The circumstances which permit the establishment of Leishmania infections in sandflies were investigated by altering the growth conditions for L. donovani parasites in the unsuitable vector Phlebotomus papatasi. Only 5·0% of the sandflies harboured a few parasites 3 days after feeding on promastigotes in defibrinated blood. Heparinized blood or the addition of trypsin inhibitor to the meals allowed persistence of infections (day 6) in 9·9% and 25·8% of the flies respectively. Meals of erythrocytes, saline and amastigotes produced 44·4% fly infection on day 6, while similar promastigote-initiated infections remained in 70·3% of the flies. Proteolytic activities in the guts of sandflies fed on the above meals without parasites, were the highest after defibrinated bloodmeals. Erythrocytes with saline decreased the maximal alkaline protease level from 20·8 U to 13·5 U/fly; that of trypsin from 3·9 U to 1·8 U/fly and that of the aminopeptidase from 5·5 U to 3·9 U/fly. After meals of heparinized blood, the maximal alkaline protease activity (12·0 U/fly) was also much lower than after defibrinated blood-feeding. The different diets which resulted in comparatively low enzymatic activities, including blood with trypsin inhibitor, also promoted the survival of infections. This implies that the proteolytic activity in the sandfly gut modulates the vector susceptibility.

Malaria parasites of the genus Plasmodium make a hazardous journey through their mosquito vectors. The majority die in the process, many as a result of the action of mosquito defence mechanisms. The mosquito too is not unscathed by the encounter with these parasites. Tissue damage occurs as a result of mid-gut invasion and reproductive fitness is lost when many developing ovarian follicles are resorbed. Here we discuss some of the mechanisms that are involved in killing the parasite and in the self-defence mechanisms employed by the mosquito to repair the mid-gut epithelium and to manipulate resources altering the trade-off position that balances reproduction and survival. In all cases, cells die by apoptotic-like mechanisms. In the midgut cells, apoptosis-induction pathways are being elucidated, the molecules involved in apoptosis are being recognised and Drosophila homologues sought. The death of ookinetes in the mosquito mid-gut lumen is associated with caspase-like activity and, although homologues of mammalian caspases are not present in the malaria genome, other cysteine proteases that are potential candidates have been discussed. In the ovary, apoptosis of patches of follicular epithelial cells is followed by resorption of the developing follicle and a subsequent loss of egg production in that follicle.

When eggs of Ascaris suum were transferred from glass-distilled water into 0·1–0·4 m NaCl solutions, the water content of the unhatched juveniles fell with increasing concentration of solute. The effect was reversible. The egg-shell was thus permeable to water. The osmotic pressure of the egg fluid was osmotically equivalent to between 0·1 and 0·2 m trehalose. In hatching experiments in Fairbairn's medium containing 0·1 or 0·2 m trehalose, only 5 and 3% respectively of the eggs hatched; 83% of the eggs hatched in the absence of trehalose. The evidence suggests that loss of solutes from the egg fluid permits an increase in the water content of the unhatched juveniles and that this may be responsible for ending their quiescence.

Two studies were carried out to determine the effect of the rodent malaria Plasmodium yoelii nigeriensis on the blood feeding success of Anopheles stephensi. Initially, pairs of mice with similar packed cell volume (PCV) (measured by haematocrit) were selected. Following infection of one of the pair its PCV gradually fell. At various times post-infection, a comparison was made of the bloodmeal size (haemoglobin content) of mosquitoes feeding on these mice. The bloodmeal sizes increased with parasite-induced fall in PCV down to a haematocrit of 43–44%, which occurred approximately 48 h post-infection. Bloodmeals were significantly reduced, however, when mosquitoes fed on mice with higher parasitaemias and a haematocrit of 15–35%. Thus, at early stages of infection, mosquitoes ingested a bloodmeal significantly greater than did the mosquitoes feeding on the control mice. However, mosquitoes were not able to compensate for severe infection-associated anaemia. To compensate for variation due to innate differences in the mice, a second experiment was performed. Mosquitoes were fed on the same mice before (control) and after infection. Again, the bloodmeal size increased with decreasing PCV down to haematocrits of 42–45%, but declined thereafter. In this host–parasite–vector system, haematocrits that maximized erythrocyte intake were produced when gametocytes, capable of exflagellation, were present.

