A single dose of Ro 11–3128 was found to be 98–100% effective against Schistosoma mansoni infections at intervals of 3 h to 15 days following infection, and apparently killed the schistosomula stages soon after administration, thus allowing an assessment of the immunizing potential of progressive larval stages. Following infection with 500 unirradiated cercariae, optimum resistance was manifest by groups drug-treated at 48–96 h (60–75%). Significantly lower levels of resistance occurred with early (3 h) or later (6–15 day) treatments. Superimposition of an infection treated at 15 days on a prior infection which had been treated at 2 days did not reduce the level of resistance caused by the latter, indicating that the infection plus delayed treatment had not induced suppression. Thus the peak resistance manifest during the 48–96 h period may reflect optimum expression of protective antigens. Comparison of irradiated (20 krad.) with unirradiated infections showed that, when drug-terminated 24, 48 or 96 h post-infection, irradiated cercariae induced significantly less resistance than unirradiated cercariae, perhaps indicating a delayed appearance of protective antigens following radiation treatment.

The Gyrocotylidea is a group of platyhelminths comprising only a dozen or so species which have been placed in three genera, Oyrocotyle Diesing, 1850, Amphiptyches Grube and Wagener in Wagener, 1852 and Gyrocotyloides Fuhrmann, 1930. All species are highly specific to chimaeroid fish, a small group of present-day holocephalans, and are restricted to the spiral valve intestine of these hosts.

Adult Fasciola hepatica were incubated for 48 h in vitro in the synthetic peroxide, OZ78 at a concentration of 100 μg/ml and then prepared for scanning and transmission electron microscopy. There was limited disruption to the external fluke surface, with only slight swelling and blebbing of the interspinal tegument in the midbody and ventral tail regions. By contrast, significant disruption was observed to the ultrastructure of the tegument and subtegumental tissues. There was severe swelling of the basal infolds in the tegumental syncytium and the flooding spread internally to affect the subtegumental tissues. In the tegumental system, there was swelling of the cisternae of granular endoplasmic reticulum and of the mitochondria, with the latter showing signs of breaking down. Autophagic vacuoles and lipid droplets were present and the synthesis of tegumental secretory bodies was much reduced. The gastrodermal cells were severely affected, with swelling and degeneration of the mitochondria and the presence of autophagic vacuoles and lipid droplets. The granular endoplasmic reticulum was swollen and vesiculated and the cells contained few secretory bodies. Both the vitelline and testis follicles showed evidence of extensive cellular disruption and degeneration. This study confirms previous data indicating the potential flukicidal activity of OZ78.

The description of Sphyranura oligorchis (Alvey, 1933) and S. polyorchis n.sp. is presented together with an account of the development of the former. Study of the life history of S. oligorchis, and a review of the literature on the life cycles of the Monogenea, show that at a corresponding time in their development embryonic stages similar to Dactylogyrus are present. It is postulated that Dactylogyrus is near the primitive ancestral type of the Monogenea, and that all of the parasitic platyheminthes may have arisen from a common planula ancestor.

A large Babesia species was found in a leopard (Panthera pardus) in Kenya. It was established in domestic cats but no other animal was found to be susceptible. The parasite has been compared with other piroplasms of felids and it was found to differ from them in some significant characters. It was established as a new species and named Babesia pantherae.

We would like to thank Miss B. O. Vidler for her assistance, Dr S. F. Barnett for many helpful discussions and Professor N. D. Levine for pointing out the need for this description.

The parasite was isolated when we were working at the East African Veterinary Research Organization at Muguga in Kenya and we are most grateful to that organization for facilities.

The Ascarids parasitic in snakes present considerable difficulties from the systematic point of view, owing to the incomplete character of many of the descriptions, and to the state of confusion which has long existed in the nomenclature. The writer has made an attempt, by examining such material as was available, and by comparing a number of the existing descriptions, to clear up some of this confusion. It was hoped also that such a comparative treatment would throw some light on the systematic value of the modifications of the female genital apparatus, which occur in some of these forms.

The host–parasite interaction between the rainbow trout Oncorhynchus mykiss and the fish louse Argulus japonicus was investigated by administering low levels of dietary cortisol before infecting the fish with low numbers of the parasite. After 24 h, the dietary cortisol treatment elevated blood cortisol and glucose levels and stimulated the synthesis of secretory granules in the upper layer of skin cells. Infection with 6 lice per fish caused skin infiltration by lymphocytes, also in areas without parasites. The lymphocyte numbers in the blood at 48 h post-parasite infection were reduced. Other changes, typical for exposure to many stressors and mediated by cortisol, were also found in the epidermis of parasitized fish, although neither plasma cortisol nor glucose levels were noticeably affected. Glucocorticoid receptors were localized immunohistochemically and found in the upper epidermal layer of pavement and filament cells, and in the leucocytes migrating in these layers. Cortisol-fed fish had reduced numbers of parasites and the changes in the host skin are likely involved in this reduction. Thus a mild cortisol stress response might be adaptive in rejecting these parasites. Further, the data suggest that this effect of cortisol is mediated by the glucocorticoid receptor in the skin epidermis, as these are located directly at the site of parasite attachment and feeding in the upper skin cells that produce more secretory granules in response to cortisol feeding.

