals and the interest in them by neuro-physiologists, molecular biologists and others, we hope that such distinctions will be lessened.