Fish Diseases Recorded in New with a Discussion on Potential …docs.niwa.co.nz/library/public/FRDop34.pdf · 2013-02-04 · with a Discussion on Potential Sources ... (1982) Fish

lssN 01 10-1765

Fish Diseases Recorded in New zealand,with a Discussion on Potential Sources

and Gertification Procedures

byN. C. Boustead

Fisheries Research DivisionOccasional Publication No. 34

Fisheries Research Division occasional publication no. 43 (1982)

Fish Diseases Recorded in New Zealand,with a Discussion on Potential Sources

and Certification Procedures

byN. C. Boustead


198'2


Published by the New Zealand Ministry ofAgriculture and Fisheries

Wellingtonr982

rssN 0l10-1765


Gontents

IntroductionOccurrence of diseases to May 1973Occurrence of diseases from 1973 to I 980

Bacterial diseases .... Viral diseases

Parasitic diseases ...Fungal diseasesNon-infectious diseases

Miscellaneous submissronsDiscussion...Disease controlCertificationReferences..AcknowledgmentsAppendix: Submitting fish for disease diagnosis ...

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67

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lntroduction

Hatcheries for trout and salmon have operated inNew Zealand since the introduction of those fish. Atthat time knowledge of diseases of fish was limited,and there are few early records of fish diseases. Fishhealth problems have been examined by officers of theMarine Department, the Animal Health Division ofthe Ministry of Agriculture and Fisheries (MAF), andthe universities. In 1972 Fisheries Research Division(FRD) of MAF appointed a parasitologist, Dr P. M.Fline, to study fish parasites and diseases. Thisappointment was made in accordance with recom-mendations of the Fisheries Committee of theNational Development Conference and after theintroduction of legislation to permit freshwater fishfarming. (This legislation was amended in 1973 toexclude trout farming.)

After the appointment of Dr Hine all submissions offish health problems were catalogued. There were 476submissions between May 1973 and December 1980.

Most were individual fish caught by fishermen,though there were important submissions of cultured

The earliest reports of disease in New Zealandhatcheries were by Scott in l89l and Gilruth in 1902

(Gaylord, Marsh, Busch, and Simpson l9I2). Thereports described tumours which were thyroidcarcinomas. These were widespread among hatcheryfish at that time.

Fry of grass carp (Ctenopharyngodon idella) weteimported into New Zealand in October 1971, andmany died from varioús parasitic diseases. Theparasites were identified as Ichthyophthirius multifilüs,Bothrio cep halus goukongensis, and species of. Triþartie I la,

Dactylogltrus, and GyrodacfTløs. These were all con-trolled while the carP were under quarantine(Edwards and Hine 1974).

Occurrence of diseases to May 1973

fish. Priority was given to the investigation of diseasesin salmonids and eels because of their importance inrecreational and commercial fisheries. Submissions ofornamental fish were normally referred to FisheriesManagement Division of MAF. Major fish killscaused by pollution were also dealt with in someinstances, but are not discussed here.

The main objectives of FRD's investigation into fishdiseases have been the identification, control, andprevention of these diseases in New Zealancl. Some

exotic diseases may threaten fish stocks, and it isessential that, if they occur, they should be rapidlyand accurately diagnosed and their occurrence fullydocumented.

This publication summarises the fish diseasesrecorded by FRD from May 1973 to 3l December1980 and documents the important diseases knownbefore this period. In addition, there is a discussion onpossible sources of disease and requirements forcertifying fish health.

In 1972 there were some losses of rainbow trout(Salmo gairdneril at the South Canterbury Acclimat-isation Society hatchery at Temuka. These wereinvestigated by Dr G. C. Hewitt, though there was nopositive identification of the cause. His unpublishedreport suggested that some particles (seen by use ofelectron microscopy) in liver tissue of the fishexamined may have been either virus or breakdownproducts of the cell. All fish were removed from thehatchery and destroyed. Hatchery design preventedthe disinfection of the raceway. Under the supervisionof MAF the hatchery was restocked in 1973 and 1974.

Losses similar to those of 1972 did not recur, thoughbacterial gill disease caused some losses in 1974.There has been no further evidence of a viral disease'


In 1972 there were also mortalities in quinnatsalmon (Oncorhychus tshawytscha) at the Departmentof Internal Affairs hatchery at Wanaka. These wereattributed to nocardiosis (P. M. Hine pers. comm.),and the salmon concerned were removed anddestroyed. The hatchery was restocked with rainbowtrout in 1973, and those fish were regularly examinedfor disease. No sign of nocardiosis was found, and thedisease has not recurred in salmon or trout at thathatchery.

The most important fish disease identified beforeMay 1973 was whirling disease caused by Mlxosomacerebralis. This was identified in rainbow trout at the

Otago Acclimatisation Society's hatchery at Waitati(Hewitt and Little 1972). The hatchery was closedand disinfected, and it is no longer used, though theponds are still there and are accessible to wild fishfrom the Waitati River.

Maconie (1937) refers to whirling behaviour oftrout in the Akatarawa River and suggests that it mayhave been caused by what is now known as whirlingdisease. This report cannot be substantiated becausãother diseases can cause similar behaviour. McDowall(1978) gives a more comprehensive review of diseasesand parasites in New Zealand freshwater fish.

Occurrence of diseases from 1973 to 1g8O

Bacterial diseasesBacterial gill disease and columnaris disease were

the most common infectious diseases referred to FRDfrom fish culture facilities. Bacterial gill disease wasprevalent in cultured juvenile quinnat salmon andalso occurred in cultured trout. Losses of fish weregenerally small (less than l"/o per day), though themortality rate was usually increasing before treatmentstarted. In one instance, much of the population diedwhen small numbers of salmon were kept with limitedwater exchange in small swimming pools. In thisexample, the disease would have been aggravated bythe poor water exchange. Outbreaks of bacterial gilldisease sometimes coincided with increased sedimentin the water supply after hear.y rainfall. Control wasachieved by treatment with Diquat ("Reglone", madeby ICI Tasman Limited), a quarernary ammoniumcompound (Cetrimide), or "Furanace,' (,.Nifur-pirinol", made by Dainippon Pharmaceutical Co.,Ltd.). Diquat and Cetrimide were used at 8 mg perIitre and 2 mg per litre, respectively, for I hour dailyfor 3 or 4 days. Furanace was used in a l-hour bath at0.5 mg per litre. Frequently, more than one of thesetreatments was used to control an outbreak; so it wasnot clear which agent or combination had the greatesteffect.

