Author: Tania Hunt

 

I.  Literature Review                               [to next] [to top]  

Marine mammals are known to contract and carry many known zoonotic diseases. 1 2 Until recently human contact with these animals has been limited to whalers, fisherman, and indigenous peoples who hunt these animals for food. 3   Since the Marine Mammal Act was enacted in 1972 contact between sea mammals and humans has increased. 1   Efforts to rescue and rehabilitate sick and injured marine mammals have included the establishment of more wildlife rehabilitation centers and aquaria in the United States.  In addition to biologist, trainers and veterinarians, many of these facilities are staffed by volunteers, placing a larger population at the potential risk for zoonoses. 

          Also at risk are the growing number of tourist who participate in the swim-with-dolphins programs that are offered in coastal waters around the world. Some of these programs allow participants to swim with wild dolphins, of which the health status is unknown. 4 5 The health of the participants may also play a role in the risk of disease transmission for many of these programs are targeted to people with life threatening or debilitating diseases, like cancer. 6

Spekkfinger or blubber finger is one of the earliest documented zoonotic diseases transmissible to humans by marine mammals. While the causative agent has been reported as Staphylococcus or Erysipelothrix it is now believed to be caused by Mycoplamsa spp. This disease has historically been an affliction of whalers and fishermen, but recent reports of trainers and handlers contracting the skin and joint infection has appear in the literature.  This disease appears to result most often from bites. 3

Sealpox, a parapox virus, Mycobacterium murium, Erysipelothrix rhusiopathiae, and Staphylococcus aureus are other documented organisms causing concurrent infections of trainers, caretakers and the animals. 7 8 9   Two of three seal handlers working with Grey Seals ( Halichoerus grypus) developed raised caseous nodules on their hands, after working with the animals during an energetics study conducted in 1983.   The agent that was isolated from both the handlers and the seals was identified as a parapox virus commonly refered to as sealpox. 10   In 1974, four students acquired an E. rhusiopathiae infection from the carcass of a stranded pilot whale (Globicephala melas).   The organism was isolated from both the lesions on the hands of the students and the tissues from the whale collected at necropsy. 9   While in 1970, a long term M. murium infection was acquired by a trainer from the bite from a dolphin. 8   However, the S. aureus infections seen in 8 dolphins (Tursiops truncatus) and 14 oceanarium personnel in 1976, was determined by the researcher to not have been cross infections from either dolphin to trainer or trainer to dolphin. 7

Some more serious diseases have also been recorded in the literature, including Brucella spp. Leptospira spp., Mycobacterium bovis, and Influenza virus A. 3 11 12 13 14   However, documentation of humans actually acquiring these diseases from direct contact with marine mammals is lacking in some cases.   Foster reported the isolation of Brucella spp. from many different species of marine mammals.   These organisms were isolated from subcutaneous lesions, spleen and lymph nodes.13   At this time the infective potential of the Brucella spp. isolated was not yet known.   However, Brew reports that a researcher working with isolates of Brucella from marine mammals tested positive for strains of Brucella identical to those reported in the Foster study.  Based on this incident, the suggestion is made that those who come in contact with marine mammals are at risk for acquiring the disease. 12   Three workers conducting necropsies on sea lions ( Zalophus californianus californianus) in 1978, became ill, and developed serum agglutinating titers to Leptospira pomona.  Persons who are in contact with bodily fluid of seal lions, particularly urine and urine contaminated water are at risk for contracting this disease. 11   After the death of three seals ( Arctocephalus forsteri) in 1986 a seal trainer developed a pulmonary tuberculosis; the isolate of M.bovis from the seals and the seal trainer were reported as identical.   The barking and coughing behavior of seals and sea lions provides enough opportunity for aerosol transmission; trainers do not need to be in direct contact with contagious animals. 14   Influenza A is also reported as a disease with aerosol transmission.   The ecology of this virus appears to be complex involving birds, humans and other terrestrial mammals. 3,15 There are reports of people acquiring conjunctivitis from harbor seals ( Phoca vitulina) during an epidemic among these animals, while other studies have shown that the virus isolates from seals are capable of causing systemic disease and death in non-human primates. 3  

Tryland reports of many other diseases and epidemics in people that originated from contact and exposure to sea mammals. Most notably are the large numbers of indigenous peoples who have suffered from parasitic diseases such as Trichnellosis, Toxoplasmosis and Giardiasis from eating contaminated, undercooked meat, and drinking contaminated surface water. 3 Of the zoonotic disease reported in the literature these appear to be the most thoroughly described and understood.

