Saltcorner
By Bob Goemans
By Bob Goemans
Note to Readers: uShaka Marine Park, which opened in April 2004, is a massive undertaking in Durban, South Africa. It consists of five separate theme areas, i.e., Sea World; Dolphin World; Wet & Wild World; Beach World; and, Treasure World, encompassing over 5,000,000 gallons of water. The following article formed part of a letter written to senior management denoting the protocol that its author wished to establish. I want to thank David Vaughan, its Senior Quarantine Aquarist for the following article.
Quarantine is probably the least understood area regarding its function or place in a public aquarium, hence differences in opinion regarding a wide range of related and integrated subjects. In this document, I hope to create a better understanding of the concept of quarantine in aquaria, its function, my aims and my goals for the new development, uShaka Island, as well as problem areas and solutions.
What is Quarantine?
The dictionary defines "quarantine" as a time of compulsory isolation or detention to prevent the spread of contagious disease. The name itself meaning "forty days."
Quarantine has four distinct and equally important functions:
1) The prevention of the spread of contagious diseases from a contaminated source to a non-contaminated source, which can be explained as "active prophylaxis."
2) The active treatment of known diseases and infections caused by disease-causing organisms, using Chemotherapeutant chemicals and detergent substances.
3) The most overlooked and misunderstood function of Integrated Pest Management, or I.P.M, is where established disease-causing organisms are controlled indefinitely as a result of overwhelming and permanent factors outside the control of both numbers 1 and 2 by targeting specific vulnerable life-cycle stages of parasites in conjunction with revised husbandry practice.
4) Sterilisation: the elimination of all life in a system to eradicate a disease problem.
My concept of a Quarantine for a public aquarium incorporates all four of the above, as each situation presents a unique requirement. It must also be understood that Quarantine is not just the area in which the quarantining process is implemented, but an entire concept incorporating an entire organisation or aquarium, large or small.
If we look at the first step, we can immediately recognise its main function, which is prevention. The question has been raised: "Why do we want to prevent diseases if the fish seem healthy and disease free?" The question itself is a valid one. In general we trust ourselves in what we witness, using sight as possibly the most influential tool for making judgements and decisions. Fishes caught in the wild look in prime condition when captured, but there is an intricate net, or web of complete harmony, which is easily disturbed or broken with our intervention when those specimens are collected.
It is well known that parasites of fishes in the wild, representing many forms and specialities form a relationship with a host organism, where the host is generally used for the gain of the parasite, without any host benefit. The parasites are generally not responsible for disease outbreaks in the wild population and prefer to remain as small self-sustaining populations from which the host is used to complete only a small and generally insignificant stage of their life-cycle. The host, if healthy can carry these small populations of parasites and help with their general longevity and natural survival. A general parasite and host relationship exists harmoniously.
Several factors determine the success, failure and even the population explosion of parasites on these hosts. The first one is the environment. We all know that the environment in which we live determines our ultimate reactions to it, as even we as humans have what we call our "comfort zones." Different parasites and groups of parasites require different environmental conditions for optimal survival and reproduction. This is a key factor in determining their control, not only from a quarantine perspective but in nature as a whole. Marine fish parasite numbers are usually controlled through nature's manipulation of their environment through temperature and salinity fluctuations to general time required for the completion of life-cycles, host specificity/availability, competition/predation and the area and topographical influence or physical area in which the host lives and inhabits. These influences can be represented as a formulated model:
Parasite numbers x 1 = % successful reinfection rate
(Basically, parasite numbers divided by the effects of their environment (Which varies, e.g., temperature + salinity + topography + host specificity/availability + other environmental conditions such as competition/predation) multiplied by itself and divided by time (which would therefore be relative to the exposure of these conditions) is equal to the percentage success rate of any reinfection.)