Columnaris disease (Fig. l), which is caused byFlexibacter columnaris, occurred on the fins of elvers(Anguilla spp.) in warm-water culture (22"-25"c)

(Hine and Boustead 1974). There was often adramatic increase in mortality, though outbreakswere controlled by Furanace. A bacterial infectionresembling columnaris disease was seen on the gills of

Fig- l: Columnaris disease. Typical damage and congealedblood in the gills of an eel.


eels of 60 cm total length that were introduced intoponds for growth studies or held in eel-processingholding tanks. Columnaris disease has not been seenin salmonid culture.

Vibrio anguillarum, which causes vibriosis, wasisolated from the kidney of a wild long-finned eel(Anguilla dieffenbachil from Lake Ellesmere (abrackish, eutrophic, coastal lake) . Although therewere lesions on the skin of this eel, there have been nomortalities in the wild, or in culture facilities, whichcould be attributed to V. anguillarum.

Aeromonas hydroþhila, which causes bacterial sep-ticaemia, was isolated several times from kidneys andlesions of dead or moribund fish (Fig. 2) includingsalmon, trout, ornamental fish, and eels in hoidingtanks.

The acid-fast bacterium Mycobacterium marinum wasidentified from an imported tropical Íis}r (Xiphoþhorusmaculatus). Other acid-fast bacteria have beenidentified in consignments of ornamental aquariumfish.

Clostridium botulinum which produced "Type C"toxin was isolated from the intestine of a koi carp(Cyþrinus sp.) (National Health Institute unpublisheddata), and it has been described as the cause of deathof various waterfowl in the Auckland area (Mar-tinovich, Carter, Woodhouse, and McCausland1972). These infections of C. botulinumwere thought tooriginate from migrating sea birds, and theoccurrence in koi carp was believed to be accidental.Other C. botulinum toxins are not known from NewZealand,. Type C botulism occurs only rarely in manand is different from the toxins that do affect man.

Viral diseasesNo viral diseases were identified from New Zealand

freshwater fish, though lymphocystis was found inimported tropical aquarium fish which were stillunder quarantine (Durham and Anderson l98l).Tissue cultures of fish cell lines were not available forthe detection of fish viruses. Ilowever, there has been

Fig. 2: Bacterial septicaemia. A wildgoldfish with haemorrhages which aretypical of several bacterial diseases Inthis case the bacterium was identifiedas Aeromotas þdrophilø.

no behavioural or histological evidence of viraldisease. Once, when fish mortalities were notexplained, and viral disease was suspected, samples ofthe affected fish were sent to the Eastern Fish DiseaseLaboratory (now the United States National FishHealth Research Laborarory) in the United Srares.No evidence of fish virus was found, and the losseswere attributed to thiamine deficiency.

Parasitic diseasesParasites of New Zealand, freshwater fish have been

described by Hewitt and Hine (1972), Hine (1978),and McDowall (1978). Few of these parasites cancause serious diseases in wild or cultivated fish,though they can have adverse physiological effects ontheir hosts.

The most significant parasitic disease identified byFRD was whirling disease caused by Myxosomacerebralis. It was identified in February 1980 inrainbow trout being raised, for the sports fishery, atthe Silverstream fish hatchery, which is on a tributaryof the Waimakariri River. All 29 000 rainbow troutwere removed and destroyed, and all the few quinnatand sockeye salmon (Oncorhynchus nerka) wereexamined and then destroyed. Surveillance hascontinued, and trace-back studies to identify theextent of the disease are still proceeding.

Parasites of freshwater fish submitted to FRD arelisted in Table l.

Ichtboþhthirius multifilüs, which causes white spot(Fig. 3), was the only parasite causing significantlosses among cultured elvers, though ciliate proto-zoans (a trichodinid species and Chilodonellasp.) wereoccasionally associated with white spot epizootics. Inaddition, Chilodonella sp. was found on elvers free fromother parasitic infection. White spot was seen oncommon bullies (Gobiomorþhus cotidianus), many ofwhich died in Lake Rotorua during September 1976.The cause of these deaths was not resolved, thoughwhite spot may have contributed. Some myxosporean

t'z


inlections in individual eels were quite severe (Figs.4-6); however, they were isolated infections thatoriginated from fish caught in the wild. No epizooticscould be attrlbuted to these myxosporeans in culturedeels, despite the presence of individual eels withseemingly heavy infections.

Fig. 3: White spot on the skin of an eel. The eel has producedexcessive mucus (the opaque white areas) around theencysted parasite.

Fig.4: Mytobolus sp. Cysts (up to I mm in diameter), and pitscaused by burst cysts, on the skin of an eel caught nearHokitika. Infections as severe as this are rare.

TABLE l: Parasites of freshwater fish refened to FRD

Parasite

ProtozoaChilodonella sp.Eimcria anguillacI c h t þ op ht hiríus mu I tif i liìsI c ht þ oþ h t hi riu s nu I tifi lii sI cht hyophthirius nu I tifi lüsI chtþophthiius multifilüsMyxidium sp.Myxobolus sp.

Myxobolus sp.Myxosoma c¿r¿bralis

Scyþhidia sp.Thclohanellus sp.Thclohania sp.Tichodina sp.TrematodaDactylogtrus sp.Gyrodacllus sp.Phlllodistomum sp.S tego d e x amene angui I I ae

S le go de x amene angui llacTclogaster opisthorchis

Tclogaster opülhorchisCestodaTrypanorhynch laruaeNematodaAscarophis sp.Angui llico la aus tralicnsisConlracaemm sp.Eustrongylides sp.Eustrongltlidcs sp.Eustrongllides sp.Spirocamallanus sp.CopepodaLcnaea cyþrinaceae

IsopodaCirolana sp.l

*No data.

