Corynosoma spp. (Acanthocephala) infection in ringed seals (Pusa hispida) is compared in spring and in autumn in the Bothnian Bay, northern Baltic Sea. The material consists of more than 13400 specimens: 7590 from the intestines of 13 seals captured in April and May 1978 and 5850 from 29 seals captured in October and November.

Corynosoma strumosum infection had approximately the same intensity in spring and autumn (mean 76 and 66 individuals/infected seal, maxmum 313 and 324 individuals, respectively). C. semerme specimens, on the other hand, were 37 times more numerous in spring than in autumn (504 compared with 136/infected seal, maximum 1700 and 1230 individuals, respectively). The ratio of C. strumosum to C. semerme was 1:6·3 in spring and 1:2·0 in autumn, as calculated from the total material. Corynosoma infection was more recent on average in spring than in autumn, as judged both from the proportion of males and immature females and from the distribution of C. semerme in the intestine. The feeding habits of the ringed seals and the rate of development of Corynosoma infection are discussed.

Partly developed strobila of Echinococcus granulosus from a 28–38 days infection in a dog have been brought to maturity by culturing in both liquid and diphasic media.

Surface-sterilization of the worms from dogs was achieved by use of antibiotics. Maturation was most successful in a diphasic system consisting of Parker 199+10% inactivated bovine serum over a solid base of coagulated bovine serum and a gas phase of 8% O2+5% CO2 in N2.

In the most successful results in diphasic media, a 28-day-old strobila reached maturity after a further 14 days in vitro culture, and a 35-day-old strobila matured after 6 days culture.

Ova produced in vitro showed activity but were not tested for infectivity. Abnormalities developed in some cultures, especially in monophasic media.

This work was supported by the Australian Wool Board, the World Health Organization and U.S. Public Health Service Research Grant no. E 4707–03.

The larval trematodes described in this paper were obtained from fresh-water molluscs collected from Rostherne Mere and a pond near Ashley, both in Cheshire. Rostherne Mere is a large sheet of water and carries an extensive fauna, vertebrate and invertebrate. The molluscs were collected from various fixed positions in the littoral region, and this method has confirmed previous observations (unpublished) in other stretches of fresh-water on the variation in the distribution and localisation of infected molluscs. How far this may be related to movements of the final host or to physical factors affecting the migration of the molluscs is at present uncertain; further observations are being made in an attempt to elucidate this problem. The molluscs were isolated in the laboratory in 3 × 1 glass specimen tubes, when the infected specimens were easily seen by the swarming of the cercariae, and all observations (including measurements) were made on these living, fully developed cercariae. Infected snails were later crushed in physiologically normal saline in order to obtain living sporocysts or rediae for examination. Measurements are, of necessity, only approximate owing to the slight pressure exerted by the weight of the cover-glass and the great powers of contraction and extension of these larval forms. Neutral red was used as an intra vitam stain; it also inhibits movement. Of the five species described four are new, the fifth, for which a further stage in the life history is described, being little known and not previously recorded for this country.

The objective of this experiment was to detect a possible interaction between iron deficiency and intestinal nematode infections. We report on a 2×2 study where thirty-one 10-week-old pigs fed a low or a normal iron diet were infected with both Trichuris suis (4500 eggs) and Ascaris suum (1200 eggs). No significant difference was detected between diet groups with respect to parasitological parameters for A. suum or the total number of adult T. suis recovered at necropsy 10 weeks p.i. However, in the low iron group T. suis were located more proximally and the worms were increased in length. A higher proportion of pigs with initial faecal egg excretion at 6 weeks p.i. was observed in the low iron group, indicating a shortened pre-patency period. Worm fecundity and total faecal egg excretion were also highest in the low iron group. A significant correlation was found between female worm length and fecundity. The peripheral eosinophil counts were diminished in the low iron host groups. The infected low iron group experienced more severe pathophysiological changes in terms of hypoalbuminaemia and decreases in erythrocyte volumes. A significant inverse correlation existed between iron content in the bone-marrow and liver (body) store. In conclusion, iron deficiency increased the severity of T. suis infection in pigs.