During the course of Schistosoma mansoni murine infection there is a dramatic increase of some immunoglobulins and S. mansoni-specinc antibodies. The most substantial response is initiated after 40 days of infection and results in a prolonged increase of total IgG1; IgM and IgA. The maximum increase is respectively 26, 14 and 3-fold the basic immunoglobulin level in control mice. Some anti-S. mansoni classes and sub-classes were studied by an original radio-immunoadsorbent test. Anti-S. mansoni IgG1 and IgM antibodies appear and increase at the same time as that of total IgG1 and IgM. Anti-S. mansoni IgA antibodies appear later (80th day) and correspond to a second peak of total IgA.

Introduction. Leishmania donovani, the causative agent of visceral leishmaniasis in the Indian subcontinent, has been reported to be genetically homogeneous. In order to support ongoing initiatives to eliminate the disease, highly discriminative tools are required for documenting the parasite population and dynamics. Methods. Thirty-four clinical isolates of L. donovani from Nepal were analysed on the basis of size and restriction endonuclease polymorphisms of PCR amplicons from kinetoplast minicircle DNA, 5 nuclear microsatellites, and nuclear loci encoding glycoprotein 63, cysteine proteinase B, and hydrophilic acylated surface protein B. We present and validate a procedure allowing standardized analysis of kDNA fingerprint patterns. Results. Our results show that parasites are best discriminated on the basis of kinetoplast minicircle DNA (14 genotypes) and 1 microsatellite defining 7 genotypes, while the remaining markers discriminated 2 groups or were monomorphic. Combination of all nuclear markers revealed 8 genotypes, while extension with kDNA data yielded 18 genotypes. Conclusion. We present tools that allow discrimination of closely related L. donovani strains circulating in the Terai region of Nepal. These can be used to study the micro-epidemiology of parasite populations, determine the geographical origin of infections, distinguish relapses from re-infection, and monitor the spread of particular variants.

It has recently been shown (Smith & Wyckoff, 1950) that, in addition to the classical type of nuclear polyhedral disease of lepidopterous larvae, there exists a second type of polyhedrosis with spherical virus particles instead of rods. This was demonstrated in the case of two tiger-moth larvae, Arctia villica and A. caja. The polyhedra of this type of disease do not dissolve fully when treated with weak alkali but leave behind a honeycomb-like shell pitted with round holes. We have also shown (Xeros, 1952, Smith & Xeros, 1953a) that in all our material these polyhedra occur in the cytoplasm and not in the nuclei and are confined to the cells of the midgut.

Sera from rabbits, rats and mice multiply-vaccinated with attenuated cercariae of Schistosoma japonicum conferred high levels of resistance against challenge to naive recipient mice (up to 97, 64 and 60% respectively). Vaccinated rabbit and rat sera were given before challenge and vaccinated mouse serum 5 days after challenge. To show that the protective factors in these sera were antibodies, vaccinated rabbit and mouse sera were fractionated by protein A-Sepharose and the fractions precipitated by 50% ammonium sulphate. The protein A-Sepharose binding or non-binding fractions in vaccinated rabbit serum transferred approximately equal levels of significant resistance to mice, suggesting that both the IgG and non-IgG components of vaccinated rabbit serum are protective. The major part of the protective activity in vaccinated mouse serum was transferred to recipients by the protein A-Sepharose binding fraction, i.e. the IgG antibodies. Heat inactivation of sera at 56 °C for 3 h affected the protective capacity of vaccinated rat sera, but not that of vaccinated rabbit or mouse sera.

Density-dependent effects of Anguillicola crassus larval infections in the copepod intermediate host were examined experimentally. Three species of copepods (Cyclops vicinus, C. viridis and C. fuscus) were subjected to a range of doses of larval A. crassus within infection arenas. Prevalence, intensity and parasite dispersion (variance: mean abundance) values increase and then approach an asymptote as infection dose increases. Infection parameters differ between species of copepod. Increasing temperature has a negative effect on the establishment of the parasite population within the intermediate host. Parasite-induced host mortality increases with dose. These mechanisms have the potential to regulate populations of A. crassus larvae within the copepod population and hence the whole suprapopulation.

