One diphyllidean and five tetraphyllidean cestodes from Australian elasmobranchs are described and figured. Echinobothrium heroniensis sp.nov., from Himantura granulata (Macleay, 1883) possesses two groups each of 42 apical hooks, eight rows each of 25 hooks on the cephalic peduncle and ten testes in each proglottid. In Anthobothrium sexorchidum sp.nov. from T. lymna (Forskal, 1775) there are only six testes and the bothridium is irregularly divided into a number of shallow areolae while in Rhinebothrium himanturi sp.nov. from Himantura granulata there are 22 proglottids, 52 loculi and 19–20 testes. Comments are made on the taxonomy of Rhinebothrium sp., Spiniloculus mavensis and Yorkeria parva. The value of some helminths, especially cestodes from elasmobranchs, as an aid to the study of the taxonomy, biology and zoogeography of their hosts is briefly discussed with reference to some previous papers on this topic. Previous work on the cestodes of Australasian marine fishes is summarized briefly.

Of the 7 genetic assemblages of the parasite Giardia duodenalis only 2 (A and B) are known to cause infections in humans. These assemblages have been characterized in detail at the genomic level but few studies have examined differences in the proteins expressed. Employing one and two-dimensional PAGE we have identified an assemblage A-specific protein of human infective G. duodenalis; alpha 2 giardin. The protein difference was evident using both electrophoretic techniques. Alpha 2 giardin is known to be a structural protein and associates with the caudal flagella and the plasma membrane; however, its exact function is unknown. Although several proteins unique to assemblage B were also observed, we were unable to identify these proteins due to a lack of genomic data available for assemblage B isolates. Together, these proteins represent distinct phenotypic differences between the human infective assemblages of G. duodenalis and support the need to revise the taxonomy of this parasite.

This study describes the effects of testosterone (Te) on the intestinal nematode Heterakis spumosa in mice. The course of Heterakis infections is apparently under Te-control. At high circulating Te-levels as occurring in intact males, Te-treated females, and Te-treated castrated males, the period of release of Heterakis eggs in mouse faeces is greatly extended and the number of eggs released per unit time is markedly elevated in comparison to low Te-levels, as found in untreated females and castrated male mice. Also, the onset of the patent period occurs earlier in Te-treated mice. Testosterone also accelerates development and growth of both female and male worms of Heterakis in mice. Thus, young adult male worms can be observed in the upper colon of Te-treated castrated male mice on day 21 post-infection (p. i.), whereas, at that time, only L4 larvae are present in Te-untreated male castrates. Testosterone also favours the survival of nematodes in hosts. In untreated male castrates, the number of worms present on day 7 p.i. (L2 larvae) is approximately two thirds higher than that found on day 21 p.i. However, such a reduction in the number of worms does not occur in Te-treated castrated mice during the same period of time. The early phases of the life-cycle of Heterakis, i.e. hatching in the small intestine and final settling of L2 larvae in the upper colon are independent of Te. Also, Te does not affect motility and even slightly reduces the fecundity of adult female worms in vitro. Our data suggest that Te and/or Te-metabolites and/or Te-induced host factor(s) accelerate the development and growth of H. spumosa and favour the survival of Heterakis in the colon of mice.

Seasonal dynamics of Pneumocystis carinii in the field vole, Microtus agrestis, and in the common shrew, Sorex araneus, were investigated in southern and central Finland by microscopical examination of methenamine silver-stained tissue sections. In both host species at both localities the number of P. carinii cyst forms was highest in late autumn (November). In S. araneus, prevalence was higher than in M. agrestis during all seasons. None of the animals was heavily infected or apparently ill, and neither species showed any extrapulmonary dissemination. In this study covering an increase phase and 4 peak host-density phases of the vole cycle, the occurrence of P. carinii seemed to be related to the population density of M. agrestis.

This study was conducted to determine the genotypes of Giardia duodenalis isolated from human faecal samples at Pos Betau, Pahang, Malaysia. Faecal specimens were collected and examined for G. duodenalis cysts using Trichrome staining techniques. Molecular identification was carried out by the amplification of a region of the small subunit of the nuclear ribosomal RNA (SSU rRNA) gene using nested PCR and subsequent sequencing. The sequences from 15 isolates from G. duodenalis were subjected to phylogenetic analysis (including appropriate outgroups) using the neighbor-joining and maximum parsimony methods. The trees identified G. duodenalis assemblages A and B, with a predominance of assemblage B. The predominance of anthroponotic genotypes indicates the possibility of anthroponotic transmission of these protozoa in this Semai Pahang Orang Asli community.

