The evolutionary history of leeches is employed as a general framework for understanding more than merely the systematics of this charismatic group of annelid worms, and serves as a basis for understanding blood-feeding related correlates ranging from the specifics of gut-associated bacterial symbionts to salivary anticoagulant peptides. A variety of medicinal leech families were examined for intraluminal crop bacterial symbionts. Species of Aeromonas and Bacteroidetes were characterized with DNA gyrase B and 16S rDNA. Bacteroidetes isolates were found to be much more phylogenetically diverse and suggested stronger evidence of phylogenetic correlation than the gammaproteobacteria. Patterns that look like co-speciation with limited taxon sampling do not in the full context of phylogeny. Bioactive compounds that are expressed as gene products, like those in leech salivary glands, have ‘passed the test’ of evolutionary selection. We produced and bioinformatically mined salivary gland EST libraries across medicinal leech lineages to experimentally and statistically evaluate whether evolutionary selection on peptides can identify structure-function activities of known therapeutically relevant bioactive compounds like antithrombin, hirudin and antistasin. The combined information content of a well corroborated leech phylogeny and broad taxonomic coverage of expressed proteins leads to a rich understanding of evolution and function in leech history.

This paper uses simple mathematical models and statistical estimation techniques to analyse the frequency distribution of microfilariae (mf) in blood samples from human populations which are endemic for lymphatic filariasis. The theoretical analysis examines the relationship between microfilarial burdens and the prevalence of adult (macrofilarial) worms in the human host population. The main finding is that a large proportion of observed mf-negatives may be ‘true’ zeros, arising from the absence of macrofilarial infections or unmated adult worms, rather than being attributable to the blood sampling process. The corresponding mf distribution should then follow a Poisson mixture, arising from the sampling of mf positives, with an additional proportion of ‘true’ mf-zeros. This hypothesis is supported by analysis of observed Wuchereria bancrofti mf distributions from Southern India, Japan and Fiji, in which zero-truncated Poisson mixtures fit mf-positive counts more effectively than distributions including the observed zeros. The fits of two Poisson mixtures, the negative binomial and the Sichel distribution, are compared. The Sichel provides a slightly better empirical description of the mf density distribution; reasons for this improvement, and a discussion of the relative merits of the two distributions, are presented. The impact on observed mf distributions of increasing blood sampling volume and extraction efficiency are illustrated via a simple model, and directions for future work are identified.

A cDNA encoding a β-galactoside-binding lectin (galectin) was identified by immunoscreening a Haemonchus contortus cDNA library with antisera from lambs vaccinated with a membrane protein complex (H-gal-GP) derived from the parasites' gut. The cDNA sequence, exhibiting a tandem repeat structure and designated Hco-gal-2, showed significant levels of similarity with galectins from several species of nematode as well as mammalian galectin type 4. Native galectin was preferentially extracted from the H-gal-GP complex and also from an insoluble membrane fraction prepared from adult worms using lactose–agarose affinity chromatography. The affinity-purified material had apparent molecular mass of around 35 kDa with 3 distinct bands visible on SDS–PAGE. All 3 bands were identified as galectins by reaction with antiserum raised to recombinant Hco-GAL-2 on Western blot. To determine whether H. contortus galectins have any protective capacity against infection lambs were vaccinated with affinity-purified galectin and subsequently given a single challenge infection. Vaccination did not confer any protection against infection with H. contortus as judged by faecal egg output or worm counts.

A method is described by which individual bed-bugs, weighing only 5 mg., can be accurately weighed, and their rate of loss of weight measured during starvation.

Fasting bed-bugs were kept for various periods at five temperatures, ranging from 8° C. to 37° C., and at four humidities—0, 30, 60 and 90 per cent. relative humidity—at each temperature. Analysis after the experiments showed that the same amounts of food reserves were used up at each humidity for one temperature, and, as more water was evaporated from those kept in dry air than from those in moist, the proportion of dry matter rose most rapidly in dry air. Protein was the main food reserve used.

Although the rate of loss of water was greatest in dry air, the rate of loss was relatively greater in moist air when the saturation deficiencies are compared. It appears that the insects conserve their water in dry air, but their surface area being so great in comparison with their volume, they cannot prevent all evaporation. This evaporation is at a rate nearly proportional to the saturation deficiency of the air.

In moist air water appears to be evaporated freely. It is suggested that the spiracles are kept closed more in dry air and less in moist, which accounts for the fact that the rate of evaporation is proportionately greatest in moist air.

A comparison is made between the results obtained with Cimex and Rhodnius.

