Time filter

Source Type

Abbotsford, Canada

Himsworth C.G.,University of British Columbia | Himsworth C.G.,Animal Health Center | Parsons K.L.,University of British Columbia | Jardine C.,University of Guelph | Patrick D.M.,University of British Columbia
Vector-Borne and Zoonotic Diseases | Year: 2013

Urban Norway and black rats (Rattus norvegicus and Rattus rattus) are the source of a number of pathogens responsible for significant human morbidity and mortality in cities around the world. These pathogens include zoonotic bacteria (Leptospira interrogans, Yersina pestis, Rickettsia typhi, Bartonella spp., Streptobacillus moniliformis), viruses (Seoul hantavirus), and parasites (Angiostrongylus cantonensis). A more complete understanding of the ecology of these pathogens in people and rats is critical for determining the public health risks associated with urban rats and for developing strategies to monitor and mitigate those risks. Although the ecology of rat-associated zoonoses is complex, due to the multiple ways in which rats, people, pathogens, vectors, and the environment may interact, common determinants of human disease can still be identified. This review summarizes the ecology of zoonoses associated with urban rats with a view to identifying similarities, critical differences, and avenues for further study. © Copyright 2013, Mary Ann Liebert, Inc. Source

Hargreaves A.L.,Center for Conservation Research | Whiteside D.P.,Animal Health Center | Whiteside D.P.,University of Calgary | Gilchrist G.,Carleton University
Science of the Total Environment | Year: 2011

Exposure to contaminants is one hypothesis proposed to explain the global decline in shorebirds, and is also an increasing concern in the Arctic. We assessed potential contaminants (As, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn) at a shorebird breeding site in Nunavut, Canada. We compared element levels in soil, invertebrates and shorebird blood to assess evidence for bioconcentration and biomagnification within the Arctic-based food chain. We tested whether elements in blood, feathers and eggs of six shorebird species (Pluvialis squatarola, Calidris alpina, C. fuscicollis, Phalaropus fulicarius, Charadrius semipalmatus, and Arenaria interpres) were related to fitness endpoints: adult body condition, blood-parasite load, egg size, eggshell thickness, nest duration, and hatching success. To facilitate comparison to other sites, we summarise the published data on toxic metals in shorebird blood and egg contents.Element concentrations and invertebrate composition differed strongly among habitats, and habitat use and element concentrations differed among shorebird species. Hg, Se, Cd, Cu, and Zn bioconcentrated from soil to invertebrates, and Hg, Se and Fe biomagnified from invertebrates to shorebird blood. As, Ni, Pb, Co and Mn showed significant biodilution from soil to invertebrates to shorebirds. Soil element levels were within Canadian guidelines, and invertebrate Hg levels were below dietary levels suggested for the protection of wildlife. However, maximum Hg in blood and eggs approached levels associated with toxicological effects and Hg-pollution in other bird species. Parental blood-Hg was negatively related to egg volume, although the relationship varied among species. No other elements approached established toxicological thresholds. In conclusion, whereas we found little evidence that exposure to elements at this site is leading to the declines of the species studied, Hg, as found elsewhere in the Canadian Arctic, is of potential concern for breeding bird populations. © 2011 Elsevier B.V. Source

Hargreaves A.L.,Center for Conservation Research | Whiteside D.P.,Animal Health Center | Whiteside D.P.,University of Calgary | Gilchrist G.,Carleton University
Science of the Total Environment | Year: 2010

Exposure to contaminants is one hypothesis proposed to explain the global decline in shorebirds, and this is of particular concern in the arctic. However, little information exists on contaminant levels in arctic-breeding shorebirds, especially in Canada. We studied potential contaminants in three biparental shorebird species nesting in Nunavut, Canada: ruddy turnstones (Arenaria interpres), black-bellied plovers (Pluvialis squatarola) and semipalmated plovers (Charadrius semipalmatus). Blood, feathers and eggs were analyzed for As, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Tl, V, and Zn. We assessed whether element concentrations a) differed among species and sexes, b) were correlated among pairs and their eggs, and c) were related to fitness endpoints, namely body condition, blood-parasite load, nest survival days, and hatching success.Non-essential elements were found at lower concentrations than essential elements, with the exception of Hg. Maximum Hg levels in blood approached those associated with toxicological effects in other bird species, but other elements were well below known toxicological thresholds. Reproductive success was negatively correlated with paternal Hg and maternal Pb, although these effects were generally weak and varied among tissues. Element levels were positively correlated within pairs for blood-Hg (turnstones) and feather-Ni and Cr (semipalmated plovers); concentrations in eggs and maternal blood were never correlated. Concentrations of many elements differed among species, but there was no evidence that any species had higher overall exposure to non-essential metals. In conclusion, whereas we found little evidence that exposure to the majority of these elements is leading to declines of the species studied here, Hg levels were of potential concern and both Hg and Pb warrant further monitoring. © 2010 Elsevier B.V. Source

Voordouw M.J.,University of Victoria | Adama D.,BC Hydro | Houston B.,Fish and Wildlife Compensation Program Columbia Basin | Govindarajulu P.,Environment Canada | Robinson J.,Animal Health Center
BMC Ecology | Year: 2010

Background: Emerging infectious diseases threaten naïve host populations with extinction. Chytridiomycosis, an emerging infectious disease of amphibians, is caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd) and has been linked to global declines in amphibians.Results: We monitored the prevalence of Bd for four years in the Northern leopard frog, Rana pipiens, which is critically imperiled in British Columbia (BC), Canada. The prevalence of Bd initially increased and then remained constant over the last three years of the study. Young of the year emerging from breeding ponds in summer were rarely infected with Bd. Some individuals cleared their Bd infections and the return rate between infected and uninfected individuals was not significantly different.Conclusions: The BC population of R. pipiens appears to have evolved a level of resistance that allows it to co-exist with Bd. However, this small population of R. pipiens remains vulnerable to extinction. © 2010 Voordouw et al; licensee BioMed Central Ltd. Source

Marty G.D.,University of California at Davis | Marty G.D.,Animal Health Center | Heintz R.A.,National Oceanic and Atmospheric Administration
Diseases of Aquatic Organisms | Year: 2010

Marine survival of anadromous salmon species is highly variable, and causes of this variability are often unknown. In the 1990s, cultured pink salmon Oncorhynchus gorbuscha alevins from 2 different regions in Alaska, USA, had years with increased postemergent mortality that could not be attributed to viruses, bacteria, or parasites. In both regions, lifetime marine survival of the most severely affected fish groups was as low as 1.1% in 1 region and 0.13% in the other region. To determine causes of morbidity, alevins from both regions were sampled for detailed histopathology (n = 144 and 36). Microscopic lesions associated with increased postemergent mortality included ruptured yolk sacs or 'coagulated yolk' (up to 38% of abnormal fish affected) and invasive fungi in the stomach or swimbladder (up to 39% of abnormal fish affected). The diagnosis of a ruptured yolk sac was based on the presence of yolk protein in the peritoneal cavity. Putative yolk proteins sometimes also distended peritoneal macrophages, systemic vessels, hepatocyte cytoplasm, splenic macrophages, and renal ducts. The most severe case of visceral fungi had hyphae invading from the stomach into the swimbladder and kidney. In the hatchery with the greatest postemergent mortality, 38% of the abnormal fish sampled had no significant microscopic lesions. We hypothesize that ruptured yolk sacs and visceral fungi occurred in fish that were predisposed to develop these lesions because of poor body condition. High prevalence of these lesions might be a useful marker for predicting poor marine survival. © Inter-Research 2010. Source

Discover hidden collaborations