Biology subjects

Duignan, P. J.

Publications and source records attributed to Duignan, P. J..

6 recordsLinked to original sources

bioRxiv2026

Leptospirosis in Southern Sea Otters from Central California: Detection of Fatal Infections and Pathologic Findings

Leptospira interrogans serovar Pomona infections cause periodic outbreaks among California sea lions (CSL; Zalophus californianus) and sporadic deaths in phocids; however, frequency of infection and associated health impacts are uncharacterized among sympatric threatened southern sea otters (SSO; Enhydra lutris nereis), which are important sentinels of coastal health. Given the broad impacts of L. interrogans on other marine mammals, our objective was to screen selected SSO for infection, determine whether leptospirosis contributes to SSO mortality, and describe leptospiral-associated lesions. A retrospective review (2005-2025) yielded 19 candidates that underwent case review, including Leptospira immunohistochemistry (IHC), serology, and polymerase chain reaction (PCR), with a special focus on renal and hepatic lesions. Kidney was PCR-positive for 74% (14/19) of suspected cases and for eight of these, DNA sequence-based serogroup typing detected L. interrogans serogroup Pomona. Seven of the 14 PCR-positive leptospirosis cases were classed as fatal based on positive renal IHC and moderate to severe tubulointerstitial nephritis. All fatal cases had anti-L. interrogans serovar Pomona antibody titers [≥]1:25,600. All remaining (n=7) PCR-positive cases were considered nonfatal leptospirosis cases due to minimal and/or unrelated renal lesions, and negative IHC. Nonfatal Leptospira-infected cases ranged from seronegative to low positive (1:400) for serovar Pomona. Antibody titers for Leptospira PCR-negative cases were negative. For fatal cases, gross renal changes were often inapparent or characterized by miliary white cortical foci. Renal histologic lesions included tubulointerstitial nephritis, acute tubular necrosis and suppurative tubulitis with intratubular bacteria in fatal cases, and positive IHC staining for leptospiral antigen in lesions. Gross hepatic changes were also inapparent in fatal cases and histologic lesions were rare, characterized in one animal by hepatocellular disassociation and in two sea otters by limited leptospiral antigen detection by IHC. Most Leptospira-infected sea otters (71%, 10/14) stranded during higher rainfall months in California, suggesting possible land-to-sea transmission from terrestrial hosts. Given these findings, and because L. interrogans serovar Pomona infections have been confirmed in sympatric CSLs and terrestrial mammals from adjacent watersheds, focused investigation of potential marine and terrestrial disease transmission dynamics could provide new information to reduce mortalities of SSO.

pathology↗

bioRxiv2024

Identification of Candidate Protein Biomarkers Associated with Domoic Acid Toxicosis in Cerebrospinal Fluid of California Sea Lions (Zalophus californianus)

Since 1998, California sea lion (Zalophus californianus) stranding events associated with domoic acid toxicosis have consistently increased. Outside of direct measurement of DA in bodily fluids at the time of stranding, currently there are no practical non-lethal clinical tests for the diagnosis of domoic acid toxicosis (DAT) that can be utilized in a large-scale rehabilitation facility. Proteomic analysis was conducted to discover candidate protein markers of DAT using cerebrospinal fluid from stranded California sea lions with acute DAT (n = 8), chronic DAT (n = 19), or without DAT (n = 13). A total of 2005 protein families were identified experiment-wide (FDR < 0.01). Of these proteins, 83 were significantly different in abundance across the three groups (adj. p < 0.05). Cytoplasmic malate dehydrogenase (MDH1), 5-3 exonuclease PLD3, disintegrin and metalloproteinase domain-containing protein 22 (ADAM22), 14-3-3 protein gamma (YWHAG), neurosecretory protein VGF, and calsyntenin-1 (CLSTN1) were able to discriminate California sea lions with or without DAT (ROC > 0.75). Immunoglobulin kappa light chain-like (IGKV2D-28), receptor-type tyrosine-phosphatase F (PTRPF), kininogen-1 (KNG1), prothrombin (F2), and beta-synuclein (SNCB) were able to discriminate acute DAT from chronic DAT (ROC > 0.75). Interestingly, proteins involved in alpha synuclein deposition were over- represented as classifiers of DAT and many of these proteins have been implicated in a variety of neurodegenerative diseases. These proteins should be considered potential markers for DAT in California sea lions, as well as markers to discriminate between acute or chronic DAT, and should be considered priority for future validation studies as biomarkers. All MS data have been deposited in the ProteomeXchange with identifier PXD041356 (http://proteomecentral.proteomexchange.org/dataset/PXD041356).

biochemistry↗

bioRxiv2023

The Symptomatology and Diagnosis of Domoic Acid Toxicosis in Stranded California Sea Lions (Zalophus californianus): A Review and Evaluation of 20 Years of Cases to Guide Prognosis

