Aquarium.Net Feb 97 Diseases in = Fish Part 5=20

This month Shawn Prescott has = written on=20 Chilodonella, Cryptocaryon irritans, causes, cures and prevention, = Aquarium Net has numerous articles written by the leading authors = for the=20 advanced aquarist

Diseases in Fish Part 5.

= Shawn=20 Prescott

Last month I began the long examination of the various diseases = to=20 which are fish are prone, with a division of the ailments into the = different divisions which is the methodology used in Fish = Pathology. For=20 those of you who read this column, you will recall that I began = with the=20 freshwater parasite commonly known as "white spot" or "Ick" , the=20 scientific name being Ichthyophthirius = multifiliis=20 . This parasite was chosen, because it is = probably=20 the most ubiquitous of all the ailments that strike in fresh water = Aquaria, & is common in Aquaculture as well.

Afterwards, as I began to contemplate the topics for discussion = in the=20 next version, I realized that a high percentage of you, (judging = by the=20 "hits" & the articles we have currently) are Salt water = enthusiasts,=20 so I have decided from now on, to try & balance the articles, = with an=20 examination of a fresh water and a salt water disease with each=20 contribution.

In freshwater this month, we will examine the parasite known as = Chilodonella , whilst for salt water we will look at the=20 counterpart of Ichthyophthirius multifiliis , which is=20 Cryptocaryon irritans . If any of you out there = in the=20 wide world of cyberspace, have any questions about the articles, = or if=20 there is a subject you would especially like me to deal with, = please=20 contact me at my E-Mail address fishvet@jagunet.com. =

3D""=20 =20

Moderate to heavy infestation of C. irritans on Tomato Clown =

Chilodonella cyprinii. Causative = organism:=20 Ciliated protozoan parasite viz:- Chilodonella cyprinii . = Synonyms ( alternative names):- None Geographic distribution. = World wide.=20 Water type . Fresh water. Typical signs of infection. = Chilodonella=20 cyprinii.

Water. Poor water quality can bring on the=20 reproduction of the parasite, as the fish become stressed.

Behaviour. Laboured breathing, and fish may = appear at=20 surface gasping for air. Fish will evidence lethargy, and may from = time to=20 time, try to "scratch" of the organisms, by rubbing against an = object of=20 some kind in the Aquarium. Distress is visibly obvious.

Fins. Fins often become clamped or folded

Body. Excessive mucous production is typical, = &=20 parts of the body will manifest a cloudiness as large numbers of = the=20 parasite begin feeding of the epithelial layers.

Gills. Gill examination will show large = numbers of the=20 leaf shaped organisms .

Skin. (smear). Should show ciliates once an = infection=20 has become established.

Life cycle & method of transmission.

This protozoan parasite occurs frequently in fresh water = Aquaria, &=20 has a counterpart in marine aquaria called Brookynella. The = parasite is=20 vaguely leaf shaped with a length of 40-70 microns, & a width = of some=20 30-50 microns. The ventral side of the parasite is covered with = cilia.=20 Inside the cell for those of you, who have a microscope, & = wish to=20 examine same, are a nucleus and two contractile vacuoles. These = are made=20 more evident, by staining the slide with a smear taken from an = infected=20 fish, using a stain such as methylene blue, or methyl violet.

Reproduction of the parasite takes place typically by mitotic = division,=20 but from time to time a pairing of two individuals takes place = called=20 conjugation, and an exchange of some genetic material probably = takes=20 place.

As with many parasitic infestations, Chilodonella can = lie=20 dormant for long periods of time, but if and when the fish becomes = stressed or weakened for any reason, or if the quality of the = water=20 conditions in the Aquarium deteriorate, then rapid reproduction of = the=20 parasites can ensue, and once the gills are attacked mortality is = to be=20 expected.