The recorded parasites and predators of Meligethes aeneus (F.) and M. viridescens (F.) [Coleoptera: Nitidulidae] are given together with descriptions and illustrations, for the first time, of the post-embryonic stages of the hymenopterous parasites Diospilus capito (Nees) [Braconidae], Isurgus heterocerus (Thoms.) [Ichneumonidae], Isurgus sp. A, and Cryptoserphus parvulus (Nees) [Proctotrupidae]. The egg and first instar of Thersilochus sp. are described and figured, and a species of Zeteticontus mentioned. The antennae, propodea, and ovipositors of the two species of Isurgus are compared and the ovipositors of Diospilus capito, Isurgus sp. A, I. heterocerus and Thersilochus sp. are illustrated.

A protozoan (Gregarine), a larval mite and a nematode, none of which has been identified, are recorded inhabiting Meligethes adults.

In 1851, Bilharz (1852) first discovered paired adult trematode worms originally named after him in the portal system of an Egyptian fellah. Subsequently, investigations of the deposits of ova in excreta were made, but numerous attempts by Cobbold, Sonsino, Lortet and Vialleton (1894) and others, to unravel the life history of the parasite, failed. Looss (1896), appreciating that the digenetic trematodes must necessarily pass through a molluscan intermediary, dissected many species of snails collected from the fresh-water canals around Cairo. He failed to find the cercariae of bilharzia, and discarded the hypothesis of an intermediate molluscan host. As, however, the miracidium of Schistosomum haematobium contained germinal cells within its body cavity, it must, naturally, he argued, have been destined to produce sporocysts at some stage of its life cycle. In view of this, Looss evolved the hypothesis that man acted simultaneously as the intermediary, as well as the definitive host of this parasite.

To date, little is known about the dynamics of vertical transmission of Toxoplasma gondii in Australian marsupials. Studies in mice demonstrate that vertical transmission of T. gondii is common and that chronically infected mice can transmit T. gondii to successive generations. In this study, PCR and immunohistochemistry were used to detect T. gondii in chronically infected marsupial dams and their offspring. T. gondii was detected in the unfurred pouch young of 2 out of 10 chronically infected western grey kangaroos (Macropus fuliginosus) and in the unfurred pouch young of a brush-tailed bettong (Bettongia penicillata). Results of the study suggest that vertical transmission of T. gondii can occur in chronically infected Australian marsupials.

Neuropeptide F (NPF) is an abundantly expressed neuropeptide in platyhelminth nervous systems, and exhibits a moderate, myogenic effect on muscle preparations of parasitic flatworms. NPF displays structural similarities to peptides from molluscs and vertebrate members of the neuropeptide Y (NPY)-superfamily of peptides. NPY is one of the most abundant and highly conserved neuropeptides within vertebrates and similarities between the gene organization of NPY, pancreatic polypeptide (PP) and peptide tyrosine tyrosine (PYY), suggest a common evolutionary origin of this peptide family. Dual localization analyses coupled with confocal scanning laser microscopy revealed a close spatial relationship between NPF-containing nerves and muscle fibres in M. expansa. Molecular cloning techniques identified the M. expansa NPF (mxNPF) precursor and characterized the isolated transcript which encodes an open reading frame of 57 amino acids. The transcript possesses a 17 amino acid signal peptide and the mature NPF sequence (39 amino acids) followed by a carboxyterminal glycyl extension. Sequence analysis of genomic DNA identified a product which possessed a 54 base pair intron with consensus sequences for 5′ and 3′ splice sites. The M. expansa npf gene possesses a phase 2 intron within the penultimate arginyl residue, a characteristic feature of NPY superfamily peptide-genes. The intron–exon organization of the npf gene, coupled with the abundant expression of NPF within the nervous systems of flatworms, suggests an early evolutionary origin for this peptide transmitter family within the nervous systems of basal bilaterian metazoans.

