Riboprinting is one of several molecular methods that can generate comparative data independently of the complexity of the organism's morphology. Restriction fragment length polymorphism (RFLP) profiles derived from digestion of polymerase chain reaction (PCR) products of the ribosomal 18S from Leishmania spp. yields a typical ‘riboprint’ profile that can vary intraspecifically. A selection of 76 stocks of L. major and L. tropica, isolated from patients with cutaneous leishmaniasis, was analysed by riboprinting to assess divergence within and between species. L. major and L. tropica could be easily differentiated from each other. Analysis of PCR–RFLP profiles indicated that stocks of Leishmania spp. could be broadly partitioned into 2 species corresponding to L. major and L. tropica. To test if ribosomal 18S sequences were homogeneous within each species, several isolates of each of the Leishmania spp. were digested. Interpretation of the riboprint profiles of the 18S independently amplified by PCR, there would appear to be one restriction pattern present within each Leishmania spp. Homogeneity within copies of the ribosomal 18S within a single genome has, therefore, been demonstrated. The species designation established by riboprinting results were in agreement with the zymodeme analysis of the same isolates. The restriction patterns produced were simple, reproducible and easy to interpret.

The northern biotype of Echinococcus granulosus occurs in North America and northern Eurasia in life-cycles involving cervids. Previously, cervid isolates of E. granulosus from North America have been characterized using molecular genetic techniques as the G8 genotype. In this study, 5 isolates of E. granulosus were collected from 4 reindeer and 1 moose in north-eastern Finland. DNA sequences within regions of mitochondrial cytochrome c oxidase I (COI) and NADH dehydrogenase I (NDI) genes and the internal transcribed spacer 1 (ITS-1) fragment of the ribosomal DNA were analysed. The mitochondrial nucleotide sequences were identical in all isolates, but high sequence variation was found in the ITS-1 region. Mitochondrial and nuclear sequences of the Finnish cervid E. granulosus and the camel strain (G6) of E. granulosus resembled closely each other. According to phylogenetic analyses, the Finnish isolates have close relationships also with the pig (G7) and cattle (G5) strains. Although some similarities were found with the previously published North American cervid strain (G8), particularly in the NDI sequence and some of the ITS-1 clones, the Finnish E. granulosus form represents a distinct, previously undescribed genotype of E. granulosus. The novel genotype is hereby named as the Fennoscandian cervid strain (G10).

The transmission dynamics of the cercariae of Diplostomum spathaceum were investigated under laboratory conditions using cercariae collected from naturally infected Lymnaea stagnalis. Cercariae were kept in a constant temperature of 20 °C and the survival and infectivity to naïve young rainbow trout recorded at 3-h intervals until few cercariae were alive. Mortality initially remained constant but increased rapidly after 20 h. While a model of constant mortality fitted the survival data, an age-dependent model provided a better fit and implied that cercariae tended to carry similar quantities of resources and once these were exhausted the cercariae died. Cercarial infectivity also showed an age-dependent pattern although infectivity tended (P=0·09) to increase with age over the first 6 h of life and then fall. The per capita transmission rate of cercariae was investigated by experimentally infecting rainbow trout under standardized conditions, first with an increasing cercarial density and second, by keeping density constant but increasing numbers of cercariae. The per capita transmission rate was frequency dependent and averaged 0·341/h (±0·036).

We examined a host-finding factor of the monogenean Heterobothrium okamotoi oncomiracidia to develop an alternative prophylaxis. H. okamotoi oncomiracidia attached preferentially to gill filaments and skin mucus from the tiger puffer Takifugu rubripes compared with corresponding material from other tested fishes (amber jack Seriola dumerili, red sea bream Pagrus major, Japanese flounder Paralichthys olivaceus and spotted halibut Verasper variegatus). The body mucus pH of the tiger puffer was 6·40±0·09 (mean±S.D.), whereas that for the other tested fishes was 7·2–7·4. To find if this difference in pH could account for the specific targeting of tiger puffer by H. okamotoi oncomiracidia, the attachment response of the oncomiracidia to pieces of agar buffered at various pH between 6·0 and 7·4 was examined. The number of attaching oncomiracidia was maximal at pH 6·4. We produced gynogenetic tiger puffers from a single female. These gynogenetic individuals showed a variety of body mucus pH and they were exposed to the oncomiracidia. Thirteen days after exposure, more young H. okamotoi were found on the gills of gynogenetic tiger puffer with mucus at pH 6·3–6·6, than on gills of fish with mucus at pH 6·0–6·3 and 6·6–7·2. H. okamotoi exploits the body mucus pH to identify the host. The simplicity of pH as a lure may lead to development of a simple and economical method to control H. okamotoi outbreaks.

