A double clone of Trypanosoma platydactyli Catouillard, 1909, derived from a single trypomastigote from the blood of the Moorish gecko, Tarentola mauritanica, was grown in vitro. Morphogenesis of the parasites led to a stable population of promastigotes which were identical, in general morphology, ultrastructure and the electrophoretic mobility of 8 enzymes, to those cultures previously considered to be Leishmania tarentolae Wenyon, 1921. These cultures included the strain isolated from the type locality in Algeria by Parrot (1949) and later used as a laboratory model for the genus Leishmania. T. platydactyli and L. tarenlolae are synonymized and the present status of saurian Leishmania parasites is discussed.

In this study, the advantage of the use of chloroquine (CQ) containing liposomes (lipCQ) over free CQ in the chemotherapy of murine malaria (Plasmodium berghei) was demonstrated. The maximum permissible dose per intraperitoneal injection was 0·8 and 10 mg for CQ and lipCQ, respectively. An increase in therapeutic and prophylactic efficacy of lipCQ in comparison with free CQ at a 0·8 mg CQ dose level was found. It was possible to obtain 100% efficacy (injection at day 5 after infection; parasitaemia 4–8%) with one single intraperitoneal injection of 6 mg lipCQ. Moreover, the ability to increase the doses of CQ per injection after liposome encapsulation allowed successful treatment of infections with CQ-resistant Plasmodium berghei which could not be cured by a 7-day course with the maximum tolerable dose of free CQ of 0·8 mg/mouse/day.

Larvae of Hymenolepis diminuta develop in the haemocoele of the beetles Tribolium and Tenebrio, and of the locust Schistocerca gregaria, without being encapsulated by haemocytes. The mechanism of this evasion of the haemocytic defence reaction has been examined using various techniques. Larvae grown in culture and injected into S. gregaria have few or no haemocytes adherent even after 8 h, although latex beads injected at the same time have been thickly encapsulated. This, and results of transplanting cysticercoids and host tissue between different insect species, suggests that the surface of the larvae may bear an inherent similarity to the surface of host tissues and thus escape recognition as ‘not-self’ by the host’s haemocytes.

Experiments on the larval development of Fasciola gigantica carried out under natural conditions have shown that at temperatures of 16° C. or less the rediae did not produce cercariae. The first-generation rediae, developed from the sporocyst, and all the rediae of subsequent generations produced only daughter rediae and did not change over to the production of cercariae as long as the low temperatures of the cold season lasted.

As soon as the cold season ended and the temperature of the water in the aquaria containing the infected snails rose to a mean maximum of 20° C. all the rediae switched from redial to cercarial production.

Head lice prevalence varies greatly between and within countries, and more knowledge is needed to approach causes of this variation. In the present study, we investigated head lice prevalence among elementary school students and their households in relation to individual and household characteristics as well as spatial variables. The investigation included households from 5 geographically separated municipalities. Present infestations among household members as well as previous infestations in the household were reported in a questionnaire. In elementary school students prevalence was low (1·63%), but more than one-third of the households (36·43%) had previously experienced pediculosis. Prevalence was higher in elementary school students than in other household members, and highest in third-grade children. Prevalence was also influenced by the school attended, which suggested that interactions between children in the same school are important for head lice transmission. Previous occurrence of head lice in homes also increased the risk of present infestation. Prevalence of previous infestations was higher in households with more children and in more densely populated municipalities, indicating that the density of hosts or groups of hosts influences transmission rates. These results demonstrate that information of hosts’ spatial distribution as well as household and individual characteristics is needed to better understand head lice population dynamics.

The hypothesis that intestinal helminth communities in freshwater brown trout are dissimilar in composition and structure to those in the European eel was tested by an analysis of component communities from 72 localities and of infracommunities from 34 localities in the British Isles and Norway. Derived indices were then compared with published data from eels. Composition of helminth communities differed considerably between the two hosts as a group of 4 species occurred commonly in trout and so gave greater predictability to the community composition. These 4 species were trout specialists and in 97% of the localities a trout specialist dominated the community rather than a generalist acanthocephalan as is typical for eels. By contrast all measures of community structure and indices of richness and diversity indicated that helminth communities in trout were isolationist in character, species poor and exhibited low diversity at both component and infracommunity levels. All values of indices for trout helminth communities were strikingly similar to those obtained from eels. Evidence of interspecific interactions within the trout helminth communities and a limit of 4 to infracommunity species richness further enhanced the similarities and suggested a common determinant of community structure. The hypothesis was thus supported in respect of species composition but refuted in respect of community structure.