Site

GillsIntestineSkin and gillsSkinSurface and gillsSurface and gillsGillsSkin

MuscleCartilageGillsSkinTail muscleGills

GillsGillsUrinary bladder E'el, A. australis, A. dieffmbøchiiLiver Koaro, G. brcaipinnisBody cavity Upland búly, Gobiomorþhus breuiæpsBody cavity Upland bully, G. breaiceps

Liver and gonad Brown mudfish, Neochanna apoda

Ovary Quinnat salmon, O- tshaurtscha

-* Eel, Anguilla sp.Swim bladder Eel, A. australis, A. diellmbachüThroat Rainbow trout, S. gairdncrü

- Eel, Angailla sp.Stomach wall Brown trout, Salmo trutta

Host

Eel, Anguilla sp. Eel farmsEel, A. australis, A. dicflcnbachii Eel farms

Quinnat salmon, Oncorh2nchus tshawltscha Salmon farmRainbow trout, Solmo gairdnerü

Eel, Anguilla sp.Koaro, Galaxias breúpinnísEel, A. australis, A. dicffcnbachiiEel, A. auslralis, A. dicllaúachü

Koaro, G. breúpinnisRainbow trout, S. gairdnerü

Short-finned eel, A. australisEel, Anguilla sp.Crayfish, Paranephroþs 4alandiasLong-finned eel, A. dieffcnbachü

Grass carp, Ctcnopharyngodon idellaKoaro, G. breùþinnis

Origin

Lake WaikaremoanaFish hatchery, Waikato RiverLake WaikaremoanaLake Waikere, Rangitata River, eel farmsEel farms, Hokitika, Lake Waikere, Korokoro

Stream (Wellington)Lake ChristabelFish hatchery, Lake MahinerangiLake PounuiBurlings Stream (Wairarapa), eel farmsWater of Leith, Manorburn ReservoirRangitaiki River

RotoruaLake ChristabelEel farm, Rangitaiki RiverLake ChristabelEyre River tributaryEyre River tributaryLake Pounui

Lincoln, Rangitata River

Rangitaiki River, eel farmLake IdaLake HorowhenuaLake Waikaremoana, Lake TaupoRotoruaRangitaiki River

Fish farm

Waitaki River

Intestine

Surface

Mouth

Rainbow trout, S. gairdneüLong-finned eel, A. dieffmbachü

Goldfish, Carassius auratus

Quinnat salmon, O. tshawltscha

fMarine parasite taken from a fish caught at the river mouth.


Fíg. 5: Mlxídiumsp. Cysts (l-2 mm in diameter) near the lateralline of an eel.

Fig.6: Thelohancllus sp. These rysts (0.5-1.5 mm in diameter)were in the mucus and did not appear to damage the skin ofthe eel.

A submission for disease diagnosis was receivedfrom an eel farm in the Philippines after a visit to thatcountry by Dr Hine as part of the New Zealandforeign aid programme. The formalin-fixed eelssubmitted (Anguilla bicolor þacifica ar'd A. celebesensis)

were heavily infected with the microsporean parasiteP listoþ hor a angui I I arum.

Glochidia of the freshwater mussel Hyridella sp.(Fig. 7) were seen attached to the gills of Gobiomorþhus

sp. and common srnelt (Retropinna retropinna) in LakeRotoiti in the Rotorua district and on the gills ofrainbow trout and koaro (Galaxias breuiþinnis) in LakeWaikaremoana.

Parasites are brought into the country whenornamental aquarium fish are imported' Occasionallythese fish are referred to FRD for the identification ofparasitic infections. Parasites identified included 1.

multifiliis and species of Lemaea, Dactylogytus,

Gyrodactylus, Trichodiha, Oodinium, Costia, andThelohanellus. Lernaea cyprinaceae was identified fromgoldfish (Carassius auratus) on a fish farm whereornamental fish were raised in outdoor ponds.Monogenean flukes and Trichodina sP. were seen in

Fig. 7: Glochidia. The larua (0.35 mm in diameter) is shownattached to a gill filament of an eel.

another fish farm where ornamental fish were raised.The parasite Argulus jaþonicas was found on goldfish inornamental ponds in Christchurch.

Marine fish were also submitted for the identifica-tion of parasitic infections. Most of these submissionswere individual fish, though there were twoexceptions. One of these was many lemon soleinfected with digenean metacercaria; the other wasjack mackerel Trachurus decliuis from a fish kill of morethan 1200 fish. The mackerel had many cysts of themicrosporean Octosþorea sp. (J. Weiser pers. comm.)in the pericardial cavity and the oesophagus andbehind the brain around the nerve ganglia.

Numerous ectoparasites were found on snapper(Chrysoþhrys auratus) which had been caught at sea andkept alive in tanks with limited water exchange. Therewere many unidentified trichodinids on the gills andskin; and there were three different monogeneans onthe gills. The monogeneans included a dactylogyrid,an unidentified species which had eight suckers andwas up to 5 mm long, and Biuagina þagrosomi. Inaddition, a large nematode (Philometra sp.) wasencysted in the ovary of one fish. Of these parasites,only B. pagrosomi is included as a parasite of snapperby Hewitt and Hine (1972).

Parasites of marine fish received for diagnosis areIisted in Table 2.

Fungal diseasesFungal infections of skin or gills were seen on koaro,

goldfish, mackinaw (Saluelinus namalcush), rainbowtrout, eels, bullies (Gobiomorþhur sp.), and quinnatsalmon. Fungal infections were found on fish in bothartificial and natural conditions, and the infectionswere often associated with physical damage to the fishor conditions of extreme crowding, as in the holdingtanks for eels. In these tanks many fish could have


been affected. Stress, a result of excessive handling,crowding, and warm temperatures, is likely to havemade conditions favourable for infection. However,fungal infections are rare, and they are controlledusually by treatment with malachite green. Onesalmon-culture facility had some losses associatedwith high water temperatures of up to 22"c. Some ofthe quinnat salmon affected had a variety of fungi(including Trichoderma sp. and Peyronellaea glomerata)infecting their gills. In this instance, the fungi werethought to be opportunists, and the problem wasalleviated with the onset of cooler temperatures andtreatment on separate occasions with formalin(250 mg per litre for less than I hour) or malachitegreen (l mg per litre for less than I hour).

