Current chemotherapeutic agents for leishmaniasis have several disadvantages interfering with the effective treatment and therefore more and better antileishmanial drugs are needed. Discovery of candidates for leishmaniasis treatment requires not only accurate and precise methodologies but also well-known biological system to measure infectivity of parasites and antileishmanial activity of the new compounds. Significant variation in the in vitro and in vivo infectivity and sensitivity to established and experimental drugs in Leishmania strains are reported. This work reports the in vitro biological behavior and antileishmanial drugs sensitivity of different green fluorescent protein transfectant Leishmanias strains. The in vitro growth kinetic and infectivity to U937 cells vary slightly in the Leishmania transfectant strains in comparison with their correspondant wild-type. However, the insertion of the pIR3(-)-eGFP may affect the sensitivity of the parasites to meglumine antimoniate (MA) and miltefosine but not to amphotericin B (AMB) and pentamidine isethionate. In consequence, AMB or pentamidine isethionate but not MA or miltefosine should be used as antileishmanial control drugs during in vitro assays of antileishmanial activity. Furthermore, is recommended to test compounds against more than one Leishmania strain in order to verify that the antileihmanial activity of these compound is similar among species.

A detailed morphological investigation of the anterior sensory organs, the nerve ring and a glomerulus-like structure in male Onchocerca volvulus was performed by means of electron microscopy. The 8 head papillae are arranged in the common 4 + 4 pattern of most filarial worms in circles around the mouth opening. The amphidial openings are found between the circles of inner and outer papillae on both sides of the mouth. Inside, several additional nerve axons are seen in the tissue of the anterior tip not related to one of the identified papillar structures. The inner and outer papillae exhibit a remarkably different fine structure, and are part of a complex system of at least 2 different receptor cell types at the anterior tip of the worm. The amphidial channel contains 8 modified cilia; accessory axons are associated with the cytoplasm of the sheath cell. The anterior nerve ring of male worms is located about 150 µm posterior from the outermost tip of the head region. It consists of several fibres coiled around the oesophagus. The comparison of the fine structure of the central nervous system did not show the expected morphological differences associated with the heterogeneous age distribution in the natural worm population. This was in contrast to previous findings with respect to tissues in different parts of the worm. The study also provides the first evidence that suggests the existence of an excretory organ in a filarial worm in the region of the anterior nerve ring. Paired glomerulus-like structures in the lateral chords and a canal formed by a projection of the basal zone of the cuticle were identified.

The protozoan parasite Toxoplasma gondii produces a family of microneme proteins that are thought to play diverse roles in aiding the parasite's intracellular existence. Among these, TgMIC2 has a putative function in parasite adhesion to the host cell to initiate the invasion process. The invasion process may be localized and inhibited by monoclonal antibodies against the protein(s) involved. Here we report on the construction of a phage-displayed single-chain variable fragment (scFv) library from mice immunized with whole T. gondii parasites. The library was subsequently panned against recombinant TgMIC2 (rpTgMIC2) and 2 different groups of antibody clones were obtained, based on fingerprinting and sequencing data. The expressed recombinant scFv antibody was able to recognize rpTgMIC2 in a Western blot detection experiment. These results show that the phage display technology allows quick and effective production of monoclonal antibodies against parasite antigens. By panning the scFv-displayed library, we should be able to obtain a plethora of multi-functional scFv antibodies towards T. gondii proteins.

Cyclic GMP (cGMP) is responsible for various cellular functions including signal pathways and it acts as a mediator for nitric oxide (NO). In order to evaluate the anthelmintic efficacy of the plant-derived isoflavones, the crude peel extract of Flemingia vestita and pure genistein were tested with respect to the activity of nitric oxide synthase (NOS), NO efflux and the cGMP concentration in Rallietina echinobothrida, the cestode parasite of domestic fowl. For comparison, the parasites were also treated with genistein (the major isoflavone present in the crude peel extract), sodium nitroprusside (SNP), a known NO donor, and praziquantel (PZQ), the reference drug. At the time of onset of paralysis in the parasite, the activity of NOS showed a significant increase (35–46%) and a 2-fold increase of NO efflux into the incubation medium in the treated worms in comparison to the respective controls. The cGMP concentration in the parasite tissue increased by 46–84% in the treated test worms in comparison to the controls. The results show that the isoflavones, genistein in particular, from the crude peel extract of F. vestita influence the cGMP concentration in the parasite tissue, which plays a major role in the downstream signal pathways.

