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PubMed2006

Life without GAG: the BARE-2 retrotransposon as a parasite's parasite.

A large proportion of the plant LTR (Long Terminal Repeat) retrotransposons are partly or completely unable to synthesize their own machinery for transposition. However, most of these inactive or non-autonomous elements are likely able to retrotranspose, based on their insertional polymorphism. Therefore, they must be parasitic on one or more active partners. Here, we describe the parasitism of the chimeric BARE-2 element on the active BARE-1 (Barley RetroElement-2 and -1 respectively). These two elements are present in the Triticeae and related species, and are together polymorphic among closely related accessions. BARE-2 elements are unable to synthesize their own GAG protein, and harbor a specific ATG deletion in the gag ORF. However, BARE-2 sequences are conserved with BARE-1 in the PBS (Primer Binding Site), PSI (Packaging SIgnal) and DIS (DImerization Signal) domains. As these motifs have been shown to allow parasitism among the lentiviruses, we conclude that BARE-2 is probably a partial parasite of the BARE-1 element because the machinery of the latter can complement the defective GAG of the former. This example emphasizes that we must characterize the parasitic network of LTR retrotransposons and its implication for integration of autonomous, inactive, and non-autonomous elements in order to understand current and past host genome evolution.

Base Sequence↗
PubMed1999

Parasitization of Lacanobia oleracea (Lepidoptera: Noctuidae) by the ectoparasitc wasp, Eulophus pennicornis. Effects of parasitization, venom and starvation on host haemocytes.

In contrast to the situation with endoparasitic wasps, little is known about the effects of ectoparasitoids and their secretions on the haemocytes of their insect hosts. To address this deficit, a study has been made of the ectoparasitic wasp, Eulophus pennicornis, and it's host, the tomato moth, Lacanobia oleracea. Using light microscopy, it was determined that L. oleracea has five main haemocyte types, namely, plasmatocytes, granular cells, spherule cells, oenocytoids and pro-haemocytes, representing 56%, 30%, 10%, 2% and 2% of the population, respectively. Parasitization by E. pennicornis, resulted in an increase in the number of circulating haemocytes up to day three, followed by a decrease towards day eight; the latter being associated with changes to the morphology and viability of the cells. For example, on day five after parasitization, plasmatocytes and granular cells had become more rounded and put out pseudopods less readily compared with those from non-parasitized controls, whilst from day seven onwards there was a significant decrease in haemocyte viability and by day nine, extensive haemocyte damage and disintegration was evident. These changes were not observed when larvae were injected with E. pennicornis venom, or when haemocytes were exposed directly to venom in vitro, neither did they occur in starved larvae. Thus, although the observed effects on L. oleracea haemocytes are definitely associated with parasitization they are not due to wasp venom components, nor are they a non-specific effect resulting from nutritional deprivation. The possibility that the feeding wasp larvae produce factors which perturb host haemocytes in order to help condition the host to ensure that successful parasitization occurs, is discussed.

Journal Article↗
PubMed2001

Parasites that cause problems in Malaysia: soil-transmitted helminths and malaria parasites.

Malaysia is a developing country with a range of parasitic infections. Indeed, soil-transmitted helminths and malaria parasites continue to have a significant impact on public health in Malaysia. In this article, the prevalence and distribution of these parasites, the problems associated with parasitic infections, the control measures taken to deal with these parasites and implications for the future will be discussed.

Helminthiasis↗
PubMed2002

Comparative population structure and genetic diversity of Arceuthobium americanum (Viscaceae) and its Pinus host species: insight into host-parasite evolution in parasitic angiosperms.

In a recent study we revealed that the parasitic angiosperm Arceuthobium americanum is comprised of three distinct genetic races, each associated with a different host in regions of allopatry. In order to assess the role of host identity and geographical isolation on race formation in A. americanum, we compared the genetic population structure of this parasite with that of its three principal hosts, Pinus banksiana, Pinus contorta var. latifolia and Pinus contorta var. murrayana. Despite the fact that A. americanum was divided into three genetic races, hosts were divided into only two genetic groups: (i) Pinus banksiana and hybrids, and (ii) P. contorta var. latifolia and var. murrayana. These findings suggest that factors such as geographical isolation and adaptation to different environmental conditions are important for race formation in the absence of host-driven selection pressures. To assess factors impacting population structure at the fine-scale, genetic and geographical distance matrices of host and parasite were compared within A. americanum races. The lack of a relationship between genetic and geographical distance matrices suggests that isolation-by-distance plays a negligible role at this level. The effect of geographical isolation may have been diminished because of the influence of factors such as random seed dispersal by animal vectors or adaptation to nongeographically patterned environmental conditions. Host-parasite interactions might also have impacted the fine-scale structure of A. americanum because the parasite and host were found to have similar patterns of gene flow.

