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Sampling of sea ducks for influenza A viruses in Alaska during winter provided no evidence for an epidemiologic peak of infection. Isolates were recovered, however, that provide information on viral diversity and dispersal that may not be realized through sampling efforts focused on other avian taxa.
Detection of West Nile virus (WNV) in ducks has been reported in North America in isolated cases of mortality in wild waterbirds and following outbreaks in farmed ducks. Although the virus has been noted as an apparent incidental finding in several species of ducks, little is known about the prevalence of exposure or the outcome of infection with WNV in wild ducks in North America. From 2004–06, we collected sera from 1,406 wild-caught American Wigeon ( Anas americana ), Mallard ( Anas platyrhynchos ), and Northern Pintail ( Anas acuta ) ducks at national wildlife refuges (NWRs) in North Dakota and Wood Ducks ( Aix sponsa ) at NWRs in South Carolina and Tennessee. We measured the prevalence of previous exposure to WNV in these ducks by measuring WNV antibodies and evaluated variation in exposure among species, age, and year. Additionally, we evaluated the performance of a commercial antibody to wild bird immunoglobulin in duck species that varied in their phylogenetic relatedness to the bird species the antibody was directed against. As determined by a screening immunoassay and a confirmatory plaque reduction neutralization assay, the prevalence of WNV antibody was 10%. In light of experimental studies that show ducks to be relatively resistant to mortality caused by WNV, the antibody prevalence we detected suggests that wild ducks may be less-frequently exposed to WNV than expected for birds inhabiting wetlands where they may acquire infection from mosquitoes.
West Nile virus (WNV) spread to the US western plains states in 2003, when a significant mortality event attributed to WNV occurred in Greater Sage-grouse ( Centrocercus urophasianus ). The role of avian species inhabiting sagebrush in the amplification of WNV in arid and semiarid regions of the North America is unknown. We conducted an experimental WNV challenge study in Vesper Sparrows ( Pooecetes gramineus ), a species common to sagebrush and grassland habitats found throughout much of North America. We found Vesper Sparrows to be moderately susceptible to WNV, developing viremia considered sufficient to transmit WNV to feeding mosquitoes, but the majority of birds were capable of surviving infection and developing a humoral immune response to the WNV nonstructural 1 and envelope proteins. Despite clearance of viremia, after 6 mo, WNV was detected molecularly in three birds and cultured from one bird. Surviving Vesper Sparrows were resistant to reinfection 6 mo after the initial challenge. Vesper sparrows could play a role in the amplification of WNV in sagebrush habitat and other areas of their range, but rapid clearance of WNV may limit their importance as competent amplification hosts of WNV.
Toxoplasma gondii is a protozoan parasite transmitted by domestic cats ( Felis catus ) that has historically caused mortality in native Hawaiian birds. To estimate how widespread exposure to the parasite is in nene (Hawaiian Geese, Branta sandvicensis ), we did a serologic survey for T. gondii antibody and genetically characterized parasite DNA from the tissues of dead birds that had confirmed infections by immunohistochemistry. Of 94 geese sampled, prevalence on the island of Kauai, Maui, and Molokai was 21% ( n =42), 23% ( n =31), and 48% ( n =21), respectively. Two new T. gondii genotypes were identified by PCR-restriction fragment length polymorphism from four geese, and these appeared segregated geographically. Exposure to T. gondii in wild nene is widespread and, while the parasite is not a major cause of death, it could have sublethal or behavioral effects. How to translate such information to implement effective ways to manage feral cats in Hawaii poses challenges.
Eight Bald Eagle ( Haliaeetus leucocephalus ) nestlings heavily infested with larval ticks were found in or under a nest near the confluence of the Verde and Salt rivers in Arizona in 2009-11. The 8-12-wk-old nestlings were slow to respond to stimuli and exhibited generalized muscle weakness or paresis of the pelvic limbs. Numerous cutaneous and subcutaneous hemorrhages were associated with sites of tick attachment. Ticks were identified as Argas radiatus and Argas ricei . Treatment with acaricides and infection with West Nile virus (WNV) may have confounded the clinical presentation in 2009 and 2010. However, WNV-negative birds exhibited similar signs in 2011. One nestling recovered from paresis within 36 h after the removal of all adult and larval ticks (>350) and was released within 3 wk. The signs present in the heavily infested Bald Eagle nestlings resembled signs associated with tick paralysis, a neurotoxin-mediated paralytic syndrome described in mammals, reptiles, and wild birds (though not eagles). Removal of the infested nest and construction of a nest platform in a different tree was necessary to break the cycle of infection. The original nesting pair constructed a new nest on the man-made platform and successfully fledged two Bald Eagles in 2012.