Evidence for the presence of 11 intestinal parasites in pre-school children from 4 rural villages in Ghana was obtained from an examination of stool samples. Striking differences were detected between the prevalence of some of the 6 common infections in the 4 villages. The prevalance of Ascaris lumbricoides varied from about 76% in one village (Oshiyie, coastal savanna) to apparently 0% in another (Akuma, forest zone). No differences in prevalence for any infection were observed to be sex dependent. Investigation of the relationship between age of the children and prevalance showed that the degree of prevalence of both A. lumbricoides and Trichuris trichiura had essentially levelled off by the time the children were 4 years old. There was no evidence to suggest that the prevalence of either Entamoeba sp. or spp. or hookworm was approaching a maximum value, even in the oldest children. These trends applied across the villages regardless of the differences in prevalence values for the infections. On average, the children of Oshiyie were found to harbour twice as many infections as the children of the other villages. The investigation of the prevalence data revealed evidence of associations between pairs of infections, particularly those involving hookworm and T. trichiura.

The expression of proteolytic activities in the Trypanosomatidae family was explored as a potential marker to discriminate between the morphologically indistinguishable flagellates isolated from insects and plants. We have comparatively analysed the proteolytic profiles of 19 monoxenous trypanosomatids (Herpetomonas anglusteri, H. samuelpessoai, H. mariadeanei, H. roitmani, H. muscarum ingenoplastis, H. muscarum muscarum, H. megaseliae, H. dendoderi, Herpetomoas sp., Crithidia oncopelti, C. deanei, C. acanthocephali, C. harmosa, C. fasciculata, C. guilhermei, C. luciliae, Blastocrithidia culicis, Leptomonas samueli and Lept. seymouri) and 4 heteroxenous flagellates (Phytomonas serpens, P. mcgheei, Trypanosoma cruzi and Leishmania amazonensis) by in situ detection of enzyme activities on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS–PAGE ) containing co-polymerized gelatine as substrate, in association with specific proteinase inhibitors. All 23 trypanosomatids expressed at least 1 acidic proteolytic enzyme. In addition, a characteristic and specific pattern of cell-associated metallo and/or cysteine proteinases was observed, except for the similar profiles detected in 2 Herpetomonas (H. anglusteri and H. samuelpessoai) and 3 Crithidia (C. fasciculata, C. guilhermei and C. luciliae) species. However, these flagellates released distinct secretory proteinase profiles into the extracellular medium. These findings strongly suggest that the association of cellular and secretory proteinase pattern could represent a useful marker to help trypanosomatid identification.

The life-cycle of a precocious and attenuated line (WisF96) of Eimeria tenella, derived from the Wisconsin (Wis) strain, contained only the first of the three generations of schizogony undergone by the parent strain. The reproductive capacity of WisF96 was less than that of the parent strain by a factor of about 2000, but inoculation of chickens on two occasions with a large number of its oocysts induced resistance against challenge with oocysts, or with second-generation merozoites of Wis. The immunizing abilities of the attenuated line and its parent were compared by priming groups of chickens with numbers of oocysts of WisF96 or Wis, designed to produce infections of equal magnitude in terms of oocyst production (standard inocula), and then challenging with oocysts of Wis. The results suggested that an equivalent parasite mass of WisF96 was more immunogenic than Wis. This was confirmed by the finding that, even when the priming dose of Wis was increased 10-fold, the standard inoculum of WisF96 still produced the greater protective effect. These results indicate that the first generation of schizogony of E. tenella is highly immunogenic.

Concentrations of lead, determined by electrothermal atomic absorption spectrometry, were compared between the cestodes Hymenolepis diminuta and Taenia taeniaeformis and its host rat (Rattus norvegicus). Rats were sampled at 2 sites, which differed in respect to lead pollution as quantified from road dust, adjacent to the city of Cairo, Egypt. Comparing lead levels among host tissues and the parasites the significantly highest accumulation was found in H. diminuta, followed by rat kidney and larvae of T. taeniaeformis. Calculation of bioconcentration factors showed that H. diminuta contained 36-, 29-, 6- and 6-fold higher lead levels than intestinal wall, liver, kidney and larvae of T. taeniaeformis, at the more polluted site. At the less contaminated site lead bioconcentration factors for H. diminuta were found to be 87, 87 and 11 referred to intestine, liver and kidney of the host. Due to a high variability of the lead concentrations in H. diminuta it was not possible to indicate differences in metal pollution between both sampling sites. This variability may be influenced by different age structures of cestode infrapopulations. It is likely that younger worms contain lower metal levels than older worms due to a shorter exposure period. Thus, it is necessary to standardize the sampling of worms which should be used for indication purposes. Due to a lack of adequate sentinel species in terrestrial habitats more studies are required to validate and standardize the use of helminths as accumulation bioindicators in order to obtain mean values with low standard deviations. The host–parasite system rat–H. diminuta appears to be a useful and promising bioindication system at least for lead in urban ecosystems as rats as well as the tapeworm are globally distributed and easily accessible.

