Fish Tank Aerosols Transmitting Infections to Other Tanks or Humans, by Dr. Adrian Lawler

Fish Tank Aerosols Transmitting Infections to Other Tanks or Humans

Adrian Lawler, Ph.D.
(retired) Aquarium Supervisor (l984-l998) J. L. Scott Aquarium Biloxi, Ms 39530
Original to Aquarticles

Introduction
There are many viral, bacterial, and fungal diseases of humans (and other animals) that are infective through aerosols created by coughs, sneezes, spraying, wind, impact, explosions, etc. The present article authored by Lawler was prompted by questions from a hospital concerning the possibility of infecting their staff and patients via aerosols from a marine display fish tank.

The inquiry I received was as follows: "We are trying to determine if there is a health risk to humans in an environment where a fish tank is kept from the aerosolized particulate that comes from the aeration process. Can some one get sick by breathing the air where a salt water fish tank is maintained?"

Related research
An aerosol containing biological organisms such as viruses, bacteria, fungi, dinoflagellates, or other organisms can be called a bioaerosol. In the case of a fish tank, the fine bubbles going to the water surface from air lifts, air stones, filters, etc., put many tiny aerosol droplets into the air that may contain some of the small organisms present in the fish tank water.

Not much detailed work has been done on aerosols from fish tanks. We know that gill disease of koi (http://www.ornamentalfish.org/common/acrobat/fvs/fvsjournalissue3.pdf ), and various life stages of ICH (http://www.lsc.usgs.gov/fhb/workshops/26/A12.HTM ) can be transmitted to other tanks via aerosols. The latter site reported that Ichthyophthirius multifiliis (ICH) trophonts or tomites could be transported up to 3 feet via tank aerosols, and "that viable Aeromonas salmonicida can be spread via airborne route and be recovered from water downwind from an experimentally generated aerosol/droplet spray. It is possible that viable fish pathogens can be spread via the airborne route."

"Aerosol transmission of pathogens can occur. Consider placing barriers between tanks." (http://www.atlantech.ca/articles/Biosecurity.PDF )

In using wastewater for crop irrigation, it has been found that "The use of sprinklers leads to the formation of an aerosol (about 0.1 to 1% of the amount of water spread). As a result, pathogens may be transported as far as 750 m with the wind." (http://www2.gtz.de/ecosan/download/BMZ-environmental-handbook-2000.pdf )

Previous experiments have shown that viruses and bacteria are put into aerosols with toilet flushes. "In fact, significant quantities of microbes floated around the bathroom for at least two hours after each flush." (http://www.straightdope.com/classics/a990416.html )

In humans, the bacterium Legionella pneumophila is been found to be widespread throughout the world. "Infection is acquired by inhalation of water aerosol derived from heating or air-conditioning systems, showers and spa pools. It is more likely to infect elderly or immunosuppressed individuals and can cause a severe multi-organ disease in addition to pneumonia." (http://www.24dr.com/reference/library/infection/emerge.htm )

My edited answer, and discussion
Here is my revised and edited answer to the question (contact information deleted):

IF there are bacteria in the tank that can potentially infect humans, then there is the chance one could get human infection via aerosol transmission. I would consider this chance of human infection via aerosol to be slight, probably less than the order of one thousandth of one percent of those exposed. There would have to be several things to occur for infection to result from breathing or passing through the bioaerosol, or from coming into contact with the settled bioaerosol:

1. You would have to have a bacterium (or other organism) in the tank that could potentially infect humans, for example, Mycobacterium marinum (or another species of Mycobacterium, various species of Vibrio, Erysipelothrix rhusiopathiae, Streptococcus, etc).

2. Water flow to the tank, or tank aeration, would have to be vigorous enough to get bacteria (or other infective agents) into an aerosol state in the air.

3. The resulting bioaerosol would have to be airborne long enough (not settle out on items in the area) for someone to come into contact directly (either breathing the aerosol, or having it settle on clothes or skin) with the bioaerosol while in the air, OR………….

4. The resulting bioaerosol would have to settle on items in the area and remain viable for a period of time and the potential victim come into contact with the settled infective agent which settled on food, clothes, toothbrushes, drinking glasses, towels, etc.

5. The person passing through and/or breathing the bioaerosol would have to have a weakened immune system making them more susceptible to infection, and breaks in skin of nose/mouth to allow bacterial entry, OR have the bioaerosol land on skin or in eyes where bacteria could enter via skin breaks or by rubbing into eyes, etc., OR have bioaerosol settle on items (food, clothes, toothbrushes, drinking glasses, towels, etc.) that are subsequently used by the victim and enter via skin breaks or rubbing.

