The genitalia of the Pupipara are markedly modified from those of other higher Cyclorrhapha and the nomenclature used is mainly descriptive and controversial; different terminologies have been used by the various authors.

Sera from rabbits vaccinated with irradiated cercariae mediated cell (P388D1 or mouse peritoneal macrophage) adherence to lung-stage schistosomula (LS) but such antibody-mediated cell adherence was short-lived in contrast to cell adherence to mechanically transformed schistosomula (MS). Thus LS lost 50% of their adherent cells within 3–6 h in culture and up to 90% by 24 h, whereas adherence to MS was undiminished during this time. Rapid loss of adherent cells was unique to schistosomula that had developed to the lung stage because schistosomula recovered from the skin up to 3 days post-infection did not exhibit the rapid cell loss shown by 3-day LS. To determine whether cell loss was caused by loss of surface antigenicity during culture LS were cultured on their own for up to 24 h and at various intervals samples of schistosomula were tested for antigenicity by addition of immune serum and cells. Levels of adherence to both MS and LS were maintained throughout the incubation period. When antibody-opsonized schistosomula were washed and indicator cells added at progressive intervals, persistence of adherence was again demonstrated, showing that antibody binding to LS had not promoted surface antigen loss or degradation of bound antibody. It was then shown, by adding fresh macrophages to cultures up to 24 h old that LS which had lost their adherent cells nevertheless retained bound antibody, and comparison of adherence of ‘used’ and ‘fresh’ cells to MS and LS showed that the cytoadherence properties of macrophages were not significantly reduced during their culture with LS from which cells had been lost. Cell loss was shown to be dependent upon protein synthesis by LS since cell loss was significantly reduced when the schistosomula were pre-incubated in puromycin or actinomycin D. Transient cell adherence to LS may comprise an important immune evasion stratagem by schistosomula.

Signal transduction molecules play key roles in the regulation of developmental processes, such as morphogenesis, organogenesis and cell differentiation in all organisms. They are organized into ‘pathways’ that represent a coordinated network of cell-surface receptors and intracellular molecules, being involved in sensing environmental stimuli and transducing signals to regulate or modulate cellular processes, such as gene expression and cytoskeletal dynamics. A particularly important group of molecules implicated in the regulation of the cytoskeleton for the establishment and maintenance of cell polarity is the PAR proteins (derived from partition defective in asymmetric cell division). The present article reviews salient aspects of PAR proteins involved in the early embryonic development and morphogenesis of the free-living nematode Caenorhabditis elegans and some other organisms, with an emphasis on the molecule PAR-1. Recent advances in the knowledge and understanding of PAR-1 homologues from the economically important parasitic nematode, Haemonchus contortus, of small ruminants is summarized and discussed in the context of exploring avenues for future research in this area for parasitic nematodes.

The amounts of acetylcholinesterase (AChE) in homogenates of infective-stage larvae of strains, from different countries, of Haemonchus contortus, Ostertagia circumcincta and Trichostrongylus colubriformis resistant or susceptible to benzi-midazole (BZ) anthelmintics, were compared using a rapid colorimetric assay. The levels of AChE were much greater in those strains which were BZ-resistant than in BZ-susceptible populations. The larvae of susceptible and resistant H. contortus contained less AChE than did the larvae of the other two species. One-way analysis of variance showed that the observed differences between susceptible and resistant strains were significant in each of the species studied. It is suggested that the extra enzyme may act as an anthelmintic-detoxifying enzyme, may inactivate the active site of the anthelmintic or may prevent binding of the anthelmintic to its receptor

Species of the genus Pennella are of interest because they parasitize widely different hosts such as cetacea, flying fish, pipe fishes, sword fishes, etc. In 1917 Wilson listed fourteen valid species and nine more have been added since. Of these P. exocoeti (Holten) and P. blainvilli (Le Sueur) have been recorded as parasites of flying fishes, the former probably in Exocoetus speculiger from which Leigh-Sharpe (1928) and Deboutteville & Nunes-Ruivote (1954) recorded the species, while the latter was found on E. volitans. The present paper deals with four parasites collected from four different species of flying fishes of Madras. The types will be deposited in the Indian museum, Calcutta.