Disease is usually only associated with these parasites if the direct environmental influences are manipulated or changes in such a way as to favour the parasite. These influences include high temperatures which shorten the time necessary for the completion of parasitic life-cycles within their optimum temperature range; increased host number availability or implementation of integrated species or related species specificity; decline in predation; and/or among other things, stable favourable salinity.
Indirect environmental factors also play an extremely important role because it is generally recognised that several positive influential factors favouring parasite success are conversely related to those associated with the positive factors favouring the host fish. We therefore can state generally that unfavourable environmental conditions influencing the health and well-being of the host may favour the possibility of pathogenesis caused by the otherwise latent associate parasite:
Minus - Parasite Numbers - Favourable Conditions
Plus - Parasite Numbers - Unfavourable Conditions
(Parasite numbers may increase if the host is experiencing unfavourable conditions or they may decrease if experiencing favourable conditions)
Indirect environmental conditions such as stress caused during capture and removal of the host from its natural environment, along with placing them in relatively small confines in large stocking densities, will over time (which is again an important factor) directly effect the parasite-host relationship. And these factors lower the hosts' immune system, as well as creating closed artificial environments, which favour parasite production. The host not only has to deal with more frequently occurring outbreaks of higher numbers of parasites, but its immune system or natural resistance, which is lowered as a stress-response, is not in place to counter the problem. Parasites multiply quickly, accelerated by their new "favourable" environment, added to the unfavourable environmental conditions experienced by the host, and disease occurs.
The immunosuppressive stress response is probably the most important associated problem with disease outbreaks and may be caused by numerous and uncontrollable factors in any public aquarium. The first step of a successful quarantining process is designed to understand these delicate relationships and to target the obvious problematic factor, the disease-causing organism. One could also argue that the environmental factors could also be targeted, so as to produce favourable host environmental conditions, thus maintaining the natural host and disease-causing organism equilibrium. In theory this would work only if the stress-related immunosuppression of the host could be eliminated and if natural conditions for both host and disease-causing organism could be reproduced, which is extremely difficult and almost impossible to achieve in a public aquarium.
The most important element of successful implementation of the first quarantine step is understanding how the disease-causing organisms work and what their relationships are with the host. Certain groups of these organisms or parasites will be effectively destroyed by certain chemicals, while others will not. A good understanding of the general knowledge surrounding the pharmacological requirements for successful prophylactic treatments is imperative. The concept surrounding the first quarantine step is a simple one. Destroy the latent parasite load on the host fish before the manifestation of disease.
To destroy the latent parasite load on the fish successfully, certain steps need to be correctly implemented. A host fish can carry more than one type of parasite, including different groups, which need different treatments in different time-frames to be successfully removed. To do this we need to understand and try to incorporate broad-spectrum treatments designed to target actual groups or phyla of parasites. The family Protozoa, including the common Cryptocaryon, Amyloodinium etc, can be controlled and ultimately destroyed using detergent treatment regiments. Detergent treatments include those chemicals that are designed to eliminate infection from the host, but with a small safety margin. The safety margin exists between the levels at which the detergent is effective against the parasite before becoming damaging to the host tissue, and the level at which the detergent can cause tissue damage and death of the host itself. Unfortunately these margins can sometimes be relatively small and managing the detergent levels in a quarantine system can be difficult and comes with experience. Copper citrate, the form of copper that we use as one of our detergent regiments, is one such treatment. If used at the correct therapeutic level, the parasite that is being targeted can be eliminated over time without damaging the host. These levels of copper are recognised as being successful only from 0.15 ppm (parts per million) and above, with a maximum acceptable level of 0.30 ppm for the host fishes. Therefore, with a safety margin of only 0.15 ppm, copper citrate is probably also potentially one of the most risky detergent treatments to perform. The choice of using copper citrate lies in its ability to be successful as a broad-spectrum external-protozoacide, but again in relative terms. One must understand that there are two ways in which a detergent regiment can target a specific problem. Firstly, by understanding the possibilities, the treatment can be specifically designed to be used as an in-water medication, where the host and parasite come into contact with the treatment in the immediate environment, or as a direct application to the host. Copper is one used as an environmental treatment and thus is effective only against external protozoan and some crustacean infections.
