Genetic analysis of Trypanosoma spp. depends on the detection of variation between strains. We have used the amplified fragment length polymorphism (AFLP) technique to develop a convenient and reliable method for genetic characterization of Trypanosome (sub)species. AFLP accesses multiple independent sites within the genome and would allow a better definition of the relatedness of different Trypanosome (sub)species. Nine isolates (3 from each T. brucei subspecies) were tested with 40 AFLP primer combinations to identify the most appropriate pairs of restriction endonucleases and selective primers. Primers based on the recognition sequences of EcoRI and BglII were chosen and used to analyse 31 T. brucei isolates. Similarity levels calculated with the Pearson correlation coefficient ranged from 15 to 98%, and clusters were determined using the unweighted pair-group method using arithmetic averages (UPGMA). At the intraspecific level, AFLP fingerprints were grouped by numerical analysis in 2 main clusters, allowing a clear separation of T. b. gambiense (cluster I) from T. b. brucei and T. b. rhodesiense isolates (cluster II). Interspecies evaluation of this customized approach produced heterogeneous AFLP patterns, with unique genetic markers, except for T. evansi and T. equiperdum, which showed identical patterns and clustered together.

Cryptosporidia are important protozoan parasites of vertebrates, and a number of species and genotypes, with different host ranges, have been described. In this study a protocol was established for the detection and the genetic characterization of Cryptosporidium spp. isolated from various types of surface waters (rivers, creeks, lakes, sewage plant in- and outlets and swimming pools) from the area between Zurich (Switzerland) and Munich (Germany). Cryptosporidium oocysts were isolated by continuous-flow-centrifugation and immunomagnetic separation (IMS). A novel nested PCR combined with direct sequencing of the amplicon which spans a variable region of the 18S rRNA allowed characterization of species and genotypes. Cryptosporidium spp. were detected in 23 of the 68 water samples investigated. Almost half of these isolates represent species and genotypes known to be pathogenic to man, namely C. parvum ‘bovine genotype’ (from 6 samples) and C. parvum ‘human genotype’ (4). Furthermore, we identified C. muris ‘genotype A’ (3), C. muris ‘genotype B’ (6), C. baileyi (1) as well as 3 novel Cryptosporidium genotypes. Our results confirm the ubiquitous presence of Cryptosporidium oocysts in surface waters. The detection of a variety of species and genotypes stresses the importance that molecular characterization is indispensable before drawing conclusions of medical or epidemiological significance.

A new Myxozoa species causing enteritis and death in cultured turbot, Scophthalmus maximus, is described at light and electron microscope levels. In addition, small subunit ribosomal RNA gene sequences (SSU rDNA) from the new species and from similar myxozoans were obtained and used for phylogenetic inference, as complementary criteria to resolve its taxonomic classification. The new parasite is closely related to Myxidium leei, another enteric histozoic species from marine fish. However, the ascription of M. leei to the genus Myxidium was based on weak morphological evidence and is not supported by our rDNA data analysis. A close relationship with Zschokkella, the other morphologically related myxozoan genus is also not supported. The combined morphological and molecular study results in the establishment of the new genus Enteromyxum to accommodate the new species E. scophthalmi, and the former M. leei, which is transferred to the new genus as Enteromyxum leei (Diamant, Lom & Dyková 1994) n. comb. This genus of marine, histozoic and enteric myxozoans includes significant parasite species for marine finfish culture.

Glugoides intestinalis, Microsporidium sp., Ordospora colligata, Gurleya vavrai, Larssonia obtusa and Flabelliforma magnivora are microsporidian parasites of planctonic freshwater crustaceans Daphnia spp. We performed a phylogenetic analysis of the small subunit ribosomal DNA which revealed their positions as polyphyletic. G. intestinalis, Microsporidium sp. and O. colligata, which are horizontally transmitted gut parasites with small spores and low virulence, group with different lineages. G. intestinalis is related to 2 microsporidia infecting lepidopterans and to Vittaforma corneae, which has been described as a human pathogen. It is thought that V. corneae may have an invertebrate as its natural host. Microsporidium sp. is a relative of the genera Enterocytozoon and Nucleospora, pathogens of man and fish respectively. O. colligata is the first species found to be closely related to the genus Encephalitozoon, which is comprised of 3 species that are parasites of homeothermic vertebrates. G. vavrai and L. obtusa are sister taxa that branch close to the Amblyosporidae, the only microsporidia with known intermediate hosts. This finding supports the presumption of secondary hosts for G. vavrai and L. obtusa, as it has not been possible to maintain these species in Daphnia in the laboratory. F. magnivora roots deep at the base of the phylum microsporidia with no close relative found so far.

