Sea otter stranding

Sea otter stranding, Monterey Bay, CA

A Zoonotic Disease Found in Sea Otters – Coccidioides immitis
Melissa A. Miller also contributed to this piece

When responding to sick/injured Southern sea otters or recovering carcasses, responders should be aware of the potential health hazards associated with wildlife contact. This is one reason the public is encouraged to call the proper authorities rather than handle live or dead sea otters themselves. The organizations that are authorized to handle and treat these species have training that helps to protect both stranded otters and rescue personnel. Some of these organizations include the California Department of Fish and Game, United States Geological Survey, U.S. Fish and Wildlife Service, Monterey Bay Aquarium, and The Marine Mammal Center. These organizations train staff members to know what to do if bitten or if they become sick, and workers have health coverage and workers compensation insurance.

The obvious dangers of working with wild animals like sea otters are bites and scratches. Sea otters have powerful jaws that can cause deep wounds, bone fractures or infection. Some species of bacteria that are commonly isolated from sea otters can cause severe wound infections when implanted in bite wounds or scratches. There is also a risk of catching a zoonotic disease (a disease that is transferable from animals to humans) from handling live or dead sea otters. An example of a zoonotic disease that most people are familiar with is rabies. Rabies has never been reported from sea otters, but they are certainly susceptible to this virus, and rabies cases have been reported from river otters.

In addition to infection through skin wounds, humans can become infected with zoonotic organisms by inhaling aerosolized droplets containing the organisms, through splashes in their eyes or by accidentally consuming infectious organisms after touching contaminated materials, such as blood, urine or fecal matter. Some important zoonotic organisms that are known to infect sea otters include the single-celled parasite Toxoplasma gondii, the marine Brucella bacteria and the fungus Coccidioides immitis. C. immitis infection causes the disease “Valley Fever” in humans. Human infection with this fungus can be serious, so we are extremely careful when handling these cases. Luckily we only see a small number of infected sea otters every year. We call C. immitis-infected otters “Cocci” cases – As soon as we recognize them we take extra precautions.

Zoonotic Disease - Coccidioides immitis

Two round, thick-walled fungal stages (spherules) of Coccidioides immitis in a sea otter eye (center). Photo credit: Dr. Melissa Miller (CDFG)

Based on the experience of working in a necropsy (postmortem examination) setting for many years, we’ll describe the protective measures we take during postmortem examinations of stranded sea otters. Basic personnel protective equipment (PPE) worn during all routine necropsies consist of a scrub top and pants, tall rubber necropsy boots, gloves, eye protection, and a waterproof apron. When necropsying an otter that might have a zoonotic disease, we also use a face mask, sometimes even one with a HEPA filter. We are also trained to use a full-face respirator, or use a safety hood for additional protection, when needed. We complete postmortem examinations on potential Cocci cases quickly and then freeze the carcass to reduce our risk of aerosol exposure to this fungus. When the tissue form of C. immitis is exposed to the air for a prolonged period (1-2 days) it can form a stage that can be more easily inhaled, triggering infection. We also collect any fluids and tissues for incineration to prevent further transmission of the fungus.  When cleaning, water pressure is lowered to prevent fungal splashing or aerosolization. All surfaces are disinfected and the necropsy instruments are scrubbed and autoclaved (steam sterilized) as a further precaution. Scrub tops, pants and aprons are washed immediately. This helps prevent cross-contamination and helps to protect staff health.

Numerous factors help the necropsy staff determine if a given sea otter may be a high risk for zoonotic disease. For example, because most ”Cocci” cases are collected along the shoreline of San Luis Obispo County, we are extra-careful when handling any otters that are found sick or dead in this region. When performing the necropsy, potential abnormalities that can suggest the presence of a zoonotic organism include swollen lymph nodes, an enlarged and/or spotted spleen or liver, pneumonia, pleuritis (inflammation in the chest cavity), lung masses or the presence of abscesses, inflamed joints or reproductive abnormalities. If these are present, it is best to conduct further tests. We can quickly examine tissue or fluid smears on a microscope to scan for the fungus (cytology), try to grow the organisms in the laboratory (microbiology), or examine wax-embedded tissue sections (histology) to help determine if an otter died from C. immitis or some other potentially zoonotic disease.

CDFG biologists recover approximately 2-4 C. immitis-infected sea otters each year. The route by which sea otters are exposed to Coccidioides is not known, but is believed to be an example of land-to-sea biological pollution as the organism originates from alkaline soils. It appears that this fungus-contaminated soil either blows out to sea or flows downstream to the ocean, thus affecting sea life. Depending on the state of the infection, the spores of “Cocci” can also be aerosolized and inhaled by humans. Freezing the infected otter or its tissues will not kill the fungus, even in -80°C. In addition, bones, fur or other samples collected from infected animals as souvenirs can transmit this fungus to humans. According to the Center of Disease Control and Prevention-Department of Health and Human Services, C. immitis infection can pose a severe threat to human health. Because of this concern, we incinerate the carcasses of all sea otters with known or suspected C. immitis infection.

In summary, the potential for human exposure to zoonotic organisms like Coccidioides immitis during wildlife conservation efforts cannot be taken lightly. When officials ask the public not to touch, harass or feed wildlife, they are trying to protect the health and well-being of both animals and humans. Our training, knowledge, and experience help minimize our risk of exposure to zoonotic pathogens. So please enjoy the sea otters from the safe viewing distance of 50 yards (150 feet) on land and 100 yards (300 feet) on water per the Marine Mammal Protection Act of 1972. And please leave handling of sick or dead marine wildlife to trained personnel. Thank you!


Southern Sea Otter Stranding Contact Numbers for the Public

Sick/Injured Sea Otters:

In Santa Cruz or Monterey Counties: Monterey Bay Aquarium (MBA), 831-648-4840

Outside the above areas: The Marine Mammal Center, 415-289-7325


Dead Sea Otters:

Santa Cruz County and North: California Department of Fish and Game (CDFG) 831-212-7010

Monterey County: CDFG, 831-212-7010 or MBA, 831-648-4840

San Luis Obispo and South: CDFG, 805-772-1135


NOAA Fisheries – Office of Protected Resources

Viewing Guidelines:


CDC’s National Select Agent Registry