No description available.

Specimens from the National History Museum, London, and from the United States National Parasite Collection, Beltsville, United States of America., which had all previously been identified as Mescoelium monas from a variety of definitive hosts (amphibians, reptiles and/or fish), were evaluated using all available literature and the body-type keys developed by Norman Dronen. None of these 85 putative M. monas specimens appeared to fit the original description of M. monas. There are likely multiple species of Mescoelium worldwide, and the M. monas complex, as currently defined, is not a unified monospecific grouping. The present study leads to the conclusion that there can be no fewer than 9 species of Mescoelium (6 body types, 3 of which can be divided into 2 separate groups based on the median or submedian placement of the genital pore). The specimens of M. monas I examined represented 3 of the 6 body types identified by Norman Dronen: the M. monas body type, the M. lanceatum body type, and the M. pesteri body type. Because Mesocoelium is a difficult group within which to distinguish species, it may be expedient in endoparasitic surveys of amphibians, fish and reptiles to consider any specimen of Mesocoelium found to be M. monas. Because Mesocoelium is a difficult group within which to distinguish species, it may be expedient in endoparasitic surveys of amphibians, fish and reptiles to consider any specimen of Mesocoelium found to be M. monas. Subsequent reevalations must consider these key characteristics: genital pore placement, cecal length, vitelline follicle distribution, along with other supporting characteristics.

No description available.

Metagonimoides oregonensis is a digenetic trematode that infects raccoons as definitive hosts, the snail Elimia proxima as a first intermediate host and in the southern Appalachians, encysts in the muscle tissue of a variety of second intermediate salamander hosts. My first study examined 289 individual salamanders representing six species from 23 streams in North Carolina to determine which species of salamanders are naturally infected.  I found that five of the six species examined had natural infections, but that there was variation in infection intensity and prevalence among the species. Of the six species, Desmognathus quadramaculatus may be most important in transmission, as they had the highest prevalence and intensity of infection. This may be due to their long larval period, which results in a longer trematode accrual period.  My second study explored the role of host and parasite behavior in driving infection dynamics in this system. I examined both parasite response to host chemical cues and host response to parasite presence and chemical cues. I did not see a behavioral response by either the parasite or the host, indicating behavior is probably less important in determining variable infection among hosts in this system, than are environmental and ecological factors. My final study examined the effect of cercariae exposure (n=0, 20, 60) on locomotor performance of D. quadramaculatus, Eurycea wilderae and Hyla versicolor. I did not see any effect on locomotor performance for any of the species. / Master of Science

To examine the interactions of disease and pollution on amphibian populations around the world, I investigated the effect of infection on contaminant susceptibility in pickerel frog, Rana palustris, larvae. I conducted standard 48-hr toxicity tests to examine effect of trematode parasite, Echinostoma trivolvis, infection (0, 10, or 30 cercaria) on the susceptibility of pickerel frog tadpoles to the widely used organophosphate insecticide malathion. LC50 values ranged from 16.5 – 17.4 mg/L, within the range reported for other amphibian species. I found no differences in susceptibility to malathion among parasite treatments. Nevertheless, this crucial question remains to be tested in other amphibian host-parasite systems. Second, I studied the reverse interaction, the effect of pesticide exposure on susceptibility to parasite infection. I exposed pickerel frog embryos to low doses of malathion, then subjected morphologically normal tadpoles to E. trivolvis later in development. Malathion significantly decreased hatching success and viability rates at concentrations lower than previously documented for anuran embryos. After 7 wk of development in water with no malathion, tadpoles previously exposed to malathion as embryos suffered increased parasite encystment rates compared to controls. My research identifies embryonic development as a sensitive window and the potential for increased susceptibility to infection long after pesticide exposure has ceased. With potential for increased parasite prevalence from eutrophication and climate change, my data underscore the importance of understanding the reciprocal influences of parasites and pesticides in amphibians. / Master of Science

