Abstract

A five year old female resident killer whale (A57) was observed at 0800 hours, by local residents of Saltery Bay, Powell River, B.C., listing and swimming in a circular pattern close to shore. At 1500 hours she died, her carcass was then towed to the shoreline for a necropsy.

This animal's life history has been well documented since birth by field biologists. She belonged to A5-pod, a well known resident group.

Necropsy

On external physical examination, the 4.0 meter long body was in good condition. The only significant abnormalities were found with the jaw and skin. Numerous, small punctate like erosions "pox-like," often associated with linear wounds, and occasional teeth rake marks are present on the surface of the skin in many areas, but confined primarily to the lateral body wall. These particular lesions are approximately three to four millimeters in diameter. There are small areas, approximately one centimeter in diameter, on the dorsal mid line between the blowhole and insertion of the dorsal fin; with roughed skin. Further examination demonstrates some downward extension of the epidermis into the underlying hypodermis and blubber. Some blood-tinged fluid is present beneath the blubber in this area. The most dramatic external alteration is confined to the lower jaw. The tip of the jaw projects three centimeters beyond the maxilla; as a result, the teeth are malaligned. On the one side of the jaw the tips of the mandibular teeth project into the hard palate on the glossal side of the dental arch. In focal areas there is also evidence of apparent scar formation immediately adjacent to abnormally projecting teeth. Due to malocclusions there are extensive tooth wear and cranial slab fractures involving the anterior aspect of several maxillary teeth. Two teeth (#8, #9) are grossly fractured and mobile.

The temporal mandibular joint (TMJ) was unremarkable. Abundant froth was found in the trachea and mainstem bronchi and the lungs are mildly edematous. "Chicken fat" clots occur in the right and left ventricles. No feed material was present in any of the stomach compartments and a moderate number of Anisakis spp. nematodes are found in both the glandular and non glandular portions of stomach. A small quantity of mucoid brownish liquid was associated with these parasites. There was minimal petechiation on the gastric. The entire small and large intestine was essentially devoid of any feed material. Only a small quantity of greenish tinged fluid was found in the duodenum. Mesenteric lymph nodes are prominent and edematous. The hepatic lymph nodes also appear slightly enlarged and edematous. The spleen was enlarged and autolytic. No significant alterations are present in the large muscle masses. Focal hemorrhages are noted on the meninges of the right cerebral hemisphere but do not extend to the underlying cerebral cortex.

Bacteriology

Heavy Erysipelothrix rhusiopathiae from the lung, liver, spleen, hepatic lymph nodes, mesenteric lymph nodes, brain and intestine. Heavy E. rhusiopathiae also from pulp cavity of tooth #8 and #9. Vagina and blowholes cultures yielded Aeromonas spp. Heavy growth of Edwardsiella tarda from the intestine.

 All levels appear to be within normal ranges for cetaceans.

 Virology

 No viruses were isolated.

Histopathology

Several sections of lung demonstrate diffuse congestion, hyperemia, edema and focal alveolar hemorrhages. Occasional bacterial colonies are found within septal capillaries and pulmonary blood vessels. Bacterial sludging is associated with large numbers of neutrophils within several pulmonary vessels. Gram staining demonstrates these bacteria to be gram positive coccobacilli. Several lymph nodes are also examined microscopically. These lymph nodes demonstrate diffuse edema, prominent lymphoid follicles and several active germinal centres. Within some nodes there are also extensive hemorrhages within the medullary channels. There is relative paucity of white versus red pulp in sections of spleen and increased numbers of macrophages are noted within the splenic red pulp. No visible lesions in several sections of glandular stomach. No visible lesions in stratofoed portions of stomach. Occasional cross section of nematode larvae and ova are found within the lumen of cestions of intestine. No significant alterations, however, within the intestinal lining. Intrahepatic biliary stasis is noted in sections of the liver. There also moderate cloudy swelling in several hepatocytes. Focally extensive meningeal hemorrhage was noted in sections of cerebrum. Meningeal vessels are congested and hyperemic and bacterial aggregates are also noted in some menegeal vessels. Similarly bacterial colonies are found in some vessels in these various areas. Gram staining demonstrates these to be gram positive coccobacilli. A wide variety of sections of cerebrum from both right and left hemispheres as well as cerebellum thalamus, medulla and obex are also examined. Some sections of cerebellum also demonstrate bacteria associated with intravascular fibrin thrombi. No other primary alterations, however, are present within the many sections of brain. No visible lesions in thyroid, several sections of myocardium or kidney. Apart from extensive pigmentation, no significant lesions noted in most sections of skin. Within a few sections, however, there are focal aggregations of lymphocytes within the dermis. The upper dermis is congested and hyperemic. Within focal areas of the surface of the epidermis there are large colonies of filamentous and other bacteria associated with sloughing cells. Focal nonspecific degenerative alterations are noted in areas of the central and upper stratum corneum.