It has been demonstrated that under prolonged experimental conditions lipid is utilized most quickly under optimal conditions of tonicity, gaseous exchange, pH and sensory stimulation. There is good evidence that activity may be an appreciable energy-consuming process. It has been deduced, however, that the low Reynold's number means viscous forces dominate locomotory energy consumption, and work done is proportional to the square of the velocity. Osmoregulation in hypotonic media and tolerance of hypertonic media do not require appreciable energy.

Locomotion is only possible in limited environmental conditions, and these may also be conditions of peak basal metabolism. Larvae are able to enter quiescence which is not energy-demanding, in poor conditions. Larvae can survive anaerobiasis, but finally die without reduction in lipid and cannot convert lipid to carbohydrate for anaerobic metabolism.

The help of Mrs Helen Foreman in staining the larvae and for statistical analyses, and of Mr J. M. Smith is greatly appreciated. I would like to thank Dr Elizabeth U. Canning for kindly providing the microdensitometer and Professor G. S. Nelson and Dr D. A. Denham for enabling us to establish A. tubaeforme in our cats. The generous support of the British Medical Research Council is much appreciated.

Biological control is understood here in the classical sense, which is precisely defined by De Bach (1964) as ‘the action of parasites, predators or pathogens in maintaining another organism's population density at a lower average than would occur in their absence’. This account consists of a survey of the principal causes of disease in nematodes, with a summary of the efforts made to use certain pathogens in practise and a discussion of nematode pathology with reference to destruction of plant pathogenic nematodes.

In this study, we conducted phylogenetic analyses of nematode parasites within the genus Dictyocaulus (superfamily Trichostrongyloidea). Lungworms from cattle (Bos taurus), domestic sheep (Ovis aries), European fallow deer (Dama dama), moose (Alces alces), musk ox (Ovibos moschatus), red deer (Cervus elaphus), reindeer (Rangifer tarandus) and roe deer (Capreolus capreolus) were obtained and their small subunit ribosomal RNA (SSU) and internal transcribed spacer 2 (ITS2) sequences analysed. In the hosts examined we identified D. capreolus, D. eckerti, D. filaria and D. viviparus. However, in fallow deer we detected a taxon with unique SSU and ITS2 sequences. The phylogenetic position of this taxon based on the SSU sequences shows that it is a separate evolutionary lineage from the other recognized species of Dictyocaulus. Furthermore, the analysis of the ITS2 sequence data indicates that it is as genetically distinct as are the named species of Dictyocaulus. Therefore, either this taxon needs to be recognized as a new species, or D. capreolus, D. eckerti and D. viviparus need to be combined into a single species. Traditionally, the genus Dictyocaulus has been placed as a separate family within the superfamily Trichostrongyloidea. The present molecular phylogenetic analyses support the placement as a separate family, but the current data do not support the placement of the Dictyocaulidae within the Trichostrongyloidea without a reassessment of the placement of the superfamily Strongyloidea. While D. eckerti has been regarded as the one and only lungworm species of cervids, this study showed that 4 host species including 3 members of Cervidae (moose, reindeer, red deer) and 1 Bovidae (musk ox) were infected with this parasite. Host ranges of D. viviparus (cattle), D. filaria (sheep) and D. capreolus (moose and roe deer) were more restricted. No clear pattern of co-evolution between the dictyocaulid taxa and their bovid and cervid hosts could be determined.

Dientamoeba fragilis is a pathogenic protozoan parasite that is implicated as a cause of human diarrhoea. A case-controlled study was conducted to determine the clinical signs associated with D. fragilis infection in children presenting to a Sydney Hospital. Treatment options are also discussed. Stool specimens were collected from children aged 15 years or younger and analysed for the presence of D. fragilis. In total, 41 children were included in the study along with a control group. Laboratory diagnosis was performed by microscopy of permanently stained, fixed faecal smears and by real-time PCR. Gastrointestinal symptoms were present in 40/41 (98%) of these children with dientamoebiasis, with diarrhoea (71%) and abdominal pain (29%) the most common clinical signs. Chronic gastrointestinal symptoms were present in 2% of cases. The most common anti-microbial used for treatment was metronidazole (n=41), with complete resolution of symptoms and clearance of parasite occurring in 85% of cases. A treatment failure rate occurred in 15% of those treated with metronidazole. Follow-up treatment comprised of an additional course of metronidazole or iodoquinol was needed in order to achieve complete resolution of infection and symptoms in this group. This study demonstrates the pathogenic potential of D. fragilis in children and as such it is recommended that all laboratories must routinely test for this organism and treat if detected.

