Enzymes moonlight in a non-enzymatic capacity in a diverse variety of cellular processes. The discovery of these non-enzymatic functions is generally unexpected, and moonlighting enzymes are known in both prokaryotes and eukaryotes. Importantly, this unexpected multi-functionality indicates that caution might be needed on some occasions in interpreting phenotypes that result from the deletion or gene-silencing of some enzymes, including some of the best known enzymes from classic intermediary metabolism. Here, we provide an overview of enzyme moonlighting in parasitic protists. Unequivocal and putative examples of moonlighting are discussed, together with the possibility that the unusual biological characteristics of some parasites either limit opportunities for moonlighting to arise or perhaps contribute to the evolution of novel proteins with clear metabolic ancestry.

Leishmaniases is a tropical disease caused by protozoa of the genus Leishmania for which the current treatment is expensive, besides increasing reports of parasite resistance. This study investigated the anti-Leishmania amazonensis activity of the essential oil from Aloysia gratissima (AgEO) and guaiol, the major sesquiterpene constituent in the oil. Our results showed that AgEO killed promastigotes and intracellular amastigotes at an IC50 of 25 and 0·16 µg mL−1, respectively, while guaiol killed amastigotes at an IC50 of 0·01 µg mL−1. Both AgEO and guaiol were safe for macrophages up to 100 µg mL−1, as evaluated by the dehydrogenase activity, membrane integrity and phagocytic capacity. AgEO and guaiol did not induce nitrite oxide (NO) in resting macrophages and inhibited the production of NO in lipopolysaccharide-stimulated macrophages. The ultrastructural analysis suggested that AgEO and guaiol act directly on parasites, affecting promastigotes kinetoplast, mitochondrial matrix and plasma membrane. Together, these results pointed out that AgEO and guaiol could be promising candidates to develop anti-Leishmania drugs.

To understand how fisheries affect parasites, we conducted a meta-analysis of studies that contrasted parasite assemblages in fished and unfished areas. Parasite diversity was lower in hosts from fished areas. Larger hosts had a greater abundance of parasites, suggesting that fishing might reduce the abundance of parasites by selectively removing the largest, most heavily parasitized individuals. After controlling for size, the effect of fishing on parasite abundance varied according to whether the host was fished and the parasite's life cycle. Parasites of unfished hosts were more likely to increase in abundance in response to fishing than were parasites of fished hosts, possibly due to compensatory increases in the abundance of unfished hosts. While complex life cycle parasites tended to decline in abundance in response to fishing, directly transmitted parasites tended to increase. Among complex life cycle parasites, those with fished hosts tended to decline in abundance in response to fishing, while those with unfished hosts tended to increase. However, among directly transmitted parasites, responses did not differ between parasites with and without fished hosts. This work suggests that parasite assemblages are likely to change substantially in composition in increasingly fished ecosystems, and that parasite life history and fishing status of the host are important in predicting the response of individual parasite species or groups to fishing.

An account is given of the seasonal occurrence, maturation and population changes of Caryophyllaeus laticeps in its intermediate host Psammoryctes barbatus and in its definitive host Leuciscus leuciscus in the River Avon. Infective larvae were found in the tubificid in all months except August, but occurrence and maturation of C. laticeps in fish showed a clear seasonal periodicity. Infections were acquired between December and March, the parasite matured in April and May and disappeared by July. Maturation of C. laticeps appeared to be governed by changes in fish hormone levels. Changes in the parasite population in fish bore no relationship to the availability of infective larvae nor probably to the feeding behaviour of fish but were closely correlated with water temperature changes. The most important factor controlling the dynamics of the C. laticeps–dace system appears to be a temperature dependent rejection response to the parasites by dace, and it is suggested that a similar mechanism may operate to control the dynamics of other freshwater fish–tapeworm systems.

I should like to thank the Avon and Dorset River Authority, and in particular Mr A. S. Grater, for their help in capturing the fish and for their ready co-operation.

