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Postmortem Findings in Four South American Sea Lions (Otaria byronia)
from an Urban Colony in Valdivia, Chile
Author(s): Maximiliano A. Sepúlveda, Mauricio Seguel, Mario Alvarado-Rybak, Claudio
Verdugo, Claudia Muñoz-Zanzi, and Rafael Tamayo
Source: Journal of Wildlife Diseases, 51(1):279-282. 2015.
Published By: Wildlife Disease Association
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DOI: 10.7589/2013-07-161 Journal of Wildlife Diseases, 51(1), 2015, pp. 279–282
Wildlife Disease Association 2015
Postmortem Findings in Four South American Sea Lions
(Otaria byronia) from an Urban Colony in Valdivia, Chile
Maximiliano A. Sepu´lveda,
Claudia Mun˜ oz-Zanzi,
and Rafael Tamayo
Instituto de Medicina Preventiva Veterinaria, Facultad de
Ciencias Veterinarias, Universidad Austral de Chile, Campus Isla Teja s/n, Valdivia, Chile;
Laboratorio de Estudios
´a y Conservacio´n de Mamı
´feros y Aves Acua´ticas, Universidad Austral de Chile, Campus Isla Teja s/n,
Instituto de Patologı
´a Animal, Facultad de Ciencias Veterinarias, Universidad Austral de Chile,
Campus Isla Teja s/n, Valdivia, Chile;
Division of Epidemiology and Community Health, School of Public Health,
University of Minnesota, 1300 S Second St., Suite 300, Minneapolis, Minnesota 55454, USA;
Pathology, College of Veterinary Medicine, University of Georgia, 501 D. W. Brooks Dr #148, Athens, Georgia
Current address: Center of Applied Ecology and Sustainability (CAPES), Pontificia Universidad
Cato´lica de Chile, Alameda 340, Santiago, Chile;
Corresponding author (email: email@example.com)
We performed postmortem exam-
ination on four South American sea lions
(Otaria byronia) from an urban colony in
Valdivia, Chile. Chronic leptospirosis and
suspected morbillivirus-like infection were
diagnosed in one individual. Antibodies against
Toxoplasma gondii and the zoonotic helminthes
Contracaecum sp., Pseudoterranova sp., and
Diphyllobothrium sp. were also detected.
A resident, nonbreeding, small group of
South American sea lions (SASLs; Otaria
byronia) has been present since the mid-
1970s in the center of Valdivia, southern
Chile (39u489S, 73u149W) (Schlatter 1976).
This small group consists of approximately
of 50 juvenile, subadult, and adult males.
Because SASLs use publicspaces, there is a
risk of pathogen transmission between
SASLs and humans and their pets. We
performed postmortem examination in four
SASLs to determine cause of death and
assess presence of relevant pathogens.
Between March 2008 and December
2010 we necropsied four SASLs and per-
formed ancillary diagnostic studies. Two
SASLs (SASLs 1 and 2) were part of an
ecologic study and died during routine
anesthesia (1.2 mg/kg of tiletamin/zolaze-
pam, ZoletilH, delivered intramuscularly)
(Haulena 2008). Both animals died despite
being apparently healthy at the time of
darting. The two additional sea lions (SASL
3 and 4) were found emaciated on the
shore of the Valdivia River and died within
24 h of discovery. Serum samples to detect
antibodies against canine distemper virus
(CDV), canine parvovirus-2 (CPV-2),
Toxoplasma gondii,Leptospira interrogans
serovars Pomona, Icterohaemorrhagiae,
Hardjo, Bratislava, Copenhageni, Canicola;
Leptospira kirschneri serovar Grippoty-
phosa; and Leptospira biflexa serovar Patoc
were collected premortem from SASLs 1,
2, and 4. Blood from SASL 3 was plated on
MacConkey and blood agars.
Complete necropsies were performed
on all SASLs within 24 h of death.
