Ex vivo culture of spleen cells from BALB/c mice infected with 2 × 106Leishmania major (L.major) promastigotes were cultured with ConcanavalinA (ConA) or leishmanial antigen (L. Ag) and tested for prostaglandin E2 (PGE2) and for leukotriene B4 (LTB4), in order to study their involvement in the evolution of cutaneous leishmaniasis and the connexion with lymphokine-mediated responses. The data were compared with those obtained in BALB/c mice protected against L. major by sublethal irradiation (550 rad; cured mice). In the unprotected BALB/c mice the levels of PGE2 that were responsible for the depression of interferon-γ (IFN-γ) and tumour necrosis factor-α (TNFα) Th1-associated cytokines and for the relative increase in the interleukin-4 (IL-4) became higher and higher as the lesion progressed. On the contrary, the cured mice produced levels of PGE2 similar to normal uninfected controls, high levels of TNFα and IFN-γ and low levels of IL-4. Elevated levels of LTB4 were detected in the early stage of infection in the unprotected mice compared to cured ones, a sign of more intense inflammation and a stimulus for the recruitment of inflammatory cells. The observation that exogenous LTB4 was able to enhance in vitro both Th1 cytokines in cured mice and Th2 cytokines in unprotected ones suggests that LTB4 could act in the recruitment of the T cells already committed to Th1 or Th2 phenotype.

L-amino acid esters such as leucine methyl ester (Leu-OMe) destroy Leishmania mexicana amazonensis amastigotes by a mechanism which may involve hydrolysis of the compounds by parasite enzymes. Moreover, several esters (e.g. Ile-OMe) prevent the killing of parasites by Leu-OMe, perhaps by inhibition of the hydrolytic enzymes. We show here that certain amino acid amides are also leishmanicidal. Killing of Leishmania within macrophages was assessed microscopically, and that of isolated amastigotes was measured by reduction of the tetrazolium MTT. Amino acid amides were generally less active than the methyl esters and several were more toxic to the macrophages, as determined by inspection of Giemsa-stained preparations. Ranks of activity of the amides on isolated amastigotes were Trp > Leu > Phe > Met > Tyr. The amides of Ala, Gly, Val, Ile, His and D-Leu were inactive. This pattern of activity is similar to that of amino acid methyl esters. Ile-NH2 and a few other amides protected intracellular as well as isolated parasites from killing by Leu-OMe. Conversely, Ile-OMe reduced the toxicity of Leu-NH2 for isolated amastigotes. None of the esters or amides assayed prevented the destruction of Leishmania by Trp-NH2. The results are compatible with the view that amino acid esters and amides may be recognized by the same or similar parasite enzymes.

The nematode, Heterotylenehus autumnalis, generally failed to develop successfully in Musca domestica L., Orthellia caesarion (Meigen) and Ravinia l'herminieri(Robineau-Desvoidy). Failure is attributed mainly to host resistance in the form of haemocytic encapsulation of the small gamogenetic female nematode. In a few instances, the nematode was able to complete development successfully in housefly and Orthellia, but was not capable of leaving the host. These few instances of development in the unnatural, experimental hosts are attributed in part to general ’weakening’ of the host by superparasitism. In many cases superparasitism resulted in the death of the fly larvae or pupae.

Tracheolar proliferation was usually associated with the encapsulated nematodes and there was evidence that many of them were expelled from the host during pupation. We also observed nematodes with cephalic caps of dark material, presumably melanin, and some that were tightly girdled with this material. A host reaction, apparently never before reported for a parasitized insect, was the darkening (presumably melanization) of the larval anal organ.

The authors would like to express their appreciation to Dr A. J. Nappi, Biology Department, State University of New York, Oswego, New York, and Dr G. 0. Poinar, Jr., Department of Entomology and Parasitology, University of California, Berkeley, California, for reading an early draft of the manuscript and offering critical comments. The senior author would like to express his deep appreciation to Dr W. R. Nickle, Nematology Investigations, Crops Research Division, Agr. Res. Serv., USDA, Beltsville, Maryland, and to Dr H. Welch, Zoology Department, University of Manitoba, Winnipeg, Canada, for their help and encouragement during the course of this study. This study was supported in part by a grant from the University of Connecticut Research Foundation.