Life-cycle stages of the microsporidia Nosema bombycis, the pathogen causing silkworm pebrine, were separated and purified by an improved method of Percoll-gradient centrifugation. Soluble protein fractions of late sporoblasts (spore precursor cells) and mature spores were analysed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Protein spots were recovered from gels and analysed by mass spectrometry. The most abundant differential protein spot was identified by database search to be a hypothetical spore wall protein. Using immunoelectron microscopy, we demonstrated that HSWP5 is localized to the exospore of mature spores and renamed it as spore wall protein 5 (NbSWP5). Further spore phagocytosis assays indicated that NbSWP5 can protect spores from phagocytic uptake by cultured insect cells. This spore wall protein may function both for structural integrity and in modulating host cell invasion.

Ascariasis is an important infection in humans (Ascaris lumbricoides) and pigs (Ascaris suum) and individuals appear to be predisposed to either heavy or light worm burdens. These extremes of susceptibility and resistance are represented in a mouse model by 2 strains of mice, CBA mice showing high resistance to infection and C57BL/6 which are highly susceptible, as reflected in worm burdens in the lungs 6–7 days after infection. In an attempt to identify the point at which the difference between these 2 strains is first manifested, we quantified worm burdens at key stages during infection leading up to the pulmonary stage of development. Thus mice were inoculated with fully embryonated A. suum eggs and larval burdens were enumerated in the large intestine and rectum, liver and lungs of the 2 strains at 6 h post-inoculation (p.i.) and on each of days 1–8 p.i. inclusively. A higher percentage of the total inoculum was recovered from the intestine/rectum of C57BL/6j mice in contrast to CBA/Ca mice at 6 h p.i. Larvae were recovered from the intestinal contents and also whilst actively migrating through the large intestinal wall. The number of larvae recovered was significantly reduced in CBA/Ca mice in contrast to C57BL/6j mice between the phase of migration from the liver and arrival in the lungs. The combined results of the inoculation of mice with corticosteroids and the examination of the change in profile and number of leukocytes present in bronchoalveolar lavage fluid suggested that the pulmonary inflammatory immune response was not prominently involved in primary protection of mice to A. suum infection in the latter days of infection in the lungs. The susceptible C57BL/6j mice produced a BAL response almost twice as intense as that of resistant CBA/Ca mice with stronger neutrophil, lymphocyte and eosinophil but not macrophage components, suggesting that the difference in worm burdens between the strains was generated earlier in the course of infection. These results were further corroborated by a histological examination of the lung tissues which showed that the passage of the larval stages of A. suum through the mouse lungs was associated with a marked inflammatory response in both strains. Again, C57BL/6j mice exhibited increased inflammation relative to CBA/Ca mice. Hence some hepatic/post-hepatic factor that varies between the 2 strains, but exerts its effect before the lung phase plays a critical role in determining the success of larvae through the host tissues. The possible sites of this host defence are reviewed.

Babesia parasites generally require a defined percentage of serum in the culture medium for their in vitro growth. In this study, we attempted to culture Babesia bovis in a serum-free condition. The growth pattern and morphology of B. bovis in serum-free (plain) GIT medium were unaltered as compared to those of the standard growth condition containing 40% bovine serum in M199. When exposed to the test drugs, the parasite in plain GIT medium showed clearly lower IC50 values than those in 40% serum-containing GIT medium, indicating that several serum components may interfere with the drug bio-availability. Therefore, the serum-free culture system is useful for standardizing drug test protocols and understanding the roles of serum factors in the drug test.

