Browsing by Author "Tolo, Isaiah"

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    Carp Edema Virus Host Range Study in Lake Swartout and Outbreaks in four other lakes
    (2021-03-02) Tolo, Isaiah; Phelps, Nicholas; tolo0007@umn.edu; Phelps, Nicholas; Minnesota Aquatic Invasive Species Research Center
    Mass mortality events of common carp (Cyprinus carpio, carp) associated with carp edema virus (CEV) alone or in coinfections with koi herpesvirus (KHV), is an emerging issue. Despite recent outbreaks of CEV in wild carp populations, the host range of North American species has not been well studied. To that end, we intensively sampled carp (n = 106) and co-habiting native fish species (n = 5 species; n = 156 total fish) from a CEV-suspect mass-mortality event of carp in a small Minnesota lake (Lake Swartout). Additionally, fecal and regurgitant samples (n = 73 each) from double-crested cormorants (Phalacrocorax auritus, DCCO) were sampled to test the potential of DCCO to act as a vector for virus transmission. CEV was confirmed to be widespread in the Lake Swartout carp population during the outbreak with high viral loads and histological confirmation, suggesting that CEV was the cause of the mortality event. There were no detections of CEV in any native fish species; however, DCCO regurgitant and fecal samples were positive for CEV DNA. In addition, three CEV-positive and one CEV+KHV-positive mortality events were confirmed with no observed mortality or morbidity of non-carp species in other lakes. This study provides evidence that CEV infection and disease may be specific to carp during mortality events with mixed-species populations, identifies DCCO as a potential vector for CEV, and further expands the known range of CEV, as well as coinfections with KHV, in North America.
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    Disease ecology and host range of Cyprinid herpesvirus 3 (CYHV-3) in North American lakes
    (2022-11-10) Tolo, Isaiah; isaiah.tolo@state.mn.us; Tolo, Isaiah; Minnesota Aquatic Invasive Species Research Center
    Cyprinid herpesvirus-3 (CyHV-3) is an important pathogen of common carp (Cyprinus carpio, carp) causing significant economic and ecological impacts worldwide. The recent emergence of CyHV-3 in the Upper Midwest region of the United States has raised questions related to the disease ecology and host specificity of CyHV-3 in wild carp populations. To determine the prevalence of CyHV-3 in wild populations of fishes in Minnesota, we surveyed five lakes in 2019 in which the virus was known to have caused mass mortality events in carp from 2017-2018. A total of 28 species (n = 756 total fish) of native fishes and 730 carp were screened for the presence of CyHV-3 DNA using specific qPCR. None of the native fish tissues tested positive for CyHV-3 though the prevalence of CyHV-3 in carp was 10-50% in the five lakes. A single lake (Lake Elysian) with a 50% DNA detection rate and evidence of ongoing transmission and CyHV-3 associated mortality was surveyed again in 2020 from April-September. During this period, none of the tissues from 24 species (n = 607 total fish) tested positive for CyHV-3 though CyHV-3 DNA and mRNA (indicating viral replication) was detected in carp tissues during the sampling period. CyHV-3 DNA was detected most often in brain samples without evidence of replication, potentially indicating that brain tissue is a site for CyHV-3 persistence. Paired qPCR and ELISA testing for Lake Elysian in 2019-2020 identified young carp (especially males) to be the primary group impacted by CyHV-3 associated mortality and acute infections, but with no positive detections in juvenile carp. Seroprevalence of carp from Lake Elysian was 57% in 2019, 92% in April of 2020 and 97% in by September 2020. These results further corroborate the host specificity of CyHV-3 to carp in mixed wild populations of fishes in Minnesota and provide additional insights into the ecological niche of CyHV-3 in shallow lake populations of carp in North America. Little to no curation was performed on this dataset. DRUM can not verify the completeness or quality of the documentation, nor the FAIRness of the included files. Please contact the author with any questions.
