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Aquarium F ish Derm atologic D iseasesK. Marcia Murphy, DVM, and Gregory A. Lewbart, MS, VMD

A q u a r i u m f is h a r e o n e o f th e l a rg e s t g r o up s o f p e t s k e p tin t he Un i t ed S t a t e s . The re i s an eve r i nc rea s ing de -mand fo r ve t e r ina ry s e rv i ce s r e l a t ed t o pe t f i sh . Ea r lyc l i n ica l s igns i n ma ny in f ec t ious and n on in fec t i ous d i s -ea se s o f f ish a r e m an i f e s t ed by t he sk in . I n th i s ' a r t i c l e ,w e h a v e r e v i e w e d a n d d e s c r i b e d t h e m o r e c o m m o ne n v i r o n m e n t a l a n d p a t h o g e n - r e l a te d d e r m a t o l o g i c d i s -ea se s o f pe t f i sh . D i sease p reven t ion , con t ro l , and va r-i ous t r ea tm en t p ro toco l s a l so have been d i s cus sed .C o p y r i g h t 9 1 9 9 5 b y W .B . S a u n d er s C o m p a n y

K e y w o r d s : A q u a r i u m , f i s h , s k i n , d e r m a t o l o g y, d i s ea s e .

A s i n a l l v e r t e b r a t e s , t h e s k i n o f t e l e o s t f i s h( b o n y f i s h es ) c o n si s ts o f a n e p i d e r m i s a n d

d e r m i s s u p p o r t e d b y a h y p o d e r m i s o r s u b cu -t a n e o u s l a y e r ( F i g 1). I n g e n e r a l , t h e e p i d e r m i sis v e r y t h i n a n d c o m p o s e d , f r o m t h e i n s i d e o u t-w a r d , o f a b a s a l l a y e r o f g e r m i n a l c e ll s ( s t ra t u mg e r m a n t i v u m ) , a v ar ia b le n u m b e r o f la y e rs o fc u b o i d a l t o s q u a m o u s c e l l s ( s t r a t u m l u c i d u m ) ,a n d a n o u t e r c u t i c l e l a y e r. l ' 2 T h e t h i c k n e s s o ft h e s k i n a n d e a c h o f i ts l a y e r s v a ri e s b e t w e e na n d e v e n w i t h i n s p e c i e s , d e p e n d i n g o n a g e ,

s e a s o n o f t h e y e a r , a n d l o c a t i o n o n t h e b o d y.A l t h o u g h s o m e f is h d o h a v e k e r a ti n i z e d s u r-f a c e c e l l s , t h e o u t e r e p i d e r m a l c e l l s o f f i s h a r eu s u a l l y l i v in g a n d d o n o t h a v e k e r a t i n i z e d s ke l-e t o n s . 1 T h e c el ls o f t h e s t r a t u m g e r m a n t i v u mm o v e u p w a r d a n d o u t w a r d u n t i l th e y a r e ex -f o l i a t e d . 2 I n a d d i t i o n t o t y p i c a l e p i t h e l i a l c e l ls ,a n u m b e r o f s pe c i al ce ll s a n d s t r u c t u r e s m a y b ep r e s e n t i n f i s h e p i d e r m i s . 1'2 T h e s e i n c l u d em u c u s c e ll s t h a t p r o d u c e t h e t h i n m u c u s c o v -e r i n g f o u n d o n t h e s u r f a c e o f a ll f is h ; a l a r mc e ll s, a l s o k n o w n a s c l u b c el ls , w h i c h p r o d u c e a

w a t e r - so l u b l e s u b s t a n ce ( a p h e r o m o n e ) t h a tw i l l i n i t i a t e a l e r t o r a l a r m r e a c t i o n s i n o t h e r

From the Department of Companion Animal and S pecial Spe-cies Medicine, College of Veterinary Medicine, North CarolinaState U niversity, Raleigh, N C.

Address reprint requests to Gregory A. Lewbart, M S, VMD ,Assistant Professor of Aquatic Anim al M edicine, Department ofCompanion Animal and Special SpeciesMedicine, College of Vet-erinary Medicine, North Carolina State U niversity, Raleigh, N C27606.

Copyright 9 1995 by W.B. Saunders Company1055-937X/95/0404-000355.00/0

f i s h ; n e u r o m a s t c e i l s , w h i c h a r e m u l t i c e l l u l a ro rg a n s o f s e n s e ( ta c t il e , t a s t e , o d o r ) ; c h l o r i d ec e l l s , w h i c h f u n c t i o n i n b l o o d e l e c t r o l y t e e x -c h a n g e ; p i g m e n t c e l l s ; w h i t e b l o o d c e l l s , w h i c hs e r v e a p r o t e c t i v e f u n c t i o n ; a n d s c al e s, x'2

J u s t b e n e a t h t h e e p i d e rm i s , t h e d e r m i s i sc o m p o s e d o f a lo o s e l a y e r a n d a c o m p a c t l a y e ro f c o n n e c t i v e t i s s u e. 1'2 T h e i n n e r p o r t i o n o ft h e d e r m i s c o n t a i n s b l o o d v e s se ls a n d l y m p h a t -ic s th a t n o u r i s h t h e s k i n . l F i s h s c a le s d e v e l o p

w i t h i n t h e d e r m i s f r o m o s t e o g e n i c c e l l s , n o te p i d e r m a l l y a s i n re p t i l e s . B e c a u s e o f t h i s , t h e ya r e n o t s h e d r e g u l a r l y b u t l i e i n p o c k e t s c l o s et o t h e s u r f a c e , a n d w h e n a s c a l e i s l o s t , t h ep o r t i o n o f t h e e p i d e r m i s a t t a c h e d t o t h e f r e es u r f a c e i s l o s t w i t h i t . 2 S c a le r e g e n e r a t i o n o c -c u r s q u i c k l y a n d e f f i c i e n t l y a s l o n g a s t h e o s -t e o g e n i c c e l l r e m a i n s v i a b le . N o t a l l f i s h e s h a v es c al es . C a t f i s h a n d m a n y s p e c i e s o f e el , f o r e x -a m p l e , l a c k sc al es .1 I n m o s t t e le o s t s , t h e d e r m i sa l s o c o n t a i n s p i g m e n t c e l l s ( c h r o m a t o p h o r e s )t h a t o c c u r i n l a y e r s a t d i f f e r e n t l e v e l s. 1'2 T h e

s k i n c o l o r p a t t e r n s a r e p r o d u c e d b y i n t e r a c -t i o n s b e t w e e n t h e s c a l e t y p e s a n d t h e v a r i o u sc h r o m a t o p h o r e s ; h o w e v e r , i n s o m e f i s h , s u c ha s t h e R e d O s c a r , t h e p i g m e n t i s p r i m a r i l y i nt h e e p i d e r m i s . 1

T h e c o l o r o f f i sh is a f f e c t e d b y m a n y n o r m a lp h y s i o lo g i c a n d e n v i r o n m e n t a l f a c t o r s i n c l u d -i n g a g e, d i et , t e m p e r a t u r e , s t re s s, a n d i n s o m ec a s es , s u n l i g h t . 1,2 C o l o r s m a y f a d e t o s o m e e x -t e n t d u r i n g s l ee p. 1 T h e c l in i c ia n m u s t c o n s i d e rt h e s e f a c t s w h e n e v a l u a t i n g a p a t i e n t b e c a u s et h e r e a r e a l s o m a n y c o l o r c h a n g e s a s s o c i a t e d

w i t h d i f f e r e n t d i s e a s e c o n d i t i o n s . W h e n a fi s hb e c o m e s i l l, o n e o f t h e f i r s t s i g n s is a c h a n g e i nc o lo r. U s u a l l y t h e f i s h wi ll b e c o m e d a r k e r d o r -s al ly, b u t a l ac k o f c o l o r o r a n e n h a n c e m e n t o fc o l o r a l s o m a y b e o b s e r v e d . 1.2

C o l o r c h a n g e i s n o t t h e o n l y c l i n i c a ll y s i g n i f -i c a n t w a y i n w h i c h f i s h s k i n r e s p o n d s t o i n s u l t s .I n c re a s es i n m u c u s p r o d u c t i o n m a y o c c u r w i t hp r o t o z o a l i n f e c t i o n s , a n d i n s o m e i n s t a n c e s ,w h e n a n i r r i t a n t i s p r e s e n t i n t h e w a t e r. 1,2 T h em u c u s c o v e r i n g c o n t a i n s a n t i b o d i e s ( I g M ) a n dl y s o s o m e s t h a t a r e a n t i b a c t e r i a l , a n t i f u n g a l ,a n d / o r a n t i p r o t o z o a l . 1'2 U l c e r a t i o n s a r e a l so

2")0 Seminars in Avian and Exot ic Pe t Medic ine , Vol 4 , No 4 (October ), 1 995: p p 220 -233

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Aqu arium Fish Derm atologic Diseases 221

common ly observed on th e skin. They are of-

ten red in the center, white on their edge, andblack on the periphery/ The skin may reactwith proliferative changes, such as hyperplasiaand hypertrophy secondary to protozoan in-fections, or viral-induced papillomas of saltwa-ter fish a nd freshwater fish. 2

Th e skin covers all surfaces of the fish andprotects it from the outside environment. Thecause of death in fish with extensive lesionsof the skin is undoubtedly due to an upsetin electrolyte and osmotic balances in theblood, l'2 In fish with sup erficial woun ds, it is

very importan t to dete rmin e the salinity of thewater in order to interpret the osmotic burdenof the fish.t Evaporation can cause salinity tochange over time, therefo re, it is necessary forthe client to regu larly check the specific gravityof the water in which mari ne fish are kept. 3 Ifulcerations are extensive or acute, hemo rrh agemay also play a role. ̀) Not all skin di seases re-sult in lethal skin lesions, and conversely, notall skin lesions are the result of primary skindisease. I n this r eport , we will discuss the morecommon skin diseases of pet aquarium fish.