Prognosis

When a heavy infestation of Chilodonella has taken = hold, then=20 some casualties are to be expected. Usually certain species such = as=20 Discus, will become infected most severely first, but if untreated = other=20 varieties will succumb as well. However if correct treatment is = applied in=20 good time, then it can not only be checked but it is also possible = to=20 eliminate the parasite.

Young fish have less capacity to resist the parasite, & = will more=20 easily succumb.

Treatment

Fortunately if successfully diagnosed , there are several = treatments=20 that can be used.

These include the use of formaldehyde used as a bath, also = Acriflavine=20 type drugs, along with methylene blue, as well as quinine type = drugs all=20 are effective. One should follow the manufacturer's instructions = for=20 treatment, as different producers, use different concentrations, = & it=20 is therefore impossible to give a standard treatment for all the=20 medications out there. Fish-Vet ™ also producers a very=20 effective treatment for this condition called Revive.

In treating the fish, one should always make allowances for the = degree=20 of infection, as weakened fish may not always withstand the full = dosage,=20 either in strength, or period of time. This call is one which = either one=20 builds up experience over time, or enlists the help of a = professional, or=20 a dealer whose expertise you can trust.

As Chilodonella is not affected by change of water=20 temperature, no alteration should be made to your thermostat.

Bibliography.

Langdon et al. 1985. Death in Australian freshwater fishes = associated=20 with Chilodonella hexasticha infection. In Australian Veterinary = Journal=20 62, 409-413

Untergasser D. 1989. In Handbook of Fish Diseases. Publ. TFH = page 95.=20

Van Duijn C. 1973. In Diseases of Fishes . pages 70-72.

Cryptocaryon irritans = Causative=20 organism: Ciliated protozoan parasite viz:- Cryptocaryon=20 irritans Synonyms ( alternative names):- Marine = white spot.=20 Geographic distribution. World wide. Water type . Salt water. = Typical=20 signs of infection. Cryptocaryon irritans.

Water. Less than optimum water quality, such = as a=20 lowering of the pH level, or high Nitrate or Phosphate readings = can lead=20 to an outbreak.

Behaviour. Fish will evidence lethargy, and = may from=20 time to time, try to "scratch" of the organisms, by rubbing = against an=20 object of some kind in the Aquarium. Distress is visibly obvious. =

Fins. Fins often become clamped or folded. = White spots=20 (after which the disease is popularly named) usually appear often = at first=20 on the pectoral fins. As infection progresses, very large numbers = of these=20 spots of size 0.5-2.0 mm will spread .

Body. White spots appear on = the body,=20 & will if untreated spread so that almost snow like appearance = will=20 spread over its entirety. Some haemorrhaging may appear in later = stages of=20 the disease.

Eyes. In medium to advanced stages of an = outbreak, the=20 eyes typically become clouded, & when very heavy blindness can = ensue.=20

Gills. Gill examination will show large = numbers of the=20 organisms .

Skin. (smear). Should show ciliates once an = infection=20 has become established. Secondary infection with fungal is = commonplace=20 once major invasion of the skin has taken place, adding to the = problem.=20

Life cycle

Transmission is direct, with no intermediate hosts. = Cryptocaryon is=20 an obligate parasite, which means that it must infect a host = fish in=20 order to complete development.

3D""=20 = =20

Life cycle of Cryptocaryon irritans. Chart by Dr.Peter Burgess. =

The life cycle of Cryptocaryon can be conveniently = divided=20 into four basic stages. Susceptible marine fish become infected = with the=20 active free-swimming stage, called the theront (or tomite).

