Quarantine - a brief introduction...

Discussion in 'Quarantine Tanks, sick fish, QT corals' started by David Vaughan, 9 May 2011.

  1. David Vaughan

    David Vaughan

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    Quarantine is a diverse topic and one which cannot adequately be covered in a single post. It is a dynamic concept but one which is extremely valuable and which should be considered as a priority when purchasing ANY fishes for your home aquarium.

    One of the most common problems associated with the introduction of new fishes is the introduction of their parasites which they may be carrying into your system. Of all the many problems, parasites pose one of the most important because many of them have the ability to reproduce quickly in a closed system using a single host to close their life-cycle. These parasites (those with a direct life-cycle) have the ability to be the most destructive. To begin with however, we need to try and understand what happens when a seemingly healthy fish is introduced into your home tank and shortly thereafter you have an infestation.

    Parasites are incredibly well adapted organisms and demand much respect. Most are highly specialised and have evolved to fill a very specific niche so narrow that some are only found in a single micro-habitat in or on a host, on a single host species, without which they would cease to exist. Parasites and their hosts are constantly in a battle to survive. Parasites are evolving ways of evading the host immune system, while host fishes are evolving ways to exclude their parasites. This constant conflict, often referred to as the “parasitic arms race” reflects what is known as the Red Queen Hypothesis which states that in order to survive, these organisms are constantly having to “run on the spot to keep up.” So, there is an intricate balance then between the host, the parasite and the environment which may or may not lead to the outbreak of disease. This balance is called the host-parasite dynamic. If we look at each of these as factors, we can take a deeper look and get a deeper understanding of how each influences this dynamic.

    Factor 1: Host (A fish population being invaded by a parasite has 3 mutually-exclusive cohorts that can change in relation to one another during the course of disease.)

    • The susceptible group: those than can become infected
    • The infected group: those susceptible, now infected
    • The removed or immune group: acquired immunity or death
    Factor 2: Parasite

    • The ability to infect a particular host species
    • The parasite’s level of infectiveness (its pathogenicity)
    • The parasite’s virulence
    • The mode of parasitism
    • Parasite or parasitoid?
    Factor 3: Environment

    • The environment can have a significant influence of the transmission and the development of disease
    • Population density is critically important in the dissemination of disease
    • Frequency of contact between the infected and susceptible hosts individuals (direct and indirect contact)
    • Reduced host spatial arrangements and improved likelihood of successful invasion by re-infective stages
    • Temperature, water quality, chemicals, water flow
    • Stress and immunosuppression
    Quarantine, the word, traditionally means isolation for 40 days. However, quarantine as we know it is often the isolation of new acquisitions or sick fishes from a healthy population to reduce the risk of introducing disease from individuals of the infected group to the susceptible group. All wild-caught fishes have parasites. When they are collected from the wild they are often maintained in small tanks with high stocking densities, increasing the risk of not only parasitic transfer between individuals, but also the frequency and success of transfer to individuals that are stressed and have a compromised ability to deal with infections through the immune system. In addition, water quality (particularly temperature) can play an important role in speeding up parasite life-cycles which puts additional strain on the frequency of successful invasion. Often, by the time you receive your fishes from a supplier, if they have not been adequately and CORRECTLY quarantined, they pose a significant risk of infection to your fishes if directly introduced. Here, prevention is the most effective action. A quarantine tank, completely separate from your main setup is invaluable because the period of isolation will allow for the manifestation of disease symptoms and therefore allow you to make a correct diagnosis which is imperative in choosing the correct treatment. You may also treat your fish before they exhibit any symptoms prophylactically, and after a period of at least 30 days in isolation with treatment can be considered of low risk to be introduced into your main tank.