Prevention and control are important becauseit is easier to prevent these diseases than totreat them. See Table 1 for some commontreatment protocols.

Diagnostic Techniques

His to ry

The adaptive changes of fish skin and itsreaction to insults are a response to its aquatic

environment. Most fish are constantly im-mersed in water. This is an obvious statementbut one that must be kept in mind when ap-pro achi ng a fish patient, especially a pet aquar-ium fish. The fish has literally no means ofescape from its captive environment. Theyfeed, excrete wastes, reproduce, and most im-porta ntly, r espire in it. As with any sick animal,obtaining a complete and accurate historyfr om the owne r is essential. 4-6 Stos kopf pro-vides an excellent approach to obtaining a ba-sic history. 7 The clinician will want to know

among other things if the client is an experi-enced aquarist, the social structure in theaquarium, the nutritional plan, quarantine

protocol, and previous medical problems or

treatments of the tank. 4-6

Wate r Tes t ing

The initial contact with th e client is likely tobe over the telephon e and some basic problemscan be discussed and potentially solved in thismanner. If necessary, the client should beasked to bring the affected fish and approxi-mately 1 L of water (packed separately) fromthe aquari um into t he veterinary clinic. 6 Thefish-food containers as well as the boxes or, atleast, a written description of the aquariumequipment, such as the heater, filter, and airpump, should be br oug ht in as well. 6 Witho utquestion, the major cause of aquarium fishdisease and mortality is poor water quality.Therefore, once the client has arrived, the cli-nician should finish taking the history and testthe water. 6 Several compr ehens ive articlesdealing with water chemistry and testing are inthe literature and the authors would recom-mend that the reade r refer to those. 4's'9

Sample Collection TechniquesSk in , F in , and G i l l Samples

After the history taking is complete and thewater is evaluated, the fish is examined. Thephysical examination begins with careful ob-servation only; handling the fish should bekept to a minimum. Are the fins frayed? Arethere areas of discoloration or depigmenta-tion? Are there visible ectoparasites, ulcer-ations, or white spots? Is the fish swimming or

breathing abnormally? 5'6 A positive answer toany of these questions indicates that furtherdiagnostics are necessary.

Skin scrapings and routi ne fin and gill biop-sies can usually be performed quickly andwithout anesthesia. An anesthetic agent, suchas tricaine methanesulfonate, may be requiredfor surgical pr ocedu res. 4-6 Th e agen t is pur-chased in a crystalline form and sprinkled intoa container of clean water. 6 After the fish losesits ability to main tain eq uilibr ium it is rem ove dfrom the water, the desired procedures are

performed, and the fish is placed in a "recov-ery" vessel containing clean water and aera-tion. 4 Latex gloves sho uld be worn when hart-

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222 Murphy and Lewbart

Figure 1. Figure 2.

Figure 3. Figure 4.

Figure 5. Figure 6.

Figure 7.Figure 8.

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Aquarium Fish Dermatologic Diseases 2 2 3

d l i n g f is h t o p r e v e n t d a m a g e t o th e p r o t e c t i v e

m u c u s l a y e r .S k i n s c r a p i n g . T h e f i s h i s r e s t r a i n e d m a n -u a l l y o r is s e d a t e d . A c l e a n s c a l p e l o r c o v e r s l ipis t h e n q u i c k l y a p p l i e d t o t h e a r e a o f i n t e r e s ta n d t h e s a m p l e ( i n c l u d i n g s c al es a n d e p i t h e -l i u m ) is t a k e n ) T h e t ai l f i n s h o u l d a lw a y s b ee x a m i n e d b e c a u s e p a r a s i te s t e n d t o a c c u m u -l a te t h e r e . R e m e m b e r t h a t f is h sk i n is v e r y t h i na n d s h o u l d n o t b e s c r a p e d t o b le e d i n g . T h i sp r o c e d u r e is n o t a n a l o g o u s t o s k in s c r a p i n g o fd o g s a n d c a t s . T h e t i s s u e s a m p l e , o n t h e t i p o ft h e s c a l p e l , i s p l a c e d o n a g l a s s s l i d e t h a t c o n -

t a in s s e v e r a l d r o p s o f c l e a n w a t e r ( n o t a q u a r -i u m w a t e r ) . 4 A c o v e r s l i p i s a p p l i e d , a n d t h es p e c i m e n is r e a d y f o r m i c r o s c o p i c e x a m i n a -t i o n .

F i n b i o p s y o r c l i p .A f i n b i o p s y c a n b e e a s i l yp e r f o r m e d o n a n y o f t h e la r g e r f in s , s u c h ast h e t a i l ( c a u d a l f i n ) . A s m a l l p i e c e o f t h e f i n i sr e m o v e d a n d p l a c e d i n a fe w d r o p s o f cl e a nw a t e r o n a m i c r o s c o p e s l id e a n d c o v e r e d w i t h ac o v e r s l i p t o b e e x a m i n e d a s s o o n a s p o s s i b le . 4Tw o o r t h r e e b i o p s i e s c a n b e p l a c e d o n a s i n g l es l ide .

G i l l b i o p s y. R e m o v i n g a p i e c e o f g il l t is s u eis m o r e c o m p l i c a t e d t h a n o b t a i n i n g t h e s k i n o rf i n s a m p l e o w i n g t o t h e i n c r e a s e d r i s k t o t h ep a t i e n t . T h e c l i n i c i a n m u s t b e c a r e f u l t o r e -m o v e o n l y a c o u p l e o f m i l li m e t e rs o f t h e p r i-m a r y g ill l a m e l l a e . 4 T h e r e is u s u a l l y s o m eb l e e d i n g a f t e r t h is , b u t it s h o u l d s u b s i d eq u i ck l y. T h e o p e r c u l u m , o r g i l lp l at e , is d e -f l e c t e d , a n d a f e w m i l l i m e t e r s o f gi ll t i s s u e a r es n i p p e d o f f u s i n g a p a i r o f s h a r p s c is s or s . 4 T h e

g ill s a m p l e is th e n m o u n t e d u s i n g c l ea n w a t e r

a n d a c o v er s li p a n d e x a m i n e d q u ic k ly.H e a l t h y g i ll t is s u e a p p e a r s r e d , a n d t h es m a l l l a m e l l a e a r e d i s t in c t a n d e v e n . 6 P r o t o z o a la n d o t h e r e c t o p a r a s i t e s a r e e a s il y o b s e r v e d i na n y o r a l l t i s s u e . S o m e b a c t e r i a o n t h e t i s s u es h o u l d b e c o n s i d e r e d n o r m a l ; h o w e v e r , a l a r g en u m b e r o f m o t i le b a c t e r ia o n t h e s k in a n d g il lsu s u a l l y i n d i c a t e t h a t a p r o b l e m e x is ts . 6 B e c a u s eg il l b i o p s y i s a r i s k y p r o c e d u r e , i f t h e f i s h i ss m a l l o r a p o o r a n e s t h e t i c r i s k , t h e c l i n i c i a ns h o u l d k e e p i n m i n d t h a t m a n y e c t o p a r a s i t e st h a t a f f e c t g il l t is s u e a r e u s u a l l y f o u n d o n t h e

s k i n a n d f i n s . Tr e a t i n g t h e p a r a s i t e s o n t h es k i n m a y a l s o t a k e c a r e o f t h o s e o n t h e g i ll s. 4G ill d a m a g e c a u s e d b y e n v i r o n m e n t a l p r o b -l e m s c a n o n l y b e e v a l u a t e d a f t e r a g il l b i o p s yh as b e e n p e r f o r m e d . 4

S k i n B i o p s y.U s i n g t h e s a m e a n e s t h e t i c p r o -t o co l a n d p r e c a u t i o n s j u s t m e n t i o n e d , w e d g eb i o p s ie s o f m a s s e s , l u m p s , a n d / o r u l c e r a t i o n sm a y b e p e r f o r m e d . T h e s a m p le is p r e s e r v e d i nf o r m a l i n a n d s u b m i t t e d f o r h i s t o p a th o l o g y .D e p e n d i n g o n t h e e t i o l o g y a n d a b i li ty t o a t ta i na r e p r e s e n t a t i v e s a m p l e , t h e c l in i c i an m a y b e

a b l e t o o b t a i n a d i a g n o s i s o n a li v e f i s h .