The life-cycle of Isospora ohioensis in dogs is described. Eight dogs were killed 6, 16, 24, 48, 72, 96, 114 and 120 h after feeding 106I. ohioensis sporocysts to each. First divisional stages occurred in the jejunum at 48 h post-inoculation (p.i.). At 48 h, zoites occurred in pairs in parasitophorous vacuoles of surface epithelial cells of the jejunum. The parasitophorous vacuoles were 7–9 × 6 μm and the zoites were 7–9 × 2·5 μm in sections. At 72 h, uninucleated zoites, multinucleated zoites and meronts containing fully formed merozoites occurred in surface epithelial cells of the jejunum. At 96, 114 and 120 h asexual multiplication occurred throughout the small and large intestine, mostly in the ileum. The number of asexual generations was not determined. At least 2 structurally distinct meronts were identified at 96–120 h p.i. Type I meronts contained larger merozoites (11 × 3 μm) than those (7·5 × 1·5 μm) in Type II meronts. Meronts were merozoite-shaped and contained up to 8 nuclei. Uninucleated, binucleated and multinucleated zoites occurred within the same parasitophorous vacuole. Gamonts occurred in surface epithelial cells of the small intestine, caecum and colon, but predominantly in the ileum, 96–120 h p.i. Macrogamonts were 13–17 × 11–12 (14·5 × 12·8) μm in sections and 21–26 × 17–25 (21·7 × 17·6) μm in smears. Microgamonts were 13–17 × 8–15 (15·3 × 11·4) μm in sections and 24–30 × 15–24 (27 × 19) μm in smears and contained up to 50 microgametes. The cycle was also studied in 6 dogs killed 6, 12, 24, 48, 96 and 120 h after feeding tissues of laboratory mice that had been infected with I. ohioensis oocysts 17 days earlier. Stages were not seen in the dogs killed at 6 and 12 h p.i. Asexual and sexual stages were structurally similar in size and location to the oocyst-induced cycle but their development was faster by 24 h in the mouse-induced cycle. Extra-intestinal stages were not found in sections of mesenteric lymph nodes, spleen, lung, liver, heart, skeletal muscle and brain. However, biological evidence indicated that I. ohioensis invaded the spleens and mesenteric lymph nodes of dogs fed oocysts.

Helminth infections were studied in bank voles (Myodes glareolus) from 3 woodland sites in N.E. Poland in the late summers of 1999 and 2002, to assess the temporal stability of derived statistics describing the regional helminth fauna and component community structure, and spatial influence on the latter. Regional helminth fauna changed dramatically between the two years, primarily due to a fall in the abundance of Syphacia petrusewiczi but was partially compensated for by an increase in Mesocestoides lineatus and Cladotaenia globifera. It was dominated by nematodes overall, but more so in 1999 than in 2002 when larval cestodes were more frequent. Most derived parameters for component community structure varied considerably between sites and the two surveys, the hierarchical order for sites not being maintained between surveys. They were susceptible to the disproportionate influence of three relatively rare, unpredictable species with the greatest overall aggregated distribution among hosts. Jaccard's similarity index was less influenced by the rare species, showing greater stability between sites and across years. In conclusion, temporal variation confounded any site-specific characteristics of the summary measures quantified in this study and their usefulness is therefore restricted to the years in which the surveys were conducted.

Rabbits and mice, but not sheep, guinea-pigs or rats, were suitable hosts for secondary echinococcosis using protoscoleces obtained from Australian sheep. The host specificity is tentatively related to the phylogenetic relationship between the donor host and receptor host.

The development rate of hydatid cysts in mice is described in terms of increase in fresh weight, dry weight, and maximum cyst diameter. Fertile cysts were found after 8 months when the water content of the cysts had increased to more than 95 %. The diameter of fertile cysts up to 14 months ranged from 6 to 30 mm. By 14 months, the average fresh weight of cysts was greater than the body weight of the mice.

This work was carried out during the tenure of an Australian Wool Board Senior Postgraduate Scholarship, and forms part of a thesis to be presented for the degree of Doctor of Philosophy of the Australian National University.

I wish to thank my supervisor, Professor J. D. Smyth, for guidance and criticism.

A technique is described for the efficient feeding of Rhipicephalus appendiculatus nymphae on cattle blood through an artificial membrane bearing tactile and olfactory stimuli. The effect of four anticoagulation methods on the feeding of nymphae was compared and heparinized blood was found to be the most efficacious, followed by defibrinated blood. Blood treated with acid citrate dextrose (ACD) or ethylenediamine tetraacetate (EDTA) inhibited nymphal feeding. Nymphae fed on heparinized and defibrinated blood obtained engorgement weights within the range of ticks fed on mammalian hosts and they subsequently moulted and fed normally as adults and produced viable eggs. Nymphae fed on membranes using either defibrinated or heparinized blood infected with Theileria parva piroplasms developed salivary gland infections as adult ticks and transmitted East Coast fever (ECF) to susceptible cattle. There were indications that T. parva-infected defibrinated blood was not as infective to the feeding nymphae as the infected heparinized blood. When T. parva-infected heparinized blood was used to feed nymphae through membranes in two experiments, it was found that the infections in the resultant adult ticks could be comparable to those of nymphae fed on donor cattle, but were usually lower. The membrane feeding technique will enable the study of factors affecting the tick and T. parva transmission without the complication of host/T. parva interactions and could be useful for both tick maintenance and Theileria parasite isolation and maintenance.