Fungi are found normally on decaying matter infresh water and are likely to infect any dead or dyingfish (such as spent salmon). Consequently, littleattention has been given to fungal infections of fish. Aspecies of Saprolegnid was seen on some fish, andAsþergillus sp. (identified at the Animal HealthDivision laboratory at Palmerston North) was foundassociated with a granuloma in the nasal region of aneel. A species of Botrytis (identified by Dr Anne Bell,Victoria lJniversity, Wellington) was isolated fromthe surface of brown trout (Salmo trutta) ín a displaypond with both brown and rainbow trout. This fungusdid not appear to penetrate the epidermis, but itcaused an unsightly discoloration on the fish. Thelarger of these brown trout had various fungi,bacteria, and protozoa in the swim bladder, and ithad nephrocalcinosis (calcium deposits in thekidney). Dr S. J. Samuels at the Levin Plant HealthDiagnostic Station of MAF identified one of the fungias Fusarium merismoides.

Non-infectious diseasesVarious neoplasia (Figs. 8-ll) were recorded and

are listed in Table 3. These were isolated cases from awide range of fish species and localities whichprobably corresponds to the distribution of fishermenand fisheries officers. Some provisional identificationswere made by FRD, but, for a more informeddiagnosis, specimens were sent either to the Registryof Tumors in Lower Animals, Smithsonian Insti-tution, Washington or to the Animal Health Divisionof MAF.

Several fish had skeletal abnormalities. Curved anddistorted spinal columns were seen on farmed eels anda wild eel from Kahao Stream, near Pauatahanui. Inthe eel farms, only a few long-finned eels and short-finned eels (Anguilla australis) had these wavy

Fig. 8: Neoplasm. A very dense fibroma (30 mm in diameter) ona rainbow trout from the Tongariro River.

TABLE 2: Parasites of marine fish referred to FRD

Site HostParasite

ProtozoaKudoa sp.MicrosporidiaMicrosporidiaOctosþorea sp.TrematodaBiuagina pagrosoniClinostomum sp.Echinostomatid metacercariaEchinostomatid metacercariaMonogenea (3 species)CestodaGlmnorhynchus thyrsitae

AcanthocephalaN e o c c hinor hync hus a ldric h¿ t ta¿

CopepodaLcrnaea sp.Sphyrion sp.

MuscleMuscleGillsVarious tissues

Gills_+

+SkinSkin and muscleGills

Muscle

Intestine

SurfaceSurface

Red cod, Pseudoþhycis bachus

Butterfish, Coridodax þuLLusBlack slickhead, Xenodcnichichthls coþei

Jack mackerel, Trachuns d¿cliais

Snapper, Chrysophrys auratus

Flounder, Rhomôosolea sp.Bastard red cod, Pæudopþcis brcaiusmlusLemon sole, Pelolrclis flauilatusSnapper, C. auratus

Barracouta, Thyrsilcs atun

Yellow-eyed mulleq Aldichctla forsleri

Yellow-eyed molleq A. forsteiTarakihi, CheilodacQlus mañoþt¿tus

Origin

Department of HealthAHD*Bay of PlentyCable Bayf

WellingtonLake EllesmereTaurangaWanganuiWellington

Department of Health

Lake Ellesmere

Manukau Harbour

+Animal Health Division laboratory, Lincoln.fOver 1200 fish affected.

fNo data.

tl¿

10


I

c09l

09 0t 0¿

t#:e..1' ..'"- - 4

Fig. 9; Neoplasm. Multiple tumours in the muscle and viscera of a brown trout from Lake Sedgemere-

Fig. l0: Neoplasm. A myxofibrosarcomaon a brown trout from Lake Wakatipu.

backbones (Fig. l2), and so the deformities were moreof a curiosity than a problem. These skeletalabnormalities were thought to be due to a dietarydeficiency of vitamin C which caused osteomalacia(softening of bones). An eel from the ChathamIslands, and another from Lake Ellesmere, had single,pronounced, inflexible bends in the body. These werethought to be caused by mechanical damage orpredation.

Several trout and salmon from various areas alsohad deformed vertebral columns. Of these, two adultsalmon from Canterbury, three adult rainbow trout(two from Lake Taupo and one from the WaimakaririRiver), and four juvenile brown trout (Fig. 13) fromBullock Stream, Wanaka were examined for whirlingdisease spores, which might have caused thesedeformities. However, no evidence of whirling diseasewas found. Skeletal deformities can be also attributed

',j

11


Fig. t l: Neoplasm. A leiomyoma (smoothmuscle neoplasm) on the stomachmuscle of a brown trout from Ngongo-taha Stream.

to congenital defects or dietary deficiency, or theymay result from myxobacterial infections when thefish are young (Wood 1979).

Fish with unusual coloration were received. Ayellow-belly flounder (Rhombosolea leþorina) had eyesand colour on the side which is normally eyeless andunpigmented. This is rare, but abnormal pigmenta-tion is known in New Zealand flatfish (Colman 1972).

Abnormal pigmentation has been seen in eels. Oneexample was a bright yellow long-finned eel. (This isnot to be confused with the European eel Anguillaanguilla, which is referred to as being yellow or silverwhen migrating.) Dr R. D. Wilson of the ChemistryDivision, Department of Scientific and IndustrialResearch, determined that the yellow coloration wasdue to the absence of melanin, which normally masksthe yellow colour of the carotenoid pigment in the skinof an eel. In addition, a short-finned eel which alsolacked melanin was received from an eel processor.This fish was completely white, except Ior a blackpigment in the eyes. These abnormalities have beenseen on several eels in New Zealand and Australia.

