During 16 of 21 consecutive annual breeding seasons, two diseases, Newcastle disease and avian cholera, killed approximately 50% of juvenile Double-crested Cormorants (Phalacrocorax auritus) in a large nesting colony in Canada. From 1994 to 2014, we recorded data annually on disease occurrence, causal pathogens, species and age classes affected, total number of breeding pairs of cormorants on the colony site, and other biological parameters. A mathematical model of pathogen transmission was constructed to assess the potential importance of transmission parameters and to test a hypothesis regarding the potential effect of the observed progressive loss of nest trees and the consequent shift from tree-nesting to ground-nesting behavior. The model indicated that juveniles from ground nests were 14 times more likely to die from epidemic disease (50.14% mortality) than were juveniles from nests in trees (3.57% mortality). Additive disease-related mortality of juvenile cormorants in the observed range of 40-60% would reduce a closed cormorant population over time. There was no directional change in the colony population during the study period, suggesting that immigration had compensated for disease-related mortality. Our results highlight the preeminent influence of environmental factors on pathogen transmission and the value of long-term data sets.

To achieve a contemporary understanding of the common and rare lesions that affect wild, urban Norway rats ( Rattus norvegicus), we conducted a detailed pathology analysis of 672 rats from Vancouver, British Columbia, Canada. Grossly evident lesions, such as wounds, abscesses, and neoplasms, were present in 71 of 672 rats (11%) and tended to be severe. The most common and significant lesions were infectious and inflammatory, most often affecting the respiratory tract and associated with bite wounds. We assessed a subset of rats (up to n = 406 per tissue) for the presence of microscopic lesions in a variety of organ systems. The most frequent lesions that could impact individual rat health included cardiomyopathy (128 of 406; 32%), chronic respiratory tract infections as indicated by pulmonary inducible bronchus-associated lymphoid tissue (270 of 403; 67%), tracheitis (192 of 372; 52%), and thyroid follicular hyperplasia (142 of 279; 51%). We isolated 21 bacterial species from purulent lesions in rats with bacterial infections, the most frequent of which were Escherichia coli, Enterococcus sp., and Staphylococcus aureus. Parasitic diseases in rats resulted from infection with several invasive nematodes: Capillaria hepatica in the liver (242 of 672; 36%), Eucoleus sp. in the upper gastrointestinal tract (164 of 399; 41%), and Trichosomoides crassicauda in the urinary bladder (59 of 194; 30%). Neoplastic, congenital, and degenerative lesions were rare, which likely reflects their adverse effect on survival in the urban environment. Our results establish a baseline of expected lesions in wild urban rats, which may have implications for urban rat and zoonotic pathogen ecology, as well as rat control in cities worldwide.

Avian influenza virus (AIV) occurrence and transmission remain important wildlife and human health issues in much of the world, including in North America. Through Canada's Inter-Agency Wild Bird Influenza Survey, close to 20,000 apparently healthy, wild dabbling ducks (of seven species) were tested for AIV between 2005 and 2011. We used these data to identify and evaluate ecological and demographic correlates of infection with low pathogenic AIVs in wild dabbling ducks (Anas spp.) across Canada. Generalized linear mixed effects model analyses revealed that risk of AIV infection was higher in hatch-year birds compared to adults, and was positively associated with a high proportion of hatch-year birds in the population. Males were more likely to be infected than females in British Columbia and in Eastern Provinces of Canada, but more complex relationships among age and sex cohorts were found in the Prairie Provinces. A species effect was apparent in Eastern Canada and British Columbia, where teal (A. discors and/or A. carolinensis) were less likely to be infected than mallards (A. platyrhynchos). Risk of AIV infection increased with the density of the breeding population, in both Eastern Canada and the Prairie Provinces, and lower temperatures preceding sampling were associated with a higher probability of AIV infection in Eastern Canada. Our results provide new insights into the ecological and demographic factors associated with AIV infection in waterfowl.