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    Host range and disease dynamics of viral pathogens of common carp (Cyprinus carpio), and their potential as biological control agents
    (2022-11) Tolo, Isaiah
    Common carp (Cyprinus carpio), hereafter referred to as carp, is a ubiquitous and destructive invasive fish in Minnesota and much of the world. There is a need for the development of species-specific, highly effective, and cost-efficient approaches for carp management that can be used across large scales. Pathogen biocontrol agents have previously been used in combination with conventional methods to control vertebrate pests at the landscape scale. Cyprinid herpesvirus 3 (CyHV-3; aka. Koi herpesvirus, KHV) and carp edema virus (CEV) are pathogens worthy of further investigation for carp biocontrol due to their host-specific pathogenicity. Both CyHV-3 and CEV are known to cause mass mortality events of carp and it is possible that carp populations can continue to decline after initial outbreaks. Despite the potential value of viruses as biocontrol agents, there are significant data gaps in the understanding of the distribution and disease ecology of carp-specific viruses in North America, a need for increased research capacity, as well as concern related to the risks of using microbial biological control agents in general. This dissertation is composed of research working to identify a safe and effective pathogenic biocontrol agent for carp. This work contributes to the understanding of the potential value of viral biocontrol of carp by identifying the distribution of CyHV-3 and CEV in Minnesota, obtaining a regional viral strain of CyHV-3 from a carp mortality event, assessing the host range and disease dynamics of these viruses, and by describing the natural ecology of CyHV-3 in laboratory disease trials and wild populations surveys.
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    Investigation of cyprinid herpes virus 3 (CyHV-3) disease periods and factors influencing CyHV-3 transmission in a low stocking density infection trial
    (2021-12-13) Tolo, Isaiah; tolo0007@umn.edu; Tolo, Isaiah; Minnesota Aquatic Invasive Species Research Center
    Pathogens are the primary limitation to aquaculture production of fish and a major issue in consideration of the interface between cultured and wild populations of fishes worldwide. While rapid spread of fish pathogens between populations (wild or farmed) is generally anthropogenic and the result of trade, the mechanisms of transmission once a pathogen has been introduced to a fish population are not well understood. The most widespread pathogen impacting both aquaculture and wild populations of common carp (Cyprinus carpio, carp) is Cyprinid herpesvirus 3 (CyHV-3). To understand how CyHV-3 is transmitted in a population we conducted a series of infection trials, designed to determine the kinetics CyHV-3 infections, identify the contributions of direct and indirect forms of CyHV-3 transmission, and to determine the contributions of contact rate, viral load, pathogenicity, and contact type. We found that direct contact between fish was the primary mechanism of CyHV-3 transmission rather than transmission through contaminated water. Additionally, CyHV-3 transmission occurred primarily during the incubation period of CyHV-3, prior to the appearance of disease signs and disease-associated reduction in contact rate.
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    KHV disease data from wild Cyprinus carpio from Lake Elysian (Le Seuer, MN) and cohabitation disease trial of Cyprinus carpio, Pimephales promelas and Carassius auratus
    (2020-09-28) Tolo, Isaiah; Phelps, Nicholas; phelp083@umn.edu; Phelps, Nicholas; Minnesota Aquatic Invasive Species Research Center
    Koi herpesvirus (KHV) is an important pathogen worldwide and a common cause of mass mortality events of wild common carp (Cyprinus carpio) in North America, however reference strains and genomes obtained from wild carp are not available. Additionally, it is unclear if fishes native to North America are susceptible to KHV infection due to incomplete susceptibility testing. Here we present the first North American type strain and whole genome sequence of KHV isolated from wild carp collected from a lake with history and recent incidence of carp mortality. Additionally, the strain was used in an in-vivo infection model to test the susceptibility of a common native minnow (Pimephales promelas) and goldfish (Carrasius auratus) which is invasive in North America. Detection of KHV DNA was confirmed in the tissues of a single fathead minnow but the same tissues were negative for KHV mRNA and samples from exposed fathead minnows were negative on cell culture. There was no detection of KHV DNA or mRNA in goldfish throughout the experiment. KHV DNA in carp tissues was reproducibly accompanied by detection of KHV mRNA and isolation on cell culture. Additionally, environmental KHV DNA was detected on all tank filters during the study. These findings suggest that fathead minnows and goldfish are not susceptible to KHV infection and that detection of KHV DNA alone in host susceptibility trials should be interpreted with caution