Other factors include time, as possibly the most important one during a detergent treatment regiment. Generally, the detergent, such as copper will only be effective against a specific vulnerable or susceptible part of the parasite's entire life-cycle. The difficult thing is that we cannot determine at what point a parasites life-cycle is actively integrated in an established environment, and to be correct, the different stages of the life-cycle will overlap. With the first step of the quarantine process we ultimately remove the host fish from this reinfective environment and therefore are dealing with usually only a section or two sections of the parasite's life cycle. The application of preventative or active prophylaxis needs to take place as soon as the host is placed into a new controlled environment, represented by the quarantine facility in the aquarium. If the host is not treated and disease allowed to manifest, the second quarantine stage is automatically implemented, which can also be used as a tool in targeting exact known infections.
To be successful, the detergent treatment must be effective constantly for the period of time in which it takes the vulnerable stage throughout the entire parasites' life cycles, to be destroyed. This incorporates time, levels of therapeutant (detergent) and controlled environmental conditions. If any one of these parameters is altered, for example, if the time-frame is decreased or if the levels of therapeutant are lowered below the point at which they are effective, even for a short period, a window is created in which the parasite can complete its life-cycle. Even if expressed as a small percentage, it ultimately leads to a reinfection cycle.
Many institutions use only one detergent therapeutant as their main prophylaxis or preventative measure. This can be seen as a large portion of part of the first quarantine step, however it cannot be seen as a sound general measure. To be as successful as possible we need to again visit the possibilities of infection. If protozoan parasites are removed from the picture expressed as a percentage of external parasites, then surely there are those different groups and families which will either be less-susceptible or immune to this one or few treatments. This is true for the Helminth group of parasites incorporating many external parasitic worms, with mainly very specific modes of infection and host specificity, added to different reproduction and survival strategies.
Again, we would like to use a broad-spectrum detergent treatment incorporated into the first quarantine step to be successful. Copper is ineffective against the parasitic helminths, but the use of formalin at specific levels is extremely effective, as are other "chemotherapuetants" such as the anthelminthic group of drugs.
Timing and therapeutic levels of this detergent (Formalin) are again important. Many external helminth parasites effect different parts of the body such as the gills, skin, fins, eyes etc. Many of them have direct parasite-host reproductive strategies and some produce eggs which enter the surrounding environment forming an open life-cycle similar to the concept used by some of the protozoan parasites. The successful destruction of the helminth group is determined by not only the correct levels of therapeutant used, but how it is used. Helminths are easier to treat than protozoan parasites, because both the adult parasitic reproductive stage can be eliminated as well as the reinfective juvenile parasitic or oncomiracidial stage. In the case of egg-producing helminth parasites, the eggs are resistant to treatment. We can therefore state that in understanding the actual time in which it takes the eggs to be produced, incubated and hatch, an initial once-off treatment will eliminate further egg-production and reinfection until such time that the eggs hatch. To be as effective as possible, the time it takes the last theoretical eggs to be produced and their known hatching rate, with treatment time overlap, will determine the last re-application of therapeutant. And if the time-frame is know in which the eggs take to hatch, re-application of therapeutants repeated for possible oncomiracidial reinfective stages which emerge, before they are able to become sexually mature, will be effective in eradicating the problem. Again "Time" is the key factor.
Formalin as my detergent therapeutant chemical of choice is widely effective against possibly the largest incorporated groups of external helminth parasites. But again needs to be carefully managed between levels which are effective in destroying the parasites and those which are destructive to host tissue. Generally I prefer to use a broad-spectrum dose of 1ml (38% vol.) formalin to 20L of water. Lower levels are generally effective against the general and more commonly experienced helminth groups of Monogeneans. But for some reason, both the Capsaloidea group of Monogeneans, of which none present in South Africa have been properly identified, and the Turbellarians (Platyhelminths), forming the group of flatworm parasites causing "black spot" disease, are not effected at lower levels sufficient enough to eliminate reinfection.