Genetic Variation↗
PubMed2000

Chitinases of the avian malaria parasite Plasmodium gallinaceum, a class of enzymes necessary for parasite invasion of the mosquito midgut.

The Plasmodium ookinete produces chitinolytic activity that allows the parasite to penetrate the chitin-containing peritrophic matrix surrounding the blood meal in the mosquito midgut. Since the peritrophic matrix is a physical barrier that the parasite must cross to invade the mosquito, and the presence of allosamidin, a chitinase inhibitor, in a blood meal prevents the parasite from invading the midgut epithelium, chitinases (3.2.1.14) are potential targets of malaria parasite transmission-blocking interventions. We have purified a chitinase of the avian malaria parasite Plasmodium gallinaceum and cloned the gene, PgCHT1, encoding it. PgCHT1 encodes catalytic and substrate-binding sites characteristic of family 18 glycohydrolases. Expressed in Escherichia coli strain AD494 (DE3), recombinant PgCHT1 was found to hydrolyze polymeric chitin, native chitin oligosaccharides, and 4-methylumbelliferone derivatives of chitin oligosaccharides. Allosamidin inhibited recombinant PgCHT1 with an IC(50) of 7 microM and differentially inhibited two chromatographically separable P. gallinaceum ookinete-produced chitinase activities with IC(50) values of 7 and 12 microM, respectively. These two chitinase activities also had different pH activity profiles. These data suggest that the P. gallinaceum ookinete uses products of more than one chitinase gene to initiate mosquito midgut invasion.

Amino Acid Sequence↗
PubMed1998

Recombinant Mycobacterium bovis bacillus Calmette-Guérin secreting merozoite surface protein 1 (MSP1) induces protection against rodent malaria parasite infection depending on MSP1-stimulated interferon gamma and parasite-specific antibodies.

The merozoite surface protein 1 (MSP1) has emerged as a leading malaria vaccine candidate at the erythrocytic stage. Recombinant bacillus Calmette-Guérin (rBCG), which expressed a COOH-terminal 15-kD fragment of MSP1 of Plasmodium yoelii (MSP1-15) as a fusion protein with a secretory protein of Mycobacterium kansasii, was constructed. Immunization of mice with this rBCG induced a higher degree of protection against blood-stage parasite infection than with recombinant MSP1-15 in the RIBI adjuvant (RIBI ImmunoChem Research, Inc., Hamilton, MT) or incomplete Freund's adjuvant systems. We studied the mechanism of protection induced by MSP1-15, and found that interferon (IFN)-gamma had a major role in protection in all adjuvant systems we examined. Mice that produced low amounts of MSP1-15 stimulated IFN-gamma and could not control parasite infection. The antibody against MSP1-15 did not play a major role in protection in this system. After parasite infection, immunoglobulin G2a antibodies, which had been produced by IFN-gamma stimulation, were induced and subsequently played an important role in eradicating parasites. Thus, both cellular and humoral immune responses were essential for protection from malaria disease. These data revealed that BCG is a powerful adjuvant to induce such a protective immune response against malaria parasites.

Adjuvants, Immunologic↗
PubMedDate not supplied

Parasite diversity in an endemic region for avian malaria and identification of a parasite causing penguin mortality.

Understanding the population structure of Plasmodium parasites is essential for malaria intervention. A survey of parasites in vectors and host infections was conducted in an area of intense mortality due to malaria in a captive penguin (Spheniscus demersus) colony, using a novel method for identification of Plasmodium species by amplification of ribosomal sequences in DNA or RNA. Three phylogenetically distinct groups of avian Plasmodium were detected in mosquitoes (Culex) collected at the study site (Baltimore Zoo, Baltimore, MD) during a period of high transmission. One of the three clades of Plasmodium was found to be prevalent in penguins monitored through the malaria transmission season and consistent with morphological identification as Plasmodium relictum. This parasite sequence was directly associated with the death of a penguin. Thus, a complete transmission cycle is defined at this site. Phylogenetic comparison of ribosomal sequences to an authenticated reference strain of Plasmodium relictum indicates that this is not the parasite causing death in the penguins, suggesting that different parasites may be morphologically indistinguishable.

