Pathology, microbiology, and genetic diversity associated with Erysipelothrix rhusiopathiae and novel Erysipelothrix spp. infections in southern sea otters (Enhydra lutris nereis)

Erysipelothrix spp., including E. rhusiopathiae, are zoonotic bacterial pathogens that can cause morbidity and mortality in mammals, fish, reptiles, birds, and humans. The southern sea otter (SSO; Enhydra lutris nereis) is a federally-listed threatened species for which infectious disease is a major cause of mortality. We estimated the frequency of detection of these opportunistic pathogens in dead SSOs, described pathology associated with Erysipelothrix infections in SSOs, characterized the genetic diversity and antimicrobial susceptibility of SSO isolates, and evaluated the virulence of two novel Erysipelothrix isolates from SSOs using an in vivo fish model. From 1998 to 2021 Erysipelothrix spp. were isolated from six of >500 necropsied SSOs. Erysipelothrix spp. were isolated in pure culture from three cases, while the other three were mixed cultures. Bacterial septicemia was a primary or contributing cause of death in five of the six cases. Other pathology observed included suppurative lymphadenopathy, fibrinosuppurative arteritis with thrombosis and infarction, bilateral uveitis and endophthalmitis, hypopyon, petechia and ecchymoses, mucosal infarction, and suppurative meningoencephalitis and ventriculitis. Short to long slender Gram-positive or Gram-variable bacterial rods were identified within lesions, alone or with other opportunistic bacteria. All six SSO isolates had the spaA genotype–four isolates clustered with spaA E. rhusiopathiae strains from various terrestrial and marine animal hosts. Two isolates did not cluster with any known Erysipelothrix spp.; whole genome sequencing revealed a novel Erysipelothrix species and a novel E. rhusiopathiae subspecies. We propose the names Erysipelothrix enhydrae sp. nov. and Erysipelothrix rhusiopathiae ohloneorum ssp. nov. respectively. The type strains are E. enhydrae UCD-4322-04 and E. rhusiopathiae ohloneorum UCD-4724-06, respectively. Experimental injection of tiger barbs (Puntigrus tetrazona) resulted in infection and mortality from the two novel Erysipelothrix spp. Antimicrobial susceptibility testing of Erysipelothrix isolates from SSOs shows similar susceptibility profiles to isolates from other terrestrial and aquatic animals. This is the first description of the pathology, microbial characteristics, and genetic diversity of Erysipelothrix isolates recovered from diseased SSOs. Methods presented here can facilitate case recognition, aid characterization of Erysipelothrix isolates, and illustrate assessment of virulence using fish models

Investigating the prevalence and pathogenesis of Helicobacter infections in southern sea otters (Enhydra lutris nereis)

While it is known that Helicobacter species in humans and ferrets can cause gastritis and gastric ulcers, it is unknown if the sea otter bacterium, ‘H. enhydrae’ sp. nov., causes similar gastric diseases. Southern sea otters (Enhydra lutris nereis) are marine mustelids that commonly have gastric ulcers as a significant contributing cause of death. Determining whether Helicobacter infection promotes gastric diseases might aid population recovery by recognizing disease presentation and facilitating treatments. As a first step, we investigated the prevalence of Helicobacter infections in southern sea otters using DNA. Helicobacter DNA was amplified using quantitative polymerase chain reaction from formalin-fixed and fresh-frozen gastric body and pyloric tissues from 46 sea otters using Helicobacter genus 16S rRNA primers. Postmortem examination data and histology were statistically analyzed to uncover associations between Helicobacter presence and gastric diseases. Enrolled sea otters had an 85% Helicobacter spp. prevalence, which is comparable to H. mustelae in ferrets. Fresh frozen tissues showed a higher amount of Helicobacter qPCR-positive samples than did formalin-fixed tissues. Gastric ulcers at the postmortem exam were significantly associated with Helicobacter positivity, while other analyzed factors such as sex, melena, and shark trauma were not correlated. Antibiotic sensitivity analysis show that ‘H. enhydrae’ was sensitive to tetracycline and clarithromycin in vitro. Our data suggest that Helicobacter infections are prevalent in southern sea otters and are associated with gastric ulcers. Our data represents a first step in the study of this potential pathogen, supporting that further work is warranted to assess whether ‘H. enhydrae’ causes or is simply associated with gastric ulcers

Helicobacter spp. in Necropsied Southern Sea Otters (Enhydra lutris nereis) Is Associated With Gastric Ulcers and Sensitive to Multiple Antibiotics

