discus000
Mon May 15, 2006, 06:59 AM
Just When You Thought It Was Safe To Go Back In The (Aquarium) Water…
Dr. Nicholas R. Silvaggi
Freshwater-Aquarium-Fish.com
Introduction
Millions of aquarium hobbyists work in their tanks every day, without taking any safety precautions beyond rolling up their sleeves. While it is true that the vast majority of hobbyists will never have any unfortunate repercussions from working in their aquariums, it is still wise to at least know the potential dangers involved. I myself never even thought about the possibility of aquarium-born pathogens until a few years ago when I read about a case of an aquarist getting a nasty infection from his marine reef aquarium. I am not overly concerned even after researching the topic, but I do take some simple, common sense precautions now before I dive into my aquarium. The aim of this article is to educate aquarists about the potential dangers that an aquarium might bring into their homes. I am not out to sensationalize the issue or to scare people away from the hobby. I will present a brief review of some scientific literature describing aquarium-born pathogens (disease-causing agents) and offer some simple steps every aquarist can take to protect themselves.
Bacterial Infections
Bacterial infections account for the majority of aquarium-born illnesses. There are a surprising number of potential pathogens present in coastal marine environments. Problematic organisms include several species of the genus Vibrio, Erysipelothrix insidiosa, and Mycobacterium marinum.
Vibrio
Of the vibrio species the most famous is Vibrio cholerae, the causative agent of cholera. Although cholera is extremely rare in developed countries (only four cases in the U.S. in 1999; none fatal), there are hundreds of non-cholerae vibrio infections reported each year, almost 10% of which prove fatal. Most of the potentially pathogenic vibrio species are marine, with vibrio vulnificus being a notable exception. This organism caused an outbreak of wound infections in workers handling tilapia in Isreal. In the United States, three vibrio species are responsible for the large majority of reported infections, Vibrio parahaemolyticus, Vibrio vulnificus, and a non-toxigenic strain of Vibrio cholerae. The latter does not produce the toxic protein that causes the terrible gastrointestinal symptoms associated with cholera. These pathogens can cause gastroenteritis, septicemia (infection of the blood), or wound infections, depending on the species. The majority of vibrio infections in the U.S. are gastroenteritis caused by eating raw or undercooked fish or shellfish. (All of you oyster shuckers take note.) Vibrio infections from aquariums do occur, however, and these are normally wound infections. Vibrio wound infections cause pustules and lesions, as well as cellulitis, which looks like bruising or a yellowish discoloration under the skin. The lesions are normally not very painful. Luckily, vibrio species are susceptible to a number of antibiotics, including tetracycline and cephalosporins.
Erysipelothrix insidiosa
Figure 1. A typical case of Erysipeloid infection. The arrow indicates the small wound where the pathoge entered the body.
Erysipelothrix insidiosa is found in association with both wild and domestic mammals, birds, fish, mollusks, and crustaceans world wide. It causes acute, localized skin infections. These almost always occur on the hands and fingers. In places with active fisheries such infections are commonly called "shrimp pickers' disease", "crab poisoning", or "fish poisoning." The rather mild-looking red lesions belie the searing pain that typically accompanies erysipoloid infections. Figure 1 shows a typical example of an erysipeloid infection. The white arrow highlights the small wound where the bacteria entered the man's body. Fortunately, these infections normally resolve themselves in about three or four weeks. Very rarely, Erysipelothrix can cause widespread infections. In these cases penicillin G and ampicillin are usually effective.
Mycobacterium marinum
Figure 2. An example of infection by Mycobacterium marinum. Note the gnarled, granular appearance of the lesion.
Of the bacterial pathogens discussed here, M. marinum is by far the most problematic for aquarists. It can be found with unsettling frequency in both fresh and saltwater aquariums and poorly chlorinated swimming pools. Mycobacterial infections appear as gnarled, granular lesions on the skin (see Figure 2). These granulomas appear two to six weeks after an abrasion or other injury sustained in the water (i.e. from handling live rock) or an existing wound is exposed to water. It is typical for M. marinum infections to occur on fingers, hands, elbows, and knees because these areas are prone to cuts and abrasions. While these infections really are rare, even among those whole frequently work in their aquariums, there is at least one case of a child exhibiting multiple lesions spread over the entire body after being bathed in a tub that had recently been used to clean an aquarium.
Treatment is with antibiotics, clarithromycin, doxycycline, and rifampin/ethambutol. The course of the treatment is long, requiring at least three months. Deep infections may require some of the lesion to be removed surgically. Hot water or heat lamps may speed recovery, since the organism does not grow well at high temperatures. It should be noted that many general practitioners, especially those in inland regions, are not accustomed to seeing M. marinum infections and may fail to diagnose it properly.