Plasmodium falciparum merozoites have an array of 2–3 subpellicular microtubules, designated f-MAST. We have previously shown that colchicine inhibits merozoite invasion of erythrocytes, indicating a microtubular involvement in this process. Colchicine inhibition of invasion was reduced by the Taxol®-stabilization of merozoite microtubules prior to colchicine exposure. Immunofluorescence assays showed that the number and length of f-MASTs were reduced in colchicine-treated merozoites, confirming that microtubules were the target of colchicine inhibition. The dinitroaniline drugs, trifluralin and pendimethalin, were shown by immunofluorescence to depolymerize the f-MAST and both drugs were inhibitory in invasion assays. These results demonstrate that the integrity of the f-MAST is important for successful invasion. Fluorescence imaging demonstrated the alignment of mitochondria to f-MAST, suggesting that mitochondrial transport might be perturbed in merozoites with disorganized f-MAST. Depolymerizing mt in late-stage schizonts did not affect the allocation of mitochondria to merozoites.

Paramphistomum daubneyi sp.nov., recovered from Bos taurus in Kenya, East Africa, is described and differentiated from the other species of the genus possessing a Microbothrium type of genital atrium.

Lymnaea truncatula Müller was infected experimentally with miracidia of P. daubneyi and the development in the snail host is briefly described.

The dynamics of infection of the fish host Poecilia latipinna by free-swimming tomites of the ciliate Ichthyophthirius multifiliis and the age-dependent survival of these infective stages are examined experimentally. Simple deterministic models are developed to aid the analysis of experimental results. Under defined laboratory conditions it is found that virtually all recently emerged infective stages successfully locate a host and that there appear to be no density-dependent constraints on parasite establishment on naive hosts. The overall reproductive success of the parasite is therefore shown to be determined by the proportion of infective stages encountering a host that are able to develop to form adult parasites. Variability between hosts in proportional establishment is postulated as the generating mechanism of the high observed heterogeneity in parasite burden/host. A model is described which predicts a simple relationship between mean parasite burden and variance in burden/host.

Monoclonal antibodies raised against antigens present in the excretions/secretions (E/S) of larval Trichinella spiralis, polyclonal antibodies raised against E/S and antisera from rabbits and pigs infected with T. spiralis were used in conjunction with immunocytochemical techniques to detect antigens in sections of muscle from mice that had been infected with T. spiralis for 15 or 30 days. The antibodies recognized epitopes in the stichocytes, on the surface of the cuticle, in the lumen of the oesophagus and in the lumen of the intestine of encysted larvae. Monoclonal antibodies 7C2C5 and 1H7 and the polyclonal antibodies recognized epitopes in the cavity occupied by the larva, in the cytoplasm of the nurse cell, and in the hypertrophic nuclei of the nurse cell, but did not recognize material in the smaller nuclei of the nurse cell, in the cyst wall or in the surrounding muscle. Monoclonals 3B2E6 and 1D11G8B2, which recognized epitopes in the stichocytes and on the surface of the cuticle of the larvae, gave negative results with the cytoplasm and nuclei of the nurse cell. A polyclonal antibody raised against Trichuris suis recognized epitopes in the muscle and hypodermis of encysted T. spiralis but gave negative results with material in the nurse cell and nurse cell nuclei. The possibility that the antigen detected in the cytoplasm and nuclei of the nurse cell is produced by the stichocytes of the nematode and that it is controlling genes of the altered muscle fibre, either directly or indirectly, is discussed.

Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) was evaluated for the rapid identification of ceratopogonid larvae. Optimal sample preparation as evaluated with laboratory-reared biting midges Culicoides nubeculosus was the homogenization of gut-less larvae in 10% formic acid, and analysis of 0·2 mg/ml crude protein homogenate mixed with SA matrix at a ratio of 1:1·5. Using 5 larvae each of 4 ceratopogonid species (C. nubeculosus, C. obsoletus, C. decor, and Dasyhelea sp.) and of 2 culicid species (Aedes aegypti, Ae. japonicus), biomarker mass sets between 27 and 33 masses were determined. In a validation study, 67 larvae belonging to the target species were correctly identified by automated database-based identification (91%) or manual full comparison (9%). Four specimens of non-target species did not yield identification. As anticipated for holometabolous insects, the biomarker mass sets of adults cannot be used for the identification of larvae, and vice versa, because they share only very few similar masses as shown for C. nubeculosus, C. obsoletus, and Ae. japonicus. Thus, protein profiling by MALDI-TOF as a quick, inexpensive and accurate alternative tool is applicable to identify insect larvae of vector species collected in the field.

