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At least 847 records · Page 47Linked to original sources
USGS2019

Review: Endophytic microbes and their potential applications in crop management

Endophytes are microbes (mostly bacteria and fungi) present in plants. Endophytic microbes are often functional in that they may carry nutrients from the soil into plants, modulate plant development, increase stress tolerance of plants, suppress virulence in pathogens, increase disease resistance in plants, and suppress development of competitor plant species. Endophytic microbes have been shown: 1) obtain nutrients in soils and transfer nutrients to plants in the rhizophagy cycle and other nutrient‐transfer symbioses; 2) increase plant growth and development; 3) reduce oxidative stress of hosts; 4) protect plants from disease; 5) deter feeding by herbivores; and 6) suppress growth of competitor plant species. Because of the effective functions of endophytic microbes, we suggest that endophytic microbes may significantly reduce use of agrochemicals (fertilizers, fungicides, insecticides, and herbicides) in the cultivation of crop plants. The loss of endophytic microbes from crop plants during domestication and long‐term cultivation could be remedied by transfer of endophytes from wild relatives of crops to crop species. Increasing atmospheric carbon dioxide levels could reduce the efficiency of the rhizophagy cycle due to repression of reactive oxygen used to extract nutrients from microbes in roots.

Pest Management Science↗
USGS2019

Nonlethal detection of Asian fish tapeworm in the federally-endangered Humpback Chub using a molecular screening tool

Optimal spawning habitat of federally endangered Humpback Chub Gila cypha exists within the Little Colorado River; however, temperatures in the Little Colorado River are also ideal for proliferation of the invasive pathogenic Asian fish tapeworm Schyzocotyle acheilognathi . The current standard for positive identification of the parasite is necropsy and visual examination of the gut via microscopy, a methodology undesirable for assessing infection in endangered fishes. A swab taken at the rectum of the fish and analyzed using a novel DNA primer targeting the cestode cytochrome oxidase I subunit mtDNA gene region offers a convenient nonlethal sampling tool. To validate the nonlethal methodology, primer sensitivity (51.9%) and specificity (79.5%) were calculated by exposing captive fish to the parasite and comparing results using the lethal standard method (i.e., visual examination). Subsequently, we utilized this nonlethal methodology to address prevalence of infection and infection frequency across a range of size-classes in a wild population of Humpback Chub and addressed possible patterns and mechanisms of infection in the Little Colorado River. When wild Humpback Chub were screened for infection prevalence in spring 2015 (21.4%, n = 140) and fall 2015 (6.6%, n = 258), the relative frequency of infection was highest in juveniles and subadult fish (200–300 mm). Elevated levels of infection near the major spawning grounds of Humpback Chub in the Little Colorado River promote parasitic infection, which may continue to persist without treatment or actions to control infections. We demonstrated that rectal swabs, in conjunction with PCR and primer-specific identification, offer a time-efficient nonlethal method to detect infection of Asian fish tapeworm in an endangered fish.

Transactions of the American Fisheries Society↗
USGS2026

Feathers and flu: Identifying data gaps in avian influenza host dynamics to prioritize wildlife conservation

