„Peracetic acid, an alternative to

fight fish ectoparasites!?“

T. Meinelt 1, D. Straus 2, S. Matzke 3, E. Sudova 4

1 WGL - Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Dept.

Aquaculture and Ecophysiology, Berlin, Germany2 USDA, Harry K. Dupree - Stuttgart National Aquaculture Research Center

Stuttgart, AR, USA3 Humboldt-University of Berlin, Germany 4 Research Institute of Fish Culture and Hydrobiology, Vodnany, Chech Republic

Structure

� Background of the PAA investigations

� About PAA

� Saprolegnia parasitica

� Ichthyophthirius multifiliis

� Life stage sensitivity to PAA

� Long term treatment of I. m.

� Mixed infection in Leuciscus idus

� Summary

� Chloramine-T

� Copper sulfate

� Florfenicol

� Formalin √

� Hydrogen peroxide √

� OTC

� Peracetic acid √? Water treatment? (Desinfection?)

� Potassium permanganate

� Salt (Sodium chloride) √

� Sodium hydroxide √

� Sodium monopersulfat

� Sodium percarbonate

� Unhydrated lime (Calcium oxide) √

Legislation, approved therapeutic agents.

Another European disaster

(Background of the PAA-investigations)

H3C C

O

OH

O O

H

H

O

H H

+ +H3C C

O

O OH

H3C C

O

OH

O O

H

H

O

H H

+ +H3C C

O

O OH

PAAC2H4O2 H2OH2O2

Disadvantages of PAA

• Thermodynamic instability (alteration of dosage).

• Modified effectiveness/toxicity in relation to water parameters such as

hardness, organic load, aeration etc.

• Corrosive.

• Caustic.

• Oxidizing effects, even at low temperatures.

• Very good water solubility.

• PAA-degradation produces acetic acid and hydrogen peroxide.

• The unspecific effects of PAA prevent the adaptation of microorganisms.

Advantages of PAA

Decrease of PAA (Wofasteril) concentration at 22°C,

Static, without aeration (doubled)

0

1

2

3

4

5

6

7

0 1 2 3 4 5 6 7 8

time [h]

ppm PAA

2 ppm

2 ppm (2)

3 ppm

3 ppm (2)

4 ppm

4 ppm (2)

5 ppm

5 ppm (2)

6 ppm

6 ppm (2)

Decrease of PAA (Wofasteril) concentration at 22°C, with aeration

0

1

2

3

4

5

6

7

8

0 1 2 3 4 5 6 7time [h]

ppm PAA

2 ppm

3 ppm

4 ppm

5 ppm

6 ppm

Decrease of PAA (Wofasteril) concentration at 30°C, without aeration

0

1

2

3

4

5

6

7

0 1 2 3 4

time [h]

ppm PAA

2 ppm

3 ppm

4 ppm

5 ppm

6 ppm

Selected results

Saprolegnia parasitica

Damages caused by Saprolegnia p.

(germ-carrier-investigations with D. rerio-eggs, germ-carrier (fungus media) = GY-agar Ø 10 mm infected

with S. p.)

Germ-carrier, GY-agar, 10 mmwith S. p. 14 d

Danio-rerio-embryos, 24 h, germ-carrier-test, no PAA-application

(negative control)

Danio-rerio-embryos, 24 h, germ-carrier-test, PAA-application, 3 ppm PAA, 2 h/d

Negative control

Treatment3 ppm PAA

(750 µL/100 L Wofasteril E400)2 x 1 h daily

Rainbow trout-eggs, fertilized

12

34

56

78

910

1112

0

100

200

300

400

500

600

Number of living eggs

days

control

2x10 min (4 ppm PAA)

2x1 h (3 ppm PAA)

12

34

56

78

910

1112

0

100

200

300

400

500

600

Number of infected eggs

days

eggs 2x1 h (3 ppm PAA)

2x10 min (4 ppm PAA)

control

Rainbow trout-eggs, fertilized,

Treated with Wofasteril E400,

3 ppm PAA (2 x 1 h) or 4 ppm PAA (2 x 10 min)

Number of

surviving eggs

Number of infected

eggs

Picture Daniel Hühn

Lifecycle of

Ichthyophthirius multifiliis

PAA to treat PAA to treat Ichthyophthirius multifiliisIchthyophthirius multifiliis

therontstheronts

Survival of I. multifiliis-theronts, treated with 0.2 ppm PAA

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

[n / 100 mL]

2 10 19 39 58 68 77 92 111 118 127 133 138 142 186

t [min]

Control

0.2 ppm PAA

Survival of I. multifiliis-theronts, treated with 0.3 ppm PAA.

