Post reply

Reply to the message by Dr Emmanuel PARLIER

Name:

E-mail: (optional, won't be displayed directly)

Leave this field empty:

Remember me (cookie)

Category:

Subject:

Once this topic has been resolved, type "T" into this field for true. (For administrator only)

Tags: (optional, separated by comma)

Formatting help

skip to input

format text bold: [b]bold text[/b]
format text italic: [i]italic text[/i]
insert hyperlink: [link=http://example.com/]link text[/link] / [link]http://example.com/[/link]
set text color: [color=#rgb]colored text[/color]
font size: [size=small]small text[/size]; [size=large]large text[/size]
insert list: [list][*]list item[/list]
insert image: [img]http://example.com/image.jpg[/img]; left: [img=left]http://example.com/image.jpg[/img]; right: [img=right]http://example.com/image.jpg[/img]; thumbnail: [img=thumbnail]http://example.com/image.jpg[/img]; thumbnail left: [img=thumbnail-left]http://example.com/image.jpg[/img]; thumbnail right: [img=thumbnail-right]http://example.com/image.jpg[/img]
upload image: upload image ...

Message:

> Dear Warren,
> 
> Following your observation of mortality in tilapia fry at the hatchery in Bangladesh during March, and the subsequent disappearance of symptoms with increasing water temperature, your hypothesis of a possible ISKNV (Infectious Spleen and Kidney Necrosis Virus) involvement is scientifically plausible.
> 
> Current scientific and institutional evidence confirms that ISKNV is thermosensitive, and that controlled elevation of water temperature is an effective mitigation measure in hatchery conditions, particularly for fry and early juveniles.
> 
> Below is an operational thermal management protocol applicable to tilapia fry, based on peer-reviewed studies and international guidelines.
> Recommended Thermal Treatment Protocol (Tilapia Fry)
> 
> 1. Target Temperature
> 32–34 °C
> Do not exceed 34 °C, especially for fry <1 g
> Scientific rationale: ISKNV replication is optimal between 22–28 °C and significantly inhibited above 30–32 °C.
> 
> 2. Temperature Increase
> Increase gradually: +1 °C every 6–8 hours
> Avoid rapid heating to prevent:
> thermal shock,
> physiological stress,
> secondary immunosuppression.
> 
> 3. Treatment Duration
> Maintain 32–34 °C for 5 to 7 consecutive days
> Monitor daily:
> mortality,
> feeding behavior,
> abnormal swimming or lethargy.
> 
> 4. Cooling Phase
> Decrease temperature slowly: –1 °C every 12 hours
> Return to standard rearing temperature (28–30 °C).
> 
> Essential Environmental Conditions During Treatment
> 
> Parameter
> Recommended value
> Dissolved oxygen
> > 6 mg/L
> Unionized ammonia (NH₃)
> < 0.02 mg/L
> Nitrite (NO₂⁻)
> < 0.1 mg/L
> Stocking density
> Reduce by 20–30% if possible
> Feeding rate
> Reduce by ~30%
> 
> ⚠️ At temperatures above 32 °C, oxygen demand increases by approximately 30–40%.
> 
> Limitations and Important Notes
> This method is not a curative antiviral treatment.
> Effectiveness is reduced if fish are already in advanced disease stages.
> Surviving fish may remain asymptomatic carriers.
> Relapse may occur when temperature returns to 28–30 °C.
> ➡️ Thermal treatment should be considered a risk-management and mortality-reduction strategy, not an eradication measure.
> 
> PCR analysis for ISKNV on spleen and anterior kidney tissues.
> 
> Biosecurity
> Strict isolation of affected batches.
> Disinfection of equipment (iodophors or chlorine-based disinfectants).
> 
> Long-term prevention
> Use of ISKNV-screened broodstock.
> Minimum 21-day quarantine for new fish.
> Avoid mixing batches of different origins.
> 
> Scientific and Institutional References
> FAO (2020).
> Tilapia Lake Virus and Megalocytivirus (ISKNV): Emerging diseases in tilapia aquaculture.
> Food and Agriculture Organization of the United Nations.
> Reliability: International institutional source
> https://www.fao.org/3/ca9209en/ca9209en.pdf
> WOAH (World Organisation for Animal Health, formerly OIE) (2023).
> Infectious spleen and kidney necrosis virus – Aquatic Manual.
> Reliability: International regulatory reference
> https://www.woah.org/en/disease/infectious-spleen-and-kidney-necrosis-virus/
> Dong, H. et al. (2017).
> Effect of water temperature on mortality and viral replication of ISKNV in tilapia.
> Aquaculture, 468, 70–76. Elsevier.
> Reliability: Peer-reviewed scientific journal
> https://doi.org/10.1016/j.aquaculture.2016.10.017
> Subramaniam, K. et al. (2016).
> Megalocytivirus infection in farmed tilapia.
> Diseases of Aquatic Organisms, 119, 17–28.
> Reliability: Peer-reviewed epidemiological study
> https://doi.org/10.3354/dao02970
> 
> Please note that PCR confirmation is essential before formally concluding on ISKNV presence.
> If required, I can provide:
> a Standard Operating Procedure (SOP) adapted to your hatchery system (RAS or flow-through),
> a HACCP-compatible biosecurity plan,
> or a short technical brief for local staff training.
> 
> Kind regards,
> Dr Emmanuel Parlier, PhD
> Aquaculture & Aquatic Animal Health Expert
> Parlier Environnement SAS