A study to compare effects of mass, targeted and selective chemotherapy with levamisole (Ketrax) as an action for the control of Ascaris lumbricoides was carried out in three communities in rural Oyo State, Nigeria. Selective treatment was applied in one village by treating the most heavily infected 20% of the inhabitants, targeted treatment in the second village involved children aged 2–15 years, while mass treatment was offered to all inhabitants excluding infants under 1 year and pregnant women in the third village. Recommended doses of levamisole were given in the villages, as described above, at 3-monthly intervals during a period of 1 year. Prevalence and intensity (epg) of A. lumbricoides infection were determined immediately before and 3 months after the period of intervention using a modified Kato-Katz technique. In the selective treatment village, no significant differences were found between the pre- and post-treatment egg counts (mean(±S.D.) epg 6776±10791 versus 4259±10909 respectively) of A. lumbricoides in the total population. In the targeted treatment village, significant differences were recorded in pre- and post-treatment egg counts for the total population (9057 ± 15 797 versus 2579±6529) among the children alone (10935±20094 versus 992±3175) and among the untreated adults (7742±9782 versus 4561±8798). In the mass treatment village, significant differences in pre- and post-treatment egg count values were also recorded (11 907±17220 versus 1489±5165). The intensity of Trichuris trichiura and hookworm infections among the villagers before and after intervention were not observed to have changed significantly regardless of selective, targeted or mass treatment.

Infection with the avirulent piroplasm Babesia microti in mice is accompanied by a marked depression in the ability of the mice to mount an immune response to sheep red blood cells. The period of immunodepression begins 3 days after peak parasitaemia and is maximal 4 days later. There-after, there is a slow return to normal immune responsiveness, correlated with the gradual disappearance of the parasites from the blood. Both IgM and IgG responses are depressed. Cell-mediated responses as determined by contact sensitivity to oxazolone and allograft survival are apparently unaffected. Phagocytic activity as measured by carbon clearance tests is increased, and is correlated with the parasitaemia.

Genome projects for the parasitic helminths Brugia malayi (a representative filarial nematode) and Schistosoma were initiated in 1995 by the World Health Organization with the ultimate objectives of identifying new vaccine candidates and drug targets and of developing low resolution genome maps. Because no genetic maps are available, and very few genes have been characterized from either parasite group, the first goal of both Initiatives has been to catalogue new genes for future placement on chromosome and physical maps. These genes have been identified by the expressed sequence tag (EST) approach, utilising cDNA libraries constructed from diverse life cycle stages. To date, the Initiatives have deposited over 16000 Brugia ESTs and nearly 8000 Schistosoma ESTs in Genbank's dbEST database, corresponding to 6000 and over 3600 genes respectively (33% of Brugia's estimated gene compliment, 18–24% of that of Schistosoma). Large fragment, genomic libraries have been constructed in BAC and YAC vectors for studies of genomic organization and for physical and chromosome mapping, and public, hypertext genomic databases have been established to facilitate data access. We present a summary of progress within the helminth genome initiatives and give several examples of important gene discoveries and future applications of these data.

