The short version
- Seal finger is a hand infection caught from seals, usually caused by Mycoplasma bacteria; fishers, hunters, sealers and marine biologists get it[1].
- It shows up 3 to 4 days after a bite or a cut that touched seal tissue, and can take anywhere from 1 to 21 days[1].
- The usual first-choice antibiotics often fail: cases have resisted cephalosporins, amoxicillin-clavulanate, azithromycin and erythromycin, while tetracyclines such as doxycycline work[1][2].
- Late or wrong treatment costs fingers: one study found 49% of patients left with a stiff joint[1].
What seal finger is, and why doctors miss it
The infection was first written up in 1907, and Norwegian sealers called it spekkfinger, blubber finger[1]. Most doctors have never seen a case, so wounds go untreated or get the wrong antibiotic[1].
| Question | Answer |
|---|---|
| Cause | Mycoplasma from the seal’s mouth or tissue; Mycoplasma phocimorsus was named as a new species in 2023 from 6 Scandinavian patients[2] |
| How it gets in | A bite, or broken skin that touches seal tissue[1] |
| First signs | Sudden severe swelling, redness and pain, with a finger that will not bend; pus is unusual, clear fluid is common[1] |
| What works | Tetracycline-class antibiotics, often for 4 to 6 weeks; the new species is also sensitive to moxifloxacin[1][2] |
| Easily confused with | Erysipeloid, which is easier to culture and redder[1]; see fish handler’s disease |
Who gets seal finger: the case record
| Source | Who | What happened |
|---|---|---|
| 2025 literature review[1] | Sealing fleets, 1950 reports | 10% of a Norwegian sealing crew and 2.5% of a Newfoundland crew infected |
| Alaska, 2016[3] | Alaska Native hunter | Fever, a swollen finger and infected hips after harvesting seals; the first known spread case |
| Alaska, 2025[4] | Hunter skinning a bear | Bone infection in the finger after a delayed diagnosis and treatments that failed |
| Canada, 2009[5] | Patient referred to hand surgery | Misdiagnosed at the first visit, then recovered fully on tetracycline |
| United States, 1981[6] | Two young women bitten by seals | One cured with tetracycline; the other needed the finger joint fused |
| Marion Island, Southern Ocean[9] | Seal biologists, 22 bites | 5 had symptoms like seal finger; 4 settled within 4 days without antibiotics |
| San Francisco Bay, 2011 to 2014[8] | 11 open-water swimmers bitten | One infection failed on amoxicillin-clavulanate and healed on doxycycline |
For a fishing crew the exposure is a seal or sea lion bite, or seal tissue handled with cut hands. A deep bite is not needed; broken skin is enough[1].
How many seals carry the bacteria
| Wild seals sampled in eastern Canada[7] | Carrying M. phocicerebrale in the mouth |
|---|---|
| Gray seal | 78% (31 of 40) |
| Hooded seal | 70% (32 of 46) |
| Harbor seal | 44% (11 of 25) |
| Harp seal | 22% (8 of 37) |
The same study also found mycoplasmas in California sea lions, elephant seals and Pacific harbor seals at a rehabilitation center[7]. Treat every seal bite as contaminated[1].
What to do on board after seal contact
- Wash the wound with soap and water and treat any seal bite as contaminated[1].
- Write it down: the date, the animal, and whether the skin was broken. The medical log is the place.
- Watch the hand for 3 weeks. Most cases start on day 3 or 4, some as late as day 21[1].
- At the first swelling, get radio medical advice and say “seal contact” in the first sentence; that is what steers the doctor away from the antibiotics that fail[1].
- Give antibiotics only as the physician directs. In Canada, many ship captains carry tetracycline and give it at the first sign of seal finger[1].
When seal finger is an emergency
Fever, swelling that spreads up the hand, or pain in other joints after seal contact need a physician the same day: the 2016 Alaska case spread from a finger to both hips[3]. Treatment that is late or wrong can destroy the joint[6]. On a vessel, a spreading seal finger infection calls for a medevac decision.
Prevention for crews who work near seals
Wear gloves when handling seals or seal tissue; most seal bites land on the hands and arms, which points to bare-handed work[1]. Touching or petting seals and sea lions is prohibited by the Marine Mammal Protection Act[8]. Related: catfish sting, degloving injury and marine animal injury statistics. For Alaska boats, see Alaska fishing vessel medical compliance.
Seal finger is rare but predictable for crews who work near seals, so the response belongs in the vessel’s medical plan and in the chest. Discovery Health MD writes both: maritime medical consulting for the marine animal injury protocol, and ship medical chest management for the antibiotics and dressings it calls for. Ask a physician to review your fleet’s wound and bite plan.
Common questions
What is seal finger?
A painful hand infection caught from seals, usually caused by Mycoplasma bacteria[1].
How long after a seal bite does seal finger start?
Usually 3 to 4 days, with a range of 1 to 21 days[1].
What antibiotic treats seal finger?
Tetracyclines such as doxycycline; one new species is also sensitive to moxifloxacin but resistant to azithromycin and erythromycin[1][2].
Can you get seal finger without a bite?
Yes. Broken skin that touches seal tissue is enough, which is how sealers and hunters get it[1].
Is seal finger dangerous?
It can be: in one study, 49% of patients were left with a stiff joint, and one Alaska case spread to the hips[1][3].
Do sea lions cause seal finger?
Mycoplasmas were found in California sea lions, and a pinniped bite infection in a swimmer healed only on doxycycline[7][8].
How common is seal finger?
There is no current prevalence data; older reports found 10% of a Norwegian sealing crew infected[1].
