Three neonatal and two older Pacific walrus (Odobenus rosmarus divergent) were diagnosed with enteric salmonellosis. Clinical signs in the neonates consisted of an acute onset of partial to complete anorexia, regurgitation, diarrhea, lethargy, depression, and weight loss. The older walrus were asymptomatic when culture positive.

The neonates had arrived at the Aquarium for Wildlife Conservation in May 1994 at approximately 1 month of age. They were enteric pathogen culture negative at that time. One month later, all three became ill within 72 hours (27-29 June). Salmonella muenchen was isolated from feces of all three; Campylobacter jejuni was also cultured from one. Clinical signs rapidly resolved with antibiotic therapy. One month later (23-24 July) all three developed recurrent illness. Salmonella anatum was isolated from all three and Salmonella Quencher was also isolated from one. Walrus again rapidly responded to treatment. On both occasions all three walrus converted to culture negative status during or immediately after treatment. Three months after initial illness the three walrus were asymptomatic but enteric culture positive for Salmonella muenchen, Salmonella alachua, or an untypeable Salmonella sp.

Treatments included an oral electrolyte solution, Enrofloxacin (1,020 days), nystatin (10-24 days), and acidophilus (10-24 days). In addition, in some cases, sucralfate and ranitidine were administered (10-18 days). There was rapid improvement in clinical condition within hours of treatment onset. Hematologic and biochemical results were normal and fecal occult blood tests were frequently positive when clinical enteritis occurred. Direct fecal examination occasionally demonstrated red blood cells but parasites were not observed. Fecal electron microscopy did not reveal evidence of enteric viral infection.

The two older walrus (2 and 12 years old) were housed in a separate area of the aquarium, were clinically normal, and had previously been enteric pathogen culture negative. In August 1994 Salmonella hadat was isolated from feces of both. Attempts to resolve the infection with two regimens of oral antibiotic therapy (tetracycline and Trimethoprim ulfamethoxazole were unsuccessful. Although the two older walrus have remained asymptomatic, the 2 year old developed gastroenteritis associated with gastrointestinal foreign bodies in October 1994. At that time Salmonella Istanbul was isolated from vomitus and Salmonella hadar from feces.

Factors which may have predisposed the neonates to infection include lack of maternal colostral antibodies, delayed voluntary nursing (2 days-5 weeks), and a dietary associated enteritis. The later resulted from composition abnormalities when the formula was reconstituted and intolerance of an alternative formula utilizing lactase treated heavy cream. An increased volume fed to compensate for the poor utilization of this formula exacerbated the problem. The result may have been an increased susceptibility to enteric pathogens. Isolation of Salmonella from both captive and free-ranging pinnipeds, and from various sources in a marine aquarium, have been reported.^1,2,3,5 The source(s) of Salmonella and Campylobacter for the walrus were not identified. Cultures of food fish (herring, smelt, capelin, squid), milk replacement formula (Multimilk, Pet-Ag, Inc. Elgin, IL), exhibit pool and tap water, and the environment were all negative. California sea lions (Zalophus californianus) housed in an area adjacent to the neonates were also enteric pathogen culture negative initially; one later became enteric Salmonella alachua culture positive. One sea otter (Enhydra lutris) and one harbor seal (Phoca vitulina) housed near the older walrus were enteric pathogen culture negative. One employee caring for the ill walcus contracted Salmonella anatum infection and developed clinical enteritis. Gulls are well documented to harbor and shed both Salmonella and Campylobacter.⁴ They were locally abundant and may have been the source of infection.

Acknowledgments

The authors thank Noreen Connolly, Jim Dress, Gail Reilly, Martha Hiatt-Saif, and Guenter Skammel for the excellent care given to the walrus and Dr. Patrick McDonough and Valerie Patton, Diagnostic Laboratory, Cornell College of Veterinary Medicine for Salmonella cultures.

References

1.  Beckmen, K. and S. Nolan. 1994. Salmonella serotypes in pinnipeds at a rehabilitation center. Proc. Int. Assoc. Aq. An. Med. 25:162.

2.  Dunn, J.L. 1990. Bacterial and mycolic diseases of cetaceans and pinnipeds. In: CRC Handbook of Marine Mammal Medicine: Health, Disease, and Rehabilitation. Dierauf, L.A. (ed.). CRC Press,Boca Raton, F1., Pp 73-87.

3.  Gilmartin,W.G., P.M. Vainik and V.M. Neil. 1979. Salmonellae in feral pinnipeds off the southern California coast. J. Wild.Dis. 15(4):511-514.

4.  Quessy, S. and S. Messier.1992. Prevalence of Salmonella spp., Campylobacter spp., and Listeria spp. in ring-billed gulls (Laws delawarensis). J. Wild. Dis. 28(4):526-531.

5.  Sasaki, D.M. and H.P. Minette. 1985. Isolation of Salmonella in a public aquarium. J. Am. Vet. Med. Assoc. 187(11): 1221-1222.