Formalin is a harsh treatment and actively removes oxygen and ammonia from the water. Oxygen is removed at 1mg for every 12mg formalin depending on water temperature, and recently, after some experimenting, I determined that 1ml 38% vol. formalin to 100L, removes 0.16 ppm of ammonia. Both pose a problem in treatment therapeutant levels. If oxygen is replaced by formalin, the host's environment becomes more stressful. It is therefore important to include oxygen as an additional part of relatively high formalin treatments as above. If the environment being treated possesses levels of ammonia, these levels will directly influence the effectiveness of the therapeutant, as formalin and ammonia react conversely on each other (cancel each other out), thus lowering the levels of formalin needed to be effective against the parasite. This is the main reason why it is so important to remove any uneaten food from treatment tanks and to keep them as clean as possible with regular flushing and re-administering of treatment.
My design of the first quarantine step as above incorporates copper citrate followed by the use of formalin to try and create as tight and effective as possible true prophylaxis before manifestation of disease occurs. The old saying of "prevention is better than cure" is certainly true.
The remaining part of the first quarantine step incorporates the internal treatment of parasites. Host fishes can carry many different types of internal parasites, which generally only cause problems if the host's immune system is compromised, as for the same stress related immunosuppression explained above.
Some internal protozoan parasites are extremely difficult to eradicate, and oral medications need to be administered to be successful. Thankfully not many moralities have been positively linked to internal protozoan parasites, however, this group of internal parasites may well cause unexplained and mysterious deaths with seemingly no answers. As yet there are no incorporated prophylactic oral regiments for the control of internal protozoan parasites because application of timely treatments is extremely difficult. And so far has only been mildly successful as an oral application though anesthesia and intubation using known host body weights and disease-causing organisms identified in histology from related mass-mortalities. (Dr. A. Mouton and D. Vaughan)
Amyloodinium is also one of those common dinoflagellate protozoan parasites which not only effect the host externally as mentioned earlier, but also effects the lining of the gut, causing severe anorexia in a short space of time. Internally there is nothing we can do, but as the parasite leaves the host to continue its life-cycle, the use of a timely external general prophylaxis becomes apparent.
Our main target in internal prophylaxis is the group of intestinal helminths, usually with complex life-cycles, which cause more direct host-related problems than reinfection risk concerns and need not be incorporated immediately into the general quarantine regiments. But can be treated on a repeated cycle with fishes present on display or exhibit as a de-worming schedule every six months, given orally in their food.
Problems associated with the first quarantine step:
1) General prophylaxis does not cover 100% of possible latent disease-causing organisms present on or in the host.
The second step is by far a more aggressive and direct step in the quarantine concept. This step incorporates detergent therapeutant chemicals and chemotherapeutant chemicals to directly target known parasites already in the stage of pathogenesis.
Chemotherapeutants are chemicals designed to specifically target the disease-causing organism and have little or no effect if used correctly, on the host. Chemotherapy includes the use of antibiotics for bacterial infections, antifungal treatments, some antiprotozoan treatments and the anthelminthic drugs such as Praziquantel, Fenbendazole, Mebendazole etc.
Specific disease-causing organisms manifest themselves as large population explosions, causing the ultimate demise of the host if not treated. This can make specific treatment success depend heavily on several factors, including actual progressive development of the parasite in the environment and on the host, related to the condition of the host and amount of damage caused by the infection. Other influences also play a part, such as additional secondary infections and opportunism by otherwise saprophytic organisms and other parasitic organisms as the health of the host deteriorates and its immuno response is further compromised. The success therefore of treating a specific outbreak of a disease relies heavily on its early detection and positive identification and implementation of the correct specific treatment. Strangely enough another main factor in determining a treatment's success or failure is the host fish itself, as some fishes can cope with certain infections better than others.