Schistosoma haematobium and S. intercalatum readily hybridize with each other producing generations of viable hybrid offspring. Experiments were designed to investigate the infectivity and viability of the S. haematobium×S. intercalatum F1 and F2 hybrid larvae in their two intermediate snail hosts compared with the parental species. Analysis of the data obtained suggested that the S. haematobium [male ]×S. intercalatum [female] F1 hybrid miracidia were more infective to Bulinus truncatus than to B. forskalii, and also more infective to B. truncatus compared with the parental S. haematobium miracidia. This hybrid was also observed to have a greater cercarial productivity from both intermediate hosts and these cercariae were shown to be more infectious and to have a longer longevity compared with the cercariae of S. haematobium, S. intercalatum and the S. haematobium [female]×S. intercalatum [male ] F1 hybrid cercariae. The S. haematobium [female]×S. intercalatum [male ] F1 hybrid was shown not to be very successful in all stages of the investigations. The results indicate that the S. haematobium [male ]×S. intercalatum [female] F1 hybrid may have many reproductive advantages over the reciprocal hybrid and the parental schistosome species. The significance of the results is discussed in relation to the epidemiological consequences occurring in Loum, Cameroon, and other areas where S. haematobium and S. intercalatum are sympatric and able to hybridize.

The population biology of the schistosome-vector snail Bulinus truncatus was studied in an irrigation area near Marrakech, Morocco, using demographic approaches, in order to estimate life-history parameters. The survey was conducted using 2 capture-mark-recapture analyses in 2 separate sites from the irrigation area, the first one in 1999 and the second one in 2000. Individuals larger than 5 mm were considered. The capture probability varied through time and space in both analyses. Apparent survival (from 0·7 to 1 per period of 2–3 days) varied with time and space (a series of sinks was considered), as well as a square function of size. These results suggest variation in population intrinsic rate of increase. They also suggest that results from more classical analyses of population demography, aiming, for example at estimating population size, should be interpreted with caution. Together with other results obtained in the same irrigation area, they also lead to some suggestions for population control.

A variety of fluorescent probes have been used to study the acidic compartments in cercariae and schistosomula of Schistosoma mansoni. Freshly transformed schistosomula treated with the LysoTracker Red dye specific for lysosomes showed large acid-containing compartments (0·5–10 μm in size). The uptake of the dye is an energy-dependent process that depends on the metabolic activity of schistosomula. The compartments were quantified individually with respect to area, quantity of fluorescence and the total number/schistosomulum. Under normal conditions these compartments were not found in untreated cercariae, but appeared in cercariae slightly damaged by poly-L-lysine. The formation of these compartments seemed to be related to the development of cercariae into schistosomula as the number of compartments and uptake of fluorescence increased with time after transformation. Also, the method of transformation as well as the in vitro incubation of the parasite affected the percentage area of compartments/schistosomulum. Acid phosphatase enzyme activity was assessed using an endogenous phosphatase probe. Living and fixed schistosomula displayed the presence of enzyme activity in compartments of the same size and distribution as the acid-rich compartments. This was confirmed by histochemical staining showing deposition of enzyme-generated lead at the sites of phosphatase activity. We suggest that the development of acidic compartments is important during the transformation process or as a consequence of damage.

Trypanosomes isolated from South American bats include the human pathogen Trypanosoma cruzi. Other Trypanosoma spp. that have been found exclusively in bats are not well characterized at the DNA sequence level and we have therefore used the SL RNA gene to differentiate and characterize kinetoplastids isolated from bats in South America. A Trypanosoma sp. isolated from bats in southern Brazil was compared with the geographically diverse isolates T. cruzi marinkellei, T. vespertilionis, and T. dionisii. Analysis of the SL RNA gene repeats revealed size and sequence variability among these bat trypanosomes. We have developed hybridization probes to separate these bat isolates and have analysed the DNA sequence data to estimate their relatedness. A new species, Trypanosoma desterrensis sp. n., is proposed, for which a 5S rRNA gene was also found within the SL RNA repeat.