Trichomonas gallinae is an emerging pathogen in wild birds, linked to recent declines in finch (Fringillidae) populations across Europe. Globally, the main hosts for this parasite are species of Columbidae (doves and pigeons); here we carry out the first investigation into the presence and incidence of Trichomonas in four species of Columbidae in the UK, through live sampling of wild-caught birds and subsequent PCR. We report the first known UK cases of Trichomonas infection in 86% of European Turtle Doves Streptopelia turtur sampled, along with 86% of Eurasian Collared Doves Streptopelia decaocto, 47% of Woodpigeons Columba palumbus and 40% of Stock Doves Columba oenas. Birds were more likely to be infected if the farm provided supplementary food for gamebirds. We found three strains of T. gallinae and one strain clustering within the Trichomonas tenax clade, not previously associated with avian hosts in the UK. One T. gallinae strain was identical at the ITS/5.8S/ITS2 ribosomal region to that responsible for the finch trichomonosis epizootic. We highlight the importance of increasing our knowledge of the diversity and ecological implications of Trichomonas parasites in order further to understand the sub-clinical impacts of parasite infection.

A Neospora caninum 17–19 kDa antigenic protein fraction (p17) in one-dimensional polyacrylamide gel electrophoresis (SDS-PAGE) is the immunodominant antigen recognized by sera from bovines naturally infected by N. caninum. To identify the proteins making up the p17 fraction, we screened a new N. caninum tachyzoite cDNA library with an affinity-purified antibody against p17 (APA17). We isolated several cDNA clones with 100% sequence identity to the NcGRA7 gene. This previously described gene encodes a dense granule protein with an apparent molecular mass of 33 kDa. A second line of evidence emerged through a combined proteomic approach associating two-dimensional PAGE (2D-PAGE) to Western blotting and to mass spectrometry to characterize the p17 fraction. Two acidic immunodominant but minority protein spots were recognized by APA17 and by bovine sera. These antigens of 17 and 33 kDa are respectively composed of 4 and 2 isoforms. Furthermore, p17 isolation by 2D-PAGE and peptide sequencing by tandem mass spectrometry yielded a partial sequence of 17 amino acids, which allowed the putative amino terminal region of the NcGRA7 protein to be identified unambiguously.The NcGRA7 protein, without the putative signal peptide at the NH2-terminus, was cloned and expressed in Escherichia coli and when the purified recombinant protein (rNcGRA7) was analysed by SDS-PAGE and mass spectrometry, 2 bands of 24 and 33 kDa were resolved and identified as NcGRA7. These results demonstrate that the immunodominant 17 kDa antigen of N. caninum is encoded by the NcGRA7 gene.

Some unique features of monogenean biology have emerged from studies on 2 polystomatids which infect spadefoot toads in Arizona, USA: Pseudodiplorchis americanus in Scaphiopus couchii and Neodiplorchis scaphiopodis in S. multiplicatus and S. bombifrons. Transmission is confined to 1–3 nights each summer when the desert-adapted toads enter water to spawn. Encapsulated larvae complete development in utero and hatch within seconds of deposition; their body length (up to 600 μm) is 2–4 times greater than that of most other oncomiracidia, and their swimming life (over 48 h at 25–27 °C) is twice that usual amongst monogeneans. The ciliated oncomiracidia invade the nostrils, a target usually above the water surface and requiring migration over the exposed skin; remarkably they tolerate drying for up to 1 h (at 32 °C, 45% rel. hum.). The larvae migrate via the buccal cavity and glottis to the lungs where juvenile development occurs until early autumn. Migration from the lungs to the urinary bladder (by an as yet undetermined route) is followed by maturation and reproduction during host hibernation, and developing embryos accumulate in preparation for a period of transmission more restricted than that of any other monogenean. No other monogenean is known to exploit the lungs nor to inhabit, successively, anterior and posterior sites of the same adult host individual.

The protective potential of killed Leishmania major (ALM) along with BCG was evaluated against L. donovani in Indian langur monkeys in single and triple dose schedules. A delayed protection was observed in monkeys after a single dose schedule of ALM (3 mg)+BCG (3 mg) given intradermally 2 months before intravenous challenge with L. donovani. Triple dose schedule each of 1 mg ALM+1 mg BCG was more effective. The status remained unchanged until the end of the experiment (approximately 8 months). The study indicates that a combination of ALM+BCG may be a good candidate vaccine for exploiting against human Kala-azar.

