Running Mortality Syndrome (RMS)
Scientific Classification: Idiopathic Multi-Factorial Mortality Complex of Andhra Pradesh
రొయ్యల రన్నింగ్ మోర్టాలిటీ సిండ్రోమ్ (RMS / డైలీ మోర్టాలిటీ) నివారణ
ఆంధ్రప్రదేశ్ లోని భీమవరం, నెల్లూరు ప్రాంతాల్లో DOC 35 నుండి 70 రోజుల మధ్య రోజూ కొన్ని రొయ్యలు చనిపోయే RMS నివారణ సమగ్ర పద్ధతులు.
1. Clinical Overview
Running Mortality Syndrome (RMS) is a distinct clinical manifestation predominantly documented in intensive Litopenaeus vannamei farming across coastal Andhra Pradesh (West Godavari, Krishna, Bapatla, and Nellore districts). Unlike acute WSSV or AHPND which cause total pond wipeout in 72 hours, RMS is characterized by continuous, low-grade, persistent daily mortalities (10 to 50 dead shrimp per check tray or 5–15 kg/day) persisting over 15 to 30 days between DOC 35 and DOC 70, gradually eroding 30% to 60% of crop biomass.
2. Etiology & Transmission Dynamics
Complex interaction involving opportunistic secondary bacteria (Vibrio campbellii, V. parahaemolyticus), low-virulence viral agents, benthic soil toxicosis ($H_2S$), and micro-mineral depletion ($K^+, Mg^{2+}$).
Non-specific horizontal transmission; cannibalism of weak moribund shrimp at the pond bottom.
Gradual onset; typically emerges post-DOC 35 as shrimp biomass crosses 2,000 kg/acre and feeding rates peak.
Cumulative mortality 25% to 55% over a 3-week period.
3. Gross Pathology & Field Signs
A. Pond Dike & Aerator Observations
- Persistent presence of 10 to 30 dead shrimp on feeding trays every single inspection, morning and afternoon.
- Dead shrimp collected in bottom sludge check nets showing severed antennae, missing pleopods, and eroded uropods due to cannibalism.
- Shrimp swimming aimlessly along dikes during mid-day without schooling behavior.
B. Check Tray Pathology
- Feeding drops moderately (15% to 25%), but shrimp continue to consume a portion of feed while mortalities continue uninterrupted.
- Fecal matter present in trays but appears watery, segmented, and pale.
- High percentage of dead shrimp exhibit empty stomachs and retracted hepatopancreas.
C. Gross Dissection Findings
- Hepatopancreas is shrunken, dark reddish-brown, with loss of tubular structure and reduced lipid droplets.
- Intestinal tract shows intermittent empty patches (discontinuous gut filling).
- Abdominal musculature appears opaque, whitish, or displays focal necrosis near the 5th and 6th abdominal segments.
4. Microscopic & Molecular Laboratory Diagnosis
Squash mount of HP reveals hemocytic infiltration and mild to moderate tubular atrophy without classic ATM vermiform structures.
Degeneration of tubular epithelial cells accompanied by high secondary bacterial colonization in necrotic areas.
H&E staining shows multifocal melanization, hemocytic enteritis, and focal necrosis in lymphoid organ spheroids.
PCR tests for WSSV, IHHNV, IMNV, and EHP often return negative or low-copy positive, confirming an environmental/synergistic etiology.
5. Water Quality Trigger Thresholds
| Parameter | Critical Danger Threshold | Biological Impact on Shrimp |
|---|---|---|
| Pond Bottom Redox Potential (Eh) | < -150 mV (Anaerobic black soil) | Causes benthic hydrogen sulfide ($H_2S$) leakage which suffocates bottom-dwelling shrimp. |
| Potassium (K+) to Salinity Ratio | < 10:1 mg/L per ppt salinity | Causes neuromotor exhaustion and inability to complete ecdysis molting. |
| Dissolved Oxygen at Pond Bottom | < 3.0 mg/L | Forces shrimp into hypoxic stress where basal immunity collapses. |
6. Differential Diagnosis (Rule-Out Matrix)
Key Distinguishing Features: AHPND causes sudden catastrophic mortality (> 80% in 3 days) at DOC 10–35 with hard, pale, shrunken HP. RMS causes chronic low-grade daily mortalities over weeks at DOC 35–70 with dark reddish HP.
Key Distinguishing Features: WSSV causes distinct white spots on carapace and 100% kill in 3–5 days. RMS shows zero white spots and mortalities drag on daily.
7. CAA Statutory Biological Protocol
100% Antibiotic-FreeBenthic Soil Oxidation & H2S Neutralization
Reduce feed by 30% for 3 days.
Apply Next Sludge @ 1 Kg/Acre + Next Converter @ 3 Litres/Acre across bottom aerators.
Systemic Pathogen Suppression with Next Viro Nill
Administer Next Gut @ 15 ml/kg of feed in morning and noon meals.
Broadcast Next Viro Nill @ 1.5 Litres/Acre at 05:00 PM.
Osmotic & Mineral Balance Restoration
Top-dress Next Min @ 15 g/kg feed with sea binder for 7 days.
Apply Next Min @ 5 Kg/Acre to pond water at night.
8. Clinical Frequently Asked Questions
Q: Why does RMS persist for weeks without killing the entire pond at once?
RMS is caused by chronic environmental degradation (bottom black soil, $H_2S$, micro-mineral deficits) rather than an acute lethal viral pathogen. Only shrimp that undergo molting or encounter severe hypoxic bottom patches succumb each day, resulting in a continuous "running" daily mortality pattern.
Q: Does chemical potassium permanganate (KMnO4) stop RMS?
No. KMnO4 temporarily oxidizes organic matter in water but crashes the beneficial diatom bloom, creating massive stress and worsening mortality within 48 hours. The only sustainable cure is biological sludge digestion (Next Sludge) and systemic mineral restoration (Next Min).
Scientific Citations & Institutional References
- Alavandi, S. V. et al. (2019). Investigation on "Running Mortality Syndrome" (RMS) of Litopenaeus vannamei in shrimp farming areas of Andhra Pradesh. ICAR-CIBA Technical Bulletin, 14, 1–28.
- Pradeep, B. et al. (2012). Emerging viral diseases of penaeid shrimp in Asia: review and perspectives. Indian Journal of Virology, 23(2), 123–133.
- Flegel, T. W. (2012). Historic emergence, impact and current status of shrimp pathogens in Asia. Journal of Invertebrate Pathology, 110(2), 166–173.