Marine Mammal Zoonotic Bacteria 
 
  1. Brucella
  2. Erysipelothrix
  3. Leptospira
  4. Mycobacterium
  5. Mycoplasma

Brucella

In 1999, a researcher suffered headaches, lassitude and a severe sinusitis after exposure to marine mammal strains of Brucella with which the worker was in contact. The symptoms resolved in one week after treatment with doxycycline and rifampin. The researcher had a positive titer for Brucella, and the organism was cultured from blood samples. PCR-RFLP was used to positively identify the isolates as being comparable to marine mammal Brucella (Brew and Staunton 1999).

Organisms
Brucella ssp. are gram-negative intracellular bacteria and are a major source of zoonoses worldwide. B. melitensus, B. abortus, and B. suis are some species commonly recognized to play a role in human and animal health. Nomenclature for marine mammal strains of Brucella has not yet been fully developed, but B. maris and B. pinnipedia have so far been named. Transmission occurs primarily through contact with aborted fetal material, and consumption of contaminated milk.

Clinical disease in marine mammals
The bacteria have been isolated from multiple species of marine mammals, including pinnipeds, cetaceans and otters. Abortion and meningoencephalitis have been reported in dolphins from which the bacteria was isolated, but in the majority of cases, the animals did not demonstrate clinical disease (Godfroid 2002).

Clinical disease in humans
Symptoms can vary depending on the chronicity of the infection, ranging from acute "flu-like" symptoms (headaches, fever, myalgia, and malaise) to more chronic symptoms (arthritis, orchiepididymitis, and fatigue). Neurological symptoms are rare, being seen in less than 5% of cases. Serologic tests for Brucella are available, but culture is the most definitive test for diagnosis (Centers for Disease Control 2001).

Treatment
Doxycycline and rifampin are the recommended therapies.  Other treatment has been associated with recurrence.

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Erysipelothrix 
In 1975, four students from the Laboratoire de l'Institut Scientifique et Technique des PÍches Maritimes (Scientific and Technical Institute of Maritime Fishing) acquired a cutaneous Erysipelothrix rhusiopathiae infection from a beached pilot whale (Globicephala melaena). The organism was isolated from both the whale and the affected students (Chastel, Measure et al. 1975).

Organism
Erysipelothrix rhusiopathiae is a gram-positive, facultative anaerobic rod, and is recognized as the causative agent of swine erysipelas.

Clinical disease in marine mammals
Cetacea appear to be more susceptible than pinnipeds and can develop septicemia, endocarditis, and chronic skin abscessation (Couch, Fournie et al. 1993; Kinsel, Boehm et al. 1997). The characteristic rhomboid cutaneous lesions, which are caused by thrombosis of peripheral arteries and local tissue infarction, can also be seen (Sweeney and Ridgway 1975).

Clinical disease in humans
Infection in humans is usually associated with occupational and recreational exposure. The bacteria enter through breaks in the skin and infection can present in three clinical forms:

1. Erysipeloid form: localized, self-limiting cellulitis that develops around site of inoculation.
2. Cutaneous form: a more severe and diffuse infection.
3. Septicemic form: most severe and rare form with or without cutaneous lesions. Associated with arthritis and/or endocarditis with valvular destruction (Artz, Szabo et al. 2001).

Treatment
Erysipelothrix is susceptible to penicillins and cephalosporins.

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Leptospira
During the course of a 5 year study (1972-1977), three researchers became ill after exposure to California sea lions (Zalophus californianus) that were infected with Leptospira. The two workers with more severe illness became infected after necropsying a sea lion. All three developed serum agglutinating antibody titers to Leptospira interrogans serovar  pomona (Smith, Vedros et al. 1978).

Organism
Leptospira interrogans serovar pomona, is one of 200 serovars within this species of spirochete bacteria. For this and other potentially zoonotic serovars, transmission occurs directly between mammalian hosts and indirectly through exposure to contaminated water and soil.

Clinical disease in marine mammals
Renal disease has been observed in harbor seals (Phoca vitulina), and more commonly in California sea lions (Zalophus californianus) and fur seals (Arctocephalus spp.) (Gulland, Koski et al. 1996; Stamper, Gulland et al. 1998). The disease causes tubular necrosis consistent with interstitial nephritis. Clinical signs include anorexia, dehydration and polydipsia. Cytology and serum chemistry reveals a leukocytosis and high serum phosphorus, urea nitrogen and creatinine levels.

Clinical disease in humans
In the largest outbreak of environmentally-acquired leptospirosis, the most common symptoms reported were chills, headache, myalgia, eye pain, reddened eyes and diarrhea. Clinical signs included those consistent with acute hepatitis and renal failure. Diagnostics revealed elevated liver enzymes, bilirubinemia, thrombocytopenia, proteinuria, hematuria, and elevated creatinine (Morgan, Bornstein et al. 2002).

