Search results for "Parasite"
showing 10 items of 827 documents
Microbial symbionts of parasitoids
2020
Parasitoids depend on other insects for the development of their offspring. Their eggs are laid in or on a host insect that is consumed during juvenile development. Parasitoids harbor a diversity of microbial symbionts including viruses, bacteria, and fungi. In contrast to symbionts of herbivorous and hematophagous insects, parasitoid symbionts do not provide nutrients. Instead, they are involved in parasitoid reproduction, suppression of host immune responses, and manipulation of the behavior of herbivorous hosts. Moreover, recent research has shown that parasitoid symbionts such as polydnaviruses may also influence plant-mediated interactions among members of plant-associated communities…
Grouping facilitates avoidance of parasites by fish
2013
Background. Parasite distribution is often highly heterogeneous, and intensity of infection depends, among other things, on how well hosts can avoid areas with a high concentration of parasites. We studied the role of fish behaviour in avoiding microhabitats with a high infection risk using Oncorhynchus mykiss and cercariae of Diplostomum pseudospathaceum as a model. Spatial distribution of parasites in experimental tanks was highly heterogeneous. We hypothesized that fish in groups are better at recognizing a parasitized area and avoiding it than solitary fish. Methods. Number of fish, either solitary or in groups of 5, was recorded in different compartments of a shuttle tank where fish co…
Structural analysis of Cryptosporidium parvum.
2004
Cryptosporidium parvum(Apicomplexa, formerly Sporozoa) is the causative agent of cryptosporidiosis, an enteric disease of substantial medical and veterinary importance.C. parvumshows a number of unique features that differ from the rest of the class of coccidea in which it is currently grouped taxonomically. Differences occur in the overall structure of the transmission form and the invasive stages of the parasite, its intracellular location, the presence of recently described additional extracellular stages, the host range and target cell tropism, the ability to autoinfection, the nonresponsiveness to anticoccidial drugs, the immune response of the host, and immunochemical and genetic char…
Morphology and in vitro infectivity of sporozoites of Cryptosporidium parvum.
2009
An important obstacle in studying Cryptosporidium parvum is the lack of a permanent in vitro cultivation system of the parasite. While short-term cultures using various host cell lines have been widely employed, long-term cultures that would facilitate the immortalization of C. parvum isolates have not yet been developed. The description of the complete development of C. parvum in cell-free culture in 2004 has been received with great interest and also with some astonishment. Unfortunately, attempts to reproduce these results with different isolates of C. parvum and also C. hominis have failed. In this report, we provide an alternative interpretation of the nature of a parasite stage that o…
Survival and infectivity of Hypoderaeum conoideum and Euparyphium albuferensis cercariae under laboratory conditions.
1999
The survival characteristics of the cercariae of Hypoderaeumconoideum and Euparyphiumalbuferensis (Trematoda: Echinostomatidae) at 20°C and 30°C are described, and the age dependency of their infectivity at 20°C is studied to determine their respective transmission efficiencies. Cercarial survival was found to be age-dependent and was higher at 20°C. For both cercariae, the maximum life-span was 26 h at 20°C and 16 h at 30°C, and their respective times to 50% mortality were similar at each temperature. Both cercariae seem to be well adapted to transmission in their natural habitat, though cercarial infectivity of H. conoideum was higher than that of E. albuferensis, this being correlated wi…
Interactions among co-infecting parasite species: a mechanism maintaining genetic variation in parasites?
2008
Individuals of free-living organisms are often infected simultaneously by a community of parasites. If the co-infecting parasites interact, then this can add significantly to the diversity of host genotype×parasite genotype interactions. However, interactions between parasite species are usually not examined considering potential variation in interactions between different strain combinations of co-infecting parasites. Here, we examined the importance of interactions between strains of fish eye flukes Diplostomum spathaceum and Diplostomum gasterostei on their infectivity in naive fish hosts. We assessed the infection success of strains of both species in single-strain exposures and in co-…
Delayed transmission of a parasite is compensated by accelerated growth.
2005
Compensatory or ‘catch-up’ growth following prolonged periods of food shortages is known to exist in many free-living animals. It is generally assumed that growth rates under normal circumstances are below maximum because elevated rates of growth are costly. The present paper gives experimental evidence that such compensatory growth mechanisms also exist in parasitic species. We explored the effect of periodic host unavailability on survival, infectivity and growth of the fish ectoparasiteArgulus coregoni. Survival and infectivity ofA. coregonimetanauplii deprived of a host for selected time periods were age dependent, which indicates that all metanauplii carry similar energy resources for …
Echinostoma friedi: the effect of age of adult worms on the infectivity of miracidia.
2004
AbstractThe effect of ageing of adults ofEchinostoma friedi(Trematoda: Echinostomatidae) on the infectivity of miracidia yielded was analysed. Miracidia were obtained after hatching of eggs obtained from adult worms ofE. friedicollected weekly during the course of experimental infections in golden hamsters. Miracidial infectivity, measured in terms of percentage of infection inLymnaea peregra, was significantly influenced by the age of the adult worms from which the miracidia were derived. Infective miracidia only were obtained from adult worms in the age range from 4 to 9 weeks post-infection. Infectivity was maximal in those miracidia derived from adults collected 8 and 9 weeks post-infec…
Presence of Pomphorhynchus laevis in Salamandra salamandra
1995
AbstractInfection of Salamandra salamandra larvae (Amphibia: Urodela) with the fish acanthocephalan Pomphorhynchus laevis was detected in a fish-free mountain brook. Gammarus fossarum was found to be the intermediate host. The parasites were probably inadvertently introduced through fish breeding practices. Evidence was obtained that Pomphorhynchus laevis persists, at least for several months, in postmetamorphic fire salamanders.
Local adaptation of a holoparasitic plant, Cuscuta europaea: variation among populations
2000
Locally adapted parasites have higher infectivity and/or fitness on sympatric than on allopatric hosts. We tested local adaptation of a holoparasitic plant, Cuscuta europaea, to its host plant, Urtica dioica. We infected hosts from five sites with holoparasites from the same five sites and measured local adaptation in terms of infectivity and parasite performance (biomass) in a reciprocal cross-infection experiment. The virulence of the parasite did not differ between sympatric and allopatric hosts. Overall, parasites had higher infectivity on sympatric hosts but infectivity and parasite performance varied among populations. Parasites from one of the populations showed local adaptation in t…