The gastrointestinal parasite of dogs and their related species, <I>Toxocara canis</I>, is a prime example of a zoonotic parasite. It is the principal agent of visceral larva migrans and also a cause of ocular larval migrans. As a result of the close association that dogs have with man, the parasite enjoys a world-wide distribution. Infections can be contracted from contaminated soil and handling of infected dogs, and is particularly prevalent amongst professions that have a close association with dogs, such as hydatid control officers in New Zealand. Once inside the non-canid host, the parasite enters a state of arrested development, in which it neither grows nor differentiates. In this state the parasite releases up to 1% of its body weight in excretory/secretory antigens per day. Assuming that this high protein production was in some way linked to immune evasion, a modest EST project was undertaken using a cDNA library generated from infective larvae. The hypothesis behind this approach was that the high protein output demonstrated by these parasites would be mirrored at the mRNA level. In total 266 clones were sequenced, the majority of which were from the both the 5' and 3' ends of the transcripts. Homologues for these genes were sought by similarity searching against the GenBank protein and the dbEST nucleotide databases. Cluster analysis of the clones identified 129 distinct gene products, all but three of which represented new genes. The majority of the genes (96) were represented by single clones, although 8 transcripts were present at high frequencies, each composing >2% of all the clones sequenced. These high abundance transcripts include a mucin and a novel C-type lectin, which together comprise the two major excretory/secretory antigens released by the parasite. Four highly expressed novel transcripts were found, termed <I>ant</I> genes (abundant novel transcripts). Together these genes represented 18% of all the cDNA clones isolated, but no similar sequences occur in the <I>C. elegans</I> genome. While the coding regions of these genes are dissimilar, they exhibit a remarkable level of similarity in their 3' UTR at the nucleotide level. The discovery of these abundant parasite specific genes, of newly-identified lectins and mucins, as well as a range of conserved and novel proteins, provide defined candidates for future analysis of the molecular basis of immune evasion by <I>Toxocara. </I>

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The acanthocephalan, Acanthocephalus clavula Aujardin, 1845 is an inteatinal. _parasite of freshwater fir-he The iropod, Acellus neridianus Racovitza , is, an, intermediate host. The details of growth and development of A. clavula in A. ceridianue and Cottus robio (L. ) were described from laboratory experimental infection3... The complete life cycle required at least 132 days at 8-13°C; development, in intermediate host took 84 days, and 48, days were required for copulation and maturation in the, definitive, host. Temperature had direct effects on the. growth and development of, _the,. larval-parasite, by increasing the rate of development at, high, temperature (5-19°C). The growth and development of larval parasites in the intermediate host. was affected by crowding. Uniform growth and development were disturbed, if more than 3 ppranites were established in the same isopod.. ;> wz The occurrence of A. clavula in gwyniad, roach, bullhead, eel was affected by a combination of one or more factors of the following: seasonal: iluetuationa, host sex, host length, hont age, feeding habits. The seasonal cycle of A. clavula wan clearly shown in gwyniad, androach4n Bala Lake. The parasites started to establish in late dummer and reached a peak in, Nay and June_in gwyniad and roach respectively, and declined thereafter. until the beginning of Coptember. The incidence of infection in, gwyniad was the same in the aale and female fish for. the, whole year. When the gwyniad data were summed into four 3-monthly periods, the incidence in, male gwyniad had aktendency to be lower than in femalen only during April-June. In roach, the incidence of infection was the same in males and females during April-June, and July-September, and the incidence in male fish was lower than females during October-December, and January-March. The incidence of infection in gwyniad increased with length and age of the fish over the whole year, but when the affect of seasonal fluctuation was minimized, the incidence of infection increased with length of fish. The intensity of infection in male gwyniad was lower :. hsr females from January to October, but much higher in November and December. In roach, the intensity of infection was always lower than 1. A. clavula was able to survive in all regions of the fish intestine, but it was seen that A. clavula established in a particular region of the intestine which was dependent on each host species. In gwyniad, the parasites were established 0-403 from anterior of the intestine; but in eel, the parasite was established 40-100% from anterior of the intestine. The experimental studies showed that superimposed infections occurred in both intermediate and definitive hosts. Overloaded superimposed infections may lead to the discharge of some worms. Host starvation did not cause any apparent discharge of worms from the fish. The shelled acanthors of A. clavula did not hatch in vitro using either wet and dry or applied pressure methods.The in survival times. of, ohelled acanthors and adults of A. clavula, were determined, but the results proved difficult to interpret.

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A conserved acto-myosin motor complex is implicated in parasite motility and host invasion by a wide variety of Apicomplexan zoites. Until recently, only actin, myosin A (MyoA) and its putative light chain (MLC1 in Toxoplasma gondii) or myosin tail domain interacting protein (MTIP) in Plasmodium spp., had been identified as central to the function of this motor. Identification of two further components in T. gondii, the gliding-associated proteins (GAP45 and GAP50), has provided a valuable insight into how the motor may be anchored in the inner membrane complex (IMC) that lies below the plasma membrane. Results presented here demonstrate that Plasmodium falciparum (Pf)GAP45 and PfGAP50 are expressed and co-localise with PfMTIP at the periphery of merozoites. Both GAPs are found to be in complex with PfMyoA, and PfMTIP. Pulse-chase experiments indicate that the motor complex is assembled in two stages. PfGAP50 is incorporated after the formation of a ternary complex comprising PfGAP45, PfMyoA and PfMTIP. PfGAP45 is shown to be N-myristoylated and palmitoylated and may therefore function as a linker protein tethering the motor to the outer leaflet of IMC. Additionally, PfGAP45 is phosphorylated by calmodulin-dependent protein kinase 1 (CDPK1); a process that may be important in the regulation of the motor. Recombinant PfGAP50 is a well-ordered protein, whereas PfGAP45 has a low content of secondary structure. Potential interaction of GAPs with other motor components has been examined. Co-immunoprecipitation experiments, circular dichroism (CD) and fluorescence spectroscopic analyses have not provided any evidence of direct interaction with any other motor proteins.

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No description available.