FISHERIES AND MARINE SERVICE

Translation Series No. 4399

Hexamita: Pathogenicity and therapy

•

by H.J. Rothenbacher, and M. Bohl

-

Original title: Hexamita, Pathogenitat und Therapie

From: Fisch Umwelt '1: 13-23, 1975

Translated by the Translation Bureau (VNN) Multilingual Services Division

Department of the Secretary of State of Canada

Department of the Environment Fisheries and Marine Service Pacific Biological Station

Nanaimo, 'R,C,

1978'

19 pages typescript

'

DEPARTMENT OF THE SECRETARY OF STATE

TRANSLATION BUREAU

MULTILINGUAL SERVICES

SECRÉTARIAT D'ÉTAT

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AUTHOR - AUTEUR

H.J. Rothenbacher and M.Bohl

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13 - 23

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YEAR ANNÉE

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1975 1

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TRAD r: 0 N ON P, ; S Information s,auictn.an;

DIVISION MULTILINGUES

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TITLE IN ENGLISH - TITRE ANGLAIS

Hexamita: Pathogenicity and therapy

TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ÉTRANGÉRE (TRANSCRIRE EN CARACTERES ROMAINS)

Hexamita, Pathogenitaet und Therapie

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1486941 German V.N.N. iTi• 2 4 "In2

"Hexamita, Pathogenitaet und Therapie,"

Fisch und Umwelt 1, 13 - 23, 1975

Hexamita: Pathogenicity and therapy

by

H.J. Rothenbacherland M. Bohl

From the Teichwirtschaftliche Abteilung der Bayerischen Biologischen Versuchsanstalt [Department of Pisciculture, Bavarian Biological Experimental Station], Wielenbach, Federal Republic of Germany

Summary - The flagellate Hexamita salmonis must be counted with the faculta-

tive parasites affecting only organisms already weakened. In cases of massive

infestation--in particular, of the gut and the gall bladder--losses may be

severe among salmonid hatchlings. This particular parasitosis can be con-

trolled successfully with the aid of directed prophYlactic and therapeutic

measures; Enheptin or, better, Acinitrazol are recommended for therapy.

1 Professor Dr. Hans J. Rothenbacher, Associate Professor, Department of Veterinary Science, Colled of Agriculture, Pennsylvania State University, University Park, Pennsylvania 16802, U.S.A., has worked for three months at the Wielenbach Station in 1972 during his trip to Germany in the course of his sabbatical year.

Translator's note: Scientific or common names given between square brackets in this typescript have been added by the Translator. -

t` nIT 1:.1); (: or

;'.;(:).;•4 scr.licrvIcrO.

SEC 5-25 (Rev. 6/78)

-2

Hexamitiasis--hitherto incorrectly referred to as octomitiasis--is

caused by the flagellate Hexamita salmonis MOORE, 1922.

According to present knowledge, this flagellate belongs to the facul-

tative parasites affecting only organisms already weakened. This parasi-

tosis frequently appears in association with certain infectious diseases

or becomes apparent in the fish due to other stress factors; it is encoun-

tered, in particular, in trout brood.

In cases of massive infestation with this parasite, the syndrome isi

characterized by intestinal inflammation. In mainly chronic forms, los 1lSes

are only minimal; however, losses may be high during the acute stage.

Occurrences

Hexamitiasis occurs widely and is encountered, in particular, in

. trout and salmon hatcheries, with all salmonid species--like trout, sal-

man, and coregones--being affected. Free-living fishes apparently are

infested significantly more rarely [than hatchery ones]; however, in

cases where whitefish [genus Coregonus], graylihgs [Thymallidae] or brook

trout [Sa/WO trutta var. fario] were affected by Hexamita, infestation

was always very severe (Sanzin, 1965).