Highly pathogenic avian influenza viruses (HPAIV) have had disastrous, worldwide effects on wild birds and domestic poultry since the emergence of the A/goose/Guangdong/1/1996 (Gs/GD/96) lineage. The currently circulating H5N1 clade 2.3.4.4b has an expanded set of susceptible hosts, including many migratory wild birds, and is associated with higher transmission rates, increased susceptibility among wild bird hosts, and a greater number of wildlife reservoirs. Certain wild bird life-history strategies and behaviors have been suggested to explain avian hosts’ susceptibility and exposure to HPAIV. These biological traits include gregariousness, such as colonial nesting and mixed flock foraging, predation or scavenging on wild birds, and association with aquatic habitats. Variation in host infection responses (e.g., infectability, shedding rates and duration, mortality rate, antibody development) informs the overall infection risk across avian species, yet the specific role of biological traits is often inconsistent and unclear across taxa. Moreover, the interactions and potential compounding effects among these biological traits remain largely unknown. To develop a more holistic understanding of cumulative risk across bird species, we integrate existing information on infection risk factors (i.e., susceptibility, immunological response, and behavioral traits) into a qualitative multivariate analysis. This approach enabled us to examine how infection risk factors relate to biological traits (e.g., phylogeny, physiology, behavior, species range) and to begin disentangling their complex interactions. We quantified and summarized these risk factors across host species and qualitatively ranked species by their viral responses along a proposed HPAIV response continuum, guided by expectations of traits and metrics associated with competence or vulnerability to HPAIV. In doing so, we aimed to better understand how viral responses and biological traits synergistically interact to influence cumulative risk across wild bird species. This work broadly expands on the previous avian influenza literature, which has focused on Anseriformes and Charadriiformes as primary viral reservoirs. We tie our findings to effective disease management responses with links to risk components, including descriptions of potential surveillance strategies applied to research and One Health goals, as well as a fuller understanding of how resources may be better deployed for rapid response when spillovers do inevitably occur. Additionally, we identified numerous areas where vital epidemiological information is lacking to best characterize the spread of these viruses. Ultimately, this improved understanding will help identify and inform disease management needs and decision making.

Wildlife Monographs↗
USGS2020

Gene transcript profiling in desert bighorn sheep

Respiratory disease is a key factor affecting the conservation and recovery of bighorn sheep ( Ovis canadensis ) populations. Innovative, minimally invasive tools such as gene transcription–based diagnostics have the potential to improve our understanding of the broad range of factors that can affect the health of wild sheep. Evaluation of transcript levels for genes representative of multiple internal systems enables measurement of physiological responses of individuals as well as populations to environmental stressors such as pathogens, nutritional deficiency, or contaminants. We developed real‐time polymerase chain reaction assays for 14 genes of interest representing systems including inflammation, cell signaling, detoxification, antiviral, antibacterial, or general stress. Initial results from desert bighorn sheep ( O. c. nelsoni ) sampled from the River, Muddy, and Bare mountains as well as from the Pintwater Range, in southern Nevada, USA, indicated unique transcript profiles associated with each population. This initial study provides the framework from which controlled variable or longitudinal studies can be made, thus augmenting the potential to inform management actions in the future.

Nevada↗
USGS1997

An evaluation of the rust fungus Gymnoconia nitensas a potential biological control agent for alien Rubus species in Hawaii

The rust fungus Gymnoconia nitens infects blackberry ( Rubus argutus ) systemically in regions of the continental United States, producing bright yellow–orange masses of spores on newly developing floricanes during springtime. In tests to determine the suitability of this rust as a biological control agent for R. penetrans in Hawaii, a species now thought to be conspecific with R. argutus, rooted cuttings of the Hawaiian plants were grown at North Carolina State University, inoculated, and observed. Other introduced weedy Rubus spp. in Hawaii, including R. ellipticus, R. rosifolius, and R. glaucus, as well as the two endemic species R. hawaiensis and R. macraei, also were inoculated. No species of Rubus are of commercial importance in Hawaii, but the protection of the native species, of which R. macraei is rare, was of utmost concern. The native Hawaiian species did not survive well in North Carolina in this study, however. Later availability of a plant pathogen containment laboratory in Hawaii enabled similar tests to be conducted at that facility. In addition to the above species, R. spectabilis (salmonberry), a species native to the Pacific Northwest with which the Hawaiian Rubus spp. are thought to share a common ancestor, was inoculated in Hawaii. Infection with G. nitens under natural field conditions becomes apparent only when sporulation occurs on floricanes the second year following infection. However, experimental inoculation led to early responses of chlorotic leaf flecking and puckering, leaf and stem contortion, and stem gall formation, indicating the sensitivity of R. penetrans (= R. argutus ), R. hawaiensis, and R. macraei to this rust. Apparent systemic infection also resulted in sporulation on one plant of R. macraei. Ability to attack the endemic species suggests that G. nitens would not be suitable for release in Hawaii as a biological control agent, at least on the islands with populations of the native species.