Salmonella
Everyone who washes their cutting board after preparing chicken knows that birds can carry Salmonella, and that Salmonella can be a very nasty human pathogen. Perhaps some reptile owners know that lizards and snakes can also carry the bacteria. But how many people, especially aquarists, would guess that Salmonella can come from aquarium water? As in birds, Salmonella is not ubiquitous in aquariums, but there is a real possibility of its occurrence in your aquarium. Salmonella species have been isolated from aquarium water in many parts of the world, and has even been proven to colonize the common goldfish. This is a concern because Salmonella from these sources can be pathogenic depending on how many cells are ingested and the health of the host's immune system. Seepersadingh et al. (2003) studied the prevalence of Salmonella in birds, reptiles, and aquaria. Out of 485 aquaria tested, they isolated Salmonella from two of them (0.4%). Both isolates came from pet shop aquariums, and not home aquariums, but they tested 481 pet shops and only four home aquariums. As I said, the risk is small, but it is there. What is worse is that of the Salmonella strains isolated in the study, half were shown to be resistant to at least one common antibiotic. One of the isolates from fish tanks was resistant to cephalothin, a common cephalosporin antibiotic.
Cercarial Dermatitis
Though bacteria cause the large majority of aquarium-acquired infections, parasites, like trematode flat worms, can also cause problems for aquarists. Fölster-Holst et al. (2001) report on a case of cercarial dermatitis contracted by a German biology teacher when cleaning the class aquarium. The aquarium contained aquatic snails collected from a local lake during the summer, and this was the major cause of the infection. Cercariae are the larval form of the trematode Trichobilharzia ocellata, a relative of the human parasite Schistosoma sp. The life cycle of this parasite begins and ends with waterfowl. Birds, especially ducks, release millions of eggs into the water in their feces. The eggs hatch and the miracidiae gather in the digestive glands of snail hosts, in this case Lymnaea stagnalis. In bright light and high temperature, thousands of cercariae burst forth from the snail in search of a new avian host. This is where humans can run into trouble. The cercariae use non-specific signals to locate their next host, including cholesterol. This means that cercariae are able to mistakenly invade human skin. The infestation is a dead end as far as the parasite is concerned, because the cercariae can not reach the blood to complete the life cycle. The cercariae die within 12 hours of entering human skin. The dermatitis is actually caused by the host's immune response to the digestive enzymes the cercariae use to enter the skin.
Figure 3.A picture of the patient's forearm showing the pustules caused by the burrowing cercariae (white arrows). Reproduced from Folster-Holst et al. (2001).
Our biology teacher made the mistake of collecting snails from a shallow, stagnant area of a local lake. The conditions in the aquarium caused the snails to release their load of cercariae, which mistook the teacher's arm for a viable host. The result is the itchy, poison ivy-like rash pictured in Figure 3. Pustules mark the sites where cercariae entered the skin (white arrows).
Fortunately, since humans are a terminal (non-productive) host for T. ocellata, treatment is relatively easy. The parasites will die within a few hours. The skin eruptions are treated with cortisone and antihistamines to combat the itch. Cercarial dermatitis can be prevented by avoiding exposure to cercariae. This means avoiding the shallow, stagnant waters of lakes during the warm summer months.
Prevention
The old adage is true. Prevention really is the best medicine. Fortunately a very few simple and inexpensive measures can help limit your risk of contracting an aquarium-acquired infection. Obviously, all of these measures are aimed at reducing your exposure to these organisms. The first suggestion is the easiest to implement. Never put your skin in contact with aquarium water. If you have any cuts or abrasions on your hands or arms, then you need to be extra careful. Buy some sturdy rubber gloves, such as the ones sold at most grocery stores for washing dishes, etc. If you want to be fancy, many vendors sell arm-length rubber gloves that will allow you to stick your entire arm in the tank safely. Never handle live rock without gloves of some sort. The rocks are very sharp and abrasive, increasing the risk of a mycobacterial infection. If you are in the habit of starting your siphon with your mouth (as millions do, including me) you might think about getting a cheap suction device to do it for you. Salmonella is an orally acquired pathogen, meaning that one must swallow the germs to be infected. For this reason, it's best not to risk drinking the aquarium water. Even if you don't swallow it, if there are enough salmonella cells in the water they can still cause a problem. Finally, never add pet store water to your tank. This is something that you should never do anyway, since you don't know how well-maintained their tanks are or what else might be in that water. Your own health sould provide just another reason to practice careful stocking techniques. These few simple precautions will protect any aquarist from the majority of the illnesses discussed here. As I have said throughout this article, aquarium-acquired infections are extremely rare. However, since any aquarium can potentially carry human pathogens, and the preventive steps are easy and inexpensive, why not spend a few dollars to protect yourself?