Parasites have been found to be more infective to sympatric hosts (local adaptation) in some systems but not in others. The variable nature of results might arise due to differences in host and/or parasite migration rates, parasite virulence, specificity of infection, and to differences in the dose–response functions. We tested this latter possibility by manipulating the dose of trematode (Microphallus sp.) eggs on sympatric and allopatric host populations (Potamopyrgus antipodarum). We found that infection rapidly increased to a high asymptote (0·88±0·02, 1 S.E.) in the sympatric host population, but infections were low and surprisingly unrelated to dose in the allopatric host. We also found that host survival and growth rate were not negatively affected by increasing parasite dose in either population. These results suggest that defences in the allopatric host were not overwhelmed at high parasite doses, and that any life-history costs of defence are not plastic responses to parasite dose.

The complete sequence of the 18S small subunit (SSU) ribosomal DNA of Hammondia hammondi and Sarcocystis mucosa was obtained and compared to SSU rDNA sequences of Neospora caninum, Toxoplasma gondii, Besnoitia besnoiti, 2 species of Frenkelia, 3 species of Isospora, and 13 species of Sarcocystis. Analyses showed that H. hammondi and T. gondii are monophyletic and that these taxa shared a common ancestor with N. caninum and B. besnoiti. The weight of evidence shows that S. mucosa, S. neurona, and Frenkelia species form a clade thereby supporting the conclusion that Sarcocystis is paraphyletic.

The hatching of Hymenolepis diminuta eggs and penetration of the emergent hexacanths in adult and larval Tenebrio molitor beetles had been described. Hatching was shown to be a two-stage process involving rupture of the eggshell by the insect's mandibles and digestion of the remaining egg-layers in the midgut lumen. Penetration of hatched embryos was examined by histological methods that demonstrated the rate of migration and the route taken by hexacanths entering the haemocoel of adult beetles. Differences in the arrangement of the midgut tissues in adult and larval T. molitor were detected and shown to account for the failure of hexacanths to complete migration in the larvae. The role of the embryonic hooks and penetration gland secretions during hatching and penetration has also been discussed.

I should like to thank Professor T. R. E. Southwood for providing generous research facilities, Dr June Mahon for her advice and encouragement, and in particular, Dr W. Mordue for his continuous interest and many useful criticisms. This work was conducted during the tenure of a Science Research Council Studentship at Imperial College of Science and Technology, London, S.W. 7.

The structure of the head and especially of the mouth-parts of these economically very important flies has been studied by many observers. The first very brief remarks on the proboscis were made by Wiedemann (1830), in his original description of the genus Glossina. He pointed out that the proboscis is almost as long as the thorax, and setiform and triangular in its basal part, the palps almost as long as the proboscis and horizontal. In the same year, Robineau-Desvoidy (1830) described another species of tsetse-fly, Glossina palpalis, but under the generic name Nemorphina, which became a synonym of Glossina. In his diagnosis of the genus, he gave an even shorter description of the proboscis which he believed was not adapted for sucking blood.

The in vivo effects of a single, subcurative dose (200 mg/kg body wt of mouse) of praziquantel on the structure of the tegument and subtegumental tissues of juvenile (21-, 26- and 30-day-old) and adult Schistosoma mansoni are described. In juvenile worms praziquantel caused only moderate damage to both the tegument and subtegumental tissues although the degree of drug-induced damage was related to both the sex of the worms and to the developmental status of each individual worm. In general, male worms exhibited more extensive and longer lasting surface damage than females. However, the level and extent of the changes increased as the worms became more developmentally advanced with adult worms showing extensive damage to the tegument and vacuolization and disruption of the subtegumental tissues. The possible correlation between the stage-dependent changes in susceptibility to praziquantel and age-related changes, particularly in the phospholipid composition of the outer tegumental membrane is discussed.

Three species of filarial worms, Wuchereria bancrofti, Brugia malayi and Brugia timori, are the causative agents of lymphatic filariasis in man, defined by the characteristic tropism of adult worms of each species for the afferent lymphatics. Reproductive activity leads to the release of large numbers of microfilariae, which circulate in the vascular system, and upon ingestion by an appropriate mosquito vector, develop through to infective third-stage larvae (L3) within 10–14 days. After a subsequent bloodmeal, the infective larvae enter the definitive host via the wound and mature to the adult stage over several months, involving two moults, during which the entire nematode exoskeleton (cuticle) is replaced.