Hawaii↗
USGS2000

Fish DNA vaccine against infectious hematopoietic necrosis virus: efficacy of various routes of immunization

The DNA vaccine, pIHNVw-G, contains the gene for the glycoprotein (G) of the rhabdovirus infectious hematopoietic necrosis virus (IHNV), a major pathogen of salmon and trout. The relative efficacy of various routes of immunisation with pIHNVw-G was evaluated using 1.8 g rainbow trout fry vaccinated via intramuscular injection, scarification of the skin, intraperitoneal injection, intrabuccal administration, cutaneous particle bombardment using a gene gun, or immersion in water containing DNA vaccine-coated beads. Twenty-seven days after vaccination neutralising antibody titres were determined, and 2 days later groups of vaccinated and control unvaccinated fish were subjected to an IHNV immersion challenge. Results of the virus challenge showed that the intramuscular injection and the gene gun immunisation induced protective immunity in fry, while intraperitoneal injection provided partial protection. Neutralising antibodies were not detected in sera of vaccinated fish regardless of the route of immunisation used, suggesting that cell mediated immunity may be at least partially responsible for the observed protection.

Fish and Shellfish Immunology↗
USGS2015

Interactions of water quality and integrated groundwater management: Examples from the United States and Europe

Groundwater is available in many parts of the world, but the quality of the water may limit its use. Contaminants can limit the use of groundwater through concerns associated with human health, aquatic health, economic costs, or even societal perception. Given this broad range of concerns, this chapter focuses on examples of how water quality issues influence integrated groundwater management. One example evaluates the importance of a naturally occurring contaminant Arsenic (As) for drinking water supply, one explores issues resulting from agricultural activities on the land surface and factors that influence related groundwater management, and the last examines unique issues that result from human-introduced viral pathogens for groundwater-derived drinking water vulnerability. The examples underscore how integrated groundwater management lies at the intersections of environmental characterization, engineering constraints, societal needs, and human perception of acceptable water quality. As such, water quality factors can be a key driver for societal decision making.

Book chapter↗
USGS2016

Ecosystem impacts of exotic annual invaders in the genus Bromus

An understanding of the impacts of exotic plant species on ecosystems is necessary to justify and guide efforts to limit their spread, restore natives, and plan for conservation. Invasive annual grasses such as Bromus tectorum , B. rubens , B. hordeaceus , and B. diandrus (hereafter collectively referred to as Bromus ) transform the structure and function of ecosystems they dominate. Experiments that prove cause-and-effect impacts of Bromus are rare, yet inferences can be gleaned from the combination of Bromus -ecosystem associations, ecosystem condition before/after invasion, and an understanding of underlying mechanisms. Bromus typically establishes in bare soil patches and can eventually replace perennials such as woody species or bunchgrasses, creating a homogeneous annual cover. Plant productivity and cover are less stable across seasons and years when Bromus dominates, due to a greater response to annual climate variability. Bromus’ “flash” of growth followed by senescence early in the growing season, combined with shallow rooting and annual habit, may lead to incomplete use of deep soil water, reduced C sequestration, and accelerated nutrient cycling. Litter produced by Bromus alters nearly all aspects of ecosystems and notably increases wildfire occurrence. Where Bromus has become dominant, it can decrease soil stability by rendering soils bare for months following fire or episodic, pathogen-induced stand failure. Bromus-invaded communities have lower species diversity, and associated species tend to be generalists adapted to unstable and variable habitats. Changes in litter, fire, and soil properties appear to feedback to reinforce Bromus’ dominance in a pattern that portends desertification.

Book chapter↗
USGS2019

Historical range and variation (HRV)

Fire-prone landscapes are experiencing rapid and potentially persistent changes as the result of complex and potentially novel interactions of anthropogenic climate changes, shifting fire regimes, exotic plant, insect, and pathogen invasions, and industrial, agricultural, and urban development. Are these landscapes fully departed from historical conditions? Should they be managed as novel environments or as landscapes in transition? Historical range and variation is a benchmark representation of the conditions that describe fully functional, healthy ecosystems or landscapes. The HRV can provide an ecological reference against which contemporary and future conditions can be evaluated to determine status, trend, and magnitude of departure. This text describes the concepts of HRV, methods for developing HRV data sets, and application of HRV for fire management. We discuss the limitations of HRV, and its use under future climates that are no longer representative of historical conditions.