Pentastomids are arthropod-like parasites which inhabit the respiratory tract of tetrapods and, despite being haematophagous, cause little or no visible pathology. Nymphs (or larvae), belonging to the advanced genus Porocephalus, encyst in the tissues of rodent intermediate hosts and migrate from this site to the lung following ingestion of the intermediate host. During migration, several moults occur and instars encounter a variety of tissue barriers and environmental cues. It was therefore relevant to define the proteins and proteinases released by the different instars during this migration as they are likely to be essential for tissue penetration, feeding and immune evasion. In vitro released proteins (IVRP), commonly termed ES, were defined on the basis of molecular size and immune recognition by naturally infected rodent intermediate hosts. In addition, proteinases present in IVRP were characterized using gelatin-substrate gels and protein degradation assays. These studies showed that the protein profile is subtly different when IVRP from different instars is compared. In addition, IVRP from each instar contained metallo-proteinases with proteolysis at 48 kDa dominating in all stages. However, other higher molecular weight activities were, to an extent, released in a stage-specific manner. These proteinases degraded haemoglobin and fibrinogen as well as structural proteins such as collagen and fibronectin, suggesting roles in bloodmeal digestion and tissue penetration. Immunoglobulin digestion was not demonstrated.

Numerous hypotheses have been postulated to explain the rapidly changing parasitological situation in Loum, Cameroon as a result of the interaction between Schistosoma haematobium and S. intercalatum. The aim of this study is to test the various hypotheses using a simple mathematical model, incorporating equal and unequal sex ratios of adult schistosomes, recombinations, and levels of compatibility with the intermediate molluscan hosts, B. forskalii and B. truncatus. The model assuming an equal sex ratio does not fit with the existing field data in that it predicts a continued presence of S. intercalatum, S. haematobium and the hybrids. The model assuming a sex bias in favour of males, which reflects the situation usually observed in schistosome populations, predicts the loss S. intercalatum which indeed concurs with the most recent data.

The effect of platyhelminth FaRPs and selected classical neurotransmitters on the motility of intact Mesocestoides corti (syn. M. vogae) tetrathyridial larvae was studied in vitro using a micromotility meter. The effects of the test substances were temperature dependent and these were examined at 4, 23, 30 and 36 °C. At 36 °C all test substances had concentration-dependent excitatory effects, with thresholds for activity of: 100 nM (GNFFRFamide), 10 μM (YIRFamide), 30 μM (GYIRFamide), 100 nM (serotonin) and 100 μM (acetylcholine). At this temperature significant elevation of motility indices (MI) was recorded within 5 min of the addition of peptide or serotonin. The effect of acetylcholine was slower in onset and appeared 15–20 min post-addition. At 30 °C larval motility diminished more rapidly than that recorded at 36 °C, following the addition of 1 mM of each test substance. At 23 °C only serotonin (1 mM) significantly increased the MI, all other test substances having no apparent effect. Larval movement was completely arrested at 4 °C. The results demonstrate for the first time excitatory effects of platyhelminth neuropeptides and acetylcholine on muscle systems in cestode larvae. The fact that the only known cestode FaRP, GNFFRFamide, was more potent than any of the turbellarian FaRPs tested, suggests structural conservation of FaRPs and FaRP receptors within the cestodes.

Life-history attributes of the capsalid monogenean Benedenia lutjani, a parasite of Lutjanus carponotatus from the Great Barrier Reef, Queensland, Australia, were investigated from experimental infections. Oncomiracidia of B. lutjani invaded and attached at any site on the fish, but more commonly invaded body surfaces. Immature specimens then migrated to the pelvic fins. Development of the reproductive organs of B. lutjani corresponded with migratory movements on the host. Parasite aggregation on the pelvic fins coincided with the development of functional male reproductive organs and some protandrous worms that possessed a vagina appeared to be inseminated. Migration to, and aggregation on, the branchiostegal membranes (membranous folds posterior to the opercula) coincided with the onset of sexual maturity and commencement of egg production by parasites. The rate of parasite development and the timing of migratory events on the host were influenced by water temperature. All specimens of B. lutjani reached sexual maturity between 12 and 14 days p.i. at 24 °C and between 8 and 10 days p.i. at 27 °C. Anterior hamuli grew continually during a 16-day experiment at 27 °C and 25-day experiment at 23 °C and their length appeared to provide a suitable index to estimate parasite age. The possible adaptive significance of the migratory behaviour, site-specificity and its link with changes in parasite development are discussed.