In addition, Rexamita has been found in the eel (Anguilla anguilla),

in Leucapsius delineatus (HECK[EL, 1843]), in the burbot (Lota iota), in

certain aquarium fishes, and in marine fishes. In several instances,

Rexamita has been found also in the carp (Cyprinus carpio) (Sanzin, 1965;

Reichenbach-Klinke, 1966). In addition, this parasite has been found

also in frogs (Rana esculenta), in toads, and in pond water, so that it

is not surprising that Hexamita has been found also as ectoparasite on

the skin of cichlids (Sanzin, 1965). In cichlids, hexamites have been

described as agents causing pitting disease (Lochkrankheit) (Herkner,

1969; 1970). More recently, the genus Spironucleus, which is closely re-

lated to the species Hexamita salmonis, has been found in the grass carp

(Ctenopharyngodon idella) (Molnar, 1971).

Etiology

The agent causing hexamitiasis, as already mentioned further above

is Hexamita semonis MOORE, 1922. This parasite has previously been rer

ferred to, inter alia, as Octomitus salmonis, O. salmonis truttae or O.

truttae. Additional investigations, initiated by the studies undertaken

by Sanzin (1965), will establish whether other species, hitherto listed

separately, also belong to the parasitic species under consideration.

Sanzin has been able to demonstrate that hexamites isolated from pond water,

trout, warmwater fishes, and frogs eventually exhibited identical appear-

ance and behavior. The transfer of these parasites from the host of one

species to the host of another species initiated by Czech authors (Kulda

and Lom, 1964) will provide new insights. The latter authors have been

able to infect a'scalare [viz, a large angle fish, Pterophyllum] with the

hexamite species Spironucleus elegans isolated from amphibians. They de-

monstrated the existence of full identity between Spironucleus of fishes

and Spironucleus of amphibians.

On the basis of both the latter results and those obtained by Sanzin

(1965), we must assume that amphibians may represent a source of infec-

tion for fishes. The-description of a new species (g. symphysodonis)

based solely on a relatively rare finding site in the liver and the spleen

111prè, t-/isInr/i ptIn fts 1 .

)plo5ten 2 „•„,11„), woo, 3 .

///%011 4 11//il

5 . A• 6.

nputw,Glappma 7 . crmro , -1( he KI(1•.•`....' 1 8

9. Kaudate Spolton 10.

- -chrornatische Massenn

5/. t/k/piltioinPill 12.

- 4 -

Figure 1 - Reconstruction of a Hexamita cell. Locations and descriptions of the organelles after Schmidt, Davis, Kulda and [illegible] (after Sanzin, 1965). Key: 1, Three anterior pairs of flagella; ?, Blepharoblast; 3, Groups of basal granules; 4, Nuclei with karysome and halo; 5, Axial filament; 6, Axostyle; 7, Parabasal apparatus; 8, Chromatic masses; 9, Cell wall; 10, Caudal fissures; 11, Chromatic masses; 12, Trailing flagellum.

of a discus fish (Symphysodon discus [i.e. the pompadourfish]) (Amlacher,

1972) does not appear to be justified under the aspects recently established,

and this, in particular, since Hexamita semonis has already been found in

the blood, and we therefore cannot be surprised to find these flagellate-

also in internal organs.

Description of the species

Hexamita exhibits an oval cell body measuring 7.to 12.5 microns in

length and 3 to 6 microns in width. As representative of the Diplomonadida,

this parasite is bilaterally symmetrical and exhibits two nuclei, with each

nucleus being associated with four flagella. The morphology of this pa-

rasite is illustrated in the sketch presented as Figure 1.

- 5 -

Multiplication

Flagellates multiply by means of binary (longitudinal) fission, with

the exception of their flagella (Figure 2). New flagella develop rapidly.

Under certain conditions, Bexamita cells are able to multiply very rapid-

ly. According to American investigations, the intracellular stages, in

particular, are able to multiply enormously (Davis, 1970). Whether the

conglomerate formation observed by us (Figure 3) represents a so-called

-colonial form following very rapid division (fission) processes, a spont

taneous reaction under unfavorable environmental conditions, or a defeJ4-

sive reaction (against serum antibodies) can as yet not be established.