Within southern Africa, the widely distributed four-striped mouse genus (Rhabdomys) is parasitized by, amongst others, the specific ectoparasitic sucking louse, Polyplax arvicanthis. Given the presence of significant geographically structured genetic divergence in Rhabdomys, and the propensity of parasites to harbour cryptic diversity, the molecular systematics of P. arvicanthis was investigated. Representatives of P. arvicanthis were sampled from Rhabdomys at 16 localities throughout southern Africa. Parsimony and Bayesian gene trees were constructed for the mitochondrial COI, 12S rRNA, 16S rRNA and nuclear CAD genes. Our findings support the existence of 2 genetic groups within P. arvicanthis separated by at least 25% COI sequence divergence, which is comparable to that observed among recognized Polyplax species. We therefore propose that these 2 genetic lineages probably represent distinct species and that the apparent absence of clear morphological differences may point to cryptic speciation. The 2 taxa have sympatric distributions throughout most of the sampled host range and also occasionally occur sympatrically on the same host individual. The co-occurrence of these genetically distinct lineages probably resulted from parasite duplication via host-associated allopatric divergence and subsequent reciprocal range expansions of the 2 parasite taxa throughout southern Africa.

In a paper published with Warburton in 1909 (Parasitology, ii. 70–76, Figs. 17–26), I described and figured a number of abnormalities observed in ticks of which the most remarkable were two specimens, Boophilus decoloratus ♂ and Rhipicephalus sanguineus ♂ (Figs. 22, 25 and 26), showing two ani together with a duplication of the adanal shields; in the Rhipicephalus duplication was more pronounced in that a subcircular spiracle was present posteriorly in the median line; the Boophilus exhibited two caudal spines. The other specimens figured were Hyalomma aegyptium ♂ and Boophilus australis ♂ (Figs. 18 and 21) which showed underdeveloped adanal plates on the right side. All of these specimens were found attached to a host.

Lambs given 60000 third-stage larvae of Nematodirus battus were killed on days 16, 20, 22, 24 and 32 of the infection and the duodenal mucosa was examined by scanning electron microscopy (SEM). On day 16 of the infection the villi were long and finger-like and, although goblet cells were visible, the surface of the villi was not extensively folded, as is the surface of villi of uninfected control animals. By day 20 of the infection the villi had been reduced to flattened, plate-like structures or had formed low, irregular-shaped ridges. On this day of the infection the nematodes appeared to be enclosed by mucus-like material. As the infection progressed the intestinal damage was repaired, so that, by day 24 of the infection, the surface of the intestine was covered by short, smooth, finger-like projections and, by day 32 of the infection, the morphology of the intestine was somewhat similar to that of the control lamb. The possible role of villus atrophy and of mucus in the rejection of N. battus from the intestine is discussed.

Prepupae and pupae are shown to lose weight more rapidly at low than at high humidities. This more rapid loss of weight is due to loss of water alone and not to loss of dry matter.

The limits of temperature and humidity which each of the two stages can survive have been mapped out. If the metamorphic period as a whole is considered, it is likely that the limits of temperature and humidity for survival and development will be narrower than for each stage considered alone.

Babesia rodhaini remains in the blood of most rats from 2 to 12 months after the acute primary parasitaemia has subsided. By analogy with some trypanosome and malaria infections it is suggested that piroplasms may have the capacity for antigenic variation, thus allowing the parasite to survive in the host for so long albeit as a chronic infection. A population of B. rodhaini was isolated which was considerably less sensitive in passive transfer experiments to two pools of serum from recovered rats than the normal passage population.

I thank Dr S. F. Barnett for his advice during the work and Dr F. Hawking and my colleagues at Mill Hill for criticizing the manuscript. This work was carried out during the tenure of an Agricultural Research Council Studentship.