Chloroquine-resistance in Plasmodium falciparum is associated with polymorphisms in a locus on or near the cg2 gene on chromosome 7, and in the pfmdr1 gene on chromosome 5. In this study we typed P. falciparum DNA from uncomplicated malaria cases in The Gambia in 1990, 1995 and 1996 for size polymorphism in the omega repeat of cg2, for sequence polymorphisms in pfmdr1 at codons 86 and 184, in dhfr at codon 108 and in the msp2 gene. Chloroquine sensitivity tests were conducted in vitro. A significant but incomplete association was found between the presence of the cg2 Dd2-like omega repeat size polymorphism and in vitro resistance, and between the tyr-86 allele of pfmdr1 and in vitro resistance. Furthermore there was strong linkage disequilibrium between the pfmdr1 asn-86 allele and the cg2 not Dd2-like omega repeat allele located on different chromosomes. In contrast, no linkage disequilibrium was found between these alleles and either the dhfr ser-108 allele or the msp2 IC sequence polymorphism. No significant linkage was measured between pfmdr1 asn-86 and phe-184 although these loci are separated only by 296 base pairs. Our results suggest that genetic elements linked to the cg2 and the pfmdr1 genes are important determinants of chloroquine resistance. It can be concluded that the observed linkage disequilibrium is maintained epistatically through selection by chloroquine.

Interleukin (IL)-13 and alternatively activated macrophages (AAMs) play an important role in liver granuloma and fibrosis of schistosomiasis. Paeoniflorin (PAE, C23H28O11) has been reported to have an anti-hepatic fibrosis effect in schistosomiasis; however, the mechanism has not been fully elucidated. In this study, we measured serum hyaluronic acid (HA) concentrations, liver granuloma diameter and volume density, fibrosis degree and expressions of IL-13, arginase-1 (ARG-1), nitric oxide synthase-2 (NOS-2), and phosphorylated signal transducer and activator of transcription 6 (p-STAT6) in mice liver of schistosomiasis. Then we detected expressions of specific biomarkers of AAMs and activity of Arg-1 in Kupffer cells (KCs) from infected and PAE-treated mice, or in KCs from uninfected mice, but exposed to rIL-13 in vitro. Finally, we observed expression of IL-13 signalling molecules in KCs and secretion of IL-13 from lymphocytes of infected and PAE-treated mice. Our results showed that during schistosomiasis, IL-13 expression and secretion increased with liver macrophages activated alternatively. PAE not only directly inhibited alternative activation of macrophages via reducing the phosphorylations of janus-activated kinase 2 (JAK2) and/or STAT6, leading to reduction of AAMs-related markers and Arg-1 activity, but also indirectly suppressed alternative activation of macrophages through decreasing secretion of IL-13. PAE might be a promising prophylactic agent for hepatic granuloma and fibrosis of schistosomiasis japonica.

1. Histomonas meleagridis was isolated in culture from the liver lesions of a hen suffering from “blackhead” (enterohepatitis). It has been cultivated at 36·5–37°C. for over a year.

2. Chicks, which had been reared free from protozoa, were inoculated per os or per anum, with cultures of the above strain of H. meleagridis. Eleven out of twelve birds became infected. Caecal lesions only were produced. This strain, although isolated from the liver lesions of a hen suffering from acute blackhead, showed no abnormal virulence in chicks.

3. Individuals of this strain of H. meleagridis showed amoeboid movement but were also flagellate. Normally the protozoon was uninucleate, but binucleate forms were common, and tri- and quadrinucleate forms occurred more rarely. One flagellum arose from each nucleus.

4. During division the flagellum disappears. The method of nuclear division was similar to that of Trichomonas.

5. A resistant phase was never seen in the cultures.

1. The emergence of the gametocytes of Plasmodium gallinaceum from the erythrocytes and the exflagellation of the male gametocyte were inhibited completely when infected blood was exposed to an atmosphere of 5 % CO2 and 95 % O2, or 5 % CO2 and 95 % N2. When these gas mixtures were replaced by air, the gametocytes emerged from the erythrocytes and the male gametocytes exflagellated after approximately the same interval as they did in newly drawn blood exposed to air, or in blood ingested by mosquitoes. If pure CO2 were used instead of the gas mixtures containing 5% CO2, the development of the gametocytes, after the replacement of the gas by air, was uncertain.

2. The emergence of the gametocytes and exflagellation of the male gametocytes proceeded normally when parasitized blood was exposed to an atmosphere of N2.

