Abstract
"Seal finger" is a potentially serious infection that may develop in people that have been bitten by pinnipeds or that have punctured their skin with blades or needles contaminated by pinniped body fluids. Recent studies have implicated a Mycoplasma as the causative agent in these infections3. Several different species of Mycoplasma have been cultured from the oral cavities of different pinnipeds including California sea lions (Zalophus californianus)2 and a Mycoplasma was thought to have complicated a viral pneumonia outbreak in harbor seals (Phoca vitulina)1. However, disease associated with Mycoplasma sp. has not been previously described in otariids.
From July 1999 to November 2001, Mycoplasma sp. was cultured from lesions found in 16 (12 male, 4 female) sea lions that had stranded along the central California coast and were brought to The Marine Mammal Center for rehabilitation. The animals ranged in age from yearling to adult and weighed between 19.5 and 174.5 kg. Eight of the animals were eventually released while the remaining eight either died or were euthanized during treatment. Of the eight animals that died, Mycoplasma sp. was thought to have contributed to the death of three animals where it was associated with severe pleuritis and necrotizing pneumonia in two animals and a septic polyarthritis in one animal. A summary of the lesions from which Mycoplasma sp. was cultured is presented in Table 1.
A moderate to severe leukocytosis characterized by a neutrophilia with a left shift was found in 12 out of 15 animals in which a complete blood count (CBC) was performed. Mycoplasma sp. was cultured from subdermal abscesses in 11 animals and from muscle abscesses in an additional two animals. The high prevalence of superficial abscesses in these animals suggests a transdermal route of introduction for the organism. Potential sources may include bites from other sea lions or it may be that Mycoplasma sp. is an opportunist found on the skin that may be introduced through a break in the epithelial barrier.
The organism was cultured on blood and chocolate agar and appeared as small, pinpoint colonies embedded into the agar approximately 3 to 6 days after swabs were plated. A pure culture of Mycoplasma sp. was obtained in 11 of the animals. Preliminary PCR and DNA sequencing results indicate that this is a novel species of Mycoplasma. An unidentified gram-negative rod was cultured with the Mycoplasma sp. in four samples. The significance of this organism is unknown.
Table 1. Summary of Mycoplasma sp. cultured from lesions in California sea lions (Zalophus californianus).
|
Sea lion identification
|
Lesions cultured
|
Organisms cultured
|
|
CSL 4296
|
Carpal joint
|
Pure culture Mycoplasma sp.
|
|
CSL 4698
|
Cervical and retropharyngeal subdermal abscesses
|
Pure culture Mycoplasma sp., but Pseudomonas aeruginosa, Proteus vulgaris, E. coli, Klebsiella sp. grown on postmortem culture of occipital condyles
|
|
CSL 4779
|
Subdermal hip abscess
|
Pure culture Mycoplasma sp.
|
|
CSL 4801
|
Lung and pleural fluid
|
Pure culture Mycoplasma sp.
|
|
CSL 4859
|
Pleural fluid and axillary muscle abscess
|
Pure culture Mycoplasma sp.
|
|
CSL 4945
|
Subdermal flipper and mandible abscess
|
Pure culture Mycoplasma sp.
|
|
CSL 4949
|
Subdermal neck abscess
|
Pure culture Mycoplasma sp.
|
|
CSL 4956
|
Subdermal neck abscess
|
Pure culture Mycoplasma sp.
|
|
CSL 4957
|
Subdermal flipper abscess and prescapular lymph node
|
Mycoplasma sp. and unidentified gram-negative rod
|
|
CSL 4998
|
Subdermal hip abscess
|
Mycoplasma sp. and unidentified gram-negative rod
|
|
CSL 5025
|
Subdermal hip abscess
|
Mycoplasma sp., Gemella sp., E. coli
|
|
CSL 5026
|
Axillary muscle abscess
|
Mycoplasma sp. and unidentified gram-negative rod
|
|
CSL 5027
|
Sublumbar lymph node
|
Pure culture Mycoplasma sp.
|
|
CSL 5059
|
Subdermal neck abscess
|
Pure culture Mycoplasma sp.
|
|
CSL 5070
|
Subdermal neck abscess
|
Mycoplasma sp. and unidentified gram-negative rod
|
|
CSL 5152
|
Subdermal hip abscess
|
Pure culture Mycoplasma sp.
|
Animals responded well to surgical lancing, flushing and insertion of drains to treat abscesses and to through-and-through sterile saline joint flushes to treat septic arthritis. Clinical improvement was noted following treatment with doxycycline and erythromycin.
Mycoplasma colonies may be easily missed on culture plates due to their small size and because it may take longer for colonies to grow than for some other bacteria. Antibiotics used to treat Mycoplasma infections may differ from antibiotics that are more routinely used to treat subdermal abscesses in other species. It is important, therefore, that clinicians are aware of their pathogenic potential in California sea lions.
References
1. Geraci JR, DJ St. Aubin, IK Barker, RG Webster, VS Hinshaw, WJ Bean, HL Ruhnke, JH Prescott, G Early, AS Baker, S Madoff, RT Schooley. 1982. Mass mortality of harbor seals: pneumonia associated with influenza A virus 215:1129-1131.
2. Measures L, L Parker, P McRaid, M Hammill, E Albaine. 2001. Oral mycoplasmal infections in pinnipeds-risk of "sealfinger" infection? Proceedings of the Fourteenth Biennial Conference on the Biology of Marine Mammals. Vancouver, Canada.
3. Stadtlander CTK-H, S Madoff. 1994. Characterization of cytopathogenicity of aquarium seal mycoplasmas and seal finger mycoplasmas by light and scanning electron microscopy. International Journal of Medical Microbiology, Virology, Parasitology, and Infectious Disease (Germany) 280:458-467.