Canine Dirofilaria immitis infection in a hyperenzootic area: examination by parasitologic findings at necropsy and by two serodiagnostic methods

A total of 174 dogs from an area hyperenzootic for Dirofilaria immitis were grouped into 4 age categories and necropsied; information was obtained on adult D immitis infections and on the presence of microfilariae. Serum samples from these dogs were examined by an enzyme-linked immunosorbent assay (ELISA) for antibody to adult D immitis and by an indirect fluorescent antibody test (IFAT) for antibody to microfilarial surface antigens. In dogs less than or equal to 5 months of age, necropsy demonstrated no evidence of infection; however, positive serologic results indicated that some of these dogs had prepatent infections. The percentage of dogs with ELISA titers (positive) increased with age, as did the percentage of dogs with adult D immitis infections. The IFAT results were positive in some dogs in each age category. Sera from all 29 dogs with occult infections were positive by ELISA. Sera from 6 of 20 dogs with occult dual-sex heartworm infections and 1 of 9 dogs with occult single-sex heartworm infections were positive by IFAT. For diagnosing occult dirofilariasis, the ELISA had a positive predictive value which increased with age of the dog to a maximum of 65.0% in dogs greater than or equal to 12 months of age; ELISA had a negative predictive value of 100% in all age groups. In contrast, positive and negative predictive values for the IFAT decreased with age of the dog to 60% and 37.5%, respectively, in dogs greater than or equal to 12 months of age.     

Impact of rewilding,species introductions and climate change on the structure and function of the Yukon boreal forest ecosystem

Community and ecosystem changes are happening in the pristine boreal forest ecosystem of the Yukon for 2 reasons. First, climate change is affecting the abiotic environment (temperature, rainfall and growing season) and driving changes in plant productivity and predator–prey interactions. Second, simultaneously change is occurring because of mammal species reintroductions and rewilding. The key ecological question is the impact these faunal changes will have on trophic dynamics. Primary productivity in the boreal forest is increasing because of climatic warming, but plant species composition is unlikely to change significantly during the next 50–100 years. The 9–10‐year population cycle of snowshoe hares will persist but could be reduced in amplitude if winter weather increases predator hunting efficiency. Small rodents have increased in abundance because of increased vegetation growth. Arctic ground squirrels have disappeared from the forest because of increased predator hunting efficiency associated with shrub growth. Reintroductions have occurred for 2 reasons: human reintroductions of large ungulates and natural recolonization of mammals and birds extending their geographic ranges. The deliberate rewilding of wood bison (Bison bison) and elk (Cervus canadensis) has changed the trophic structure of this boreal ecosystem very little. The natural range expansion of mountain lions (Puma concolor), mule deer (Odocoileus hemionus) and American marten (Martes americana) should have few ecosystem effects. Understanding potential changes will require long‐term monitoring studies and experiments on a scale we rarely deem possible. Ecosystems affected by climate change, species reintroductions and human alteration of habitats cannot remain stable and changes will be critically dependent on food web interactions.     

Necrotizing hepatitis associated with a reo-like virus infection in a parrot

A young African grey parrot was presented for necropsy following a 3-to-4-day illness consisting of lethargy, anorexia, and diarrhea. A disseminated necrotizing hepatopathy was evident upon histologic examination of the liver. Aggregates of approximately 70-nm-diameter viral particles having morphology consistent with the family Reoviridae were demonstrated by thin-section and negative-staining electron microscopy.     

Parallel declines in pollinators and insect-pollinated plants in Britain and the Netherlands

Despite widespread concern about declines in pollination services, little is known about the patterns of change in most pollinator assemblages. By studying bee and hoverfly assemblages in Britain and the Netherlands, we found evidence of declines (pre-versus post-1980) in local bee diversity in both countries; however, divergent trends were observed in hoverflies. Depending on the assemblage and location, pollinator declines were most frequent in habitat and flower specialists, in univoltine species, and/or in nonmigrants. In conjunction with this evidence, outcrossing plant species that are reliant on the declining pollinators have themselves declined relative to other plant species. Taken together, these findings strongly suggest a causal connection between local extinctions of functionally linked plant and pollinator species.     

ULTRASONOGRAPHIC EXAMINATION OF THE THYROID GLAND OF HYPERTHYROID CATS: COMPARISON TO 99mTcO−4 SCINTIGRAPHY

High-resolution ultrasonography was evaluated as an alternative to ^99mTcO^-₄ scintigraphy for examining size and appearance of thyroid glands in hyperthyroid cats. Thyroid ultrasound examinations were performed on 6 normal cats and 14 cats with hyperthyroidism. Thyroid lobe volume was estimated from ultrasound images using the equation for a prolate ellipsoid, π/6 (length * height * width). Total thyroid volume was estimated by adding the volume estimations of the left and right lobes. Thyroid lobes of hyperthyroid cats were considered abnormal if estimated volume exceeded the 99% confidence interval for normal thyroid volume determined from the control group. Scintigraphic examinations performed on hyperthyroid cats were evaluated for unilateral versus bilateral disease and for the presence of ectopic activity. Mean thyroid lobe volume and total thyroid volume for normal cats was 85 and 169 mm³, respectively. Mean thyroid lobe volume and total thyroid volume for hyperthyroid cats was 578 and 889 mm³. There was a significant difference in mean estimated total thyroid volume of normal and hyperthyroid cats. Thyroid lobes with greater than normal TcO^-₄ uptake on scintigraphy were larger and had variable homogeneity, echogenicity, and margination on ultrasound examination. There also was an 85.7% agreement of scintigraphy and ultrasonography in differentiating normal from abnormal thyroid lobes. A fair correlation between estimated total thyroid volume of hyperthyroid cats and most recent pretherapy serum thyroxine values were also found. This preliminary study indicates that thyroid ultrasound examination may provide information that is useful for diagnosis and treatment of feline hyperthyroidism. Although ultrasound provides accurate evaluation of the thyroid glands, it cannot replace ^99mTcO^-₄ scintigraphy for screening of metastatic lesions and ectopic glands.     