1. The oxidation-reduction potential in cultures of E. histolytica has been studied. It was found that a close relation exists between the potential in the culture and the growth, encystation, and excystation of E. histolytica. The small differences observed in different cultures indicate the reproducibility of the potentials and the reliability of the potential condition in explaining these biological activities of the amoebae in culture.

2. The best growth of trophozoites was observed at potentials between −350 and −425mV., less at potentials between −275 and −350mV., still less at between −200 and −275mV. At potentials between −150 and −200mV. a bare increase in number of trophozoites was noticed. Between potentials of −50 and −150mV. no increase of growth was observed. Trophozoites were found dead in 12 hr. or more at potentials between −50 and +50mV., and died and disintegrated in a couple of hours between potentials of +100 and +200mV.

3. The life span of a culture of E. histolytica was also found to be related to the potential condition. The longer the potential in the culture remains below −150mV., the longer the culture remains positive.

4. Excystation of E. histolytica, no matter in what media, took place only at potentials of −115mV. or lower.

5. Mass encystation of E. histolytica was induced in cultures in which a ‘sharp rise of potential’ occurred after a greatly increased rate of multiplication of trophozoites after 22–24 hr. of incubation. Maturation of cysts occurred during this period of ‘sharp rise of potentials’. If the potential went down shortly after its sharp rise, the cysts failed to become mature and disappeared in about 12 hr.

6. Trophozoites and cysts observed in cultures with very low potentials (below −300mV.) and a rapid multiplication were definitely smaller than those in cultures having higher potentials and trophozoites multiplied slowly.

7. In cultures of amoebae in which mass encystation failed to occur, or mass encystation occurred but cysts failed to become mature, some success was observed in a few trials by artificially creating the ‘sharp rise of potential’ by oxygenation.

8. The pH values noticed in cultures at times of encystation ranged from 6.4 to 6.8. This pH range was a little lower than that observed previously. Mass encystation failed to occur at the change in potential if the pH was 7.2 or higher.

9. It is felt that the process of encystation requires, at least, two extrinsic and one intrinsic factors. The first two are the potential change from more favourable to less favourable conditions and the pH. The last one is the tendency to encyst possessed by the amoebae.

10. The low potential condition in a culture of E. histolytica was found chiefly provided by the activity of the accompanying bacteria. It is, therefore, felt that the indispensability of a bacterial flora for cultivation of amoebae may be explained, partly if not entirely, by the potential relation. To verify this statement, it is hoped to propagate E. histolytica in cultures in which a strongly reducing condition is provided without the presence of bacteria.

The author wishes to acknowledge the kindness of Dr David Weinman of this department in making many invaluable corrections of this manuscript, and he is very grateful to Mrs Elizabeth B. Keller and Mrs Wanda Reed for their help in preparing the graphs accompanying it.

The characterization of four Trypanosoma vivax isolates from Colombia in South America showed that although minor phenotypic differences existed between them, these parasites are antigenically related and belong to a single serodeme. Characterization by isoenzyme assay, karyotyping and DNA probe analysis, showed the Colombian isolates to be more similar to the West African than to Kenyan T. vivax. There was, however, little serological cross-reactivity between South American and African groups of T. vivax. Although the T. vivax isolates from Colombia were pathogenic for dairy calves which showed the typical sign of progressive emaciation, these parasites failed to infect mice or tsetseand could not be cultivated as bloodstream forms in vitro.This study represents initial attempts to establish the phenotypic and serological diversity amongst T. vivax isolates from South America.

Great confusion prevails in literature with regard to the various species of nematode worms inhabiting the air-passages and blood-vessels of whales, porpoises and dolphins. These worms form a group analogous, and, as we believe, very closely related to the genera Metastrongylus, Dictyocaulus, Synthetocaulus, and Haemostrongylus, which occur in similar situations in terrestrial mammals. The genera named are referred to the family Meta-strongylidae Leiper (1908), as restricted by the exclusion of the forms now included in the family Trichostrongylidae Leiper (1912). The forms found in Cetacea, of which the typical genus is Pseudalius, have been ranked first as a subfamily Pseudaliinae of “Strongylidae” by Railliet and Henry (1909) and later as a family Pseudaliidae of Strongyloidea by Railliet (1916).