A recent outbreak of beak deformities among resident birds in Alaska has raised concern about environmental contamination as a possible underlying factor. We measured whole blood concentrations of 30 essential and nonessential elements to determine whether any were associated with beak deformities in Northwestern Crows ( Corvus caurinus ). We tested for differences between 1) adults with versus those without beak deformities and 2) unaffected adults versus juveniles. Crows with beak deformities had slightly higher levels of barium, molybdenum, and vanadium (all P <0.05), but concentrations were generally low and within the range of values reported from other apparently healthy wild birds. Concentrations of several elements, including selenium, were higher in birds without versus birds with beak deformities (all P <0.05), a difference that may be explained in part by compromised foraging ability associated with the deformities. Adult crows had higher concentrations of cadmium, silicon, and zinc than juveniles (all P <0.05), although differences were relatively small and values were similar to those from other wild birds. Our results suggest that neither selenium nor other tested elements are likely to be causing beak deformities in Alaskan crows. We also provide the first data on elemental concentrations in Northwestern Crows. Levels of selenium far exceeded those typically found in passerine birds and were similar to those in marine-associated waterfowl, suggesting that background levels should be interpreted relative to a species's environment.
Between 1998 and 2014, recurrent mortality events were reported in the Dresser's subspecies of the Common Eider ( Somateria mollissima dresseri ) on Cape Cod, Massachusetts, USA near Wellfleet Harbor. The early die-offs were attributed to parasitism and emaciation, but beginning in 2006 a suite of distinct lesions was observed concomitant with the isolation of a previously unknown RNA virus. This novel pathogen was identified as an orthomyxovirus in the genus Quaranjavirus and was named Wellfleet Bay virus (WFBV). To assess evidence of exposure to this virus in Common Eiders, we conducted a longitudinal study of the prevalence of WFBV antibodies at multiple locations from 2004–14; we collected 2,258 serum samples from six locations and analyzed each using a microneutralization assay. Results corroborate the emergence of WFBV in 2006 based on the first detection of antibodies in that year. Significantly higher prevalence was detected in Common Eiders sampled in Massachusetts compared to those in Maine, Nova Scotia, and Québec. For birds breeding and wintering in Massachusetss, viral exposure varied by age, sex, and season of sampling, and prevalence by season and sex were highly interrelated with greater numbers of antibody-positive males in the autumn and females in the spring. No evidence of viral exposure was detected in the Northern subspecies ( Somateria mollissima borealis ). Among the locations sampled, Massachusetts appears to be the epicenter of Common Eider exposure to WFBV. Further research is warranted to understand the factors controlling the epidemiology of WFBV in Massachussetts, including those that may be limiting geographic expansion of this virus.
Few studies have evaluated how wetland and forest characteristics influence the prevalence of meningeal worm ( Parelaphostrongylus tenuis ) infection of deer throughout the grassland biome of central North America. We used previously collected, county-level prevalence data to evaluate associations between habitat characteristics and probability of meningeal worm infection in white-tailed deer ( Odocoileus virginianus ) across eastern South Dakota, US. The highest-ranked binomial regression model for detecting probability of meningeal worm infection was spring temperature + summer precipitation + percent wetland; weight of evidence ( w i =0.71) favored this model over alternative models, though predictive capability was low (Receiver operating characteristic=0.62). Probability of meningeal worm infection increased by 1.3- and 1.6-fold for each 1-cm and 1-C increase in summer precipitation and spring temperature, respectively. Similarly, probability of infection increased 1.2-fold for each 1% increase in wetland habitat. Our findings highlight the importance of wetland habitat in predicting meningeal worm infection across eastern South Dakota. Future research is warranted to evaluate the relationships between climatic conditions (e.g., drought, wet cycles) and deer habitat selection in maintaining P. tenuis along the western boundary of the parasite.