Book chapter↗
USGS2018

The aerosphere as a network connector of organisms and their diseases

Aeroecological processes, especially powered flight of animals, can rapidly connect biological communities across the globe. This can have profound consequences for evolutionary diversification, energy and nutrient transfers, and the spread of infectious diseases. The latter is of particular consequence for human populations, since migratory birds are known to host diseases which have a history of transmission into domestic poultry or even jumping to human hosts. In this chapter, we present a scenario under which a highly pathogenic avian influenza (HPAI) strain enters North America from East Asia via post-molting waterfowl migration. We use an agent-based model (ABM) to simulate the movement and disease transmission among 10 6 generalized waterfowl agents originating from ten molting locations in eastern Siberia, with the HPAI seeded in only ~10 2 agents at one of these locations. Our ABM tracked the disease dynamics across a very large grid of sites as well as individual agents, allowing us to examine the spatiotemporal patterns of change in virulence of the HPAI infection as well as waterfowl host susceptibility to the disease. We concurrently simulated a 12-station disease monitoring network in the northwest USA and Canada in order to assess the potential efficacy of these sites to detect and confirm the arrival of HPAI. Our findings indicated that HPAI spread was initially facilitated but eventually subdued by the migration of host agents. Yet, during the 90-day simulation, selective pressures appeared to have distilled the HPAI strain to its most virulent form (i.e., through natural selection), which was counterbalanced by the host susceptibility being conversely reduced (i.e., through genetic predisposition and acquired immunity). The monitoring network demonstrated wide variation in the utility of sites; some were clearly better at providing early warnings of HPAI arrival, while sites further from the disease origin exposed the selective dynamics which slowed the spread of the disease albeit with the result of passing highly virulent strains into southern wintering locales (where human impacts are more likely). Though the ABM presented had generalized waterfowl migration and HPAI disease dynamics, this exercise demonstrates the power of such simulations to examine the extremely large and complex processes which comprise aeroecology. We offer insights into how such models could be further parameterized to represent HPAI transmission risks as well as how ABMs could be applied to other aeroecological questions pertaining to individual-based connectivity.

Book chapter↗
USGS1989

Preliminary characterization of a virus causing infectious anemia among stocks of salmonid fish in the western United States

Since 1982, anemias occurring in stocks of yearling coho ( Oncorhynchus kisutch ) and chinook salmon (Oncorhynchus tshawytscha ) have been associated with serious losses at hatcheries in the Pacific Northwest, USA. The anemia is often accompanied by infections with external fungus (e.g. Saprolegnia) or the bacterial pathogens Cytophaga psychrophila or Renibacterium salmoninarum (Holt and Rohovec 1984, Leek 1987). The losses associated with the anemia are thought to be caused by these secondary infections. Blood smears that were made from anemic fish and stained with Giemsa or pinacyanol chloride showed erythrocytic inclusions ranging in size from 1 to 8 um and varying in number per cell. Thin sections of infected red blood cells (RBC) examined by electron microscopy revealed virus particles approximately 70 nm in diameter. The virions were scattered in the cytoplasm of the RBC or contained within membrane bound organelles. These virus particles were morphologically distinct from the iridovirus, erythrocytic necrosis virus (ENV), which is also associated with anemia (Holt and Rohovec 1984, Leek 1987). Evidence suggests that the etiological agent of this new anemic disease, termed erythrocytic inclusion body syndrome (EIBS) by Leek (1987), is a previously undescribed virus infecting salmon. The purpose of this study was to experimentally transmit the disease to healthy fish, to determine the blood parameters associated with infection, and to investigate the nature of the virus associated with EIBS.

