An analysis is presented of continuous data collected over 11 years based on 1902600 person/days of observation on the malaria experience of the people of Daraweesh, a village in eastern Sudan. Malaria transmission is hypo-endemic: the acquisition of clinical immunity with age is not as obvious as in more holo-endemic areas and malaria remained a problem in all age groups throughout the study. However, this population, who are of Fulani origin, showed a distinctly variable level of disease susceptibility. Thirty-two percent of the village never reported malaria symptoms or required malaria treatment while others experienced up to 8 clinical episodes over the 11 years of observation. Malaria incidence was clearly influenced by drought but much less obviously by rainfall. To what extent outbreak patterns are explicable in terms of anopheline factors, and to human immune factors, remains an interesting question for malaria modelling in this, and in other low transmission zones, such as the burgeoning urban areas of modern Africa.

Leishmania donovani, the most virulent species of Leishmania, is found in the South Asian region that harbours the majority of visceral leishmaniasis (VL) cases in the world. The traditionally accepted relationships between the causative species of Leishmania and the resultant disease phenotype have been challenged during recent years and have underscored the importance of revisiting the previously established taxonomy with revisions to its classification. The weak voice of the afflicted with decades of neglect by scientists and policy makers have led to the miserably inadequate and slow advancements in product development in the fields of diagnostics, chemotherapeutics and vector control that continue to hinder the effective management and control of this infection. Limitations notwithstanding, the regional drive for the elimination of VL initiated over a decade ago that focused on India, Nepal and Bangladesh, the three main afflicted countries in the Indian subcontinent is therefore, commendable, with the subsequent status reviews and restructuring of strategies possibly even more so. However, the renewed efforts would need to be combined with plans to combat new challenges in the South-Asian region that includes the emergence of atypical parasite variants, in order to realistically achieve the set goal of regional elimination of VL.

Sexually reproducing pathogens such as Cyclospora cayetanensis often produce genetically heterogeneous infections where the number of unique sequence types detected at any given locus varies depending on which locus is sequenced. The genotypes assigned to these infections quickly become complex when additional loci are analysed. This genetic heterogeneity confounds the utility of traditional sequence-typing and phylogenetic approaches for aiding epidemiological trace-back, and requires new methods to address this complexity. Here, we describe an ensemble of two similarity-based classification algorithms, including a Bayesian and heuristic component that infer the relatedness of C. cayetanensis infections. The ensemble requires a set of haplotypes as input and assigns arbitrary distances to specimen pairs reflecting their most likely relationships. The approach was applied to data generated from a test cohort of 88 human fecal specimens containing C. cayetanensis, including 30 from patients whose infections were associated with epidemiologically defined outbreak clusters of cyclosporiasis. The ensemble assigned specimens to plausible clusters of genetically related infections despite their complex haplotype composition. These relationships were corroborated by a significant number of epidemiological linkages (P < 0.0001) suggesting the ensemble's utility for aiding epidemiological trace-back investigations of cyclosporiasis.

This paper reports the effects of BnSP-7 toxin, a catalytically inactive phospholipase A2 from Bothrops pauloensis snake venom, on Leishmania (Leishmania) amazonensis. BnSP-7 presented activity against promastigote parasite forms both in the MTT assay, with IC50 of 58·7 μg mL−1 of toxin, and a growth curve, inhibiting parasite proliferation 60–70% at concentrations of 50–200 μg mL−1 of toxin 96 h after treatment. Also, the toxin presented effects on amastigotes, reducing parasite viability by 50% at 28·1 μg mL−1 and delaying the amastigote–promastigote differentiation process. Ultrastructural studies showed that BnSP-7 caused severe morphological changes in promastigotes such as mitochondrial swelling, nuclear alteration, vacuolization, acidocalcisomes, multiflagellar aspects and a blebbing effect in the plasma membrane. Finally, BnSP-7 interfered with the infective capacity of promastigotes in murine peritoneal macrophages, causing statistically significant infectivity-index reductions (P < 0·05) of 20–35%. These data suggest that the BnSP-7 toxin is an important tool for the discovery of new parasite targets that can be exploited to develop new drugs for treating leishmaniasis.

A total of 20 749 bulk tank milk (BTM) samples was collected in November 2008 from all over Germany, corresponding to 20·9% of all German dairy herds. The BTM samples were analysed for antibodies against Fasciola hepatica using the excretory–secretory (ES) ELISA. A geospatial map was drawn to show herd prevalences per postal code area. Various spatial risk factors were tested for potential statistical associations with the ELISA results in logistic regression supported by a geographical information system (GIS). The mean seroprevalence was 23·6% and prevalences in different German federal states varied between 2·6% and 38·4%. GIS analysis revealed statistically significant positive associations between the proportion of grassed area and water bodies per postal code area and positive BTM ELISA results. This can be explained by the biology of the intermediate host, the amphibious snail Galba (Lymnea) truncatula and the pasture-borne nature of fasciolosis. The full logistic regression model had a Pseudo-R2 of 22%, while the final model obtained by controlled stepwise model building revealed a Pseudo-R2 of 14%, indicating that additional, unrecorded factors and random effects contributed substantially to the occurrence of positive ELISA results. Considering the high seroprevalences in some areas and the economic impact of fasciolosis, farmers and veterinarians should be strongly advised to implement effective liver fluke control programmes.

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 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.

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.

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.

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.

1. Nearly a quarter of a million eggs of Sialis lutaria were collected at Cambridge in 1936. About 0·6 per cent of them were attacked by a parasite.

2. The egg-parasite of Sialis is distinct from Trichogramma evanescens, and is to be called T. semblidis (Aurivillius).

3. The male of Trichogramma semblidis occurs in two forms. Neither consists merely of imperfect or degenerate individuals of the other, for the two forms are equally large and differ constantly and fundamentally in several characters. The species, therefore, exhibits true dimorphism.

4. Rearing experiments involving isolated pure lines show that it is principally the host that determines which form of the parasite shall emerge. Males reared on Sialis are of the apterous form; those reared on three species of Lepidoptera are of the winged form.

5. The dimorphism of T. semblidis is discussed in relation to other examples of dimorphism in the Hymenoptera. It is shown to have several features of special interest.

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.

The strongest evidence for host specificity of mammalian trypanosomes comes from parasites of the subgenus Trypanosoma (Herpetosoma). Laboratory studies have shown that T. (Herpetosoma) species will not infect an alternative host. However, this has not been demonstrated in wild populations. We screened 560 bank voles (Clethrionomys glareolus) and 148 wood mice (Apodemus sylvaticus) for trypanosomes by PCR amplification of the 18S rRNA gene. In total, 109 (19%) bank voles and 12 (8%) wood mice were infected. A HaeIII restriction site was discovered that could be used to discriminate between T. (H.) evotomys of the bank vole and T. (H.) grosi of the wood mouse. All the parasites in the bank voles were identified as T. (Herpetosoma) evotomys by RFLP-PCR. Out of the 12 wood mouse infections 10 were due to T. grosi. Two of the wood mice were infected with parasites with a novel genotype that was most similar to those of T. evotomys and T. microti of voles. Fifty-six fleas collected from the rodents were also screened for trypanosomes; 9 were infected with T. evotomys and 1 with T. grosi. One of the fleas infected with T. evotomys was collected from a wood mouse.

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.

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.

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.

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.

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.

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.