Dyanna M. Lambourn1; Steven J. Jeffries1; P. Briggs Hall1, DVM; Michael M. Garner2, DVM, DACVP; Jack C. Rhyan3, DVM; Darla R. Ewalt3; Linda M. Polzin4; Norman F. Cheville5, DVM, PhD, DACVP
The Washington Department of Fish and Wildlife and National Marine Mammal Laboratory have been conducting annual blood testing on Pacific harbor seals on Gertrude Island and California sea lions at Shilshole Bay in Puget Sound, WA.8 Forty-eight of 200 harbor seals (12%) and four of 84 California sea lions (5%) had antibodies to Brucella abortus by the Brucella card test, Brucella buffered plate hemagglutination test, Rivanol test, and complement fixation procedure.1,3 The National Veterinary Services Laboratory (NVSL) isolated a Brucella sp. from four seropositive stranded harbor seals.5 This isolate is similar to a strain isolated from a seal in the United Kingdom.9 Necropsy of most affected seals revealed emaciation and lungworm infection. Histopathology revealed severe verminous pneumonia with intralesional Parafilaroides sp. lungworms.4,6,7 In Giemsa-stained sections, large numbers of minute bacterial coccobacilli were detected along the inner membrane of the uterus and within the gut lumen of some of the Parafilaroides sp. adult worms.6 Immunohistochemistry using a Brucella abortus antibody revealed large quantities of antigen within the gut lumen and/or uterus of several of the Parafilaroides sp., corresponding to areas where bacteria were detected within the worms.6,10 Labeled Brucella antigen was also detected within the cytoplasm of leukocytes in the surrounding pulmonary parenchyma.6 Bacteria within the uterus and gut lumen of the worms had ultrastructural morphology typical of Brucella sp.2,6 The significance of Brucella sp. infection to the lungworm and to the seal is unknown. Because seals frequent habitat shared by terrestrial mammals, and because seals are occasionally used for human consumption, there may be some risk of transmission to terrestrial wildlife, domestic livestock, and humans.
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2. Anderson, T.D. and N.F. Cheville. 1986. Ultrastructural morphometric analysis of Brucella abortus-infected trophoblasts in experimental placentitis. Bacterial replication occurs in rough endoplasmic reticulum. Am. J. Pathol. 124:226–237.
3. Brucellosis Eradication Uniform Methods and Rules, United States Department of Agriculture, Animal and Plant Health Inspection Service. Published March 6, 1992, with revisions, June 16, 1994.
4. Chitwood, M.B. and J.R. Lichtenfels. 1972. Identification of parasitic metazoa in tissue sections. Exper. Parasit. 32:461–464.
5. Ewalt, D.R. 1989. Comparison of three culture techniques for the isolation of Brucella abortus from bovine supramammary lymph nodes. J. Vet. Diagn. Invest. 1:227–230.
6. Garner, M.M., D.M. Lambourn, S.J. Jeffries, et al. 1997. Evidence of Brucella sp. infection in Parafilaroides sp. lungworms in a Pacific harbor seal (Phoca vitulina richardsii). J. Vet. Diagn. Invest. (In press).
7. Howard, E.B., J.O. Britt, G. Matsumoto. 1983. Parasitic diseases. In: Pathobiology of Marine Mammal Diseases. Howard EB (ed.), Pp. 128–213, CRC Press, Inc. Boca Raton, FL.
8. Lambourn, D.M., S.J. Jeffries, P.B. Hall, et al. 1996. Evidence of brucellosis in pacific harbor seals (Phoca vitulina richardsii) and California sea lions (Zalophus californianus) from Puget Sound, Washington. Abstract in 45th Annual Conference of the Wildlife Disease Association, July 21–25, 1996, Fairbanks, Alaska.
9. Ross, H.M., K.L. Jahans, A.P. MacMillan, R.J. Reid, P.M. Thompson, and M. Foster. 1996. Brucella species infection in North Sea and cetacean populations. Vet. Rec. 138:647–648.
10. Rhyan, J.C., K.L. Wilson, D.E. Burgess, et al. 1995. Immunohistochemical detection of Tritrichomonas foetus in formalin-fixed, paraffin-embedded sections of bovine placenta and fetal lung. J. Vet. Diagn. Invest. 7:98–101.