S e l e c t e d F i s h S k i n D i s e a s e s

P a r a s i t e sF i s h li ve in a n e n v i r o n m e n t t h a t i s f u l l o f

d i s e as e - c a u si n g o r g a n i s m s a n d p a r a s i t e s 3 W i ldf is h u s u a l l y h a v e a lo w b u r d e n o f a w i d e v a r i -e t y o f p a r a s it e s w h e n t h e y a r e c a p t u r e d , f r e -q u e n t l y w i t h o u t s h o w i n g a n y s i gn s o f d i s e a s e . 10

Figure 1. This H &E s ta ined sect ion throu gh the skin of a s t r iped bass(Morone saxatilis)shows the ce l lu larepide rmis ove r ly ing the dark ly s ta ined bony scale . Th e th in derm is lies benea th the scale. The sandw ichedcon f igu rat ion o f th is sect ion is du e to the fac t because , in most f i shes , the scales over lap o ne an othe r, cre at ing theappea rance o f ep ide rmis ove r l app ing ep ide rmis . (Pho tomic rog raph by Les te r Khoo . )Figure 2 . A s ilver dol lar(Metynnis sp)wi th a seve re case o f " Ich . " No te the n um erou s p inpo in t wh i t e spo t s on thesk in and f in s tha t r ep resen t encys ted t rophon t s o fIchthyopthirius multifiliis.( P h o t o g r a p h b y To d d We n t z el .)Figure 3. This H &E s ta ined sect ion of ca tf ish skin shows an ency sted "Ich" t ropho nt . N ote the lack of scales .( P h o t o m i c r o g r a p h b y L e s t e r K h o o . )Figure 4 . Th i s r ed pacu(Colossoma brachypomum)was a t t acked by a t ankmate wh ich damaged the p ro tec t iveep i the l ium and mucus coa t ing . A secondaryTetrahymenainfect ion caused most of the t i ssue eros ion seen in th ispic ture . This f i sh survived wi th in tens ive ant ib iot ic and sa l t therapy.Figure5. A goldf ish wi th c linica l s igns of bacter ia l f in ro t . Note the f raye d f ins , epi thel ia l necros is , and exp os edbony f in r ays .Figure 6. A koi (Cyprinus ca~pio)with an ulcer typical of those fou nd wi thAeromonas salmonicidainfect ions .Figure 7 . A com mo n go ld f ish(Carassius auratus)wi th an und i ff e ren t i a t ed sa rcoma . Such tumors a re no t un -common in go ld f i sh . Th i s tumor was r emoved su rg ica l ly.Figure8. This f ire ee l(Mastacembelus erythrotaenia)became en t r a ppe d in a sma ll ho le d r i l led in to the s ide o fa PVCpipe she l t e r. A d eep nec ro t i c le s ion r e su l t ed f rom the t r aumat i c even t .

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2 2 4 Murphy and Lewbar t

Parasites derive their living from another or-

ganism, the host, and provide no benefit forthe host. 2 Protozoa, trematodes , and crusta-ceans are am ong the many parasites that infectboth freshwater and marine fishes.

P r o t o z o a

Protozoans are the most ubiquitous para-sites that infect tropical pet fish. They alsocause the most damage. Fortunately they areeasily diagnosed and, in general, are readilytre ated. 10,t 1

I c h t h y o p h t h i r i u s m u l t i f i l i i s / C r y p t o c a r y o n i r -r i t an s . Ich thyophth i r ius mul t i fi l ii s ,a ciliate, is themost familiar protozo an to aquarists an d clini-cians. It is the cause of "Ich" and affects mostfreshwater fish species worldwide. Underaquarium conditions it is very virulent3 1 m u l -tifiliis has a simple life cycle that involves onetrue host, the fish. The the ront matures in theskin of the fish and becomes a trophont. Thelarge trophont (visible as small whitish-graynodules on the skin and gills [Fig 2]) breaksthrough the epithelium of the host and falls to

the bottom of the aquarium. It is now called atomont. The tomont undergoes mitosis, which,with in 18 to 21 h ours at 23 to 25 ~ C, pr odu ceshu ndr eds of ciliated, infective tomites. Th e in-fective tomites, once released into the water,are referred to as theronts. They must find afish host within 2 to 3 days of" release or thetheront s will die. Once an infective the ron t at-taches and actively penetrates the skin and/orgill epithelium of the fish, it develops into areproductive trophont, completing the life cy-cle (Fig 3). Th e entir e "Ich " life cycle takes be-

tween 2 to 4 weeks, depending on the watertemp era tur e. 1'2'1~ It is imp ort ant to notethat the infective theronts may become at-tached to plants or other debris for a day ortwo, thus, the aquarium decor may act as adisease vector when moved from one tank toanother without a period of quarantine.21

The predominant signs of the disease in-clude small white spots over the body and/orgills. Diagnosis is con fir med by microscopic ex-amination of skin scrapings and/or fin and gillbiopsies. The theronts are large, may appear

round to oval, and move across the field ofview in a rolling motion. A characteristic cres-cent-shaped nucleus is often visible. 1'2'11 1 m u l -

tifiliis is one of the few fish parasites with cilia

sur rou ndi ng the entire organism. 1,9Eradication of I mult i f i l i isis possible onlyduring the free-swimming infective stages,since medications cannot penetrate to the en-cysted ther onts . 1'2'1~ Malachite gre en, for-malin, and malachite green-formalin mixtureshave all been used to treat fre shw ater fish. 11Com mon salt was successfully used to tr eat ex-perimentally induced I mul t i f i l i i sin warm-water fishes. 12 In additio n to c hemot hera py,managemen t adjustments also help to controlinfestations. Elevating the water temperature

to several degrees above normal for 5 to 7 dayswill limit the infection by adversely affectingthe heat-sensitive theronts, accelerating theparasite's life, and enhancing the immune sys-tem of the ho st . 1'2'11 However, attention mustbe paid to temperature and pH regulation toavoid stressing the fish. 9 Heav y fil trat ion withdiatomaceous earth filters will also decreasethe numb er of circulating theronts. 1'2 A thir dmana geme nt strategy is to transfer the fish to aclean "hospital" aquarium every day for 7 days,limiting reinfection by the theronts. 1'2 In home

aquaria where the medicants may harm plants,removal of theronts can be achieved by makin gheavy water changes daily or, alternatively, thefish may be treated in a separate aquariumequipped with a heater and filter. The proto-zoa in the main aquarium will eventually dieowing to lack of a host. 1,2 To be ab solutely s urethat the theronts are eliminated, have the cli-ent make at least one complete water change,along with removing debris from the gravel,and elevate the temperature several degreesabove normal before returning the fish to the

main aqu ari um. 1'2Cryptocaryon i rr i tansis the counterpart to Imult i f i l i isin saltwater fish and is often called"marine ich" or "crypto." The predominantsigns of the disease in marine fish also includeswhitish-gray noduies on the skin and/or gills,as well as fusion of the gill lamellae, epithelialhyperplasia, hemorrhages, and lesions of sec-ond ary bacterial infection. 1'5 The tro pho nts(feeding stage) burrow vigorously into the ep-ithelium causing extreme irritation. The resultis scratching or flashing, excess mucus produc-

tion, and an increased respiratory rate. 2,5 Thelife cycle of C # , i t a n sis similar to that of I m u l -tifiliis,and the treat ment methodolog y is iden-

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226 Murphy and Lewbart

t o c o l o n i z e n o t o n l y t h e s k i n a n d g i ll s, b u t a l s o

t h e i n t e s t i n e . 1 '2 '11 T h i s d i s e a s e i s c o m m o n i nm a r i n e a n d f r e s h w a t e r a q u a r i a .C h i l o d o n e l l a c y p r i n i / B r o o k l y n e U a h o s t i l i s .