Theronts are treatable even at very low PAATheronts are treatable even at very low PAA--concentrations! concentrations!

t [min]

0

5000

10000

15000

20000

25000

30000

35000

[n / 100 mL]

2 14 16 23 33 41 53 111 120

Control

0.3 ppm PAA

PAA PAA vs.vs. Ichthyophthirius multifiliisIchthyophthirius multifiliis

trophontstrophonts

Trophonts

Dose-response relationship between percent of dead and live trophonts or tomonts in the detached trophont toxicity experiment. 48 h static treatment with PAA (Meinelt et al., subm.).

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Control 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

mg/L PAA

Deadorlive trophonts and/ortomonts

live

dead

„Young“ trophonts (2.5 h)

0

100

200

300

400

500

600

700

Control 0.5 1 2 3

mg/L PAA

Live theronts per mL

Mean number of live theronts (± SD) produced from trophonts allowed to settle 2.5 h and then treated with 0, 0.5, 1, 2 or 3 mg/L PAA for 12 h. All exposed groups were significantly different from control (p<0.05).

12 h static treatment with PAA.Total incubation time 48 h.

„Old“ trophonts (tomonts)

0

200

400

600

800

1000

1200

1400

Control 0.5 1 2 2.5 3 0.5 1 2 2.5

0 2 2 2 2 2 4 4 4 4

Live theronts per mL

mg/L PAA

time [h]

Mean number of live theronts (± SD) produced from tomonts (24 h) treated with 0, 0.5, 1, 2, 2.5 or 3 mg/L PAA for 2 or 4 h. Total incubation time was 48 h.

Trophonts allowed to settle 24 h

„Dynamic“ 4 d-treatment

0

0,5

1

1,5

2

2,5

3

3,5

4

Gills Skin Fin

Mean infestation [n parasites]

Before PAA exposure

Control not PAA-exposed

After PAA exposure group (I)

After PAA exposure group (II)

PAA treated fish showed lower infestation with I. m. than the non-treated control fish as well as the I. m.-infected fish before PAA-exposure.

Investigations with wholesale ornamental fish. 600 fish (8 – 13 cm) from winter ponds, tanks volume = 1.2 m3, elevated mortality of 6 - 9 %/d

Diagnostics: Leuciscus idus [n = 20] Caudale, 40x, Chilodonella, Trichodina,

Epistylis, Ichthyobodo spp.

0 parasites

1-3 parasites

4-11 parasites

>11 parasites

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Chilodonella sp. Trichodina sp. Epistylis sp. Ichthyobodo sp.

0 parasites

1-3 parasites

4-11 parasites

>11 parasites

Results: Low infestion after threefold PAA-application

Leuciscus idus [n = 20] Caudale, 40x; 2.0 – 2.6 ppm PAA (6.5 mL WS), 1 x daily, 3 d,

Success: Chilodonella, Trichodina and Epistylis, moderate success with

Ichthyobodo; radical reduction of the losses.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Chilodonella sp. Trichodina sp. Epistylis sp. Ichthyobodo sp.

0 parasites

1-3 parasites

4-11 parasites

>11 parasites

No treatment success

Ichthyobodo (Apistogramma, L. idus)

Dactylogyrus sp. (Koi-carp)

Oodinium sp. (Ctenopoma weeksi)

PAA-sensitive species

� Pikeperch (Lucioperca)

� Tench

� Several ornamental species

At the end of the story…

Therapeutical success:

� Chilodonella sp. (L. idus)

� Trichodina sp. (L. idus)

� Epistylis sp. (L. idus)

� Gyrodactylus sp. (Guppy)

� Ichthyophthirius-theronts, early trophonts (in vitro)

� Saprolegnia parasitica (in vitro, in vivo)

Summary

� PAA is instable with a high / variable toxicity.

� Data about altering factors (DOC?) is insufficient.

� Toxicological data for PAA is insufficient.

� The therapeutic index for some fishes / juveniles is low.

� For some parasites (e.g. Chilodonella, Gyrodactylus,

Trichodina) short time exposures are successful.

� Some stages of Ichthyophthirius are treatable.

� But, hatch of trophonts / theront is not synchronous.

� Therefore a long term exposure is necessary.

� Concentrations must be kept constant.

� Additional research concerning PAA-tolerance of fish

species, parasite species and developmental stages,

application intervals and PAA-concentration is necessary.

„Peracetic acid, an alternative to

fight fish ectoparasites!?“

„Yes”

Particularly in Germany/EuropeN

Thank you for your attention!

The investigations were

supported by the Schreiner-

Stiftung, Germany

But!Nominal concentrationTap water without organic materialGreat differences between species and ages

Toxicity of PAA

Danio rerio (Embryos) 48-h-LC50 2,8 ppm PAA

Cyprinus carpio (Embr.) 24-h-LC50 6,1 ppm PAA

Sander lucioperca (ZV) 24-h-LC50 1,14 ppm PAA

2

2,5

3

3,5

4

4,5

5

5,5

6

72 96 120 144 168

hours

ppm PAA

Wofasteril E250

Wofasteril E400

Dilution test Saprolegnia parasitica

Water desinfection

� Sodium hypochloride