The trematode Bolbophorus damnificus (Digenea: Bolbophoridae) has deleterious effects on production efficiency of farm-raised catfish. The effects of B. damnificus on channel and hybrid catfish, as well as the prevalence and longevity of the trematode stages impacting production, are not well understood. This study aimed to understand the prevalence of infected snails, determine the longevity and site specificity of B. damnificus cercaria in catfish, and compare mortality and physiological response between channel and hybrid catfish during infection. The infectivity and survival of B. damnificus cercariae declined significantly at 12h intervals from 12-36h, and subsequent trials were standardized using cercariae <12h old. Metacercariae persisted in both fish types for 13 months and were found commonly in the posterior midsection. Hybrid catfish exhibited lower mortality than channel catfish. Exposed catfish exhibited anemia corresponding to parasite encapsulation, however no difference was found between fish types in physiological response during infection and subsequent recovery.

No description available.

Le parasite Alaria alata (Goeze, 1782) est un trématode qui nécessite trois hôtes obligatoire et qui présente la particularité de pouvoir infester un grand nombre d'espèces animales (oiseaux, reptiles, mammifères) au stade mésocercaire..Depuis que la recherche de trichine par des méthodes de digestion a été rendu obligatoire chez les sangliers chassés dans l'ensemble des pays de l'union européenne, elle a permis également la détection des mésocercaires dans les muscles de ces animaux. L'étude de la répartition des déclarations de sangliers porteurs montre que les cas se situent majoritairement dans l'Est de la France. Le nombre de déclarations en augmentation entre 2007 et 2010 est probablement lié à la sensibilisation des laboratoires à la présence d'A. alata plutôt qu'une réelle émergence. A partir d'une base de données de déclaration dans le Bas-Rhin montre que la répartition spatiale des sangliers porteurs du parasite se limite à la vallée du Rhin bornée par le massif des Vosges soulignant ainsi l'importance des zones humides pour la maintien du parasite. Une relation significative existe entre le portage du parasite et les saisons printemps-été ainsi qu'une émergence réelle du parasite entre 2007 et 2010. Par une approche moléculaire le rôle de Planorbis planorbis et Anisus vortex comme premier hôte intermédiaire a été confirmée in natura lors de l'examen de mollusques. La nature des biotopes des mollusques a été abordée ainsi que leur périodes d'émission des cercaires d'A. alata ce qui explique partiellement la saisonnalité des cas observée chez les sangliers du Bas-Rhin..Des prélèvements de muscles sur 6 sangliers chassés dans des zones de forte circulation du parasite, soumis à une méthode de Baermann modifiée, ont permis de mettre en évidence des taux d'infestation de plus de 1000 mésocercaires pour 100 gr. La distribution des mésocercaires chez le sanglier est très large avec toutefois des localisations ciblées vers les tissus antérieurs au diaphragme. Nous avons également mis en évidence une sensibilité du parasite à la congélation et une longue persistance dans les viandes en décomposition.. A partir de mésocercaires isolées sur sanglier, des infestations sur souris ainsi que des tests de survie in vitro ont été effectués :. Chez les souris, chez certains amphibiens et in vitro, une encapsulation active des mésocercaires a été observée ce qui tend à montrer que le parasite dispose de moyens d'éviter la réaction de l'hôte. Si le parasite (au stade cercaires et mésocercaires) est fortement inféodé aux milieux humides, il est capable de phénomène de transfuge à une grande variété d'hôtes paraténiques qui ainsi participent très largement à son maintien et à sa dispersion. / The parasite Alaria alata (Goeze, 1782) is a flatworm which needs three obligatory hosts for its development but its particularity lies in that it can infect a wide number of hosts (birds, reptiles, mammals) at the mesocercarial stage. Since the search of trichinella by pepsinic digestion in the muscles of hunted wild boars has become mandatory in the European union, this analysis has also lead to the detection of Alaria alata in the muscles of these animals. The study of case distributions shows that most of the cases have occurred in the East of France. The number of infected wild boars has increased between 2007 and 2010 which is probably more due to the awareness of laboratories to the presence of A. alata mesocercaria than to a true emergence. Using database for the Bas-Rhin département, we were able to show a geographical cluster of positive wild boars around the Rhine Valley and bordered by the Vosges Mountains, hence showing the importance of wetland areas for the sustenance of the parasite. A significant association between A. alata positivity and the spring and summer seasons was noted as well as a true emergence of the parasite between 2007 and 2010. We then sought to identify the first intermediate snail hosts using molecular tools on snail and cercaria collected in infected areas which lead us to identify two Planorbid species: Planorbis planorbis and Anisus vortex. Search of these two species on different biotopes showed that specific environmental conditions were needed for these species, and therefore the parasite, to be present. We proceeded to test different muscular samples from 6 wild boars using a test derived from the Baermann method. Tests showed the highest parasite burdens ever observed in the literature with several samples over 1000 mesocercaria/100g. Distribution within the carcass is very wide though it appears to be oriented to the tissues anterior to the diaphragm. We also showed that the parasite was sensitive to freezing but long persisting in decaying meat. From the mesocercaria collected on the wild boars, experimental infections were performed on mice and survival tests were done in vitro. In mice, but also in amphibians and in vitro, mesocercaria actively formed an inert capsule which would tend to prove the existence of equipments to evade the host's reactions. The works presented here show two important aspects of A. alata's life cycle: the importance of wetlands for its sustenance and also the parasite's ability to persist in a wide variety of paratenic hosts which participate in its sustainance and dispersal.