Some hatchery mortalities have been attributed toproblems not directly associated with disease-producing organisms. The most significant of thesewas a 167o mortality of quinnat salmon in theSilverstream hatchery in 1973. There was no evidenceof bacterial or protozoan disease or contaminated

Fig. l2: Curvature of the spinal column ofan eel.

water supplies. Samples of the fish were then sent tothe Eastern Fish Disease Laboratory where histologi-cal examination did not reveal any evidence of knownsalmonid viruses. Muscle necrosis, and the behaviour

Fig. 13: Skeletal deformities. Deformed trout from BullockStream.

72


of the fish before death, suggested that the losses hadbeen due to thiamine deficiency (R. L. Herman pers.comm.).

Calcific heart disease is well known among adultbrown trout in New Zealand (Prior, Webber,Alexander, and Barclay 1968). Further examples ofthis condition were received from Lake Wakatipu,

Lake Benmore, Lake Sedgemere, and LakeWaikaremoana.

Sunburn (or backpeel) occurs in cultured sal-monids. It was seen on quinnat salmon after manycloudless days in summer, and occasional deathsoccurred when the sunburn had predisposed the fishto fungal infection.

Neoplasm Organ

Lipoma MuscleMultiple infectious granuloma MuscleGranuloma VisceraNephroblastoma LiverFibroma SkinFibropapillomatous growths ToothProbable neurilemmoma LiverMesenchymal neoplasm Anal finGranuloma I{idneyGranuloma KidneyMalignant lymphoma KidneyLeiomyoma IntestineNeurofibrosarcoma SkinMyxofibrosarcoma SkinLeiomyoma TestisHaematopoietic neoplasm KidneyLipoma MuscleNeurilemmomal sarcoma SkinFungal granuloma SkinThyroid adenocarcinoma ThyroidNeurofibroma SkinThyroid adenocarcinoma ThyroidResolving haematoma MuscleBaso-squamous cell carcinoma SkinLeiomyoma VisceraHeiomyosarcoma SkinSarcoma OperculumBaso-squamous cell carcinoma SkinNeurofibroma HeadFibroma IntestineNeurofibroma SkinCutaneous fibroma SkinInvasive neurilemmoma VisceraProbable haemangioma SkinAdenoma KidneyPleomorphic fibrosarcomas Skin

TABLE 3: Neoplasia in fish received by FRD

Fish

Kahawai, Aripis tnttaCommon river galaxias, Galaxias uulgarisGoldfish, Carassius auratusBrown trout, Salmo tnttaRainbow trout, Salmo gairdneriiAngelfish, Pteroþhyllum sealare

Spiny dog{ish, Squalus acanthias

Quinnat salmon, Oncorhynchus tshawytscha

Snapper, Chrysoþhrys auratusSnapper, C- øuratus

Rainbow trout, S. gairdneiiBrown trout, S lnttaTrevally, Caranx georgianas

Brown trout, S tnttøKahawai, A. ttuttaRainbow trout, S. gairdneriiShort-finned eel, Anguilla australisBrown trout, S- tnttaE'el, Anguilla sp.Rainbow trout, S. gairdneriiGoldfish, C. auratusBrown trout, S- truttaRainbow trout, S- gairdneriiCommon smelt, Retroþinna retroþinnaBrown trout, S- tnttaRainbow trout, S. gairdnerii

Quinnat salmon, O. tshawytscha

Common smelt, R. retropinnaRainbow trout, S. gairdneriiBrown trout, S. truttaGrey mullet, Mugil rcþhalus

Rainbow trout, S. gairdneriiBrown trout, S- tru¿la

Brown trout, S. tmttaRainbow trout, S. gøirdneriiBrown trout, S. tntto

Area

Canterbury BightRakaia RiverEastbourneLa Fontaine StreamTongariro River(Imported)Duck CoveRangitata RiverGisborneHauraki GulfTongariro RiverNgongotaha StreamDargaville beachLake WakatipuWaimakariri River mouthLake TaraweraWaikato RiverLake BenmoreLake EllesmereLake WanakaNear RaetihiRakaia RiverRotoruaLake EllesmereGrey RiverLake OkarekaGlenariffe StreamLake EllesmereLake ColeridgeRakaia RiverAucklandTongariro RiverLake SedgemereTemukaLake TaraweraLake Wakatipu

Refe¡ence

RTLA* 648RTLA 664RTLA 676RTLA 803RTLA 822RTLA 972RTLA 938RTLA IOO2

RTLA IO4IRTLA IO42RTLA 1043RTLA IO44RTLA 1O7O

RTLA IO9O

RTLA 1T72RTLA 1205RTLA 1267RTLA 1476PNt 60lit4lPN 601704PN 605655PN 607168PN 7000s5PN 60+735PN 606308PN 700420PN 70226+PN 702753PN 704652RTLA 1884RTLA 2095RTLA 2062RTLA 2217wAT 80003164wA 8000+972wA 80008416

tRegistry of Tumors in Lower Animals, Smithsonian Institution, Washington.

tAnimal Health Division Laboratory, Palmerston No¡th.fAnimat Health Reference Laboratory, MAF, Wallaceville.

t3


Miscellaneous submissions

Examinations of hatchery fish have been carriedout at the owner's request for the certification of fishhealth. Fish from hatcheries of MAF, the Departmentof Internal Affairs, and acclimatisation societies wereexamined before export or liberation. Regularsampling was also done at Wanaka and Temukahatcheries as part of investigations into mortalities.Although these examinations were limited, no seriousfish diseases were found.

Some submissions were of individual wild fish withabnormalities for which there was no obvious cause.Often these specimens were frozen, or had autolysed,and so they were unsuitable for detailed examination.The fish were from different areas, and they weresufficiently affected to warrant inclusion in thispublication. A 1.7-kg rainbow trout showing signs ofdistress was caught with a hand net at the TongariroRiver delta, Lake Taupo. There were many fluid-filled cysts (up to I cm in diameter) throughout theliver and, to a lesser extent, in the spleen and kidney.Samples were sent to the Registry of Tumors in LowerAnimals, but the material had autolysed beyondrecognition.

A rainbow trout, taken from a small tributary ofLake Rotorua, had been swimming normally andfeeding before it was caught, but the surface of thefish, including the tongue and mouth, was coveredwith petechiae (small haemorrhages). Bacteriologicaland histological examination of viscera and lesionsfailed to reveal the cause of these spots. Similarlyaffected fish have been received from the WaihaoRiver (Fig. l4).