In the closely related trichomonads, it is, in any case, possible to

induce conglomerate formation using a diluted antiserum. Occasionally,

conglomerate formation may be obserVed also spontaneously on the slide

without using antiserum.

- Infection

. Infection takes place upon passive uptake with the food of the rest-

ing (dormant) stages either excreted with the feces or formed [in the me-

dium] (Figure 4): These structures are oval to spherical, and are enve-

loped with a thin, transparent membrane. . Due to the absence of a second

envelope (or sheath), the latter stages can be distinguished from the cysts, ;

and, for that reason, are described as palmella stages. They undergo

fission soon after formation of the palmella, and then are ready to infect

(Davis, 1970).

Attempts to perform artificial infection have already been Undertaken

with good or divided successes, respectively (Kuida and Lom, 1964); Uzmann

6

Figure 2 - Ilexamita undergoing division

Figure 3 - Hexamita conglomerate formation

\IVY •tr' * • '4, •

1* .-444

-7-.

Figure 4 - Possible resting stage of Hexamita

et al., 1965), with Uzmann et al. being able in the rainbowtrout--but not

in salmons--to introduce directly (by way of the anal route) hexamites

. grown in culture. Losses in trout-fingerling and fattening ponds have

also been described (Schaeperclaus, 1954). Losses have also become known

in rainbowtrout-fingerling and spawning ponds (Steinbach, 1968).

Pathogenesis

As representative of the facultative parasites affecting only"organisms

already weakened (Schwaecheparasiten), Hexamita is found also in fishes

exhibiting no clinical symptoms at all. For that reason, several workers

(Schmidt, 1900; Uzmann and Jesse, 1963; Uzmann et al., 1965) regard this

flagellate as commensal, i.e. an organism which provides neither an

- 8 -

advantage nor a disadvantage for this fish. The therapeutic successes

obtained have been discussed as side-effects due to agents or injurious

factors hitherto unknown. However, the majority of authors (Moore, 1923;

Davis, 1923; 1970; Bellet, 1959; Deufel, 1963; Sanzin, 1965; Reichenbach-

Klinke, 1966; Ghittino, 1968; Amlacher, 1972) regard Hexamita as pathogenic

parasite, which, as facultative parasite affecting only pre-weakened or-

ganisms, experiences a certain enhancement of pathogenicity in stressed

host animals, multiplies in great masses, and causes losses of up to 75i

per cent.

As unfavorable factors, we must consider: Overly high stocking densi-

ties; non-optimal water conditions; inappropriate food (Deufel, 1963);

change of food; and infectious diseases like furunculosis, hemorrhagic

viral septicemia, bacterial gill disease, and piscine tuberculosis (Bellet, 1

1959; Deufel, 1963; Ghittino, 1968; Schubert, 1971).

In an experimental design aimed in a different direction, we have been

able to make the interesting observation that the Ro supplied with wet

(fresh) ration are infested distinctly later byglexamites than R o supplied

with dry food.

The hexamite under consideration may be found, above all, in the in-

testinal tract; however, they occur also in the gall bladder. Recently,

they have been demonstrated in the blood and in internal organs, like the

liver, the spleen, and the heart (Amlacher, 1972). TÉtese flagellates have

also been described as gastric parasites (Van Duijn, 1967); the latter

location may well be confined to aquarium fishes.

Preferred sites of infestation in the digestive tract probably do not

exist, although the rectum (Amlacher, 1972), on the one hand, and the

9

anterior digestive region (Uzmann et al., 1965), on the other one, have

been mentioned in this connection. In individual cases, we have found

also exclusive infestation of the gall bladder with Hexamita, as has

Schaeperclaus (1954).

Seasonal appearance of this parasitosis could not be demonstrated.

although American observations speak for preferred spring and early-summer

occurrence (Davis, 1970)--a finding probably associated with the general

brood-rearing phase. Since that phase is.presently distributed largely s

over the seasons due to the breeding of strains spawning early and stra(ns

spawning late in the year, this parasitosis may be encountered more or

less during the whole year.