Host snail demography and trematode parasitism were followed for one host generation in a shallow brackish lagoon of the western Baltic Sea. In addition, a laboratory experiment was simultaneously conducted to quantify the effects of parasitic infection on host fecundity. Hydrobia ventrosa of the cohort of 1996 had a maximum life-span of up to 2 years and reproduced between May and November of their second calendar year in 1997. Snails died after reproduction. The first trematode infections appeared in May 1997 when the snails started to mature. Total trematode prevalence peaked in summer and declined during winter to the lowest level in early spring 1998. Eight taxa of larval trematodes were found. Egg production of females with trematode infections was significantly reduced. Among females with pre-patent infections, about 20% were still able to produce eggs. Among females with patent infections merely 9% could lay eggs, compared to an average of about 51% in uninfected females. Taking into account a summer prevalence of about 25%, parasitic infections caused an overall reduction in egg production of the snail host population of about 15%. The reduction in host fecundity as a result of larval trematode infection did not measurably affect the population dynamics of H. ventrosa, because other environmental factors, especially winter severity and available food supply, were concluded to be much more relevant.

In this paper we address the question of detecting immunity to helminth infections from patterns of infection in endemic communities. We use stochastic simulations to investigate whether it would be possible to detect patterns predicted by theoretical models, using typical field data. Thus, our technique is to simulate a theoretical model, to generate the data that would be obtained in field surveys and then to analyse these data using methods usually employed for field data. The general behaviour of the model, and in particular the levels of variability of egg counts predicted, show that the model is capturing most of the variability present in field data. However, analysis of the data in detail suggests that detection of immunity patterns in real data may be very difficult even if the underlying patterns are present. Analysis of a real data set does show patterns consistent with acquired immunity and the implications of this are discussed.

1. The life history of Merocystis kathae shows that development follows a seasonal course. The youngest stages may appear in the kidney any time between March and June. Growth proceeds and sexual differentiation takes place but mature gametes are not found until November, when the first stages of sporogony also make their appearance. Mature spores containing sporozoites are formed in January and become increasingly common up to May. Degenerating stages of spores are common in summer.

2. The smallest parasites within the cells of the kidney are about 10μ. Growth occurs in the intracellular condition. The karyosome is complex, and contains a chromatinic body; in older parasites no chromatin reaction is given by the nucleus outside the karyosome.

3. Sexual differentiation is not perceptible until growth is almost complete.

4. In the female the intrakaryosomic body emerges, though a large karyosomic remnant remains until after fertilisation. Very fine granules of chromatin reappear in the nucleus, and form a fine network, which incorporates the intrakaryosomic body, and later forms the characteristic prefertilisation ‘cobweb’ nucleus. This network contracts in the mature macrogamete. Meantime the parasite has become free of its host cell, and the cytoplasm stains more intensely.

5. In the male, the elongated karyosome breaks down, generally completely, leaving the centrally placed chromatin body surrounded by a ring (in sectional view), of deeply stained material containing granules of chromatin, into which the central body passes as in the female. The male is released from the host cell, and, as in the female an alteration of the cytoplasmic staining occurs.

6. The nucleus, in the male parasite, moves to the surface, and undergoes repeated divisions until approximately 32 nuclei are formed. Cleavage of the cytoplasm brings about the formation of uninucleate cytomeres; within each of these are produced many nuclei, which lie near the surface, and finally become the microgametes.

7. After the macrogamete is fertilised, a thick membrane is formed outside the zygote. The nucleus assumes the characteristic spindle shape and subsequently divides.

8. Nuclear divisions proceed, until finally a great number of cone-shaped nuclei are found on the surface. This becomes folded and the nuclei sink in, and each is surrounded by a portion of cytoplasm to form a sporoblast. A single nuclear division then occurs, and the two nuclei elongate to form sporozoites each with a small cytoplasmic body.