Extinction risk of wood-living model species in forest landscapes as related to forest history and conservation strategy

Dead wood is a critical resource for biodiversity in boreal forests. We analysed the persistence of five model species inhabiting dead wood. By parameterising a metapopulation model (the incidence function model), the model species were all assigned characteristics that makes it likely that they have disappeared from some (20%) forest landscapes with a long history of forest management. In the metapopulation model, a forest stand (5 ha) was regarded as a habitat patch. The amount of habitat in each patch was obtained from models of dead wood dynamics of Norway spruce in central Sweden. Dead wood generated by altered management over the entire landscape was found to be less efficient in reducing extinction risks in comparison to the same amount of dead wood generated by protecting reserves. Because generation of dead wood by altered management is often less expensive than setting aside reserves, it is difficult to determine which conservation measure is most cost-efficient. In a landscape subjected to forestry for the first time, it was better to preserve a few large reserves than many small ones. However, in a managed, highly fragmented forest landscape it was better to set aside many small reserves. The reason for this was that small plots with high habitat quality could be selected, while large reserves originally contained habitats both of high and low quality, and the rate of habitat quality increase was low. A strategy for biodiversity conservation in a managed forest landscape should include information about the history of the landscape, the current amount and spatial distribution of forest habitats, and the potential for rapid restoration of forest habitats, both on managed and unmanaged forest land.     

Body size, niche breadth, and ecologically scaled responses to habitat fragmentation: mammalian predators in an agricultural landscape

The ability to make a priori assessments of a species' response to fragmentation, based on its distribution in the landscape, would serve as a valuable conservation and management tool. During 1997-1999, we monitored 717 scent stations to examine seasonal use of forest patches, corridors, and crop fields by coyotes (Canis latrans), domestic cats (Felis catus), foxes (Vulpes vulpes and Urocyon cinereoargenteus), raccoons (Procyon lotor), striped skunks (Mephitis mephitis), opossums (Didelphis virginiana), and long-tailed weasels (Mustela frenata). For each species we developed landscape-based ecologically scaled landscape indices (ELSI), and we modeled species spatial distribution across three spatial scales (landscape-level, element-level, and local habitat-level). Our results suggest that these predators view landscape fragmentation at different spatial scales and demonstrate strong interspecific differences in their response to elements of the landscape. All species except coyotes and domestic cats avoided agricultural fields. In general, predator species that were more mobile (i.e. high ESLI for landscape connectivity; coyotes) were characterized by landscape- and element-based logistic models. In contrast, models including local habitat features generally were most appropriate for less mobile or more stenophagous predators (e.g. long-tailed weasels). Our analysis extends the application of the ESLI concept to species assemblages that do not appear to function as metapopulations, and it highlights the importance of examining spatial scale and species-specific responses to habitat fragmentation. We discuss the relevance of these findings for defining ecological landscapes, understanding predator-prey interactions at multiple spatial scales, and conserving predator and prey populations in fragmented landscapes.     

Natural degradation of low-level petroleum hydrocarbon contamination under crop management

Journal of Soils and Sediments - Natural degradation of petroleum hydrocarbons (PHC) is a crucial process to consider when managing contaminated soils. However, the degradation rate is dictated by...     

Wood chips and wheat straw as alternative biofilter media for denitrification reactors treating aquaculture and other wastewaters with high nitrate concentrations

This study evaluated wood chips and wheat straw as inexpensive and readily available alternatives to more expensive plastic media for denitrification processes in treating aquaculture wastewaters or other high nitrate waters. Nine 3.8-L laboratory scale reactors (40 cm packed height × 10 cm diameter) were used to compare the performance of wood chips, wheat straw, and Kaldnes plastic media in the removal of nitrate from synthetic aquaculture wastewater. These upflow bioreactors were loaded at a constant flow rate and three influent NO₃–N concentrations of 50, 120, and 200 mg/L each for at least 4 weeks, in sequence. These experiments showed that both wood chips and wheat straw produced comparable denitrification rates to the Kaldnes plastic media. As much as 99% of nitrate was removed from the wastewater of 200 mg NO₃–N/L influent concentration. Pseudo-steady state denitrification rates for 200 mg NO₃–N/L influent concentrations averaged (1360 ± 40) g N/(m³ d) for wood chips, (1360 ± 80) g N/(m³ d) for wheat straw, and (1330 ± 70) g N/(m³ d) for Kaldnes media. These values were not the maximum potential of the reactors as nitrate profiles up through the reactors indicated that nitrate reductions in the lower half of the reactors were more than double the averages for the whole reactor. COD consumption per unit of NO₃–N removed was highest with the Kaldnes media (3.41–3.95) compared to wood chips (3.34–3.64) and wheat straw (3.26–3.46). Effluent ammonia concentrations were near zero while nitrites were around 2.0 mg NO₂–N/L for all reactor types and loading rates. During the denitrification process, alkalinity and pH increased while the oxidation–reduction potential decreased with nitrate removal.

Wood chips and wheat straw lost 16.2% and 37.7% of their masses, respectively, during the 140-day experiment. There were signs of physical degradation that included discoloration and structural transformation. The carbon to nitrogen ratio of the media also decreased. Both wood chips and wheat straw can be used as filter media for biological denitrification, but time limitations for the life of both materials must be considered.