Kinetoplastid parasites are responsible for serious diseases in humans and livestock such as Chagas disease and sleeping sickness (caused by Trypanosoma cruzi and Trypanosoma brucei, respectively), and the different forms of cutaneous, mucocutaneous and visceral leishmaniasis (produced by Leishmania spp). The limited number of antiparasitic drugs available together with the emergence of resistance underscores the need for new therapeutic agents with novel mechanisms of action. The use of agents binding to surface glycans has been recently suggested as a new approach to antitrypanosomal design and a series of peptidic and non-peptidic carbohydrate-binding agents have been identified as antiparasitics showing efficacy in animal models of sleeping sickness. Here we provide an overview of the nature of surface glycans in three kinetoplastid parasites, T. cruzi, T. brucei and Leishmania. Their role in virulence and host cell invasion is highlighted with the aim of identifying specific glycan–lectin interactions and carbohydrate functions that may be the target of novel carbohydrate-binding agents with therapeutic applications.

A molecular approach was used to genetically characterize 5 species (Aoruroides queenslandensis, Blattophila sphaerolaima, Cordonicola gibsoni, Desmicola ornata and Leidynemella fusiformis) belonging to the superfamily Thelastomatoidea (Nematoda: Oxyurida), a group of pinworms that parasitizes terrestrial arthropods. The D3 domain of the large subunit of nuclear ribosomal RNA (LSU) was sequenced for individual specimens, and the analysis of the sequence data allowed the genetic relationships of the 5 species to be studiedNucleotide sequence data reported in this paper are available in the GenBank®, EMBL and DDBJ databases under the Accession numbers: AM232755–AM232763.. The sequence variation in the D3 domain within individual species (0–1·8%) was significantly less than the differences among species (4·3–12·4%). Phylogenetic analyses, using maximum parsimony, maximum likelihood, and neighbour-joining, tree-building methods, established relationships among the 5 species of Thelastomatoidea and Oxyuris equi (a species of the order Oxyurida). The molecular approach employed provides the prospect for developing DNA tools for the specific identification of the Thelastomatoidea, irrespective of developmental stage and sex, as a basis for systematic, ecological and/or population genetic investigations of members within this superfamily.

The inheritance of variant surface antigens in Trypanosoma brucei has been determined by identifying variable antigen types (VATs) in each of two cloned parental stocks and then examining the presence and abundance of these VATs in hybrid progeny produced when these stocks undergo genetic exchange during co-transmission through tsetse flies. Nine VATs have been identified from the repertoire of the parental stock STIB 247L and 5 VATs have been identified from the parental stock STIB 386AA; the identified VATs were exclusive to each stock. Their inheritance was elucidated using two assays. In the first, repertoire antisera (RAS) containing antibody specificities to many different VATs were raised in rabbits to the 2 parental stocks and 6 progeny clones. The presence of VAT-specific antibodies in these RAS was then determined by antibody-dependent complement-mediated lysis. In the second assay, the 2 parental stocks and 4 hybrid progeny clones were each independently transmitted through tsetse flies and VATs observed using VAT-specific antisera in indirect immunofluorescence of metacyclic trypanosomes and in bloodstream forms of fly-bitten mice. The results from both assays showed that (1) both metacyclic- and bloodstream-VATs were inherited into the progeny, (2) each hybrid progeny clone contained some VATs from both parents, (3) hybrids did not express all the VATs from either parent, (4) there was little apparent pattern as to which VATs had been inherited and which had not and (5) the VAT repertoires of the hybrid progeny appeared to be larger than those of the parents. In addition, two results indicated that control of VAT expression remains unaltered after genetic exchange. Firstly, the immunofluorescence results showed that VATs present in hybrid trypanosomes were expressed at the same stage during an infection and at approximately the same prevalence as in the parent. Secondly, a double-labelling experiment using direct immunofluorescence indicated that individual hybrid trypanosomes did not generally simultaneously express more than one VAT. Taken together, these results demonstrate that recombinant VAT repertoires are created when trypanosomes undergo genetic exchange and that genetic exchange is a mechanism whereby the generation of new serodemes can occur.

