East Coast fever (ECF) is a fatal disease of cattle caused by the protozoan parasite Theileria parva. The development of a subunit vaccine, based on the sporozoite-specific surface antigen p67, has been hampered by difficulties in achieving high-level expression of recombinant p67 in a near-authentic form. Therefore two sets of recombinant baculovirus vectors were constructed. The first set, encoding various regions of p67, produced low levels of the corresponding p67 domains in High Five™ cells, despite the presence of large amounts of p67 RNA. The second, consisting of p67 domains fused to the carboxy-terminus of GFP expressed significantly higher levels of p67 protein. The GFP[ratio ]p67 fusion proteins were recognized by a sporozoite-neutralizing monoclonal antibody (TpM12) raised against native p67 whereas non-fused full length p67 expressed in insect cells was not recognized. GFP-tagging therefore, appeared to enhance the stability of p67 and to conserve its folding. The high-level expression of p67 domains in a more authentic form is an important step towards the development of an effective subunit vaccine against ECF.

Polistes atrimandibularis is a species of obligate social wasp parasite, which introduces into nests of the host species P. biglumis, where it rears its own brood relying on the workers of the host species. Wasps of the host species discriminate between nestmates and non-nestmates by means of their epicuticular hydrocarbons. To overcome the host recognition systems, parasites have to modify their epicuticular recognition cues. Compared to individuals of the host species, parasites have 3–4 times less epicuticular hydrocarbons, although they share with their hosts the habitat and even the nests. We hypothesize that a dilution of the recognition cues in social parasites could have a facilitating role in entering host nests, in integrating within their host colony and in sneaking into secondary colonies to steal larvae and pupae.

Due to shared characteristics with snail haemocytes, the Biomphalaria glabrata embryonic (Bge) cell line has been used as a model in vitro system for the study of snail–trematode interactions. In this study, Bge cells were used to characterize the adherence of snail host cells to schistosome primary sporocysts, and to test the effect of carbohydrates as inhibitors of this behaviour. Bge cells bound to the surface of >90% of Schistosoma mansoni sporocysts and, based on a semi-quantitative cell adhesion scale of 1–4, exhibited a cell adhesion index (CAI) of 2·45. This cellular adhesion was significantly inhibited in the presence of selected carbohydrate-containing substances. Fucoidan was the most potent inhibitor, reducing Bge cell-binding prevalence to approximately 50% and the CAI to 1·6. Other inhibitory compounds included mannose-6-phosphate, heparin, dextran sulfate, and various forms of the polysaccharide carrageenan. Fluoresceinated-fucoidan was found to attach to Bge cells confirming their ability to associate with sugar moieties. These results were further supported by the specific binding of surface biotinylated Bge cell proteins to sporocyst tegumental glycoproteins ranging from 40 to 120 kDa. N-linked tegumental carbohydrates appeared to represent ligands for Bge cell proteins since N-glycosidase treatment of blotted tegumental glycoproteins completely abolished biotinylated Bge protein binding. We hypothesize that the involvement of lectins as potential host cellular receptors in snail cell–sporocyst interactions, and suggest that negatively charged (mainly sulfated) carbohydrate moieties may represent the schistosome surface ligand(s).

Excretion of metabolic wastes as well as xenobiotics is a major concern of all living organisms, and the Platyhelminthes including Schistosoma mansoni possess the protonephridial excretory system for their survival. Except for some ultrastructural and biochemical information, little is known about the protonephridium of platyhelminths due to a lack of established techniques for exploring the excretory activity. This study describes a new technique to assess the excretory activity of S. mansoni by use of the fluorescent marker resorufin, which is a potential substrate of the drug efflux pump, P-glycoprotein. After simple diffusion into the schistosome body, fluorescent resorufin was concentrated in the excretory tubules by an energy-dependent mechanism and excreted via the nephridiopore. The present technique of labelling functionally the excretory system was applicable to adult worms, but not schistosomula or cercariae. A variety of modulators known to interfere with mammalian P-glycoprotein function perturbed resorufin excretion from male adult schistosomes, including cyclosporin A, Ro11-2933, verapamil, or nifedipine. This technique of labelling the excretory system with fluorescent resorufin has enabled us to study aspects of the physiological function, hitherto unknown, of the protonephridial system of S. mansoni.

The study investigated whether the susceptibility of calves to an early Schistosoma mattheei infection may be modified by intake of colostrum from infected cows. Twelve calves born to non-infected mothers were randomly divided into 2 groups of 6. The animals from group 1 were fed colostrum originating from a pool collected from non-infected cows, the calves from group 2 received colostrum from a pool collected from cows infected with S. mattheei. One month after birth all calves were infected by exposure to 1000 cercariae of a local strain of S. mattheei, and perfused 12 weeks later to determine the worm- and tissue egg counts. IgGH+L, IgG1, IgG2 and IgA levels against soluble adult worm antigen preparation of S. bovis (SWAP bovis) were analysed in both colostrum pools and in the serum from the calves collected during the study before and after receiving colostrum, then on days 7, 30, 73 and 122. Faecal egg counts were determined from day 73 onwards. The IgGH+L, IgG1 and IgA levels of the positive colostrum pool were higher than those of the negative pool. Calves of group 2 showed significantly higher levels of IgGH+L and IgG1 until day 73, to reach equal levels at necropsy. Calves of group 2 showed significant reductions of 42, 28 and 42% in total worm counts, female worm counts, and tissue egg counts, respectively, and a reduction of 25% in cumulative faecal egg counts. These findings indicate that there was a significant impact of colostrum on the parasitological and serological course of early S. mattheei infections.

