Completion of the life cycle of Tylodelphys mashonense (Sudarikov, 1971) (Digenea: Diplostomidae) with DNA barcodes and rDNA sequences.

The life cycle of Tylodelphys mashonense (Digenea: Diplostomidae), whose metacercariae occur in the cranial cavity of the widely cultivated catfish Clarias gariepinus, was resolved by the application of molecular markers. Both COI barcodes and ITS sequences obtained from diplostomid-like cercariae infecting Bulinus spp. from Mindu Dam, Morogoro, matched those acquired from metacercariae from the catfish C. gariepinus, and those from adult T. mashonense from the grey heron Ardea cinerea and the white egret Egretta alba. The success in linking the life cycle stages of T. mashonense using molecular tools highlights the usefulness of this approach in resolving the complex life cycles of digeneans in the absence of experimental establishment.

Plagiorchis elegans (Trematoda) induces immune response in an incompatible snail host Biomphalaria glabrata (Pulmonata: Planorbidae).

Plagiorchis elegans has been shown to decrease the fecundity and survivorship of the incompatible snail host Biomphalaria glabrata. Furthermore, a prior infection with P. elegans was shown to render the snails resistant to the compatible parasite Schistosoma mansoni. Here, we test the hypothesis that infection with P. elegans stimulates the immune system of B. glabrata. Our findings indicate that infection by P. elegans significantly increased the number of free hemocytes in the hemolymph of B. glabrata by an average of ~60%. Furthermore, this immuno-stimulated state lasted from the first day post-infection (PI) to some time between 7 and 21 days PI. This is one of the few reported examples of a parasite stimulating the immune response of an incompatible host.

Impacts of agriculture on the parasite communities of northern leopard frogs (Rana pipiens) in southern Quebec, Canada.

Given that numerous amphibians are suffering population declines, it is becoming increasingly important to examine the relationship between disease and environmental disturbance. Indeed, while many studies relate anthropogenic activity to changes in the parasitism of snails and fishes, little is known of the impact on the parasites of amphibians, particularly from agriculture. For 2 years, the parasite communities of metamorphic northern leopard frogs from 7 agricultural wetlands were compared with those from 2 reference wetlands to study differences in parasite community diversity and abundance of various species under pristine conditions and 3 categories of disturbance: only agricultural landscape, only pesticides, and agricultural landscape with pesticides. Agricultural (and urban) area was negatively related to species richness, and associated with the near absence of adult parasites and species that infect birds or mammals. We suggest that agriculture and urbanization may hinder parasite transmission to frogs by limiting access of other vertebrate hosts of their parasites to wetlands. The only parasite found at all localities was an unidentified echinostome infecting the kidneys. This parasite dominated communities in localities surrounded by the most agricultural land, suggesting generalist parasites may persist in disrupted habitats. Community composition was associated with dissolved organic carbon and conductivity, but few links were found with pesticides. Pollution effects may be masked by a strong impact of land use on parasite transmission.

An annotated checklist of Hymenolepidid cestodes described from birds: 1983-2002.

A survey of the literature covering the period from January 1983 to December 2002 revealed that 17 genera and 106 species of cestodes belonging to the family Hymenolepididae have been described from birds since the publication of Schmidt's Handbook of Tapeworm Identification (his literature search terminated in March, 1983). Although the family has been revised recently, Schmidt's monograph provides the most recent list of species within the family. This work updates the list of species reported from avian hosts and includes data on the host, and collection locality along with the dimensions of the strobila, the number and length of the rostellar hooks, where applicable, and the dimensions of the cirrus sac as reported in original descriptions.

Effects of cadmium upon longevity of Diplostomum sp. (Trematoda: Diplostomidae) cercariae.

Laboratory experiments were conducted to examine the impact of cadmium (Cd) on survival of Diplostomum sp. cercariae. Freshly emerged cercariae were exposed to Cd solutions at concentrations ranging between 0.2 and 200 microg/l. The mortality patterns and mean survival times (MSTs) of the exposed parasites were determined by the Kaplan-Meier estimator and were compared (Log-Rank test) to corresponding patterns and estimators of the unexposed controls. Cd concentrations >20 microg/l caused statistically significant changes in the mortality pattern of Diplostomum sp. cercariae and reduced MST by at least five hours compared to the control group, where MST was 52 h. The results show that longevity of the free-living Diplostomum sp. cercariae can be reduced by direct exposure to heavy metals. Cd contamination of aquatic habitats thus potentially can have an impact on parasite populations and communities.

Effects of mercury and chromium upon longevity of Diplostomum sp. (Trematoda: Diplostomidae) cercariae.

