It is a common experience that mosquito larvae when they are brought into a laboratory to undergo their development, often fail to develop normally. At times a high mortality takes place, or the larvae lapse into a condition of suspended development continuing as larvae for months. The latter phase usually ends in death before pupation can take place. I have been puzzled to account for these manifestations for a very long time, and have conducted various experiments in the hope of discovering the cause. The general opinion on the matter, I think, is that there is “something wrong with the food supply,” but as a matter of fact larvae supplied with an ample diet often show the same state of affairs.

In previous papers one of us (Keilin, 1915, 1917) has shown that among cyclorrhaphous dipterous larvae there is a remarkable correlation between the anatomical structure of the larvae and their mode of life. Although the mode of life of the larvae is in correlation with such anatomical features as thickness and hardness of the body-wall, the development of sensory organs on the head, and the structure of the alimentary canal, it is in the bucco-pharyngeal armature that the most obvious and important adaptations are to be found. The most important of these adaptations may be mentioned briefly. In certain cyclorrhaphous dipterous larvae the ventral wall of the basal sclerite of the bucco-pharyngeal armature has a number of longitudinal ridges projecting into the lumen of the pharynx. These ridges are usually Y-shaped at their free borders, and form a series of longitudinal channels in the ventral region of the pharynx. In other cyclorrhaphous dipterous larvae such ridges are absent and the ventral wall of the pharynx is smooth. This character allows the larvae to be divided into two groups—“all cyclorrhaphous dipterous larvae parasitic on the most diverse animals or on plants, as well as carnivorous larvae, and larvae which suck the blood of mammals, never have ridges in their pharynx; on the contrary, ridges are always present in saprophagous larvae” (Keilin, 1915). All the larvae which are devoid of ridges and are either parasitic, carnivorous, pass their whole life in the uterus of the female, or are phytophagous, may be united into the group of biontophagous; all larvae which have ridges are saprophagous.

The uptake kinetics of a 14C-labelled trypanocidal compound isometamidium chloride (SamorinR, RMB Animal Health Ltd, UK) was measured in drug-resistant and drug-sensitive Trypanosoma congolense. It was established that drug uptake was significantly more rapid and quantitatively greater in drug-sensitive parasites. There was clear evidence that drug uptake in both the resistant and sensitive trypanosomes was by a specific, receptor-mediated process. This specific drug transport was energy-dependent, being sensitive to metabolic inhibition with SHAM/glycerol. Significant differences in drug transport were observed which could be correlated with resistance to isometamidium. The optimal pH for drug accumulation was lowered in the resistant trypanosomes; this finding, along with an observed change in specificity for the related compound homidium bromide, suggested that the specific receptor for isometamidium is altered in the resistant trypanosomes, possibly resulting in a reduction in drug uptake. In addition to these alterations in drug uptake, efflux of isometamidium also appears to occur in the resistant trypanosomes. Both a reduction in incubation temperature and metabolic inhibition increased the level of trypanosome-associated isometamidium in the resistant parasites. This was in contrast to observations using drug-sensitive parasites. Furthermore, the addition of calcium flux-modulating agents to the incubation medium also resulted in an increase in accumulation by the resistant parasites.

We measured seasonal changes in the prevalence of haematozoa (Leucocytozoon fringillinarum, Haemoproteus fringillae, and Trypanosoma avium) in free-ranging White-winged Crossbills, Loxia leucoptera, over 1·5 year in Fairbanks, Alaska, USA. This prevalence was low during early winter. L. fringillinarum prevalence increased in late winter/early spring, in the absence of vectors, suggesting relapse of latent infection. By contrast, the prevalence of T. avium and H. fringillae did not increase until mid-spring, coincident with the emergence of putative vectors and suggestive of new inoculations. The winter breeding period was not associated with lower body condition or elevated blood heterophil/lymphocyte ratios than the summer post-breeding period. Thus, birds unlikely perceived their breeding effort as particularly stressful. Adult males in May and June had low plasma testosterone and their blood prevalence of L. fringillinarum, but not other haemoparasites, was higher than in adult females. This difference may have resulted from sex differences in behaviour and/or plumage colouration – bright red in males, dull green/yellow in females. Species in which reproduction and vector abundance are seasonally dissociated may constitute important models for investigating the respective contribution of reproductive hormones, breeding effort, and vector abundance to patent and latent hemoparasitic infections and to new inoculations.