A high degree of intra- and inter-geographical variation has been demonstrated previously in the excretory/secretory proteinases released by adult Haemonchus contortus. Proteinase activity has also been associated with host-protective ‘hidden’ antigens isolated from the gut of adult H. contortus. If similar geographical strain variation also exists within the gut-associated proteinases, this will have important implications for the development of a globally effective vaccine. The proteinases active in integral-membrane protein extracts from 3 different strains of adult H. contortus were characterized on the basis of their pH optima and molecular size. Although enzyme activity was detected over a wide pH range, the majority of proteinase activity was detected at acidic pH. Differences in specific activity and size of enzymes were observed between the 3 different parasite strains at different pH values. A high degree of conservation in reactive peptides was observed when protein extracts were probed with antisera raised to the protective hidden gut-antigen complexes isolated from the Moredun strain of H. contortus, or to bacterially expressed subcomponents thereof. Therefore, despite the observed differences in membrane-bound proteinase profiles, the similarity of the immunogenic response against these hidden antigens may be sufficient to prove protective against different geographical isolates of H. contortus.

A microsporidian parasite, Nosema eurytremae, was fed to Lymnaea trunculata infected with Fasciola hepatica. Microsporidian infection of the snail was always light, though spores were present in all tissues, but the rediae became heavily infected in the parenchyma. The proportion of infected rediae increased with time and was especially high in ageing infections. Although rediae were only lightly infected when examined before cercarial release began, the infections became progressively heavier, so that towards the end of the life of the snails a high proportion of rediae were totally destroyed and contained no cercariae. Cercarial output was significantly depressed over a long period of active shedding by snails which had been hyperinfected with 1 × 10 6 spores and some of the liberated cercariae were themselves infected.

The male intromittent apparatus of Ergenstrema labrosi and Ligophorus angustus, monogenean parasites of the thick-lipped grey mullet Chelon labrosus, consists of a slender flexible penis tube with an expanded proximal region and whose distal end passes freely through a canal in an accessory sclerite; the tube is surrounded by a sleeve of longitudinal muscle and the apparatus works in a manner generally similar to an engineer's Bowden cable. There is a substantial difference in the form of the accessory sclerite in the two species. In both parasites there is a slender sclerotized vagina which, in L. angustus, is short and straight or curved but in E. labrosi is about 7 times longer and forms a spiral. The special role of the sclerotization of the distal part of the vagina may be to resist perforation of the wall by the exceedingly fine penis tube and the consequent discharge of sperms into the parenchyma.

Adult trematodes belonging to the genus LeucocMoridium Carus are here reported for the first time from North America. These flukes are intestinal parasites of birds and proved to be previously undescribed species.

In the present paper a key separating the species of the genus is given, and the following are described and figured as new species:

Leucochloridium certhiae n. sp. from Certhia familiaris americana;

Leucochloridium mniotiltae n. sp. from Mniotilta varia;

Leucochloridium icteri n. sp. from Icterus galbula;

Leucochloridium vireonis n. sp. from Vireo griseus griseus;

Leucochloridium sorae n. sp. from Porzana Carolina.

Competition between parasite species or genotypes can play an important role in the establishment of parasites in new host populations. Here, we investigate a mechanism by which a rare parasite is unable to establish itself in a host population if a common resident parasite is already present (a ‘priority effect’). We develop a simple epidemiological model and show that a rare parasite genotype is unable to invade if coinfecting parasite genotypes inhibit each other's transmission more than expected from simple resource partitioning. This is because a rare parasite is more likely to be in multiply-infected hosts than the common genotype, and hence more likely to pay the cost of reduced transmission. Experiments competing interfering clones of bacteriophage infecting a bacterium support the model prediction that the clones are unable to invade each other from rare. We briefly discuss the implications of these results for host-parasite ecology and (co)evolution.

1. The development of S. duttoni and S. recurrentis was studied in lice.

2. After penetrating the anterior part of the midgut spirochaetes were seen in the haemocoele, haemocytes, neural ganglia and muscles of lice. They were never seen elsewhere.

3. The haemocytes of infected lice sometimes contained coarse granules believed to be the breakdown products of spirochaetes due to phagocytosis.