Domoic acid (DA) is a glutaminergic excitatory neurotoxin that causes morbidity and mortality of California sea lions (Zalophus californianus; CSL) and other marine mammals due to a suite of effects mostly on the nervous and cardiac systems. Between 1998 and 2019, 11,737 live-stranded CSL were admitted to The Marine Mammal Center (TMMC; Sausalito, CA, USA), over 2,000 of which were intoxicated by DA. A plethora of clinical research has been performed over the past 20 years to characterize the range of toxic effects of DA exposure on CSLs, generating the largest dataset on the effects of natural exposure to this toxin in wildlife. Here we review published methods for diagnosing DA intoxication, clinical presentation and treatment of DA-intoxicated CSL, and present a practical, reproducible scoring system called the neuroscore (NS) to help assess whether a DA-affected CSL is fit for release to the wild following rehabilitation. The largest proportion of DA-intoxicated CSL were adult females (58.6%). The proportions of acute and chronic cases were 63.5% and 36.5%, respectively, with 44% of affected CSL released and 56% either dying naturally or euthanized. The average time in rehabilitation was 15.9 days (range 0-169) for all outcomes. Logistic regression models were used to assess the relationships between outcome (released vs. euthanized or died) and multiple variables to predict the outcome for a subset of 92 stranded CSLs. The best performing model (85% prediction accuracy; area under the curve = 0.90) consisted of four variables: final NS, change in NS over time, whether the animal began eating in rehabilitation, and the state of nutrition on admission. These results suggest that a behavioral scoring system is a useful tool to assess the fitness for release of stranded DA-intoxicated CSL.

zoology↗

bioRxiv2022

Human influenza A virus H1N1 1 in marine mammals in California, 2019

From 2011-2018, we conducted surveillance in marine mammals along the California coast for influenza A virus (IAV), frequently detecting anti-influenza antibodies and intermittently detecting IAV. In spring 2019, this pattern changed. Despite no change in surveillance intensity, we detected IAV RNA in 10 samples in March and April, mostly in nasal and rectal swabs from northern elephant seals (Mirounga angustirostris). Although virus isolation was unsuccessful, IAV sequenced from one northern elephant seal nasal swab showed close genetic identity with pandemic H1N1 IAV subclade 6B.1A.1 that was concurrently circulating in humans in the 2018/19 influenza season. This represents the first report of human A(H1N1)pdm09 IAV in northern elephant seals since 2010, suggesting IAV continues to spill over from humans to pinnipeds.

microbiology↗

bioRxiv2020

Respiratory tract explant infection dynamics of influenza A virus in California sea lions, northern elephant seals, and rhesus macaques and severe acute respiratory syndrome virus-2 in rhesus macaques

To understand susceptibility of wild California sea lions and Northern elephant seals to influenza A virus (IAV), we developed an ex vivo respiratory explant model and used it to compare infection kinetics for multiple IAV subtypes. We first established the approach using explants from colonized rhesus macaques, a model for human IAV. Trachea, bronchi, and lungs from 11 California sea lions, 2 Northern elephant seals and 10 rhesus macaques were inoculated within 24 hours post-mortem with 6 strains representing 4 IAV subtypes. Explants from the 3 species showed similar IAV infection kinetics with peak viral titers 48-72 hours post-inoculation that increased by 2-4 log10 plaque forming units (PFU)/explant relative to the inoculum. Immunohistochemistry localized IAV infection to apical epithelial cells. These results demonstrate that respiratory tissue explants from wild marine mammals support IAV infection. In the absence of the ability to perform experimental infections of marine mammals, this ex vivo culture of respiratory tissues mirrors the in vivo environment and serves as a tool to study IAV susceptibility, host-range, and tissue tropism. ImportanceAlthough influenza A virus can infect marine mammals, a dearth of marine mammal cell lines and ethical and logistical challenges prohibiting experimental infections of living marine mammals means that little is known about IAV infection kinetics in these species. We circumvented these limitations by adapting a respiratory tract explant model first to establish the approach with rhesus macaques and then for use with explants from wild marine mammals euthanized for non-respiratory medical conditions. We observed that multiple strains representing 4 IAV subtypes infected trachea, bronchi, and lungs of macaques and marine mammals with variable peak titers and kinetics. This ex vivo model can define infection dynamics for IAV in marine mammals. Further, use of explants from animals euthanized for other reasons reduces use of animals in research.

microbiology↗

bioRxiv2017

Sex differences in the epidemiology of tattoo skin disease in captive common bottlenose dolphins (Tursiops truncatus): are males more vulnerable than females?

The clinical and epidemiological features of tattoo skin disease (TSD), caused by cetacean poxviruses, are reported in 257 common bottlenose dolphins (Tursiops truncatus) held in 31 facilities in the USA and Europe. Photographs and biological data of 146 females and 111 males were analyzed. Dolphins were classified into three age classes (0-3; 4-8; over 9 years), approximating the life stages of calves and young juveniles, juveniles and sub-adults and adults. The youngest dolphins with tattoos were 14 and 15 months old. Minimal TSD persistence varied between 4 and 65 months in 30 dolphins and was over 22 months in those with very large lesions (> 115 mm). In 2012-2014, 20.6% of the 257 dolphins had TSD. Prevalence varied between facilities from 5.6% (n= 18) to 60% (n= 20), possibly reflecting variation in environmental conditions. Prevalence was significantly higher in males (31.5%) than in females (12.3%), a pattern which departs from that observed in free-ranging Delphinidae where there is no gender bias. As with free-ranging Delphinidae, TSD prevalence in captive females varied with age category, being the highest in the 4 to 8 year old. By contrast, prevalence levels in males were high in all age classes. Prevalence of very large tattoos was also higher in males (28.6%, n= 35) than in females (11.1%, n= 18). Combined, these data suggest that captive male T. truncatus are more vulnerable to TSD than females possibly because of differences in immune response and because males may be more susceptible to captivity-related stress than females.

epidemiology↗