Book chapter↗
USGS2002

Comparison of traditional and molecular methods for detection of Renibacterium salmoninarum

Bacterial kidney disease (BKD) caused by Renibacterium salmoninarum occurs in most parts of the world where wild or cultured salmonid fishes are present. Several extensive reviews have been written on the pathogen and the disease (Fryer and Sanders, 1981; Austin and Austin, 1987; Elliott et al ., 1989; Evelyn, 1993; Evenden et al ., 1993; Fryer and Lannan, 1993). Bacterial kidney disease can cause serious mortality in juvenile salmonids in both fresh water and seawater, and also in prespawning adults. Although the chronic nature of the disease has hindered accurate estimates of fish losses, particularly in feral fish populations, BKD is one the most important bacterial diseases affecting cultured salmonids, with reported losses as high as 80% in stocks of Pacific salmon ( Oncorhynchus spp.) and 40% in stocks of Atlantic salmon ( Salmo salar ) (Evenden et al ., 1993).

Book chapter↗
USGS1972

Fish rhabdoviruses: Morphology and ultrastructure of North American salmonid isolates

The morphology and ultrastructure of three North American salmonid pathogens, Oregon sockeye salmon, chinook salmon and infectious hematopoietic necrosis viruses, were examined by thin sectioning and negative staining after growth in fathead minnow cells at 10 ° C. The viruses matured at the plasma membrane of these cells. They were approximately 170 nm in length, 70 nm in width and had internal striations with a periodicity of 5.5nm. They were rounded on one end and planar on the other ( i.e. , bullet shaped). By morphological criteria, these viruses are rhabdoviruses with dimensions and ultrastructural features similar to vesicular stomatitis virus.

Archiv Fur Die Gesamte Virusforschung↗
USGS2007

A comparative analysis of polybrominated diphenyl ethers and polychlorinated biphenyls in southern sea otters that died of infectious diseases and noninfectious causes

Southern sea otters ( Enhydra lutris nereis ) from the California coast continue to exhibit a slower population regrowth rate than the population in Alaska. Infectious diseases have been identified as a frequent cause of death. Infectious diseases caused by varied pathogens including bacteria, fungi, and parasites were suggestive of compromised immunological health of mature animals in this population. To test the hypothesis that elevated exposure to immunotoxic contaminants such as polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) contribute to disease susceptibility via immunosuppression, we determined concentrations of PBDEs and PCBs in livers of 80 adult female sea otters that died of infectious diseases, noninfectious causes, or emaciation. Concentrations of PBDEs and PCBs in sea otter livers varied widely (10–26,800 ng/g and 81–210,000 ng/g, lipid weight, respectively) . Concentrations of PBDEs in sea otters were some of the highest values reported for marine mammals so far. Although PCB concentrations in sea otters have declined during 1992-2002, the mean concentration was at the threshold at which adverse health effects are elicited. Concentrations of PBDEs and PCBs were significantly correlated, suggesting co-exposure of these contaminants in sea otters. No significant association was found between the concentrations of PBDEs and the health status of sea otters. Concentrations of PCBs were significantly higher in otters in the infectious disease category than in the noninfectious category, suggesting an association between elevated PCB concentrations and infectious diseases in Southern sea otters.

Alaska, California↗
USGS2012

Free tropospheric transport of microorganisms from Asia to North America

Microorganisms are abundant in the troposphere and can be transported vast distances on prevailing winds. This study measures the abundance and diversity of airborne bacteria and fungi sampled at the Mt. Bachelor Observatory (located 2.7 km above sea level in North America) where incoming free tropospheric air routinely arrives from distant sources across the Pacific Ocean, including Asia. Overall deoxyribonucleic acid (DNA) concentrations for microorganisms in the free troposphere, derived from quantitative polymerase chain reaction assays, averaged 4.94 × 10(-5) ng DNA m(-3) for bacteria and 4.77 × 10(-3) ng DNA m(-3) for fungi. Aerosols occasionally corresponded with microbial abundance, most often in the springtime. Viable cells were recovered from 27.4 % of bacterial and 47.6 % of fungal samples (N = 124), with 49 different species identified by ribosomal DNA gene sequencing. The number of microbial isolates rose significantly above baseline values on 22-23 April 2011 and 13-15 May 2011. Both events were analyzed in detail, revealing distinct free tropospheric chemistries (e.g., low water vapor, high aerosols, carbon monoxide, and ozone) useful for ruling out boundary layer contamination. Kinematic back trajectory modeling suggested air from these events probably originated near China or Japan. Even after traveling for 10 days across the Pacific Ocean in the free troposphere, diverse and viable microbial populations, including presumptive plant pathogens Alternaria infectoria and Chaetomium globosum, were detected in Asian air samples. Establishing a connection between the intercontinental transport of microorganisms and specific diseases in North America will require follow-up investigations on both sides of the Pacific Ocean.