Treatment of a specific disease, is therefore an active and aggressive one and not preventative. This second step is implemented in the possibility of certain disease-causing organisms that managed to evade the first step, which is quite possible, as this relies and reflects on the correct management of the initial step or the lack of. It is important to note that to assume a 100% success rate for the initial quarantine step is short sighted, and that all three steps actually form different dynamics of the whole concept.
The second quarantine step should be restricted as much as possible to a controlled quarantine environment, hence the addition of an isolated hospital section incorporated into the quarantine area at uShaka Island. These controlled conditions allow for the correct treatments to be used in conjunction with small treatment volumes without the risk of exhibit or display failure, and the associated public response to diseased fishes which is a negative one. The use of the quarantine facility as a controlled environment also eliminates the risk of cross-contamination from an infected area to another uninfected area, eliminating epidemics.
Specific disease-causing organisms are targeted to the exact time frame needed in which to eradicate them, as for the first quarantine step, but instead of two or three selected general broad-spectrum treatments, specific treatments and their associated regiments are used. Copper is used as a general broad-spectrum external protozoacide in the first quarantine step, and as a specific external protozoacide in the second step, in the case of Cryptocaryon and Amyloodinium. Formalin can be used at different dosages depending on the specific identification of the helminth parasite in the case of fluke outbreaks and their specific susceptibility to it.
The treatment of disease in a display poses a number of challenges and problems. The viewing public is generally aware of obvious disease manifestations and the use of certain treatments, which discolour the water, reflects a negative picture. If disease outbreaks occur on display, if identified early, treatment and control of the problem can be discreet. The problems occur when we start experiencing mortalities as a result of severe infection. Such cases should be dealt with away from the eyes of the general public, either by removing all displayed fishes to the quarantine area or by screening the viewing panels to the public as treatment commences on display.
Disease outbreaks on display are also extremely costly because of the sheer volume of water needed to be treated for the length of time needed to destroy the parasite's life-cycle. Far too often treatment regiments are broken before this can become effective as seemingly "healthy" fishes are flushed of their therapeutants in ignorance. This not only creates a large window for reinfection over time but also running the risk of creating resistant parasite populations as repeated treatment regiments are sought after each failure. This was seen at Sea World with the discovery of the unique strain of Cryptocaryon irritans in August 2003 (D. Vaughan, Dr. K Christison). It was resistant to copper and formalin as well as quinine hydrochloride/malachite green mixture as well as for Aquavet Whitespot formula, which is extremely effective against the normal strain.
Disease outbreaks need to be dealt with quickly and correctly. Identification of the parasite or disease-causing organism ensures that the correct treatment protocols, including the correct detergent or chemotherapeutic chemicals are used. The misidentification or any assumption without the correct evidence is extremely dangerous and leads to complete or partial failures in determining the correct treatments and time-frames in treating the disease with associated high mortalities.
It is extremely important to treat the exposed area as a part of the quarantine area, where one person is responsible for the management of the quarantine procedure, which differs in situation between environments and disease-causing organism to the type of host.