U n l i k e t h e p r e v i o u s p r o t o z o a n s d i s c u s s e d ,t h e re i s n o c o m m o n n a m e f o rChi lodonel lacyprinii n f ec t i on s . I t is a n u n c o m m o n p r o b l e mi n t h e h o m e a q u a r i u m b e c a u s e t h e i n f e s t a t i o nw o u l d i n i ti a ll y b e e n c o u n t e r e d a t th e w h o l e s a l ea n d r e t a i l le v e l , w h e r e i t i s a s e v e r e a n d c o m -m o n p r o b l e m o f f r e s h w a t e r f is h e s. 1"2 Ve r yh i g h m o r b i d i t y a n d m o r t a l i ty m a y o c c u r u n d e rs t r es s f u l, c r o w d e d a q u a r i u m c o n d i t i o n s . 11 T h e

p r i n c i p l e s i g n s o fC cyprinia r e r e s p i r a t o r y d i s -t re s s , c l a m p e d f i n s, d e p r e s s i o n , a n d e x c es s iv em u c u s p r o d u c t i o n . 1'2 S k i n s c r a p i n g s a n d g il lb i o p s y s a m p l e s s h o w a n o v a l , f l a t t e n e d c i l i a t ew i t h a s h a p e s u g g e s t iv e o f a v a l e n t i n e h e a r t ,w h i c h m o v e s i n a c h a r a c t e r i s t i c a l l y s l o w c i r c u -l a r f a s h i o n , a'2 '11 W e t m o u n t s m u s t b e e x a m -i n e d i m m e d i a t e l y b e c a u s e t h e p a r a s it e d i e sq u i c k l y o n a m i c r o s c o p e s l id e . 1,11ChilodoneUaiss u s c e p ti b l e t o c o m m o n l y u s e d p a r a s i t ic i d e s o r0 . 3 % s a l t a d d e d t o w a t e r. B o t h t r e a t m e n t r e g -i m e n s w i l l k i l l t h e p a r a s i t e s o n t h e f i s h a s w e l l

as in the wa t e r. 1 '2AIBrooklynella host i l isi s a h i g h l y l e t h a l Chil-odonella-likeo b l i g a t e p a r a s i t e o n t h e g i ll s a n ds k i n o f m a r i n e f is h . It a p p e a r s t o b e m o r e c o m -m o n i n h o m e a q u a r i a t h a n i ts f r e s h w a t e r c o u n -t e r p a r t , a l t h o u g h s t r e s s f u l , c r o w d e d c o n d i t i o n sa r e a ls o i m p o r t a n t i n t h e p a t h o g e n e s i s o f Bhos-tilis.C l o w n f i s h a n d s e a h o r s e s a p p e a r t o b e p a r-t i c u l a r l y s u s c e p t i b l e a n d e x h i b i t c l i n i ca l s ig n s a sp r e v i o u s l y m e n t i o n e d . 2 B o d y l e s i o n s b e g i n a ss m a l l , d i f f u s e , d i s c o l o r e d f o c i t h a t i n v o l v e al a rg e p o r t i o n o f t h e f i s h 's b o d y. 2 A s t h e d i s e a s e

a d v a n c e s , m a s s i v e h e m o r r h a g e a n d e p i t h e l i a ls l o u g h i n g o c c u r s . 1'2 D e a t h i s l i k e ly c a u s e d b yt h e lo ss o f e p i t h e l i u m a n d s u b s e q u e n t i m -p a i r e d o s m o r e g u l a t o r y c a p ab i li t i e s o f t hefis h. 1'2'5 D i a g no s i s is m a d e b y w e t m o u n t e x -a m i n a t i o n o f f is h a n d / o r g i ll s m e a r s . T h e c ili -a t e s a r e b e a n - t o h e a r t - s h a p e d a n d g l i d e o nt h e i r v e n t r a l s u r f a c e . 1'2 T h e y c o n t a i n a n o v a lm a c r o n u c l e u s , s e v e r a l m i c r o n u c l e i , a n d m u l t i -p i e f o o d v a c u o l e s. 2B hostilisis r e s i s t a n t t o c o p -p e r m e d i c a n t s , t h e r e f o r e , a c o m b i n a t i o n o fm a l a c h i te g r e e n a n d f o r m a l i n is r e c o m m e n d e d

f o r t r e a t m e n t . 1 '2 '5 I n m o s t c a se s , a n t i b a c t e r i a lt h e r a p y a l s o i s n e c e s s a r y t o c o n t r o l s e c o n d a r yt o p i c a l o r s y s t e m i c b a c t e r i a l i n f e c t i o n s . 2

Epi s ty l i s . Ep i s ty l i ss p e c i e s (He te ropo la r i a

colisarum)a r e s t a l k e d c i l i a t e d p r o t o z o a n s t h a tp a r a si t iz e f r e s h w a t e r t r o p i c a l f is h . T h e r e is n ok n o w n m a r i n e c o u n t e r p a r t . N o r m a l l yEpistylisa r e n o n p a t h o g e n i c a n d a r e f o u n d a t t a c h e d t ov e g e t a t i o n a n d c r u s t a c e a n s i n t h e a q u a r -i u m . 1& 11 H o w e v e r , i f th e a q u a r i u m i s h i g h i no r g a n i c m a t t e r , t h e y w i l l p r o l i f e r a t e a n d t a k ea d v a n t a g e o f s t r e s s ed o r d e b i l i t a te d f i s h . T h e s ep r o t o z o a n s a r e m o s t f r e q u e n t l y o b s e r v e d o ng o l d f i s h as w e ll a s b o t t o m - d w e l l i n g o r n a m e n t a lca t f i sh . 1 '2 '11 Gro ss l e s ions ap pe ar a s a wh i tea r e a o r w h i t e t u f t ( r e s e m b l i n g f u n g a l i n f e c t i o n )

o n t h e s u r f a c e o f t h e f i s h b o d y a n d / o r f in s .Epistylish a v e a l s o b e e n i s o l a te d i n u l c e r a t e d a r -e a s f r o m w h i c hAeromonas hydrophilah a s b e e nc u l t u r e d . I t i s u n k n o w n w h i c h o r g a n i s m i n i t i -a t e d th e p rob lem . I '2 '11

D i a g n os i s is c o n f i r m e d b y m a k i n g w e tm o u n t p r e p a r a t i o n s f r o m t h e a f f e c t e d ar ea s .C h a r a c t e r i s t i c b e l l - s h a p e d c i l i a t e d o r g a n i s m s ,w h i c h p e r i o d i c a l l y c o n t r a c t f r o m a n e l o n g a t e df o r m t o a b a l l - s h a p e f o r m , a r e o b s e r v e d . 1'2'11Epistylisa r e e a si ly t r e a t e d w i t h s t a n d a r d p a r a -s i t i c i d e s o r b y s w a b b i n g t h e a f f e c t e d a r e a s w i t h

t i n c t u r e o f i o d i n e o r a p o v i d o n e i o d i n e s o lu -t i o n . H o w e v e r , t h e p r o b l e m c a n b e e a si l ya v o i d e d b y r e g u l a r c l e a n i n g o f g r a v el a n d c a re -f u l fe e d i n g t o m i n i m i z e t h e b u i l d u p o f o r g a n i cm at te r. 1,2,11

Monogenet ic TrematodesM o n o g e n e t i c t r e m a t o d e s o r f l a t w o r m s a r e

c o m m o n p a r a s i t e s o f t h e g i ll s , f i n s , a n d s k ir l o f"b o t h f r e s h w a t e r a n d s a l t w a t e r a q u a r i u m f i s h e s .T h e y f e e d o n m u c u s , s k in , a n d s o m e t i m e sb l o o d . T h e m o s t d a m a g i n g a s p e c t t o th e f i s h i s

t h e h a p t o r , o r a t t a c h m e n t o r g a n , w h i c h b e a r st w o l a r ge c e n t r a l l y p la c e d h o o k s a n d a n a s so r t-m e n t o f u p t o 1 6 s u r r o u n d i n g h o o k l e t s . 1 '2 '5 '1 ~

Dac ty logyrus /Gyrodac ty lus .Tw o m a i n f a m -i li es p a r a s it i z e b o t h f r e s h w a t e r a n d m a r i n et r o p i c a l f i s h ,Dactylogyridae(g i l l f lukes ) and Gy-rodactylidae( s k i n f l u k e s ) . O v e r c r o w d i n g a n dp o o r h u s b a n d r y a r e o f t e n a s s o c i a t e d w i t h a ne p i z o o t i c o c c u r r e n c e o f t h e s e p a r a s i t e s . 1.9,10 O ft h e m a n y g e n e r a ,Dactylogyrusi s t h e m o s t i m -p o r t a n t . I t is a s s o c i a t e d p r i m a r i l y w i t h t h e g i l ls ,c a u s i n g h y p e r p l a s i a , d e s t r u c t i o n o f t h e g il l e p -

i t h e l i u m , a n d c l u b b i n g o f g il l f i l a m e n t s , r e s u l t-i n g i n a s p h y x i a t i o n . 1'2Gyrodactylusa l s o c o m -m o n l y i n f e ct s a q u a r i u m f i s h a n d is as s o c i a te d