Understanding the origin of invasive parasites and ecological transmission barriers on the distribution of mosquito-borne pathogens is enriched by molecular phylogenetic approaches now that large databases are becoming available. Here we assess the biogeographical relationships among haemosporidian blood parasites and an avian host, the New Zealand bellbird (Meliphagidae, Anthornis melanura). Four Plasmodium haplotypes were identified among 93 infected bellbirds (693 screened) using nested PCR of a mitochondrial DNA cytochrome b gene fragment. The most common lineage, LIN1 (11%), is confined to northern New Zealand and falls within a known clade of Plasmodium (subgenus Novyella) sp. infecting Australian meliphagids. LIN1 differs within that clade by 4 9% sequence divergence suggestive of an endemic lineage to New Zealand. The most widespread lineage, LIN2 (2%), is an exact match with a global cosmopolitan (P. elongatum GRW06). Two rare lineages, LIN3 and LIN4 are less abundant, geographically restricted within New Zealand and have <1% sequence divergence with P. (Novyella) sp. (AFTRU08) and P. relictum (LINOLI01) documented from Africa. For the first time, we provide invaluable information on possible rates of entry of invading parasites in New Zealand and their distribution from temperate to cold environments.

The following observations were made upon serial sections of a new monogenetic trematode, Hexacotyle extensicauda, which the writer has described in a previous paper (Dawes, 1940).

Many parasites, including all known viruses, characteristically lead an intracellular existence, and are known as ‘obligatory intracellular parasites’. It is, however, obvious that—whether the parasite is a virus, a bacterium, or a protozoon— transmission of infection from host to host, or from cell to cell within a single host, must involve an extracellular stage, however short in duration. This extracellular stage is, for the purpose of therapeutics of highest importance, since evidence accumulates that within the protecting walls of a cell parasites are relatively protected against chemotherapeutic agents and antibiotics, while susceptible to their action in the extracellular phase.

The histological changes in the gut of Chrysops silacea during the digestion of blood are the same as those described by Cragg in Tabanus.

Digestive enzymes are confined to the posterior half of the mid-gut. They comprise an active invertase, a weak amylase and an active tryptase and peptidase. These results are compared with those in Glossina and Calliphora.

The functions of the crop are discussed.

A main feature of the data here presented is the number of new records. For the sake of brevity these are tabulated below, under their respective headings.

Another feature is the wide geographical distribution of a large percentage of the parasites herein recorded, particularly of such forms as Zoogonoides viviparus (Olsson), Derogenes varicus (Mueller) and Hemiurus communis Odhn. The former has been recorded for St Andrews, Millport, Aberdeen, Plymouth, Northumberland, Liverpool, Galway, and also for foreign seas. Derogenes varicus has been recorded for St Andrews, Millport, Plymouth, Aberdeen, Northumberland, Galway, and for foreign seas. Hemiurus communis has been recorded for St Andrews, Millport, Plymouth, Northumberland, Liverpool, Aberdeen, Galway, and for foreign seas.

This suggests that the intermediate host of the larval stages of these parasites must be some common marine form, in all probability an invertebrate, which itself enjoys a very wide geographical distribution.

A further feature is the tendency of certain parasites to infect a variety of fish, the more notorious being Derogenes varicus (Mueller) and Hemiurus communis Odhn. Of the twenty-six species of marine fishes examined at Galway, eleven (42 per cent.) were found to harbour Derogenes various. The infected fishes were the bib (G. luscus), cod (G. morrhua), pollack (G. pollachius), dab (Pleuronectes limanda), plaice (P. platessa), tub (Trigla hirundo), grey gurnard (T. gurnardus), brill (Rhombus laevis), hake (Merluccius vulgaris), common sole (Solea vulgaris), common sea bream (Sparus centrodontus).