We evaluated the potential transmission of avian influenza viruses (AIV) in wildlife species in three settings in association with an outbreak at a poultry facility: 1) small birds and small mammals on a poultry facility that was affected with highly pathogenic AIV (HPAIV) in April 2015; 2) small birds and small mammals on a nearby poultry facility that was unaffected by HPAIV; and 3) small birds, small mammals, and waterfowl in a nearby natural area. We live-captured small birds and small mammals and collected samples from hunter-harvested waterfowl to test for active viral shedding and evidence of exposure (serum antibody) to AIV and the H5N2 HPAIV that affected the poultry facility. We detected no evidence of shedding or specific antibody to AIV in small mammals and small birds 5 mo after depopulation of the poultry. We detected viral shedding and exposure to AIV in waterfowl and estimated approximately 15% viral shedding and 60% antibody prevalence. In waterfowl, we did not detect shedding or exposure to the HPAIV that affected the poultry facility. We also conducted camera trapping around poultry carcass depopulation composting barns and found regular visitation by four species of medium-sized mammals. We provide preliminary data suggesting that peridomestic wildlife were not an important factor in the transmission of AIV during the poultry outbreak, nor did small birds and mammals in natural wetland settings show wide evidence of AIV shedding or exposure, despite the opportunity for exposure.
In 2013 a novel avian influenza H7N9 virus was isolated from several critically ill patients in China, and infection with this virus has since caused more than 200 human deaths. Live poultry markets are the likely locations of virus exposure to humans. Peridomestic avian species also may play important roles in the transmission and maintenance of H7N9 at live poultry markets. We experimentally challenged wild European Starlings ( Sturnus vulgaris ) with the novel H7N9 virus and measured virus excretion, clinical signs, and infectious dose. We found that European Starlings can be infected with this virus when inoculated with relatively high doses, and we predict that infected birds excrete sufficient amounts of virus to transmit to other birds, including domestic chickens. Infected European Starlings showed no clinical signs or mortality after infection with H7N9. This abundant peridomestic bird may be a source of the novel H7N9 virus in live poultry markets and may have roles in virus transmission to poultry and humans.
We measured serum chemistries in wild Black-capped Chickadees ( Poecile atricapillus ) from Alaska to test for potential differences associated with beak deformities characteristic of avian keratin disorder. Lower uric acid in affected birds was the only difference detected between groups, although sample sizes were small. This difference could be associated with fasting or malnutrition in birds with beak deformities, but it is challenging to interpret its biologic significance without reference values. Black-capped Chickadees had high levels of aspartate aminotransferase, lactate dehydrogenase, and creatine kinase relative to reference values for companion birds. However, all serum chemistry parameters from our study were within the range of values reported from other apparently healthy wild-caught birds.
West Nile virus (WNV) was first detected in New York in 1999 and, during its expansion across the continental US, southern Canada, and Mexico, members of the Corvidae (ravens, crows, magpies, and jays) were frequently infected and highly susceptible to the virus. As part of a behavioral study of Steller's Jays ( Cyanocitta stelleri ) conducted from 2011–2014 in the coastal California counties of San Mateo and Santa Cruz, 380 Steller's Jays were captured and tested for antibodies to WNV. Using the wild bird IgG enzyme linked immunoassay, we failed to detect antibodies to WNV, indicating either that there was no previous exposure to the virus or that exposed birds had died.
We determined reference intervals for nine serum biochemistries in samples from 329 molting, after-hatch-year, Pacific Black Brant ( Branta bernicla nigricans ) in Alaska, US. Cholesterol and nonesterified fatty acids differed by sex, but no other differences were noted.
Bats occupying hibernacula during summer are exposed to Pseudogymnoascus destructans ( Pd ), the causative agent of white-nose syndrome (WNS), and may contribute to its dispersal. Furthermore, equipment and clothing exposed to cave environments are a potential source for human-assisted spread of Pd . To explore dispersal hazards for Pd during the nonhibernal season, we tested samples that were collected from bats, the environment, and equipment at hibernacula in the eastern US between 18 July–22 August 2012. Study sites included six hibernacula known to harbor bats with Pd with varying winter-count impacts from WNS and two hibernacula (control sites) without prior history of WNS. Nucleic acid from Pd was detected from wing-skin swabs or guano from 40 of 617 bats (7% prevalence), including males and females of five species at five sites where WNS had previously been confirmed as well as from one control site. Analysis of guano collected during summer demonstrated a higher apparent prevalence of Pd among bats (17%, 37/223) than did analysis of wing-skin swabs (1%, 4/617). Viable Pd cultured from wing skin (2%, 1/56) and low recapture rates at all sites suggested bats harboring Pd during summer could contribute to pathogen dispersal. Additionally, Pd DNA was detected on clothing and trapping equipment used inside and near hibernacula, and Pd was detected in sediment more readily than in swabs of hibernaculum walls. Statistically significant differences in environmental abundance of Pd were not detected among sites, but prevalence of Pd differed between sites and among bat species. Overall, bats using hibernacula in summer can harbor Pd on their skin and in their guano, and demonstration of Pd on clothing, traps, and other equipment used at hibernacula during summertime within the WNS-affected region indicates risk for pathogen dispersal during the nonhibernal season.