The theront is incapable of feeding within the aquatic = environment and=20 therefore has a limited time, less than 12 hours, in which to = contact and=20 invade a fish, otherwise it will exhaust its energy reserves and = die. If=20 invasion is successful, the theront penetrates below the skin = epithelium,=20 possibly aided by digestive enzymes such as hyaluronidase, and = transforms=20 into the parasitic stage which is known as a trophont. The = trophont=20 actively feeds on the fish's tissues, twisting and rotating as it = does so.=20 It grows rapidly, doubling in size approximately every 24 hours. = By 48=20 hours, the parasitic trophont is just visible to the naked eye, = appearing=20 as a small white spot on the fish. By the third or fourth day of=20 infection, the trophont will have attained 3 to 5 millimetres in = length=20 and at about this time it exits from the fish. Although the = trophont is=20 equipped with rows of beating cilia it is too bulky to swim away = from its=20 host and instead it sediments to the substrate. (Compare with = freshwater=20 whitespot in which the trophont stage actively swims after leaving = its=20 host). Within a few hours, the trophont has firmly attached to the = substrate and rounds up to form a thick-walled cyst. The cyst, = also known=20 as a tomont, is the reproductive stage which will eventually give = rise to=20 between 100 and 300 infective theronts, thereby completing the = life cycle.=20 Of course, not all theronts are successful in locating and = infecting a=20 host, even under ideal conditions only about 5-10% succeed. = Nevertheless,=20 within an closed environment, Cryptocaryon can increase = in=20 numbers by approximately tenfold every six to eight days. This = enormous=20 reproductive potential explains the sometimes rapid build-up of = infection=20 levels in any closed system..

[an error occurred while processing this directive] The cyst is = the=20 only stage of Cryptocaryon which is known to reproduce; = there is=20 no conclusive evidence to suggest that the parasitic trophont = stage can=20 multiply within the fish's epithelium.

Prognosis

There is no reason why mortalities should take place, as to = reach=20 lethal levels this parasite usually takes some 7-12 days. = Observant=20 hobbyists should take remedial action, at an early stage & if = this is=20 done, and the results CAREFULLY monitored than a successful = eradication of=20 the problem is possible. Care must be taken, to ensure that no = latent=20 parasitic tomonts are still present, so that the problem does not = recur.=20

Treatment

In those Aquaria, where fish only are present, Copper based = remedies,=20 are very effective, although those chelated forms of Copper of = which there=20 are several have not in the writers experience given good results. = The=20 claim that you can use heavy doses of such Coppers, without = harming the=20 fish may be true, regretably the same argument applies to the = parasite.=20 With the true Copper treatments that are effective it is vital to = use a=20 reliable Copper test kit, & in the first few days of treatment = this=20 must be done several times daily, as the Copper in a new tank to = be=20 treated, "binds' to the glass the rocks, & just about anything = else,=20 so that the theurapeutic level drops below the recommended amount, = &=20 under this the parasite is able to complete its life cycle. = Treatment=20 should be continued for at least 7 days after all signs are = absent, to=20 ensure that no latent tomonts are waiting the chance to reinfect. =

In Reef Aquaria, however no Copper treatments can be used, as = they all=20 will have fatal effects on almost all Inverterbrate life. This = leaves the=20 Hobbyist with the alternative of catching his/her fish, & = treating in=20 a separate Aquarium. This is time consuming & can often ruin = the=20 appearance of a tank that has been carefully nurtured over a long = period=20 of time.

Fortunately Fish-Vet =C2=AE has today a product called = Ecolibrium =C2=AE, which=20 allows successful treatment of this scourge, and is harmless to = all=20 Invertebrates. We will be pleased to advise any Hobbyist where = this=20 product can be obtained form a dealer in your area. No test kits = are=20 needed & it biodegrades after a week, when treatment is = ceased.