Dr. Nicholas R. Silvaggi
Freshwater-Aquarium-Fish.com
Introduction
Millions of aquarium hobbyists work in their tanks every day, without taking any safety precautions beyond rolling up their sleeves. While it is true that the vast majority of hobbyists will never have any unfortunate repercussions from working in their aquariums, it is still wise to at least know the potential dangers involved. I myself never even thought about the possibility of aquarium-born pathogens until a few years ago when I read about a case of an aquarist getting a nasty infection from his marine reef aquarium. I am not overly concerned even after researching the topic, but I do take some simple, common sense precautions now before I dive into my aquarium. The aim of this article is to educate aquarists about the potential dangers that an aquarium might bring into their homes. I am not out to sensationalize the issue or to scare people away from the hobby. I will present a brief review of some scientific literature describing aquarium-born pathogens (disease-causing agents) and offer some simple steps every aquarist can take to protect themselves.
Bacterial Infections
Bacterial infections account for the majority of aquarium-born illnesses. There are a surprising number of potential pathogens present in coastal marine environments. Problematic organisms include several species of the genus Vibrio, Erysipelothrix insidiosa, and Mycobacterium marinum.
Vibrio
Of the vibrio species the most famous is Vibrio cholerae, the causative agent of cholera. Although cholera is extremely rare in developed countries (only four cases in the U.S. in 1999; none fatal), there are hundreds of non-cholerae vibrio infections reported each year, almost 10% of which prove fatal. Most of the potentially pathogenic vibrio species are marine, with vibrio vulnificus being a notable exception. This organism caused an outbreak of wound infections in workers handling tilapia in Isreal. In the United States, three vibrio species are responsible for the large majority of reported infections, Vibrio parahaemolyticus, Vibrio vulnificus, and a non-toxigenic strain of Vibrio cholerae. The latter does not produce the toxic protein that causes the terrible gastrointestinal symptoms associated with cholera. These pathogens can cause gastroenteritis, septicemia (infection of the blood), or wound infections, depending on the species. The majority of vibrio infections in the U.S. are gastroenteritis caused by eating raw or undercooked fish or shellfish. (All of you oyster shuckers take note.) Vibrio infections from aquariums do occur, however, and these are normally wound infections. Vibrio wound infections cause pustules and lesions, as well as cellulitis, which looks like bruising or a yellowish discoloration under the skin. The lesions are normally not very painful. Luckily, vibrio species are susceptible to a number of antibiotics, including tetracycline and cephalosporins.
Erysipelothrix insidiosa
Figure 1. A typical case of Erysipeloid infection. The arrow indicates the small wound where the pathoge entered the body.
Erysipelothrix insidiosa is found in association with both wild and domestic mammals, birds, fish, mollusks, and crustaceans world wide. It causes acute, localized skin infections. These almost always occur on the hands and fingers. In places with active fisheries such infections are commonly called "shrimp pickers' disease", "crab poisoning", or "fish poisoning." The rather mild-looking red lesions belie the searing pain that typically accompanies erysipoloid infections. Figure 1 shows a typical example of an erysipeloid infection. The white arrow highlights the small wound where the bacteria entered the man's body. Fortunately, these infections normally resolve themselves in about three or four weeks. Very rarely, Erysipelothrix can cause widespread infections. In these cases penicillin G and ampicillin are usually effective.
Mycobacterium marinum
Figure 2. An example of infection by Mycobacterium marinum. Note the gnarled, granular appearance of the lesion.
Of the bacterial pathogens discussed here, M. marinum is by far the most problematic for aquarists. It can be found with unsettling frequency in both fresh and saltwater aquariums and poorly chlorinated swimming pools. Mycobacterial infections appear as gnarled, granular lesions on the skin (see Figure 2). These granulomas appear two to six weeks after an abrasion or other injury sustained in the water (i.e. from handling live rock) or an existing wound is exposed to water. It is typical for M. marinum infections to occur on fingers, hands, elbows, and knees because these areas are prone to cuts and abrasions. While these infections really are rare, even among those whole frequently work in their aquariums, there is at least one case of a child exhibiting multiple lesions spread over the entire body after being bathed in a tub that had recently been used to clean an aquarium.
Treatment is with antibiotics, clarithromycin, doxycycline, and rifampin/ethambutol. The course of the treatment is long, requiring at least three months. Deep infections may require some of the lesion to be removed surgically. Hot water or heat lamps may speed recovery, since the organism does not grow well at high temperatures. It should be noted that many general practitioners, especially those in inland regions, are not accustomed to seeing M. marinum infections and may fail to diagnose it properly.