1. Both male and female N. fasciatus normally require a blood meal before they will mate.

2. Fed males do not attempt to mate with unfed females. It is suggested that the taking of a blood meal enables the female to provide a stimulus necessary for the male to show mating behaviour.

3. Unfed Nosopsyllus of both sexes will mate if subjected to a temperature between 30 and 35°C inclusive. Above 35° mating does not occur.

4. Below 30°C mating occurs only if the fleas have previously been subjected to a temperature of 30°C or above. A temperature rise to the critical point thus acts as a trigger for an enabling process which continues after temperature has again fallen.

5. It is suggested that the effect of a blood meal in enabling mating to occur may be explained by the fleas' experience, while on the host, of a rise in temperature to the level critical for mating.

A technique is described for the growth of pure gametocyte cultures of Plasmodium falciparum. Using the classification of Hawking, Wilson & Gammage (1971) these cultures contain gametocytes of stages III, IV and V alone. Routine sexual cultures, varying from 0·35 ml static cultures to 500 ml shaking cultures, are exposed to an inhibitor of DNA synthesis (mitomycin C at 10 μg/ml) on the 11th day of culture, and the culture is harvested on the 14th day when capacitated stage V gametocytes are present. All other stages are killed by the drug and are morphologically degenerate within 2 days of the addition of the inhibitor.

Parasite dynamics can be mediated by host behaviours such as sociality, and seasonal changes in aggregation may influence risk of parasite exposure. We used little brown bats (Myotis lucifugus) captured during the autumn mating/swarming period to test the hypothesis that seasonal and demographic-based variation in sociality affect ectoparasitism. We predicted that ectoparasitism would: (1) be higher for adult females and young of the year (YOY) than adult males because of female coloniality; (2) increase for adult males throughout swarming because of increasing contact with females; (3) decrease for adult females and YOY throughout swarming because of reduced coloniality and transmission of individual ectoparasites to males; (4) be similar for male and female YOY because vertical transmission from adult females should be similar. Ectoparasitism was lowest for adult males and increased for males during swarming, but some effects of demographic were unexpected. Contrary to our prediction, ectoparasitism increased for adult females throughout swarming and YOY males also hosted fewer ectoparasites compared with adult and YOY females. Interestingly, females in the best body condition had the highest parasite loads. Our results suggest that host energetic constraints associated with future reproduction affect pre-hibernation parasite dynamics in bats.

Taenia multiceps coenurus fluid was analysed by fast protein liquid chromatography in order to separate the factors responsible for previously reported modification of immunological activity in macrophages and T-cells. One factor, F7, was found to be mitogenic for murine L3T4+ T-cells, to be macrophage dependent, to require macrophage compatibility at the I region of the H2 complex, to increase the sensitivity of T-cells to regulatory signals from macrophages and to increase the rate of generation of splenic rosette-forming cells (RFC) against sheep red cells. A second factor, F24, was found to alter macrophages so as to render them suppressive, rather than stimulatory, for parasite-activated and Con A-activated lymphocyte transformation, to depress the rate of generation of RFC and to antagonize the mitogenic effect of F7. The combined actions of these two factors are, therefore, sufficient to explain the known immunomodulatory effects of the metacestode.

When sporozoites of Eimeria tenella were inoculated into an isolated horn of the bicornuate caecum of the domestic fowl, replicating infections, culminating in the production of oocysts, were found, almost exclusively, in the inoculated horn. In contrast, sporozoites of E. tenella introduced into the bloodstream via a superficial vein induced infections of equivalent intensity in both horns of the caecum. These findings are discussed with reference to (1) the detection (by tissue transfer) of infective sporozoites in samples of cardiac blood and vascular tissues taken within 3 to 18 h of the oral inoculation of oocysts, and (2) the (previously published) observation that the sporozoites of E. tenella are transported from the superficial epithelium of the caecum (site of invasion) to the crypts (site of initial development) within host intra-epithelial lymphocytes. We suggest that a local inflammatory response to the invasion of sporozoites may be responsible for their re-location in proximity to the site of entry. This could act by directing the homing (or retention) of the parasite-bearing lymphocytes, and/or by providing a stimulus for the sporozoite to leave its transporting cell.