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Aquarium Fish D ermatologic Diseases 2 2 7

m a i n l y w i t h t h e s k in , a l t h o u g h t h e f i n s a n d g il ls

m a y b e in v o l v e d a s w e ll . I n a p p a r e n tGyrodacty-/ us i n f e c t i o n s o c c u r . W h e n l e s i o n s a r e p r e s e n t ,t h e y m a y i n c lu d e l o c a l iz e d h e m o r r h a g i c a r e a s ,e x c e s si v e m u c u s p r o d u c t i o n , a n d l o c al i ze d u l-c e r a t i o n s . 1'2 T h e a f f e c t e d f is h o f t e n h a v e ar a g g e d - a p p e a r i n g ta il f r o m l o ca li z ed h y p e r p l a -s ia , n e c r o s i s o f t h e t i p s o f t h e f i n s, a n d l o ss o fe p i t h e l i a l c e ll s . 1 ,9 ,1 0 S e c o n d a r y b a c t e r i a l i n f e c -t io n s ar e c o m m o n . T h e b e h a v i o r o f a ff e c t e df is h ra n g e s f r o m f l a sh i n g o r r u b b i n g t o b e c o m -i n g i n a c ti v e a t t h e b o t t o m o f t h e a q u a r i u m .R a p i d r e s p i r a t o r y m o v e m e n t s a l so m a y b e o b -

se r ve d . 1 ,9

Ta b l e 1 . Tr e a t m e n t Ta b l e

T h e d i a g n o s i s o f b o t h g e n e r a i n v o l v e s s k in

s c r a p i n g s , f i n , a n d / o r g i ll b i o p s i e s ; t h e w o r m sa r e r e a d il y a p p a r e n t . l '2 T r e a t m e n t c o ns is ts o ft h e c o m m o n p a r a si t ic i d e s , o r s a l t w a t e r b a t h sf o r f r e s h w a t e r f i sh a n d f r e s h w a t e r b a t h s f o rs a l t w a t e r fi sh . R e s i s t a n c e p r o b l e m s h a v e d e v e l -o p e d w i th t h e o v e r u s e o f o r g a n o p h o s p h a t e s ,b u t p r a z i q u a n t e l ( as a b a t h o r i m m e r s i o n ) h a sb e e n u s e d s u c c e s s f u l l y t o t r e a t g y r o d a c t y l i dt r e m a t o d e s . 1,2

Neobenedenia meUini . M a n y s p ec ie s o f m a -r i n e t r o p i c a l f i s h a r e a l s o s u s c e p t i b l e t o t h em o n o g e n e t i c t r e m a t o d eNeobenedenia mellini

(Epibdella mellini).U n d e r a q u a r i u m c o n d i t i o n s ,

Agent Dosage and Treatment Comments (Indications, Concerns)

Ace t i c ac id (G lac ia l ) D ip t r ea tm en t o f 2 mL /L o f Ec topa ra s i te s .wa ter for 30 to 45 May ki ll smal l or debi l i ta ted f i sh .seconds .

0 .18 to 0 .22 mg/L for 14 to21 days .

C o p p e r s u l f a t e

E n r o f l o x a c i n

F o r m a l d e h y d e ( 3 7 % )

Malach i t e g r een

P o v i d o n e - i o d i n e p r e p a r a t i o n

Praz iquan te l

Q u i n i n e h y d r o c h l o r i d e

S i lvadene (Mar ion , Kansas C i ty,M O )

Sod ium ch lo r ide (3 .0%)

T r i m e t h o p r i ms u l f a m e t h o x a z o l e

Ba th o f 2 .5 m g /L o f wa te rfo r 5 hou r s , r epea t a snecessary.

B a t h t r e a t m e n t o f 2 0 t o 25p p m f o r 1 2 t o 24 h o u r s o rI 0 0 t o 2 5 0 p p m f o r 3 0minu te s t o t hou r.

B a t h t r e a t m e n t o f0. 1 to0 .15 ppm fo r 12 t o 24hour s , r epea t a s neces sa ry.

1:10 dilution, topically.

Ba th o f 5 t o 10 mg /L fo r 3to 6 hou r s , r epea t w i th30% to 70% wa te r changesbe tween ba th s .

Use 10 t o 20 ppm as aninde f in i t e t ank t r ea tmen t .

D e c o m p o s e s o v e r t im e .

Apply topica l ly, twice da i ly,a s n e e d e d .

100% seawa te r d ip fo r 5minu te s o r l onge r,d e p e n d i n g o n t heto l e r ance by t he f ish .

B a t h o f 9 6 0 m g / 3 8 L o fwa te r fo r 3 t o 6 hou r s ,r e p e a t a s n e e d e d .

External c i l ia tes , d inof lagel la tes ,s o m e m o n o g e n e a o f m a r i n efish.

To x i c i t y, d e c r e a s e d i m m u n efunc t ion .

M a n y g r a m - n e g a t i v e b a c t e r ia .

Ex te rna l f unga l and pa ra s i t i cin f ec t i ons . Ca rc inogen ic , hand lewi th ca r e . Wa te r mus t be we l lae r a t ed , and f i sh mus t be c lo se lym o n i t o r e d .

Most ec toparas i tes , especia l ly" I ch . " May use i n combina t ionw i t h 2 0 p p m f o r m a l d e h y d e .M a y r e p e a t t r e a t m e n t n e x t d a ya f t e r 30% wa te r change .

Loca l i zed funga l i n f ec ti on .Po ten t i a l t ox ic i ty, may bu rn sk in .

S o m e M o n o g e n e a .May cause cen t r a l ne rvous sys t em

dys func t ion ( t e rmina t e d ip ) .

Oodiniumand tomi t e s t ages o f" Ida . "

Some spec i e s o f f i sh may besens i t ive , tes t before use .

Bacter ia l infec t ions .

Wo r k s o n l y o n f r e s h w a t e r f is h .Mar ine f i sh may be t r ea t eds imi la r ly i n a f r e sh w a te r d ip fo r5 minu te s i f t hey t o l e r a t e i t .

Bac t e r i a l in f ec t ions . Tr ea t un t i ls i gns o f d i s ea se a r e gon e .

Safe for most f i sh species .

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2 2 8 Murphy and Lewbart

it parasitizes the skin and gills of saltwa ter fish.

The fish show signs of respiratory distress, ir-ritation (frequent scratching on objects), andthe bod y color pales. 1'2'5 Mechanical d ama geand ulceration of the skin leads to secondarybacterial infecti ons. 1'2 The diagnosis is con-firmed by observation of the worms in wetmount preparations of skin scrapings and gillbiopsies. F resh wate r dips will effectively con-trol N mellini, although organophosphates,praziquantel, and formalin have also beenused. 1,2,5

C r u s t a c e a n s

L e r n a e a . Copepods of the genus Lernaeaare easily recognized crustacean parasites ofthe fish skin. Th ey are not host specific but areparticularly commo n in goldfish. 2 They arecommonly called "anchorworms" because thefemale anchors herself to the fish by burrow-ing into the dermis with her head. The femalealso has a wormlike appearance and, at hermaxi mum len gth, a characteristic V shape ow-ing to the two eggs sacs that pro tru de fro m thefree e nd of her body. 1,2 Irr itat ion an d localized

hemo rrha gic reactions occur at the point of en-try of the anchorworm. These areas may de-velop into ulcerations and then fibrous nod-ules, as well as allow for secondary bacterial orfun gal infections.l'2'10 Th e parasite is easily di-agnosed on physical examination of the af-fected fish. Treatment involves dipping thefreshw ater fish into a saltwater aqua rium for 5to 10 minutes per day. The anchorworms willeventually turn a greenish color, wither, andbe expelled fro m the fish. 2 If only a few fishare involved, the worms may be removed using

forceps, t akin g care not to break the wo rm. 1,2Juvenile forms must also be eliminated fromthe water using organophosphates or formalinwith successive water changes. Antibiotic treat-men t may also be necessary. 1.2

