Anaphylaxis
Anaphylaxis, an allergic reaction to the animal's venom, is a medical emergency. Anaphylaxis is a systemic immune response to a compound. It is independent of the compound's innate toxicity. Because it is dependent upon the immune system, an anaphylactic response requires prior exposure to the compound. Following this initial exposure, there will be no physically evident symptoms. One could consider this exposure as "priming" the immune system. Later contact, either the next time or several times down the road, will produce a systemic, life-threatening response in susceptible individuals within seconds to minutes of re-exposure. Again, this response is variable from person to person, and generally independent of the level of exposure. This reaction is characterized by vascular collapse and shock, with or without respir
atory distress. Possible symptoms include:
Upper airway swelling -- hoarseness and a "lump in the throat" feeling.
Lower airway obstruction -- chest tightness.
Wheezing, and shortness of breath.
Cutaneus involvement -- intensely itchy, red, raised hives with pale centers and wandering borders, that can be local or spread over the entire body.
Gastrointestinal symptoms -- nausea, vomiting, diarrhea, and cramping stomach pains.
Vascular collapse -- blood pressure drop, rapid heart rate, and shock.
Anaphylaxis requires prompt medical treatment with epinephrine and other support measures. Anyone who has experienced a severe allergic reaction should avoid exposure to the precipitating compound. If this compound is a toxin produced by a reef inhabitant, the animal should be removed from the aquarium. At a minimum, epinephrine should be readily available for immediate use in case the individual is exposed to the compound again. Because anaphylaxis is immune regulated, each response will likely be more severe than any previous exposure.
Local Allergies
In addition to the severe anaphylactic reaction, minor local allergic responses can also be initiated. This contact dermatitis can be very similar to the hypersensitivity reaction of poison ivy. Often, it will be difficult to differentiate an allergic response from the response of a toxin or foreign body. Sponges of the genus Tedania (fire sponges) can produce this type of allergic reaction. Moreover, spicules from the sponge are irritating, though they can be removed by gently applying adhesive tape to the dried area and peeling the imbedded spicules off attached to the tape.
Inorganic compounds such as the salt used in tank water can be irritating and produce a type of dermatitis. The rash, or chronic eczema, is often located near the antecubital fossa (the part that is hidden when the elbow bends). This patch is usually dry, red, and itches. The lesion is often produced by rubbing the arm against dried salt deposits along the top of the tank during routine maintenance. The dried deposits disturb the epithelial integrity and produce a local irritation. This type of hobby-related injury will heal in several days once exposure is stopped. Hydrocortisone creams may alleviate some of the symptoms. This type of irritation can be prevented by wiping salt deposits off the top of the tank before introducing the extremity into water and exposure can be limited by wearing arm-length gloves. Moreover, carefully washing the arm with freshwater afterwards will remove any salts before they can dry or sufficiently irritate the skin.
Infection
Finally, the most important non-acute complication of marine trauma is infection. Tank inflicted or otherwise unrelated injuries or wounds can become infected with halophilic (salt-loving) bacteria from the aquarium, or with other bacteria from the environment. In a study in which animal wounds were inoculated with Hong Kong beach water, 318 bacterial strains were isolated. The predominant marine/estuarine species were of the genera Vibrio, Pseudomonas, and Aeromonas. The infection rate was highly correlated with fecal coliform counts, implying that aquarium water, which is relatively pure when compared to seawater from many recreational beaches, does not harbor virulent bacteria in the same densities. In another experiment, oral cultures from two captive moray eels at the Chicago Shedd Aquarium were taken. Isolated bacteria "included Vibrio fluviolis, V. damsela, V. vulnificus, Micrococcus species, and coagulase-negative Staphylococcus." In addition, Pseudomonas puterfaciens was also isolated from cultures of the tank water. Other species of Vibrio have been isolated from oral cultures of Leopard, Maco, and Great White sharks.
