MORE QUESTIONS & ANSWERS

ABOUT PARASITE-S

Using Parasite-S as a prophylactic treatment to reduce fungal infections in salmonid eggs

 

What is the potential of overdose? 

Not much. Info on rainbow trout indicates high tolerance (Marking et al., 1994). Several peer-reviewed articles indicate that salmonid eggs can be exposed to 1000 - 1500 ppm for periods of 30 to 60 minutes, every other day, with no adverse effects (Marking et al., 1994; Schreier et al., 1996; Waterstrat and Marking, 1995).

What is the overdose level for eggs? 

Rainbow tout have a lethal dose of 5000 ppm for 60 min and toxicity to eggs was not apparent at 5000 for exposures of 15 and 30 minutes (Marking et al., 1994).

Where did the 1670 ppm value come from? 

The original 1670 ppm value came form Piper et al, 1982, however, Marking et al. (1994) indicates that a 1000 ppm treatment for 15, 30, and 60 minutes inhibited saprolegnia infection and that 60 min exposures reduced the initial infection rate. Schreier et al. (1996) indicates that when fungal infection sets in, concentrations of 1000-1500 are needed to control further contamination.

Is the recommended 15 min enough time? 

The 1670 ppm for 15 minutes originally came form Piper et al, 1982. This number has since been revised to 1000-2000 ppm (Piper et al., 1992) but he still recommends a 15 min treatment. There may be some leeway based on the toxicity data found in Marking et al. (1994) which recommends that lower concentrations (1000 - 1500 ppm) should be used for longer periods of time (30-60 minutes).

Is there a reaction between Parasite-S and concrete? 

No information is readily available regarding interactions with concrete. However, formalin is often used for treating salmonids in concrete raceways and tanks. In addition, many older government hatcheries have concrete raceways and tanks and no adverse reactions have ever been reported

Buffering of Parasite-S, is there an effect of water quality? What buffering capabilities did the water have that was used to determine the 1670 ppm?

Piper et al (1992) suggests that formalin toxicity is affected by temperature and that fish (not eggs) become sensitive to formalin when temperatures above 10°C in this case concentrations should not exceed 167 ppm. No reference is made to water quality parameters such as hardness and alkalinity. However, they suggest that formalin can be effective in a wide range of applications from heath stacks to earthen ponds. Marking et al. (1994) had water quality parameters of (total hardness 138 ppm CaCO₃ ; alkalinity 105 ppm CaCO₃ ; pH 8.0; temp 12°C) however no mention was made about effects of water buffering capacity. Waterstrat and Marking (1995) reported water parameters of (total hardness 90 ppm CaCO₃ ; alkalinity 76 ppm CaCO₃ ; pH 7.7 ; and temp 12.2°C).

Is there a compatible food grade dye that can be used to trace the product? 

Aquatic eco-systems representative indicated that there should be no adverse reactions with Aquashade (a food grade dye) and formaldehyde.

When can you start treating eggs? 

Marking et al. (1994) suggests that green eggs were used for their experiment but does not comment on if this is an appropriate time to start or if there is a more appropriate time to start. Waterstrat and Marking (1995) also indicated that treatments began with Chinook salmon eggs the day after fertilization and stopped on day 35 (just before hatch).

When do you stop treating? 

Schreier et al. (1996) used formalin every other day for 15 minutes until hatch. Waterstrat and Marking (1995) indicated that with Chinook salmon they stopped treatment on day 35 (just before hatch).

What is the desired flow rate to maintain a consistent concentration during treatments? 

In health stacks, Schreier et al. (1996) determined that for a 15-minute exposure, a flow rate of at least 7.6 L/min was required to maintain a consistent formalin concentration. At this flow rate, the desired concentration is reached within 5 minutes and is quickly flushed out at 20-minutes when the treatment is finished.

Is there any way to measure formalin concentrations during treatments? 

Yes. Test kits are available which measure formaldehyde in solution. The kits measure from 0 – 100 ppm in 10 ppm increments. Measuring higher concentrations would require some dilution.

What dilution is 1670 ppm? 

1670 ppm is equivalent to a 600:1 dilution (1670 ppm = 1.67 ml/L Therefore the dilution would be calculated as 1000ml/1.67ml = 598 ~ 600:1)

Marking, L.L., Rach, J.J., Schreier, T.M., 1994. Evaluation of antifungal agents for fish culture. The Progressive Fish Culturist 56, 225-231. 

Piper, R.G., McElwain, I.B., Orme, L.E., McCraren, J.P., Fowler, L.G., Leonard, J.R., 1982. Fish Hatchery Management. U.S. Fish and Wildlife Services, Washington, D.C.

Piper, R.G., McElwain, I.B., Orme, L.E., McCraren, J.P., Fowler, L.G., Leonard, J.R., 1992. Fish Hatchery Management (Fifth edition). U.S. Fish and Wildlife Services, Washington, D.C.

Schreier, T.M., Rach, J.J., Howe, G.E., 1996. Efficacy of formalin, hydrogen peroxide, and sodium chloride on fungal-infected rainbow trout eggs. Aquaculture 140, 323-331. (internal reference # 80)

Waterstrat, P.R., Marking, L.L., 1995. Clinical evaluation of formalin, hydrogen peroxide, and sodium chloride for the treatment of Saprolegnia parasitica on fall Chinook salmon eggs. The Progressive Fish-Culturist 57, 287-291. (internal reference # 110)