Oral papillomatosis was diagnosed in a gray wolf ( Canis lupus ) with sarcoptic mange from Minnesota, USA found dead in February 2015. Intranuclear inclusion bodies were evident histologically, and papillomaviral antigens were confirmed using immunohistochemistry. Sequencing of the L1 papillomavirus gene showed closest similarity to Lambdapapillomavirus 2 .
From 12 May 2013 to 29 May 2013, the Gull-billed Tern ( Gelochelidon nilotica ) colony at the San Diego Bay National Wildlife Refuge, California, experienced a mass die-off of at least 92 adults, representing 71–92% of the breeding population on the US west coast. Cause of death was determined to be peritonitis due to perforations of the intestine by a large quantity of acanthocephala ( Profilicolis [= Polymorphus ] altmani ). This is a unique report of P. altmani infecting G. nilotica , and a report of a great impact to a tern population in southern California. Mole crabs ( Emerita analoga ), the intermediate host for P. altmani and a major component of the Gull-billed Tern diet in San Diego, were found in the stomachs of necropsied terns along with cystacanths, and are the presumed source of the parasite infection. The tern's dietary reliance upon mole crabs likely amplified parasite transmission and infection. We suggest additional research to determine factors that influence parasite infection of intermediate and definitive hosts, particularly mole crabs, given that they are a vital resource for migrating birds within the coastal zone.
On 16 September 2015, a red tide ( Karenia brevis ) bloom impacted coastal areas of Padre Island National Seashore Park. Two days later and about 0.9 km inland, 30–40 adult green tree frogs ( Hyla cinerea ) were found dead after displaying tremors, weakness, labored breathing, and other signs of neurologic impairment. A rainstorm, accompanied by high winds, rough surf, and high tides, which could have aerosolized brevetoxin, occurred on the morning of the mortality event. Frog carcasses were healthy but contained significant brevetoxin in tissues. Tissue brevetoxin was also found in two dead or dying spotted ground squirrels ( Xerospermophilus spilosoma ) and a coyote ( Canis latrans ). Rainwater collected from the location of the mortality event contained brevetoxin. Mortality of green tree frog and ground squirrel mortality has not been previously attributed to brevetoxin exposure and such mortality suggested that inland toxin transport, possibly through aerosols, rainfall, or insects, may have important implications for coastal species.
We confirmed safety and immunogenicity of mass-produced vaccine baits carrying an experimental, commercial-source plague vaccine (RCN-F1/V307) expressing Yersinia pestis V and F1 antigens. Forty-five juvenile black-tailed prairie dogs ( Cynomys ludovicianus ) were randomly divided into three treatment groups ( n =15 animals/group). Animals in the first group received one standard-dose vaccine bait (5×10 7 plaque-forming units [pfu]; STD). The second group received a lower-dose bait (1×10 7 pfu; LOW). In the third group, five animals received two standard-dose baits and 10 were left untreated but in contact. Two vaccine-treated and one untreated prairie dogs died during the study, but laboratory analyses ruled out vaccine involvement. Overall, 17 of 33 (52%; 95% confidence interval for binomial proportion [bCI] 34−69%) prairie dogs receiving vaccine-laden bait showed a positive anti-V antibody response on at least one sampling occasion after bait consumption, and eight (24%; bCI 11–42%) showed sustained antibody responses. The STD and LOW groups did not differ ( P ≥0.78) in their proportions of overall or sustained antibody responses after vaccine bait consumption. Serum from one of the nine (11%; bCI 0.3–48%) surviving untreated, in-contact prairie dogs also had detectable antibody on one sampling occasion. We did not observe any adverse effects related to oral vaccination.