Therefore animal bites can directly inoculate numerous virulent bacterial species into the wound. In addition, many of the bacterial species found free in tank water and in the slime coating of fish cause infections in both aquatic creatures and humans. This includes Erysipelothrix rhusiopathiae and related species which can produce a red patch with vesicles and smaller papules. The borders are well demarcated and slightly raised. The bacteria enter through minor skin trauma and initially produce an itchy and painful purplish area following an incubation period of less than four days. The infection expands slowly, mostly towards the body proper. Untreated, the infection will resolve within several weeks. Rare cases of disseminated disease and endocarditis, an infection of the heart, have been reported. Though this disease has yet to be described as an aquarium-associated problem, it is relatively common in the fishing industry and is most likely transferred through dead fish. Moreover, human wounds are exposed to Staphylococcus and Streptococcus species that are ubiquitous on the skin. Finally, it has been reported that fish handlers and aquarists are at a higher risk for common warts caused by various types of human papilloma virus, though this has yet to be substantiated. In short, the likelihood for some type of infection at some point is high among hobbyists.
Vibrio sp.
Species from the Vibrio genus are the most common marine bacteria, accounting for over 31% of all colonies culturable from water samples. V. vulnificus is probably the most common Vibrio species isolated from human wounds. It is gram negative, highly motile, strongly oxidase-positive, and ferments glucose (other species of Vibrio ferment lactose). Virulence is associated with the presence of an acidic polysaccharide capsule that protects the bacteria from host defenses. Virulent strains also produce destructive enzymes including proteases, lipases, DNAses, chondroitin sulfatase, mucinase, and hyaluronidase; with all of these enzymes being capable of dissolving different tissue components. This bacterium rarely causes infections in healthy humans, yet it can cause devastating infections in individuals with certain illnesses or those who are immunologically compromised. V. vulnificus is found at peak levels in water temperatures of 21-23oC, the temperature that some reef aquariums may be maintained at. Furthermore, the presence of V. vulnificus is unrelated to fecal coliform counts in two studies, and it grows best in clean water. Filter feeding organisms such as oysters can concentrate this bacteria in very high amounts. Hence, eating contaminated raw oysters can produce severe sepsis, a systemic infection of the blood, with a high mortality rate. But, most aquarists do not eat the fruits of their labor, so a more likely form of disease is via wound infection. This can rapidly progress to secondary sepsis and is associated with a 7-24% mortality rate, even with medical treatment.
V. vulnificus cutaneus infections are restrained to the extremities, even if they are secondary to a primary sepsis from ingestion of the bacteria. This is most likely a result of its preference for a temperature lower than that of central core areas of the body. The initial infection presents early with redness, swelling, and intense pain. It quickly overwhelms the local immune response, as evidenced by the plethora of bacteria on biopsy at the dermal/epidermal junction, but the general lack of inflammatory cells. The redness changes to a bronze discoloration and bacteria move into the lymphatics and surrounding tissue. The bacteria spreads rapidly, destroying tissue with their toxins and producing large areas of necrosis. The process can mimic gas gangrene, with vesicles and bullae (blisters) often present. The bacteria destroy skin, blood vessels, connective tissue, and muscle. Invasion of blood vessels can lead to secondary sepsis. This infection requires aggressive treatment with antibiotics and surgical debridement. Even with this therapy, it is often rapidly fatal.
Several factors place certain populations at a heightened risk for V. vulnificus infections. First, its virulence is associated with host iron availability. The bacteria produce proteins that can complex free iron and allow for growth. Normally in the body, a protein called transferrin binds iron tightly and greatly limits the availability of the free form. Chronic diseases that increase blood iron levels produce a more favorable environment in which the bacteria can grow. Some of these diseases include: hemolytic anemia, where red blood cells are lysed and iron from the hemoglobin is released; hemochromatosis, a genetic disease in which excess iron is stored in the body; and liver diseases such as hepatitis and alcohol-related liver damage, which destroy the liver and decrease the amount of transferrin synthesised. Other proteins, such as complement (the body's immediate defense against invasion), are not produced in adequate amounts in severe liver disease. Furthermore, ethanol increases stomach acid secretion, which increases iron absorption from the small intestine. This leads to a net increase in the amount of total iron present in the body. Second, disorders that compromise the immune system will give V. vulnificus an advantage and allow for infection. These diseases include HIV, cancer, diabetes (also a problem because peripheral nerve damage can allow a wound or infection to go unnoticed for days), and genetic immune disorders.
Mycobacterium sp.