Sections from major organs and tissues
(including brain) were fixed in 10%
neutral buffered formalin and processed
for histopathology. Samples of lung, liver,
and mesenteric, bronchial, and mediasti-
nal lymph nodes were collected from
SASLs 3 and 4 and were processed and
cultured, and the microorganisms were
identified by standard bacteriologic tech-
niques (Barrow and Feltham 2004). Gas-
trointestinal parasites were placed in 70%
ethanol and identified by light microscopy
(Carvajal et al. 1983; Mercado et al. 2010).
Immunohistochemistry (IHC) using a
monoclonal antibody against CDV nucle-
oprotein was performed on lung, medias-
tinal lymph node, brain, spleen, and
bladder (Stone et al. 2011). We also
performed IHC on kidney samples using
aLeptospira-specific polyclonal antibody
against L. interrogans serovars Bratislava,
Canicola, Hardjo, Icterohaemorrhagiae,
and Pomona, and against L. kirschneri
Grippotyphosa (Colegrove et al. 2005).
Serologic results are shown in Table 1.
Sea lion 1 was a 200-cm, 320-kg, adult
male. Antibodies to CDV (1:8), CPV-2
(1:64), and L. interrogans serovars Pomona
and Bratislava (.1:400) were detected. At
histopathology there was mild, nonsuppu-
rative meningoencephalitis and moderate,
multifocal neutrophilic and lymphoplasma-
cytic bronchopneumonia with epithelial
necrosis and abundant deposition of fibrin
in the bronchioles. Occasional bronchiolar
gland epithelial cells presented mild in-
tracytoplasmatic staining for morbillivirus
antigen. There was moderate multifocal
lymphoplasmacytic interstitial nephritis
and a few leptospires detected in the
renal tubules with the Warthin-Starry
silver stain and IHC (Fig. 1). Sea lion 2
was a 210-cm, 250-kg, adult male. Anti-
bodies against CPV-2 (1:64) and Toxo-
plasma gondii (1:256) were detected. The
same pattern of bronchopneumonia ob-
served in SASL 1 was found in SASL 2
but was milder. Sea lion 3 was a 120-cm,
65-kg, juvenile male. On postmortem
examination, 70%of the lung paren-
chyma presented a marked multifocal to
coalescing bronchointerstitial histiocytic
pneumonia. Gram-negative bacilli and
Gram-positive cocci were observed inside
macrophages in the lung, spleen, and
mediastinal and axillary lymph nodes.
There was moderate lymphoid depletion
in the spleen and most lymph nodes.
Proteus mirabilis and Staphylococcus sp.
(nonhemolytic) were isolated from lung,
spleen, and mediastinal and axillar lymph
nodes. Protozoal cysts (probably Sarcocys-
tis sp.) were found in the skeletal muscles.
Sea lion 4 was a 180-kg, 160-cm, subadult
male with antibodies against CDV (1:8)
and CPV-2 (1:8). This animal presented
the same pattern of bronchointerstitial
pneumonia found in SASL 3. Escherichia
coli and a nonhemolytic Staphylococcus
1. Antibody titers against selected pathogens in three South American sea lions (Otaria byronia),
Valdivia, Chile, between 2008–10.
Test performedSea lion 1 Sea lion 2 Sea lion 4
1:8 NR 1:8 Viral seroneutralization
1:64 1:64 1:8 Hemagglutination Inhibition
Leptospira interrogans serovar
1:800 NR NA Microagglutination
L. interrogans serovar Hardjo
NR NR NR Microagglutination
L. interrogans serovar
NR NR NA Microagglutination
L. interrogans serovar Pomona
NR NR Microagglutination
L. interrogans serovar Copenhageni
NR NR NR Microagglutination
L. interrogans serovar Canicola
NR NR NR Microagglutination
Leptospira kirschneri serovar
NR NR NR Microagglutination
Leptospira biflexa serovar Patoc
1:200 1:100 NA Microagglutination
NR NR NR Bengal rose
NR NR NR Plaque agglutination
NR NR NR Plaque agglutination
NR 1:256 NA Latex agglutination
CDV 5canine distemper virus; CPV-2 5canine parvovirus-2.
NR 5not reactive; NA 5not analyzed.
Tests performed at the Chilean Agricultural and Livestock Department Laboratories.
Tests performed in the laboratories of the College of Veterinary Medicine, University of Minnesota.
