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How to prevent common shrimp diseases

January 22, 2020

The most practical way to prevent diseases or reduce the losses caused by diseases is to have good farm management and enhance shrimp immune system.

Shrimp diseases are the shrimp farming industry’s biggest concern. In Asia, diseases cost the shrimp industry billions of dollars annually (Shinn, et al., 2018). There are numerous diseases that cause this economic loss. This article will provide guidance to help you prevent shrimp diseases by going back to basics with farm management practices, biosecurity and shrimp health management.

Common shrimp diseases in Asia

No single disease can be definitively named the most severe, as this depends on the area, the timing of the outbreak and the season. Some of the most common shrimp diseases found in Asia are acute hepatopancreatic necrosis disease (AHPND), which is caused by bacteria; white-spot syndrome virus (WSSV), which is caused by virus; and Enterocytozoon hepatopenaei (EHP), the fungal microsporidian. The table below summarizes the symptoms of and prevention methods for each of these diseases.

Disease

Type

Symptoms

Prevention

Acute hepatopancreatic necrosis disease (AHPND)

AHPND mainly infects giant tiger prawn (Penaeus monodon) and whiteleg shrimp (Penaeus vannamei).  

Asian countries that have reported cases of AHPND include China, Vietnam, Malaysia, Thailand and the Philippines.

Bacterial infection with strains of Vibrio parahaem-olyticus.

Sudden, mass mortalities (up to 100%), usually within 30–35 days of stocking grow-out ponds (FAO, 2013; Hong et al., 2016; NACA, 2012).

AHPND targets gut-associated shrimp tissues and organs.

 

Environmental factors: Overfeeding, poor seed quality, poor water quality, poor feed quality, algal blooms or crashes (FAO, 2013; NACA, 2012).

Practices: Improvement of hatchery sanitary conditions and PL screening; good broodstock management; use of high-quality post-larvae; strict feeding rate control; and appropriate stocking density (OIE, 2019).

White spot syndrome virus (WSSV)

First detected in Taiwan in 1992, WSSV then spread to almost all Asian countries (Sanchéz-Paz, 2010).

Virus

Rapid reduction in food consumption; lethargy; high mortality (up to 100%) within 310 days of the onset of clinical signs; loose cuticle with white spots, most apparent on the inside surface of the carapace; in many cases, moribund shrimp display a pink to reddish-brown coloration due to the expansion of cuticular chromatophores and few, if any, white spots (FAO, 2012).

Screening of broodstock, nauplii, PL and grow-out stages; avoiding rapid changes in water conditions; avoiding shrimp stress; avoiding the use of fresh feeds, particularly crustacean; minimizing water exchange to prevent virus carriers from entering the pond; treating infected ponds or hatcheries with 30 ppm chlorine to kill infected shrimp and carriers; and disinfecting associated equipment (FAO, 2012).

Enterocytozoon hepatopenaei (EHP)

EHP is now endemic throughout China, Malaysia, Thailand, Indonesia and Vietnam, and is likely present in India.

Microspori-dian parasite

EHP does not cause mortality, but it does heavily limit growth.

This pathogen can be detected by using gene-based tools, such as polymerase chain reaction (PCR) and loop-mediated isothermal amplification testing of feces from broodstock (Newman, 2015).

Biosecurity in the hatchery (no live feed, disinfection, clean eggs); proper pond preparation (physically remove accumulated organic matter and treat pond bottoms); and proper pond management during the growth cycle (Newman, 2015).

Disease can be brought on-farm by water quality, wildlife, equipment, people, stock and feces. They can manifest as external parasites, viral infections, bacterial infections or fungal infections. Therefore, the most practical way to prevent disease and/or reduce the losses they lead to is to implement proper farm management practices and enhance the immune system of the shrimp.

Farm management and biosecurity

The production cycle of shrimp farming consists of four components: broodstock, hatchery, nursery and grow-out. According to the Food and Agriculture Organization of the United Nations (FAO), each of these components would require clean water, clean rearing facilities, clean feed, hygienic protocols, and dry-out and break-cycle practice.

Shrimp disease treatment is not easy; often, it is more complex than disease prevention. There is not one single solution that fixes all problems, but there are preventive measures that keep pathogens from filtering through shrimp ponds and that keep shrimp healthy. FAO recommends the following best practices in shrimp culture:

  • Choose the right shrimp genetics: i.e., specific pathogen-free (SPF) and high performers for high biosecurity systems. Better biosecurity in shrimp aquaculture begins with clean broodstock that supply eggs and nauplii for hatcheries. The broodstock, whether SPF or non-SPF, should be carefully sourced and certified. This is the first and most important step to take, as it could prevent the disease carriers from entering the culture system.
  • Keep pathogens out: Dry out facilities regularly; disinfect fill and exchange water; control feed; and prevent air and droplet contamination.
  • Biosecurity implementation: Limit the number of visitors (e.g., vehicles, humans, birds, other carriers) to a minimum.
  • Hygiene: Install hand-wash stations, foot baths and wheel washes or tire baths; put up warning signs; disinfect footwear before entering the facilities; and wear boots.