1. The following strains produced no infection in any of the laboratorybred Glossina used in their examination; the total number of flies dissected is given for each strain:

T. gambiense, strain V, Uganda, isolated in 1926 … … … 548

T. gambiense, strain Adero, Uganda, isolated in Jan. 1933 … 1642

T. rhodesiense, Liverpool, isolated in Jan. 1933 …. … … 750

T. rhodesiense, Liverpool, arsenic-fast variant … … … … 1166

T. brucei, “Hamburg alt” from Berlin; isolated over 30 years ago 2452

Some of the flies used in testing each of these strains were kept at 95–97° F. during their infecting feeds.

2. T. gambiense, strain “Braun,” isolated in February, 1920, gave two “gut only” infections in 1137 flies. T. gambiense, strain “McA,” isolated in 1921, produced one very light infection, of the intestinal tract only, in 1410 flies employed. This infected fly died on the 27th day after its infecting feed.

T. brucei, strain “Hornby mild,” isolated at the end of 1930, gave three infections of the intestinal tract only in 1443 flies used. Some of the flies employed on these three strains were kept during their infecting feeds at 95–97° F., but the infected flies came from boxes kept at room temperature throughout.

It will be seen that all the strains hitherto summarised are, as far as these tests are concerned, non-transmissible by Glossina, and the majority are no longer capable of infecting even the intestine of the fly.

3. T. brucei, strain “Hornby virulent,” isolated in April, 1927, from a heifer, and found by Corson in 1931 to be readily transmissible by G. morsitans or G. pallidipes (or both), 4½ years after its first isolation (Corson, 1932). A month or so later this strain was found at Entebbe to be still feebly transmissible by G. palpalis and somewhat more readily by G. morsitans, although much less so than in Corson's experiments.

4. Strain “Br,” considered by Prof. J. G. Thomson to be a T. gambiense showing some resemblances to T. rhodesiense, when examined at Entebbe some three years after its isolation from a European in West Africa, proved to be still infective to both G. palpalis and G. morsitans through only very feebly transmissible. 4272 laboratory-bred flies were used in the examination of this strain: 74 of these developed infection of the intestine, and only one a gland infection—a G. palpalis dying on the 40th day after its infecting feed. Flagellates were numerous in the glands of this fly.

5. The behaviour of the “Hornby virulent” strain of T. brucei and of strain “Br” suggests that completion of the cycle in the fly may be delayed beyond the 25–30 days usually sufficient for East African strains, and it is possible that this delay may be a feature characteristic of strains whose transmissibility by tsetse is undergoing reduction. On the other hand, the solitary infective fly obtained with strain “Br” had a heavy gland infection which had in all probability been present at least for several days before the death of this insect.

6. A strain freshly isolated from a native who was infected on or near the northern shores of Lake Victoria failed to infect any of 1642 G. palpalis used in its examination, although a number of these flies were kept at 95–97° F. during their infecting feeds.

7. The results of the investigations described in this paper lend some support to the opinion already formed as the result of numerous experiments with the polymorphic group of trypanosomes, namely that T. brucei (and, as far as can be seen, T. rhodesiense) is less prone than T. gambiense to lose touch with Glossina.

It may be that the stability of this character in T. brucei is an expression of a more perfect adjustment to environment than is possessed by T. gambiense; the latter trypanosome, which is essentially dependent on man, having not yet attained biological equilibrium in this its principal mammalian host.