Binding of promastigotes to the sand fly midgut epithelium is regarded as an essential part of the Leishmania life cycle in the vector. Among Leishmania surface molecules putatively involved in attachment to the sand fly midgut, two GPI-anchored molecules are the most prominent: lipophosphoglycan (LPG) and promastigote surface protease gp63. In this work, we examined midgut attachment of Leishmania lines mutated in GPI-anchored molecules and compared results from 2 different techniques: in vivo development in sand flies and in vitro competitive binding assays using fluorescently labelled parasites. In combination with previous studies, our data provide additional support for (1) an LPG-independent parasite-binding mechanism of Leishmania major within the midgut of the permissive vector Phlebotomus perniciosus, and provide strong support for (2) the crucial role of L. major LPG in specific vector Phlebotomus papatasi, and (3) a role for Leishmania amazonensis gp63 in Lutzomyia longipalpis midgut binding. Moreover, our results suggest a critical role for GPI-anchored proteins and gp63 in Leishmania mexicana attachment to L. longipalpis midguts, as the wild type (WT) line accounted for over 99% of bound parasites.

Deserts represent universally recognized extreme environments for animal life. This paper documents the highly specialized adaptations of Pseudodiplorchis americanus, a monogenean parasite of the desert toad, Scaphiopus couchii. Building on a long-term record of parasite population ecology (continuing since the early 1980s), field studies focus on the effects of severe drought in the Sonoran Desert, Arizona, in the mid 1990s. This provides a test of the ability of the host-parasite system to tolerate exceptional perturbation. The analysis provides new insight into parasite infection dynamics in a natural wildlife system through integration of host and parasite population age structure. The environmental check interrupted host recruitment in 1993–95 and parasite recruitment in 1995–97. This produced an imprint in age structure and infection levels recognizable over several years: parasite recruitment failure reduced transmission 2–3 years later. The host (maximum life span 17 years) tolerated the disruption but the impact was more serious for the parasite (life span 3 years) leading to extinction of some previously stable populations. Despite this demonstration of a rare event exacerbating external environmental constraints, experimental studies suggest that the internal (host) environment normally creates the most severe conditions affecting P. americanus. Only about 3 % of parasites survive from invasion until first reproduction. Post-invasion factors including host immunity, characteristic of most parasite life cycles, constitute a greater constraint upon survival than external conditions, even in a desert environment.

Reservosomes are large membrane-bound organelles found at the posterior end of epimastigote forms of Trypanosoma cruzi, but absent in amastigotes and trypomastigotes. We have transferred bloodstream trypomastigotes to LIT medium supplemented with gold-labelled transferrin in order to analyse, at the ultrastructural level, the occurrence of reservosomes and endocytosis during the trypomastigote to epimastigote differentiation. After 24 h, the trypomastigotes differentiated into amastigotes, which adhered to each other forming large clusters. Electron-dense vesicles were detected close to the Golgi complex in cells with intermediary characteristics between amastigotes and epimastigotes, but typical reservosomes at the posterior cell tip were still absent. Transferrin–gold complexes were observed only bound to the surface of clustered cells. After 72 h, epimastigotes were observed being released from the clusters and free-swimming epimastigotes appeared, containing electron-dense vesicles at their posterior region. Typical reservosomes, labelled with transferrin–gold, were observed only in free-swimming epimastigotes. When fully differentiated epimastigotes were incubated with transferrin–gold complexes and then processed for the immunocytochemical detection of cysteine proteinase, all reservosomes were positive for the enzyme, but co-localization of both markers did not occur in all organelles. Our data demonstrate that in T. cruzi epimastigotes endocytosis is strongly related to reservosome biogenesis during the trypomastigote to epimastigote differentiation process.

This study reports on morphological variability of Eimeria species, which may be given either by drawings or as quantitative data. The drawings may be used to facilitate identification by eye of ‘unknown’ Eimeria specimens, whereas quantitative data may serve as a reference set for identification by multivariate statistical techniques. The morphology of 810 Eimeria specimens was defined in binary (b/w) digital images by pixels of their oocyst outline. A Fourier transform of pixel positions yielded size and shape features. To classify coccidia, the quantitative data were employed in an agglomerative clustering by average linkage algorithm with equal weight assigned to size and shape. An inverse Fourier transform served to reconstruct oocyst outlines, i.e. outlines of average shape and size, from mean values of features in resulting clusters. Clusters were subsequently identified based on their average morphology by comparison with drawings of species in an earlier taxonomical work. Five hundred oocyst outlines were simulated for each cluster representing a species, and shape/size variability was presented in contour diagrams. Differences in species shapes, and correspondence in length and width, were seen after reconstruction by inverse Fourier transform and comparison with earlier studies.