A rg u l u s . Another external crustacean thataffects aquarium fish is Argulus, the fish louse.This large parasite can be easily seen with thenaked eye moving along the surface of bothfreshw ater and marine tropical fish. 1'2'I~ Thefish louse uses both suction cups and a pair ofcurved hooks to attach to the fish, inserts its

proboscis into the epidermis and underlyingtissues, and feeds by injecting cytolytic toxinth ro ug h the stiletto. 1'2 Severe local reactions

are apparent aroun d the area of the sting. Ul-

cerations often develop and are believed to bethe result of secondary bacterial infections(Aeromonas, Pseudomonas). 1,2,10The wounds arealso frequently infected with fungi.l'2 The af-fected fish will be observed to scratch repeat-edly on the aquarium bottom or any availableobject. 1'2'1~ Diagnosis is m ade by ex ami ni ngthe live fish for the small, dorsoventrally flat-tened parasite. Argu lus is transparent andtends to take on the color of the fish it is par-asitizing. Both organophosphate and formalintreatments may be successful, althou gh antibi-

otic therapy may also be required. 1,2

B a c t e r i a

The billions of bacteria contained in an es-tablished aquarium can be divided into threemain groups. The first, and largest propor-tion, are normal flora. They live benignly inthe environment and include a group of bac-teria responsible for the decomposition ofwastes (nitr ifyin g bacteria). 2 The secondgroup, opportunistic bacteria, can cause dis-

ease under a given set of conditions. This usu-ally involves some factor in the aquatic envi-ronment that weakens the fish, compromisingits immune system and rendering it open tosuccessful bacterial attack. 2 The thi rd, andsmallest group, are the primary pathogens,which are only occasionally present. These mi-croorganisms have the ability to cause diseasein normal healthy fish. 2 Because prima rypathogens are seldom encountered in fish cul-ture, most bacterial disease programs centeron controlling the opportunists, and more im-

portantly, maintaining the inherent immunityof the fish. 2The physical signs associated with bacterial

infections include hemorrhages, ulcerations,and skin and fin erosions (Fig 5). Hemor-rhages are common and may vary from pete-chiae (pinpoint) to ecchymotic (paintbrushlikered den ed areas). 2 Ulcers are distinct, oft en cir-cumscribed areas of skin where a ring of red-dened tissue surrounds a central core of deadtissue. Erosions appear as white areas and areusually caused by a bacterial enzyme that de-

stroys the tissue (Fig 6). 2 Th e tentativ e diag no-sis of a bacterial prob lem shou ld always be pre-ceded by attempts to identify stress factors that

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Aquarium Fish Dermatologic Diseases 2 2 9

may have weakened the fish. These include

poor water quality, long transport time, poornutrition, or the presence of a concomitantparasitic infection. 2'9 When an etiologic diag-nosis is necessary, a sterile sample is best col-lected from the kidney for microbiological cul-ture. Skin lesions may be cultured, but the re-sults are often misleading owing to mixedculture results, including no npatho gens. 9 Mostbacterial pathogens of tropical fish are gram-negative rods and include the genera Aeromo-nas, Pseudomonas, Vibrio,and F lexiba cter. 1'2'5'9"1~

Aero mo nas hydrophila . Aeromonas hydrophila

is a common cause of bacterial infection in thefish. It is an opportunistic pathogen with dis-ease outbreaks after a period of stress and/orinfestation with parasites that provide a routeof entry.l'2 Early lesions may include petechialand ecchymotic hemorrha ges in and aroun dthe gills and anus, at the base of fins, andwithin the mouth. In advanced cases, the le-sions dev elo p into larg e ulcers. ~'2'1~ A cyto-toxin produced by A hydrophilais believed toplay a role in th e p athogen esis o f the disease. 13Tre atm ent involves the use of antibiotics; how-

ever, resistance does develop easily in A hydro-phila strains. 1'2 Th er e are r eport s that fluoro-quinolones are an effective treatment of thismicroorganism.14 A commercial bacteri n is notyet available. Problems related to A hydrophitaare rare in well-managed home aquaria wherefish are fed a well-balanced diet.l'z

Pseu dom ona s f luorescens. Pseudomonas f luo-rescens is a dominant, normal inhabitant ofboth freshwater and marine aquaria. All spe-cies of aquarium fish are susceptible to this op-portunistic pathogen and, in all cases, infec-

tions are believed to be related to stress/Theclinical signs are identical to those associatedwith other bacterial infections. They rangefrom fin and body ulcers to erosions. The tis-sues surrounding the ulcers are not usuallyhemorrhagic, although petechiae and ecchy-moses may be present elsewhere on thebody. 1'2 This diffe rs fr om the ulcerative le-sions related to A hydrophilainfections. Amaz-ingly, affected fish may contin ue to eat, despiteextensive lesions, including exposed skeletalstructures. 1 Death does occur in peracute and

severely advanced cases. 1'2 Treatment is diffi-cult because several Pseudomonasstrains are re-sistant to many antimicrobial drugs. 2 Altho ugh

fluoroquinolones have been reported to be ef-

fective against a numb er of bacterial fish path-ogens, we are unaware of its efficacy againstfish Pseudomonas specifically. 14 No bacte rinsare available ibr this disease.

Vibrio. Vibriois the most common and se-rious bacterial infection of saltwater fish. Al-thou gh all freshwater and saltwater fish speciesare considered susceptible, it is more likely tobe found in the marine environment.~'2'5 It isan opportunistic pathogen with infections oc-cur rin g in fish after perio ds of stress, 2'5 espe-cially when the tank water becomes warm and

dissolved oxyge n is decreased . 1 Th e typical ex-ternal lesions include eryt hema an d bloody in-fection of the mouth, vent, and at the base ofthe fins; red necrotic lesions of the abdomen;ulcerations; and fin and body erosions, l'2'aThe necrotic lesions may extend into the mus-culature as the disease progresses, resulting ina loss of body fluids. 5 The affe cted f ish rarelyeat and are lethargic and depressed.1 Chemo-therapeutic options are limited because of theusual loss of appetite, although some antibiot-ics may be injected into larger fish or a dde d to

the aqu ariu m water. ~'2 An effective commer -cial vaccine is available but is mainly used forfoo d-p rod uci ng species. 2'5 In a well- manag edsaltwater aquarium wh ere fish are kept in goo dnutrition and good water, vibriosis is rare.l'z

Flexibaeter eolumnaris . In contrast to thepreviously discussed bacteria, Flexibacter colum-naris (Cytophaga columnaris)may be considereda prim ary patho gen of fish. 2"~~ t p roduces theenzyme chronditinase and is capable of initi-ating a disease known as columnaris diseasein healthy fish. 2 The marine count erpart is

known as Flexibacter maritimus.The skin infec-tion is characterized by blanched, necrotic le-sions of the body, the most distinctive of whichis a saddlelike marking behind the dorsal fin.The fins and tail of some affec ted fish will de-velop whitish areas and split. Th e gills may alsodisplay necrotic ulcers. 2'1~ Unlike the previou sthree bacterial pathogens, internal involve-ment is uncommon with Flexibacterinfections,although concurrent infections with other bac-teria, such as Aeromonas, may occur, z W henlesions are observed on the fish, antibiotics

should be used immediately. Flexibacteris con-sidered a primary pathogen, but environmen-tal stresses do appear to play somewhat of a

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230 Murphy and Lewbart

r o l e in t h e d i s e a s e p r o c e s s. I n a q u a r i u m f is h , i t

i s o f t e n o b s e r v e d i m m e d i a t e l y a f t e r s h i p p i n g ,a n d i n w e l l - m a n a g e d h o m e a q u a r i a , i t is a n u n -c o m m o n d i se a s e. ~ C o l u m n a r i s d i se a s e c a n b ec o n t r o l le d t h r o u g h t h e r e d u c t i o n o f e n v i r o n -m e n t a l b a c t e r i a b y m i n i m i zi n g t h e a m o u n t o fo rg a n i c m a t t e r i n t h e a q u a r i u m . N o v a c c i n e i sava i lab le fo r th i s d i sease . 2

FungusSaprolegnia

T h e m o s t c o m m o n l y i d e n ti f ie d f u n g a l p a t h -

o g e n s a re m e m b e r s o f t heSaproleg~ziag e n e r a .T h e y a r e u b i q u i t o u s w a t e r m o l d s f o u n d i nb o t h f r e s h w a t e r a n d s a l t w a t e r , a l t h o u g h t h e ya r e p r i m a r i l y a f r e s h w a t e r p r o b l e m . 1.2,10 T h e i rg r o w t h is f a v o r e d b y m o d e r a t e l y a c i d ic p H , l o wt e m p e r a t u r e s , a n d t h e p r e s e n c e o f d e c a y i n gorga n ic m ate r ia l . 1 '1~Saprolegniaf u n g i r a r e l yp e n e t r a t e d e e p l y i n t o m u s c l e b u t i n s te a ds p r e a d m a i n l y a l o n g th e s u r f a c e o f th e b o d y.B y c o n t r a s t , h y p h a e g r o w r a p i d l y i n to d e a d ,exc i sed f i sh t i s sue . 1 ,15 This sugges t s tha t po ten td e f e n s e s n o r m a l l y p r e v e n t d e e p i n v a si o n . 1~

Funga l d i sease in f i sh i s near ly a lways second-a r y t o a b r e a k i n t h e i n t e g r i t y o f th e e p i d e r m i sa n d a s s o c i a t e d m u c u s c o a t in g . 9 M u c u s is c o n -s i d e r e d a n i m p o r t a n t b a r r i e r t o o o m y c e t e c ol-o n i z a t io n . T h e m a j o r i t y o fSaprole~ia s p o r e st h a t l a n d o n h e a l t h y f i s h s k i n a r e q u i c k l ys l o u g h e d o r d i e . 1 5 Va r i o u s f o r m s o f s t r e s s i n -c l u d i n g t r a n s p o r t , h a n d l i n g , p o o r w a t e r q u a l -i ty ( e s p e ci a ll y i n c r e a s e d o rg a n i c m a t t e r a n d d e -c r e a s e d t e m p e r a t u r e ) , a n d p o o r n u tr i t io n a r ec o n s i d e r e d n e c e s s a r y i n t h e d e v e l o p m e n t o fw a t e r m o l d i n f e c t i o n s i nfish. 1'2'15