         

II.  Research Question              [to next] [to top]          

 The documentation of humans infected with disease as a result of contact with marine mammals is rare.  Many of the incidents in the literature were reported as first time disease occurrences.  Much is said about those people in positions that put them in daily contact with both sick and apparently healthy animals; however, this information does not allow for the extrapolation of incidence of transmission, or the relative risk associated with transmission. Additionally, much of the reports found are dated by, in some cases, 30 years.   Considering the new dynamics of human to marine mammal contact, from trainer to tourist, more information is needed with regard to risk.   This project plans to document, via questionnaire and survey, the cases of disease acquired from marine mammals by workers and volunteers at facilities that house and hospitalize these animals. Facilities to be included are aquariums, oceanariums, and wildlife rehabilitation centers.   Assessments will be made as to the number of occurrences and the circumstances accompanying the human illnesses.

 

III.  References                                   [to top]          

          1.          Buck CD, and J. P. Schroeder. Public Health Significance of Marine Mammal Diseases. Cleveland, OH.: CRC Press, 1990.

          2.          Sweeney JCaR, S.H. Common Diseases of Small Cetaceans. J of the American Vet Med Association 1975;167:533-540.

          3.          Tryland M. Zoonoses of arctic marine mammals. The Infectious Disease Review 2000;2:55-64.

          4.          Smith CWS. Swimming with wild, friendly and playful dolphins is an experiance of a lifetime., 2000.http://www.dolphindreamteam.com/trips/Dol%20trip/dolphintrip.html

          5.          Reiman R, Basgall S. Dolphin Connection Programs, 1999. http://www.dolphinconnection.com/infoprint.txt

          6.          Taylor A. Dolphin 'therapy' for a dying child: About.com, 1989. http://newage.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Fwww.globalideasbank.org%2FGIB%2FBOV%2FBV-602.HTML

          7.          Streitfield MM, and Chapman, C.G. Staphylococcus aureus infections of captive dolphins (Tursiops truncatus) and oceanarium personnel. American Journal of Veterinary Research 1976;37:303-305.

          8.          Flowers DJ. Human infection due to Mycobacterium marinum after a dolphin bite. Journal of Clinical Pathology 1970;23:475-477.

          9.          Chastel C MO, Balouet G, Laban P, Lucas A. The student, the cetacean and swine-fever. A minor epidemic after dissection of a globicephale. Nouv Presse Med 1975;Jun 14;4(24)::1803-5.

          10.          Hicks BDaW, G.A. Sealpox in captive gray seals ( Halichoerus grypus) and their handlers. Journal of Wildlife Diseases 1987;23:1-6.

          11.          Smith AW, Vedros, N.A., Akers, T.G., and Gilmartin, W.G.,. Hazards of disease transfer from marine mammals to mammals: Review and recent findings. Journal of the American Veterinary Medical Association 1978;173:1131-1133.

          12.          Brew SD, Perrett LL, Stack JA, et al. Human exposure to Brucella recovered from a sea mammal [letter]. Veterinary Record 1999;144:483.

          13.          Foster. G J, K.L., Reid, R.J. and Ross, H.M. Isolation of Brucella species from cetaceans, seals and an otter. Veterinary Record 1996;138:583-586.

          14.          Thompson PJ, Cousins DV, Gow BL, et al. Seals, seal trainers, and mycobacterial infection. American Review of Respiratory Disease 1993;147:164-7.

          15.          Alexander DJ, Brown IH. Recent zoonoses caused by influenza A viruses. Revue Scientifique et Technique Office International des Epizooties 2000;19:197-225.