Treatment
Leptospira are susceptible to penicillins.

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Mycobacterium
There is one reported case of an animal handler acquiring skin lesions similar to the cutaneous mycobacterosis lesions seen on a manatee which the handler was working (Howard 1983).

In 1968, a dolphin trainer working with a bottle-nosed dolphin (Tursiops truncatus) was bitten and subsequently developed dermal abscesses. Mycobacterium marinum was cultured from aspirates taken from the lesions on the trainer's hands (Flowers 1970).

In 1988, a seal trainer from western Australia was diagnosed with Mycobacterium bovis tuberculosis.  Diagnosis was made after the trainer developed a dry productive cough, exercise intolerance, and weight loss. Bacterial isolates from the trainer and the seals with which he worked were identical based on gel electrophoresis  (Thompson, Cousins et al. 1993).

Organism
Mycobacterium spp. are gram-positive acid-fast rods. Mycobacterium marinum is more commonly regarded as a salt- and fresh-water fish pathogen, while M. bovis primarily affects cattle and is an important zoonotic agent worldwide.

Mycobacterium marinum

Clinical disease in marine mammals
The organism causes dermal abscesses when infection is local, and pulmonary tuberculosis or generalized abscessation with spreading infection (Tryland 2000).

Clinical disease in humans

This disease may also be called fish handler's disease or swimming pool granuloma in humans. The organism usually enters through breaks in the skin after host contact with contaminated water. Local infection results in a nodular lymphangitis with or without lymphadenitis. Skin lesions can ulcerate, and spreading infection can cause tenosynovitis, arthritis, and osteitis (Ryncarz 1999).

Mycobacterium bovis


Clinical disease in marine mammals
Pathological findings in pinnipeds include pulmonary granulomas, lesions in the liver , draining lymph nodes, and tuberculous meningitis (Forshaw and Phelps 1991). Animals may also have subclinical infections.

Clinical disease in humans

Humans are usually infected with M. bovis from drinking contaminated cows milk. Infection can causes pulmonary tuberculosis, cervical lymphandenopathy, and Lupus vulgaris (chronic skin tuberculosis). Urogenital infections have also been reported (Cosivi, Grange et al. 1998).

Treatment

Common treatment for mycobacteriosis is long-term streptomycin and rifampin.

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Mycoplasma (Seal Finger)
While studying seal behavior at the New England Aquarium in 1979, a psychologist was bitten by a harbor seal (Phoca vitulina). Treatment with penicillin and oxacillin resulted in the resolution of symptoms, but the infection reappeared weeks later. The patient was then successfully treated with a 3 week course of tetracycline (Markham and Polk 1979).

In 1980, a graduate student was stabbed with a necropsy knife while working on a sea lion carcass. Clinical symptoms worsened after treatment with dicloxacillin. Radiographs showed periosteal reaction indicative of an osteitis underlying the cutaneous infection. Finally, treatment with tetracycline resolved the infection (Sargent 1980).

In 1990, a wildlife ranger was bitten while returning a seal to the ocean; he subsequently developed an skin infection. A two-week course of treatment with amoxicillin led to a persistent infection, and symptoms continued to persist after a change in antibiotics to flucloxacillin. Radiographs taken of the affected digit showed demineralization of phalanx 2 of the thumb suggestive of an osteitis. Finally a four-week course of treatment with tetracycline cured the infection (Eadie, Lee et al. 1990).

In 1998, a trainer working at the New England Aquarium was bitten by a harbor seal. Treatment was with tetracycline. Cultures taken from the trainers infected digit and the oral cavity of the seal isolated the same strain of Mycoplasma (Baker, Ruoff et al. 1998).

Organism
Mycoplasmas are gram-negative coccobacilli that lack a cell wall.

Clinical disease in marine mammals
M. phocacerebrale, M. phocidae, and M. phocarhinis were isolated from harbor seals (Phoca vitulina) during an epidemic in New England (1980) and in the Baltic Sea (1989) (Baker, Ruoff et al. 1998). Mass mortality due to mycoplasmal pneumonia has been documented; however, pinnipeds likely carry these organisms as part of their normal flora.

Clinical disease in humans
The local infection in humans with M. phocacerebrale (possibly other Mycoplasma species as well) isolated from marine mammals is commonly referred to as "seal finger". The organism enters through breaks in the skin, and infection can occur after contact with pinniped skin and commonly after a bite from seals and sea lions.

Infection causes local erythema and nodules at the site of inoculation, with progressive swelling that can be severely painful. If left untreated (or treated with inappropriate antibiotics), the infection can progress to cellulitis, tenosynovitis, and/or arthritis (Hartley, Pitcher 2002).

Treatment
Mycoplasma are susceptible to tetracyclines and are resistant to penicillins and erythromycins.  Treatment of severe cases may include arthrodesis or amputation.

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