In the present study we have used antibodies to Leishmania major promastigote antigens which were eluted from a glutathione-agarose column (LmGbp) and could identify several parasite components among different Leishmania species by using immunoprecipitation and Western blot techniques. The results also showed that some of LmGbp are present among the molecules released into the culture medium. Moreover, immunofluorescence assays clearly demonstrated that LmGbp are expressed by intracellular amastigotes. The electron micrographs of thawed cryosections of L. major-infected cells revealed that the antigens were associated with the membrane of the phagocytic vacuole. Moreover, the Western blot technique allowed us to identify, using other Leishmania species extracts and anti-LmGbp antibodies, a major polypeptide of an apparent molecular mass of 66 kDa. Immunofluorescence studies suggested that the 66 kDa polypeptide is associated with intracytoplasmic vesicles. Cryosections of Leishmania promastigotes improved the fine structure preservation of the organelles and enabled a number of features to be seen, particularly the structures considered as vesicles, which appeared as a complex tubulo-vesicular structure resembling mammalian cell endosomes and Leishmania organelles previously named ‘megasomes’. Further studies using antibodies against the native 66 kDa protein will be needed to investigate the localization of the protein at the ultrastructural level and to follow its intracellular vesicular traffic.

The three trypanosomatid genome projects have employed common strategies which include: analysis of pulsed-field gel electrophoretic chromosomal karyotypes; physical mapping using big DNA (cosmid, pacmid P1, bacterial artificial chromosome, yeast artificial chromosome) libraries; partial cDNA sequence analysis to develop sets of expressed sequence tags (ESTs) for gene discovery and use as markers in physical mapping; genomic sequencing; dissemination of information through development of web-sites and ACeDB-based fully integrated databases; and establishment of functional genomics programmes to maximize useful application of genome data. Highlights of the projects to date have been the demonstration that, despite extensive chromosomal size polymorphisms for diploid homologues within Africa trypanosomes, T. cruzi or Leishmania, the physical linkage groups for markers on each chromosome are retained across all isolates/species studied within each group. For African trypanosomes, detailed analysis of chromosome 1 has demonstrated that repetitive sequences and the two retroposon-like elements RIME and INGI are localized to a defined region at one end of the chromosome, with the bulk of the central region of the chromosome containing genes coding for expressed proteins. Comparative mapping shows that, although subtelomeric changes account for a large proportion of the polymorphism in chromosome size in African trypanosomes, there are significant expansions and contractions in regions across the entire chromosome. The highlight of the genomic sequencing projects has been the demonstration of just 2 putative transcriptional units of chromosome 1 of Leishmania major, extending on opposite strands from a point in the central region of the chromosome. A similar observation made on 93·4 kb of contiguous sequence for T. cruzi chromosome 3 suggests the presence of promoter and regulatory elements at the junctions of large polycistronic transcriptional units. All data obtained from the genome projects are made available through the public domain, which has prompted changing philosophies in how we approach analysis of the biology of these organisms, and strategies that we can employ now in the search for new therapies and vaccines.

Amblyomma dissimile Koch is well known to science and previous accounts of its biology have already appeared. Newstead (1909) made some observations on its habits in Jamaica. Hooker, Bishopp, and Wood (1912) give an exact account of its life cycle worked out in confinement in the Southern United States of America. These authors do not refer to the occurrence of parthenogenesis in this species.