Radiology

A series of dorsal-ventral (DV) and oblique exposures were taken of the complete jaw which detail the dramatic malocclusion, particularly on the left side. Full set of twelve teeth were evident in all four quadrants. The first tooth in each quadrant was unexposed. The slab fractures of teeth #8 and 9 are apparent and associated with extensive osteomyelitis; other teeth integrity was for the most part healthy.

Conclusion

There is evidence of overwhelming septicemia due to infection with Erysipelothrix rhusiopathiae. The changes within the blood vessels of the brain and lung demonstrates some, sludging, fibrin thrombi and aggregations of bacteria strongly suggestive of Erysipelothrix. No other primary alterations are noted in the wide variety of other organs examined microscopically. Death in this animal is attributed to septicemia with E. rhusiopathiae.

Erysipelas rhusiopathiae is a gram positive rod.¹⁰ Erysipelas infections have been documented within several captive pinniped and nine cetacean species.^1,2,8 This bacteria is very resilient, it can persist within aquatic and terrestrial environments and remarkably resist disinfection.¹ Positive cultures of E. rhusiopathiae have even survived from frozen fish.⁹ It is well known as the most serious infectious disease of captive cetaceans.⁶ Potential for zoonosis is significant. Suer, et al. (1988), have found that this opportunistic organism can inhabit the oral cavity of pinnipeds. Zoonosis from Erysipelas can develop from handling pinnipeds, cetaceans, fish, and domestic livestock.^7,9 Signs of infection are difficult to determine. Usually there are two types of the disease occurring in captive cetaceans -septicemic or dermal. Symptoms of the disease are often associated with inappetance, lethargy, leukocytosis, behavioural changes, and depression.^1,2 Calle et al. (1993) found that a captive beluga whale had 7 weeks of partial anorexia and 6 days of anorexia before positive signs of the disease were apparent. Inanition was considerable as indicated from the necropsy. The onset of signs was rapid (7 hours), leaving little time for medical intervention. Recent serological assays may help with the characterization and treatment of this disease in captive cetaceans.^1,5 The best defense or control of potential infections in captive cetaceans has been primarily through the provision of good hygiene practice in dietary storage and preparation, and in acquiring high-quality fish (McBain per. com.).³ Vaccination has been used with some controversy, where some aquaria have experienced problems with the bacterin.^4,7

The inference of this case illustrates the potential for susceptibility of an opportunistic gram positive bacteria, like Erysipelas rhusiopathiae, leading to a septicemic disease from a congenital defect within a free-ranging cetacean.

References

1.  Calle, P.P., D.E. Kenny, and R.A. Cook. 1993. Successful treatment of suspected erysipelas septicemia in a beluga whale (Delphinapterus leucas). Zoo Biology 12:483-490.

2.  Dierauf, L. Marine Mammal Medicine Handbook. 1990. CRC Press, Boston. Pp. 27, 77, 78,124,165.

3.  Geraci, J.R, R.M. Sauer, and W. Medway. 1966. Erysipelas in dolphins. 1966. American Journal of Veterinary Research 27:597.

4.  Gilmartin, W.G, J.F. Allen, and S.H. Ridgway. 1971. Vaccination of porpoise (Tursiops truncatus) against Erysipelas rhusiopathiae infection. Journal of Wildlife Diseases 7:292.

5.  Jones, J.C, R.A. Patterson, and B. L. Middlebrooks. 1995. A biotin-avidin amplified elisa for the detection of antibodies against Erysipelas rhusiopathiae in captive dolphins. 26th Annual International Association for Aquatic Animal Medicine (IAAAM). Pp 54.

6.  Merck Veterinary Manual. 6th edition. 1986. Merck & Co. Inc. Rahway, N.J. USA. Pp. 971-972.

7.  Merck Veterinary Manual. 7th edition. 1991. Merck & Co. Inc. Rahway, N.J. USA. Pp. 1040.

8.  Ridgway, S.H. 1972. Mammals of the Sea, Biology and Medicine. Charles C. Thomas. Springfield, IL, Pp. 372, 377, 379, 653, 701, 702, 704, 712.

9.  Suer, L.D., and N.A. Vedros. 1988. Erysipelas rhusiopathiae. I. Isolation and characterization from pinnipeds and bite/abrasion wounds in humans. Diseases of Aquatic Organisms 5: 1.

10. Thomas, C.G.A. 1988. Medical Microbiology. 6th edition. Baillere Tindall, London, Philadelphia, Toronto, Sydney, Tokyo, Pp. 269-270.