Rhipicephalus appendiculatus ticks, infected with Theileria parva, were fed on rabbits and removed at daily intervals for 9 days. Half of the ticks removed were dissected and their salivary glands processed and examined for parasites. The remaining ticks which had been removed were ground up and aliquots of the supernatant fluid thus obtained were injected into East Coast fever susceptible cattle. Cattle injected with supernatant fluids from ticks fed for 4–9 days became infected, and this could be correlated with the histological detection of mature parasites in the corresponding ticks. The most highly infective supernatant fluids were prepared from 5-day-fed ticks. In a second experiment it was shown that female ticks of a variety of weights contained infective particles of T. parva.

Sex ratios of adult schistosomes in mice are almost invariably different from 1·0 and are biased towards males. The bias applies to wild rats infected with Schistosoma japonicum and trapped in an endemic area of the Philippines (male: female ratio = 1·7). It also applies to cercariae of snails collected in such areas and assessed by infection of laboratory mice using cercariae from individual snails (male: female ratio may approach 6·0). Experiments were designed to determine if duration of infection in the mammalian host was a factor that influenced the sex ratio of miracidia used for infecting snails and subsequently mice. BALB/c and C57BL/6 mice were infected with 100 cercariae of S. mansoni, and liver eggs harvested at early and late time points for infection of snails and production of cercariae. Two phenomena were demonstrated: firstly, a more pronounced male bias when eggs were harvested late compared with early in infection; secondly, a reduced apparent hatchability of eggs in BALB/c compared with C57BL/6 livers. The possibility is raised by the data that female miracidia within eggs of chronically infected individuals may be more prone to immune damage than male miracidia with important epidemiological consequences.

The primary infection of breeding female rates with N. brasiliensis was examined as an experimental model for the study of the effect of lactation on host-parasite relationships.

Self-cure was inhibited when the period of infection corresponded with lactation, and a majority of worms could persist to day 34 when lactation was prolonged. A normal self-cure occurred during pregnancy, when litters were removed at birth or when the suckling litter was reduced to 3 young.

1. The main facts in Brasil's (1907) account of the intracellular schizogony in Selenidium caulleryi from Protula tubularia have been confirmed. Early stages in the sporogony of this species are described now for the first time.

2. Intracellular schizogony is described for the first time in Selenidium mesnili Brasil from Myxicola infundibulum, and here also the early stages in sporogony are noted for the first time.

3. The life histories of Caullery and Mesnil's two unnamed species of Selenidium (now called S. spionis (Köll.) and S. foliatum n.sp.) from Scolelepis fuliginosa have been exhaustively studied. No schizogonic phase has been observed in either. The gametocysts, here described for the first time, are found to develop fully only after escape into the sea. The gametocysts of S. spionis are ovoid, 108μ x 60μ and contain spores with four sporozoites: those of S. foliatum are spherical, 70μ in diameter, and their spores contain eight sporozoites.

4. New or hitherto little known species of Selenidium are recorded from Cirratulus cirratus Müll., Branchiomma vesiculosum Mont., Sabella pavonina Sav., Pomatoceros triqueter L. and Terebella lepidoria Kühl, and the morphological characters of the trophozoites are described.

5. A discussion follows of the value of the diagnostic characters of the genus Selenidium. It is suggested that this genus requires drastic revision and will probably have to be dismembered. Stress is laid, however, on the occurrence in all the gregarines examined, and at all the observed stages of their development, of characteristic chromatic bodies at the anterior end, structures which have hitherto escaped the notice of most observers.

Seven cDN A clones of Schistosoma mansoni containing the C-terminal part of the deduced sequence of a mucin-like protein have been identified. The protein contains 28% threonines, 20% serines, and has a pi of 3middot;4. On Northern blots of RNA of adult worms, the cDNA clones detect 2 transcripts of 1middot;65 and 4middot;2 kb which are expressed only in female worms. The tissue of gene expression, as revealed by in situ hybridization, is the epithelium surrounding the female reproduction duct proximal to its entrance into the ootype. Accumulation of N-glycosylation sites suggests that the protein, like other mucins, might form a protective layer, coating the lining of the duct. Regarding its acidic pi, we hypothesize a role in preventing premature egg-shell formation. This is the first female-specifically transcribed sequence, hitherto known in S. mansonithat is not expressed in the vitellaria.