Schistosomiasis and malnutrition are often overlapped in poor communities, resulting in disproportionately high mortality rates. Currently, fragmented data make it difficult to define the relationship between diet and schistosomiasis. Thus, we systematically review the preclinical evidence on the impact of diet in Schistosoma mansoni infection. From a structured search, we recovered 27 original articles. All studies used mice and most of them investigated hypoproteic (70.37%), hyperlipidic (22.22%) or vitamin-deficient (7.41%) diets. Diets based on carbohydrate, zinc or milk supplementation were investigated at a reduced frequency (3.70% each). Hypoproteic diets attenuated parasitic load and granulomatous inflammation, but also reduced host resistance to S. mansoni infection, determining higher mortality rates. By stimulating steatohepatitis, parasitic load and granulomatous inflammation, hyperlipidic diets increase organ damage and mortality in infected animals. Although a high-sugar diet and vitamin restriction potentiate and zinc supplementation attenuates S. mansoni infection, the current evidence for these diets remains inconclusive. Analysis of methodological quality indicated that the current evidence is at high risk of bias due to incomplete characterization of the experimental design, diet composition and treatment protocols. From the bias analysis, we report methodological limitations that should be considered to avoid systematic reproduction of inconsistent and poorly reproducible experimental designs.

Leucine aminopeptidases (LAPs) are a group of metalloexopeptidases that catalyse the sequential removal of amino acids from the N-termini of polypeptides or proteins. They play an important role in regulating the balance between catabolism and anabolism in living cells. LAPs of apicomplexa parasitic protozoa have been intensively investigated due to their crucial roles in parasite biology as well as their potentials as drug targets. In this study, we identified an M17 leucine aminopeptidase of Cryptosporidium parvum (CpLAP) and characterized the biochemical properties of the recombinant protein. Multiple sequence alignment of the deduced amino acid sequence of CpLAP with those of other organisms revealed that typical amino acid residues essential for metal binding and active-site formation in M17 LAPs were well conserved in CpLAP. Recombinant CpLAP shared similar biochemical properties such as optimal pH, stability at neutral pHs, and metal-binding characteristics with other characterized LAPs. The enzyme showed a marked preference for Leu and its activity was effectively inhibited by bestatin. These results collectively suggest that CpLAP is a typical member of the M17 LAP family and may play an important role in free amino acid regulation in the parasite.

1. Filarial worms were found in the peritoneal cavity of a monkey (Macaca speciosa) from Bengal. They were identified as Dipetalonema digitatum (Chandler, 1929).

2. The microfilariae were unsheathed and showed a well-marked nocturnal periodicity in the blood.

3. No development of the microfilariae was detected in Aëdes aegypti, A. albopictus, Anopheles quadrimaculatus or An. stephensi, but only a few mosquitoes were observed.

4. Six female worms and one male were transplanted into the peritoneal cavity of a rhesus monkey (Macaca mulatta). Ten weeks later microfilariae were found in the blood of the monkey and they persisted for at least 16 weeks.

5. Filarial worms (Dipetalonema gracile) were discovered in the peritoneal cavity of a monkey (Cebus apella) from Brazil.

6. The microfilariae were unsheathed and were found in the blood. They showed no periodicity.

7. No development of the microfilariae was detected in Aëdes aegypti, A. albopictus, Anopheles maculipennis atroparvus or An. stephensi.