The Canadian prairies are one of the most important breeding and staging areas for migratory waterfowl in North America. Hundreds of thousands of waterfowl of numerous species from multiple flyways converge in and disperse from this region annually; therefore this region may be a key area for potential intra- and interspecific spread of infectious pathogens among migratory waterfowl in the Americas. Using Blue-winged Teal (Anas discors, BWTE), which have the most extensive migratory range among waterfowl species, we investigated ecologic risk factors for infection and antibody status to avian influenza virus (AIV), West Nile virus (WNV), and avian paramyxovirus-1 (APMV-1) in the three prairie provinces (Alberta, Saskatchewan, and Manitoba) prior to fall migration. We used generalized linear models to examine infection or evidence of exposure in relation to host (age, sex, body condition, exposure to other infections), spatiotemporal (year, province), population-level (local population densities of BWTE, total waterfowl densities), and environmental (local pond densities) factors. The probability of AIV infection in BWTE was associated with host factors (e.g., age and antibody status), population-level factors (e.g., local BWTE population density), and year. An interaction between age and AIV antibody status showed that hatch year birds with antibodies to AIV were more likely to be infected, suggesting an antibody response to an active infection. Infection with AIV was positively associated with local BWTE density, supporting the hypothesis of density-dependent transmission. The presence of antibodies to WNV and APMV-1 was positively associated with age and varied among years. Furthermore, the probability of being WNV antibody positive was positively associated with pond density rather than host population density, likely because ponds provide suitable breeding habitat for mosquitoes, the primary vectors for transmission. Our findings highlight the importance of spatiotemporal, environmental, and host factors at the individual and population levels, all of which may influence dynamics of these and other viruses in wild waterfowl populations.

Since the spread of highly pathogenic avian influenza (HPAI) H5N1 in the eastern hemisphere, numerous surveillance programs and studies have been undertaken to detect the occurrence, distribution, or spread of avian influenza viruses (AIV) in wild bird populations worldwide. To identify demographic determinants and spatiotemporal patterns of AIV infection in long distance migratory waterfowl in North America, we fitted generalized linear models with binominal distribution to analyze results from 13,574 blue-winged teal (Anas discors, BWTE) sampled in 2007 to 2010 year round during AIV surveillance programs in Canada and the United States. Our analyses revealed that during late summer staging (July-August) and fall migration (September-October), hatch year (HY) birds were more likely to be infected than after hatch year (AHY) birds, however there was no difference between age categories for the remainder of the year (winter, spring migration, and breeding period), likely due to maturing immune systems and newly acquired immunity of HY birds. Probability of infection increased non-linearly with latitude, and was highest in late summer prior to fall migration when densities of birds and the proportion of susceptible HY birds in the population are highest. Birds in the Central and Mississippi flyways were more likely to be infected compared to those in the Atlantic flyway. Seasonal cycles and spatial variation of AIV infection were largely driven by the dynamics of AIV infection in HY birds, which had more prominent cycles and spatial variation in infection compared to AHY birds. Our results demonstrate demographic as well as seasonal, latitudinal and flyway trends across Canada and the US, while illustrating the importance of migratory host life cycle and age in driving cyclical patterns of prevalence.

Histological lesions associated with Eucoleus sp. infection of the non-glandular stomach were discovered in a wild, urban population of Norway rats (Rattus norvegicus) trapped over a 1-year period in Vancouver, Canada. Four distinct categories of histological lesions in the non-glandular stomach were identified in association with infection in a sample of 183 rats. The apparent prevalence of Eucoleus sp. in the upper gastrointestinal tract (ventral tongue, oropharynx, esophagus and non-glandular stomach) was 43.1% (79/183). Infection with Eucoleus sp. was significantly associated with hyperkeratosis, mucosal hyperplasia, keratin pustules and submucosal inflammation in the non-glandular stomach (P < 0.05). Eucoleus sp. infection and/or related stomach pathology was present in 135/183 (73.8%) of rats. Statistical analysis showed the odds of being affected by Eucoleus sp. or associated stomach pathology were greater in heavier (OR = 1.06, 95% CI = 1.00–1.12) and sexually mature rats (OR = 4.64, 95% CI = 1.23–17.10). Eucoleus sp. infection is common in wild rats in Vancouver and induces substantial host response. The impact of Eucoleus sp. and associated lesions on the health of individual rats and the population as a whole remains to be investigated.