    Bear in mind that unless all of your fishes have been introduced this way, you may have a resident population of a parasite living comfortably within the realms of the dynamic equilibrium in your tank until this equilibrium is disturbed with the introduction of a new individual. It is common for a Cryptocaryon irritans infection for example to be present without exhibiting any symptoms of disease, but will be ticking over while being “managed” by the immune system of the various host fishes. The introduction of the new fish presents a susceptible individual which allows for a shift in the equilibrium and therefore the likelihood of the onset of disease. This often begins with the new individual but could then again spread to the others until the equilibrium is again satisfied.

    So, given that I am rambling on a bit here, DO quarantine your new fishes. It reduces but does not exclude risk. How to quarantine? This is another long and complicated affair and deals with diagnosis, specific treatments that are tolerant of specific host species and an understanding of IPM (integrated parasite management). One also needs to consider the risks and assign priorities to certain conditions, but here are some basic pointers:

    • Treat separate purchases of fishes separately and do not mix quarantine periods to add new fishes or break treatments
    • Treat ubiquitous parasites (those of low host-specificity) with priority
    • Ensure that your quarantine system is completely separate from your main system and use a separate set of nets and cleaning equipment for each
    • Keep low levels of light in the quarantine tank with some structures for fishes to hide in
    • Do not have substrate in your quarantine tank. This can harbour parasites and can also absorb some chemicals from treatments
    • Ensure your climate control is tight (no wild fluctuations in temperature or general water quality). Use a filter that can maintain your water quality but one which can be used with treatments
    • Feed good quality foods but keep to a minimum to avoid poor water quality
    • Keep records of your quarantine periods, species quarantined, where they came from and any observations which you made that may be useful in future
    The various treatments available are as diverse as the problems they treat. Ensure that whatever treatment covers the life-cycle completion time of a known parasite (if you know what you are treating for) or at least the prescribed 30 days of prophylaxis. Some home-aquarist remedies make interesting claims about their products working in a short period of time. These are often inaccurate because parts of disease life-cycles are treatment resistant and these treatments are usually only treating for the symptoms and will not address the root cause of the disease. I always treat for 30 days, with water volume re-treated daily after a complete water change, this or through an IPM strategy given the biological parameters of a know parasite and the effects of the captive ecology on the biology. This is complicated but I can go into more detail again in subsequent posts.

    I hope that the above gives a basic introduction to quarantine but I find that an understanding of the question “why?” is often the most valuable – so keep asking this question until your queries are satisfied. Let’s together take quarantine and its many facets to the endth degree.

    Regards

    David
     
    Last edited: 9 May 2011
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  3. rakabos

    rakabos

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    Excellent post. Maybe we can make a list of the common parasites and how to treat it, if such a list doesnt already exist?
     
  4. seank

    seank

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    Wow is all I can say. Now at least I have learn't something today. Thank you for your time and effort posting here David
     
  5. David Vaughan

    David Vaughan Thread Starter

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    Mmm, Rakabos' suggestion would be useful but as many ways there are to skin a cat, there are to treat a disease...

    I guess we could start by adding the basics, yes. I will get to this a bit later.

    Regards

    David
     
    Last edited: 9 May 2011
  6. crispin

    crispin

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    can u share thoughts on how many fish per tank in quarenteen, seeing as a singular system is required and what size tank for specific fish should be used. what i mean is it ok to have some chromis and a goby together in the same tank, or should they be seperate and do you have to have larger tanks for fish like tangs as opposed to anthias (for simplicity) ?
     
  7. erle_vaughan

    erle_vaughan

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    I was wondering... what about if i put a fish in the QT and then say ten days later acquire a new fish... can they new guy get added to the QT or must he get his own QT?
     
    Last edited: 9 May 2011
  8. dallasg

    dallasg Moderator MASA Contributor

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    thanks David, this is an awesome post/resource
     
  9. Reef Maniac

    Reef Maniac MASA Contributor

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    :P: :P: I told you so, I told you so :tt2:

    David, THANKS for this excellent post :thumbup:

    Hennie
     
  10. AndrévN

    AndrévN

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    Awesome read ty
     
  11. Tobes

    Tobes Retired Moderator

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    Nope, the chances are there that the new fish can infect the one being in QT, then all your effort was for nothing and QT must start from scratch for that fish as well. Better to get seperate QT or wait for the first one to finnish.
     