Both titers are shown when results from the two laboratories were different.
280 JOURNAL OF WILDLIFE DISEASES, VOL. 51, NO. 1, JANUARY 2015
sp. were isolated from lung, spleen, and
mesenteric and mediastinal lymph nodes.
Sea lions 1, 2, and 4 had severe
infections with the nematodes Contracae-
cum sp. and Pseudoterranova sp. A few
tapeworms (Diphyllobotrium sp.) were
found in SASLs 1 and 2. Sea lion 3 had
a low number of the trematode Ogmoga-
ster heptalineatus. The only histopa-
thologic change associated with these
parasites was moderate eosinophilic gas-
tritis in animals infected with Contracae-
cum sp. and Pseudoterranova sp.
Although SASLs 1 and 2 died during
anesthesia, postmortem findings indicate
that moderate to severe chronic infections
in the respiratory and renal systems could
have played a role during the anesthesia
(Haulena 2008). Another possibility is an
idiopathic adverse reaction to tiletamine-
zolazepam, a drug combination that has
caused apnea and death in otariids (Dabin
et al. 2002). The most probable cause of
death of SASLs 3 and 4 was pneumonia and
later systemic infection with Gram-positive
and Gram-negative opportunistic bacteria,
one of the most prevalent causes of natural
death in young otariids (Seguel et al. 2011).
Serologic and immunohistochemical find-
ings in SASL 1 and serology in SASL 4
indicate a low reaction to CDV or another
related morbillivirus. In pinnipeds there
have been outbreaks of CDV affecting seals
(Phocidae; Kuiken et al. 2006); however,
we know of no reports of CDV clinical
illness in eared seals (Otariidae). Canine
distemper is a common disease in dogs in
Valdivia (Ernst et al. 1997); thus it is
possible that dogs were the source of
CDV exposure in these SASLs, as has been
suggested in phocids (Kuiken et al. 2006).
In the case of CPV-2, the low antibody
titers (1:8 and 1:64) could represent
previous exposure to or cross-reaction with
an unknown parvovirus.
The serology, histopathology, and im-
munohistochemistry of SASL 1 are indic-
ative of chronic leptospirosis (Gulland
et al. 1996). Clinical leptospirosis is the
second most-common cause of stranding
in California sea lions (Zalophus califor-
nianus) (Greig et al. 2005). To our
1. Kidney photomicrograph from a South American sea lion (Otaria byronia), SASL 1. There are
occasional aggregates of Leptospira sp. spirochetes within a renal tubule (arrow), and occasional macrophages
that surround the affected tubule contain a large amount of partially degraded Leptospira sp. antigen (arrow
head). Immunohistochemistry for Leptospira sp. antigen counterstained with hematoxylin. Bar 525 mm.
knowledge this is the first report of L.
interrogans infection in SASLs.
The presence of T. gondii antibodies
suggests contamination of the river water
with cat feces (Miller et al. 2002). This
would not be surprising given the high (up
to 30%) prevalence of T. gondii in cats in
Valdivia (Ovalle et al. 2000). Toxoplasma
gondii antibody prevalence of up to 40%
has been found in California sea lions, and
there are some reports of encephalitis and
disseminated infection in otariids (re-
viewed in Dubey et al. 2003).
We have shown that SASLs are exposed
to domestic animal shared pathogens
(CDV, CPV-2, T. gondii) and are infected
with agents that can represent zoonotic
risk (L. interrogans,Contracaecum sp.,
Pseudoterranova sp., and Diphyllobotrium
sp.). This highlights the potential use of
marine mammals as animal and human
health sentinels in an urban environment.
We thank L. Huckstad, L. Osman, and
C. Valencia for help during captures.
Technical and financial support was pro-
vided by E. Paredes and J. Saliki. Funding
was provided by the DID-Universidad
Austral de Chile. M.A.S. was funded by a
CONICYT FB 0002 (2014) and a FON-
DECYT no. 3140538. C.V. was funded
by FONDECYT no. 11130305. This work
was conducted with permission from the
subsecretary of Fisheries (SUBPESCA).
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Submitted for publication 11 July 2013.
Accepted 3 June 2014.
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