Understanding the ecological processes that impact parasite abundance and distribution is critically important for epidemiology and predicting how infectious disease dynamics may respond to future disturbance. Digenean trematodes (Platyhelminthes: Trematoda) are parasitic flatworms with complex, multi-host life cycles that include snail first-intermediate hosts and vertebrate definitive hosts. Trematodes cause numerous diseases of humans (e.g. schistosomiasis) and livestock (e.g. fascioliasis), and impact the ecology of wildlife systems. Identifying the ecological mechanisms that regulate these complex, multi-host interactions will advance both our understanding of parasitism and the dynamics of infectious disease. By examining patterns of infection in Elimia (= Oxytrema = Goniobasis) proxima snails, my dissertation research investigated the environmental factors and ecological processes that structure trematode communities in streams. First, I examined temporal variation in trematode infection of snails in five headwater streams. Over a three year period, I found no consistent seasonal patterns of trematode infection. There was consistency across sites in trematode prevalence, as sites with high prevalence at the beginning of the study tended to remain sites of high infection, relative to lower prevalence sites. Second, I examined landscape level variation in trematode infection by characterizing the regional distribution, abundance and diversity of E. proxima infections in 20 headwater streams. I found a broad scale spatial pattern in trematode communities due to regional turnover in dominant species. This pattern was correlated with elevation, but there were no significant relationships with other environmental variables. Additionally, molecular characterization of trematodes indicated the presence of cryptic (morphologically indistinguishable) species complexes within this system, and variation in genetic diversity among trematode types may reflect differences in host dispersal abilities. Third, I examined trematode infection within a single stream network across multiple headwaters and the mainstem. I found a decreasing downstream gradient of trematode prevalence related to several environmental variables including elevation, snail density, conductivity, and stream depth. Additionally, headwater communities were nested subsets of the communities found in the mainstem. By combining approaches at different temporal and spatial scales, my dissertation research increases our understanding of the processes that impact the abundance and distribution of parasites. / Ph. D.

Double-crested cormorants have steadily increased in the Mississippi Delta. This bird serves as a definitive host for digenetic trematodes, many of which infect fish. To identify these digeneans in cormorants and determine the impact these infections have on wild fish in the Mississippi Delta, two surveys were done. Cormorants were collected for two years in the Mississippi Delta. At necropsy trematodes were collected and identified morphologically and molecularly as: Austrodiplostomum ostrowskiae, Hysteromorpha triloba, Drepanocephalus spathans, Ascocotyle longa and Pseudopsilostoma varium. Additionally, 14 fish species were collected from a Mississippi Delta lake. Fish were examined for parasites and Posthodiplostomum minimum metacercariae were found in multiple organs in 6/14 fish species. The 18S gene sequences of these metacercariae were identical to published P. minimum sequences, whereas the cytochrome oxidase I (COI) sequences matched published COI sequences for Posthodiplostomum sp. 3, 5 and 8, suggesting subspecies of Posthodiplostomum in this fish population.