Hemiurus communis was found parasitising eight species of fish, i.e. 31 per cent, of the total number of species examined. The hosts affected were the bib (G. luscus), whiting (G. merlangus), cod (G. morrhua), pollack (G. pollachius), flounder (P. flesus), tub (T. hirundo), plaice (P. platessa), and the common sea bream (S. centrodontus).

At the moment it is a little premature to prophesy to what extent the discovery of encysted specimens of Prosorhynchus crucibulum (Rud.) in the gill tissues of the cod (Gadus morrhua) will assist in elucidating the life-history of this parasite. Mature specimens of Prosorhynchus crucibulum have previously been recorded as occurring in the alimentary canal of the conger eel (Conger niger). The writer discovered partly digested specimens of small cod to form a considerable bulk of the stomach contents of the conger eel.

Cryptosporidium species are protozoan parasites that infect humans and a wide variety of animals. This study was aimed at identifying Cryptosporidium species and genotypes isolated from avian hosts. A total of 90 samples from 37 different species of birds were collected throughout a 3-month period from April 2008 to June 2008 in the National Zoo of Kuala Lumpur, Malaysia. Prior to molecular characterization, all samples were screened for Cryptosporidium using a modified Ziehl-Neelsen staining technique. Subsequently samples were analysed with nested-PCR targeting the partial SSU rRNA gene. Amplicons were sequenced in both directions and used for phylogenetic analysis using Neighbour-Joining and Maximum Parsimony methods. Although 9 (10%) samples were positive for Cryptosporidium via microscopy, 8 (8·9%) produced amplicons using nested PCR. Phylogenetic trees identified all the isolates as Cryptosporidium parvum. Although C. parvum has not been reported to cause infection in birds, and the role of birds in this study was postulated mainly as mechanical transporters, these present findings highlight the significant public health risk posed by birds that harbour the zoonotic species of Cryptosporidium.

Immunoprophylactic products against neosporosis during pregnancy should induce an appropriately balanced immune response. In this respect, OprI, a bacterial lipoprotein targeting toll like receptor (TLR)2, provides promising adjuvant properties. We report on the manipulation of the innate and the T-cell immune response through the fusion of OprI with the Neospora caninum chimeric protein Mic3-1-R. In contrast to Mic3-1-R, OprI-MIC3-1-R significantly activated bone-marrow dendritic cells from naïve mice. Mice immunized with OprI-Mic3-1-R induced an immune response with mixed T helper (Th)1 and Th2 properties (high levels of both immunoglobulin (Ig)G1 and IgG2a and of interleukin (IL)-10, IL-12(p70) and interferon-γ responses) whereas Mic3-1-R+saponin induced a clear Th2-biased response (low IgG2a and high IL-4 and IL-10). After mating and challenge with N. caninum, increased expression of interferon-γ was only found in placentas from OprI-Mic3-1-R immunized dams. However, no protection against vertical transmission and neonatal mortality was observed in either of the two groups. These results indicated that more exhaustive studies must be done to elucidate the immune mechanisms associated with transplacental transmission. Antigen linkage to TLR2-ligands, such as OprI, is a useful tool to investigate this enigma by reorienting the innate and adaptive immune responses against other candidate antigens in future studies.

Acquisition of acute toxoplasmosis during the first trimester of pregnancy can have catastrophic consequences for the foetus. Diagnosis is routinely based on the detection of maternal Toxoplasma gondii – antibodies using whole parasite extracts as detection antigen. While such assays are sensitive, they show no specificity for the stage of infection. We hypothesized diagnosis might be improved using recombinant antigens for detection, particularly if antibodies to certain antigen(s) were associated with early or late stages of infection. To address this, protein microarrays comprising 1513 T. gondii exon products were probed with well-characterized sera from seronegative (‘N’) controls, and acute (‘A’), chronic/IgM-persisting (‘C/M’) and chronic (‘C’) toxoplasmosis cases from Turkey. Three reactive exon products recognized preferentially in A infections, and three recognized preferentially in C/M infections, were expressed in Escherichia coli and tested for discrimination in IgG ELISAs. The best discriminators were exon 1 of TGME49_086450 (GRA5) which detected C/M infections with 70·6% sensitivity and 81·8% specificity, and exon 6 of TGME49_095700 (ubiquitin transferase domain-containing protein) which detected A infections with 84·8% sensitivity and 82·4% specificity. Overall, the data support a recombinant protein approach for the development of improved serodiagnostic tests for toxoplasmosis.

