Abstract
The 24-year-old, 825 kg adult male Steller sea lion (SSL), captured in Kuril Islands (Okhotsk Sea) at the age of 1 year, was maintained in enclosures with salt water pools, well trained, and then involved in different recreational show programs. The animal appeared to be healthy until late September 2012 when the seal showed first signs of unstable and decreased nutritional activity, selectivity in the case of fish, up to temporary complete refusal of food. The results of hematological tests performed (the animal was trained for voluntary blood sampling) appeared to be within the seasonal individual normal ranges (Table 1). Repeated treatments with probiotics and enzymatic drugs resolved most of clinical signs over the following three months. The appetite was totally restored, but the body weight started to decrease (615 kg in December 2012). Drop in the level of serum albumins (29.8 g/l) was the only hematological deviation at this time.
Progressive deterioration of the seal's health state was noted since the middle of January 2013: nutritional activity decreased dramatically, and the body weight gradually went down. The use of appetite stimulants (trimetabol, megace) helped to support nutritional activity, motion, husbandry and trained behaviors of the seal over the subsequent period and allowed to implement the prescribed treatment (courses of antibiotics and antimycotics, sorbents, enzymes, probiotics, fluid therapy). The body mass of the seal continued to decrease despite consumption of sufficient amount of food. Marked progressive hematological abnormalities (anemia, neutrophilic leukocytosis with a left shift, aneosinophilia, elevated ALT, AST, iron, evident ALP, TP, and globulins increase) were observed during the last week of the animal's life (Table 1). The peculiarities of the clinical course and the absence of positive effect of treatment allowed suggesting probable malignant nature of the disease. The death of the seal occurred at the end of March 2013 against the manifestations of anorexia, total immobility, and melena.
Renal tumor with widespread metastases involving omentum, spleen, liver, lymph nodes and adrenal gland was revealed at necropsy. The primary lesion was located in the right kidney. It appeared as several small (≈ 1 cm) whitish subcapsular foci, alveolate on cut surface, with soft to liquid necrotic centers yellowish-brown in color. On histology the initial focus showed the pattern of low differentiated solid carcinoma. Histogenetically the neoplasm originated from the renal tubule epithelium. Multiple whitish nodules and nodes (1 to 20 cm in diameter) with evident sponginess on incision and jelly-like reddish-brown mass in central zones of some of the metastases were found throughout the enlarged congested spleen and liver. Most of the lymph nodes from different body sites appeared to be enlarged (particularly cervical), tuberous, with spongious structure and soft to liquid yellowish mass on cut. Histological examination of spleen, liver, lymph nodes and adrenal gland revealed large masses of proliferating low differentiated neoplastic cells with multiple areas of necroses and hemorrhages. The carcinoma cells' morphology was identical to what had been initially defined in the kidney histological specimen. We didn't find literature records of renal cell carcinoma in SSL, and it's possible that this is the first reported case in this species. The relationship with urogenital carcinoma, prevalent in California sea lions,1-3 needs to be investigated.
Table 1. Hematological and serum chemistry indices of Steller sea lion
|
Indices
|
Units
|
Individual normative values*
X (limits), n = 7
|
One week prior to death
|
Day of death
|
|
RBC
|
1012/l
|
5.4 (4.7–5.7)
|
4.3
|
4.1
|
|
Hb
|
g/l
|
175.9 (165–191)
|
142
|
130
|
|
Ht
|
%
|
46.7 (42–51)
|
45
|
39
|
|
MCH
|
pg
|
32.9 (29.2–36.5)
|
32.8
|
31.2
|
|
ESR
|
mm/h
|
5 (4–6)
|
7
|
25
|
|
WBC
|
109/l
|
7.9 (6.7–9.3)
|
27.2
|
51.2
|
|
Neutrophils (bands)
|
109/l
|
0.02 (0–0.08)
|
2.4
|
14.8
|
|
Neutrophils (segments)
|
109/l
|
4.8 (4.1–6.1)
|
20.4
|
27.1
|
|
Eosinophils
|
109/l
|
0.2 (0–0.3)
|
0
|
0
|
|
Lymphocytes
|
109/l
|
2.6 (1.7–3.2)
|
2.7
|
5.6
|
|
Monocytes
|
109/l
|
0.3 (0.2–0.5)
|
1.6
|
2.0
|
|
ALT
|
IU/l
|
46.1 (31.5–61.9)
|
217
|
20.6
|
|
AST
|
IU/l
|
58.5 (4.87)
|
78
|
27.7
|
|
Bilirubin (total)
|
µmol/l
|
3.6 (0.2–7.0)
|
7.2
|
n/d
|
|
CK
|
IU/l
|
49.8 (47.4–51.0)
|
n/d
|
|
GGT
|
IU/l
|
44.9 (43.1–46.2)
|
300.5
|
|
Urea
|
mmol/l
|
11.4 (10.9–11.8)
|
n/d
|
|
Creatinine
|
µmol/l
|
106.9 (82.0–123.8)
|
101
|
|
LDH
|
IU/l
|
900.1 (831.0–989.8)
|
n/d
|
|
ALP
|
IU/l
|
83.1 (68.9–107.1)
|
2054
|
64.4
|
|
Glucose
|
mmol/l
|
4.9 (4.6–5.4)
|
5.4
|
5
|
|
Cholesterol
|
mmol/l
|
4.9 (3.8–5.5)
|
4.2
|
n/d
|
|
Total protein
|
g/l
|
75.2 (73.1–76.9)
|
123
|
100
|
|
Albumins
|
g/l
|
35.4 (34.2–37.7)
|
25.6
|
31.4
|
|
Globulins
|
g/l
|
39.8 (35.4–42.7)
|
97.4
|
68.6
|
|
Fibrinogen
|
g/l
|
2.2 (1.2–4.2)
|
0.1
|
n/d
|
|
Sodium
|
mmol/l
|
146.8 (143.0–152.2)
|
149.5
|
|
Potassium
|
mmol/l
|
4.2 (3.73–4.54)
|
4.45
|
|
Calcium
|
mmol/l
|
2.45 (2.3–2.6)
|
n/d
|
3.1
|
|
Iron
|
mmol/l
|
12.7 (9.2–16.1)
|
49.7
|
n/d
|
* - Actual values are for the period out of molt. The data were achieved long before the disease onset and can be used as reference points for adult SSL.
n/d - data not available.
Acknowledgements
The authors would like to express sincere gratitude to Dr. Judy St. Leger of the Sea World Parks & Entertainment for support and valuable assistance.
* Presenting author
Literature Cited
1. Newman SJ, Smith SA. Marine mammal neoplasia: a review. Vet Pathol. 2006;43:865–880.
2. Bossart GD. Emerging diseases in marine mammals: from dolphins to manatees. Microbe. 2007;2(11):544-549.
3. Colegrove KM, Gulland FMD, Naydan DK, Lowenstine LJ. Tumor morphology and immunohistochemical expression of estrogen receptor, progesterone receptor, p53, and Ki67 in urogenital carcinomas of California sea lions (Zalophus californianus). Vet Pathol. 2009;46:642–655.