According to American experience (Davis, 1970), injury of the fish

due to hexamites appears to be a question of the age and, thus, probably

also a question of the immunity of the host; in general, fingerlings

measuring more than 7 to 8 cm in length exhibit only minor injury or no

injury at all.

Symptomatology

There are no .pathognomonic signs, i.e. signs characteristic or dis-

tinctive for this parasitosis permitting its recognition and differentia-

tion; most signs are of a general nature seen also in other diseases, and

this, in particular, since this parasitosis is frequently associated with

other diseases.

In addition to lack of appetite and separation from the mass with con-

centration in the surface layer of the water, or, also, congregation at

the bottom of the basin or pond, respectively, we will frequently observe

a certain darkening of a part of the fish stock.

- 10 -

As consequence of the lack of appetite, hatchery fry, in particular,

will rapidly exhibit emaciation, and the body--in somewhat exaggerated

terms--takes on an almost streak-like appearance, with the head being set

off even more distinctly than is normally the case in fry; in the English-

speaking world, fish affected in that fashion are referred to as "pinheads."

The chronic form of this parasitosis is encountered most frequently.

In cases of minor immediate losses, this disease may be present in stocks

for several weeks, and then, in the long term, still lead to considerable

losses on the whole.

In cases of massive infestation with acute course, a certain motor

ataxia may be regarded as sign indicative for this parasitosis; that

ataxia is characterized by the sporadic occurrence of helical swimming

movements of the type observed also, for instance, in cases of infectious

pancreas necrosis.

Losses of 50 to 75 per cent may occur in the acute form of this para-

sitosis.

Pathological anatomy

In acute cases, massive intestinal inflammation is found at autopsy.

The intestinal lumen is packed with mucous masses or yellowish jelly, but

may also be empty. This catarrhal enteritis is known also in Japan (Sa-

no, 1970).

_ According to both American and Japanese investigators (Davis, 1923;

;970; Moore, 1923; Miura and Ohshima, 1960), there exist also intracellu-

lar Hexamita stages causing severe injury of the intestinal cell walls.

Davis (1970) described only the latter stage as acute form, which is caused

- 1 1 -

by the rapid multiplication of the intracellular flagellate stages. Cell

forms of that type could hitherto not be detected by numerous other authors

including the present ones. It must remain unanswered for the time being

whether we, in that instance, are really dealing with stages of Hexamita.

In cases of Rexamita infestation of the gall bladder, that structure also

soon exhibits distinct pathological changes: In addition to inflammatory

phenomena, we will find hyperplasia reflected in a thickening of the bladder

wall.

Diagnosis

Diagnosis is relatively simple, and is based on the microscopic demon-

stration of the parasite.

For that purpose, a small quantity of the intestinal contents--taken

best from the hind-, mid- or foregut--and bile of the fish suspected to be

diseased is examined at magnification of not less than 100-fold.

Dilution of the midgut contents with tapwater usually causes the Hex-

. amita cell to burst (Sanzin, 1965).

It is recommended that only live fish or, if necessary, material kept

fresh b- storing at low temperatures be used for examination. In the po-

sitive case, the hexamite cells appear as oval, transparent structures

(Figure 5) showing vigorous movement; at 125-fold magnification, these

cells will be about pinhead-sized. The flagella can be distinguished us-

ing a phase-contrast microscope with high magnification.

Specific staining procedures of fixed smears will lead to the visua-

lization of both the construction and the internal fine structure of this

parasite (Rothenbacher and Hitchcock, 1962; Sanzin, 1965).

.NerN . ,

z. • e.

', 1

- 12 -

Figure 5 - Hexamita: Intestinal smear

Therapy

According to American views, control of minor Hexamita infestation,

causing no pathological changes, should not be Carried out (McElwain and

Post, 1968). Therapeutic measures should be instituted only in cases

where Hexamita infestation is severe, i.e. where initial losses have al-

ready occurred and corresponding injury has been suffered by the fish

affected.