Laboratory experiments were carried out to examine the impact of mercury and chromium upon survival of Diplostomum sp. cercariae. Freshly emerged cercariae were exposed to solutions of either mercury, at concentrations ranging between 0.1 and 100 microg/l, or chromium at concentrations from 2 microg/l to 2 mg/l. The mortality patterns and mean survival times (MSTs) of the exposed parasites were determined by the Kaplan-Meier estimator and were compared (log-rank test) with corresponding patterns and estimators of the unexposed controls. Mercury concentrations > or = 10 microg/l caused statistically significant changes in the mortality pattern of Diplostomum sp. cercariae and reduced MST by at least 9 h compared with the control group, in which MST was 42 h. Cercariae exposed to chromium solutions had statistically significant changes in mortality pattern only at a concentration of 2 mg/l and exhibited a reduction in MST of 8 h compared with the control (MST = 41 h). The results show for the first time that longevity of Diplostomum sp. cercariae can be reduced by direct exposure to heavy metals. Ecotoxicological effects of mercury are manifested at lower concentrations than those of chromium, and thus potentially have a higher impact on parasite populations and communities.

Respiratory nematodiases in raptors in Quebec.

This is a retrospective study on wild raptors submitted to the Université de Montréal (Quebec, Canada) from 1989 to 1996. Cyathostoma spp. (Nematoda: Syngamidae) adults and/or eggs were found in air sacs, lungs, bronchi, and trachea of 12 raptors (Falconiformes and Strigiformes) from Quebec, Canada, belonging to eight different species, five of which are first host records for this parasite: barred owl (Strix varia), snowy owl (Nyctea scandiaca), northern harrier (Circus cyaneus), northern goshawk (Accipiter gentilis), and broad-winged hawk (Buteo platypterus). The infection was considered fatal in four birds, while no significant clinical signs were observed in the other cases. Major pathologic changes included diffuse pyogranulomatous air sacculitis, pneumonia, and bronchitis. A few unidentified larval nematodes embedded in a granuloma were found in the lungs of an additional Coopers' hawk (Accipiter cooperii); they were not considered clinically significant. A dead nematode, surrounded by necrotic inflammatory cells, was found in the air sac of a northern goshawk. The presence of nematodes in air sacs or lungs should be considered in wild raptors demonstrating respiratory problems.

Explaining co-occurrence among helminth species of lesser snow geese (Chen caerulescens) during their winter and spring migration.

The digestive tracts of 771 lesser snow geese (Chen caerulescens) collected from January to May 1983 from 12 locations (27 samples) were examined for helminth parasites to determine whether parasite species present in wintering geese or in spring migrants occurred independently of each other. Nine helminth species were identified. Seven had mean prevalences >5% and were the focus of this study. Six of those species were waterfowl generalists, one was a goose specialist. Our primary objective was to assess the potential contribution of factors, other than species interactions, in determining patterns of co-occurrence between helminth species. There were few negative relationships between helminth species, regardless of whether presence-absence or abundance data were used. However, some species pairs showed recurrent and significant co-occurrences. There were similar and significant effects of timing of sampling, host gender, and host age, on prevalence and mean abundance of particular species. Co-occurrences were found for those species that showed seasonal declines in prevalence, for those expected to have high colonizing ability based on host age profiles (using abundance data), and for abundant species that may have shared vectors or environmental conditions favorable for transmission. Thus, similarities between parasites in their abundance, transmission biology, and phenology seem sufficient to explain species co-occurrences without invoking other processes such as species interactions.

Helminth fauna of Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii at Barberspan, South Africa.

Thirty-four species of gastrointestinal helminths were found in 25 Anas undulata, 21 Anas erythrorhyncha, ten Anas capensis and seven Anas smithii collected at Barberspan, South Africa. Excluding four new taxa, 11 new African records, and 14, 11, 12 and nine new host records were established for Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii, respectively. The helminth community included 13 cosmopolitan species, seven species known only from the holarctic, one species known only from the south Pacific and 13 new or unidentified species that appear to be restricted to Africa. The infection levels of the common helminth species in the mainly carnivorous Anas capensis and Anas smithii, were generally much higher than those of species infecting Anas undulata or Anas erythrorhyncha.

A checklist of helminths from the respiratory system and gastrointestinal tracts of African Anatidae.

A literature survey revealed that 72 helminth species, including 14 known only to the generic level, had been reported from the digestive or respiratory tracts of 28 species of Anatidae in Africa. Most of the digeneans and nematodes reported, were cosmopolitan species that occur in a range of hosts. However, two groups of cestodes, one consisting of cosmopolitan or Eurasian species and the other consisting of species restricted mainly to sub-Saharan Africa, were apparent. A host-parasite list and a detailed parasite-host list provide the synyonomies related to African records, the host and geographical distribution of each species, and the authority and country of origin for each record.