Previous studies have shown that host immunity regulates the fecundity of nematodes. The present study was aimed at clarifying the reversible nature of fecundity in response to changes of immunological status and to determine which effector cells are responsible for compromising fecundity in Heligmosomoides polygyrus. Enhanced fecundity was observed in immunocompromised SCID and nu/nu mice compared to those in the corresponding wild-type mice, with significantly fewer numbers of intrauterine eggs produced in the wild-type than in the immunodeficient mice. When 14-day-old adult worms from BALB/c mice were transplanted into naïve BALB/c mice, their fecundity increased significantly as early as 24 h post-transplantation, but not when they were transferred into immune mice, suggesting the plastic and reversible nature of fecundity in response to changes in host immunological status. In mast cell-deficient W/Wv mice, nematode fecundity was significantly higher than in mast cell-reconstituted W/Wv or +/+ mice. The serum levels of the mast-cell protease mMCP1 were markedly increased in the wild-type as well as the mast cell-reconstituted W/Wv, but not in the W/Wv, SCID, or nu/nu mice during infection. These findings raise the interesting possibility that certain activities of mast cells, either directly or indirectly, regulate parasite fecundity during infection.

Colchicine, a drug which poisons the polymerization of microtubules, was assayed for effects on the invasion of Plasmodium falciparum merozoites into red cells in order to investigate if merozoite microtubules have a function in invasion. Culture conditions and concentrations of colchicine were established where the maturation and rupture of schizonts was unaffected by the drug. This was judged first by light microscopy, including morphology and counts of nuclear particle numbers, then by ultrastructural studies which excluded deranged organellogenesis as a cause of merozoite failure, and finally by diachronic cultures in which both recruitment and loss of schizonts could be counted. Specific invasion inhibition was seen when 10 μM–1 mM colchicine was present. Red cells pre-incubated in colchicine and then washed showed no reduction in their extent of invasion, and neither red cell lysis, sphering nor blebbing were apparent. We conclude that intact microtubules are necessary for successful merozoite function.

An experiment was undertaken to study the effect of dietary carbohydrates with different digestibility on the populations of Oesophagostomum dentatum in the intestinal tract of pigs. Sixty-four worm-free pigs from a specific pathogen-free farm were randomly divided into 8 equal groups. The animals in 4 groups were assigned to a diet with partially undegradable carbohydrates (diet 1), while the pigs in the 4 remaining groups were given a diet with fermentable carbohydrates (diet 2). Diet 1 was comprised of barley flour, oat husk meal, soybean meal, vitamins and minerals and diet 2 of barley flour, inulin and sugar beet fibre, soybean meal, vitamins and minerals. The pigs in 6 of the groups (n = 48) were inoculated with 6000 infective larvae of O. dentatum. To determine O. dentatum populations at the early stage of infection, 16 pigs were slaughtered 3 weeks p.i., while the remaining 4 groups continued on the diets for a further 9 weeks after which they were slaughtered. In a diet cross-over experiment 6 weeks after inoculation, 8 pigs changed from diet 1 to diet 2 (diet 1>diet 2), and 8 pigs from diet 2 to diet 1 (diet 2>diet 1). The results showed that partially undegradable carbohydrates provided favourable conditions not only for parasite establishment and sustainability, but also for already established O. dentatum infection while, in contrast, the diet composed of highly degradable carbohydrates decreased worm establishment, size and female fecundity. The implications for pastured pigs or pigs fed different complex carbohydrate diets is discussed.

The distribution of nitric oxide synthase (NOS) immunoreactivity and putative NOS activity in adult Schistosoma mansoni was analysed using 3 different types of NOS antibodies and NADPH-diaphorase histochemistry. Although potential involvement of the gaseous radical nitric oxide (NO) in host response to infection by schistosomes has been suggested, there is little or no information available regarding the role, or even the presence, of the NO pathway in schistosomes themselves. Here, we demonstrate that antibodies against neuronal NOS (nNOS) and inducible NOS (iNOS) isoforms stain adult worms with distinctive patterns; anti-endothelial NOS (eNOS) shows no selective labelling. nNOS-like immunoreactivity is found in the main nerve cords and the peripheral nervous system. Putative sensory neurons with apical neuronal processes leading to the tegument of male worms are also immunoreactive for nNOS. Anti-iNOS labels a variety of predominantly non-neuronal tissues, showing intense labelling at or near the surface of the worm and in components of the gastrointestinal tract. The distribution of NADPH-diaphorase reactivity (a histochemical marker of NOS), is generally similar to the pattern of NOS immunoreactivity, including labelling of neuronal-like cells as well as developing eggs. These results suggest that an NOS-like enzyme is present in S. mansoni, and indicate potential roles for the different NOS isoforms in neuronal signalling, reproduction and development.

