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.

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.

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.

Ciné film and direct observation showed that microphagous, plant and animal nematodes have the same basic wave pattern when moving. Their speed is linearly related to the product of their length and wave frequency during unrestricted movement in deep water. The speed, wave pattern and frequency of the plant nematode Ditylenchus dipsaci and the animal nematode Trichostrongylus colubriformis changed in a similar way in response to changes in water film thickness on the surface of agar of different concentrations. T. colubriformis like D. dipsaci were most mobile in a sand-water medium at a suction corresponding to the stage when most of the water has drained from the pores. The optimum temperature for activity of T. colubriformis and D. dipsaci was about 20° C. and both survived desiccation at 50% relative humidity and 24° C. for 32 days. T. colubriformis was attracted to and aggregated around grass roots (Phleum pratense). The results suggest that the free-living stages of microphagous, plant parasitic and animal parasitic nematodes move similarly and that nematodes can be divided arbitrarily into three groups: (1) those active enough to swim in deep water; (2) those able to swim in thick water films, escape from the soil and ascend plants above ground level; and (3) those too inactive to swim, the crawlers, which are largely confined to the soil. The habitat of free-living stages of nematodes, irrespective of their host or feeding habits, is probably related to their propulsive power.

We thank Dr D. Poynter for supplying the animal parasites used.

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.

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.

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.

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.

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.

1. History of the classification of the family Metastrongylidae is briefly reviewed.

2. The probable origin of the family is discussed. It is believed that the metastrongylids arose, in common with the family Strongylidae, from a primitive group of eustomatous, cloacinin-like, gastro-intestinal strongylines that were symbiotic with an ancestral mammalian group, possibly the pantotheres. One group of these symbiotes established itself in the mammalian respiratory tract and originated the metastrongylid line.

3. The family Trichostrongylidae is regarded as of common origin with the family Ancylostomatidae from eustomatous ancestors. Thus meiostomy in the metastrongylids and trichostrongylids is convergent.

4. The Metastrongylidae consist of three main lines, each characteristic of a placentate order: the Filaroidinae in the Carnivora, the Pseudaliinae in the Cetacea, and the Protostrongylinae in the Artiodactyla. These lines probably have evolved from a common ancestor, symbiotic with a host at the base of the carnivore-cetacean-ariodactyl radiation. Certain forms have become secondarily adapted to symbiosis with members of other placentate orders.

5. Morphological and biological evidence is given for each of the foregoing phylogenetic conclusions.

6. Metastrongylus Molin, 1861, is regarded as a relict genus. With it, in a subfamily Metastrongy-linae, is placed the genus Heterostrongylus Travassos, 1925.

7. Heterostrongylus is represented by a single known species, H. heterostrongylus Travassos, 1925, from an opossum (order Marsupialia). Morphologically it is primitive with cloacinin-like cephalic features. In view of the phylogenetic status of its host it may well represent an ancestral type that has evolved along with the Marsupialia from a common ancestry with the other metastrongylids, probably in the panthotheres. As yet unknown lungworms of marsupials may shed light on this interesting point.

8. Diagnoses are given for the family Metastrongylidae and its subfamilies; the twenty-two component genera are listed under the latter. New synonymies are made: Neometastrongylus Kreis, 1944, a synonym of Neostrongylus Gebauer, 1932; Neometastrongylus buechii Kreis, 1944, of Neostrongylus linearis (Marotel, 1913) Gebauer, 1932; and Otophocaenurus Skriabin, 1942, of Pharurus Leuckart, 1848. Otophocaenurus oserskoi Skriabin, 1942, becomes Pharurus oserskaiaae (Skriabin, 1942, n.emend.) n.comb.; Metathelazia massino becomes M. massinoi (Davtian in Skriabin, 1933, n.emend.) Dougherty, 1943.