9. Nuclear divisions are mitotic, but the longitudinal splitting of the chromosomes occurs without contraction. It is probable that ‘amitotic’ appearances are due to the incomplete incorporation of these long chromosomes at the telophase poles, and the multipolar divisions to the subsequent division of such ‘amitotic’ resting nuclei. Six chromosomes can be seen at the anaphase poles, but each is looped back so that it is V or J shaped. This chromosome number is characteristic of the divisions of both microgametogenesis and sporogony.

10. There is good evidence that, as in other Coccidia, reduction division occurs in the zygote, and that this is therefore the only diploid phase.

Plasmodium berghei XAT, an attenuated variant of lethal P. berghei, causes a resolving infection in Balb/c mice from which they recover in about 3 weeks. The parasitaemia displays an early peak at about 5 days, followed by a steep drop in parasite number associated with the appearance of degenerating forms inside mature erythrocytes; the parasites remaining are inside reticulocytes. By contrast, no degenerating parasites were seen in infections caused by the virulent parent, which was mainly confined to mature erythrocytes. However, P. berghei XAT was no more sensitive to reactive O2 metabolites, generated by alloxan, or to tumour necrosis serum, than its virulent parent. Furthermore, its early drop in parasitaemia was unaffected by silica. The drop still occurred in the absence of T cells, although the infection was then ultimately lethal, and it was not mediated by NK cells since it occurred in nude mice treated with anti-asialo GM1 serum to abolish NK cell activity. However, it was absent in splenectomized mice, in which P. berghei XAT infection was lethal. Thus, the attenuation of P. berghei XAT infection is not due to increased susceptibility to some of the agents thought to cause parasite destruction, but to some other mechanism in which the spleen is involved.

Circulating antigen has been detected in the serum of rabbits experimentally infected with Taenia pisiformis. A rabbit antiserum against an antigen preparation derived from the in vitro maintenance of living metacestodes of T. pisiformis was used in a double-antibody enzyme-linked immunosorbent assay (ELISA). Antigen was detected in infected rabbit serum 48 h after infection and peak levels were recorded at 2 weeks post-infection or post-challenge. The pattern of circulating immune complex formation followed closely that of circulating antigen, and infected rabbit serum contained both anti-metacestode and anti-oncospheral antibodies. Serum antigen levels were just detectable (0·4–0·8 μg protein/ml) over the period (> 2 weeks post-infection) of peritoneal cyst development. The circulating antigen probably has antigenic determinants in common with the oncosphere, juvenile and mature metacestode stages. Possible reasons for the temporal variation in serum antigen levels are discussed.

Parasites with low host specificity are predicted to search for hosts in ways less specific than highly host-specific species. They may also be better dispersers. Unionicolan mites that parasitize mussels are positively phototactic, with some species becoming negatively phototactic when host substances are present. This response has been interpreted as an aid to host location and occurs in species where adult mites have a relatively permanent association with hosts. Three species of Unionicola (Unionicolidae: Acari) that differ in host specificity co-occur in freshwater mussels (Unionidae) in St Mark's River in north Florida.

The uses of metabolic profiling technologies such as mass spectrometry and nuclear magnetic resonance spectroscopy in parasitology have been multi-faceted. Traditional uses of spectroscopic platforms focused on determining the chemical composition of drugs or natural products used for treatment of parasitic infection. A natural progression of the use of these tools led to the generation of chemical profiles of the parasite in in vitro systems, monitoring the response of the parasite to chemotherapeutics, profiling metabolic consequences in the host organism and to deriving host-parasite interactions. With the dawn of the post-genomic era the paradigm in many research areas shifted towards Systems Biology and the integration of biomolecular interactions at the level of the gene, protein and metabolite. Although these technologies have yet to deliver their full potential, metabolic profiling has a key role to play in defining diagnostic or even prognostic metabolic signatures of parasitic infection and in deciphering the molecular mechanisms underpinning the development of parasite-induced pathologies. The strengths and weaknesses of the various spectroscopic technologies and analytical strategies are summarized here with respect to achieving these goals.

