Abstract

We report two separate cases of renal lithiasis and pyelonephritis in the West Indian manatee (Trichechus manatus sp.). The first case was a 306 cm long, 443.5 kg female manatee from the Florida Everglades that was reported injured by local residents. On observation, she was lethargic, emaciated and had a significant list. The animal was captured and transported to a rehabilitation facility. Initial blood values indicated an elevated CK and electrolyte abnormalities including hypoglycemia, hypernatremia, hypokalemia, hyperchloridemia, and a low iron level (Table 1). Although these electrolyte abnormalities were mostly resolved following fluid administration, the manatee died several days later. At necropsy, the right kidney (25 cm x 18 cm x 7 cm) was over three times the size of the left kidney (18.5 cm x 11cm x 4 cm). The left kidney had a 2.5 x 3.5 cm lesion in the caudal pole that contained two large calculi each measuring 2.0 cm in maximum diameter. The left renal pelvis was contracted and fibrotic. Histopathology revealed a chronic active diffuse pyelonephritis, interstitial nephritis, and glomerulonephritis with marked cortical atrophy. The right kidney contained a 2.5 x 4.0 cm lesion in the caudal pole that had a gritty necrotic center. Histopathology revealed similar lesions in the right kidney except that the lesions were multifocal with areas of active pyelonephritis. We also observed a large fluid-filled follicle measuring approximately 2.7 x 1.8 1.5 cm on the left caudal margin of the thyroid.

Table 1. CBC and chemistry abnormalities.

Culture of the left kidney showed predominantly Edwardsiella tarda (65%) with remaining growth consisting of a non-hemolytic streptococcus species. Culture of the right kidney grew E. tarda (20%), Aeromonas sobria (20%), α-hemolytic streptococcus (20%), and miscellaneous Clostridium species. Culture of the right kidney urolith isolated E. tarda, A. sobri, and a non-hemolytic streptococcus. The urolith was analyzed and its surface layer consisted of 75% calcium carbonate and 25% calcium phosphate (apatite). The body of the stone consisted of 100% calcium carbonate. No explanation for the asymmetrical body posture was determined.

The second case was a female manatee from Laguna del Tesoro (Treasure lagoon) in the Ciénaga de Zapata, Cuba. Local residents reported the manatee acting lethargic, listless, and being very emaciated. A local biologist observed the manatee alive immediately prior to the arrival of the rescue team. The manatee was dead at the time of the rescue team's arrival. A field necropsy was performed. The manatee weighed approximately 350 kg. Both kidneys and associated ureters were grossly enlarged with a severe nephropathy. Nodules of various sizes were present throughout both kidneys. The right kidney measured 50 x 30 cm, and weighed 15 kg. On cut surfaces of the right kidney there was a large amount of pasty, purulent, white material present along with many large and small calculi. The left kidney measured 28 x 18 cm and had multiple abscesses present diffusely throughout the parenchyma. The kidney capsule was fibrotic and had many superficial irregularities. Actinomyces renale was isolated as the causative agent of the suppurative process of the kidneys. It was concluded that the manatee died due to a renal lithiasis complicated by an A. renale infection.

The authors are unaware of any previously published reports of renal lithiasis in West Indian manatees. Both of these animals were severely emaciated and were very lethargic.