A protocol for dissociating single muscle fibres from intact flatworms was developed. Muscle fragments of various sizes were obtained, many with their cell bodies, or myocytons, intact. Many of the fibres were spontaneously contractile, and they and others contracted in response to applications of transmitter candidates, activators of protein kinase C and the anthelmintic praziquantel. The responses were all similar to those evoked in strips of tissue. Voltage clamp recordings from the isolated muscle fibres revealed that they possess an inward Ca2+ current and 3 separate K+ currents. These results indicate that muscle fibres in Bdelloura bear receptors for neurotransmitters and that preparations of dispersed muscle fibres can be used for studying the basic physiological and pharmacological properties of platyhelminth muscle.

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.

An account is given of a virus which is present in the roots of a number of different plants. Plants which have been shown, so far, to contain the infective principle in the roots are several members of the Solanaceae, tomatoes, tobacco, etc.; of the Primulaceae, Polyanthus sp. and Primula obconica; of the Geraniaceae, zonal Pelargonium; and of the Compositae, the aster. Such plants show no indication of infection with the exception of Nicotiana tabacum and N. glutinosa, which may develop natural disease symptoms. These symptoms are usually confined to the two lowermost leaves and develop most frequently under conditions of low temperature and low light intensity. The virus never becomes completely systemic in any host plant and is generally restricted to the inoculated leaves. Experiments are described which show the virus to be present in the roots of tobacco plants which had given a negative virus reaction a few weeks earlier. The virus is found in the roots of tobacco plants arising from seed which has been heated to a temperature of 75° C., the thermal death-point of the virus in expressed sap being 72° C. All attempts to demonstrate the presence of the virus in the seed have proved negative.

Although no systematic study has been made, the range of plants susceptible to local infection in the leaves, by artificial inoculation, seems wide. Tests have shown that about 25 species of plants belonging to 10 families respond to inoculation with the virus.

Three possible explanations of the origin and spread of the infection are discussed.

Severe adverse events (SAEs) following ivermectin treatment may occur in people harbouring high Loa loa microfilarial (mf) densities. In the context of mass ivermectin distribution for onchocerciasis control in Africa, it is crucial to define precisely the geographical distribution of L. loa in relation to that of Onchocerca volvulus and predict the prevalence of heavy infections. To this end, we analysed the distribution of mf loads in 4183 individuals living in 36 villages of central Cameroon. Mf loads were assessed quantitatively by calibrated blood smears, collected prior to ivermectin distribution. We explored the pattern of L. loa mf aggregation by fitting the (zero-truncated) negative binomial distribution and estimating its overdispersion parameter k by maximum likelihood. The value of k varied around 0·3 independently of mf intensity, host age, village and endemicity level. Based on these results, we developed a semi-empirical model to predict the prevalence of heavy L. loa mf loads in a community given its overall mf prevalence. If validated at the continental scale and linked to predictive spatial models of loiasis distribution, this approach would be particularly useful for optimizing the identification of areas at risk of SAEs and providing estimates of populations at risk in localities where L. loa and O. volvulus are co-endemic.

Life-history attributes of the capsalid monogenean Benedenia lutjani, a parasite of Lutjanus carponotatus from the Great Barrier Reef, Queensland, Australia, were investigated from experimental infections. Oncomiracidia of B. lutjani invaded and attached at any site on the fish, but more commonly invaded body surfaces. Immature specimens then migrated to the pelvic fins. Development of the reproductive organs of B. lutjani corresponded with migratory movements on the host. Parasite aggregation on the pelvic fins coincided with the development of functional male reproductive organs and some protandrous worms that possessed a vagina appeared to be inseminated. Migration to, and aggregation on, the branchiostegal membranes (membranous folds posterior to the opercula) coincided with the onset of sexual maturity and commencement of egg production by parasites. The rate of parasite development and the timing of migratory events on the host were influenced by water temperature. All specimens of B. lutjani reached sexual maturity between 12 and 14 days p.i. at 24 °C and between 8 and 10 days p.i. at 27 °C. Anterior hamuli grew continually during a 16-day experiment at 27 °C and 25-day experiment at 23 °C and their length appeared to provide a suitable index to estimate parasite age. The possible adaptive significance of the migratory behaviour, site-specificity and its link with changes in parasite development are discussed.