The aim of the present study was to compare the helminth infra and component communities of wild and stocked brown trout in Lough Feeagh, in the west of Ireland, and also to examine the establishment and development of helminth communities in stocked brown trout. Fish were sampled in May, August and November 1997 and 1998 and an additional sample of wild brown trout was examined in April 1997. In total 217 wild trout and 122 stocked trout were examined. The acanthocephalans Acanthocephalus clavula and Pomphorhynchus laevis were the first parasite species to infect stocked trout in May 1997. In May 1998 both acanthocephalan species along with the trout specialists Eubothrium crassum and Crepidostomum farionis were the first to infect trout. Mean species richness values for stocked trout increased from May to November, in 1997 and 1998. For wild trout, mean species richness values increased from April to November, in 1997 and decreased from May to November in 1998. The parasite communities of wild trout were richer than those of stocked trout in May of both years. In August the parasite communities recorded for wild and stocked trout were similar in terms of the number of species present but differed in terms of structure, and in November the parasite communities of stocked trout were richer than those of wild trout.

Dietary texture has been reported to influence parasite establishment and survival, but to what degree this relationship is modified by either the type or quantity of dietary fibre is unknown. Using a 2×4 factorial design, we explored the relationship between fibre type (soluble = pectin vs insoluble = cellulose) and fibre quantity (0, 5, 10 and 20% by dry weight) on parasitic outcomes in BALB/c mice infected with 100 Heligmosomoides polygyrus (Nematoda) larvae. Pectin, but not cellulose, exerted a significant effect on parasite egg production. Following in vitro culture of female worms, increasing levels of dietary pectin were associated with increasing release of eggs. Yet this pattern was not observed in vivo, where per capita egg production peaked at the 10% pectin concentration, but was very low in mice fed 20% pectin. Parasite establishment was elevated in mice fed 20% pectin, but was unaffected by cellulose concentration. Neither type nor quantity of fibre affected H. polygyrus survival or spatial distribution along the gastrointestinal tract. To what degree differences in parasite establishment and reproduction could be attributed to the marked effects of pectin on gut morphology (increased intestinal length, villus length, mucosa thickness and villus/crypt ratio) requires further exploration. Our data indicate that cellulose is preferable to pectin as the source of fibre for experimental diets as cellulose did not affect H. polygyrus establishment, reproduction or survival during a 4-week primary infection.

We have developed an index based on macroscopic criteria to easily assess the health state of the eel swimbladder as a result of infection by the nematode Anguillicola crassus. In the sampling area (brackish lagoons of the French Mediterranean coast), 92% of the host sample (1251 eels covering all size classes) showed pathological signs of infection. The general trend was for increasing damage as eel size increased, thus suggesting accumulation of pathological effects. We also revealed a non-linear relationship between the swimbladder index and the abundance of living worms. In particular, we showed that severely damaged swimbladders harboured very few living nematodes. We argue that the swimbladder degenerative index more closely reflects the parasite pressure than does classic parasite count. We found seasonal variation in the swimbladder index, with maximum damage occurring in July and thereafter a trend for healthy individuals. We discuss the possibility that the seasonal decrease in the swimbladder index could reflect the death of the more severely affected individuals during the warmest months.

The outcome of a parasite infection is the result of the interaction between the host and the parasite. In the system we studied, there are 3 critical stages for the outcome of infection of the (intermediate) host, the copepod Macrocyclops albidus, with the cestode Schistocephalus solidus. During the establishment phase of the parasite, the host may firstly avoid ingesting the parasite and, secondly, may prevent the parasite from entering the body cavity and, thirdly, during the growth phase of the parasite, the host's immune system may eliminate the parasite from the body cavity. We were able to study the growth phase separately from the establishment phase. The establishment phase was influenced by characteristics of the host as well as characteristics of the parasites. Small copepods and males performed poorly; they were more often infected and had a lower survival. Parasites from different sib-groups differed in infectivity. During the growth phase some disappearance of parasites was observed. However, this could not be related to any of the studied characteristics of the host, and the sib-groups of parasites did not seem to differ in their likelihood to disappear. Instead, we suggest that disappearance of parasites, once they have entered the body cavity, may be due to intrinsic mortality of the parasites, independent of the host or the sib-group that the parasites belong to. This indicates that the crucial interactions between host and parasite determining the outcome of infection takes place in the short time-period between ingestion and penetration of the gut-wall.