Animals↗
PubMed1975

[Glutathionestatus of Plasmodium vinckei parasitized erythrocytes in correlation to the intraerythrocytic development of the parasite (author's transl)].

The glutathione status of Plasmodium vinckei parasitized erythrocytes of mice was determined in correlation to the intraerythrocytic stage of maturation of the parasite. The different stages of blood schizogony were separated by discontinuous Dextran-density-centrifugation. The changes of protein content, glutathione concentration (reduced/oxidized and bound/free glutathione) and in the specific activities of the following enzymes: gamma-glutamyl-cysteine-synthetase (GC-synthetase), glutathione-reductase (GR), glucose-6-phosphate dehydrogenase (Gl-DH), glutathione-peroxydase (G-POD) and catalase were investigated in dependence of the intraerythrocytic stage of development. The following changes of the investigated metabolic parameters were observed during the schizogony: - the protein content decreased to about one half, - the glutathione concentration increased about 10-fold, while the relations reduced/oxidized and free/bound glutathione remained constant, - Gl-DH activity appeared and increased steeply, - the specific activities of GC-synthetase and of GR increased more than 2-fold, while G-POD remained almost constant, - and the activities of G-6-PDH and catalase showed a significant, strong decrease to about 25% of the original values. It is tried to relate the observed changes to the growing parasite or to the host cell. The significance of the results for the metabolism of malaria parasites and for a possible adaptation to the mosquito by a GSH mediated protection of the malaria parasite against an enzymatic defence-reaction of the mosquito, is discussed.

Animals↗
PubMedDate not supplied

[The taxonomic diversity of the parasites of agnathans and fishes in the Volga basin. I. Parasitic protozoa (Protozoa)].

A checklist of protozoa parasitizing fishes in the Volga basin is given. The checklist includes host species names for the each parasite and data on the occurrence of parasites in different parts of the Volga basin. The data on parasitic protozoa from 52 fish species are presented. The list containes 224 species and 10 subspecies names of the parasites. 9 species (Trypanosoma gracilis, Eimeria cheni, E. sinensis, Zschokkella striata, Chloromyxum cyprini, Myxobolus amurensis, M. driagini, M. pavlovskii, and Balantidium ctenopharyngodoni) were introduced into the Volga basin from the Amur basin along with acclimatizated fishes.

Animals↗
PubMed1987

The bovine autologous Theileria mixed leucocyte reaction: influence of monocytes and phenotype of the parasitized stimulator cell on proliferation and parasite specificity.

In the autologous Theileria mixed leucocyte reaction (MLR), irradiated Theileria parva-infected cells induce proliferative responses in autologous peripheral blood mononuclear leucocytes (PBM), irrespective of the immune status of the donor animal. In this paper we have analysed the cellular basis of this response in naive and immune cattle to determine the Theileria specificity of the response. The magnitude of proliferation is dependent on two parameters, namely the presence or absence of monocytes in the responder population, and the phenotype of the parasitized stimulator cells, both of which appeared to be independent of the immune status of the donor animal. Monocyte-depleted responders invariably gave stronger proliferative responses but generated cytotoxicity from immune cattle that tended to be less genetically restricted. Marked differences were observed in the stimulatory capacity of cloned parasitized T-cell and non-T cell lines. At least part of this variation was associated with differences in the capacity of the parasitized cells to secrete soluble suppressive factors and possibly also stimulatory factors. Two observations indicated that, in immune cattle, part of the proliferative response in the autologous Theileria MLR is parasite-specific. First, stimulator cells fixed with glutaraldehyde stimulated proliferative responses in monocyte depleted PBM from immune animals but not naive animals. Second, in autologous Theileria MLRs with intact PBM, genetically restricted cytotoxic cells were generated from immune but not naive animals. While monocytes seem not to be required for induction of the parasite-specific component of the response, their absence from the assay when viable stimulator cells are utilized appears to enhance the non-specific component of the proliferative and cytotoxic responses.

Animals↗
PubMed2006

Prevalences of gastrointestinal parasites in sheep and parasite-control practices in NW Spain.