Interactions between infections of Trichinella spiralis and Nippostrongylus brasiliensis were studied in the NIH strain of mouse which is known to react strongly to T. spiralis. The course of N. brasiliensis infection in this strain of mouse is described and expulsion is shown to be accelerated in immunized mice and inhibited in cortisone-treated mice. There was no evidence of inter-specific competition between the two species of worm in concurrent infections; the number and location of adults of both species were normal and T. spiralis was able to grow and reproduce normally. No evidence was found of direct immunological cross-reaction between N. brasiliensis and T. spiralis as assessed by the kinetics of adult worm numbers on heterologous challenge of immunized mice 90 days after the initiation of the last of 3 immunizing infections. Interaction was observed only when the timing of concurrent infections was such that one species was established in the intestine immediately before the beginning of expulsion of the second species. Interaction was manifested as a premature loss of worms and, in addition, as impairment of growth and fecundity of T. spiralis. These effects on T. spiralis were similar to those observed as a consequence of a specific immune response to T. spiralis. The rapidity of appearance of these effects and the lack of direct cross-immunity between the two species of worm suggest that the events involved in interaction were non-specific in action and possibly due to environmental changes in the gut caused by the immune response. These non-specific effects are therefore analogous, but not necessarily homologous, to the expulsion of these parasites in single species infections.

The activities of glucose-6-phosphatase (G6Pase), frucrose-1,6-bisphosphatase (FBPase), phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC) were determined in homogenates of adult Schistosoma mansoni worms and compared with the activities in homogenates of rat liver and rat skeletal muscle, tissues with a high and a low gluconeogenic capacity, respectively. All four gluconeogenic enzymes were present in S. mansoni. The enzymes were less active than in rat liver, but the activities of G6Pase, PEPCK and PC were at least an order of magnitude higher than in rat skeletal muscle whereas FBPase was approximately equally active in S. mansoni and in rat muscle. Experiments with 14C-labelled substrates or [14C]NaHCO3 failed to demonstrate the actual occurrence of gluconeogenesis in S. mansoni. Some possible other functions of the gluconeogenic enzymes were investigated. Experiments with inhibitors of PEPCK gave no indications that this enzyme was involved in the degradation of glucose. This was confirmed by 13C-NMR experiments which indicated that lactate was formed from phosphoenolpyruvate via the actions of pyruvate kinase and lactate dehydrogenase, and that PEPCK did not participate in the formation of lactate. Substrate cycling between fructose-6-phosphate and fructose-1,6-bisphosphate was demonstrated to occur in adult S. mansoni. This shows that FBPase participates in the glucose metabolism of this parasite.

A new genus, Kuhnia n.g., is created for the mazocraeidid monogenetic trematodes from the gills of mackerel. The type species, K. scombri (Kuhn), is redescribed (also K. minor (Goto), from the first specimens to be found outside Japanese waters), special attention being paid to the cuticularized parts, and the clamp skeleton is newly interpreted.

An alternation of sex phases has been found in Monogenea, which is well marked in K. scombri, resulting in changes in appearance which are described.

The comparison of heterauxesis curves constructed from the summarized data from six sets of dimensions shows that retardations in the rates of growth may be correlated with the onset of maximal reproductive activity, and accelerations with the relief from reproductive drain. Localized growth influence (similar shaped curves, with low post-larval coefficients of growth) has been found in the haptoral region, which is in marked contrast to the growth picture of the cuticularized oral suckers and the width of the body—the latter having both the highest and most variable growth coefficients between the six arbitrary length groups compared. Thus, neither absolute measurements nor ratios are, by themselves, of any value in specific diagnosis.

Graphical representation of allomorphosis for the genus Kuhnia affords a synoptic view of the changes brought about by the different types of differential growth of similar organs in each species throughout post-larval life. The dissimilar growth coefficients for certain dimensions are utilized in specific diagnosis. The relative diagnostic value of different entities is examined: the eggs of K. scombri are shown to be highly variable in size and shape.

The new facts obtained from the application of this metrical treatment, and its further application as a test for conspecificity of specimens outside the known size range, are discussed.

The systematics of the family Mazocraeidae are reviewed, and emended diagnoses of three species of Kuhnia are given in tabular form.