A second "hobby-associated infection" is caused by the bacterium Mycobacterium marinum. Unlike Vibrio species, M. marinum infections are very insidious. For example, in a Thailand study of 44 reported cases over 20 years, the average known disease duration prior to presentation was 2.5 years (range 1 month to 10 years). In another study of 31 patients presenting at 33 Kaiser Permanente medical centers in Northern California over 7 years, the average known disease duration prior to presentation was 2 months (range 2 days to 3.5 years). In the Thailand study, 12 patients (66.7%) had hobbies or occupations associated with fish and water exposure. The second study reported 16 patients (52%) who had potential exposure through fish tanks. Hence, this disease is intimately connected to water contact and the aquarium hobby. This has lead to several names, including "swimming pool granuloma" and "fish tank granuloma."
M. marinum is a slow growing acid-fast bacterium that is closely related to M. tuberculosis, the causative agent of tuberculosis. Thus, a percentage of M. marinum infected individuals will also have a cross-reacting positive tuberculin skin test. Unlike most other mycobacteria, M. marinum grows best at 32oC. Hence, even in extremely rare disseminated infections, lesions are predominantly on the cooler extremities. Normally, the bacteria enter through sites of minor trauma, with the site of infection often on the fingers, hands, or arms. Since the onset is insidious, the incubation period is not known and has been estimated to be 2-4 weeks. Most cases evolve into a single granuloma. Granulomas are lesions composed of special immune cells that form a wall around infected tissue. This is done because the immune system has trouble killing the bacteria. It tries to surround and contain the bacteria, so that they cannot spread beyond the immediate area. Also, the immune cells in a granuloma are activated and produce strong bactericidal agents, facilitating the containment and eradication process. Most frequently, the infected site is red with some swelling. Granulomas will appear as elevated papules or lumps. Sometimes the granulomas crust or ulcerate. Bacteria can spread along the lymphatic drainage system, producing multiple granulomas and lesions. This most often occurs 4-8 weeks following the formation of the primary lesion (range 5 days to 1.5 years). Unlike Vibrio and other more aggressive infections, M. marinum infections are painless.
Superficial infections respond to antibiotic therapy, and involution of the lesions usually begins within 2 weeks of the initiation of therapy. Treatment is often several months long, and the infected area will heal with a scar. Multiple drug therapy is recommended since the bacteria can develop resistance during the long treatment period. Deep infections can occur following more severe trauma, including bite wounds. This type of infection often requires a combination of surgery and antibiotics. Disseminated M. marinum infections have been reported rarely in immuno-compromised individuals. This infection will present with numerous small papules covering the head and extremities but sparing the trunk. Except for the distribution, this disease will resemble chicken pox. Bone and joint involvement will also occur in these extremely rare disseminated cases.
Infection Prevention
Several steps can be taken to limit or prevent infection and disease caused by bacteria from an aquarium. First, try to avoid allowing traumatized areas from coming in contact with aquarium water. If possible, use the other arm or wear a long latex glove. All cuts and scrapes should be immediately washed with soap following contact with aquarium water. Use topical antibiotics such as neosporin. Do not let bowls or containers that come in contact with aquarium water/inhabitants be used for eating or drinking purposes. Vibrio septicemia is caused when the bacteria enter the circulation from the gastrointestinal system. Theoretically, contamination of food could cause infection. Do not dump aquarium water in sinks or bathtubs. A case of disseminated M. marinum has been reported in an infant that occurred from bathing in the same bathtub used for tank water disposal. Additionally, use antibiotics in your aquariums with caution. Exposure to antibiotics will lead to selection of resistant strains of bacteria, especially when these medications are not used properly (which is usually the case). For example, most aquarium freshwater bacteria are resistant to tetracycline because of its misuse by aquarists. Because these bacteria can cause infection and severe illness in humans, it is dangerous to expose them to substandard antibiotic therapy and risk selecting resistant strains. Finally, look for warning signs -- pain, redness, tenderness, a wound that is getting worse instead of healing, and red streaks spreading centrally from the wound towards the body. These are indications of infection, with the last two indicating the definite need for medical intervention. In short, simple steps can largely prevent aquarium-related infections and diseases.
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