Michael Lawrence Kent

Oregon State University | OSU · Department of Microbiology

Objective Premature mortality of adult female Chinook Salmon Oncorhynchus tshawytscha is a major barrier to population recovery. The Willamette River basin, Oregon, typifies the problems that are faced by fishery managers in the Pacific Northwest (USA). Adult salmon are trapped and transported upstream of dams to access historical spawning grounds,...

Intestinal helminth parasite (IHP) infection induces alterations in the composition of microbial communities across vertebrates, although how gut microbiota may facilitate or hinder parasite infection remains poorly defined. In this work, we utilized a zebrafish model to investigate the relationship between gut microbiota, gut metabolites, and IHP...

Intestinal helminth parasite (IHP) infection induces alterations in the composition of microbial communities across vertebrates, although how gut microbiota may facilitate or hinder parasite infection remains poorly defined. In this work we utilized a zebrafish model to investigate the relationship between gut microbiota, gut metabolites, and IHP i...

Zebrafish ( Danio rerio ) is now the second most used animal model in biomedical research. As with other vertebrate models, underlying diseases and infections often impact research. Beyond mortality and morbidity, these conditions can compromise research end points by producing nonprotocol induced variation within experiments. Pseudoloma neurophili...

Objective Dams and reservoirs can alter juvenile growth and survival of migratory salmonids through several physical and biological mechanisms. Juvenile Chinook Salmon Oncorhynchus tshawytscha that are produced upstream of large hydropower dams may have associated passage mortality, but the reservoirs created by these dams can support rapid growth....

Progress in biomedical research requires rigorous studies and reproducible outcomes. However, despite recent achievements, standard reference diets (SRDs) for aquatic model organisms, vital for supporting scientific rigor and reproducibility, are yet to be adopted. At this workshop, we presented findings from a 7-month diet test study, tightly coor...

Here, we provide evidence that the freshwater parasitic copepod, Salmincola californiensis , acts as a vector for Aeromonas salmonicida. While investigating the effects of S. californiensis on Chinoook salmon ( Oncorhynchus tshawytscha ), we tangentially observed that fish infected with the copepod developed furunculosis, caused by A. salmonicida ....

Prespawn mortality (PSM) presents a major problem for the recovery of spring Chinook Salmon ( Oncorhynchus tshawytscha ) populations. In the Willamette River, Oregon, PSM exceeds 90% in some years but factors explaining it are not well understood. We examined intestinal tissue samples using histological slides from over 783 spring Chinook Salmon co...

Diet is an external factor that affects the physiological baseline of research animals. It can shape gut microbiome, which can impact the host. As a result, dietary variation can challenge experimental reproducibility and data integration across studies when not appropriately considered. To control for diet-induced variation, reference diets have b...

Background Despite the long-established importance of zebrafish (Danio rerio) as a model organism and their increasing use in microbiome-targeted studies, relatively little is known about how husbandry practices involving diet impact the zebrafish gut microbiome. Given the microbiome’s important role in mediating host physiology and the potential f...

The intestinal nematode Pseudocapillaria tomentosa in zebrafish (Danio rerio) causes profound intestinal lesions, emaciation and death and is a promoter of a common intestinal cancer in zebrafish. This nematode has been detected in zebrafish from about 15% of the laboratories. Adult worms are readily detected about 3 weeks after exposure by either...

Pacific salmon experience prolonged elevation in corticosteroid hormones during important life history events including migration, reproduction, and senescence. These periods of elevated corticosteroids correspond with changes to immunity and energy metabolism; therefore, fish may be particularly vulnerable to mortality at these times. Recent studi...

Background: Ongoing postoperative pain assessments are vital to optimizing pain management and attenuating the development of poor health outcomes after surgery. This study aimed to characterize acute multidimensional trajectories of pain impact on physical function, sleep, mood and stress and examine clinical characteristics and demographics asso...

Detecting the presence of important parasites within a host and its environment is critical to understanding the dynamics that influence a pathogen's ability to persist, while accurate detection is also essential for the implementation of effective control strategies. Pseudoloma neurophilia is the most common pathogen reported in zebrafish (Danio r...

Environmental DNA (eDNA) water assays are beginning to be implemented for many important pathogens in confined aquaculture systems. Recirculating systems are rapidly being developed for fin fish aquaculture. Zebrafish (Danio rerio) are reared in these systems, and Pseudoloma neurophilia (Microsporidia) represents a serious challenge for zebrafish r...