A coprological survey to know the presence of gastro-intestinal nematode parasites infecting sheep was done in Galicia (NW Spain), an area with Atlantic climate where sheep production is replacing cattle due to the Agricultural Community Politics of the European Union. From September 2001 to November 2002, 1710 faecal samples were randomly collected from 49 sheep farms and examined by using the flotation technique to determine the prevalence of gastro-intestinal nematode parasites. The sheep-level prevalence was 100%, and the genera identified were Chabertia, Cooperia, Haemonchus, Nematodirus, Oesophagostomum, Teladorsagia, Trichostrongylus and Trichuris spp. A questionnaire was distributed to the farmers (at the same time as sampling) about parasite-control practices during the year before sampling (2000). Ninety percent (95% CI 81%, 98%) of the farmers said they used antiparasitic drugs occasionally, but none of them asked for a coprological analysis prior to the treatment and the efficacy of the drugs was never evaluated. A higher median EPG was observed in the treated sheep (163) than in the untreated ones (26). Chemotherapy was the only parasite-control practice. Flocks that treated according to the farmer's previous experience had higher median EPG (236) than other flocks (185 following the prescription of their veterinary clinician and 232 based on the commercial agent's counsel). Typically, one benzimidazole-treatment per year was applied in autumn and non-veterinary counsel was used. Sheep treated with imidotiazoles had lower EPG (144) than other drugs (164 for the benzimidazoles and 166 for the macrocyclic lactones). We found a higher median EPG in the sheep receiving two treatments/year (175) than in those treated only once per year (156). These results suggest lack of knowledge about worm-control strategies and anthelmintic use or unwillingness to apply such knowledge.

Animals↗
PubMed2005

Sushi delights and parasites: the risk of fishborne and foodborne parasitic zoonoses in Asia.

Because of the worldwide popularization of Japanese cuisine, the traditional Japanese fish dishes sushi and sashimi that are served in Japanese restaurants and sushi bars have been suspected of causing fishborne parasitic zoonoses, especially anisakiasis. In addition, an array of freshwater and brackish-water fish and wild animal meats, which are important sources of infection with zoonotic parasites, are served as sushi and sashimi in rural areas of Japan. Such fishborne and foodborne parasitic zoonoses are also endemic in many Asian countries that have related traditional cooking styles. Despite the recent increase in the number of travelers to areas where these zoonoses are endemic, travelers and even infectious disease specialists are unaware of the risk of infection associated with eating exotic ethnic dishes. The aim of this review is to provide practical background information regarding representative fishborne and foodborne parasitic zoonoses endemic in Asian countries.

Animals↗
PubMed1980

Parasite-parasite interaction of Salmonella typhimurium and Schistosoma.

The parasite-parasite interaction of Salmonella and Schistosoma was studied. Salmonella typhimurium LT2 was found to associate in vitro with three human species of Schistosoma: Schistosoma mansoni, Schistosoma haematobium, and Schistosoma japonicum. Genetic mutants of S. typhimurium were allowed to interact with ligatured and unligatured worms of S. mansoni in vitro. These studies were undertaken to elucidate the mechanism(s) of the parasite-parasite interaction of Salmonella on the surface of Schistosoma. The ga/E and fla mutants showed 100% association with male schistosomes, but a reduced interaction with female worms. The rough A and pili mutants showed a significant reduction in the ability to associate with both male and female S. mansoni. Observations with the scanning electron microscope revealed that pili function in adhesion of Salmonella to the surface tegument of S. mansoni and S. haematobium. The association of Salmonella and Schistosoma may contribute to persistence of salmonella infection.

Animals↗
PubMed1992

[Natural parasitism of buffaloes in Botucatu, SP, Brazil. III. Dynamics of gastrointestinal parasitism in cows and their calves].

Gastrointestinal parasitism of 24 buffalo cows before parturition, and post-parturition, their infection and that of their respective calves during the following 30 weeks were studied. Willis, Hoffmann and whenever possible, the modified Gordon & Whitlock techniques were used for fecal examinations. Toxocara vitulorum eggs were the earliest forms encountered in calves feces, as follows: during the 1st week after birth, 58.33% of the calves were positive, and in the 4th week, 100% of these animals were positive. Eggs of Strongyloides sp were in the 1st week after birth in two of the calves and in the 5th week, all for them were positive. The next parasites to appear were the Coccidia of which oocysts were detected in the feces of two calves in the 2nd week after birth, and 58.33% of the calves were positive for these in the 3rd week, and in the 6th week, all calves shed oocysts in their feces. On the other hand, eggs of Strongyloides were the last forms to appear in calves feces. However, despite their sporadic appearance in the feces, eggs of these parasites were observed continuously from the 11th week onwards, and at this point, the percentage of positive samples began to increase to reach its peak. Relatively to adult animals, eggs of T. vitulorum were observed in the feces of 11 cows, one or twice at most; eggs of Strongyloides sp were seen only once in the feces of four buffalo cows and eggs of Strongyloides in 21 out of 24 cows. Oocysts of Coccidia were observed in 16 cows. Mechanisms of infestation of calves with these parasites are discussed.