Specific glycolipids (GLs) from Leishmania (Viannia) braziliensis promastigotes were isolated and purified. A monoclonal antibody directed to carbohydrate epitopes of these GLs was produced. mAb SST-1 recognizes a low molecular weight GL as established by solid-phase radioimmunoassay and HPTLC immunostaining, and does not cross-react with lipophosphoglycan isolated from L. (V.) braziliensis promastigotes. An indirect immunofluorescence study indicated that the antigenic GLs are present at the L. (V.) braziliensis promastigote surface. SST-1 reacted with promastigotes of L. (V.) naiffi and L. (V.) guyanensis, but not with species in the L. Leishmania subgenus i.e. L. (L.) amazonensis, L. (L.) chagasi, or L. (L.) major. All L. (V.) braziliensis serodemes tested were reactive with SST-1. These results indicate that SST-1 recognizes specific GLs expressed by species of the Viannia subgenus, and will be particularly useful for identification of L. (V.) braziliensis.

Changes in the cardiac β-adrenergic system in early stages of Trypanosoma cruzi infection have been described. Here, we studied an early (135 days post-infection–p.i.) and a late stage (365 days p.i.) of the cardiac chronic form of the experimental infection (Tulahuen or SGO-Z12 strains), determining plasma epinephrine and norepinephrine levels, β-receptor density, affinity and function, cardiac cAMP concentration and phosphodiesterase activity, cardiac contractility, and the presence of β-receptor autoantibodies. Tulahuen-infected mice presented lower epinephrine and norepinephrine levels; lower β-receptor affinity and density; a diminished norepinephrine response and higher cAMP levels in the early stage, and a basal contractility similar to non-infected controls in the early and augmented in the late stage. The Tulahuen strain induced autoantibodies with weak β-receptor interaction. SGO-Z12-infected mice presented lower norepinephrine levels and epinephrine levels that diminished with the evolution of the infection; lower β-receptor affinity and an increased density; unchanged epinephrine and norepinephrine response in the early and a diminished response in the late stage; higher cAMP levels and unchanged basal contractility. The SGO-Z12 isolate induced β-receptor autoantibodies with strong interaction with the β-receptors. None of the antibodies, however, acted a as β-receptor agonist. The present results demonstrate that this system is seriously compromised in the cardiac chronic stage of T. cruzi infection.

Habitat. This marine leech, a member of the Rhyncobdellida, or jawless leeches, is parasitic on the angler, Lophius piscatorius, and, in my experience, attaches itself to the skin of the fish on the ventrolateral surface indiscriminately; it is not found near the vent, as is usually the case with Pontobdella, which occurs frequently attached near the cloaca of the skate.

Periodicity in nematode egg excretion may be of evolutionary origin as it can favour dispersal of the eggs in the environment. We investigated whether egg excretion by Heterakis gallinarum shows a repeatable pattern of periodicity. The faecal egg concentration and total number of eggs excreted within 4-h intervals were significantly affected by the sampling time within 1 day, but remained unaffected by the sampling day or interaction effects. By contrast, the total number of eggs excreted within 24 h did not differ among the 4 days of the study, collectively indicating repeatable egg excretion patterns. Both host feces and parasite egg excretion increased from night to late afternoon, followed by a decrease in the evening, resulting in higher egg excretion during daytime than the dark period. Feces excretion and worm fecundity showed overlapping diurnal rhythms with similarly timed phases, suggesting the existence of synchronicity between the host feces and nematode egg excretion patterns. We conclude that egg excretion by H. gallinarum is synchronized with host feces excretion and is higher during the daytime than during the dark period. This overlaps with the maximum activity of the day-active host and allows a maximal dispersal of the eggs in the environment.

Le nombre des travaux traitant de la concentration moléculaire des sues et tissus des divers animaux est déjà très grand (Fredericq, Sabbattani, Bottazzi, Quinton), pourtant les parasites ont été négligés. C'est pour combler cette lacune, que nous avons entrepris les recherches dont nous donnons ici les premiers résultats. La détermination des concentrations moléculaires a d'abord un intérêt en elle-même, comme détermination de constante physico-chimique. Elle peut, d'autre part, donner d'utiles renseignements pour l'étude des milieux de culture des grands parasites; elle peut aussi indirectement contribuer à l'étude de la spécincité parasitaire ainsi qu'à celle de la nutrition des parasites intestinaux.