Thirty-one stocks of Trypanosoma cruzi, the agent of Chagas disease, representative of the genetic variability of the 2 principal lineages, that subdivide T. cruzi, were selected on the basis of previous multilocus enzyme electrophoresis analysis using 21 loci. Analyses were performed with lower numbers of loci to explore the impact of the number of loci on the robustness of the phylogenies obtained, and to identify the loci that have more impact on the phylogeny. Analyses were performed with numerical (UPGMA) and cladistical (Wagner parsimony analysis) methods for all sets of loci. Robustness of the phylogenies obtained was estimated by bootstrap analysis. Low numbers of randomly selected loci (6) were sufficient to demonstrate genetic heterogeneity among the stocks studied. However, they were unable to give reliable phylogenetic information. A higher number of randomly selected loci (15 and more) were required to reach this goal. All loci did not convey equivalent information. The more variable loci detected a greater genetic heterogeneity among the stocks, whereas the least variable loci were better for robust clustering. Finally, analysis was performed with only 5 and 9 loci bearing synapomorphic allozyme characters previously identified among larger samples of stocks. A set of 9 such loci was able to uncover both genetic heterogeneity among the stocks and to build robust phylogenies. It can therefore be recommended as a minimum set of isoenzyme loci that bring maximal information for all studies aiming to explore the phylogenetic diversity of a new set of T. cruzi stocks and for any preliminary genetic typing. Moreover, our results show that bootstrap analysis, like any statistics, is highly dependent upon the information available and that absolute bootstrap figures should be cautiously interpreted.

Since 2 morphological forms (fertilized and unfertilized) of egg can be produced by Ascaris, infected humans can release in their faeces fertilized eggs only (FEO), unfertilized eggs only (UEO) or both fertilized and unfertilized eggs (FUE) (designated herein as the 3 different egg profiles). Epidemiologically, fertilized eggs are of significance as they enable effective transmission of the parasite. This study, for the first time, characterizes the Ascaris egg profiles in human faeces in an endemic region of China, explores possible host- and parasite-factors related to these profiles, and discusses the biological and epidemiological implications of the findings. The 3 egg profiles were recorded throughout the study period of 2 years, and the overall percentages of people with FEO, FUE and UEO profiles were ~41–47%, 32–42% and 17–21%, respectively. The overall number of unfertilized eggs for the entire population accounted for ~6–9% of all eggs excreted. The different Ascaris egg profiles showed no correlation to host gender, but they did relate to age and worm burden of the host and to the sex ratio and developmental status of the parasite. While an annual universal anthelmintic treatment resulted in some fluctuation in the values of individual egg profiles, the general features of these profiles remained similar throughout the study period. The findings of this study should have significant implications for understanding transmission patterns of Ascaris and for the implementation of control measures against ascariasis in endemic regions.

A total of 35 pigs aged 15 weeks old, and 21 pigs aged 8 weeks old were divided into 7 groups. Groups 1 and 2 were uninfected and challenge control groups, respectively. Groups 3 and 4 were infected weekly with 6 increasing doses of Ascaris suum eggs, and group 4 was additionally treated with pyrantel. Groups 5, 6, and 7 were immunized weekly with the 14, 42, or 97 kDa fractions from adult worms, respectively. Animals of groups 2–7 were challenged with 10 000 A. suum eggs 7 days after the last infection/immunization. Serum was sampled weekly and specific IgG1, IgG2, and IgM responses were measured. Pigs of groups 5, 6, and 7 showed high IgG1 and IgG2 responses especially against adult worms antigens, while infected groups had high IgG1 and IgM responses, especially against larva. The IgG1 responses were negatively correlated to the numbers of larvae in the lungs, and positively associated with the liver white spot numbers. There was a positive correlation between IgG2 and the numbers of white spots and lung larvae, while IgM was negatively correlated with these parasitological measures. These findings are discussed and it is suggested that acquired resistance against A. suum larvae is correlated with the induction of IgG1 and IgM, and not with IgG2, and that future vaccination protocols may focus on inducing the Th2 activity.