Climate changes can promote disease outbreaks, but their nature and potential impacts in remote areas have received little attention. In a hotspot of biodiversity on the West Antarctic Peninsula, which faces among the fastest changing climates on Earth, we captured specimens of two notothenioid fish species affected by large skin tumors at an incid...

Pseudoloma neurophilia is a critical threat to the zebrafish (Danio rerio) model, as it is the most common infectious agent found in research facilities. In this study, our objectives were two‐fold: (1) compare the application of diagnostic tools for P. neurophilia and (2) track the progression of infection using PCR and histology. The first experi...

There have been several significant new findings regarding Microsporidia of fishes over the last decade. Here we provide an update on new taxa, new hosts and new diseases in captive and wild fishes since 2013. The importance of microsporidiosis continues to increase with the rapid growth of finfish aquaculture and the dramatic increase in the use o...

A novel Enterocytozoon infection was identified in the intestines of sexually mature Chinook salmon. While microsporidian parasites are common across a diverse range of animal hosts, this novel species is remarkable because it demonstrates biological, pathological, and genetic similarity with Enterocytozoon bieneusi, the most common causative agent...

Specific pathogen-free (SPF) animals are bred and managed to exclude pathogens associated with significant morbidity or mortality that may secondarily pose a risk to public health, food safety and food security, and research replicability. Generating and maintaining SPF animals requires detailed biosecurity planning for control of housing, environm...

Background: Pain trajectories have been described in numerous surgical settings where preoperative characteristics have been used to predict trajectory membership. Suboptimal pain intensity trajectories have been linked to poor longitudinal outcomes. However, numerous biopsychosocial modulators of postoperative pain may also have distinct longitud...

Crassiphialinae Sudarikov, 1960 is a large subfamily of the Diplostomidae Poirier, 1886 with a complex taxonomic history. It includes a diversity of species parasitic in the intestines of avian and mammalian definitive hosts worldwide. Posthodiplostomum Dubois, 1936 is a large and broadly distributed crassiphialine genus notorious for its associati...

Responses of marine populations to climate conditions reflect the integration of a suite of complex and interrelated physiological and behavioral responses at the individual level. Many of these responses are not immediately reflected in changes to survival, but may impact growth or survival at later life stages. Understanding the broad range of im...

Intestinal neoplasms and preneoplastic lesions are common in zebrafish research facilities. Previous studies have demonstrated that these neoplasms are caused by a transmissible agent, and two candidate agents have been implicated: a Mycoplasma sp. related to Mycoplasma penetrans and the intestinal parasitic nematode, Pseudocapillaria tomentosa, an...

Pacific salmon (Oncorhynchus spp.) rearing in lakes and reservoirs above dams have been known to become heavily infected with an ectoparasitic copepod (Salmincola californiensis). Little is known about the factors that affect the parasite infection prevalence and intensity. However, previous research suggests that the parasite may negatively affect...

Intestinal neoplasms and preneoplastic lesions are common in zebrafish research facilities. Previous studies have demonstrated that the neoplasms are caused by a transmissible agent, and two candidate agents have been implicated: a Mycoplasma sp. related to M. penetrans and the intestinal parasitic nematode, Pseudocapillaria tomentosa , and both ag...

Introduction Ketamine is a vital component for acute pain management in emergency trauma care for both civilian and military hospitals. This preliminary analysis examined whether combat-injured US service members sustaining traumatic brain injuries (TBI) experienced increased odds of ketamine side effects compared with those without TBI. Methods T...

Although zebrafish continue to increase in popularity as a vertebrate animal model for biomedical research, chronic infectious diseases in laboratory populations remain prevalent. The presence of pathogens such as Pseudocapillaria tomentosa, a parasitic nematode found in the intestine of infected zebrafish, can significantly influence experimental...

Objective To investigate pain catastrophizing presentations up to 6-months postoperatively and subsequent changes in pain intensity and physical function. Design Prospective observational multisite study Setting Two tertiary care facilities between 2016 and 2019 Participants Adult patients undergoing a mastectomy, thoracic surgery, total knee or...

The use of zebrafish (Danio rerio) in biomedical research has expanded at a tremendous rate over the last two decades. Along with increases in laboratories using this model, we are discovering new and important diseases. We review here the important pathogens and diseases based on some 20 years of research and findings from our diagnostic service a...