For that reason, the experienced practionner will not wait that long,

but will institute control measures already earlier. The calomel (mer-

curous chloride) hitherto used in therapy not only is toxic for fishes

(Yasutake et al., 1961), inhibiting fish growth, but also entails a risk

for man due to accumulation of residues (Reichenbach-Klinke, 1974).

- 13 -

Like carbasone (E-carbaminophenylarsonic acid) and carbasone oxide

(p-carbaminophenylarsonic oxide), respectively, which both contain the

heavy metal arsenic and exert carcinogenic effects in fishes (Halver, 1963),

calomel may no longer be employed as additive to feeds according to FDA

(Food and Drug Administration, U.S.A.) regulations, and, for that reason,

should also in Germany be removed from the market, as gene .rally is already

the case. Instead, use should be made of the Farmitalia product Gabbro-

colTM (emtrysidinal) which contains 100 g DimetridazoleTM

(1,2-dimethyl-

5-nitroimidazole) and 28.5 [g] aminosidine sulfate per kg; that prepa-

ration is added to the feed at a concentration of 1.5 per cent, and given \

for four to five days (Ghittino, 1968). Another medicated feed available

on the German market contains also aureomycin (400 mg/kg) in addition to

the active agent Dimetridazole (1800 mg/kg), which exhibits the specific

anti-Hexamita activity. In two documented cases, therapy with the latter

preparation was reported to have been unsuccessful (Gross, 1973). It is

possible that these cases represented instances of Ilexamita infestation

of the blood and of the internal organs, or instances of the so-called

intracellular intestinal-wall stages. If, in fact, no errors were made

in these therapeutic attempts--assays of the content of active agent per-

formed following these failures demonstrated no deficiencies--it must be

concluded that situations like those just mentioned did exist in these

cases; and this, in particular, since a hexamiticidal . preparation'had been

admixed to the antibiotic aureomycin. According to Van Duijn (1967)

hexamitiasis can be controlled by adding one per cent aureomycin to the

feed r . for four days. However, that antibiotic should be administered no

longer than four days, since otherwise the intestinal flora of the fish

- 14 -

may be killed, leading to avitaminosis, and, in particular, to deficien-

cies of vitamins E and K, and of folic acid.

Since Gabbrocol contains the antibiotic aminosidine sulfate (28.5 g/kg),

we have been looking for a different agent, although our experimental use

1 of Gabbrocol (costing about DM 32.00/kg) had yielded early successes in

eels. On the basis of American results (Yasutake et al., 1961), it was

. TM established, inter alia, that'Enheptin (2-amino-5-nitrothiazo1e) at a

concentration of 0.2 per cent is effective against Hexamita. We have ad-

ded the water-soluble Enheptin (costing DM 83.30/kg, and available only

on prescription) to our wet (fresh) feed and also to our dry feed, and

administered that agent then for four days to our trial fish. The results

obtained are summarized in Table 1.

The isolated--i.e. not general--positive parasite findings are probably

attributable to the inability of the more severely injured hatchlings to

take up the medicated feed. For that reason, the appetite of these fish

, should be stimulated by a preceding sodium chloride bath (1.5 to 2 [ille-

gible] for one hour) (Einsele, 1963). In addition, it is our intention

to attempt Enheptin treatment in the form of a bath.

Since investigations regarding accumulation of Enheptin residues (Post

and Beck, 1966) have revealed relatively high accumulations in various

fish organs--apparently, however, residues accumulating in the muscles

- are degraded very rapidly--and fowl have 'exhibited reproductive distur-

bances, the closely related preparation CyzineTM (2-acetamino-5-nitro-

thiazole) has been tested (successfully) in American trials. In fishes,

1 We are indebted to Farmitalia and Cyanamid, both in Munich, for making samples'available for our experimental work.

5.