8. No pathological lesions due to either of these worms were detected in the monkeys.

Anthobothrium auriculatum (Rud.) is often referred to as ‘an insufficiently known species’. Southwell (1925) states that ‘all that is known about this doubtful species is contained in Rudolphi's brief description, which is quite insufficient to diagnose the species with, certainty’. Rudolphi (1819) first described it as Bothriocephalus auriculatus from Torpedo marmorata Risso; it is possible that this brief and inadequate description included several species. Leuckart (1820) described what has since been regarded as the same species under the name of Bothriocephalus flos from Carcharinus glaucus (L.), Bremser (1824) gave a brief account of Bothriocephalus auriculatus, and Zschokke (1888) gave a somewhat fuller account of Anthobothrium Auriculatum from Torpedo marmorata. As far as can be judged all these forms are synonymous. Diesing (1850) described what he thought to be Rudolphi's species, placing it in the genus Tetrabothrium; he obtained it from Torpedo marmorata Risso, Hexanchus griseus (Gm.), Carcharinus glaucus (L.), Squatina squatina (L.), and Raja calvata L. It has been pointed out by several writers that Diesing's Tetrabothrium auriculatum does not agree with Anthobothrium Auriculatum (Rud.), because, among other things, the genital pores in the former are anterior and in the latter posterior. Southwell (1925) states that Beauchamp is of the opinion that Tetrabothrium auriculatum Dies, is synonymous with Phyllobothrium gracile Wedl., an idea which is now generally accepted. Joyeux & Baer (1936) recorded Anthobothrium Auriculatum (Rud.) fairly frequently in a number of host fishes, namely, Mustelus mustelus (L.), Scyliorhinus caniculus (L.), Lamna cornubica (Gm.), Eugaleus galeus (L.), Squatina squatina (L.), Carcharias glaucus (L.), Torpedo marmorata Risso, and Raja clavata L. They, too, refer to the species as imperfectly known, and suggest that it might be synonymous with some other species of the same genus. In view of the lack of an adequate description of Anthobothrium Auriculatum it was felt that an account of its anatomy would render future identification of the species simpler and would settle the question as to whether or not it was synonymous with some other known species.

Rhabditiform first-stage larvae of Nippostrongylus muris are about 270–550μ long. The development of these larvae culminates in a moult, which occurred 36–48 hours after cultures were prepared. The first moult is preceded by an unusually early separation of the first cuticle, which is fine and unstriated, from the body tissue in the tail region and, later, by the formation of an underlying new cuticle, which is thicker and prominently striated.

Early second-stage rhabditiform larvae differ in certain morphological respects from first-stage larvae. Second-stage larvae are about 470–750μ long.

A second preparasitic ecdysis occurs and the infective larva is a true third-stage larva. This moult was the only one previously known to occur during the preparasitic development of N. muris.

The post-cervical cuticular inflation in N. muris is regarded, on the basis of a comparative study of the cuticle of this species and of Haemonchus contortus and other trichostrongyles, as resulting from the separation of the second and third layers of the cuticle. Yokogawa's view that Nippostrongylus muris has two cuticulae is rejected. N. muris has a single cuticula, apparently made up of four layers.

N. muris undergoes four complete moults and the development of this species does not differ in any essential respect from that reported for other strongyles.

Threshold density levels were investigated experimentally in rainbow trout, Oncorhynchus mykiss, for the acanthocephalan Pomphorhynchus laevis. Fifty small fish 120–150 mm long were infected with 50 cystacanths each every 4 weeks for 16 weeks, and samples of up to 10 fish examined at 1, 5, 9, 13 and 17 weeks after the original infection. The mean intestinal length was found to have increased significantly over this period, from a mean of 125 to 173 mm and the mean number of parasites recovered increased after each interval of 4 weeks, and significantly from 19·30 to 86·40 per fish over the 17 weeks. The distribution of the parasites in the alimentary tract of O. mykiss was unaltered, indicating that the favourable region for establishment had remained unchanged. The failure to detect any manifestations of competition is discussed, and the relevance of conventional approaches to experimental investigations of both intra- and interspecific competition in fish was queried, and contrasted to the situation in birds and mammals.

1. The percentage conversion of cercariae into schistosomula, when the former were penetrating human epidermal sheets, was found not to be significantly affected by the underlying media 1—5 (Table 1). The percentage conversion varied from 16·4% (in normal saline underlying skin) to 26.2 %. When distilled water was the underlying medium significantly fewer cercariae penetrated the sheets.