In this study the anti-leishmanial activity and anti-microtubule effects of paclitaxel, trifluralin and a combination of paclitaxel and trifluralin have been tested in a wild type and sodium arsenite-resistant strain of Leishmania donovani. Both paclitaxel and trifluralin have been shown to be effective in limiting parasite growth. Specific alterations in morphology, tubulin polymerization dynamics, post-translational modifications and cellular distribution of the tubulins have been confirmed to be a part of the intracellular anti-microtubule-events that occur in arsenite-resistant L. donovani in response to these agents, ultimately leading to death of the parasite. DNA analyses of the drug-treated wild type and arsenite-resistant strains revealed an apoptosis-like death in response to paclitaxel and the combination but not to trifluralin. Data provide valuable information for further development of chemotherapeutic strategies based on anti-microtubule agents against drug resistant Leishmania parasites.

1. Cotylaspis sinensis and Lophotaspis orientalis are described as new species of trematodes from the small intestine of the turtle, Amyda tuberculata, from Foochow, Fukien Province, China.

2. Stichocotyle cristata is described as a new species from the spiral valve of the cow-nosed ray, Rhinoptera quadriloba, from Biloxi Bay, Mississippi.

3. A new subgenus, Multicalyx, is created for the species Stichocotyle cristata, while the species S. nephropis appropriately belongs to a new subgenus Stichocotyle.

4. Evidence is provided that aspidogastrid worms are referable neither to the Monogenea nor the Digenea, but belong to an intermediate subclass group, Aspidogastrea, n.n.

5. The genus Stichocotyle has been removed from the family Aspidogastridae Poche, 1907, and placed in a new family, Stichocotylidae.

The materials for this paper were obtained from three sources: (a) the examination, on successive occasions during the period December 1939–April 1940, of volunteer subjects, mainly from common lodging houses in east London, prior to their treatment with pediculicides, (b) the examination, during April 1940, of large numbers of men from common lodging houses, Salvation Army hostels, night refuges and other sources, in a search for further suitable subjects for control experiments, and (c) the study of the process of infestation of shirts issued to selected volunteers and worn continuously over a period of 10 days. The material from the first source is largely selective, since infested volunteers were specifically invited; that from the second source is more representative of the population of cheap hostels, since no emphasis was laid on the presence of lice, the men being induced to submit to examination by the offer of payment. It is, however, obviously not a random sample since it represents volunteers, and neither it nor the source (a) material should be used as a measure of the frequency or degree of infestation normal to the corresponding group of the city population.

Ten albino rats injected with hydrocortisone were infected with 36–66 cystacanths of Corynosoma semerme in order to study the course of infection in a warm-blooded animal. Surveys were carried out 2, 5, 8, 14, 18, 21 and 28 days after infection. Recovery decreased from 60% after 2–5 days to 22% after 28 days. The proportion of males dropped markedly before the 8th day of infection. The worms were concentrated in the latter half of the intestine, the males being in a more anterior location on average. The males matured between the 2nd and 5th day of infection. Disintegrated ovaries were observed in some of the 2-day-old females, but mature free ovaries were seen only in 5-day-old females. By the 14th day many females contained fully developed eggs, but it was only after the 18th day that the number of eggs increased considerably. Male worms were not encountered in the 4-week-old infection. The females were longer than the males. In the present study, experimental infections are compared with other acanthocephalan infections in both birds and mammals.

A new technique for determining the trypanocidal activity of body fluids has been devised, using very small quantities in the wells of plastic microtest plates.

The activities of blood and tissue fluid of rabbits have been measured after the injection of melarsoprol, suramin, diminazene aceturate and isometamidium chloride. Activity against Trypanosoma (Trypanozoon)brucei Persisted in body fluids for a shorter time in treated normal rabbits than in treated rabbits infected with the tryponosome. The difference was caused by the participation of the immune response of the infected animals.

The new technique was sensitive enough to detect these interactions of chemotherapy and immunology and should be of use in the study of new trypanocidal compounds.