Actively immunized mice, whole-body irradiated with 650 or 525 rad., manifested comparable levels of resistance to Schistosoma mansoni compared with unirradiated, immunized mice in spite of a marked reduction in circulating leucocytes (>90%) and platelets (>85%), and despite an abrogation of delayed-type hypersensitivity (DTH) (Type IV) response to schistosomular antigens (as determined by footpad swelling, 24 h after injection of antigen). However, limited histopathological comparison of lung sections from irradiated and unirradiated mice 7 days post-challenge showed that cellular reactions (‘foci’) around parasites were essentially similar in size and cellular composition except that in irradiated mice, eosinophils were poorly represented both in the foci and in lung tissue in general. Neither presumed immune complex-mediated (Type III, Arthus reaction) hypersensitivity (as determined by footpad swelling, 5 h after injection of antigen) nor serum anti-schistosomulum extract antibody levels (as determined by ELISA) were affected. In addition, the pattern of 125I-labelled schistosomular surface antigens immunoprecipitated with serum from irradiated and unirradiated mice was essentially similar. These results are consistent with antibody playing an important role in vaccine-induced immunity in mice but suggest that radiosensitive T cell function and radiosensitive cells, such as platelets and polymorphonuclear cells, including eosinophils, may not be essential.

The thoracic lymph duct of rats infected with Trypanosoma brucei and with T. congolense was cannulated at different stages of infection. Trypanosomes were always present in the lymph of rats infected with T. brucei, whereas they were absent or very scarce in the lymph of rats infected with T. congolense. There were greater fluctuations in the numbers of trypanosomes in the blood than in the lymph. The intra- and extravascular populations of T. brucei differed: stumpy forms were present only in blood; dividing forms were usually more numerous in lymph.

The electrophysiological properties of the bag region of the somatic muscle cells of Ascaris suum and Ascaridia galli were studied using intracellular techniques. For Ascaris muscle cells, the mean resting membrane potentials at 20 and 37°C were −29·9 and −33·8 mV respectively, and the average input conductance was 2·12 μS. For the muscle cells of A. galli similar values were obtained. For example, the mean input conductance of these cells was 2·84 μS at 20°C. Healthy Ascaris muscle cells at near physiological temperatures show both spontaneous depolarizing and hyperpolarizing activity and, in cells close to the nerve cords, rhythmic large amplitude (approximately 30 mV) action potentials are observed. Such action potentials, which are very sensitive to temperature variations, originate in the muscle cells. In contrast the muscle cells of Ascaridia are quiescent. The rhythmic action potentials of Ascaris are resistant to tetrodotoxin (TTX) (≤ 10−6 M), verapamil (10−4 M) and cinnarizine (10−4 M), but are blocked irreversibly by 22, 23 dihydroavermectin B1a (10−7 to 5 × 10−6 M). GABA, and the GABAA receptor agonists, muscimol and isoguvacine, hyperpolarize and increase the input conductance of both Ascaris and Ascaridia muscle cells. The antagonists+bicuculline and picrotoxin were not effective in modulating the spontaneous hyper polarizations of Ascaris muscle cells, and picrotoxin (10−4 M) was not effective in altering the response to GABA (5 × 10−6 M). The significance of the results is discussed briefly.

Some effects of insemination on Moniliformis dubius were studied by means of a surgical technique involving the transplantation of worms of known age, sex and reproductive state from one male rat to another. Insemination resulting in the development of eggs was found to have occurred in female M. dubius aged 16 days. An individual male M. dubius was found to be capable of inseminating as many as 17 females of the same age. The duration of the patent period appeared to be related to the length of the period of contact between male and female worms at the start of the course of infection. The evidence indicated that the patent period of a female worm was curtailed in cases where the female was isolated from males sooner than 5 weeks after the start of the infection. Male worms estimated to be not more than 21 days old were found to be capable of inseminating females older than 100 days; in these cases, the patent period was brief. Evidence was obtained to suggest that insemination is followed by further growth of the somatic tissues of the female worms. These results apply to experimental infections, and caution should be exercised in applying them directly to natural infections.