  12. erle_vaughan

    erle_vaughan

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    so if a fish is in the QT already and a new one is added... basically the QT period should start over from when the last fish was added...(if getting 2 QT's is a hassle)
     
  13. Tobes

    Tobes Retired Moderator

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    Yes, I would say so
     
  14. David Vaughan

    David Vaughan Thread Starter

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    Good morning.

    I agree with Tobes. The risk of cross-contamination is a problem and you never know what you might add by mistake. With quarantine it takes some dicipline to let one set of fishes run though quarantine before beginning with the next lot.
     
  15. David Vaughan

    David Vaughan Thread Starter

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    Crispin, sorry for the late response to your query:

    Quarantine size is up to you and depends on what size fish you wish to quarantine. In general the same rules apply for your main system where it should be kept in mind that changes to water quality happen more rapidly in a smaller system. For the fishes you mention, a 100L tank should be fine. Keep stocking levels to a minimum but also keep in mind that some fishes cannot be quarantined together for a variety of reasons. These include competition for food and fighting (general incompatibility issues) and different tolerance levels to treatment chemicals. Gobies are generally more fussy when it comes to treatments and these I would keep separate for signs of sensitivity.
     
    Last edited: 10 May 2011
  16. Reef Maniac

    Reef Maniac MASA Contributor

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    Hi David,

    Some questions, if you don't mind:

    I have for many years now had similar thoughts, having witnessed long-established, stable tanks that have not had any new additions for many months develop a C. irritans outbreak after a severe temperature drop caused by power outages, etc.

    On the other hand, scientific literature and personal discussions with amongst others a professor specialising in fish parasites, indicate that, as this parasite is an obligate parasite with no intermediary hosts, it would not be possible for it to continue in a normally populated aquarium indefinitely. I have further read (cannot recall where) that an experiment has shown that C. irritans became weakened and eventually died out during a period of repeated re-infections of some fish in a closed system.

    What are your views on this?

    From personal observations and numerous "reports" on the 'Net, there is anecdotal "evidence" that fish do not become "sick" as easily in a mature reef tank than in a fish-only system. It is my belief that this could be as a result of predation by the tank's "small critters" and (perhaps even) SPS corals on the free swimming stages of these parasites. I have done numerous observations of my tank's sand bed "goggas" (and there must be millions of them...) and I would not like to meet many of them in a dark alley at night :eek:

    I further believe that stress in newly acquired fish is a serious matter to contend with, as it (amongst others) reduces their natural immune system. To my mind, it is much less stressful on the fish if it can swim in a tank with a nice sand substrate, natural rock to hide in, and some macro algae to provide cover/shade, rather than to be confined to a "sterile" bare tank with very little place to hide.

    I thus, contrary to your recommendation, have an old tank which has been set up for some years now with a deep live sand bed, just "ticking over" with no fish (but housing some excess corals), for use as a Q-tank. The water quality of this tank is kept the same as my display tank ("full strength" sea water, undetectable NO3, etc). Whenever I buy new fish (and that does not happen all that often), they go into this "natural" Q-tank for a period of at least 28 days before being added to my tank. Should they develop any disease during quarantine, they are transferred to a "hospital tank" (bare, with only a few pipes for hiding) for treatment.

    Although this has worked very well for me, I would really appreciate your comments on this.