See my article on various fish-related diseases that can be transmitted to humans, at: http://www.aquarticles.com/articles/management/Lawler_Diseases%20Transmitted%20to%20Humans.html

IF the fish tank is properly maintained, sick fish are promptly removed, there is a UV sterilizer and/or ozone treatment on the tank, and a good cover on the tank, there should be no real problems to staff or patients, as there will be no viable bacteria in the aerosol.

IF there is Mycobacterium chelonae in the hospital water supply, running the water could put this bacterium into the air, and have it settle on various hospital items which could lead to human infection. Also see my articles at: http://www.aquarticles.com/articles/management/Lawler_Infection_Details.html http://www.aquarticles.com/articles/management/Lawler_Tank_Safety.html

One should also be aware of the possibility of problems from toxic algae in tanks. See my article, at: http://www.aquarticles.com/articles/management/Lawler_Toxic_Algae.html Also see: http://www.advancedaquarist.com/issues/april2003/feature1.htm for a discussion on toxic aerosols.

I ran many tanks for many years, and the only human bacterial problems we encountered were from people putting hands and arms into problem tanks (Lawler: bacterial infections = mostly fish TB). We were not aware of a bacterial problem from breathing tank aerosols during all this time (over 50 years), or infections resulting from contact with settled aerosols. We did have some effects from a toxic algae bloom making us dizzy, weak, etc., one time from breathing the toxic aerosol coming from the affected tank.

As mentioned above, one study found ICH transported up to 3 feet away from the tank by aerosol. ICH is many times heavier than bacteria, so I would expect bacteria to be transported further than 3 feet via tank aerosol. I can find no reference on the distance tank bacteria can be carried via aerosol, but it will depend on the vigor of the aeration, size of aerosol droplets, air movement in the room, etc.

I would expect from experience working with fish tanks, etc., that we could see bioaerosols consisting of viruses, bacteria, fungi, parasitic dinoflagellates (Amyloodinium, and others), ciliates (as ICH), free-living dinoflagellates (which can produce toxic aerosols), and various other small organisms, or toxins, arising from fish tanks.

"The effectiveness of UV sterilization on fish pathogens has been well documented, and increases dramatically with pre-filtration to remove solids (Bullock and Stuckey 1977, Liltved and Cripps 1999). UV lighting is currently used in many hospitals to control airborne pathogens, including M. tuberculosis. It is important, however, that the appropriate system is chosen for your facility's water flow rate, and that bulbs are cleaned and replaced at regular intervals to ensure effectiveness. Exposure intensities of over 45 mW/cm2 will control the more resistant aquatic Mycobacterium (Miyamoto et al. 2000)." (http://www.mdsg.umd.edu/Extension/finfish/FF9.html )

Toxic aerosols
One should also be aware of the possibility of problems from toxic algae in tanks. See my articles, at: http://www.aquarticles.com/articles/management/Lawler_Toxic_Algae.html http://www.aquarticles.com/articles/management/Lawler_Diseases%20Transmitted%20to%20Humans.html Also see: http://www.advancedaquarist.com/issues/april2003/feature1.htm for a discussion on toxic aerosols.

For handling toxins from toxic algae blooms, see my article at: http://www.aquarticles.com/articles/management/Lawler_Toxic_Algae.html

Toxic aerosols produced by red tide organisms and Pfiesteria piscicida can affect humans in various ways:
-- Pfiesteria exposure can lead to skin sores, memory loss, narcosis ("drugged" effect), reddening of eyes, severe headaches, blurred vision, nausea/vomiting, difficulty in breathing, kidney/liver dysfunction, severe cognitive impairment (can't remember name, address, etc), etc.
-- Relapses have happened 6 years after initial exposure.
-- Pfiesteria is now classed as a BIOHAZARD III, and can be researched only in specially-equipped labs.

Summary
If water flow or tank aeration is strong enough to produce watery aerosols, then various diseases and even small parasites (or other small tank occupants) can be transported via those aerosols to other tanks AND to people that breathe in the aerosols or come into contact with settled aerosols. Prevent viable biological agents from being in aerosols by using a UV light sterilizer, or ozone treatment on the tank. The resulting sterilized aerosols will not transmit disease, either to other tanks, or to humans.

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