The typ ica l c l in ica l appearance i s whi te co t -t o n li k e g r o w t h s r a n d o m l y d i s t r i b u te d o v e r t h es u r f a c e o f t h e s k i n a n d g ills . T h e c o t t o n y a p -p e a r a n c e is o n l y p r e s e n t w h e n t h e f i s h is i n t h ew a t e r. O n c e t h e f is h is r e m o v e d f r o m t h e w a -t e r, t h e m a s s c o l l a p s e s r e s e m b l i n g a b a l l o f w e tc o t t o n . 1,2 F o c a l e p i d e r m a l e r o s i o n s m a y b e e v -i d e n t a n d a r e d i r e c t l y r e l a t e d t o t is s u e n e c r o s isi n t h e a r e a o f t h e h y p h a e . 1 A ff e c t e d ' f i sh w i llb e c o m e a n o r e c t i c a n d i n a c t iv e . 1~ D e a t h isc a u s e d b y i m p a i r e d o s m o r e g u l a t i o n a n d t h ef i s h ' s i n a b i l i t y t o m a i n t a i n b o d y f l u i d b a l -

a n c e . 1'2 T h e d i a g n o s i s is r e a d i l y m a d e w i t hq u i c k sk i n s c r a p e a n d e x a m i n a t i o n o f t h e w e tm o u n t p r e p a r a t i o n . I f t h e i n f e c ti o n is n o t s e-

v e r e , m a n y f i s h w i l l h e a l w i t h s u p p o r t i v e c a r e

( g o o d n u t r i t i o n a n d c l e a n w a t e r ) . 9 S e v e r a l c h e -m o t h e r a p e u t i c o p t i o n s a r e a v a i l a b l e i n c l u d i n gc o p p e r s u l fa t e , m a l a c h it e g r e e n , f o r m a l d e -h y d e , a n d s o d i u m c h l o r i d e b a t h s , a m o n g o t h -e rs . l ' 2 '9 In genera l , an es tab l i shed funga l in fec -t i o n is d i f f i c u lt to t re a t . M a n a g e m e n t p r a c t i c e sm u s t b e i m p r o v e d , a n d t h e o t h e r p a t h o g e n sp r e s e n t m u s t a l so b e a d d r e s s e d . 1.2

I ch thyophonus ho fe r iR e p o r t s o f f u n g a l d i s e a s e in m a r i n e f i s h a r e

s p o r a d i c w i t h th e e x c e p t i o noflchthyophonus ho-feri d i s e a se ( s a n d p a p e r d i se a s e ). 1 F i s h b e c o m ei n f e c t e d a f t e r e a t i n g f o o d c o n t a i n i n g v i a b le Ihoferispores . 1'5 Th e ex te rna l l e s ions m ay in -c l u d e s k i n d i s c o l o r a t i o n a n d m u l t i p l e w h i t ep a p u | e s . I n f i n e - s c a l e d s p e c ie s o f f is h , a r o u g h ,g r a n u l a r a p p e a r a n c e o f th e s k in m a y b e e v i-d e n t c a u s e d b y m u l ti p le s u b c u t a n e o u s g r a n u -l o m a s . S o m e f i s h w i l l d e v e l o p a d a r k c o l o r i nt h e l a t e r a l l i n e t h a t p r o g r e s s e s t o c o m p l e t ed a r k e n i n g . l ' 5 V i s u a li z a ti o n o f g r a n u l o m a s c o n -t a i n in g r o u n d a n d e l li p ti c c ys ts i n a w e t m o u n tp r e p a r a t i o n w i ll c o n f i r m t h e d i a g n o s i s . 5 T h e r eis n o c h e m o t h e r a p e u ti c r e g i m e n d o c u m e n t e dfor th i s d i sease , and the u se o f sys temic an t i-f u n g a l d r u g s i s e x p e r i m e n t a l . P r e v e n t i o n i n -c l u d e s e l i m i n a t i n g f r e s h f i s h f r o m t h e d i e t a n dr e m o v i n g d e a d a n d d y i n g fi sh f r o m t h e a q u a r -iu m . 1,5

NeoplasiaM o r e t h a n 5 0 b a s ic t y p e s o f t u m o r s , r a n g i n g

f r o m b e n i g n e p i d e r m a l p a p i l l o m a s t o m e t a -s ta ti c m e l a n o m a s , h a v e b e e n r e g i s t e r e d i nm o r e t h a n 3 0 0 s p e ci e s o f fi sh . Tu m o r s o f th e

s k in a c c o u n t f o r a l m o s t 5 0 % o f t h e s e , h o w e v e r,t h e o v e r w h e l m i n g m a j o r it y o f th e s e o c c u r i nw i ld f i sh . 16 O t h e r t h a n t u m o r s o f g o l d f i s h ( F ig7 ), w h i c h a r e w e l l r e p r e s e n t e d i n th e l i t e r a t u r e ,f e w tu m o r s a r e r e p o r t e d i n t r o pi c a l fr e s h w a t e ror ma r ine f ish. l' 2'17 O f the na tu ra l ly oc cu r r in gf is h tu m o r s , b e n i g n e p i d e r m a l h y p e r p l a s i a a n dp a p i l l o m a s a r e t h e m o s t f r e q u e n t l y o b s e r v e d . 1 6T h e c a u se s o f fi sh s ki n t u m o r d e v e l o p m e n t a r ev a r i e d a n d s u s p e c t e d t o b e m u l t i f a c t o r i a l .T h e r e is s o m e e v i d e n c e t h a t i r r i t a ti o n o f t h es k in c a u s e d b y c o n s t a n t m e c h a n i c a l d a m a g e

( s c r a t c h i n g ) o r p a r a s i t i c e n c y s t m e n t m a y l e a dt o t u m o r o u s g r o w t h s . 16 Vi r u s e s a r e a l s o b e -l i e v e d t o p l a y a n i m p o r t a n t r o l e i n t h e i n d u c -

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Aq uariu m Fish D ermatologic Diseases 231

tion of skin tumors in fish. Viruses and virus-

like particles identified in benig n tumo r tissueof fishes were (most frequently) herpesvirusesand (less frequently) adenoviruses, retrovirus-es, rhabdoviruses, birnaviruses, or picornovi-ruses. In malignant forms, like sarcomas orlymphosarco mas, evidence was linked to retro-virusesJ 6 To date, the significance of the vi-ruses and viruslike particles is mostly specula-tive. 16 Clinically, because the majori ty of fishskin tumors appear to be benign, surgical re-section may be curative as well as diagnostic.Any unidentified mass removed from the fish

should be submit ted for histopathologic exam-ination.

E n v i r o n m e n t a l / N u t r i t io n a l D i s e a se s

A c i d o s i s / A l k a l o s i s

In cases of chronic acidosis, a decrease inpH, fish will develop excess mucus productionand inflammation of the skin, which is oftenreported by the client as a milkiness.1 The gillepithelium will erode, and gill hemorrhages

are common. Hemorrhages of the skin alsomay occur, but more often the o wner will notethat the fish was in excellent condition with itscolors brighter than usual, and then it wasfou nd dea d at the bottom of the aquarium, stillin excellent colorJ In a closed aquarium, thepH of the water tends to decrease graduallywith the input of fish waste products and theactivity of the nitr ifyi ng bacteria. 1,9 Th e usualcorrective measure is partial water changeswith alkaline w ater J '9 If the local water supplyis acidic (not common), sodium bicarbonate

can be adde d to increase the buffer ing compo-nent of the system. A third approach, in anemergency situation, is to aerate the water vig-orously to expel carbon dioxide.