    Thanks,

    Hennie
     
    Last edited: 10 May 2011
  17. David Vaughan

    David Vaughan Thread Starter

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    Hi Hennie

    Thanks for the post. I find it interesting that a parasitology professor would think that Cryptocaryon irritans could not survive indefinitely in a captive environment. Cryptocaryon irritans certainly is obligate but has a direct life-cycle and therefore has the advantage in captivity over those with an indirect life-cycle (those who require intermediate hosts to complete the life-cycle) because its hosts are always available for re-infection and to close the life-cycle. It is often difficult or impossible for those parasites with an indirect life-cycle to complete their life-cycle in captivity and especially in a home aquarium where some or all of their intermediate hosts are missing. In these instances the intermediate hosts are often represented by various invertebrates and higher vertebrates (sometimes birds), and for the parasite to reach adulthood for reproduction, their intermediate stages would have to be consumed. One should always remember that the absence of evidence is not the evidence of absence and that parasitism in its most natural form is not designed to cause disease although parasitology does ilicit a host immune response. I have studied and completed the life-cycle of C. irritans SA strain (coldwater strain 1) and evaluated the effects of ecology on embryonation and theront production. It is unlikely that the fishes' immune system in a tank would completely erradicate a C. irritans infection but over time it certainly would reduce the numbers to sub-clinical levels where no symptoms are expressed. This is not an indication that the parasitic organism is becoming weaker, but rather that the dynamic equilibrium is being restored. Obligate parasites (excluding parasitoid) have a vested interest in keeping their hosts alive. Without hosts, they die too. So for the parasites, a very low intensity and guaranteed hosts for re-infection is just what they need to survive and this is pretty much what happens in nature. Any parasitologist will confirm that when sampling wild hosts, parasite intesities are generally very low. So, basically to answer your question, no I do not believe that C. irritans would simply die out in a closed system when they have everything necessary to maintain their own survival at sub-clinical levels. This would have no evolutionary significance, and given that C. irritans is such a successful ubiquitous parasite, it would also make little sense.

    Your points on the reef tank versus the fish only tank are very interesting and are of value. Parasitologists like me actually know very little about the intricate relationships in the ecology of parasitism and it is a fascinating world. Your observations are valuable because these often lead to scientific investigations that support them. I am not surprised that the prevalence of parasitic diseases are lower in reef systems because I can imagine how free-swimming parasite larvae and infective stages could fall prey to other filter-feeding organisms as you mentioned. Yes, I agree with you regarding stress and that stress reduction is one of the most important key factors in the success of fish husbandry. Your suggestion of moving sick fish to a hospital tank if they exhibit disease symptoms is also warranted but do keep in mind that compromise is key and that you need to find the balance between "necessary" minimal stress and the risk of disease introduction with fish that have not been treated prophylactically.

    I hope this has been useful. Let me know if anything needs further clarification.

    Regards

    David
     
    Last edited: 10 May 2011
  18. dallasg

    dallasg Moderator MASA Contributor

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    thanks for taking the time and replying in detail...
    you should get your own parasitology forum here...
     
  19. Reef Maniac

    Reef Maniac MASA Contributor

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    Dallas, I heartily concur

    David, THANK YOU for your valued input :thumbup:

    So, are you suggesting that one should ALWAYS treat prophylactically when quarantining? I suppose that it does make sense if the parasites can re-infect their hosts without them showing any signs of infection... especially if "quarantined" the way that I do... hmmm will have to think about this one...

    Hennie
     
  20. David Vaughan

    David Vaughan Thread Starter

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    Hi Hennie

    Yes, where possible it is always good to treat everything prophylatically. I did say this with caution too however. Please keep in mind that this refers to the use of detergent chemical treatments and not antibiotics. Antibiotics when used should only be used after an antibiogram has been performed so that you know exactly what antibiotic will be effective (this is a veterinary or pathology service). This reduces the risk of acquired disease resistance and the creation of drug-resistant strains of bacteria. I fear that in the future we will have increasing problems with resistance because of the unregulated nature of the treatment-beast!

    Regards

    David
     
  21. David Vaughan

    David Vaughan Thread Starter

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    An interesting book on the subject

    Hello again

    Here is a link to a book which covers some interesting general topics around the relationships between host and parasite for those who are interested:

    Bentham Science Publishers Ltd. Home Page

    Regards

    David
     
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