Once introduced to an environment or system like an exhibit, which cannot afford to be stripped and cleaned after each disease outbreak in a controlled environment, it is extremely difficult to eradicate the disease causing organism. That's because it uses several factors present in a display or exhibit to evade extermination, not present or specifically eliminated in a controlled quarantine area. One of these is the presence of substrate. If we look at the life-cycle of Cryptocaryon irritans for example, as a common and highly problematic parasite, we can determine the three stages of its life-cycle. The adult parasite or the Trophont stage is responsible for the condition know as Cryptocaryoniasis or whitespot disease. This stage is the only parasitic stage and is the one that causes all the problems associated with the host. It is extremely effective as a parasite with very low host specificity and can tolerate a wide range of conditions. The second reproductive stage or the Tomont stage is the stage that causes my main concern in any exhibit or display, and is responsible for the ultimate reinfection of the host. This stage is encysted. As the adult Trophont parasite matures, it releases from the host fish, triggered by certain stimuli, which are still not well understood. The parasite falls to the substrate where it mills around for a few hours, enabling it to find a suitable site for encystment. Once encysted, this stage is completely resistant to treatment. The Tomont undergoes asexual reproduction through binary fission, creating up to 400 tomite cells within the cyst. These cells are released as Theronts, the highly active swimming and infective stage of Cryptocaryon, which find and attach to the host to begin the infection again. The problem with the Tomont stage is that these cysts may lie dormant for long periods of time, and are easily hidden and protected in the substrate and filter systems. If outbreaks of disease occurs, the treatment is designed to incorporate as accurately as possible the largest portion of released Theronts, which are the only really vulnerable stage of this parasite. The other problem is that the Tomont stages can randomly produce their Theronts usually between day 3 and day 28 after encystment, with the majority of Theronts being released on day 8. Temperature fluctuations play an important role here too, as the lower the temperature the longer it theoretically takes for Theronts to be produced. By increasing water temperatures more, Theronts are generally produced in a shorter space of time. However, a very small percentage of Tomonts have been recorded to lie dormant for up to 72 days before releasing Theronts, even after being subjected to high temperatures, which explains how some exhibits once this parasite is introduced experiences reoccurring problematic infections sporadically. Treatments only cover the theoretical percentage of produced Theronts from the cysts within a thirty day period. Any release of Theronts outside of this time-frame will result in reinfection, with the possibility of resistance to detergent therapeutants over time, as described earlier. This is one parasite that can however be eradicated with the correct approach. To eliminate the theoretical possibility of reinfection outside of a treatment time-frame, the hosts can be removed from the infective environment after completion of the thirty day course and placed in a sterile or uncontaminated new environment. This can only be done in a quarantine area, where the host fish is removed to the display after completion of treatment. Any fish carrying Cryptocaryon that is placed into a display or exhibit will be the vector and the source of a continuous and reoccurring disease problem, which is just one of the reasons why no fish is placed into a new uncontaminated display or exhibit without being correctly quarantined. To eliminate Cryptocaryon from a host-parasite interactive environment is almost completely impossible.
Other inhibiting factors include the high cost of treatment for a large volume of water associated with effected displays or exhibits. As we can see from above, to treat Cryptocaryon effectively, a thirty-day continuous treatment must be maintained, and even this is no guarantee that reinfection will not occur, which leads to repeated treatments and the loss of animals.
Problems associated with the second quarantine step include:
1) Loss of animals due to manifested infection
2) Host fishes are subjected to harsh aggressive treatments which could also play a role in the addition of stress or damage to the host.
Managing a disease on display or in an exhibit is possibly the only guarantee that we have to maintain the health of the displayed animals. This will be discussed as the third step of quarantine, I.P.M, which can be seen as the contingency plan for failures of both the first and second points.
I.P.M or Integrated Pest (Parasite) Management entails understanding specific and permanent disease problems within an environment. And using the knowledge of their reproductive habits and time frames together with environmental manipulation and strategic treatments, to maintain acceptably low levels of parasites, which can be more easily dealt with by the host's immune system.
To maintain the third step or I.P.M, is extremely costly in the long term from a public aquariums point of view, as the management of a disease once established in a display or exhibit will need to incorporate strategic use of specific detergent or chemotherapeutant chemicals. And these must be applied at vulnerable points in specific parasites' life-cycles by using the environment to create these vulnerable points in some cases, but on an ongoing indefinite rotated cycle.