6.

7.

- 15 -

Table 1 - Investigations regarding Hexamita control with the aid of Enhep-tin. Key: 1, Date; 2. Trough, Fish number; 3, Start of treatment; 4, Days after start of treatment; 5, Green trough, grading hall; 6, White trough, grading hall; 7, White trough, hatchery.

10.3: 21.3. 22.3. 23.3. 24.3. 2 7. 1

- - Rintie 3 liell;mel Tagelmaliclumffimiphen. Ftw11-Nr. .1441;mn 1 1 3 4 7

(1runt• lt Inno, 441- tierlialle

I

• it, 4

2 + + + 4- .

3 . + 4 + 4 •

. 4 ++++

5 +++ . - +

6 +4- 4.

WeiI7,e Rumv, Sortierluille

1 4 4 + + I- 4 F4 7

2 + +4- -4 . + 1- + + + +4-

3 + + + + - . + 1-1- -

4 . . + + 4- 4- 4 F I 414 I-

5 + + + + +++ .. 4 +

6 . I + 4 4-4 f I f

. / WeiiSe It in ne, Bruthaus

1 ++-+ - + + -

2 +.+++ - -

3 +++ + - - I ++

4 + +1-+ - - + + +

5 - + 4- + + ++ I +

6 -4 + + -f- + + -4 +4 1

Key to symbols:

Negative Weak infestation (on average, one or less than one flagellate per field)

-F.+ Moderate infestation (on average, one to three flagellates per field) • +++ Severe infestation (on average, three to ten flagellates per field) +++4- Massive infestation (on average, more than ten flagellates per field)

The microscopic counts were performed at 500-fold magnification. If one works using approximately 100-fold magnification, infestation density, of course, must be related to a higher number of parasites per field due to the greater visual field.

that preparation exhibited very high tolerance, and yielded a distinct ef-

fect at very low concentrations (10 and 20 p.p.m.), for which reason it

has been proposed that 20 p.p.m. of that preparation be added to the feed.

Feed medicated using the latter preparation at that concentration was

supplied for three days.

. . 1.1)m=

2.

- 16 -

Danish investigations (Solberg and Bregnballe, 1971) have confirmed

favorable action of Cyzine, which is sold in Denmark under the name of

Acinitrazol. One g was admixed to 50 kg marine-fish food or to 25 kg dry

food, respectively, and these mixtures were then supplied for four days.

Since that drug is rather inexpensive, and is effective already at low

concentrations (viz. 40 p.p.m.), its use is very economical.

In Germany, Acinitrazol (2-acetamino-5-nitrothiazole) is marketed by

Fluka (Lilienthalstr. 8; 7910 Neu-Ulm; telephone 0731-74088), with 100 g

costing DM 17.60, and SOO g costing DM 73.70.

Due to the non-absorbability of Cyzine (Post, 1973) by the intestinal

Wall of the fish, this particular preparation can also not be employed in

cases of Rexamita infestation of the internal organs and of the blood,

and, perhaps, also does not attack the intracellular stages demonstrated

at other sites. In cases like that Enheptin would represent the agent

of choice.

Furthermore, it is not possible to apply the reproductive disturban-

ces seen in fowl directly to fishes, and this, in particular, since hexa-

mitiasis, in general, represents a diseases of the brood, with gonadal

development taking place only later in life [in fishes]. Nevertheless,

we must give consideration to this aspect. In Czech investigations

(Favelka and Tesarcik, 1973), Furazolidon has proved its value at a con- /

centration of 30 g per 100 kg feed adminrstered over a period of 14 days.

Since--as already mentioned further above--hexamitiasis occurs frequently

in association with furunculose diseases, it is probable that the hexa-

mites are killed in the course of furunculosis treatment with Furazolidon

21

e

17-

(0.2%, i.e. 200 g/100 kg, for ten days). Finally, Danish experience

(Rasmussen, 1967) indicates that addition of 1.5% magnesium sulfate to

the feed--if required, with further addition of 1.5% sodium chloride)--

supplied for three to four days yields good results, and this, in parti-

cular, when given prophylactically for 14 days. Therapy should be support-

ed by removing or eliminating the noxious factors eliciting hexamitiasis.

