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

Abstract

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.

Predators, Disease, and Environmental Change in the Nearshore Ecosystem: Mortality in Southern Sea Otters (Enhydra lutris nereis) From 1998–2012

“…Nasopulmonary acariasis (Halarachne halocheri infestation; Pesapane et al, 2018;Shockling-Dent et al, 2019) was a contributing COD for three otters. Larva migrans (brain infection by Baylisascaris sp.…”

“…Nearly two decades have passed since the last comprehensive analysis of southern sea otter mortality patterns (Kreuder et al, 2003), and much has been learned about the effects of marine predators (Tinker et al, 2016), viruses (Tuomi et al, 2014;Ng et al, 2015;Siqueira et al, 2017), bacteria (Johnson et al, 2003;Stavely et al, 2003;Miller et al, 2010aMiller et al, , 2018Bartlett et al, 2016), parasites (Miller et al, 2004(Miller et al, , 2008(Miller et al, , 2010b(Miller et al, , 2018Shapiro et al, 2012Shapiro et al, , 2016Shapiro et al, , 2019Shockling-Dent et al, 2019), fungi (Huckabone et al, 2015), and biotoxins (Miller et al, 2010c;Fire and Van Dolah, 2012) on sea otters. Novel health conditions have been identified, and some idiopathic conditions have become better-characterized (Kreuder et al, 2005;Tuomi et al, 2014;Ng et al, 2015;Chinn et al, 2016;Shockling-Dent et al, 2019;Miller et al, in review). Due to new discoveries and improved diagnostic tests, and because mortality patterns are not static in wild populations, periodic reassessment is vital.…”

Nasopulmonary mites (Halarachnidae) of coastal Californian pinnipeds: Identity, prevalence, and molecular characterization

“…We investigated the identity and prevalence of nasopulmonary mites infesting Pacific harbor seals, California sea lions, northern elephant seals, northern fur seals, and Guadalupe fur seals to complement published findings from sympatric southern sea otters from the coast of California, USA ( Pesapane et al, 2018 ; Shockling Dent et al, 2019 ). Although phocids such as harbor seals , grey seals (Halichoerus grypus ), hooded seals ( Cystophora cristata ), spotted seals ( Phoca largha ) , and southern elephant seals ( Mirounga leonina ) are reported hosts for H. halichoeri ( Margolis and Dailey, 1972 ; Furman and Dailey, 1980 ; Fay and Furman, 1982 ; Baker, 1987 ; Alonso-Farré et al, 2012 ), we present the first evidence of this mite species infesting a northern elephant seal.…”

“…However, each halarachnid mite species' affinity for particular hosts and the extent of mite transmission between host species is poorly understood. For example, significant risk factors for southern sea otters infested with H. halichoeri include proximity to Pacific harbor seals along with a prior history of captive care and stranding near Moss Landing within Monterey Bay California ( Pesapane et al, 2018 ; Shockling Dent et al, 2019 ). Although harbor seals were proposed as a source of nasopulmonary mite infestation for southern sea otters, temporally-matched data regarding mite burdens in sympatric harbor seals was not available for comparison.…”

“…Parasites are noted whenever observed during necropsy, providing opportunities to study halarachnid mites across multiple host species. We investigated the identity and prevalence of nasopulmonary mites from Pacific harbor seals, California sea lions, northern elephant seals, northern fur seals, and Guadalupe fur seals necropsied by TMMC to complement published nasopulmonary mite findings from southern sea otters that stranded during the same approximate timeframe ( Pesapane et al, 2018 ; Shockling Dent et al, 2019 ). We also present comparative scanning electron micrographs (SEM) and DNA sequence data for Halarachne miroungae, H. halichoeri, and O. attenuata from different marine mammal hosts.…”