1. Seven organic sulphur compounds likely to be produced in the breakdown of cystine have been tested under field conditions as blowfly attractants. Two of them, ethyl mercaptan and dimethyl di-sulphide, when mixed with hydrogen sulphide or carbon dioxide formed powerful attractants for females of the blowflies Lucilia caesar (and L. illustris) and L. sericata.

2. In the majority of trials 10 ml. 0·2% ethyl mercaptan mixed with 10 ml. freshly saturated hydrogen sulphide solution was used as the control attractant. As a standard in field-trapping studies this material overcomes many of the disadvantages of meat baits.

3. Sodium carbonate, sodium bicarbonate, ammonium hydroxide, ammonium carbonate and indole, at various concentrations, did not activate the organic compounds. Furthermore, when added to the ethyl mercaptan-hydrogen sulphide preparation they did not increase its activity.

4. In the present experiments oviposition was rarely induced. When it did occur it was associated with the presence of indole.

5. L. caesar responded to attractants placed 2 ft. from the ground as well as to the same materials placed on the ground. Height alone, therefore, was not responsible for the fact that L. caesar did not respond to the attractants when they were placed on sheep.

6. The responses of blowflies to chemical attractants was linked with climatic conditions. Thus, under certain conditions Calliphora spp., particularly C. vomitoria, responded to these attractants.

7. The results obtained in the present investigation emphasize the attractive nature of sulphur-containing compounds and the possible importance of hydrogen sulphide and carbon dioxide as sensitizing agents of such compounds on sheep.

During three decades, only about 20 new drugs have been developed for malaria, tuberculosis and all neglected tropical diseases (NTDs). This critical situation was reached because NTDs represent only 10% of health research investments; however, they comprise about 90% of the global disease burden. Computational simulations applied in virtual screening (VS) strategies are very efficient tools to identify pharmacologically active compounds or new indications for drugs already administered for other diseases. One of the advantages of this approach is the low time-consuming and low-budget first stage, which filters for testing experimentally a group of candidate compounds with high chances of binding to the target and present trypanocidal activity. In this work, we review the most common VS strategies that have been used for the identification of new drugs with special emphasis on those applied to trypanosomiasis and leishmaniasis. Computational simulations based on the selected protein targets or their ligands are explained, including the method selection criteria, examples of successful VS campaigns applied to NTDs, a list of validated molecular targets for drug development and repositioned drugs for trypanosomatid-caused diseases. Thereby, here we present the state-of-the-art of VS and drug repurposing to conclude pointing out the future perspectives in the field.

The parasitic roundworms Strongyloides stercoralis (in man) and Strongyloides ratti (in rats) employ environmentally controlled XX/XO sex determination with a pair of X chromosomes and two pairs of autosomes. Strongyloides papillosus (in sheep) has only two pairs of chromosomes, one of which combines the genetic material homologous to the S. ratti chromosomes X and I. This species creates males through the elimination of one copy of the portion related to the X chromosome (chromatin diminution). It is not clear which one of these two sex-determining mechanisms is ancestral. We demonstrate that Strongyloides vituli (in cattle) has two pairs of chromosomes like its very close relative S. papillosus whereas Parastrongyloides trichosuri, a closely related out-group to Strongyloides spp. in Australian brushtail possums, has three chromosome pairs and employs XX/XO sex determination. The X chromosome of P. trichosuri is homologous to the X chromosome of S. ratti. Our data strongly suggest that the last common ancestor of Strongyloides spp. and Parastrongyloides spp. had two pairs of autosomes along with two or one X chromosome in females and males, respectively. The situation with two pairs of chromosomes is likely derived and occurred through the fusion of the X chromosome with an autosome.