Microbial Ecology↗
USGS2017

Extensive shared polymorphism at non-MHC immune genes in recently diverged North American prairie grouse

Gene polymorphisms shared between recently diverged species are thought to be widespread and most commonly reflect introgression from hybridization or retention of ancestral polymorphism through incomplete lineage sorting. Shared genetic diversity resulting from incomplete lineage sorting is usually maintained for a relatively short period of time, but under strong balancing selection it may persist for millions of years beyond species divergence (balanced trans-species polymorphism), as in the case of the major histocompatibility complex (MHC) genes. However, balancing selection is much less likely to act on non-MHC immune genes. The aim of this study was to investigate the patterns of shared polymorphism and selection at non-MHC immune genes in five grouse species from Centrocercus and Tympanuchus genera. For this purpose, we genotyped five non-MHC immune genes that do not interact directly with pathogens, but are involved in signaling and regulate immune cell growth. In contrast to previous studies with MHC, we found no evidence for balancing selection or balanced trans-species polymorphism among the non-MHC immune genes. No haplotypes were shared between genera and in most cases more similar allelic variants sorted by genus. Between species within genera, however, we found extensive shared polymorphism, which was most likely attributable to introgression or incomplete lineage sorting following recent divergence and large ancestral effective population size (i.e., weak genetic drift). Our study suggests that North American prairie grouse may have attained relatively low degree of reciprocal monophyly at nuclear loci and reinforces the rarity of balancing selection in non-MHC immune genes.

Immunogenetics↗
USGS2015

Gene transcription in polar bears ( Ursus maritimus ) from disparate populations

Polar bears in the Beaufort (SB) and Chukchi (CS) Seas experience different environments due primarily to a longer history of sea ice loss in the Beaufort Sea. Ecological differences have been identified as a possible reason for the generally poorer body condition and reproduction of Beaufort polar bears compared to those from the Chukchi, but the influence of exposure to other stressors remains unknown. We use molecular technology, quantitative PCR, to identify gene transcription differences among polar bears from the Beaufort and Chukchi Seas as well as captive healthy polar bears. We identified significant transcriptional differences among a priori groups (i.e., captive bears, SB 2012, SB 2013, CS 2013) for ten of the 14 genes of interest (i.e., CaM, HSP70, CCR3, TGFβ, COX2, THRα, T-bet, Gata3, CD69, and IL17); transcription levels of DRβ, IL1β, AHR, and Mx1 did not differ among groups. Multivariate analysis also demonstrated separation among the groups of polar bears. Specifically, we detected transcript profiles consistent with immune function impairment in polar bears from the Beaufort Sea, when compared with Chukchi and captive polar bears. Although there is no strong indication of differential exposure to contaminants or pathogens between CS and SB bears, there are clearly differences in important transcriptional responses between populations. Further investigation is warranted to refine interpretation of potential effects of described stress-related conditions for the SB population.

Polar Biology↗
USGS2007

Bleaching increases likelihood of disease on Acropora palmatao (Lamarck) in Hawksnest Bay, St John, US Virgin Islands

Anomalously high water temperatures may enhance the likelihood of coral disease outbreaks by increasing the abundance or virulence of pathogens, or by increasing host susceptibility. This study tested the compromised-host hypothesis, and documented the relationship between disease and temperature, through monthly monitoring of Acropora palmata colonies from May 2004 to December 2006, in Hawksnest Bay, St John, US Virgin Islands (USVI). Disease prevalence and the rate of change in prevalence showed a positive linear relationship with water temperature and rate of change in water temperature, respectively, but only in 2005 during prolonged periods of elevated temperature. Both bleached and unbleached colonies showed a positive relationship between disease prevalence and temperature in 2005, but the average area of disease-associated mortality increased only for bleached corals, indicating host susceptibility, rather than temperature per se, influenced disease severity on A. palmata .

Virgin Islands↗