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Common Parasite (common + parasite)
Selected AbstractsEVIDENCE FOR NEGATIVE FREQUENCY-DEPENDENT SELECTION DURING EXPERIMENTAL COEVOLUTION OF A FRESHWATER SNAIL AND A STERILIZING TREMATODEEVOLUTION, Issue 9 2009Britt Koskella Host,parasite coevolution is often suggested as a mechanism for maintaining genetic diversity, but finding direct evidence has proven difficult. In the present study, we examine the process of coevolution using a freshwater New Zealand snail (Potamopyrgus antipodarum) and its common parasite (the sterilizing trematode, Microphallus sp.) Specifically, we test for changes in genotypic composition of clonal host populations in experimental populations evolving either with or without parasites for six generations. As predicted under the Red Queen model of coevolution, the initially most common host genotype decreased in frequency in the presence, but not the absence, of parasitism. Furthermore, the initially most common host genotype became more susceptible to infection by the coevolving parasite populations over the course of the experiment. These results are consistent with parasite-meditated selection leading to a rare advantage, and they indicate rapid coevolution at the genotypic level between a host and its parasite. [source] The hemoglobins of the trematodes Fasciola hepatica and Paramphistomum epiclitum: A molecular biological, physico-chemical, kinetic, and vaccination studyPROTEIN SCIENCE, Issue 10 2008Sylvia Dewilde Abstract The trematode Fasciola hepatica (Fa.he.) is a common parasite of human and livestock. The hemoglobin (Hb) of Fa.he., a potential immunogen, was chosen for characterization in the search for an effective vaccine. Characterization of trematode Hbs show that they are intracellular single-domain globins with the following remarkable features: (1) Fa.he. expresses two Hb isoforms that differ at two amino acid sites (F1: 119Y/123Q; F2: 119F/123L). Both isoforms are monoacetylated at their N-termini; (2) the genes coding for Fa.he. and Paramphistomum epiclitum (Pa.ep.) Hbs are interrupted by two introns at the conserved positions B12.2 and G7.0.; (3) UV/VIS and resonance Raman spectroscopy identify the recombinant Fa.he. HbF2 as a pentacoordinated high-spin ferrous Hb; (4) electron paramagnetic resonance spectroscopy of cyano-met Fa.he. HbF2 proves that the endogenously bound imidazole has no imidazolate character; (5) the major structural determinants of the globin fold are present, they contain a TyrB10/TyrE7 residue pair on the distal side. Although such distal-site pair is a signature for high oxygen affinity, as shown for Pa.ep. Hb, the oxygen-binding rate parameters for Fa.he. Hb are intermediate between those of myoglobin and those of other trematode Hbs; (6) the three-dimensional structure of recombinant Fa.he. HbF2 from this study closely resembles the three-dimensional structure of Pa.ep. determined earlier. The set of distal-site polar interactions observed in Pa.ep. Hb is matched with small but significant structural adjustments; (7) despite the potential immunogenic character of the fluke Hb, vaccination of calves with recombinant Fa.he. HbF2 failed to promote protection against parasitic infection. [source] The History of Toxoplasma gondii,The First 100 YearsTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 6 2008JITENDER P. DUBEY ABSTRACT. In this paper the history of Toxoplasma gondii and toxoplasmosis is reviewed. This protozoan parasite was first discovered in 1908 and named a year later. Its medical importance remained unknown until 1939 when T. gondii was identified in tissues of a congenitally infected infant, and veterinary importance became known when it was found to cause abortion storms in sheep in 1957. The discovery of a T. gondii specific antibody test, Sabin,Feldman dye test in 1948 led to the recognition that T. gondii is a common parasite of warm-blooded hosts with a worldwide distribution. Its life cycle was not discovered until 1970 when it was found that felids are its definitive host and an environmentally resistant stage (oocyst) is excreted in feces of infected cats. The recent discovery of its common infection in certain marine wildlife (sea otters) indicates contamination of our seas with T. gondii oocysts washed from land. Hygeine remains the best preventive measure because currently there is no vaccine to prevent toxoplasmosis in humans. [source] ADVICE OF THE ROSE: EXPERIMENTAL COEVOLUTION OF A TREMATODE PARASITE AND ITS SNAIL HOSTEVOLUTION, Issue 1 2007Britt Koskella Understanding host-parasite coevolution requires multigenerational studies in which changes in both parasite infectivity and host susceptibility are monitored. We conducted a coevolution experiment that examined six generations of interaction between a freshwater snail (Potamopyrgus antipodarum) and one of its common parasites (the sterilizing trematode, Microphallus sp.). In one treatment (recycled), the parasite was reintroduced into the same population of host snails. In the second treatment (lagged), the host snails received parasites from the recycled treatment, but the addition of these parasites did not begin until the second generation. Hence any parasite-mediated genetic changes of the host in the lagged treatment were expected to be one generation behind those in the recycled treatment. The lagged treatment thus allowed us to test for time lags in parasite adaptation, as predicted by the Red Queen model of host,parasite coevolution. Finally, in the third treatment (control), parasites were not added. The results showed that parasites from the recycled treatment were significantly more infective to snails from the lagged treatment than from the recycled treatment. In addition, the hosts from the recycled treatment diverged from the control hosts with regard to their susceptibility to parasites collected from the field. Taken together, the results are consistent with time lagged, frequency-dependent selection and rapid coevolution between hosts and parasites. [source] Male-biased parasitism by common helminths is not explained by sex differences in body size or spleen mass of breeding cormorants Phalacrocorax auritusJOURNAL OF AVIAN BIOLOGY, Issue 3 2008Stacey A. Robinson In vertebrates, males are often more parasitised than conspecific females. This bias in parasitism might result from sex differences in parasite exposure and/or susceptibility to infection. Such information is important for testing hypotheses about allocation of resources to life histories of males and females and for testing hypotheses about factors thought to influence parasite fitness and parasite dynamics. We tested whether double-crested cormorants Phalacrocorax auritus exhibit male-biased parasitism by gut helminths. The prevalence of nematode Contracaecum spp. and trematode Drepanocaphalus spathans infections was ,90% and 39%, respectively. Cestode, primarily Paradilepis caballeroi and acanthocephalan Andracantha gravida infections were less common (<10%). Male and female cormorants did not differ in prevalence of infection by any helminth species. However, males had twice the abundance and intensity of Contracaecum spp. infections and twice the intensity of D. spathans infections than found in females. For common parasites showing male-biased parasitism, degree of parasitism was also unrelated to body size or mass in either sex. Males and females did not differ in spleen mass and spleen mass was unrelated to abundance of common parasites. Furthermore, abundance of trematodes and nematodes was not correlated. At present, male biases in parasitism by nematodes and trematodes in cormorants are independent patterns that remain unexplained, but are most likely attributable to sex differences in exposure and/or immunological differences not yet assessed. [source] | ||||||||||