We have established an amplified fragment length polymorphism (AFLP) protocol for identifying anonymous polymorphic loci of the malarial parasite, Plasmodium falciparum. The method consists of the following steps (i) digestion and ligation in one reaction; (ii) selective fluorescence forward primers labelled; (iii) PCR products resolved in polyacrylamide gels using the ABIPRISMTM 377 XL DNA sequencer and, (iv) the use of GenescanTM software to size the fragments. This standardized protocol distinguished between 2 standard reference clones of P. falciparum from West African and Southeast Asian and 2 Central African isolates from patients with clinical malaria. The AFLP protocol resulted in evenly distributed and reproducible band patterns for amplified fragments ranking from 163 to 489 bp long ±0·5 S.D. The primer Tru ACA labelled with the phosphoramidite 6-carboxifluorescein (FAM-blue) was easy to interpret, with a maximum of 53 bands per clone and of 81 per isolate (mixed falciparum populations) whereas the primer Tru AG labelled with the hexachlorinated analogue (HEX-green) showed a less clear pattern of bands and reproducibility than Tru ACA.

Treatment protocols for the chemotherapy of malaria are usually acquired through clinical trials. Once pharmacokinetic and pharmacodynamic information becomes available, it is possible to use mathematical modelling for testing these protocols and, possibly, for improving them. In this report the case of monotherapy by mefloquine is analysed. Published pharmacokinetic and clinical results are used to derive the essential model parameters such as kill rate, parasite growth rates, drug sensitivity and the pharmacokinetic parameters. Good agreement is obtained between clinical results and simulated parasite numbers using the derived parameters. It is demonstrated that the 2 exponential kinetics of mefloquine elimination can be reduced to an operational single exponent for pharmacodynamic modelling by educated choice of sampling times of plasma drug concentration. It is deduced that a second drug dose, at a properly chosen time-interval, results in radical cure even when resistant parasites are present and at maximal parasite growth rates such as those found in non-immune patients. Finally, a table is provided for guiding the optimal choice of dosing intervals under different values of population pharmacokinetics, drug resistance and individual immunity parameters.

A 58 kDa excretory–secretory product (ESP) of Giardia lamblia has been characterized. The ESP was purified over 508-fold by a combination of ammonium sulphate precipitation and sequential chromatography on affinity matrix and a gel filtration column. The homogeneity of the purified protein was established by sodium dodecyl sulphate polyacrylamide gel electrophoresis (Mr, 58 kDa) and analytical isoelectrophoresis (pI 4·75). The purified protein was recognized by the pooled sera of G. lamblia-positive patients as well as an antiserum raised against crude Giardia extract, thus indicating it to be an immunodominant parasite product. The ESP was found to agglutinate rabbit erythrocytes. The haemagglutinating activity of this protein was inhibited strongly by thyroglobulin, fetuin, asialofetuin and monosialoganglioside but not by simple sugars. The purified protein was characterized immunochemically and was found to be heat stable as well as protease sensitive. Lectin-binding studies of the purified ESP and its sensitivity to periodic-acid silver staining as well as to metaperiodate treatment clearly indicated its glycoprotein nature. The major localization site of the ESP was found to be on the surface of the parasite as revealed by flow cytometric analysis. Further, this glycoprotein induced fluid accumulation in ligated rabbit ileal loops and revealed a positive skin permeability reaction in the rabbit.

The microaerophilous stationary phase system (MASP) was introduced in 1980 and successfully used as a standard technique for Babesia bovis and B. bigemina in vitro culture. The percentage of serum in the medium and the dependence on specific serum donors have been recognized as important constraints both for immunochemical studies and for the logistics of culture routine. In the present study the supplementation of RPMI 1640 with hypoxanthine at a concentration between 50 and 200 μM has enabled patterns of growth of B. bovis and B. bigemina to be achieved comparable to the standard technique with a simultaneous reduction of serum concentration from 40% to 5%. With hypoxanthine-supplemented medium it was possible to either replace the bovine serum from a specific donor with horse serum or use commercial adult bovine serum or foetal calf serum at 10%. When the serum replacement media Albumax II and GF21 were used, the growth of both B. bovis and B. bigemina markedly decreased after 3×72 h cycles. However, when these species were cultivated in culture flasks previously coated with cells from a murine peritoneal lavage, continuous parasite growth was achieved.

Using laboratory-bred natural rodent hosts that had been castrated and then implanted with either testosterone or inert oil, we have shown that testosterone causes prolonged and more intense infections of a tick-borne piroplasm, Babesia microti. This will result in more ticks becoming infected while feeding. Sexually active male rodents with high testosterone levels are also known to show increased locomotory activity and reduced innate and acquired resistance to tick feeding, so that more ticks are likely to be picked up and then fed successfully by these hosts. As a result, the transmission potential of B. microti is significantly increased via hosts with high rather than low testosterone levels. It is argued that testosterone helps to generate the observed aggregated distributions of parasites amongst their hosts, which also enhances parasite persistence.