Franz cells (2-chambered, air/fluid phase static diffusion devices, previously used for the study of drugs across viable human skin) are utilized for the first time to investigate the process of infection of human skin by Schistosoma mansoni cercariae. Skin obtained from cosmetic surgery sources was used in the Franz cells to describe the temporal dynamics of the early interaction of cercariae with skin. At 38 °C, about 50% of cercariae applied in water to the epidermal surface of the skin were irreversibly attached within 1 min and after 5 min about 85% were similarly irrecoverable. The technique also provides the means of following the early penetration path of cercariae by histological methods. Franz cell results on the dynamics of attachment/early penetration have been compared with those obtained using artificial skin equivalents and non-human mammalian skin models in the context of the physical and chemical differences between these systems and viable human skin. It is concluded that Franz cells provide a convenient system for directly investigating the early phases of S. mansoni cercariae interaction with human skin.

In case of cercarial dermatitis after exposure to fresh water lakes, managers responsible for bathing water quality wish to confirm the presence of Trichobilharzia, which substantiates taking measures to protect bathers from further exposure. A novel approach, including concentration of suspected water samples by filtration and PCR detection of the parasite, is proposed. This approach has been applied to bathing sites with a history of cercarial dermatitis, sampled from 2005 to 2008. Examination of snails, the standard procedure for confirmation of the parasite's presence, and analysis of water samples, appear to be complementary procedures that enhance the chance of parasite detection in implicated bathing water. Water analysis is particularly valuable when snails cannot be found; it confirmed the presence of Trichobilharzia on 25% of sampling days with reported skin conditions and no snails found. PCR of the ToSau3A repeat directly confirmed the parasite in the water. The application of the combination of analysis of water samples and examination of snails is suggested when cases of (presumptive) cercarial dermatitis are reported or when lakes with a history of cercarial dermatitis are inspected prior to the bathing season, in order to guide interventions to prevent (further) cases of swimmers' itch.

Scuticociliatosis is a severe disease in farmed flatfish. However, the causative agent is not always accurately identified. In this study, we identified two isolates of scuticociliates from an outbreak in cultured fine flounder Paralichthys adspersus. Scuticociliate identification was based on morphological data, examination of life stages and the use of molecular approaches. The isolates were compared with a strain of Philasterides dicentrachi from turbot Scophthalmus maximus and with a strain deposited in the American Type Culture Collection as Miamiensis avidus ATCC® 50180™. The use of morphological, biological and molecular methods enabled us to identify the isolates from the fine flouder as P. dicentrarchi. Comparison of P. dicentrachi isolates and M. avidus revealed some differences in the buccal apparatus. Unlike P. dicentrarchi, M. avidus has a life cycle with three forms: macrostomes (capable of feeding on P. dicentrarchi), microstomes and tomites. Additionally, we found differences in the 18S rRNA and α- and β-tubulin gene sequences, indicating that P. dicentrarchi and M. avidus are different species. We therefore reject the synonymy/conspecificity of the two taxa previously suggested. Finally, we suggest that a combination of morphological, biological, molecular (by multigene analysis) and serological techniques could improve the identification of scuticociliates parasites in fish.

Pentameric ligand-gated ion-channels rapidly transduce synaptic neurotransmitter signals to an electrical response in post-synaptic neuronal or muscle cells and control the neuromusculature of a majority of multicellular animals. A wide range of pharmaceuticals target these receptors including ethanol, nicotine, anti-depressants and other mood regulating drugs, compounds that control pain and mobility and are targeted by a majority of anthelmintic drugs used to control parasitic infection of humans and livestock. Major advances have been made in recent years to our understanding of the structure, function, activity and the profile of compounds that can activate specific receptors. It is becoming clear that these anthelmintic drug targets are not fixed, but differ in significant details from one nematode species to another. Here we review what is known about the evolution of the pentameric ligand-gated ion-channels, paying particular attention to the nematodes, how we can infer the origins of such receptors and understand the factors that determine how they change both over time and from one species to another. Using this knowledge provides a biological framework in which to understand these important drug targets and avenues to identify new receptors and aid the search for new anthelmintic drugs.