A rainbow trout caught in Lake Rotoiti in theRotorua district had large areas of haemorrhage onthe skin around the tail, operculum, and vent and onthe ventral surface. The fish was received frozen, andhistological examination of viscera and skin revealedno sign of infectious disease agents. Similar lesionswere seen on several rainbow trout from the Rotoruaarea, Lake Taupo, and the Tukituki River. These fishwere emaciated, had lost scales, and had inflam-mation of the dermis over much of the body. One ofthese trout was suitable for bacteriological examina-tion, and large numbers of the bacteria Aeromonashydroþhila and Pseudomonas fluorescenr were isolatedfrom the lesions.

Four rainbow trout from Lake Taupo, two quinnatsalmon from the Waitaki and Waimakariri Rivers,and a brown trout from Lake Emma were receivedwith superficially similar fluid-filled caviries in muscletissue. The cavities were characterised by a developedwall with some inflammation. Their contents rangedfrom amber and red fluids to a thick creamy fluid withremnants of muscle fibre (Fig. l5). The largest cavitywas 80 mm in diameter.

A submission was received from Scotts Creek, LakeAlexandrina. From a spawning run of brown trout, I0out of 62 fish appeared blind in one or both eyes (J.W. Hayes pers. comm.). The lens of the eye wasopaque, but the cause of the problem was notaPParent.

Fig. 15: A section through the skin and muscle of a brown troutfrom Lake Taupo. The cavity (33 mm in diameter) is walledoff from the surrounding muscle and contains muscleremnants.Fig. 14: Petechiae on the ventral surface of a rainbow trout.

74


Another isolated submission was an adult quinnatsalmon caught by gill-net off the Waitotara Rivermouth. This specimen had been repeatedly frozen andthawed before it was received, but there was evidenceof much damage. Although the skin was intact,portions of the muscle beneath had been totallydestroyed (particularly posterior to the vent), which

left an area (122 mm by 72 mm) between the skin andthe vertebrae that was devoid of flesh. There weresimilar cavities around the vertebrae and caudalpeduncle and at the base of the pectoral fin. The causeof this damage is not known, but the kind and site ofthe cavities suggest a proteolytic bacterium wasinvolved.

Discussion

The main fish disease of concern in New Zealand iswhirling disease. In addition to its occurrence at theWaitati hatchery (Hewitt and Little 1972), whirlingdisease occurs in wild rainbow trout in LakeMahinerangi and its catchments (my unpublisheddata). This lake is 50 km from the Waitati hatchery,and it was stocked with many rainbow trout that wereraised at the hatchery before it was closed. Movementand release of fish from this area are now prohibited.The identification of whirling disease at theSilverstream hatchery extended the known range ofthe disease. This hatchery is 312 km from Waitati,from which it is separated by four major river systemsand some smaller catchments, all of which drain intothe Pacific Ocean.

A detailed discussion of the mechanisms by whichwhirling disease spreads is beyond the scope of thispublication. The movement of fish (naturally and byman) would need to be considered. In addition,Taylor and Lott (1978) have shown that underexperimental conditions mallard ducks and heronscan transmit whirling disease, though the mechanismof cross infection is not completely understood, andthe sequence of events needed to transfer the diseasein this way may be complex. Flowever, it seems thatthe disease could spread to other waters.

White spot, columnaris disease, and bacterial gilldisease have caused losses in culture facilities duringthe period that FRD has operated a diagnostic

service. White spot is widespread in New Zealand,and it becomes a problem when water temperaturesare high in ponds with little water exchange, or insystems that recycle water without adequate treat-ment. Similarly, high water temperatures favouroutbreaks of columnaris disease. Studies done in theUnited States have shown that the raising of riverwater temperatures by the release of heated effluentsfrom power generating plants, and the concentrationof fish in fish passes around hydro dams, havecontributed to an increased incidence of columnarisdisease in wild fish (Becker and Fujihara 1978).

The bacteria V. anguillarum and A. hydroþhila cancause the diseases vibriosis and bacterial septicaemiain fish, but neither has been reported as having caused

ï:r1ît:rt* in cultured fish during the period under

The lesions in the dermis of individual wild trout(see above) may have been caused by Aeromonasand/or Ps¿udomonas infection. These bacteria areubiquitous in fresh water and are likely to invade anywounded or debilitated fish.

The cavities in muscle tissue of salmon and trout(see above) are commonly believed to be the result ofinfection and encystment by shagworm (Eustrongylidessp.). However, f have not seen any nematodes, orpossible remains of nematodes, associated with thesecavities. Further study is needed to explain how theywere caused.

15


Disease control

Several additional diseases reported in overseasliterature could cause substantial losses of culturedfish in New Zealand. The more significant of thesediseases include the viral diseases infectious pancrea-tic necrosis (IPN), viral haemorrhagic septicaemia(VHS), and infectious haematopoietic necrosis(IHN), the bacterial diseases furunculosis, bacterialkidney disease, and enteric redmouth, and the diseasecaused by the eye fluke (Diplostomum sp.). None ofthese diseases has been seen in New Zealand,. T}:eyare described by Roberts and Shepherd (1974),

Jensen (1978), Needham and Wootten (1978), andRichards and Roberts (1978).

With the increase in fish culture and fish diseasestudies, some previously unrecorded diseases may befound in New Zealand. These diseases could originatefrom various sources; for example, aquarium fish,wild fish carrying previously unknown diseases andparasites, and the illicit movement of fish both to, andwithin, New Zealand.

It is estimated that more than 800 000 tropicalaquarium fish are imported into New Zealand eachyear (S. G. Pullan pers. comm.). Gratzek, Shotts, ahdBlue (1978) have shown that in the United Statesornamental fish carry a wide range of parasites anddiseases. This finding is supported by the results fromthe examination of a few ornamental fish by FRD.Lernaea cyþrinaceae, which is not thought to be anindigenous parasite of New Zealand freshwater fish,was found on goldfish in a farm where aquarium fishwere raised for sale. This is an example of howornamental fish may assist the introduction of diseaseorganisms.

