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Marine Mammal Bites Information for Healthcare Providers

animal bites

Marine Mammal Bites Information for Healthcare Providers

Millions of residents and visitors to California enjoy the many beaches each year. A rare but concerning occurrence among beachgoers are bites from marine mammals. Seals, sea lions, and sea otters normally coexist with and tolerate humans without incident; but some animals can become more assertive and aggressive due to infectious or toxicologic conditions. Humans who encounter these ill animals risk being bitten. Because bites from these large carnivores can be severe, the majority of bite victims will seek medical attention.

Recommendations for general wound care

The wound from the bite or scratch should be cleaned within the first few hours by washing with soap and running freshwater for 20 minutes or more. Assess whether the patient has completed this step before presentation.
Liberal irrigation with normal saline or Lactated Ringers solution further decreases the concentration of bacteria, particularly in deep, extensive, or puncture wounds.
Debride wounds contaminated with necrotic tissue, dirt, or other foreign materials.

Minor wounds can be managed by the victim at home but those that are more severe, deep, or more susceptible to infection should be closely monitored for signs of infection.
Symptoms of “seal finger" infection may appear from one day up to three weeks following the bite.
More Information: CDPH Investigation, Management, and Prevention of Animal Bites in California, 3rd edition, 2014 (PDF)

“Seal finger” is a nonspecific term for swelling, discharge, and cellulitis that appears typically around joints following a bite, scratch, or other break in the skin associated with pinnipeds. Mycoplasma is considered the most common cause.

In addition to extensive tissue damage, it is important for health care providers to recognize the potential infectious consequences of marine mammal bites and manage bite victims appropriately.

Rabies

Although all mammals are susceptible to rabies, the virus has not been isolated from marine mammals in California. Therefore, bites from seals, sea lions, and sea otters to humans pose a negligible risk for rabies transmission. While the high consequences of untreated rabies exposure tend toward liberality in post-exposure prophylaxis (PEP) decisions, healthcare providers should strive to avoid recommending PEP to persons who have negligible or no risk of rabies. Providers who have questions about the risk of rabies and decisions on PEP following an animal bite should consult with Communicable Disease staff at their local public health department.

Tetanus

Clostridium tetani has not been isolated from marine mammals but has been detected in marine sediment, making tetanus a concern for any penetrating wounds exposed to ocean silt or water. In the event of a bite or scratch wound, tetanus vaccination is recommended if it has been more than 5 years since last tetanus immunization.

Antimicrobial therapy recommendations

Signs of infection present:

Antimicrobial treatment of clinically infected bite wounds should ideally be based on culture and sensitivity results. There are limited, published studies on the microbiology of marine mammal bite wounds, and a variety of aerobic and anaerobic bacteria present in their oral cavity and sea water can lead to contamination.
If results from culture and sensitivity are not available to guide antimicrobial selection, consider antimicrobials that do not target the cell wall (e.g. tetracyclines) to cover Mycoplasma spp.

Mycoplasma phocacerebrale and Bisgaardia hudsonensis (member of Pasteurellaceae family) are notable bacteria isolated from seal and sea lion bites and have previously been considered when choosing prophylactic antimicrobial treatment.
Mycoplasma spp. can cause severe, painful swelling and erythema without other signs of infection. Bisgaardia hudsonensis infections may also exhibit these clinical signs in addition to yellow exudate from the lesion.

Broader coverage that includes both aerobic and anaerobic organisms may be indicated based on the characteristics of the wound and the potential for contamination.

No signs of infection present:

The evidence to support antibiotic prophylaxis of bite wounds without signs of infection is not clear. Prophylactic antimicrobials may be considered for injuries at elevated risk for infection:

Moderate to severe wounds less than 8 hours old if edema or crushing of tissues is present
Puncture wounds with possible bone or joint penetration
Hand wounds
Wounds adjacent to a prosthetic joint or in the genital area
Wounds in immunocompromised patients

Resources

Case Reports

Nuckton et al. (2015) California Sea Lion (Zalophus californianus) and Harbor Seal (Phoca vitulina richardii) Bites and Contact Abrasions in Open-Water Swimmers: A Series of 11 Cases – Wilderness & Environmental Medicine

Case reports for 11 open-water swimmers that were attacked by seals or sea lions. Information collected includes injury photos/descriptions, treatment success or failure, features of the encounter, animal behavior, location, and date/time.

White et al. (2009) Seal Finger: A Case Report and Review of the Literature – Plastic Surgery

Detailed description of successful treatment in a 46-year-old man with seal finger. Summarizes the disease epidemiology and pathophysiology, historical discovery of seal finger infectious etiology, and past traditional treatments.

Cheng et al. (2016) River otter bite in a 52-year-old woman: managing animal bites – Canadian Medical Association Journal

Case report of successful treatment in 52-year-old woman with a river otter bite after adjustment in antibiotic therapy. No organisms were obtained on bacterial culture from the wounds. Reviews guidelines for otter bites.