A comparison of the helminth communities in Anas undulata, Anas erythrorhyncha, Anas capensis and Anas smithii at Barberspan, South Africa.

Examination of the helminth communities in 25 yellow-billed ducks (Anas undulata), 21 red-billed ducks (Anas erythrorhyncha), ten Cape teal (Anas capensis) and seven Cape shovellers (Anas smithii) that had overwintered at Barberspan, revealed differences in community structure. Infracommunities in yellow-billed and red-billed ducks were characterized by low diversity and high eveness, and generally consisted of less than 100 helminths per duck. Similarity values (mean percent similarity and mean Jaccard's coefficients) were low. In contrast, infracommunities in Cape teal and Cape shovellers were more diverse, displayed low eveness values and consisted of far greater numbers of helminths. Mean similarity values for the infracommunities in Cape teal and Cape shovellers were much higher than those in yellow-billed or red-billed ducks. The component communities in all four duck hosts were species rich. Those in yellow-billed and red-billed ducks, however, consisted predominantly of satellite species and no core species were present, whereas those in Cape teal and Cape shoveller included several core species. Cape teal and Cape shovellers each had a group of recurrent species but there was not much of a tendency for species to co-occur in yellow-billed and red-billed ducks. Multivariate analysis revealed a greater similarity between the communities in Cape teal and Cape shovellers than between the latter and the communities in yellow-billed or red-billed ducks. Communities in Cape teal and Cape shovellers could be distinguished from each other by the presence or absence of particular cestode species. The communities in these two species could be distinguished from those in yellow-billed or red-billed ducks by a suite of cestode species that was absent in the latter two. Two recurrent groups, consisting of eight and two species, were identified in the compound community. Each group consisted of species found predominantly in Cape teal and Cape shovellers. Patterns seen in the helminth communities of the various hosts reflected differences in diet, but other factors, including feeding behaviour, spatial segregation and host specificity, may also have had an effect.

Fimbriasacculus africanensis n. gen., n. sp. (Cestoda: Hymenolepididae) from Anas capensis, Anas undulata, and Anas erythrorhyncha (Anatidae) in South Africa.

Fimbriasacculus africanensis n. gen., n. sp., occurred in Anas capensis (50%), Anas erythrorhyncha (5%), and Anas undulata (12%) collected in the vicinity of the Barberspan Ornithological Research Station, Republic of South Africa. The new genus differs from others in the subfamily Fimbriariinae (Fimbriaria, Fimbriarioides, Fimbriariella, and Profimbriaria) in having 2 testes per proglottid rather than 3, an accessory sac, and a preovarian instead of postovarian vitelline gland. Fimbriasacculus africanensis n. sp. is described as the only known species in the genus. An emended diagnosis of the subfamily Fimbriariinae is provided.

Species- and size-specific infection of snails by Cyclocoelum mutabile (Digenea: Cyclocoelidae).

Infectivity of Cyclocoelum mutabile miracidia to 9 species and up to 4 size classes of pulmonate snails at 14, 16, and 20 C was studied under laboratory conditions. Of the 9 species examined, 6 (Stagnicola elodes, Lymnaea stagnalis, Gyraulus parvus, Gyraulus circumstriatus, Promenetus exacuous, and Armiger crista) were highly susceptible (infection success > or = 25%), 2 (Physa jennessi and Helisoma trivolvis) had low susceptibility (infection success < 25%, > 0), and 1 (Physa gyrina) was not susceptible to infection. Within highly susceptible species, snail size was negatively related to susceptibility and temperature had variable effects. Infection success was not affected by temperature or snail size in species with low susceptibility. Production of cercariae was negatively correlated with susceptibility among snails of different sizes and species, but was not influenced by snail size for a given species. Among species, metacercariae production was typically higher in lymnaeids than in either planorbids or physids. Results of experiments where miracidia were provided with a choice of 2 different snails suggest that they do not discriminate between species with high and low susceptibility.

Field studies on the transmission and survival of Cyclocoelum mutabile (Digenea) infections in natural snail populations in southern Manitoba, Canada.

The transmission of Cyclocoelum mutabile to snails was examined under natural conditions by sampling the snail communities of 4 natural ponds that had been exposed experimentally to infection by laboratory-infected coots (Fulica americana). Five of 6 snail species in the ponds, Physa jennessi, Promenetus exacuous, Armiger crista, Gyraulus parvus, and Stagnicola elodes, became infected. No natural infections were found in the few Helisoma trivolvis examined. The second most abundant species Promenetus exacuous was infected most often, whereas Physa jennessi, the most abundant species present, was rarely infected. The temporal pattern of infections in the snail community suggests the transmission window of this parasite in southern Manitoba is limited by both the 14 C hatching threshold of the fluke eggs and the seasonality of ovigerous infections in the coot host. No naturally overwintering infections were found in snails from these ponds, which were examined the following spring. None of the 1,120 laboratory-infected snails placed in cages and held overwinter in the ponds survived, whereas 14 of the 1,120 uninfected control snails kept in the same cages survived. These results are consistent with the hypothesis that C. mutabile must be reestablished in northern waterfowl breeding areas each spring.