We used odds ratios and a hurdle model to analyze parasite co-infections over 25 years on >20,000 young-of-the year of endangered Shortnose and Lost River Suckers. Host ecologies differed as did parasite infections. Shortnose Suckers were more likely to be caught inshore and 3 – 5 times more likely to have Bolbophorus spp. and Contracaecum sp. infe...

The zebrafish is a widely used animal model in biomedical research. Despite this, pathogens continue to be common in laboratory zebrafish. It is important to determine and describe the pathophysiology of cryptic infections on zebrafish to elucidate the impacts on experimental endpoints. Body condition is a basic measurement used experimentally and...

Background/Objective The role of caregiver psychosocial characteristics and their relation to postsurgical caregiving capability remains unclear. The objective of this study was to explore caregiver psychosocial variables following surgery of patients undergoing total joint arthroplasty and spine surgery. Methods A prospective observational study...

Pseudocapillaria tomentosa is a pathogenic nematode parasite, causing emaciation and severe inflammatory lesions in the intestines in zebrafish Danio rerio (Hamilton 1822). Emamectin benzoate is commercially available analogue of ivermectin used for treating salmon for sea lice, under the brand name SLICE®, and we have used this for treating zebraf...

Pseudocapillaria tomentosa is an important pathogen in zebrafish facilities. We investigated heat, ultraviolet (UV) light, chlorine, iodine, and dessciation for killing the parasite's eggs. Eggs released with feces larvate in about 5-10 days, and treatments were evaluated by exposing fresh eggs and subsequently comparing larvation to untreated eggs...

Surgical care episodes place opioid-naive patients at risk for transitioning to new persistent postoperative opioid use. With one of the central principles being the application of multimodal pain interventions to reduce the reliance on opioid-based medications, enhanced recovery pathways provide a framework that decreases perioperative opioid use....

Persistent postoperative opioid use is thought to contribute to the ongoing opioid epidemic in the United States. However, efforts to study and address the issue have been stymied by the lack of a standard definition, which has also hampered efforts to measure the incidence of and risk factors for persistent postoperative opioid use. The objective...

Background Helminth parasites represent a significant threat to the health of human and animal populations, and there is a growing need for tools to treat, diagnose, and prevent these infections. Recent work has turned to the gut microbiome as a utilitarian agent in this regard; components of the microbiome may interact with parasites to influence...

Parasites in wild populations almost always exhibit aggregation (overdispersion), in which relatively few hosts are infected with high numbers of the parasites. This pattern of infection has also been observed in laboratory studies, where many of the sources of natural variation are removed. Pseudocapillaria tomentosa (Nematoda) is common in zebraf...

Trap and haul programmes are used to conserve fish populations by circumventing high mortality locations or events and enhancing population abundance by reintroducing fish to historical habitats and mitigating for fish passage limitations. Spring‐run Chinook salmon are transported in trucks upstream of barrier dams in Willamette River Tributaries a...

A laboratory zebrafish colony developed red masses, predominantly under the jaw, in a significant portion of the population. The masses were diagnosed histopathologically as thyroid follicular hyperplasia, adenoma, or carcinoma in accordance with published morphologic criteria. After switching to a higher iodine brand of salt used to maintain a low...

Shortnose Sucker (Chasimistes brevirostris) and Lost River Sucker (Deltistes luxatus) are endemic to the Upper Klamath Basin of Southern Oregon and Northern California, and their populations are in decline. We used histopathology and external examination of 140 and external examination only of 310 underyearling suckers collected in 2013, 2015 and 2...

Cryopreservation is a common method used to preserve the sperm of various animal species, and it is widely used with zebrafish (Danio rerio). As with other animals, there is a possibility of paternal pathogen transmission through sperm. We evaluated the ability of five common and important pathogens of zebrafish to survive cryopreservation as used...

In recent conflicts, advances in acute pain management have been pushed to the forefront of battlefield medical care. With dramatic improvements in battlefield resuscitation, mortality rates have significantly decreased, as a result significant numbers of patients sustaining severe polytraumatic injuries must now be transported from the site of inj...

Here, we report the draft genome sequence of Pseudomonas sp. strain DrBHI1. The total assembly length is 5,649,751 bp in 146 contigs. This strain was isolated from zebrafish ( Danio rerio ) feces.

