Fish spine punctures and zoonotic infections are serious
This installment of Fish Safe addresses issues important to aquaculturists, commercial and recreational fishermen, fish processors, and even fish hobbyists (those who maintain fish in tanks at home): fish spine punctures and the resulting infections.
In addition, I am thinking about those of you who may retreat from the Northeast coast to a warmer clime for the winter months: are you going to the Gulf Coast or southern California? If you encounter spine punctures or wound contamination, there will likely be different fish and different bacteria involved than we have here in the Northeast.
You may want to consider keeping this information on hand to provide to a medical practitioner should you encounter a fish spine puncture, wound contamination, or other situation discussed here, as many physicians have not been trained to recognize, diagnose, or treat these types of occupational injuries.
Although these puncture injuries are fairly rare, they can quickly become serious and, yes, fatal. Therefore, obtaining the correct diagnosis – and treatment – from the get-go is very important.
These sorts of injuries can result in zoonotic infections: infections in humans that are caused by animals. Familiar, non-fishing, examples of zoonoses are malaria, rabies, and Lyme disease.
More specifically, we are talking about bacterial infections. The two basic types of bacterial zoonoses are categorized by route of exposure: 1.) ingestion, and 2.) dermal (skin) contact.
Salmonella poisoning from eating raw or undercooked meat or eggs is an example of the first category of zoonoses, while fish spine punctures fall into the second category.
This article is concerned mainly about the dermal contact zoonoses.
Potential encounters
Sea urchin spines come to mind first. Sea urchin divers, tenders, and the dock crew are all at risk. The divers bag their catch in open weave bags and pass them onto the tenders; these bags are unloaded at the dock. The opportunities for getting stuck with sea urchin spines are many. (Sea urchin bycatch is also a risk for scallopers.)
Atlantic coast fishermen going for finfish must watch their nets for spiny dogfish; Pacific coast fishermen must watch for a bycatch of ratfish and rockfish.
Aquaculturists can be infected by handling infected or diseased fish they encounter at a poorly managed, unclean fish farm.
All commercial and recreational fishermen are also at risk for exposure to the bones, scales, and slime of the fish they catch.
Finally, home-based aquariums can also be a source of these infections.
For more on this topic, visit <https://iacuc.wsu.edu/zoonoses-associated-with-fish/> from Washington State University.
A look at zoonoses
New analysis methods that involve genotyping have improved the ability of researchers to connect infections in fish with infections in humans. For example, researchers can compare the DNA from the swab of an infected fish with the DNA from a swab of human infection and determine if the same bacterium is involved.
But given that fish and humans are two different organisms, it stands to reason that not all bacteria that infect fish will cause an infection in humans – and some bacteria which do not infect fish will infect humans. With that caveat, let’s look at Table 1 (page 22).
Please be advised that this table only discusses a few of the many possible zoonoses. There are many, many zoonoses that do not co-occur in fish and humans.
Also, all exposures in this table – except those of Clostridium botulinum – are from dermal contact. (Botulism, the illness, is caused by ingestion of the bacterium, Clostridium botulinum.)
As shown in the table, most of the zoonoses associated with dermal contact result in cellulitis, a serious inflammation of the soft tissues. If the bacteria are introduced by the spines of a sea urchin or fish, the bacteria can be delivered into the deeper tissues, into the spaces between joints, and into spaces near tendons. Tenosynovitis – the inflammation of the protective sheath that covers tendons – can then occur. Since the role of tendons is to connect muscles to the bones they control, inflammation of this sheath can lead to decreased mobility.
This is not a good outcome for those who depend on their hands a lot, such as fishermen. Surgery is sometimes required to address tenosynovitis and more serious conditions can arise if this inflammation is not treated.
These bacterial zoonoses can lead to septicemia (blood poisoning caused by bacteria). Septicemia is the diagnosis when bacteria have moved from the original location (such as your leg or hand) to other parts of your body through the blood stream.
At first, signs of infection will appear at the original location: redness, swelling, warmth, pus, and pain. When the infection begins to move, streaks will lead towards the core of the body. The person may begin to have chills and/or a fever. If medical attention has not been sought up until this point, it must be sought now.