3. The pH of freshly drawn normal chick blood was 7·38–7·46. The pH of blood exposed to air rose over a 20 min. period of observation, the highest pH recorded being 7·97. No significant difference in pH was observed between normal and heavily infected blood. It was not possible to correlate the stages of development of the gametocytes with precise values of pH of the blood.

4. The development of the gametocytes proceeded normally when parasitized blood was mixed with isotonic alkaline Tris buffer to give a pH of approximately 8·0; but it was inhibited, though not completely, when the pH was reduced below that of freshly drawn blood by the addition of isotonic acid buffer. The inhibitory effect of the acid buffer could be completely but not invariably reversed by alkaline buffer.

5. 5 % CO2 had no inhibitory action upon the gametocytes if the pH of the blood-buffer mixture was 7·62, but when it was 7·20 the inhibitory effect of the gas was complete.

6. The emergence of the gametocytes from the corpuscles and the exflagellation of the male gametocytes were completely inhibited when washed, parasitized corpuscles were suspended in isotonic buffer pH 7·78 or 8·20, but this inhibition was completely reversed when the corpuscles were resuspended in plasma. It is concluded that a factor present in plasma is necessary for the development of the gametocytes.

7. Further evidence that the pH of the blood, alone, is not the only factor affecting the emergence of the gametocytes and exflagellation of the male gametocytes was obtained from birds treated intravenously with Diamox. When blood from such birds was exposed to air the gametocytes emerged from the corpuscles and exflagellation took place, although the pH of the blood was as low as, or lower than, that of freshly drawn blood.

8. The emergence of the gametocytes from the erythrocytes and exflagellation of the male gametocytes were not stimulated by secretions from the stomachs or salivary glands of gorged or unfed mosquitoes.

9. The lowest measurement of pH of blood from mosquitoes' stomachs was 7·47 and the highest 7·90, the mean being 7·68, which is slightly higher than that of freshly drawn chick blood. No correlation could be found between the pH of the blood and the length of time since its ingestion by the mosquito.

Acanthocotylid (monogenean) parasites inhabit the skin of rays, and the lack of cilia on the infective larvae of these parasites may be an adaptation to the host's bottom-living habits.

Freshly hatched larvae must remain on the sea-bottom until a ray settles on top of them, when the larvae then have the opportunity to attach themselves to the host's ventral surface. Acanthocotyle lobianchi, which infects Raia montagui and R. clavata at Plymouth, becomes sexually mature on the host's ventral surface and rarely wanders from it, but A. elegans, which is found on R. clavata only, migrates to the dorsal surface of the host before reaching sexual maturity.

The larvae of acanthocotylids use their haptoral hooklets to attach themselves to the host's epidermis, but as the parasites increase in size the load on these hooks becomes acute. This load is relieved not as in other monogeneans by the development of hamuli but by the transformation of the posterior third of the larval body into an accessory ‘pseudohaptor’.

I am obliged to the Director and Staff of the Plymouth Laboratory for laboratory facilities and to Mr J. E. Green for his interest and help on many occasions.

The participation of neutrophil granulocytes in the cellular reaction to skin microfilariae of Onchocerca volvulus was studied by immunohistochemistry. Skin biopsies were obtained from adult Liberian and Ugandan patients with generalized onchocerciasis after exposure to topically applied diethylcarbamazine (DEC) and from untreated patients. After DEC many damaged microfilariae were observed either in dermal infiltrates or in epidermal microabscesses consisting both of neutrophils and eosinophils. Infiltrates and microabscesses contained some intact granulocytes and many neutrophils releasing myeloperoxidase, elastase, lactoferrin, defensin, lysozyme, α1-antitrypsin and α1-antichymotrypsin. Eosinophils discharged peroxidase and cationic proteins. Released granule proteins and remnants of disrupted granulocytes were found on the surface and in close proximity of damaged microfilariae in dermal infiltrates and epidermal microabscesses. In larger microabscesses neutrophils were predominant. These observations show that neutrophils and not only eosinophils recruit, accumulate, localize around and release their helminthotoxic granule proteins such as myeloperoxidase onto or closely around skin microfilariae of O. volvulus after topical DEC administration. The association between these processes and the damage of the microfilariae indicated that neutrophils together with eosinophils attack and damage microfilariae of O. volvulus after DEC treatment in the skin.

1. Frogs were collected from a single area in the West Riding of Yorkshire and examined for adult helminth parasites. The following species were found: Polystoma integerrimum, Gorgoderina vitelliloba, Haplometra cylindracea, Dolichosaccus rastellus, Rhabdias bufonis, Cosmocerca ornata, Oswaldocruzia filiformis, Aplectana acuminata and Acanthocephalus ranae.