Fisheries Management Division now has theresponsibility to control the importation of tropicalfish. There is a 6-week quarantine which is supervisedby the Port Agriculture Service of MAF.

The Animals Act 1967 prohibits the importation offresh and frozen salmonids. This helps prevent theintroduction of new diseases. In addition, theimportation of cold-water aquarium fish (except forbrood-stock, which must be kept under quarantine) isprohibited.

The possibility that other previously undescribeddiseases may originate from wild fish is supported byknowledge of the parasites of New Zealand eels. In1972 there were 17 parasites recorded from eels(Hewitt and Hine 1972). Subsequently, Hine (1978)identified 30 parasites, including several new species.

It has been suggested that tourists who bring theirown fishing tackle to New Zealand could inadver-tently introduce a new disease. For example, thebacterium Aeromonas salmonicida, which causes furun-culosis, can survive for 29 days in mud and for morethan 6 days on wet or dry fishing nets (McCarthy1977). However, though it may be theoreticallypossible to transfer an exotic disease to New Zealandin this way, the sequence of events needed to completesuch a transfer is lengthy and complex, and thelikelihood of its happening may be remote.

The potential for introduction of exotic diseases

emphasises the need for constant surveillance byMAF.

There are comprehensive measures for the controlof disease outbreaks in fish farms in Part III of theFreshwater Fish Farming Regulations 1972. Thislegislation was introduced after the discovery ofwhirling disease in an acclimatisation societyhatchery (Hewitt and Little 1972), and it required theoperator to notify MAF of specific, serious diseases orany losses of unknown cause. The regulations gaveMAF the authority to destroy fish stocks, though theyapplied only to commercial fish farms and not togovernment or acclimatisation society hatcheries, norto fish farms which raised ornamental or tropical fish.

The Animals Act 1967 was amended after thesecond outbreak of whirling disease. Seven fishdiseases are specified, and any hatchery personnelwho suspect the presence of one of these diseases mustreport immediately to Animal Health Division. Thediseases scheduled are: the viral diseases IPN, IHN,VHS, and spring viraemia of carp; the bacterialdiseases caused by A. salmonicida and, Yersinia ruckeri;

and whirling disease.

t6


Certification

Many countries (including Great Britain and otherEuropean countries, Canada, and the United States)require fish-health certification for the importation oflive or frozen salmonids. Other countries areconsidering regulations. International organisations,such as the International Office for Epizootics and theFood and Agriculture Organization, have beenstudying fish diseases to suggest standard regulationsfor fish-health certification (Rohovec 1979, Ghittino1976). The more stringent regulations, which apply toBritain and Canada require the examination of brood-stock for a 2-year period, with samples taken every 6months. Approved methods are used to look forspecific fish diseases. In addition, the hatchery mustnot take in any fish from outside the farm.

The certification is only as reliable as the techniqueused. Fish that seem healthy may carry diseaseorganisms without ill effect until unfavourableconditions or spawning cause the disease to occur.These subclinical infections may not be detectedduring routine examinations or when examinationsare carried out at inappropriate times. For example,furunculosis can be isolated from asymptomatic fishby additional procedures involving the injection ofcorticosteroid hormones (Bullock and Stuckey 1975).Confidence in the detection of diseases also dependson the extent of sampling of the fish population. Thuscertification should be based on regular monitoring ofthe hatchery and not on the examination of one

consignment (Christensen 1978, Ghittino 1976). It isproposed that regular inspections will be made byAnimal Health Division in accordance with theAnimals Act 1967. These fish-health certificationsrelate to live or fresh fish or eggs only and do not takeinto account any public health requirements. Ova forsalmonid culture in New Zealand is obtained atpresent from anadromous fish, and not from hatchery-reared brood-stock. Consequently, it would not bepossible to meet the certification standards of somecountries. The design, operation, and inspection of afacility must meet the standards required by thepotential export market. The surveillance periodbefore certification is granted may be as long as 2years.

The need for regular certi{ication, and the control offish movement to prevent the spread of disease, alsoapply to the stocking of lakes, streams, or hatcherieswithin New Zealand. Some acclimatisation societiesare aware of this need and have requested MAF toexamine stocks before they are moved.

Many of the more serious diseases of fish are notknown in New Zealand,. The existence of whirlingdisease in some parts of the country makes it thegreatest disease risk to any culture facility. This riskcan be reduced by care in the selection of stocks andby sound hatchery management.

77


BEcKER, C. D., and Fu¡Inenr, M P. 1978: The bacterial pathogenFlexibact¿r columnaris and its epizootiology amongColumbia River fish: a review and synthesis. Monograþh,Ameican Fish¿ies Sociay No. 2. 92 pp

Bur,rocr, G. L., and Srucrnv, H. M. 1975: A¿romonas salmonicida:detection of asymptomatically infected fioùt. Progr¿ssiaeFish-Cultuist 37 (4): 237-9.

Cntlsrnusnu, N. O. 1978: Preventative medicine in fish diseasesand environmental aspects o{ trout larmíng. RiaistaItaliana di Piscicolnra c Ittioþatologia 13 (1):7-9

CoLMAN, J. A. 1972: Abnormal pigmentation in the sand flounder(note). N.Z. lounal of Marin¿ and Freshuater Research 6 (1& 2):2O8-13.

DURHAM, P. J. K., and ANDERSoN, C. D. I98I: Lymphocystisdisease in imported tropical fish. N.Z Veterinary tounal29 (6): 88-91.

Eowenos, D. J., and HINn, P. M. 1974: Introduction, preliminaryhandling, and diseases of grass carp in New Zezlanò.N.Z. Jounal of Marine and Freshwatcr Rescarch I (3): 4+l-5+.

Gevlono, H. R., Mnnsu, M. C., BuscH, F. C., and SlrrarsoN, B. T.1914: Carcinoma of the thyroid in the salmonid fishes.Bullctin of th¿ U.S. Bureau of Fish¿rids 32: 363-524.

GHrruNo, P. 1979: International aspects of disease control inaquaculture. In Pillay, T. V. R., and Dill, W. A. (Eds.),"Advances in Aquaculture", pp. 92-€. Fishing NewsBooks, Farnham.