Objective: With the increasing societal awareness of the prevalence and impact of acute pain, there is a need to develop an acute pain classification system that both reflects contemporary mechanistic insights and helps guide future research and treatment. Existing classifications of acute pain conditions are limiting, with a predominant focus on...

Objective: With the increasing societal awareness of the prevalence and impact of acute pain, there is a need to develop an acute pain classification system that both reflects contemporary mechanistic insights and helps guide future research and treatment. Existing classifications of acute pain conditions are limiting, with a predominant focus on...

After returning to spawning areas, adult Pacific salmon Oncorhynchus spp. often die without spawning successfully, which is commonly referred to as prespawn mortality. Prespawn mortality reduces reproductive success and can thereby hamper conservation, restoration, and reintroduction efforts. The primary source of information used to estimate presp...

1. Introduction2. Indicators of Stress in Laboratory Fish3. Factors Impacting Stress in Laboratory Fish Handling4. Housing 4.1. Density4.2. Enrichment4.3. Light/Dark Cycle5. Feeding and Stress6. Sex and Hierarchies7. Sex Determination and Reversal8. Stress, Cortisol, and Reproduction9. Anesthetics10. Underlying Diseases11. Consistency12. Conclusion...

The trematode Nanophyetus salmincola is known as the carrier of Neorickettsia helminthoeca, an obligate intracellular endosymbiotic bacterium that causes salmon poisoning disease (SPD), a fatal disease of dogs. The bacteria are maintained through the complex life cycle of N. salmincola that involves snails Juga plicifera as the first intermediate h...

Helminth parasites represent a significant threat to wild, domesticated, and research animal health. Pseudocapillaria tomentosa is a common intestinal nematode parasite and an important source of infection in zebrafish. Symptoms of the infection vary widely from no clinical signs to sever emaciation and mortality, however, the reasons underpinning...

In 2011, the zebrafish research facility at the University of Oregon experienced an outbreak of Mycobacterium marinum that affected both research fish and facility staff. A thorough review of risks to personnel, the zebrafish veterinary care program, and zebrafish husbandry procedures at the research facility followed. In the years since 2011, chan...

The microsporidium, Pseudoloma neurophilia, is the most common infectious organism found in laboratory zebrafish colonies. Many currently used zebrafish lines originally came from pet store fish, and the initial description of P. neurophilia came from zebrafish obtained from a retail pet store. However, as P. neurophilia has not been described from...

In 2011, the zebrafish research facility at the University of Oregon experienced an outbreak of Mycobacterium marinum that affected both research fish and facility staff. A thorough review of risks to personnel, the zebrafish veterinary care program, and zebrafish husbandry procedures at the research facility followed. In the years since 2011, chan...

Gamma irradiation is commonly used as a bone marrow suppressant in studies of the immune system and hematopoiesis, most commonly in mammals. With the rising utility and popularity of the zebrafish (Danio rerio), gamma irradiation is being used for similar studies in this species. Pseudoloma neurophilia, a microparasite and common contaminant of zeb...

Grass carp Ctenopharyngodon idella are sometimes used as a biological tool for managing aquatic vegetation in reservoirs. Sterile, triploid fish were stocked in Devils Lake, Oregon, during 1986, 1987, and 1993 to control aquatic vegetation. We present a case study for using multiple measures on the same fish to determine whether illegal stocking of...

Mycobacteriosis is the second most common infectious disease in zebrafish research colonies, and most often this is caused by Mycobacterium chelonae. The infection is characterized by multiple granulomas in the kidney, coelomic cavity, particularly the ovary. However, most fish still appear clinically normal. Developmental genetics remain a primary...

The Zebrafish International Resource Center (ZIRC) is a repository and distribution center for mutant, transgenic, and wild-type zebrafish. In recent years annual imports of new zebrafish lines to ZIRC have increased tremendously. In addition, after 15 years of research, we have identified some of the most virulent pathogens affecting zebrafish tha...

Spring Chinook Salmon Oncorhynchus tshawytscha are transported above dams in the Willamette River to provide access to blocked spawning habitat. However, 30–95% of these transplants may die before spawning in some years. To varying degrees, salmon in other tributaries—both blocked and unblocked—have similar prespawn mortality (PSM) rates. Our study...