Another technique which can be used to help accelerate the = eradication=20 of the problem, is by giving the fish baths in either fresh water, = or at a=20 salinity of less than 10 ppt. The parasite cannot tolerate the = change in=20 osmotic pressure, though I am not sure if it will affect the = tomite stage=20 as much as it will the free swimming trophont. This technique has = been=20 used very successfully in Aquaculture with those species of fish = that are=20 highly euryhaline (=3D able to tolerate wide variations of = salinity). Our=20 Aquarium fish for the most part will tolerate baths of up to a = half an=20 hour, but one must ensure that the pH & Temperature are = similar to the=20 Aquarium water. Also do not do any other task whilst the bath is = taking=20 place, as some fish will react worse than others. If major = distress is=20 observed, the fish must be returned to the Aquarium. I have used = this=20 method to reduce the level of infection, & it has proved = beneficial,=20 though never absolute. It's greatest advantage is when the fish = shows=20 evidence of a high level of infestation, & one wishes to bring = it down=20 somewhat before starting more conventional treatment. For more = details on=20 the use of this method see the ref. below by Colorni 1987.

There is some evidence that there are 2-3 different strains of=20 Cryptocaryon irritans , nobody to my knowledge has yet = made a=20 definitive analysis of such, but the empirical evidence would seem = to=20 indicate this. One observation made by many observers, is that the = treatment that in one case is quickly and totally successful, in = another=20 either is not, or takes much longer to have an effect. One = pragmatic point=20 that the writer has used with success is those persistent cases, = that=20 either do not appear to react to conventional treatments , or do = so much=20 more slowly, is that it seems that the parasite is in some way = linked in=20 its life cycle to the photoperiod. In order to disrupt its usual = timing of=20 division, reproduction etc, I have found it helpful on occasion to = leave=20 the lights on , for some 2 days, & then do the opposite whilst = at the=20 same time covering the tank with a dark blanket or suchlike. This=20 "manipulation" of the light seems to have a deleterious effect on = the=20 parasite, which coupled with the medication used often results in = its=20 elimination. I do not advise this however in the more usual = straight=20 forward cases.

A special observation:- The writer has observed with some of = his=20 co-workers on many occasions, that Crytocaryon irritans = often=20 breaks out under the following conditions. The Hobbyist will have = a tank=20 with several specimens all of which are free of any signs of the = parasite.=20 A new fish will be introduced & the following day, "white = spots" will=20 be observed in a great many cases, NOT on the new introduction, = but on one=20 of established inhbitants. This happened so often so years ago, = that we=20 made some experiments on apparently "disease free fish". Most = especially=20 some powder blue, & yellow Tangs.

3D""=20 =20

Cyst of C.irritans

We found on these fish, which had been free of all problems for = more=20 than half a year, that when we did some skin scrapings, that we = found=20 evidence of trophonts under the skin. Evidently these had not = found it=20 necessary to reproduce & leave the fish, as no sign of disease = had=20 occurred over a long period of time

With this evidence we explained the phenomena just mentioned as = follows:-

A parasite by definition has a vested interest in co-existing = with it's=20 host. As long as no unusual disturbance takes place, it will = continue it's=20 idyllic existence , in harmony with it's host. However when a new = specimen=20 is introduced to the Aquarium, often the established inhabitants = become=20 quite excited, feeling that the newcomer will in some way, take = their=20 "space", eat their food, or even team up with their favourite=20 fish/companion. This causes some form of chemical message to = course its=20 way through the fishes system, in much the same way, as adrenalin = causes=20 us, to become excited if we get a fright or suchlike. This = chemical=20 message, in some way alerts the parasite, which in effect says to = itself,=20 "Oh boy!, maybe I should get out from here, & look for a new = host".=20 The consequences are seen the next day, when it bores out from the = host,=20 leaving the telltale white spots.

To counteract this reaction, as much as possible, it is advised = when=20 introducing new fish to an established Aquarium, to do the = following.

1) Introduce all specimens with the lighting as subdued as = possible in=20 the room, & with no lights on in the tank, continue this at = least=20 until the following day.

2) Change if possible one or two rocks, so that the existing = fish are=20 concentrating their attention on the change in the habitat they = are used=20 to, & not on the newcomer(s).

Of course it is also sensible if the Hobbyist has the facility = to=20 quarantine the new specimen, as they also can and do, introduce = the=20 parasite to the tank . This should be done if one has a separate=20 quarantine tank, for at least a week, & preferably for 10 = days.