(a) Glossina morsitans

1. A method of maintaining a breeding colony is described. The flies were best kept singly in tubes.

2. The optimum temperature and humidity ranges were 74–80° F. and 60–75% R.H., respectively. Young flies failed to tolerate a lower minimum temperature.

3. A light intensity of at least one foot-candle was needed at the feeding site.

4. The method of feeding the flies was of prime importance. Best results were obtained by offering food every fourth day, at a temperature of 80–81° F. The best feeding animal was sheep, but guinea-pig was useful for inducing newly emerged flies to feed. The condition of the skin at the feeding site was important, and it is suggested that frequently changing the feeding animal will lead to better feeding.

5. Female flies lived longer than male flies, and in both sexes the highest mortality was during the first 20 days of life.

6. The optimum age for mating was 10–14 days for males and 3–4 days for females; 90–100% of the first and second generation females were fully inseminated.

7. Each generation was less virile than the preceding one. Pupa production was decreased and the abortion rate increased from each generation to the next. Pupal viability, however, remained constant throughout all generations but the mean pupal weight showed a progressive decrease, except for the pupae from the second and third generation flies.

8. The mean interval without food during an interlarval period did not affect the duration of the period.

9. Feeding on the day of parturition did not significantly affect the length of the succeeding interlarval period.

10. The duration of an interlarval period was directly correlated with the length of the maximum interval without food during the period.

(b) Glossina austeni

11. A colony was maintained in a manner similar to that used for G. morsitans, but best results were obtained at 80–85° F. and 77–82% R.H.

12. Feeding was more satisfactory than in G. morsitans.

13. In longevity and reproduction the flies were superior to G. morsitans.

The resurgence of pertussis in some countries that maintain high vaccination coverage has drawn attention to gaps in our understanding of the epidemiological effects of pertussis vaccines. In particular, major questions surround the nature, degree and durability of vaccine protection. To address these questions, we used mechanistic transmission models to examine regional time series incidence data from Italy in the period immediately following the introduction of acellular pertussis (aP) vaccine. Our results concur with recent animal-challenge experiments wherein infections in aP-vaccinated individuals proved as transmissible as those in naive individuals but much less symptomatic. On the other hand, the data provide evidence for vaccine-driven reduction in susceptibility, which we quantify via a synthetic measure of vaccine impact. As to the precise nature of vaccine failure, the data do not allow us to distinguish between leakiness and waning of vaccine immunity, or some combination of these. Across the range of well-supported models, the nature and duration of vaccine protection, the age profile of incidence and the range of projected epidemiological futures differ substantially, underscoring the importance of the remaining unknowns. We identify key data gaps: sources of data that can supply the information needed to eliminate these remaining uncertainties.

A multidisciplinary approach has been applied to examine the population structure of sardine Sardinops sagax off South Africa, where this species supports significant fisheries and is also of ecological and eco-tourism importance. Observations of discontinuous sardine distribution patterns, discrete spawning grounds and significant spatial differences in a variety of phenotypic characteristics have suggested the existence of discrete western, southern and eastern sardine sub-populations or stocks. The use of parasites as biological tags to elucidate sardine population structure has recently been investigated, and strong spatial gradients around South Africa in the prevalence, mean infection intensity and mean abundance of a digenean ‘tetracotyle’ type metacercarial endoparasite considered to be of the genus Cardiocephaloides and found in the humours of fish eyes support and have proved particularly convincing evidence for the sardine multiple stock hypothesis. A discontinuous distribution in the occurrence of another parasite, the coccidean Eimeria sardinae found in fish testes, has provided additional but weaker evidence of discrete stocks. These results have contributed to a changed understanding of the population structure of South African sardine and have significant implications for management of the fisheries for this species.

Naturally occurring immunoglobulin M antibodies to Toxoplasma gondii in human sera were examined for their ability to enhance toxoplasmacidal activities of human neutrophils to show a role of natural antibodies in immunity to the early stage of Toxoplasma infection in humans. Neutrophils were mixed with tachyzoites at a ratio of 1:5 in the presence or absence of antibodies and were cultured for 1–18 h for microscopical examination. The count of tachyzoites phagocytosed in 200 neutrophils within 1 h was significantly higher in the presence of sera with natural IgM antibody levels of > 0.8 than those of < 0.1, with 2.4- to 2.9-fold differences (P < 0.02). The total tachyzoite counts at 18 h decreased to 26–39% of those at 1 h in the presence of natural IgM antibody levels of > 0.8 (P < 0.01), while the counts at 1 h consistently increased by 18 h in the absence of natural IgM antibodies. These results indicate that relatively high levels of natural IgM antibodies enhanced phagocytic and microbicidal activities of neutrophils against Toxoplasma. The enhancement was dose dependent, and was also weaker than that obtained with the same dilution of sera from individuals with chronic or acute infections. Live and dead tachyzoite counts in infected neutrophils suggested a quicker effect of natural IgM antibodies than IgG antibodies elicited by infection.