Wild aquatic birds are recognized as the natural reservoir of avian influenza A viruses (AIV), but across high and low pathogenic AIV strains, scientists have yet to rigorously identify most competent hosts for the various subtypes. We examined 11,870 GenBank records to provide a baseline inventory and insight into patterns of global AIV subtype diversity and richness. Further, we conducted an extensive literature review and communicated directly with scientists to accumulate data from 50 non-overlapping studies and over 250,000 birds to assess the status of historic sampling effort. We then built virus subtype sample-based accumulation curves to better estimate sample size targets that capture a specific percentage of virus subtype richness at seven sampling locations. Our study identifies a sampling methodology that will detect an estimated 75% of circulating virus subtypes from a targeted bird population and outlines future surveillance and research priorities that are needed to explore the influence of host and virus biodiversity on emergence and transmission.

Capillaria hepatica is a parasitic nematode that infects the liver of rats (Rattus spp.), and occasionally other mammalian species, including humans. Despite its broad geographic distribution and host range, the ecology of this parasite remains poorly understood. We characterized the ecology of C. hepatica in urban Norway rats (Rattus norvegicus) in Vancouver, Canada. The overall prevalence of C. hepatica among Norway rats was 36% (241/671); however, there was significant variation in prevalence among city blocks. Using a generalized linear mixed model to control for clustering by block (where OR is odds ratio and CI is confidence interval), we found C. hepatica infection was negatively associated with season (spring [OR=0.14, 95% CI=0.05-0.39]; summer [OR=0.14, 95% CI=0.03-0.61]; winter [OR=0.34, 95% CI=0.13-0.84], compared to fall) and positively associated with sexual maturity (OR: 7.29, 95% CI=3.98-13.36) and presence of cutaneous bite wounds (OR=1.87, 95% CI=1.11-3.16). Our understanding of the ecology of C. hepatica in rats is hindered by a paucity of data regarding the main mechanisms of transmission (e.g., environmental exposure vs. active cannibalism). However, associations among infection, season, maturity, and bite wounds could suggest that social interactions, possibly including cannibalism, may be important in transmission.

The geographic and host distribution, prevalence and genotypes of Echinococcus canadensis in wild ungulates in Canada are described to better understand the significance for wildlife and public health. We observed E. canadensis in 10.5% (11/105) of wild elk (wapiti; Cervus canadensis) in Riding Mountain National Park, Manitoba, examined at necropsy, over two consecutive years (2010–2011). Molecular characterization of hydatid cyst material from these elk, as well as three other intermediate wildlife host species, was based on sequence of a 470bp region of the NADH dehydrogenase subunit 1 (NAD1) mitochondrial gene. In moose [Alces alces], elk, and caribou [Rangifer tarandus] from northwestern Canada, the G10 genotype was the only one present, and the G8 genotype was detected in a muskox (Ovibos moschatus) from northeastern Canada. On a search of the national wildlife health database (1992–2010), cervids with hydatid cysts were reported in all provinces and territories except the Atlantic provinces, from which wolves [Canis lupis] are historically absent. Of the 93 cervids with records of hydatid cysts, 42% were elk, 37% were moose, 14% were caribou, and 6% were white-tailed and mule deer [Odocoileus virginianus and Odocoileus hemonius]. In these animals, 83% of cysts were detected in lungs alone, 8% in both lungs and liver, 3% in liver alone, and 6% in other organs. These observations can help target surveillance programs and contribute to a better understanding of ecology, genetic diversity, and genotype pathogenicity in the Echinococcus granulosus species complex.