The phylogenetic relationship of 5 genera, i.e. Diplozoon Nordmann, 1832, ParadiplozoonAchmerov, 1974, InustiatusKhotenovsky, 1978, SindiplozoonKhotenovsky, 1981, and EudiplozoonKhotenovsky, 1985 in the subfamily Diplozoinae Palombi, 1949 (Monogenea, Polyopisthocotylea) was inferred from rDNA ITS-2 region using neighbour-joining (NJ), maximum likelihood (ML) and Bayesian methods. The phylogenetic trees produced by using NJ, ML and Bayesian methods exhibit essentially the same topology. Surprisingly, freshwater species of Paradiplozoon from Europe clustered together with species of Diplozoon, but separated from Chinese Paradiplozoon species. The results of molecular phylogeny and lower level of divergence (4·1–15·7%) in ITS-2 rDNA among Paradiplozoon from Europe and Diplozoon and, on the other hand, high level of divergence (45·3–53·7%) among Paradiplozoon species from Europe and China might indicate the non-monophyletic origin of the genus Paradiplozoon. Also, the generic status of European Paradiplozoon needs to be revised. The species of Paradiplozoon in China is a basal group in Diplozoinae as revealed by NJ and Bayesian methods, and Sindiplozoon appears to be closely related to European Paradiplozoon and Diplozoon with their relationship to Eudiplozoon and Inustiatus being unresolved.

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.

The relevance of spatial variation in the environment and host communities for parasite community composition is poorly documented, creating a need for additional case studies from which general principles can be developed. Avian malaria in southern African waterfowl has not previously been studied. As a first step towards documenting and understanding its biogeography, we used PCR and molecular sequencing techniques to analyse 454 blood samples from Afrotropical ducks from 5 different locations (spread around the subregion) for avian malaria. Fifty-five blood samples were positive for one or more genera of haematozoa. The regional infection rate across all sites and sampling periods was 12·1%. Nine individuals carried dual infections containing multiple haematozoa. Fifteen different cytochrome b haplotypes among 52 positives (3 samples failed to sequence) and 61 total sequences were found. Eleven haplotypes closely matched Plasmodium, whereas 4 were more similar to Haemoproteus. Five distinct haematozoan clades were identified. Haemoproteus parasites appeared to be more host-specific than Plasmodium, which occurred at every sampling location and in every host species examined. There were no significant differences in overall parasite prevalence attributable to either site or species, although Plasmodium and Haemoproteus occurrences differed by site-species combination and the borderline significance of our test for between-site variation (P < 0·06) implied that with a larger sample size, differences in parasite prevalence among locations might be detectable.

The incidence of fever among infants in the village of Idete in the Morogoro region of Tanzania was analysed in relation to densities of Plasmodium falciparum parasites in the peripheral blood. Parasite densities in both fever cases and in asymptomatic infants, were compared and a Bayesian non-parametric mixture decomposition algorithm was used to estimate the proportion of fevers attributable to malaria and hence the incidence of clinical malaria. Age group-specific densities of peripheral parasitaemia showed little seasonality, but the clinical malaria incidence showed a clear peak in the wet season in children aged less than 9 months. Estimates of the parasitaemia-specific incidence of clinical malaria were used to quantify apparent tolerance of parasites, and indicated that clinical episodes occurred on average at lower parasite densities during the wet season than in the dry season. These patterns could reflect differences in levels of anti-toxic immunity, but the nature of the seasonal differences supports the alternative explanation that the variation in apparent tolerance may be an effect of changes in the ratio of peripheral parasite densities to the sequestered mass.