With chronic alkalosis the gills are pale, andskin erosions along with increased mucus pro-duction are frequent complaints. Gill necrosisis not usually appreciated until postmortem. ~Filtration of water th rou gh peat will acidify thewater for changes and can be used in areaswhere the water tends to be alkaline. In sometanks, the addition of hydrochloric acid rou-

tinely occurs to lower the pH, but it is not along-t erm solution. 1 Ther e are nume rou s

commercial products designed to adjust pH

parameters available through pet stores.Supersa tura t ion

Supersaturation can be the result of abnor-mal accumulations of any gas in aqu ariu m wa-ter, the most common offen der being nitrogengas. 1 Affe cted fish will have gas un de r the skinof their fins, body, and mouth, leading to thedescriptive name of the resultant syndrome,gas bubble dis ease ) '2 Severe prob lems occurwhen gas bubble formation in capillary bedscauses ischemia and tissue necrosis. 1 Th e

causes of supersaturation include a leak in ahose or an increased accumulation of oxygencaused by heavy plan t a nd/ or algal growth. 1'2Excessive aeration from airstones does notusually but can contribute to the syndrome.1

Vi t a m i n E D e f i c i e n c y

The requirement for vitamin E in the diet ofterrestrial animals is well documented, al-though a demand for this nutrient in fish hasonly been demonstrated in a few cultured spe-cies. 1'18'19 The accidental feeding of a vitamin

E-defi cient diet to a group o f goldfish resulte din progressive fraying and deterioration of thetail and th en the fins. At the terminal stages ofthe disease, an external fungal inf ection devel-oped, and the fish died. The clinical course ofonset to death was 7 days or less, with 90% to100% morb idity, an d 20% mo rtality, is Some ofthe affected fish also showed signs of epider-mal necrosis, likely secondary to bacterial in-fection, as skin scrapings showed Aeromonas hy-drophila, Pseudomonasspecies, and Citrobacterfreundii . Correction of the vitamin E-defic ient

diet resulted in immediate and permanentclinical improvement and a drastic reductionin morta lity . 18

H e a d a n d L a t er a l L i n e E r o s i o n S y n d r o m e

Head and Lateral Line Erosion Syndrome(HLLE) is a comm on sy ndro me of marine spe-cies kept in captivity. 2~ The clinical lesions ofaffected fish include superficial erosions of th ehead and face that progress down the lateralflank to involve the lateral line. The clinicaldisease is usually nonfat al but can result in per-

manent scarring of the skin surface.1'20 A pri-mary cause of HLLE has not been discovered,

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2 32 Murphy and Lewbart

although environmental stressors such as poor

water quality, inadequate nutrition, and thepresence of opportunistic pathogens appear tobe involved. 1'2~ Tr ea tm en t with antimicrobi alsalone is unsuccessful, however, resolution ofthe lesions may be observed with vitamin Csupplementation or elimination of activatedcharcoal from the filtration systems. 1,20 Recentreports of a reovirus isolated from a moribundangel fish displaying the initial lesions associ-ated with HLL E may support the th eory of animmunocompromised state existing in fish af-fected with HLLE . 2~ Aquatic reoviruses tend

to have a low pathogenicity and are generallyfound in association with stress-related diseaseoutbreaks. Further in vivo studies will be nec-essary to establish an etiologic link betweenHLL E an d the reovirus. 2~

P r e v e n t i o n a n d C o n t r o l

Preventative medicine is always the bestmedicine. This is especially true when dealingwith pet fishes, whether they are freshw ater ormarine varieties. T he logistics of treati ng cap-tive fish is often difficult and may be costly interms o f the value of the fish, necessary equip-men t (extra tanks, heater, etcetera), and time. 21An extensive review of all of the componentsof prop er preventative fish medicine is beyon dthe scope of this report. The authors wouldrecommend that any clinicians involved intreating pet fish patients consult references onspecies compatibility, 1,2,9,21 water quality anden vi ro nmen ta l cont rol , 1'2'9'21 lightin g, 1'3 bio-logical filters, 1'2 sanitatio n, disi nfec tion andsterili zation, 1'21 an d nut rit ion . 19'21'22 A goodstarting point for a preventative medicine pro-gram is quarantine.

Q u a r a n t i n e

Quarantine is designed primarily to preventthe in trod ucti on of disease into a water systemand to protect the resident fish. Some level ofquarantine is essential in any aquarium set-ting. 21 Incom ing fish should be isolated fro mthe established population for a rec ommen dedperiod of time, ranging from 21 days (mini-

mum) to 6 weeks (preferable).l'2 Most ownersare unable to adhere to these guidelines be-

cause quarantine systems are temporary and

usually labor intensive.1 Isolation is the key toquarantine. The most reliable way to accom-plish isolation is by physical separation of thefish, with independent tanks, filters, andpumps. 21 Quar anti ne tanks should be small forease of cleaning and fish handling. A flow-through filter system is ideal but not practicalfor most clients. A single quarantine tank canbe successfully maintained by frequent waterchanges (every 3 to 5 days) to avoid ammoniaand nitrite buildup; however, it is importantthat the water temperature does not fluctuate

by more than a few degrees Fahrenheit toavoid stressing the fish. 1 Othe r stress r educer sin the quarantine tank include providing shel-ter (p olyvinylcho ride [PVC] pi pe of an app ro-priate diameter and length works well [Fig 8])and keeping t he fish density to a mini mum. 2~The quarantine aquarium temperature shouldbe actually maintained at the upper end of thespecies optimum range to speed parasite lifecycles. 21

Unless the fish are showing signs of clinicaldisease, hands-on examination for diagnostic

purposes should be delayed until 4 to 7 daysafter arrival. In the meantime, observation,history taking, fecal examination, and acclima-tizing the fish to the new conditions shouldproceed. 21 Acclimatization involves floa tingthe transport bag in the quarantine water sys-tem and slowly siphoni ng the system water intothe bag to effect a complete transition to thenew water conditions in 1 to 3 hours. For thenext 24 hours, the fish should be kept in adimly lit, quiet ar ea a nd not di stur bed. 21 In the4 to 7 days that follow, the fish is watched for

signs of disease, such as frayed fins, areas ofdiscoloration or depigmentation, and grosslyvisible ectopa rasit esf I After the fish have hadtime to acclimatize to their quarantine tank,skin scrapings and gill biopsies to rule out ec-toparasites may be performed. The num ber offish sampled will depend on the total numberof fish, thei r size, and value. Ideally fish shoul dnot be allowed out of qu arant ine un til all diag-nostic tests undertaken are normal or until theproblems identified are already present in theshow tank. 21 Any problem identified must be

specifically treated and retested to verify effi-cacy of treatment before the fish is released

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Aqua rium Fis h Dermatologic Diseases 2 3 3

f r o m q u a r a n t i n e . J u s t b e f o r e r e l e a s e , t h e f i sh

s h o u l d b e e x p o s e d t o t h e s h o w t a n k w a t e r ino r d e r t o a c c l i m a t i z e t h e m t o a n y e n d e m i c d i s-e a s e s w h i l e t h e y a r e s t il l e a s i l y a c c e s s i b l e f o rp o s s i b le t r e a t m e n t . 21

Va c c i n a t i o n

T h i s f o r m o f p r e v e n t a t i v e m e d i c i n e h a s li t-t le a p p l i c a t i o n a s y e t in t h e p e t a q u a r i u m s et -t i ng . T h e r e a r e c u r r e n t l y o n l y t h r e e c o m m e r -c i a l ly a v a i l a b l e v a c c i n e s f o r f i s h , a n d t h e s e a r eu s e d e x c l u s i v e l y i n t h e f o o d f i s h i n d u s t r y .V i b r i os i s , f u r u n c u l o s i s , a n d e n t e r i c - r e d m o u t h

d i s e a s e a r e t h e d i s e a s e s f o r w h i c h f i sh m a y b ev a c c i n a t e d . 21 S e v e r a l v a c c i n e s a g a i n s t b a c t e r i a la n d v i ra l p a t h o g e n s a r e u n d e r d e v e l o p m e n ta n d s h o u l d b e a v a i la b l e i n t h e n e a r f u t u r e , b u ta g a i n , t h e s e a r e n o t f o r u s e i n t h e h o m ea q u a r i a s e t t i n g . 22'23 T h e r e a r e c u r r e n t l y n op r o p e r l y c o n t r o l l e d s t u d i e s i n t h e l i t e r a t u r e o nt h e e f f ic a c y o f v a c ci n e s f o r d i s e a se s o f m a r i n et r o p i c a l f is h e s. M e t h o d s o f v a cc i n e a p p l i c a t i o ni n c l u d e i m m e r s i o n , i n t r a p e r i t o n e a l i n j e c t i o n,a n d o r a l a d m i n i s t r a t i o n . 21

T r e a t m e n t

T h e m a i n p u r p o s e o f t h is r e p o r t w a s t o p r o -v i d e i n f o r m a t i o n o n th e c o m m o n i n t e g u m e n -t a r y d i s ea s e s o f p e t f i sh e s. M a n y t e x t b o o k s a n da r t i cl e s o n a q u a r i u m f i s he s p r o v i d e s p e c if i ct r e a t m e n t r e g i m e n s f o r f i sh s ki n d i s ea s e s, a n dt h e a u t h o r s e n c o u r a g e p o t e n t i a l p e t f is h c l i n i-c i a n s t o r e f e r t o t h o s e p u b l i c a t i o n s f o r a m o r ec o m p l e t e g u i d e t o t h e t r e a t m e n t o f f i sh sk i nd i se a se s .a ,2 ,5 , 6, 11 ,2 4 ,2 5 We h a v e i n c l u d e d a l i m -

i t e d t r e a t m e n t t a b l e ( Ta b l e 1) o f s o m e o f t h e

m o r e c o m m o n l y u s e d m e d i c a t i o n s i n f r e sh w a -t e r a n d m a r i n e f i s h s k i n d i s e a s e s . 5'6'11

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