GRATZEK, J. 8., Suorrs, E. 8., and Br,uE, J. L. 1978: Ornamentalfish: diseases and problems. Marin¿ Fisherics R¿aiew40 (3): s&-{r0.

Hrwrrr, G. C., and HINE, P. M. 1972: Checklist of parasites ofNew Zealand fishes and of their hosts. N.Z. Joumal ofMarine and Freshuater Res¿arch 6 (1 & 2): 69-1 14.

Éfuwrrr, G. C., and Lrrrrn, R. W. 1972: Whirling disease in NewZealand trout caused by Mlxosoma cercbralis (Hofer,1903) (Protozoa: My<osporida). N.Z. Journal of Marineønd Freshualer Research 6 (1 & 2): l-lD.

HtNn, P. M. 1973: Submitting fish for disease diagnosis. FisheriesResearth Diaision Information Leaf let, N.Z. Ministry oJAgiculture and Fishcries, No. 4. 9 pp.

-1978'

Distribution of some parasites of freshwater eels inNew Zealand. N.Z. tounal of Marine and Freshuat¿rResearch 12 (2): 179-47.

HINE, P. M., and BousrEAD, N. C. 1974: A guide to disease in eelÍarms- Fisheries Res¿arch Diúsion Occasional Publication,N.Z. Ministry of Agrinlture and Fishcies, No 6. 28 pp.

References

Acknowledgments

JENSEN, N. J 1978: Fish diseases of viral origin: a schematic review.Nordisk Velerina¿medi¿in 3t 217-20.

McCanrnv, D. H. 1977: Present status o1 A¿romonas infections. -IrProceedings from the International Symposium onDiseases of Cultured Salmonids, pp. 182-9. TavolekInc., Seattle.

M.Dow.rlr-, R. M. 1978: "New Zealand Freshwater Fishes: aGuide and Natural History." Heinemann EducationalBooks, Auckland. 230 pp.

MAcoNIE, J. 1937: Whirligig disease in trout. N.Z. Fishing andShooting Gazette I0 (6): 7-8.

MenrrNovrca, D., Clnrnn, M. E., wooDHousE, D. 4., andMcOausI-eNn, L P. 1972: An outbreak of botulism inwild water{owl in New Zealand. N.Z. V¿t¿rinary Joumal20 (s): 6t-s.

NEronlv, T., and WoorrEN, R 1978: The parasitology ofteleosts fn Roberts, R. J. (Ed.), "Fish Pathology", pp.14,t-82. Baillie¡e Tindall, London.

PRroR, I. A. M., WEBBER, W. L., ALEXANDER, W S., and BercLnv,S. de C 1968: Calcific heart disease in New Zealandbrown trout. Natare 220 (516a):261-2.

Rrcmnos, R. H., and Rorrnrs, R. J. 1978: The bacteriology olteleosts. 1z Roberts, R. J. (Ed.), "Fish Pathology", pp.183-204. Bailliere Tindall, London.

Roarnrs, R. J., and Snnrutno, C. l. 1974: "Handbook of Troutand Salmon Diseases." Fishing News (Books), WestByfleet. 168 pp.

RoHovEc, J. 1979: Review of international regulations concerningfish health. In Fryer, J. L., ct a/., Proceedings from aconference on disease inspection and certification of fishand fish eggs, pp. 7-9. Oregon State Uniucrsitl' Sea GrantCollege Program, Publication No. ORESU-W-79-ØI-

TAYLoR, R. L., and Lorr, M. 1978: Transmission of salmonidwhirling disease by birds fed trout infected withMlxosoma cerebralis. lounal of Protoloologlt 25 (1): 105-6.

TnInNEv, L. D., AKRoyD, J. M., and KrlNnn, A. R. 1978:"Investigating Fish Kills." Fisheries ManagementDivision, N.Z. Ministry of Agriculture and Fisheries. 83

PP.Wooo, J. W. 1979: "Diseases of Pacific Salmon: their Prevention

and Treatment", 3rd edition State of Washington,Department of Fisheries, Hatchery Division, Olympia.82 pp.

I thank Dr P. M. Hine and Dr J. B. Jones for theidentification of some parasites and also Dr Hine, MrG. D. Waugh, Mr A. M. R. Burnet, and Dr R. M.McDowall for their comments on the manuscript. The

co-operation of all hatchery personnel and anglerswho supplied samples of fish is gratefully acknow-ledged, as is the assistance of the United StatesNational Fish Health Research Laboratorv.

18


Appendix

Submitting fish for disease diagnosisMany of the submissions received for examination

had been improperly treated. This limited their valueand sometimes made meaningful diagnosis imposs-ible. The best method of preserving fish de¡rendson the cause of death. The ideal material forexamination is live or moribund fish. Freezing thesample has limited value and should be avoided ifpossible. If formalin is used as a fixative, the materialshould be taken from the fish immediately after death(or preferably from a dying fish that is killed) andthen fixed. flowever, formalin-fixed material issuitable only for the examination of some tumoursand not for the cultivation of bacteria.

Where many fish in a hatchery are affected, themanager should contact the Animal Health Division

immediately. The procedures to follow whensubmitting fish for disease diagnosis are described byHine (1973).

The presence of many dead fish of various species innatural waterways often indicates pollution, and thefish are useful as evidence. Often the cause of death isnot found in the fish, but is found in the water,perhaps kilometres down stream of the dead fish. Fishkills need investigation as they occur, and examina-tion of the fish is of limited value unless there isevidence of a specific pollutant, or disease iswidespread. The local water authority or acclimatisa-tion society, or the Department of Internal Affairs,can investigate fish kills in accordance with theguidelines given by Teirney, Akroyd, and Kilner( l e78).

P, D. HASSELBERG, GOVERNMENT PRINTER, WELLINGTON, NEW ZEAI-ÂND_I98z747BAC-IûO/t2/8tI.f


lssN ()110-1765

Fish Diseases Recorded in New zealand,with a Discussion on Potential Sources

and Gertification Procedures

byN. C. Boustead



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