In the present study, we constructed gender-enriched cDNA libraries for the adult stage of the parasitic nematode Oesophagostomum dentatum (order Strongylida) using suppressive-subtractive hybridization (SSH), sequenced clones from the female-library and male-library (480 from each) and conducted bioinformatic and microarray analyses of the expressed sequence tags (ESTs). In total, 873 ESTs (440 male and 433 female) were obtained, achieving a sequencing success of 91%The nucleotide sequences reported in this article (Tables 1–5) have been deposited in the EMBL, GenBank and DDJB databases under the Accession nos. AM157797–AM158083. Microarray analyses of 516 unique ESTs representing both gender-enriched libraries revealed differential hybridization for 391 of them (75·8%). Of these, 220 (56·3%) had significantly greater signal intensities in the female than in the male, and 154 (70%) of these were predicted to have homologues in C. elegans. These homologues were predicted to be involved in key biological processes, including embryonic nutrition, gametogenesis, molecular binding/transport or metabolism, nucleic acid synthesis and function, and signal transduction. Of the 171 ESTs with statistically higher signal intensities in male O. dentatum, 43·8% had homologues in C. elegans. These homologues included major sperm proteins (MSPs) or MSP-like molecules, keratin-like molecules, molecules involved in metabolism, PDZ domain-containing proteins, sugar binding proteins, protein kinases, serine proteases or protease inhibitors, molecules involved in proteolysis and other proteins, such as enzymes and various putative proteins. Of the 287 ESTs (from both gender-enriched cDNA libraries) with no known homologues in C. elegans, 50 (17·4%) had homologues in other nematodes, 8 had homologues in various other organisms and 104 (36·2%) had no homology to any sequence in current gene databases. The present study lays a foundation for the isolation and molecular, biochemical and functional characterization of selected genes from the gender-enriched cDNA archives established for O. dentatum.

The aim of the present study was to analyse the relation between parasitism and subsequent metallothioneins (MT) in the case of metal contamination. Experimental exposure of parasitized and unparasitized cockles (Cerastoderma edule) to cadmium (Cd) was performed, with the cockle as first or second intermediate host of 2 digenean species. After 7 days of Cd exposure in microcosms, cockles infected as first intermediate host by Labratrema minimus exhibited metal concentrations in tissues double that in uninfected cockles. Jointly, MT concentrations of parasitized cockles were not modified in comparison with uninfected individuals in which concentrations were increased 4·3-fold compared with controls. In cockles experimentally infected as the second intermediate host by Himasthla elongata, cadmium concentrations significantly increased again in parasitized cockles compared with uninfected individuals in contaminated conditions. Simultaneously, MT concentrations in healthy cockles increased, whereas they significantly decreased in parasitized individuals. Therefore, the presence of digenean parasites in Cd-exposed cockles leads to a maintenance or a decrease in MT concentrations compared with healthy individuals, whereas Cd accumulation in tissues is significantly increased. These experiments indicate a significant alteration of the protective effect of metallothioneins towards metals which could consequently enhance cockle vulnerability. Moreover, these results highlight the limit of the use of MT as a biomarker of metal pollution in field monitoring if parasitism is not taken into account.

Trichostrongylus tenuis eggs were counted in faeces from individually marked wild red grouse for 8 years. Egg counts varied seasonally and annually. In some years, a sudden increase in mid-April was consistent with delayed maturation of larvae which had overwintered in the birds in a hypobiotic state. A more gradual increase in summer was probably due to uninterrupted maturation of larvae ingested then. Despite 30-fold year-to-year variation in mean egg counts, relative differences in egg counts among known individuals within years tended to persist across years. Rainfall in previous summers explained much of the year-to-year variation in egg counts, probably because parasite recruitment was greatest during wet summers. Grouse density was only weakly related to worm egg counts. The data were not consistent with the hypothesis that the cyclic-type population fluctuation in red grouse numbers observed at the time of this study was caused by the parasites.

Antibodies against variable antigens expressed on the surface of Plasmodium falciparum-infected erythrocytes are believed to be important for protection against malaria. A target for these antibodies is the P. falciparum erythrocyte membrane protein 1, PfEMP1, which is encoded by around 50 var genes and undergoes clonal variation. Using agglutination and mixed agglutination tests and flow cytometry to analyse the recognition of variant antigens on parasitized erythrocytes by plasma antibodies from individuals living in Daraweesh in eastern Sudan, an area of seasonal and unstable malaria transmission, we show that these antibodies recognize different variant antigens expressed by parasites of different genotype. Comparing the levels and acquisition of antibody to variant antigens in pairs of parasite isolates expressing different variant types, there is a correlation between the acquisition of antibodies to some combinations of variant antigens but not to others. These results indicate that (1) a single infection will induce the production of antibodies recognizing several variants of surface-expressed antigens, (2) the repertoire of variable antigens expressed by different parasites is overlapping and the degree of overlap differs between isolates, and (3) the expression of at least some variant antigens is genetically linked.