Prophylaxis

Preventive measures are based on the knowledge of the etiology of he-

xamitiasis:

(1)Maintenance or re-creation, respectively, of optimal environmen-

tal conditions.

(2)Avoidance of overstocking.

(3)Administration of approriate, nutritive feed.

(4) Observation of hygienic measures, like continuous removal of dead

individuals, and no employment of water having been in contact with Hexa-

mita-infested fishes, since the parasites themselves as well as their

resting (dormant) stages are vectored by way of the water.

(5) In exceptional cases, performance of preventive chemotherapy,

since hexamitiasis occurs every year in certain ponds, once the brood has

attained a certain age (Deufel, 1963; Allison, 1953).

- 18 -

Bibliography

Allison, I.. N., 1953: Advanees in plevention and tioatinent of paiasitic disease of list) •rans. Amer.Tish. Soc. 83 (2): 211 8

1 Amlacher, F., 1972: Taschenbuch der Fiselikranklienen Gustav Fischer N. eilag, Stutti:ai 2 .1ittl. Bellet, R.. 1959• titiert nach Deurd (1 ) 63) und Sanim (19651 und I ;Intlino :)68) ;Davis, 11. S., 1923: Observations on an intestinal flagellate ol Pouf

J. Parasitol. 9 (31:153 62 bavis, II. S., 1970: Culture and disease of game fiNI10% University of California Press, Berkeley

Los Angeles London, 3. Deurd, J., 1963. ot.tomituskrankheit htt Forellen und due Behandhing

. Allg. Fischere»Zig. 88 (9): 2.56 Duijn, C. van, 1967: Diseases or rishe%

, Hoc Book LW., London 2nd cd. i 4 . W., 1963: Kochsalzbader zur Ileilbeh u andlng und zur allgt•meinen K tat i ging de , Fische .

Ôsti.•rr. Fischerei 16 (3/4): 50 3 5 . ( ; hittino, P., 1968: Systematische Bekampfung der ilexanntiasis der Forellen (dal.) R iv. It. Piseic,

Ittiopat. 3 (I): 8 10 6 Gross, IL. 1973: mündliche Mittedung . 7. itaveika, J. und J. Tesareik, 1973: Zdravotni ochrana v lybarstv I (Gesnintinntssclnit; IT t t hm

. Fischwirtschaft), Piag

8 . Halver, J. E.. 1963: ut. nach Herman, R. 1. 1970

9 • .1Ierkner, IL, 1969: «Lochkrankheit » - ein unerschtiptliches Thema Aquarien-Terrarien-Z. 22 ( II): 344-8

1 0 , 1970: Erganzende Beobachtung,en zurn Therna t(Lochkranklied» Aquarien-Terrarien- Z. 23 (5): 154 7

Herman, R. L., 1970: Prevention and control of fish diseases in hatcheries in , A Symposium on . diseases of fishes and shellfishes» Spec. Publication No. 5 Amer. Fish. Soc., Washington, D. C.

Kukla, J. and 1, Loin, 1964: Remarks on the diplomastigne flagellates from the intestine Of fishes Parasit. 54 ( ): 753-62

Me. Elwain, I. B. and G. Post, 1968: EflicaCy of cyzine for trout hex:unit iasts Prog. Fish. (ult. 30 (2): 84 91

Nhura, S. and K. Olishima, 1960: On octomitiasis in rainbow trout with special reference to the pathological findings kip. J. vet. Sti. 22 (4): 201- 8

Ntolnar, K„ 1971: Studies on gill parasitosis of the grasscarp (Ctenopharyngodon idella) caused by

Dactylogyrus lamellatus Achmerow, 1952, 11, Epizootiology Acta vet, Acad. Hung.