Roach (n = 81) caught on 23 May, 1992 from oligotrophic, unpolluted Lake Peurunka were kept in cages over a 2-week period before moving half of the fish to nearby Lake Vatia, which is influenced by pulp mill effluents. Before moving the fish gill parasites were examined from 9 fish; 5 Dactylogyrus species, Gyrodactylus sp. and Paradiplozoon homoion were found, the main components of the infracommunities being dactylogyrids. Afterwards, 5 fish from each lake were studied weekly between 1 July and 17 August. Metazoan parasites were recorded from gill arches divided into 4 sections along the dorso-ventral axis. D. crucifer, D. nanus, D. micracanthus and D. suecicus occurred in both lakes throughout the study. Gyrodactylus sp., Ergasilus briani and P. homoion occurred in low numbers in both lakes. Differences between the lakes were seen in the prevalence of D. micracanthus which was higher in Lake Vatia and significantly increased abundances of D. crucifer, D. nanus and D. micracanthus in Lake Vatia. Abundances of other Dactylogyrus species remained, on average, at the same level in both lakes. No change during the experiment was recorded in the location of the two most common species, D. crucifer and D. nanus, on the host gills in either of the lakes, both species favouring the 2nd and 3rd gill arches and especially the inner parts of the gills. The apparent lack of competition between the 2 most common Dactylogyrus species indicates that no limitation of resources on roach gills occurred. This was also confirmed by the increased overlapping indices with increasing abundances between the two most common species in Lake Vatia.

Female (Fig. 1): Colour: scutum, basis capituli, coxae, distal parts of femur and proximal portions of tarsi and intervening articles are blackish brown, the remaining hard parts shading to yellowish-brown. (Dorsal aspect) Body (partly gorged) short and broad. Scutum about as long as broad, 0·87 × 0·85 mm., very slightly emarginated, with rounded scapular angles, antero-lateral borders almost straight, lateral angles situated at the anterior third of the length, posterior border rounded; cervical grooves deep, far apart, but slightly concave outwardly and slightly divergent, fading near the postero-lateral borders; surface glossy, somewhat rugose; punctations few, mostly fine. Capitulum with base roughly equilateral-triangular, short pointed cornua and sinuous dorsal ridge; porose areas not depressed, subcircular, near ridge, the interval less than their width and hollowed. Palps slender, article 1 small, articles 1–2 almost fused, broadest at the distal third of article 3 which is rounded distally; (Ventral aspect) hypostome club-shaped, 4|4 merging to 3|3 and 2|2 posteriorly where the median unarmed ridge broadens, teeth sharp, 12 per external file; basis capituli constricted where the short pointed recurved auriculae arise, posterior margin straight with rounded angles. Venter: vulva between coxae II; anal grooves form a small closed ring situate near the posterior border; spiracle ovoid, macula central. Legs slender; coxa I with short internal and stout external spur; stout external spurs on coxae II–IV progressively decreasing in size; trochanters with slight spurs; tarsus 4 tapering gradually, the distal pseudo-article about thrice as long as the basal; pads large but shorter than the claws.

An earlier paper (May, 1977) developed a theoretical framework for exploring the consequences of dioecy for the population dynamics of schistosomes, assuming an unbiased sex ratio. This paper extends the analysis to biased sex ratios, as have been reported in practice. We consider the relationships of the mean number and distribution of worms among hosts, the sex ratio, and the mating system (monogamous or polygamous) to: (i) the female mating probability, Φ the prevalence of mated female worms. Ω: and (iii) the mean number of mated female worms per host, ξ. Among other results, we show how high values of Φ are associated with male-biased sex ratios and polygamous mating; that Ω is independent of the mating system and is relatively unaffected by the sex ratio; and that ξ is maximal for unbiased sex ratios given monogamous mating, and for female-biased sex ratios if mating is polygamous. These results, together with the confounding effects of the mean number and distribution of worms, are described in detail in the main body of the paper.