This study examines the ability of an assay which measures the amount of a schistosome specific antigen (CAA) in the host circulation to reliably reflect relative worm burden. Mice were infected with 5 species of schistosome with a range of infection dose. The levels of serum CAA increased during schistosome maturation. In all species tested CAA levels correlated well with adult worm burden once the parasites achieved sexual maturity and remained relatively stable during the establishment of egg production. The amount of CAA produced varied between species but within each species CAA levels were proportional to worm numbers: no density-dependent effects on CAA levels were observed even when mice carried worm burdens that were very large relative to host size. T-cell deprivation of the host had no effect on the CAA/worm burden relationship in either Schistosoma mansoni or S. haematobium infections and the CAA equilibrium was unaltered in intact mice when reduction of worm fecundity occurred. These data support the use of the CAA as an accurate and robust estimate of relative schistosome burden in man.

Three IgM monoclonal antibodies, M22G11P, M7B7 and M22B3G, which reacted with the surface of Schistosoma mansoni schistosomula in an indirect fluorescent antibody assay, were found to recognize a polysaccharide-containing egg antigen previously designated K3. The monoclonal antibodies and a monospecific rabbit anti-K3 serum also recognized a crossreacting antigen in a crude cercarial antigen preparation. In an eosinophil-mediated schistosomulum killing assay, all three monoclonal antibodies significantly inhibited the level of killing produced by human infection serum. An IgG3 monoclonal antibody, M22C1C, which also recognized the egg antigen K3, did not inhibit eosinophil-mediated killing. However, when lower concentrations of human serum were used in the assay, this monoclonal antibody significantly enhanced the level of killing, despite having no capacity to induce eosinophil-mediated damage in the absence of human infection serum. On the basis of these and other results we suggest the possibility that antibodies to S. mansoni egg antigens which cross-react with the surface of the early post-penetration schistosomulum may influence the effective expression of antibody-dependent, eosinophil-mediated effector mechanisms in human infections.

The immune reaction of the mouse to the cestode, Hymenolepis microstoma, has been investigated. The mouse can carry a worm burden of up to 500 mg wet wt and there is no evidence either of rejection of the parasite by the mouse or a slowing down of growth rate of the mouse as a result of the parasite.

The nature of the antibody response has been investigated with regard to the type of antibody, onset of production, and titre.

The nature of the antibody is discussed together with the fact that there is no rejection of the parasite. The possibility that a cellular immune response might be necessary for rejection is also discussed.

I should like to express my thanks to Dr T. S. C. Orr of Fisons Research Laboratories, Loughborough, for many helpful comments and suggestions during the course of this work.

My thanks are due also to Professor C. A. Hopkins who put the facilities of the Wellcome Laboratory at my disposal at all times. My thanks, too, to Miss Gillian Moore whose technical assistance was invaluable.

The work was in part supported by a Grant from Fisons Ltd.

Drug development for paediatric applications entails a number of challenges, such as the wide age spectrum covered – from birth to adolescence – and developmental changes in physiology during biological maturation that influence the efficacy and toxicity of drugs. Safe and efficacious antiparasitic drugs for children are of pivotal importance given the large proportion of burden attributable to parasitic diseases in this age group, and growing efforts to administer, as widely as possible, antiparasitic drugs to at-risk populations, such as infants and school-aged children, often without prior diagnosis. The purpose of this review is to investigate whether antiparasitic drugs have been adequately studied for use in paediatrics. We approached this issue through a systematic review using PubMed and the Cochrane Central Register of Trials covering a period of 10 years and 8 months until the end of August 2010 to identify trials that investigated efficacy, safety and pharmacokinetic (PK) parameters of antiparasitic drugs for paediatrics. Overall, 269 clinical drug trials and 17 PK studies met our inclusion criteria. Antimalarial drugs were the most commonly studied medicines (82·6%). Most trials were carried out in Africa and children aged 2–11 years were the age group most often investigated. Additionally, we critically examined available drug formulations for anthelminthics and identified a number of shortcomings that are discussed. Finally, we shed new light on current proposals to expand ‘preventive chemotherapy’ to preschool-aged children and emphasise that new research, including risk-benefit analyses, are needed before such a strategy can be adopted more widely.