Animals↗
PubMed1991

Animal models in the study of the phenomenon of parasitism: filariae and other parasites.

The Round table has emphasized the absolute necessity of in vivo research showing the complexity of host reaction to the parasite. The results obtained in vitro can only provide a preliminary indication, because any interference with the culture is susceptible of changing the precarious balance of the parasite in that artificial environment. The subject proposed here cannot be treated wholly, but some particular topics could be discussed: 1--searching for appropriate models; 2--parasite strains; 3--some aspects on pathology and drug development; 4--vaccines; what significance in a natural host-parasite relationship can be gathered from a non-natural one?

Animals↗
PubMed2007

Insight into the host-parasite interplay by proteomic study of host proteins copurified with the human parasite, Schistosoma japonicum.

The tegument proteins of schistosome have attracted the most attention in studies of host-parasite interplay, while the host proteins acting at the host-parasite interface remained largely elusive. Here, we undertook a high-throughput proteomic approach to characterize the schistosome-adsorbed host proteins. Fifty five distinct host proteins were confidently identified in S. japonicum samples, including cercaria, schistosomula, adults, eggs, and miracidia, together with tegument and eggshell preparations, of which 23 and 38 host proteins were identified in adult worms and eggs, respectively. Among the schistosome-adsorbed host proteins, host neutrophil elastases were found in the granuloma initiated by schistosome egg deposition, implying that the host innate immune molecules could participate in the granuloma formation for fighting against schistosome invasion, except for the adaptive immune system. In addition, some host proteins, such as proteinase inhibitor and superoxide dismutase, might be utilized by schistosome to counteract or attenuate the host attacks. These parasite-adsorbed host proteins will provide new insights into the host immune responses against schistosome infection, the evasive behavior of the adult worms, and the granuloma formation, which could render an in-depth understanding for the host-parasite interplay.

Animals↗
PubMed2007

Increased genetic diversity as a defence against parasites is undermined by social parasites: Microdon mutabilis hoverflies infesting Formica lemani ant colonies.

Genetic diversity can benefit social insects by providing variability in immune defences against parasites and pathogens. However, social parasites of ants infest colonies and not individuals, and for them a different relationship between genetic diversity and resistance may exist. Here, we investigate the genetic variation, assessed using up to 12 microsatellite loci, of workers in 91 Formica lemani colonies in relation to their infestation by the specialist social parasite Microdon mutabilis. At the main study site, workers in infested colonies exhibited lower relatedness and higher estimated queen numbers, on average, than uninfested ones. Additionally, estimated queen numbers were negatively correlated with estimated average numbers of mates per queen within infested colonies. At another site, infested colonies also exhibited significantly lower worker relatedness, and estimated queen numbers were comparable in trend. In contrast, in two populations of F. lemani where M. mutabilis was absent, relatedness within colonies was high (40 and 90% with R>0.6). While high genetic variation can benefit social insects by increasing their resistance to pathogens, there may be a cost in the increased likelihood of infiltration by social parasites owing to greater variation in nestmate recognition cues. This study provides the first empirical test of this hypothesis.

Animals↗
PubMed1981

Energy metabolisms of parasitic helminths: adaptations to parasitism.

Many metazoans, and particularly the parasitic forms, have adapted well to their environments. This is particularly obvious in organisms that reside in anoxic surroundings, such as the large lumen-dwelling intestinal parasites. However, anaerobic energy metabolisms are not confined to parasites in microaerophilic environments. Some that reside in highly aerobic surroundings (e.g. blood or lungs) also have lost much or all of their aerobic capabilities for energy generation. Adaptations toward anaerobiosis are many and varied: homolactate fermentation (schistosomes and filarial worms), heterolacate fermentations (H. diminuta), and succinate and heterosuccinate fermentations (Ascaris). Even helminths that are obligate aerobes are not complete oxidizers. All accumulate aerobic fermentation products, indicating at best a limited terminal respiration. Some worms, particularly some of the larval stages, retain their ability to survive anaerobically but require the presence of oxygen for motility. Regardless of the type of oxygen requirement, all parasitic helminths examined are dramatically different from their mammalian hosts in regard to their energy metabolisms. Many similar adaptations have been shown to occur in nonparasitic organisms ranging from metazoans, through fish and mammals. There is much room for additional studies of these biochemical adaptations.

Adaptation, Physiological↗