A simple in vitro technique was devised to culture chick embryos in Petri dishes from the 4th to the 21st day of incubation. Leucochloridiomorpha constantiae (Trematoda) metacercariae were placed either singly or multiply (5/embryo) on the chorio-allantois of in vitro grown embryos on day 7 and were removed on day 14. Growth and development studies were also made on worms grown singly or multiply (5/chick) in the bursa of Fabricius of the domestic chick. Worms grown singly or multiply in embryos were sexually mature, although eggs from these worms were abnormal when compared with eggs from worms recovered from chicks. The mean body area of worms from chicks was 2–3 times greater than that of worms from embryos. The mean body area of single worms from embryos was significantly larger than that of worms grown multiply in this site. However, the mean body area of multiple worms from the chick was significantly larger than that of single worms from this site. Worm pairs or clusters were seen in all embryos with the multiple infections.

The rhoptry kinase 18 of Toxoplasma gondii (TgROP18) has been identified as a key virulence factor that allows the parasite to escape from host immune defences and promotes its proliferation in host cells. Although much research is focused on the interaction between host cells and TgROP18, the development of monoclonal antibodies (mAbs) against TgROP18 has not been reported till date. To produce mAbs targeting TgROP18, two hybridomas secreting mAbs against TgROP18, designated as A1 and T2, were generated using cell fusion technology. The subtypes of the A1 and T2 mAbs were identified as IgG3 λ and IgM κ, and peptide scanning revealed that the core sequences of the antigenic epitopes were 180LRAQRRRSELVFE192 and 351NYFLLMMRAEADM363, respectively. The T2 mAb specifically reacted with both T. gondii type I and Chinese I, but not with T. gondii type II, Plasmodium falciparum or Schistosoma japonicum. Finally, the sequences of heavy chain and light chain complementarity-determining regions of T2 were amplified, cloned and characterized, making the modification of the mAb feasible in the future. The development of mAbs against TgROP18 would aid the investigation of the molecular mechanisms underlying the modulation of host cellular functions by TgROP18, and in the development of strategies to diagnose and treat Toxoplasmosis.

Superantigens (SAgs) are microbial proteins which have potent effects on the immune system. They are presented by major histocompatibility complex (MHC) class II molecules and interact with a large number of T cells expressing specific T cell receptor Vβ domains. Encounter of a SAg leads initially to the stimulation and subsequently to the clonal deletion of reactive T cells. SAgs are expressed by a wide variety of microorganisms which use them to exploit the immune system to their own advantage. Bacterial SAgs are exotoxins which are linked to several diseases in humans and animals. A classical example is the toxic shock syndrome in which the massive release of cytokines by SAg-reactive cells is thought to play a major pathogenic role. The best characterized viral SAg is encoded by mouse mammary tumour virus (MMTV) and has proved to have a major influence on the viral life cycle by dramatically increasing the efficiency of viral infection. In this paper, we review the general properties of SAgs and discuss the different types of microorganisms which produce these molecules, with a particular emphasis on the role played by the SAg-induced immune response in the course of microbial infections.

Different courses of microsporidiosis, related to the route of infection, were observed in severe combined immunodeficient (SCID) mice inoculated with spores of the human microsporidian Trachipleistophora hominis (Phylum Microspora). After eye contamination by spores the mice became moribund within 7 to 8 weeks, showing severe infection in the conjunctiva and cornea, and lighter infections in the urinary bladder, liver and spleen. The mean survival time of intramuscularly inoculated SCID mice was 12 weeks, when heavy infection was found in muscles around the site of inoculation, and also in several viscera. Subcutaneously inoculated SCID mice developed skin lesions around the inoculation sites, and heavy urinary bladder infection, and died 6 or 7 weeks after inoculation. Intracerebrally inoculated SCID mice became moribund 5 or 6 weeks after inoculation with massive infection in the urinary bladder and liver, but none in the brain. Intraperitoneally inoculated SCID mice survived for 13 weeks and the urinary bladder and liver were the most heavily infected organs. The SCID mice, inoculated perorally and examined after 23 weeks, were uninfected. Infection was not detected in the brain of any of the inoculated SCID mice. Our results show that T. hominis has very little tissue specificity. Peroral infection seems to be ineffective in T. hominis, but eye contamination or insect bite (as mimicked by injection) are suggested as possible routes of infection under natural conditions.