Well that's it for this month, see you again in March.

Shawn Prescott mailto:fishvet@jagunet.com

Biobliography:-

Burgess, P.J. and Matthews, R.A. (1994). A standardized method = for the=20 in vivo maintenance of Cryptocaryon irritans (Ciliophora) = using=20 the grey mullet ( Chelon labrosus ) as an experimental = host.=20 Journal of Parasitology, 80, 288-292.

Burgess, P.J. and Matthews, R.A. (1994 ). Cryptocaryon = irritans=20 : (Ciliophora): photoperiod and transmission in marine fish. = Journal=20 of the Marine Biological Association, 74, 535-542.

Burgess, P.J. (1995). Marine Whitespot Disease. Freshwater and = Marine=20 Aquarium, 18 (1), 168-196.

Burgess, P.J. and Matthews, R.A. (1995). Fish host range of = seven=20 isolates of Cryptocaryon irritans (Ciliophora). = Journal=20 of Fish Biology, 46, 727-729.

Burgess, P.J. and Matthews, R.A. (1995). Cryptocaryon = irritans=20 (Ciliophora): acquired protective immunity in the = thick-lipped=20 mullet, Chelon labrosus . Fish and Shellfish Immunology, = 5,=20 459-468.

Cheung, P.J., Nigrelli, R.F. and Ruggieri, G.D. (1979). Studies = on=20 cryptocaryoniasis in marine fish: effect of temperature and = salinity on=20 the reproductive cycle of Cryptocaryon irritans Brown, = 1951.=20 Journal of Fish Diseases, 2, 93-97.

Cheung, P.F., Nigrelli, R.F. and Ruggieri, G.D. (1981). = Scanning=20 electron microscopy on Cryptocaryon irritans Brown 1951, = a=20 parasitic ciliate in marine fishes. Journal of Aquariculture, 2, = 7~72.=20

Colorni, A. (1987). Biology of Cryptocaryon irritans = and=20 strategies for its control. Aquaculture, 67, 236-237.

Colorni, A. and Diamant, D. (1993). Ultrastructural features of = Cryptocaryon irritans , a ciliate parasite of marine = fish.=20 European Journal of Protistology 29, 425-434.

Diamant, A., Issar, G., Colorni, A. and Paperna, I. (1991). A=20 pathogenic Cryptocaryon -like ciliate from the = Mediterranean Sea.=20 Bulletin of the European Association of Fish Pathologists, 11, = 122-124.=20

Herwig, N. (1978). Treatment of Cryptocaryon - = saltwater Ich.=20 Tropical Fish Hobbyist, 26, 55-62.

Matthews, R.A. and Burgess, P.J. (1995). Cryptocaryon = irritans=20 (Ciliophora): primary infection in thick-lipped mullet. = Journal of=20 Fish Diseases, 18, 329-335.

Nigrelli, R.F. and Ruggieri, G.D. (1966). Enzootics in the New = York=20 aquarium caused by Cryptocaryon irritans Brown, 1951 (=3D = Ichthyophthirius marinus Sikama, 1961), a histophagous = ciliate in=20 the skin, eyes and gills of marine fishes. Zoologica, 51, 97-102. =

Violetta, G. (1980). A review of two epizootic marine = protozoans:=20 Oodinium ocellatum and Cryptocaryon irritans .=20 Freshwater and Marine Aquarium, 3, 52-53,70-72.

Wilkie, D.W. and Gordin, H. (1969). Outbreak of = cryptocaryoniasis in=20 marine aquaria at Scripps Institution of Oceanography. California = Fish and=20 Game, 55, 227-236.

Yoshinga, T. and Dickerson. (1994). Laboratory propagation of=20 Cryptocaryon irritans on a saltwater-adapted Poecilia = hybrid, the=20 black molly. Journal of Aquatic Animal Health 6, 197-201.

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