Table 1 only looks at zoonotic infections – those introduced by animals – but there are many other bacterial infections that can occur which have signs or symptoms the same (or similar to) those discussed above. All these infections can have complications, so all need attention. Moreover, anyone who is immunocompromised (as a result of diabetes or cancer, for example) has an even greater risk of a poor outcome after a zoonotic or other bacterial infection.
Helping the healthcare provider
Seeking help earlier rather than later is key. Here is a list of dos and don’ts.
Do:
1.) Tell the provider your occupation and give as exact an exposure history as you can: were you stuck by a fish bone; were you standing in muddy or contaminated water; etc.
2.) Provide an accurate medical history and include the presence of any underlying disease
such as diabetes, liver disease, immunosuppression, or MRSA infections.
3.) Keep track of time so the provider knows how long it took for your symptoms to appear as they do. (For example, swelling that has taken place rapidly is a grave concern.)
4.) Explain how you have cared for the wound to this point. Have you cleaned it? Soaked it in warm water? Removed any spines or protruding bone fragments? (Yes, you can do that – but see “Don’t” #2.)
5.) Ask for a tetanus booster if it has been more than 5 years since your last one.
6.) The provider should be made aware that a cartilaginous fish bone or spine may not show up on X-ray.
7.) Be as physically quiet as possible until you have received your diagnosis and treatment.
8.) Remember there are numerous antibiotics available to treat bacterial infections, but they work better before the bacteria have had time to reproduce.
Don’t:
1.) Apply a tourniquet. A tourniquet will reduce the amount of healing blood and oxygen that gets to the wound.
2.) Try to dig out spine fragments or put pressure on the wound to move the fragment to the surface.
Here are a few more notes that may be helpful:
The bacteria that live in the North Atlantic have a different temperature tolerance from those that live on the Gulf Coast or in southern California. Sometimes laboratories have missed the exact cause of the infection because they have cultured a swab from the infection at the wrong temperature. Most cultures are done at 37°C, which is 98.6°F – our human body temperature. However, if a given bacteria lives in the Gulf of Mexico, its optimum growth temperature may be closer to 30°C (86°F); or if from the North Atlantic, something closer to 18°C (65°F) may be optimum. Laboratories culture/grow bacteria because identification of the causative bacteria facilitates choosing the appropriate antibiotic.
If the laboratory cannot grow the bacteria because it has chosen a temperature that kills the bacteria, that gets us nowhere. Even as many providers and healthcare facilities are not used to seeing fish-related zoonoses or infections caused by marine bacteria (known as halophiles, as they love salt), their labs are similarly unfamiliar with culture media and protocols that will give them the answers they need.
Finally, injury to bones and joints, large abscesses, and systemic infections (which can happen with these zoonoses and other marine-related infections) signal the need for urgent evaluation and care. A surgeon may need to be a member of the treatment team.
Steps for prevention
The public health approach is prevention. What can fishermen do to prevent exposure to a zoonotic infection or other bacterial infection?
Two organizations in British Columbia – WorkSafeBC (an organization in Vancouver) and Fish Safe (yes, the same phrase as used in these CFN articles) – have provided an excellent brochure titled Pure Poison-Fish Spine Injuries. Enter “pure poison” in the search field at <www.worksafebc.com>.
Some of the following ideas come from WorkSafeBC:
Wear dry heavy-duty gloves, cleaned regularly of fish slime; steel-toed or other boots suitable for your fishery; rain suit; safety glasses; and hard hat. Figure out what will protect you best but don’t shy away from the best coverage you can get for hands and feet if you are at risk for fish spine punctures.
Cover any open wounds with water-proof bandages.
Work out safe retrieval and disposal techniques when harvesting or bycatching spiny fish.
Ann Backus, MS, is the director of outreach for the Harvard T.H. Chan School of Public Health’s Department of Environmental Health in Boston, MA. She may be reached by phone at (617) 432-3327 or by e-mail at <abackus@hsph.harvard.edu>.