The standard assay for onchocerciasis diagnosis is microscopical detection of microfilariae in skin snips. Skin snipping is painful, requires appropriate sterilization of equipment, and may fail to diagnose light infections. Two alternatives are a polymerase chain reaction (PCR) test which detects parasite DNA in pieces or scrapings of skin and a test based on allergic reactions to topical application of diethylcarbamazine (DEC). We compared these 2 diagnostics with standard skin snip microscopy in 313 individuals from 2 villages in Guinea, with low prevalence after over 10 years of control by the Onchocerciasis Control Programme. Lower and upper bounds on sensitivities and specificities of these 3 tests were estimated. In addition, these parameters were estimated using 5 different statistical models. Where prevalence was low, PCR and the DEC patch test appeared to be more sensitive than skin snipping which has low sensitivity. As the DEC test is non-invasive, simple and cheap, it may provide a good alternative to skin snipping alone for surveillance in low prevalence areas.

Vertical migration by infective larvae (L3) of 3 species of nematodes was investigated. Upright truncated agarose cones were used to test upward migration, and comparable truncated cone-shaped agarose hollows were used to test downward migration. Flat agarose plates were control surfaces. When placed at the bases of upright cones, 74% of Ancylostoma caninum L3 migrated up, whereas only 16·5% migrated down the indented cones; this latter value was not significantly different from larval migration on flat plates. Strongyloides stercoralis L3 also migrated upward in significant numbers (80%). These larvae also failed to migrate downward under normal conditions. However, when the bottoms of the indented cones were 3–5 °C warmer than the tops, 75·5% of S. stercoralis L3 migrated down. In contrast, Haemonchus contortus L3 showed no tendency to crawl up or down cones, when compared with normal crawling behaviour on flat plates. Thus, L3 of A. caninum and S. stercoralis exhibited negative geotaxis, crawling against the pull of gravity, while H. contortus did not. The biology of these parasites may explain these behavioural differences.

Low doses of the acetylcholinesterase-inhibiting carbamate nematicides disrupt chemoreception in plant-parasitic nematodes. Fluorescein isothiocyanate (FITC)/dextran conjugates up to 12 kDa are taken up from the external medium by certain chemosensory neurons in Caenorhabditis elegans. Similar chemoreceptive neurons of the non-feeding infective stage of Heterodera glycines (soybean cyst nematode) fill with FITC and the nuclei of their cell bodies selectively stain with bisbenzimide. The widely used nematicide aldicarb disrupts the chemoreceptive response of H. glycines with 50% inhibition at very low concentrations (ca 1 pM), some 10−6-fold lower than required to affect locomotion. Similarly, the anthelmintic levamisole had this effect at 1 nM. Peptides selected as mimetics of aldicarb and levamisole also disrupt chemoreception in H. glycines and Globodera pallida at 10−3-fold or lower concentration than required to inhibit locomotion. We propose an uptake pathway for aldicarb, levamisole, peptide mimetics and other soluble molecules by retrograde transport along dendrites of chemoreceptive neurons to the cell bodies and synapses where they act. This may prove to be a general mechanism for the low-dose effects of some nematicides and anthelmintics.

Since isolates of Hymenolepis nana infecting humans and rodents are morphologically indistinguishable, the only way they can be reliably identified is by comparing the parasite in each host using molecular tools. In the current study, isolates of H. nana from rodent and human hosts from a broad geographical range were sequenced at the ribosomal first internal transcribed spacer (ITS1), the mitochondrial cytochrome c oxidase subunit 1 (C01) gene and the nuclear paramyosin gene loci.Nucleotide sequence data published here have been submitted to GenBank™ and are available under accession numbers AF461124 and AF461125 (18S–28S); AY121842 and AY121843 (cytochrome c oxidase 1); AY1844 and AY121845 (paramyosin). Twenty-three isolates of H. nana were sequenced at the ITS1 locus and this confirmed the existence of spacers which, although similar in length (approximately 646 bp), differed in their primary sequences which led to the separation of the isolates into 2 clusters when analysed phylogenetically. This sequence variation was not, however, related to the host of origin of the isolate, thus was not a marker of genetic distinction between H. nana from rodents and humans. Sequencing of a 444 bp fragment of the mitochondrial cytochrome c oxidase 1 gene (C01) in 9 isolates of H. nana from rodents and 6 from humans identified a phylogenetically supported genetic divergence of approximately 5% between some mouse and human isolates. This suggests that H. nana is a species complex, or ‘cryptic’ species (=morphologically identical yet genetically distinct). A small segment of the nuclear gene, paramyosin, (625 bp or 840 bp) was sequenced in 4 mouse and 3 human isolates of H. nana. However, this gene did not provide the level of heterogeneity required to distinguish between isolates from rodent and human hosts. From the results obtained from faster evolving genes, and the epidemiological evidence, we believe that the life-cycle of H. nana that exists in the north-west of Western Australia is likely to involve mainly ‘human to human’ transmission.