2. The seasonal incidence and intensity of infection was studied by monthly examinations of 2413 frogs over a period of 4 years. The highest incidence of parasitization by helminths occurred in the autumn. In general, when the incidence was high, the intensity of infection was also high.

3. The incidence of infection was generally higher in male than in female frogs. This effect of the host's sex was much more marked immediately before the breeding season than at any other time of the year.

4. Possible reasons for these variations in levels of infection are discussed.

Giardia duodenalis is a ubiquitous flagellated protozoan parasite known to cause giardiasis throughout the world. Potential transmission vehicles for this zoonotic parasite are both water and food sources. As such consumption of water contaminated by feces, or food sources washed in contaminated water containing parasite cysts, may result in outbreaks. This creates local public health risks which can potentially cause widespread infection and long-term post-infection sequelae. This paper provides an up-to-date overview of G. duodenalis assemblages, sub-assemblages, hosts and locations identified. It also summarizes knowledge of potential infection/transmission routes covering water, food, person-to-person infection and zoonotic transmission from livestock and companion animals. Public health implications focused within the UK, based on epidemiological data, are discussed and recommendations for essential Giardia developments are highlighted.

Despite metabarcoding being widely used to analyse bacterial community composition, its application in parasitological research remains limited. What interest there has been has focused on previously intractable research settings where traditional methods are inappropriate, for example, in longitudinal studies and studies involving endangered species. In settings such as these, non-invasive sampling combined with metabarcoding can provide a fast and accurate assessment of component communities. In this paper we review the use of metabarcoding in the study of helminth communities in wild mammals, outlining the necessary procedures from sample collection to statistical analysis. We highlight the limitations of the metabarcoding approach and speculate on what type of parasitological study would benefit from such methods in the future.

1. The life cycle of Trypanosoma avium in both its hosts is described.

2. In the vector (Ornithomyia avicularia) it undergoes a cyclical development in the alimentary canal. Multiplication occurs while the flagellate is in the crithi-dial stage, and, finally, pyriform haptomonad crithidia appear in the insect's hind-gut: these change into the infective metacyclic trypanosomes.

3. After penetrating the mucous membranes of the bird (following its ingestion of the louse-fly), the metacyclic trypanosomes probably invade the lymph system, and there develop (by growth alone) into the large forms seen in the bird's blood some 18–24 hr. later.

4. The trypanosomes persist in their natural hosts (but not in canaries) throughout the winter, more-or-less restricted to the bone-marrow. In the spring they reappear in the peripheral blood.

The Helminths herein reported are of importance because of their economic and taxonomic relations. To point this out, it is only necessary to mention Haemonchus, whose relation to the Bovidae and Ovidae is equivalent to those of Necator and Ancylostoma to the human host.

Some are well-known roundworms having a world-wide distribution as parasites of animals, and are listed only on account of locality and museum interest; others, especially certain rare forms from uncommon hosts, are of greater interest and are discussed more fully. Certain details, at one time thought not.to be necessary and hence neglected are added because to-day they are indispensable for specific designation.

Because of the abundance of material, it has been possible to supplement accounts given by other authors and to correct some errors due, no doubt, to poor or too few specimens. Several changes in systematic position of known forms and confirmation of others are made.

A new name (D. histrix) is proposed for Dirofilaria subcutanea (Linstow, 1899) Boulenger, 1920. Eustrongylides larvae, of Ciurea, J. 1924, are included under the pre-adult stage of a new species (Eustrongylides wenrichi) because both are alike and their characters fit no other known species. New information is added about Trypanoxyuris trypanuris Vevers, 1923, and Cyrnea coloni Cram, 1927, amending their descriptions.

Descriptions and illustrations of seven new species in as many genera are given. They are Acuaria (Dispharynx) resticula from a groove-billed ani, Ascaridia petrensa from a partridge, Dirofilaria spinosa from a porcupine, Physaloptera multiuteri from a monkey, Subulura pennula from a quail, Spironoura procera from a terrapin, and the above-mentioned pre-adult Eustrongylides wenrichi from a stream pike, brook-trout, calico bass, sunfish, and a frog.

In all there are 162 determinations in 38 genera and 56 species, including new ones, from 150 hosts involving 117 different host species.

Superparasitism and significant cases of parasitism are pointed out because they are of interest to one concerned with incidence and degree of infestation. Numerous records of new host-parasite relations and new localities will be of interest to students of distribution.