A good example of this would be the control of certain Monogenean trematode infection in fish on display. The initial step is to correctly identify the disease-causing organism and to identify with its reproductive dynamics, especially the time in which it takes for reinfection and immature cells to reach sexual maturity. This information varies between species, but can be easily obtained through literature searches and the use of other professional opinions on the details of the subject, such as aquatic pathologists. Once this information can be determined, a treatment plan can be incorporated using specific detergent or chemotherapeutant chemicals that are known to be effective. The initial treatment is designed to remove the actual parasite from the host in the case of helminth parasites, or the reinfective stage of Cryptocaryon as it emerges from the Tomont stage. Juvenile or young parasites that emerge from the egg stage in the case of certain helminth parasites are allowed time to reinfect. But just before they become sexually mature, the second administering of the detergents or chemotherapeutants is used to remove them from the cycle. Any late-developing eggs outside a theoretical time-frame are dealt with by a third dose, repeated in the same length of time from the first and second treatment. Parasite numbers drop dramatically in the case of helminth parasites, and can be monitored until such point where another follow-up regiment can be implemented to again knock back increasing numbers.
With Cryptocaryon and other more difficult protozoan parasites, the infective stages can be greatly controlled in addition to the use of detergents and chemotherapeutants, by creating unfavourable conditions for their development by manipulating the environment for the complete life-cycle period. This dramatically reduces parasite numbers until they slowly build themselves up again.
Salinity reduction therapy or S.R.T is such a tool, which used in conjunction with drugs or chemicals, will have a negative effect on the parasite's life-cycle.
The success of S.R.T relies on its maintained level, which for Cryptocaryon and other protozoan parasites, as well as some other parasite groups, is recognised as below 16ppt (parts per thousand) in seawater, which generally has a salinity range of 32 - 36ppt. Most fishes can tolerate lowered salinity levels without problems if allowed to acclimatise over a period of a few days, as their bodies need to adjust their osmotic potential with the changing environment. I like to maintain the salinity levels at 15.8ppt during S.R.T. The idea surrounding S.R.T is that the lower animals, such as the disease-causing organisms cannot osmoregulate efficiently enough at these levels and their cells take in more water from the environment than can be released until the cells rupture killing the parasite. Used in conjunction with chemotherapeutants or detergents, a more effective control through a parasite's life-cycle is obtained and only a small percentage remain to reproduce in the environment, which are then subjected to a repeated, managed treatment programme to control and maintain their low numbers.
Problems associated with the third quarantine step include:
1) Not all fishes can be subjected to S.R.T
2) Parasite numbers are only controlled, thus a break in the management of the third step in quarantine can and will cause epidemics of certain parasites.
3) Expensive drugs are used in large treatment volumes repeated indefinitely and need to be budgeted for on an increasing basis.
4) The possibility of cross-contamination is a real threat to surrounding uncontaminated displays or exhibits
5) Any new additions to a contaminated system will be subjected to the same infection.
The forth and final step in the quarantine concept incorporates sterilisation, or the elimination of all life in a system.
This step is a last resort in eliminating disease-causing organisms from a system that were not effected by the first three. Fishes can be removed from a contaminated environment and placed in the quarantine facility where they can undergo the second stage to eliminate their parasite loads, while the exhibit or display environment is sterilised, using oxidizing agents such as bleaches to destroy all remaining life. All life-support system components are equally treated and the display or exhibit is flushed after a period of a few days and returned to normal. This allows for the maturation of biological filtration and the correct water quality parameters before disease-free fishes are again reintroduced after their completion of the correct treatment protocols in quarantine.
Sadly, it is sometimes recommended to eliminate even the host itself in the search for complete disease eradication from a system using euthanasia, in severe cases.
Problems associated with the forth quarantine step include:
1) Closing displays to the public for duration of sterilisation.
2) Restarting and re-stocking of displays, where substitute display animals need to be found to replace those undergoing the second quarantine step.
3) Loss of display animals from disease.
4) Euthanasia of displayed animals.
In the above we get a feel for what I call the quarantine concept. All points with their own intricacies make up a complete quarantine, one that is successful and successfully managed.