Freshwater snails belonging to the genus Biomphalaria are intermediate hosts of the trematode Schistosoma mansoni in the Neotropical region and Africa. In Brazil, one subspecies and ten species of Biomphalaria have been identified: B. glabrata, B. tenagophila, B. straminea, B. occidentalis, B. peregrina, B. kuhniana, B. schrammi, B. amazonica, B. oligoza, B. intermedia and B.t. guaibensis. However, only the first three species are found naturally infected with S. mansoni. The classical identification of these planorbids is based on comparison of morphological characteristics of the shell and male and female reproductive organs, which is greatly complicated by the extensive intra-specific variation. Several molecular techniques have been used in studies on the identification, genetic structure as well as phylogenetic relationships between these groups of organisms. Using the randomly amplified polymorphic DNAs (RAPD) analysis we demonstrated that B. glabrata exhibits a remarkable degree of intra-specific polymorphism. Thus, the genetics of the snail host may be more important to the epidemiology of schistosomiasis than those of the parasite itself. Using the simple sequence repeat anchored polymerase chain reaction (SSR-PCR) in intra-populational and intra-specific studies we have demonstrated that snails belonging to the B. straminea complex (B. straminea, B. kuhniana and B. intermedia) clearly presented higher heterogeneity. Using the low stringency polymerase chain reaction (LS-PCR) technique we were able to separate B. glabrata from B. tenagophila and B. tenagophila from B. occidentalis. To separate all Brazilian Biomphalaria species we used the restriction fragment length polymorphism (PCR-RFLP) of the internal transcribed spacer region (ITS) of the DNA gene. The method also proved to be efficient for the specific identification of DNA extracted from snail eggs. Recently we have sequenced the ITS2 region for phylogenetic studies of all Biomphalaria snails from Brazil.

Kenya Colony offers a rich field for the study of ticks and tick-borne diseases. The natural conditions under which both ticks and the diseases exist range from those of the hot, low-lying coastal lands to the equable climate of the highlands culminating in the colder upland country and mountain slopes. The variety of conditions is also attributable to the extensive tracts of bush-covered country, the high plateaux with their scanty growth of vegetation, and to the forest-clad ridges and mountains.

A low molecular weight (15 kDa) surface antigen of the cattle filarial nematode, Setaria digitata, was earlier shown to be specifically recognized by the antibodies from human bancroftian filarial (Mf positive) patients' sera (Theodore & Kaliraj, 1990). The filarial specific antibodies bound to a 15 kDa peptide in preparative Western blots were eluted and employed in screening of candidate antigens expressed in the genomic library of Wuchereria bancrofti at the IgG4 subclass antibody level. A recombinant clone (λ WbG7) reacting strongly with filarial sera but poorly with sera from patients infected with non-filarial helminths was selected for further studies. The 2 kb DNA insert of the clone λ WbG7 was recloned into a pMAL vector and the recombinant clone pGT7 thus obtained was over-expressed and affinity purified. The purified 105 kDa fusion protein of the clone pGT7 was specific and was not recognized by the non-filarial sera at the IgG4 level. All microfilaraemic individuals were positive by IgG4 assay. However, similar attempts to diagnose by filarial-specific IgE assays failed to recognize microfilaraemic individuals. Moreover, by filarial-specific IgG4 assays, the endemic normals were distinctly divided into two groups, showing higher and lower recognition for this antigen indicating current and past/no infection. Among the filarial-IgG4 (assay)-positive ‘endemic normals’, 14% showed ‘microfilariae’ during repeated peripheral night blood examination, confirming the validity of the recombinant antigen, pGT7 based assay.

The free-living phase of the life-cycle of Nematodirus helvetianus was studied out of doors on grass plots and the effects of temperature and humidity on the free-living stages were studied in the laboratory. The results of these observations are discussed in relation to the bionomics of N. battus and N. filicollis, and tentative deductions made regarding the epidemiology of N. helvetianus infection.

I wish to thank Mr J. Bailey for technical assistance.