Scient. 21 (4): 361 -75 •Ntoore, E., 1923: The lire-history of Octomitus salmonis, on intestinal flagellate of (tout , Anat. Rec. 26,358-'9 Post, G., 1973: persiinliche Mitteilung

Post. G. and M NI. Beck, 1966: Toxicity, tissue residue. and efficacy of Enheptin given orally to rainbow trout for Ilexam it iasis Piog. Fish. Cult. 28 (2): 83-8

12 .Ragnusen, C. 1., 1967: Handbuch 1 Forellenzucht Wan.) Rhodos, Kopenhagen S. 203/4 13. Reichenbach-Klinke, IL, 1966: Krankheiten und Schadigungen der Fische

Gustav Fischer Verlag, Stuttgart 14 . Reichenbach-Klinke, II. II., 1974: Der SiitSwasserfisch ais N.ihrstoffquelle und l'inweltindikator.

Gustav Fischer Verlag, Stuttgart

Rothenbacher, II. and D.1. Hitchcock, 1962: Heat fixation and Gieinsa staining for flagella and other cellular structures of trichomonads Stain technology . 37 (March): 1 I I -3.

15 . San/in, W.-D., 1965: Untersuchungen zur Okologie, Artspetafitat untl Vat iabilitat von IlcAamita salmonis Moore. Dissert, Tier,irztl. Fak. Univers. München

16 . Schiiperclaus, W., 1954: Fischkrankheiten

• Akademie-Verlag, Berlin 17 . Schmidt, W., 1920: Untersuchungen liber OcIomitus intestines truttae •

Arch. Protistenkunde 40 (3): 253-89

18 • Schubert, G., 1971: Krankheiten der Fische

Franck'sche Verlagshandlung, Stuttgart. 4. Auflage

19 ..••••-e Bregnballe: NetleS Mu tel gegen Octotnitus (Ilexamital (' ) l'erskvandsfiskeri- Had,q (M (21

20 . 196 nœn(lItcho Nhitriiting ; .111.1/1,1 . t R . :Ind 1 . W. Un,3: 1 he iirlartitta I ()<loteulte.‘) problem:1 preliminary report

Prog. Fish ( ult. 25 (3): 141 3 t'nuann 1.1Z., Paulik, G..I. and S. II. 11.1)iliik 1 9 65 - l'xperinienIal hexamiliasis in juvend cittiti

salmon tOncen .ltyncinht kisutc and steelhead trout (Salmi) vairdneri) trans. Amer. Fish. Soc.,94 (1): 53 .61

Vasiita)::, W. I. . Ituliler, I). R. and W. E. Shanks 1961: ('hemotherapy of hexamiliasis in rish Palasit. 47 (1): 81 6

ino, T , I 97(): I 1101 11g ) and Instopailtology tit hexamitiasis and an IPN-like disease of rainbow trout, 1 Tokyo Univ. Fish. 56 (1/2): 23 3()

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1.

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Translation of foreign-language titles

1. Textbook of fish diseases, second edition

2. . . quoted after . . .

3. Octomitus disease in trout and its treatment.

4. Sodium chloride baths in the treatment of diseased and weakened fishes.

5. Systematic control of hexamitiasis of the trout (in Italian).

6. Personal communication.

7. Health protection in pisciculture.

8. . . . quoted after . .

9. "Pitting disease:" An inexhaustible theme.

10. Supplementary observations regarding the "pitting disease."

11. Personal communication.

12. Handbook of trout rearing (in Danish).

13. Diseases and parasites of fishes.

14. Freshwater fishes as source of food and as environmental indicators.

15. Investigations of the ecology, species specificity, and variability of Hexamita semonis MOORE.

16. Diseases of fishes.

" 17. Investigations of Octomitus intestinaiis truttae.

18. Diseases of fishes; fourth edition.

19. New agent against Octomitus (Hexamita) (in Danish).

20. Personal communication.

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