© Copyright © 2020 Batac, Miller, Moriarty, Shen, Fox and Ottemann. Southern sea otters (Enhydra lutris nereis) are threatened marine mustelids that commonly have gastric ulcers with secondary hemorrhage (melena) as a contributing cause of death. Although Helicobacter spp. infections are known to cause gastric ulcers and gastritis in humans and ferrets, it is unknown if the sea otter bacterium, H. enhydrae sp. nov., causes similar gastric pathology. Determining whether Helicobacter detection is associated with sea otter gastric pathology is the first step toward using this information to expedite diagnosis and treatment. We investigated the proportion of Helicobacter infections in 46 necropsied southern sea otters via quantitative real-time polymerase chain reaction (qPCR) of the 16S rRNA gene. Helicobacter DNA was detected in fresh-frozen and formalin-fixed gastric body and pyloric tissues using Helicobacter genus-specific 16S rRNA primers. Data from gross necropsy and histopathology were analyzed for associations between Helicobacter detection via qPCR and presence/absence of gastric pathology. ETEST® gradient strips were utilized to investigate antimicrobial minimum inhibitory concentrations for H. enhydrae isolates. Helicobacter spp. were detected in the gastric tissue of 85% of sea otters in this study. Fresh-frozen samples were more commonly Helicobacter qPCR-positive than formalin-fixed tissue, indicating variable sensitivity of detection in relation to post-necropsy tissue processing methods. Diagnosis of gastric ulcers at necropsy was significantly associated with Helicobacter qPCR detection in gastric mucosa (P = 0.005), while age, sex, presence of melena, shark trauma, and protozoal infection were not associated (P > 0.1). Helicobacter enhydrae isolates were sensitive to clarithromycin and tetracycline in vitro at physiologically relevant concentrations. Overall, this work suggests that Helicobacter spp. might be commonly found in southern sea otters, particularly those with ulcers, and that H. enhydrae can be treated with several commonly used anti-Helicobacter therapies

Pathology and epidemiology of nasopulmonary acariasis (Halarachne sp.) in southern sea otters (Enhydra lutris nereis).

Halarachne sp. nasal mites infest harbor seals (Phoca vitulina) and southern sea otters (Enhydra lutris nereis) in California, but little is known about the pathophysiology of these infestations, or risk factors for exposure. To investigate these questions, a retrospective case-control study was performed using necropsy data from 70 mite-infested sea otters, and 144 non-infested controls. Case records for sea otters examined by pathologists from February 1999 through May 2015 were examined to assess risk factors for infestation, and lesions associated with nasopulmonary acariasis. Animals with a history of captive care within 10 days of death or carcass recovery were 3.2 times more likely to be infested with nasopulmonary mites than those with no history of recent rehabilitation. Sea otters stranding within 1 km of Elkhorn Slough in Monterey Bay were 4.9 times more likely to be infested with nasal mites than other areas; this site is characterized by high sea otter contact with sympatric harbor seals (a common host for Halarachne sp.), and a comparatively large population of rehabilitated and released sea otters. Aged adult otters were 9.4 times more likely to be infested than younger animals, and sea otters with nasopulmonary acariasis were 14.2 times more likely to have upper respiratory inflammation than un-infested animals. Additional findings in otters with nasopulmonary acariasis included lower respiratory tract bacterial infections, presence of medium-sized and/or fresh nose wounds at necropsy (indicators of recent face-to-face interaction between otters during copulation or fighting), and turbinate bone erosion. Our findings, although preliminary, suggest that captive rehabilitation and close contact with harbor seals could facilitate nasopulmonary mite transmission to sea otters. We also identified a high-risk zone for nasopulmonary acariasis in sea otters. We also provide preliminary data to suggest that nasopulmonary mite infestations can cause significant respiratory pathology in sea otters

Pathology, microbiology, and genetic diversity associated with Erysipelothrix rhusiopathiae and novel Erysipelothrix spp. infections in southern sea otters (Enhydra lutris nereis).

Erysipelothrix spp., including E. rhusiopathiae, are zoonotic bacterial pathogens that can cause morbidity and mortality in mammals, fish, reptiles, birds, and humans. The southern sea otter (SSO; Enhydra lutris nereis) is a federally-listed threatened species for which infectious disease is a major cause of mortality. We estimated the frequency of detection of these opportunistic pathogens in dead SSOs, described pathology associated with Erysipelothrix infections in SSOs, characterized the genetic diversity and antimicrobial susceptibility of SSO isolates, and evaluated the virulence of two novel Erysipelothrix isolates from SSOs using an in vivo fish model. From 1998 to 2021 Erysipelothrix spp. were isolated from six of >500 necropsied SSOs. Erysipelothrix spp. were isolated in pure culture from three cases, while the other three were mixed cultures. Bacterial septicemia was a primary or contributing cause of death in five of the six cases. Other pathology observed included suppurative lymphadenopathy, fibrinosuppurative arteritis with thrombosis and infarction, bilateral uveitis and endophthalmitis, hypopyon, petechia and ecchymoses, mucosal infarction, and suppurative meningoencephalitis and ventriculitis. Short to long slender Gram-positive or Gram-variable bacterial rods were identified within lesions, alone or with other opportunistic bacteria. All six SSO isolates had the spaA genotype-four isolates clustered with spaA E. rhusiopathiae strains from various terrestrial and marine animal hosts. Two isolates did not cluster with any known Erysipelothrix spp.; whole genome sequencing revealed a novel Erysipelothrix species and a novel E. rhusiopathiae subspecies. We propose the names Erysipelothrix enhydrae sp. nov. and Erysipelothrix rhusiopathiae ohloneorum ssp. nov. respectively. The type strains are E. enhydrae UCD-4322-04 and E. rhusiopathiae ohloneorum UCD-4724-06, respectively. Experimental injection of tiger barbs (Puntigrus tetrazona) resulted in infection and mortality from the two novel Erysipelothrix spp. Antimicrobial susceptibility testing of Erysipelothrix isolates from SSOs shows similar susceptibility profiles to isolates from other terrestrial and aquatic animals. This is the first description of the pathology, microbial characteristics, and genetic diversity of Erysipelothrix isolates recovered from diseased SSOs. Methods presented here can facilitate case recognition, aid characterization of Erysipelothrix isolates, and illustrate assessment of virulence using fish models