Infective Haemonchus contortus cayugensis larvae were rapidly exsheathed (20 min) using 0·02 m-Na2B4O7. 10H2O, a gas mixture of 40 % CO2–60 % N2, and subsequent aeration with compressed air as reported previously. Several variables in this system were examined. The optimum concentration of sodium tetraborate was found to be 0·02 m. The exsheathment rate decreased with increasing molarities of the salt over the range 0·02–0·08 m. Exsheathment rates were low when the larvae received the full stimulus to exsheath for only 5 and 10 min before aeration. The larvae required at least 15 min of the full stimulus before aeration to ensure high exsheathment rates. The rapid method of ecdysis caused no abnormalities in or death of larvae, and all the larvae at the end of the incubation period were very motile and appeared normal. The exsheathment rate was consistently high as the larval concentration was increased from 2 ×103 to 2×106/10 ml of 0·02 m-Na2B4O7. 10H2O.

The most conspicuous feature of the spiracle of Ornithodoros moubata is the so-called cribriform plate. This is a massive crescent-shaped vesicle consisting of three layers; the underlying sclerotized endocuticle, a series of branching pillars or pedicels arising from this basal layer and a very thin outer membrane, supported on the distal ends of the pillars and enclosing the whole structure (Fig. 1 A). The cavity lying between the basal cuticle and the outer membrane and ramifying between the pillars is continuous with the atrium of the spiracle.

1. The in vivo growth of Schistocephalus solidus plerocercoids was investigated by surgical implantation of worms into the body cavity of uninfected, recipient sticklebacks.2. Burdens of one, two and five worms were used.3. Results show a reduction in parasite growth with both increasing size and increasing numbers of parasites.4. Reasons for the decrease in growth rate of multiple burdens are discussed and reference is made to the significance of burden size in completion of the life-cycle under natural conditions.

Selfing has been considered the most common mode of reproduction in Echinococcus flatworms. However, population genetic studies on the asexual larval stage involving nuclear co-dominant markers have not always revealed significant heterozygote deficiencies – the expected outcome of a regularly and highly inbred population. In this study, we analysed the genetic structure of Echinococcus granulosus sensu lato populations from Southern Brazil during their adult (sexual) stage using 1 mitochondrial and 1 nuclear marker (cox 1 and mdh, respectively). We show that parasite genetic differentiation is largest among definitive hosts (domestic dogs) from different farms, suggesting that transmission is mostly maintained within a farm. Moreover, we show that heterozygote deficiencies are not significant, and we suggest that outbreeding is the most common mode of reproduction of the parasite in that region.

In 1915 Dowden reported a suspected case of tsutsugamushi disease, or Japanese river fever, from the Federated Malay States. Twelve years later Fletcher and Field (1927) were able to examine a series of cases and established Allothrombium. This spelling is adopted by Oudemans. In the absence of definite evidence of the original derivation, it would appear, in the light of Opinion 34 of the Rules, that the original spelling should be preserved, and Trombicula is therefore used in this paper.

This study evaluated a relatively new molecular technique, serial analysis of gene expression (SAGE), as a tool for quantifying gene expression in the ovine abomasal nematode Haemonchus contortus for which there is relatively limited (~20% gene coverage) sequence information. SAGE technology generates data that are both qualitative and quantitative and, as such, compliments other functional genomics approaches such as EST analysis and micro-array. Prior to embarking on large-scale comparisons, the present study was initiated to establish (i) how well SAGE and EST data taken from the same life-cycle stage would compare, (ii) how easily SAGE tags could be assigned to genes given that the genome sequence is not available and (iii) whether it would be possible to extend the sequences of the SAGE tags to facilitate their identification. Of 2825 tag sequences analysed from adults harvested 28 days post-infection, the identity of the encoding gene could be ascribed to 63% of the tags. The relative abundance of these genes, arbitrarily categorized on the basis of function, was comparable with that of an EST dataset also from adults (n=2317). In addition, tag sequences could be readily extended and thereby identified using a tag-based primer and Reverse Transcription-PCR.