The structure and function of the vacuoles in the eggs of Schistosoma mansoni is unknown. In this study the eggs have been immersed in serum albumin and examined by phase-contrast optics. Under these conditions the vacuoles exhibit a definite internal structure, suggesting that they may be or may have been cellular. Histochemical staining techniques to detect the nature of the vacuolar contents revealed that the vacuoles stained heavily with iodine and gave a positive PAS reaction. This suggested the presence of carbohydrate. Stains for nucleic acids, protein and lipid were not taken up by the vacuoles. The egg shell stained with o–toluidine blue and with basic fuchsin uniformly, except for a thin irregular band which might indicate a possible line of weakness. The vacuolar membranes seem to be similar to the vitelline membrane in permeability to hydroxyl ions and it is possible that these membranes have a common origin. Plasmolysis studies with salts, urea, glycerol and sucrose showed that the vacuolar membranes have about the same permeability properties to these compounds as the other egg membranes. Glycerol treatment of the eggs until equilibrium is attained, followed by transfer of the eggs to water or saline results in a hatching of the eggs. In this, a dead mira-cidium is extruded from the shell. Similar treatment of eggs equilibrated with sucrose does not result in this hatching process. It is postulated that glycerol solubilizes a factor which aids the hatching process.

I should like to thank the following: Dr S. A. Ibrahim, in whose department this work was carried out; Dr S. Dawood of the Stack Laboratory, Khartoum, who kindly made his microscope available for use; Mr J. R. Lauder for valuable discussions and suggestions; and many young patients in Khartoum Civil Hospital for stool samples and smiles.

The electrophoretic mobility of glucose phosphate isomerase (GPI) has been used to identify Eimeria acervulina, E. praecox and E. mivati in isolates of coccidia from commercial sites in the United Kingdom. Mixtures of two or three species gave separate bands upon electrophoresis and each species could be identified provided that it formed at least 10–20% of the total number of oocysts present in a sample of 8 × 106 oocysts. The principal forms of GPI corresponded to the GPI of E. acervulina (H), E. praecox (H) and E. mivati (W) and were found in 38, 34 and 8 isolates respectively of the 46 examined. Three further variants of GPI are described.

The development of the male reproductive system in Gyrodactylus gasterostei has been followed using parasites of known age maintained on isolated hosts. The penis develops shortly after the parasite has given birth for the first time (at an age of 24–30 h at 13°C) and the first active spermatozoa appear after 40–50 h. Spermatogenesis occurs more rapidly in G. gasterostei than in any other parasitic flatworm (including those from warm-blooded hosts) in which it has been measured, and the onset of male maturity is further hastened by a reduction in the number of pre-spermatogenic germ cell divisions. Spermatogonia have a diploid chromosome complement of 12, and spermatocytes undergo meiosis to produce haploid spermatozoa. No evidence of aneuploidy in spermatozoa was obtained. Although the development of haploid spermatozoa suggests that sexual reproduction can occur, production of embryos by isolated flukes which lack a mature male system indicates that other means of reproduction may also be employed.

Amoebae were isolated from contact lenses of a symptomatic lens wearer in Spain. Protozoa were characterized by studying their morphology, biology, protease activity and the 18S rRNA gene sequence. Morphology of the organism was observed by light microscopy, scanning electron microscopy and transmission electron microscopy. Its structure corresponded to an amphizoic amoeba. The protozoa grew well at 37 °C and poorly at lower temperatures. In addition, it was capable of lysing mammalian cells in vitro. A major 56 kDa proteolytic enzyme was observed in amoeba crude extracts by gelatin–sodium dodecyl sulphate–polyacrylamide gel electrophoresis. Most proteolytic enzymes in protozoa extracts showed significant activity over a wide range of pH (3–9) and temperature (8–45 °C) values. The assays on inhibition of protease activity indicated strongly that enzymes detected in amoeba extracts corresponded to serine proteases and, to a lesser extent, cysteine proteases. The use of proteinase inhibitors on a tissue culture model proved that the proteinase activity is critical for developing focal lesions in HeLa cell monolayers. Finally, partial sequencing of the 18S ribosomal RNA gene and phylogenetic analyses indicated that the isolate is closely related to Acanthamoeba griffini H37 from the UK (T3 genotype).

In non-permanent parasites with low intrinsic mobility such as ticks, dispersal is highly dependent on host movements as well as the timing of separation from the hosts. Optimal detachment behaviour is all the more crucial in nidicolous ticks as the risk of detaching in non-suitable habitat is high. In this study, we experimentally investigated the detachment behaviour of Ixodes arboricola, a nidicolous tick that primarily infests birds roosting in tree-holes. We infested great tits with I. arboricola larvae or nymphs, and submitted the birds to 2 experimental treatments, a control treatment in which birds had normal access to nest boxes and an experimental treatment, in which the birds were prevented access to their nest boxes for varying lengths of time. In the control group, most ticks detached within 5 days, whereas in the experimental group, ticks remained on the bird for as long as the bird was prevented access (up to 14 days). This prolonged attachment caused a decrease in survival and engorgement weight in nymphs, but not in larvae. The capacity of I. arboricola larvae to extend the duration of attachment in non-suitable environments with no apparent costs, may be an adaptation to unpredictable use of cavities by roosting hosts during winter, and at the same time may facilitate dispersal of the larval instars.