In 2007, we assessed whether trapping method influenced apparent prevalence of low pathogenic avian influenza viruses (AIV) in wild ducks sampled during Canada’s Inter-agency Wild Bird Influenza Survey. Combined cloacal and oropharyngeal swabs were collected from 514 ducks captured by bait trapping (356) and netting from airboats (158), and tested by real-time reverse transcriptase polymerase chain reaction for influenza type A viruses. When controlling for species and capture site, ducks caught in bait traps were 2.6 times more likely to test positive for AIV compared with those netted from airboats (95% CI=1.2–6.0). If bait trapping increases AIV transmission among artificially aggregated ducks, this could have important implications for interpretation of disease surveillance results and waterfowl management programs.

Muskoxen (Ovibos moschatus) are Arctic-adapted ruminants native to the Arctic regions of Canada, Alaska, and Greenland. Little is known about the serum biochemistry and serum cortisol of this species, or the effects of chemical immobilization on serum biochemical Parameters. This study aimed to describe blood chemistry parameters and cortisol levels in hunted, tame, and chemically immobilized muskoxen and to examine differences in blood chemistry parameters and levels of stress associated with different capture techniques. Serum was collected from 91 adult female muskoxen in northern Canada. For analysis, these muskoxen were classified into six groups, five of free-ranging muskoxen (10 animals shot from snowmobiles near Kugluktuk, Nunavut; 18 chemically immobilized from a helicopter near Kugluktuk; 8 chemically immobilized from a helicopter near Norman Wells, Northwest Territories; 17 shot from snowmobiles near Cambridge Bay, Nunavut; 33 chemically immobilized from a snowmobile near Kugluktuk) and one of tame muskoxen,(five tame animals maintained on pasture near Saskatoon, Saskatchewan). All samples were analyzed for cortisol, and 26 serum biochemistry parameters were measured in serum collected from three of the six groups (n = 36). Comparison of four groups showed that serum cortisol levels of muskoxen chemically immobilized from a helicopter near Kugluktuk were significantly higher (p < 0.05) than those of muskoxen chemically immobilized from snowmobiles or shot. A comparison of serum biochemistry from the groups of muskoxen shot and immobilized near Kugluktuk found that serum sodium, creatinine, phosphorus, magnesium, and creatine kinase were significantly higher (p < 0.05) in hunted muskoxen than in chemically immobilized animals, while urea, glucose and gamma glutamyl transferase were significantly higher (p < 0.05) in immobilized muskoxen. Most serum biochemical parameters, however, were similar to those of captive muskoxen. This evidence of differences between hunted and immobilized muskoxen in several serum biochemistry parameters will contribute to further research on the effects of immobilization and other health assessments in this species.

This study evaluated the use of house sparrow (Passer domesticus) nestlings as sentinels of West Nile virus (WNV) in the prairie grasslands of Saskatchewan. In the summer of 2006, 600 house sparrow nestlings were collected and pooled tissues tested by reverse transcriptase-polymerase chain reaction. All tested negative for WNV. During the same period, no WNV was detected by mosquito surveillance in the study area and 15 WNV-infected pools were collected from the nearby city of Estevan. Six percent of avian carcasses collected from Regina, a city 100 km from the study area in the same ecozone, were infected with WNV. In 2007, 200 house sparrow nestlings were collected and 4 tested positive for WNV, a prevalence of 2%. Ninety-seven house sparrow eggs were also collected and WNV antibodies were measured in the yolk. Seven eggs had measurable titers, a prevalence of 7.2%. Combined WNV surveillance showed high levels of WNV transmission in 2007; 112 WNV-infected mosquito pools were collected from nearby cities of Estevan and Weyburn, and the proportion of WNV infected avian carcasses from Regina was 78%. There were 1456 human cases of WNV in Saskatchewan in 2007, compared to 19 cases in 2006. The study concluded that house sparrow nestlings are not useful as an early warning of WNV circulation, or as a measure of the intensity of WNV activity in the prairie grasslands. Also, the study determined that maternally derived antibody did not have a significant limiting effect on WNV transmission to house sparrow nestlings in 2007, a year of epidemic WNV activity in the study area.