Influence of storage and examination methods on the recovery and size of metacercariae of Cyathocotyle bushiensis and Sphaeridiotrema pseudoglobulus (Digenea).

The recovery of metacercariae of Cyathocotyle bushiensis (Digenea: Cyathocotylidae) and Sphaeridiotrema pseudoglobulus (Digenea: Psilostomidae) from Bithynia tentaculata (Gastropoda: Prosobranchia) subjected to 3 methods of storage (70% alcohol, freezing, and fresh) and 2 methods of examination (crushing or artificial digestion) was evaluated. Prevalence and abundance of fully developed metacercariae of C. bushiensis and metacercariae of S. pseudoglobulus did not significantly vary as a result of storage or examination methods; however, digestion of frozen and fresh snails resulted in a significantly lower prevalence and abundance of not fully developed metacercariae of C. bushiensis. Furthermore, freezing or storing snails in alcohol may result in misclassification of the metacercariae of C. bushiensis. Both methods of storage and examination also affected the size of the metacercariae of both digeneans. Although digested snails were easier to examine, there appeared to be no overall gain in time by using digestion instead of crushing.

Gross lesions and hematological changes in domesticated mallard ducklings experimentally infected with Cyathocotyle bushiensis (Digenea).

The digenean Cyathocotyle bushiensis has been associated with late summer fatalities of dabbling ducks in southern Québec. The objective of this study was to investigate the intensity- and time-dependent pathogenesis induced by experimental infection with this digenean in domesticated mallard ducklings. Lesions, hemorrhagic spots, plaques, and cores were observed in the ceca. Both affected tissue area and core weight increased with increasing intensity of infection. Magnitude of tissue damage increased with increasing duration of infection. Dye, administered intravenously, was found within the cecal lumen of infected ducks demonstrating increased permeability of the cecal wall to vascular products. The data suggest that infection was associated with decreased weight gain and a minor increase in body temperature. Elevations in hemoglobin concentration and packed cell volume were observed in some infected ducklings.

A possible role for altered poly(adenosine diphosphoribose)-synthesis in the sensitivity of human head and neck squamous carcinoma cells to ionizing radiation.

Cytotoxicity, extent of DNA double-strand breaks, and stimulation of poly(adenosine diphosphoribose)-synthesis were measured in two established human head and neck squamous carcinoma cell lines (183A and 1483) following x-irradiation. The 1483 cell line was 15-fold more resistant to x-ray-mediated cytotoxicity than was the 183A cell line. X-ray-mediated DNA strand cleavage also differed in these two cell lines with the absolute frequency of DNA double-strand breaks in the sensitive cells 183A cells being twice that in the resistant 1483 cell line. No detectable stimulation of poly(adenosine diphosphoribose)-synthesis was measured in the sensitive 183A cells whereas a marked increase in incorporation of [3H]-nicotinamide adenine dinucleotide was readily detected following x-irradiation of the resistant 1483 cells. These findings suggest a possible role of altered poly(adenosine diphosphoribose)-synthesis in the sensitivity of human head and neck squamous carcinoma cells to ionizing radiation.

Binding of caput epididymal mouse sperm to the zona pellucida.

Immature sperm from the caput epididymis are immotile and infertile. It is thought that caput epididymal sperm are infertile due to their immotility, as well as to an inability to bind to the zona pellucida, suggesting the absence of a functional receptor for the zona. However, the sperm receptor for the zona pellucida has been identified previously as the enzyme galactosyltransferase (GalTase) (L. C. Lopez et al. (1985) J. Cell Biol. 101, 1501-1510) and is present on the surface of caput as well as cauda epididymal sperm (N. F. Scully et al., (1987) Dev. Biol. 124, 111-124.). In this paper we examine this apparent conflict and show that immotile caput epididymal sperm are able to bind to the zona pellucida if they are first washed free of caput epididymal secretions, which contain factors that inhibit sperm-zona binding. Consistent with this finding are results that show that caput epididymal fluid is capable of inhibiting the binding of mature, cauda epididymal sperm to the zona pellucida. Caput epididymal fluid contains, among many other components, a soluble GalTase and an alpha-lactalbumin-like protein, both of which are capable of inhibiting mouse sperm-zona binding. Thus, caput epididymal sperm have the appropriate receptor, i.e., GalTase, for the zona pellucida, to which they can bind if removed from the inhibitory factors that mask their zona-binding ability.