Several studies have confirmed that epidermal Langerhans' cells (LC) play a central role in the induction of skin-related immunological events. In order to assess the role of LC in Chagas' disease, guinea-pigs were infected intradermally with Trypanosoma cruzi, sacrificed at different time-points, and their tissues were processed for routine histology, electron microscopy and immunohistochemistry. Parasitaemia was observed earliest at day 6 p.i. with 2 peaks at days 9 and 28, and disappeared on day 56 p.i. Parasite-specific serum IgG and IgM were first detected on day 12 p.i. The level of IgG gradually increased by day 84 p.i. All the infected guinea-pigs showed significant alterations in the distribution and morphology of epidermal LC during parasitaemia. The number of LC had significantly decreased in the epidermis by day 3 p.i., only returning to normal levels by day 56 p.i., although the number of LC in the underlying dermis increased concomitantly. Parasites were carried to the regional lymph node, where clustering of parasite-laden dendritic cells (DC) with lymphocytes was seen by electron microscopy. This evidence suggests that LC might be involved in antigen presentation in Chagas' disease.

A 186 bp Echinococcus granulosus-specific repetitive element, TREg, was used to assess genetic variation between strains. In G7 genotype (pig strain) it has the characteristics of a satellite DNA element with a copy number of 23000 per haploid genome. Analysis, by sequencing of TREg monomers, showed a great degree of identity within them. In the G1 genotype (common sheep strain) TREg-like repetitive elements were found in an interspersed distribution throughout the genome and in only 120 copies. The sequences of these monomers showed a great degree of variation between them and with TREg of G7 origin. The G6 genotype (camel strain) showed a pattern of distribution and copy number similar to the G7 genotype, and the G2 genotype (Tasmanian sheep strain) similar to the G1 genotype. Isolates from the G5 (cattle strain) and G4 (horse strain) genotypes also showed unique hybridization patterns in Southern blot experiments. The genomic plasticity of E. granulosus, which may have important consequences in the epidemiology and control of cystic hydatid disease is reflected in the results of this work.

We studied variation in the structure of component communities of helminths in sand lizards, Lacerta agilis, from 30 localities in the Ukraine and Bulgaria. Thirty-five separate samples of lizards, with a total of 661 completely censused infracommunities, yielded 30 helminth species (4 cestodes, 10 trematodes, 3 acanthocephalans and 13 nematodes). In its range within the Ukraine, L. agilis serves as the final host for 13 species of which only 3 (S. lacertae, S. hoffmanni and P. molini) can be considered as lizard specialists. A characteristic feature of these helminth component communities was the large proportion of heteroxeneous helminth species for which L. agilis serves as paratenic host. Sand lizards in the meadow steppeland zone were primarily parasitized by larval helminths that represented a major proportion of the total number of all worms recovered while those sampled in the grassland/forest transition zone were characterized by substantially higher proportions of adult helminths using lizards as final hosts. However, L. agilis was parasitized by a much higher proportion of lizard specialists in the ‘typical' habitats of the meadow steppeland zone as opposed to those located in ‘marginal' habitats in the grassland/forest transition zone, where helminths were shared to a greater extent with amphibian hosts.

We tested the null hypothesis that populations of hosts trapped in isolated neighbouring locations showing comparable habitat quality, should support similar helminth parasite communities. The study was undertaken in a 2-week period in late summer in NE Poland in a single year, thereby eliminating seasonal and between-year variation in parasite burdens. A total of 139 Clethrionomys glareolus (bank vole) were sampled from 3 forest sites of similar habitat quality. Total species richness was 11 (6 nematodes and 5 cestodes) with 85·6% of the voles carrying at least 1 species and an overall mean species richness of 1·4. At the component community level, the fewest species of helminths were recorded from site 2 (n = 6, compared with 9 at each of the other sites), but site 3 had the lowest Berger-Parker Dominance Index and the highest Simpson's Index of Diversity. At the infracommunity level, site 3 had the highest mean no. of helminth species/vole, the highest mean Brillouin's Index of Diversity but the lowest mean no. of helminths/vole. Voles from sites 1 and 3 differed in the nematodes that were most common (site 1, Heligmosomum mixtum – 95%; site 3, Heligmosomoides glareoli – 79·3%). At site 2 no species exceeded 50% but prevalence of Syphacia petrusewiczi was higher than at the other sites. The prevalence of cestodes was too low to test reliably (12·9%), but the highest prevalence of adult cestodes was recorded at site 1 (22·5% compared with 4·9 and 1·7% for sites 2 and 3 respectively). Host sex did not influence infection, but mean species richness increased with age. The different sites were responsible for most of the variation in our data, and the intrinsic factors (sex and age) were less important in shaping the component community structure of helminths. We conclude that even locations in relative close proximity to one another (13–25 km), selected on the basis of similar habitat quality, have rodent populations that differ in their helminth parasite communities, although for reasons other than the factors quantified in the present study.

Pats of pig faeces containing known numbers of Oesophagostomum dentatum eggs were placed on plots with bare soil, short or tall herbage on 8 occasions during 1 year. The number of eggs and larvae and the relative distribution of larvae in faeces, soil and herbage was monitored for 1 year after deposition. On 2 occasions soil from 8 selected plots was given to pigs, which were later slaughtered and examined for the presence of adult O. dentatum. Less than 1% of the deposited eggs could be recovered as infective larvae. The highest recoveries were generally made on tall herbage plots. The majority of infective larvae was found within the faecal pats, which indicates that infective O. dentatum larvae, to a large extent, do not disperse onto the herbage or into soil. The infective larval stage was reached only when the mean temperature in the weeks post-deposition was above 10 °C. This stage was reached within 1 week when the mean weekly temperature was above 13 °C. After the winter period no infective larvae could be recovered from any plots and no parasitic worms could be isolated from pigs fed soil from 8 selected plots.