The host-parasite relationship is exquisitely specific. In exploiting the host niche, a variety of helminth parasites have been shown to directly manipulate their hosts' immune responses. We assessed the ability of a whole-worm extract of Hymenolepis diminuta to modulate immune cell activation. Immune cells isolated from human blood or rodent spleens were activated with the T cell mitogen, concanavalin A (Con A)±H. diminuta extract and cytokine production (i.e. IL-2, -4, -10, -12) and proliferation assessed by ELISA and [3H]thymidine incorporation 24 and 72 h post-treatment, respectively. Co-treatment with the H. diminuta extract (100 μg protein/ml) virtually abolished Con A-induced immune cell proliferation, which was not due to increased apoptosis. Boiling of the worm extract reduced its anti-proliferative effect and fractionation indicated that a >50 kDa component was predominantly responsible for the inhibition of Con A-induced immune cell proliferation. Cytokine determinations revealed that the H. diminuta extract significantly reduced Con A-stimulated IL-2 and IL-4, but enhanced the production of IFNγ, IL-12 and IL-10. The increased IL-12 was due to an LPS contaminant in the extract and a helminth-derived ‘IL-12’-like peptide that bound in the ELISA and Western blots. In contrast, a H. diminuta–derived factor directly stimulated IL-10 production by murine splenocytes, and contaminating LPS synergistically enhanced the production of IL-10. Thus, H. diminuta has the potential to block stimulated T cell proliferation and, by inhibiting IL-4 and promoting IL-10 production, may bias the immune environment towards one of immunoregulation and away from IL-4 dominated T helper 2 type events.

Chagas disease chemotherapy is based on drugs that exhibit toxic effects and have limited efficacy, such as Benznidazole. Therefore, research into new chemotherapeutic agents from natural sources needs to be exploited. Apis mellifera venom consists of many biologically active molecules and has been reported to exhibit remarkable anti-cancer effects, often promoting an apoptosis-like death phenotype. This study demonstrates that A. mellifera venom can affect the growth, viability and ultrastructure of all Trypanosoma cruzi developmental forms, including intracellular amastigotes, at concentrations 15- to 100-fold lower than those required to cause toxic effects in mammalian cells. The ultrastructural changes induced by the venom in the different developmental forms led us to hypothesize the occurrence of different programmed cell death pathways. Autophagic cell death, characterized by the presence of autophagosomes-like organelles and a strong monodansyl cadaverine labelling, appears to be the main death mechanism in epimastigotes. In contrast, increased TUNEL staining, abnormal nuclear chromatin condensation and kDNA disorganization was observed in venom-treated trypomastigotes, suggesting cell death by an apoptotic mechanism. On the other hand, intracellular amastigotes presented a heterogeneous cell death phenotype profile, where apoptosis-like death seemed to be predominant. Our findings confirm the great potential of A. mellifera venom as a source for the development of new drugs for the treatment of neglected diseases such as Chagas disease.

The taxonomy and phylogenetic relationships of fish trypanosomes are uncertain. A collection of 22 cloned trypanosome isolates from 14 species of European freshwater fish and 1 species of African freshwater fish were examined by molecular phylogenetic analysis. The small subunit ribosomal RNA (ssu rRNA) genes of 8 clones were sequenced and compared with ssu rRNA gene sequences from a wider selection of vertebrate trypanosome isolates by phylogenetic analysis. All trypanosomes from freshwater fish fell in a single clade, subdivided into 3 groups. This clade sits within a larger, robust clade containing trypanosomes from marine fish and various amphibious vertebrates. All 22 trypanosome clones were analysed by random amplification of polymorphic DNA. The resulting dendrogram shows 3 groups, which are congruent with the groups identified in the ssu rRNA gene phylogeny. Two of the groups contain the majority of trypanosome isolates and within-group variation is slight. These groups do not separate purported trypanosome species distinguished by morphology or host origin, and thus these criteria do not appear to be reliable guides to genetic relationships among fish trypanosomes. However, we suggest that the 2 groups themselves may represent different species of fish trypanosomes. The polymorphic DNA markers we have identified will facilitate future comparisons of the biology of these 2 groups of fish trypanosomes.