What Facts Should I Know about Fish-Handler's Disease?
Can fish give humans diseases?
Fish-handler's disease is a nonspecific term that is in the medical and lay literature that describes a disease or syndrome of humans that may occur after handling fish or, in some instances, other aquatic organisms. There are a number of other similar terms that essentially describe the same disease. They are as follows:
- Fish-handler's disease
- Fish handler's nodules
- Fish tank granuloma
- Swimming pool granuloma
- Fish tuberculosis
- Picine tuberculosis
- "Erysipeloid" infection or lesions
What is fish-handler's disease in humans?
The disease has so many names because so many different outbreaks have been associated with occupations (fishermen or lobstermen), hobbies (tropical fish tanks, pet shop workers), or water sports (boating, swimming pool use). Researchers also discovered that at least two different genera of bacteria (Mycobacterium and Erysipelothrix) were the main causative infective agents of the disease. These findings added to the proliferation of names. Although some of the symptoms (mainly lesions on the extremities) caused by the organisms are similar, other symptoms, diagnosis, and treatment are somewhat different. This article is designed to discuss these two major causes of fish-handler's disease.
What Causes Fish-Handler's Disease?
Fish-handler's disease occurs when cuts or scrapes in the skin become infected with the bacteria Erysipelothrix rhusiopathiae and other species. This is an erysipeloid infection, which means it is caused by an infection that resembles erysipelas but is caused by a different organism than that which causes erysipelas. Handling and preparing fish and shellfish and many other similar activities can create small cuts and scrapes in the skin, where bacteria may enter. Developing fish-handler's disease requires deliberate contact with fish, particularly lobster and other shellfish. Fish-handler's disease occurs worldwide wherever fish and shellfish are handled.
Fish-handler's disease also occurs when cuts or scrapes in the skin become infected with Mycobacterium ssp., mainly the species marinum and fortuitum. Handling tropical fish, coral, cleaning aquariums, swimming pools, fishing, lobster catching, and many other similar activities can introduce these bacteria into cuts and scrapes. This disease is worldwide and can be associated with many organisms that inhabit saltwater, freshwater, or brackish water. One of the newest outbreaks occurred in the Chesapeake Bay with about 76% of striped bass found to have an infection with Mycobacterium.
Fish or other aquatic organisms with visible surface lesions should be not be handled with bare hands (wear gloves to help prevent infections) and not eaten. However, cooked aquatic organisms have not been reported to cause fish-handler's disease.
What Are the Symptoms and Signs of Fish-Handler's Disease?
Symptoms for fish-handler's disease caused by Erysipelothrix rhusiopathiae and other species are as follows:
- The disease generally develops two to seven days after injury to the skin and subsequent bacterial infection.
- A sharply defined, the red-purple circular area appears and surrounds the puncture; the center usually fades, and occasionally a vesicle (blister) may appear.
- The area of injury increases in diameter by about ½ inch per day.
- Joint stiffness, lymph node swelling, and pain burning, itching, and swelling at the injection site may accompany the infection.
- Rarely, the disease may progress to produce sepsis (infection of the bloodstream) and endocarditis (infection of the heart valves).
Symptoms for fish-handler's disease caused by Mycobacterium species are as follows:
- The disease generally develops about two to four weeks after exposure, although up to nine months postexposure has been reported.
- Skin lesions are often multiple and linear but can be single.
- Lesions can appear as nodules, abscesses, or ulcers, with skin color changes, and develop slowly (months).
- Joint pain, lymph node swelling, and tendonitis may develop.
- Rarely, the disease may progress to sepsis (infection of the bloodstream).
When to Seek Medical Care for Fish Handler's Disease
- If a person develops any skin lesions (either painful or not) after handling fish or other aquatic organisms, or after swimming, boating, or cleaning fish tanks or aquariums, they should seek medical care; those with a suppressed immune system should immediately contact their doctor.
- Consult a doctor about treatment with available medications so that the appropriate antibiotic is given to treat the specific bacterial cause of the disease.
How Is Fish-Handler's Disease Diagnosed?
Diagnosis of the cause of an individual's fish-handler's disease is done by culturing the bacteria from the lesions or by PCR tests (tests that identify the genetic material of bacteria or other organisms) specific for the bacterial type involved.
What Is the Treatment for Fish-Handler's Disease?
Treatment for fish-handler's disease caused by Erysipelothrix rhusiopathiae and other species is as follows:
- All wounds require immediate cleansing with fresh tap water. Gently scrub the wound with soap and water to remove any foreign material.
- Oral antibiotics (mainly penicillins) are often prescribed to treat skin infections. Prior to starting an antibiotic, be sure to tell the doctor about any drug allergies. Continue antibiotics for the entire time recommended by your doctor, even after all signs of infection have cleared.
- Pain may be relieved with one to two tablets of acetaminophen (Tylenol) every four hours or one to two tablets of ibuprofen (Advil, Motrin) every six to eight hours.
- If sepsis develops, endocarditis commonly follows; IV penicillins, cephalosporins, and clindamycin (Cleocin) have been effective in treating these severe infections. However, Erysipelothrix rhusiopathiae and other species are resistant to vancomycin, a drug often used in the treatment of endocarditis.
Treatment for fish-handler's disease caused by Mycobacterium spp. requires antibiotics. Antibiotics such as rifampin (Rifadin), streptomycin, sulfamethoxazole and trimethoprim (Bactrim), tetracyclines, and others have been successfully used to treat the condition; depending on the patient response and severity of infection, length of treatment may vary from about two weeks to 18 months. Corticosteroids are generally avoided as they may inhibit treatment and recovery. Severe infections may require IV antibiotics, plus the surgical removal of some infected tissues in tendons and joints.
Antibiotics for Fish Handler’s Disease
Antibiotics to treat Fish-handler's disease are not always needed because some patients spontaneously clear the infection. However, if the infection with Erysipelothrix rhusiopathiae does not resolve then the antibiotics of choice are either penicillin or a cephalosporin such as ceftriaxone.
Patients who are allergic to penicillin may be treated with ciprofloxacin alone or with erythromycin in combination with rifampin (Rifadin). Rarely, a patient may develop endocarditis caused by this organism; IV forms of the above antibiotics are recommended for treatment. Vancomycin, a commonly used IV drug used to treat endocarditis will not be useful because Erysipelothrix rhusiopathiae is resistant to vancomycin. Clindamycin (Cleocin) has also been used effectively by IV.
For Mycobacterium spp. that cause Fish-handler's disease, patients may be treated with rifampin, streptomycin, sulfamethoxazole, and trimethoprim (Bactrim), tetracyclines, isoniazid, pyrazinamide, and/or ethambutol. Organisms isolated from the patient should be tested for drug susceptibility as some of this spp. are resistant to specific antibiotics. Mycobacterium spp. are difficult to treat; two antibiotics (or more) may need to be used to treat a patient.
Some patients may need long-term antibiotics (about 18 months) and possibly surgical excision in addition to antibiotics to halt infection. Infrequently, a patient with Fish-handler's disease may require IV antibiotics.