Acanthobothrium quadripartitum, a tapeworm parasitic in the intestine of Raja naevus, is not found in the closely related R. radiata. The tapeworm survives in vitro for over 24 h in fresh serum from the natural host, but fresh serum from R. radiata is extremely toxic; about 80% are killed within 2 h with the formation of a characteristic external precipitate. The toxicity of fresh R. radiata serum was abolished by procedures known to inactivate complement and restored by the addition of fresh serum from the natural host R. naevus. This observation suggests that both species of ray possess a similar complement system in fresh serum but only R. radiata contains a natural serum antibody toxic to A. quadripartitum. No toxicity could be demonstrated in R. radiata mucous in vitro, probably due to the serum factors being present in low concentrations.

The results are discussed in relation to the observed inability of A. quadripartitum to survive in the intestine of R. radiata.

1. All the bacilli hitherto investigated, when growing on the surface or in the depth of agar, exhibit “post-fission” movements after division.

2. Four types of post-fission movement have been noticed, which may be termed “loop-forming,” “folding,” “snapping” and “slipping.”

3. These types of post-fission movement seem to depend on the strength, adherence and mode of rupture of the capsule. In the “loop-forming” group the capsule is very strong and adherent and is very seldom ruptured. In the “folding” group the portion of the capsule uniting the adjacent bacilli in the chain is long and flexible. In the “snapping-group” the capsule seems to undergo partial rupture at the time of division, and in the “slipping” group it is completely ruptured.

4. “Loop-forming” post-fission movements are shown by B. anthracis, “folding” by B. pestis and certain organisms morphologically resembling B. anthracis, “snapping” by all diphtheroid organisms and “slipping” by organisms belonging to the typhoid-enteritidis-colon group, vibrios, the butter bacillus (Rabinowitch), B. pyocyaneus, B. fiuorescens, B. subtilis and allied organisms and many non-pathogenic species.

5. The characters of the colonies formed by organisms exhibiting loop-forming, folding and snapping post-fission movements are not markedly altered by the condition of medium under ordinary conditions of cultivation. When thickly sown on moist agar continuous growths are formed by all of them, but the edges of these growths resemble the edges of the separate colonies. All organisms exhibiting slipping post-fission movements form films on moist agar. Under unsuitable conditions for film formation the larger and stronger members produce either colonies with radiating processes on moderately moist agar, or rounded colonies on dry agar. The smaller, weaker, and slower growing members produce colonies which to the naked eye appear more or less rounded.

The monogenetic trematodes have long been known as parasites of the lower aquatic vertebrates and many forms have been described from fishes, amphibians, and reptiles. They are largely ectoparasitic, although a few members of the group infest the oronasal cavities and urinary bladder of frogs and turtles. Up to the present there appears to be no record of their occurrence on either birds or mammals and consequently the unusual case here reported seems worthy of note. The material consists of five polystomes which bore the label, “from the eye of hippopotamus.” Presumably they were collected by the late Professor A. Looss from a Nile hippopotamus in the Giza Zoological Gardens of Cairo, Egypt, but unfortunately no particulars are available. The specimens were given to me for identification by Dr Edward Hindle, recently Professor of Biology, School of Medicine, Cairo, to whom I wish here to express my thanks. Grateful acknowledgments are due also to Professor George H. F. Nuttall, Director of the Molteno Institute for Research in Parasitology, where the study was made.

1. Aphidius matricariae Hal. is an internal parasite of Myzus persicae Sulz.; it was also found parasitizing M. circumflexus Buckt. and Aulacorthum solani Kalt. (Myzus pseudosolani Theob.).

2. The percentage of aphides successfully parasitized increased with an increased number of strikes per host. A single female can lay up to 350 eggs, and one female successfully parasitized 309 M. persicae.

3. The female parasite reaches its maximum activity during the 2nd or 3rd day of oviposition, and this activity has no correlation with light intensity.

4. The disappearance of supernumerary larvae due to cannibalism has been observed.

5. The species is arrhenotokous. Mating takes place from 2 hr. after emergence. In the progeny of early matings the females preponderated; in later matings the sex ratio was approximately 1:1.

6. The parasite appears to fly under the same conditions as those generally favourable for aphides. It is generally disseminated by flight of the adult itself and through localized movements of parasitized apterous aphides.

7. The host is unable to reproduce if ‘struck’ in the 3rd instar or earlier.