A deeper analysis shows that the impact on costs goes beyond increases in feeding the shrimp.
Shrimp aquaculture has been a pillar of economic growth in several Asian countries, yet beneath the surface lurks a formidable threat, Enterocytozoon hepatopenaei (EHP). Unlike pathogens that cause visible mass mortalities, EHP operates quietly, gradually undermining farm profitability through less obvious but significant impacts on shrimp growth and yield.
The nature of EHP and its impact
EHP is a microsporidian parasite that targets the shrimp hepatopancreas, a key organ responsible for digestion and nutrient absorption. Rather than causing immediate death, EHP infections primarily result in stunted growth and large size variations at harvest. These translate directly into economic losses, as farmers deliver smaller shrimp, often missing premium market opportunities.
Economic consequences
The chronic presence of EHP leads to several detrimental outcomes for shrimp farmers, which include:
• Extended crop cycles which increase feed and labour costs.
• Higher feed conversion ratios (FCRs), demanding more input per cycle of shrimp production.
• Uneven shrimp size and shrimp not reaching target market size complicate marketing and reduce overall sales value.
• Additional investments in diagnostics, feed supplements, and pond management further strain financial resources
Quantitative assessments, particularly from major production zones, such as Andhra Pradesh, reveal economic losses due to EHP which may exceed 20-30% of typical profit margins. This scale of loss sums up to hundreds of millions of rupees annually, threatening both individual farm viability and resilience within the broader industry.
Enhanced management strategies for controlling EHP
Effectively managing EHP requires a comprehensive approach that integrates preventive, regular monitoring, and remedial measures tailored to the unique challenges this pathogen presents. Since EHP is a chronic resilient parasite that rarely causes acute mortality, early detection and proactive management are crucial to minimise economic losses.
Pond preparation and biosecurity
Steps taken to ensure proper pond preparation and biosecurity include:
• Thorough elimination of residual pathogens and minimising infection risks during pond preparation.
• Complete drying and sun exposure during pond dry-out periods to help reduce pathogen load in the sediment.
• Application of lime and appropriate disinfectants to neutralise spores and improve pond water quality.
• Use of biosecurity protocols such as restricting farm access, controlling equipment sharing, and adopting other inputs to minimise contamination risks.
• Management of water source like using filtered or treated water to reduce introduction of EHP spores and other pathogens.
Regular health monitoring and early diagnosis
EHP Infections often remain undetected until harvest, hence, routine monitoring is indispensable. Measures taken include:
• Visual assessments for growth reduction and uneven size distribution, which serve as initial warning signs.
• Scheduled sampling of shrimp hepatopancreas tissues for microscopic observation (wet mount) and molecular testing (PCR/RTPCR) helps in early detection. (Table 1).
Nutritional and functional feed interventions
Nutritional intervention is increasingly recognised as a key component in managing EHP and reducing its economic impact on shrimp farming. Functional feeds not only fulfil the nutritional requirements of shrimp but also deliver bioactive compounds that modulate immunity, enhance gut health, and improve resilience against pathogens.
Recent advances have demonstrated the potential of targeted feed formulations such as Nutriva Plus (Growel, India), which incorporates bioactive ingredients designed to reduce pathogen pressure and improve host defence mechanisms. The functional components of this feed operate through multiple mechanisms, which include:
• Strengthening of intestinal integrity reduces the adverse effects of pathogen-derived toxins.
• Immune system modulation helps to maintain shrimp in a heightened state of readiness against infection.
• Direct antimicrobial action, with certain compounds capable of inactivating or disabling pathogens.
• Improved feed intake and nutrient utilisation, ensuring effective delivery of health-supportive compounds.
When integrated with husbandry measures such as water quality management, stocking density based on carrying capacity of the pond, and strict biosecurity protocols, functional feeds like Nutriva Plus represent a practical approach to mitigating EHP-related losses.
Water quality management
The shrimp pond with ideal water quality parameters (Table 2) and regular applications of water and soil probiotics, for bioremediation will minimise stress and pathogen proliferation.
Managing EHP outbreaks in Andhra Pradesh
Recent times have seen shrimp farmers across key districts of Andhra Pradesh grappling with escalating challenges from EHP infections, resulting in significant production decline and economic losses.
Mapping the impact
We conducted a comprehensive questionnaire-based survey over the past year across Krishna, East Godavari, and West Godavari districts—major shrimp farming regions of Andhra Pradesh. The survey covered more than 145 shrimp farms, including both healthy and EHP-affected farms, each operating under the region’s standard 2–4 crop annual cycle. The study relied on the Growel 360° app to capture and organize all pond-level data.
EHP infection status
Of the 145 farms surveyed, 93 (64%) showed signs of EHP infections during the year. Only 52 farms (36%) remained unaffected, suggesting either successful implementation of preventive measures or just limited exposure to microsporidium. The high infection rate underscores the urgent need for coordinated disease management and biosecurity protocols across the region.
Categorising severity of infection
Based on field observations, EHP-affected ponds were classified into three categories:
- Healthy shrimp: No visible signs of infection, optimal growth, and feed conversion.
- Moderate EHP: Shrimp showed signs of stunted growth, moderate size variation and reduced feed efficiency.
- Severe EHP: Severe growth retardation, high mortality, high size variation and significant economic loss.
Distinct impacts of EHP on production costs
In farms affected by EHP, pond preparation has become more intensive and costly. Activities such as tillage and soil preparation with tractors, bleaching, and liming critical for disinfection, are now performed more rigorously to eliminate residual spores and prevent reinfection.
Our study revealed a 15% to 28% increase in pond preparation costs depending on the severity of EHP in infected ponds compared to healthy ones. This escalation is driven by the need for enhanced cleaning protocols between crop cycles, often requiring additional labour and materials.
More rigorous diagnostic approach for EHP detection
To assess the presence of EHP, a structured diagnostic
protocol was followed:
• Preliminary observations: Field technicians examined shrimp for visual signs of EHP, including growth retardation, pale hepatopancreas, white faeces, and poor feed conversion.
• Wet mount microscopy: Suspected samples were screened under a wet mount to detect microsporidian spores in hepatopancreatic tissue.
• Confirmation with RT-PCR: Molecular confirmation was performed using reverse transcriptase polymerase chain reaction (RT-PCR), ensuring high sensitivity and specificity in detecting EHP DNA.
Using a classification of pond health status based on RT-PCR results and cycle threshold (CT), ponds were categorised into three health status groups.
• Healthy pond: No detectable EHP infection.
• Moderately infected ponds: CT > 25
• Highly infected ponds: CT < 25
This classification enabled targeted analysis of production costs and disease impact across varying infection levels.
Comparison of economic losses
This was studied with direct costs between the non- EHP-infected farms and EHP-infected ponds, as shown in Table 4. We also analysed the impact on costs, ranking them as in Table 5.
Conclusion
In this article, we demonstrate the cost impact per kg shrimp with EHP infections and its subsequent influence on WFD incidences. In moderately and severely infected ponds, the cycle is not profitable with harvests of size 100/kg. The cycle is profitable when the cycle continues to harvest size of 60/kg, aided by higher selling prices. Effective EHP control benefits farmers reducing cost of production thus increasing the profit margins for farmers.
Shrimp culture practices require the adoption of effective methods for pond preparation and biosecurity, regular health monitoring, early disease diagnosis, nutritional and functional feed interventions as well as water quality management.
This article was first published in Aqua Culture Asia Pacific November/December p40–43. https://issues.aquaasiapac.com/view/717436716/42/