Salmonella
Everyone who washes their cutting board after preparing chicken knows that birds can carry Salmonella, and that Salmonella can be a very nasty human pathogen. Perhaps some reptile owners know that lizards and snakes can also carry the bacteria. But how many people, especially aquarists, would guess that Salmonella can come from aquarium water? As in birds, Salmonella is not ubiquitous in aquariums, but there is a real possibility of its occurrence in your aquarium. Salmonella species have been isolated from aquarium water in many parts of the world, and has even been proven to colonize the common goldfish. This is a concern because Salmonella from these sources can be pathogenic depending on how many cells are ingested and the health of the host's immune system. Seepersadingh et al. (2003) studied the prevalence of Salmonella in birds, reptiles, and aquaria. Out of 485 aquaria tested, they isolated Salmonella from two of them (0.4%). Both isolates came from pet shop aquariums, and not home aquariums, but they tested 481 pet shops and only four home aquariums. As I said, the risk is small, but it is there. What is worse is that of the Salmonella strains isolated in the study, half were shown to be resistant to at least one common antibiotic. One of the isolates from fish tanks was resistant to cephalothin, a common cephalosporin antibiotic.
Cercarial Dermatitis
Though bacteria cause the large majority of aquarium-acquired infections, parasites, like trematode flat worms, can also cause problems for aquarists. Fölster-Holst et al. (2001) report on a case of cercarial dermatitis contracted by a German biology teacher when cleaning the class aquarium. The aquarium contained aquatic snails collected from a local lake during the summer, and this was the major cause of the infection. Cercariae are the larval form of the trematode Trichobilharzia ocellata, a relative of the human parasite Schistosoma sp. The life cycle of this parasite begins and ends with waterfowl. Birds, especially ducks, release millions of eggs into the water in their feces. The eggs hatch and the miracidiae gather in the digestive glands of snail hosts, in this case Lymnaea stagnalis. In bright light and high temperature, thousands of cercariae burst forth from the snail in search of a new avian host. This is where humans can run into trouble. The cercariae use non-specific signals to locate their next host, including cholesterol. This means that cercariae are able to mistakenly invade human skin. The infestation is a dead end as far as the parasite is concerned, because the cercariae can not reach the blood to complete the life cycle. The cercariae die within 12 hours of entering human skin. The dermatitis is actually caused by the host's immune response to the digestive enzymes the cercariae use to enter the skin.
Figure 3.A picture of the patient's forearm showing the pustules caused by the burrowing cercariae (white arrows). Reproduced from Folster-Holst et al. (2001).
Our biology teacher made the mistake of collecting snails from a shallow, stagnant area of a local lake. The conditions in the aquarium caused the snails to release their load of cercariae, which mistook the teacher's arm for a viable host. The result is the itchy, poison ivy-like rash pictured in Figure 3. Pustules mark the sites where cercariae entered the skin (white arrows).
Fortunately, since humans are a terminal (non-productive) host for T. ocellata, treatment is relatively easy. The parasites will die within a few hours. The skin eruptions are treated with cortisone and antihistamines to combat the itch. Cercarial dermatitis can be prevented by avoiding exposure to cercariae. This means avoiding the shallow, stagnant waters of lakes during the warm summer months.
Prevention
The old adage is true. Prevention really is the best medicine. Fortunately a very few simple and inexpensive measures can help limit your risk of contracting an aquarium-acquired infection. Obviously, all of these measures are aimed at reducing your exposure to these organisms. The first suggestion is the easiest to implement. Never put your skin in contact with aquarium water. If you have any cuts or abrasions on your hands or arms, then you need to be extra careful. Buy some sturdy rubber gloves, such as the ones sold at most grocery stores for washing dishes, etc. If you want to be fancy, many vendors sell arm-length rubber gloves that will allow you to stick your entire arm in the tank safely. Never handle live rock without gloves of some sort. The rocks are very sharp and abrasive, increasing the risk of a mycobacterial infection. If you are in the habit of starting your siphon with your mouth (as millions do, including me) you might think about getting a cheap suction device to do it for you. Salmonella is an orally acquired pathogen, meaning that one must swallow the germs to be infected. For this reason, it's best not to risk drinking the aquarium water. Even if you don't swallow it, if there are enough salmonella cells in the water they can still cause a problem. Finally, never add pet store water to your tank. This is something that you should never do anyway, since you don't know how well-maintained their tanks are or what else might be in that water. Your own health sould provide just another reason to practice careful stocking techniques. These few simple precautions will protect any aquarist from the majority of the illnesses discussed here. As I have said throughout this article, aquarium-acquired infections are extremely rare. However, since any aquarium can potentially carry human pathogens, and the preventive steps are easy and inexpensive, why not spend a few dollars to protect yourself?