It is PrioNet's vision to build a network that shapes and sustains prion research in Canada, translating basic science into accessible socioeconomic benefits for global betterment. PrioNet's research is developing surveillance measures, diagnostic tools, vaccines, and potential therapies and determining the various impacts of prion diseases on people. PrioNet seeks to integrate scientifically informed risk management strategies and to use this knowledge to address ongoing problems posed by bovine spongiform encephalopathy (BSE), the gathering crisis of chronic wasting disease (CWD), emerging issues of human prion disease, and basic scientific understanding of the nature of prions. PrioNet is strategically responding to prion threats by focusing its network of highly accomplished researchers and trainees to implement integrated risk management strategies that could not be supported by other mechanisms.

Surveillance for avian influenza viruses in wild birds was initiated in Canada in 2005. In 2006, in order to maximize detection of highly pathogenic avian influenza viruses, the sampling protocol used in Canada's Inter-agency Wild Bird Influenza Survey was changed. Instead of collecting a single cloacal swab, as previously done in 2005, cloacal and oropharyngeal swabs were combined in a single vial at collection. In order to compare the two sampling methods, duplicate samples were collected from 798 wild dabbling ducks (tribe Anatini) in Canada between 24 July and 7 September 2006. Low pathogenic avian influenza viruses were detected significantly more often (P<0.0001) in combined oropharyngeal and cloacal samples (261/798, 33%) than in cloacal swabs alone (205/798, 26%). Compared to traditional single cloacal samples, combined samples improved virus detection at minimal additional cost.

Five genera of potentially zoonotic bacteria and parasites were detected in environmentally collected fecal samples from a remote indigenous community in Northern Saskatchewan, Canada. Organisms identified include Toxocara canis, Echniococcus granulosus, Giardia duodenalis, Cryptosporidium spp., and Campylobacter spp. The prevalence and intensity of Giardia spp. and Campylobacter spp. in fecal samples was particularly remarkable. Three-quarters of samples tested contained at least one zoonotic species of Campylobacter, and C. jejuni-containing feces had an average of 2.9 x 10(5) organisms/g. Over one-half of samples tested contained Giardia spp. with an average of 9,266 cysts/g. Zoonotic G. duodenalis Assemblage A was the only Giardia spp. genotype identified. These data suggest that canine feces have the potential to pose a significant health risk to Canadians in rural and remote indigenous communities.

Within a remote Canadian Indigenous community, at least 11* of people had antibodies against Echinococcus granulosus and E. granulosus eggs were detected in 6* of environmentally collected canine fecal samples. Dog ownership, hunting, and trapping were not risk factors for seropositivity, suggesting that people are most likely exposed to E. granulosus through indirect contact with dog feces in the environment. In this situation, human exposure could be most effectively curtailed by preventing consumption of cervid viscera by free-roaming dogs.

PrioNet Canada's strength in basic, applied, and social research is helping to solve the food, health safety, and socioeconomic problems associated with prion diseases. Prion diseases are transmissible, fatal neurodegenerative diseases of humans and animals. Examples of prion diseases include bovine spongiform encephalopathy (BSE, commonly known as "mad cow" disease), Creutzfeldt-Jakob disease in humans, and chronic wasting disease (CWD) in deer and elk. As of March 31, 2008, PrioNet's interdisciplinary network included 62 scientific members, 5 international collaborators, and more than 150 students and young professionals working in partnership with 25 different government, nongovernment, and industry partners. PrioNet's activities are developing strategies based on a sustained, rational approach that will mitigate, and ultimately control, prion diseases in Canada.