2. There was a statistically significant decrease in the percentage conversion of cercariae to schistosomula when sodium chloride final concentration 0·67 % was placed in the exposure tube with the cercariae (1·6 % P = < 0·02 when compared with La Ye medium); 0·43 % sodium chloride also significantly decreased penetration.

3. There was a statistically significant decrease in the percentage conversion of cercariae to schistosomula when the orientation of the human epidermis was reversed, i.e. the biologically inner surface was exposed to the cercariae (2.6 %, P = < 0.02, when compared with La Ye medium).

4. Schistosomula agglutinated in the presence of normal or immune human serum or horse serum. In human serum to which donor red blood cells had been added, many red cells adhered to the schistosomula. The number adhering was less in inactivated serum. The adhesion was specific for red cells, the effect not occurring with either yeast cells or silicic acid particles. The red cells were shed from the surface of the schistosomulum after 4—12 h.

I should like to thank the following: Dr S. A. Ibrahim, in whose laboratory this work was carried out; Dr S. Dawood of the Stack Laboratory, Khartoum for the use of his microscope; Mr T. R. Melrose and Mr J. R. Lauder for valuable discussions; the Medical Research Council, U.K., and the University of Khartoum for research grants. I am very grateful to the Pathology Department Faculty of Medicine, University of Khartoum, for preparing the sections of human epidermis.

A preliminary survey of parasites from Apodemus hebridensis, Mus musculus and Epimys norvegicus on the Isle of Lewis, Outer Hebrides, is described; also the fauna of House Mouse nests. Special discussion is given of the flea fauna, and it is shown that there is much overlapping in host relations. The original flea fauna of Apodemus on the outer islands of the British Isles is indicated.

The activity of 12 anticoccidial drugs against an embryo-adapted strain of Eimeria tenella has been investigated. After seven and five serial passages respectively, in the presence of drug, resistance was developed to methyl benzoquate and buquinolate. A strain of E. tenella made resistant by exposure to drugs in chickens was resistant to the same drugs when evaluated in infections of chick embryos. This relatively simple technique would appear to offer advantages over existing methods for the study of drug resistance.

The ability of Eimeria vermiformis, a coccidium which normally parasitizes the mouse, to develop in rats was investigated. The Rowett strain (Lac: RNU) rats were euthymic (rnu/+), treated or untreated with cortisone acetate, and athymic (rnu/rnu). E. vermiformis completed its development only in rnu/rnu rats, which passed small numbers of oocysts capable of sporulating and infecting C57BL/6 mice. In the rnu/+ rats, irrespective of cortisone treatment, development appeared to terminate with the completion of the asexual (schizogonic) stages since no gametocytes were recognized in the tissues and no oocysts were detected in the faeces. The findings are discussed with reference to the factors which govern host specificity.

The eggs and oncomiracidia of two species of the capsalid genus Encotyllabe are described. These parasites were identified tentatively as E. caballeroi Velasquez, 1977 and E. caranxi Lebedev, 1967. If these identifications are correct, then E. caballeroi is recorded from two new hosts, Gymnocranius audleyi and the nemipterid Scolopsis monogramma, and E. caranxi from a new host, Pseudocaranx dentex, and a new locality, Heron Island, Queensland, Australia. Encotyllabines have not previously been recorded from fishes of the family Nemipteridae. The eggs of the two parasites failed to hatch spontaneously and did not hatch when exposed to a variety of potential hatching stimuli, but the oncomiracidia within survived for many weeks. Oncomiracidia expelled from eggs by cover-slip pressure are unciliated and possess a saucer-shaped haptor like that of other capsalids with three pairs of median sclerites and 14 marginal hooklets. The paths of tendons associated with the accessory sclerites and the presence of haptoral loculi suggest that encotyllabines are related to the trochopodines. Observations on a single juvenile specimen of E. caballeroi show that the accessory sclerites and the tendons are lost early in development and that one pair of hamuli (probably the posterior pair) ceases to grow early in post-oncomiracidial life. The loculi persist a little longer but also disappear before full sexual maturity is reached.