Enhancing the immune system of shrimp

It is natural for pathogens and bacteria to be present in shrimp ponds. They might not even lead to any diseases for healthy shrimp with strong immune systems. Therefore, it is important to take good care of shrimp gut health and work to bolster their immune systems. This can be achieved by using the right feed additives.

One example is supplementation with zinc and selenium. Zinc plays a key role in modulating immune function, resulting in shrimp with increased immune capabilities. Zinc also helps maintain skin integrity and speeds up wound-healing. In addition to zinc, selenium supplementation has been proven to promote shrimp growth and immune health.

An Alltech solution that has been effective in field trials in Southeast Asia is Aquate™ Defender.

What is Aquate Defender? It is a blend of organic trace minerals (zinc and selenium) and Saccharomyces cerevisiae yeast extract. This product has been shown to help improve performance and bolster the immune system, ultimately increasing the profitability of the farm.

Aquate Defender is the solution platform for aquaculture that provides a combination of technologies based on proprietary processes. Aquate Defender technologies help maintain a protective balance between your aquaculture species, their nutrition and the environment in which they live. This optimizes animal performance and helps maintain healthy populations.

Researchers at Alltech have developed the Aquate Defender range of nutritional solutions in partnership with our global customer base, using our three core technologies: peptide technologies, solid-state fermentation (SSF) and yeast fermentation. Aquate Defender is specifically designed to address producers’ concerns about the gastrointestinal stability of their animals. Aquate Defender solutions help producers as they work to achieve their animals' true potential and enhance their profitability.

About Aquate Defender:

  • Promotes good bacteria and builds defenses
  • Promotes gastrointestinal integrity and stability
  • Enhances nutrient utilization
  • Reinforces the function of the digestive system
  • Optimizes performance and profitability

Aquate Defender can improve the gut microvilli length, thus improving overall nutrient absorption, which can translate to growth performance (see Figure 1 below).

Figure 1: Shrimp gut morphology after feeding Aquate Component for 56 days

Intestinal morphology of shrimp fed with Aquate over 56 days

Intestinal morphology

Control

MOS 1.0

MOS 2.0

MOS 4.0

Microvilli length, um

0.92 + 0.03a

1.10 + 0.07ab

2.39 + 0.14e

2.15 + 0.09d

Source: Zhang et al., 2012


The results of a commercial trial at a Malaysia shrimp farm studying the whole production cycle showed that Aquate Defender helped improve overall profitability. The average bodyweight of the harvested shrimp increased 0.77 g, and FCR was reduced by 0.24. Overall, the yield per hectare increased 1.96 tons per hectare, and the return on investment (ROI) for the application of Aquate Defender was 7 to 1, compared to the control.

Figure 2: Results of a commercial trial of white shrimp showing improved performance with Aquate Defender

Alltech vs. control

Mean body weight (MBW)

+0.77 g

Average length

+1.23 cm

Production per pond

+979 kg

FCR

-0.24

Production per hectare

+1,960 kg

ROI

7.1:1


By improving food absoption and gut health, Aquate Defender increased bodyweight and production.

Source: A large farm in Malaysia (Sept. 2012)

Research and local field trials conducted in Malaysia and Indonesia have proven that, when Aquate Defender is used, the shrimp gut is heathier, with a longer and better villi structure that leads to better absorption. Farmers using Aquate Defender in their nutrition programs are experiencing more successful rates of shrimp culture. In several Asian countries, customers who have previously used Aquate Defender continue to use this product in their feeding programs. 

Conclusion

Although shrimp disease is the main challenge in shrimp culture, it can be prevented and overcome with good farm management practices and a strong biosecurity system. As an animal health and feed additives company, Alltech and its solutions can support you by improving the immune health of your shrimp and increasing both your productivity per hectare and, ultimately, your profitability.

 

References

A.P. Shinn, J. Pratoomyot, D. Griffiths, T.Q. Trong, N.T. Vu, P. Jiravanichpaisal and M. Briggs (2018). Asian Shrimp Production and the Economic Costs of Disease. Asian Fisheries Science, 31S (2018): 29-58.

FAO (2012). Species Fact Sheets: Penaeus monodon (Fabricius, 1798). In: FAO Fisheries and Aquaculture Department. http://www.fao.org/fishery/species/3405/en

FAO (2013). Report of the FAO/MARD Technical Workshop on Early Mortality Syndrome (EMS) or Acute Hepatopancreatic Necrosis Syndrome (AHPNS) of Cultured Shrimp (under TCP/VIE/3304), 2013. Hanoi, Vietnam, 25–27 June 2013. FAO Fisheries and Aquaculture Report No. 1053, Rome, Italy, 54 p.

HONG X.P., XU D., ZHUO Y., LIU H.Q. & LU L.Q. (2016). Identification and pathogenicity of Vibrio parahaemolyticus isolates and immune responses of Penaeus (Litopaneus) vannamei (Boone). J. Fish Dis., 39, 1085–1097.

NACA (2012). Report of the Asia-Pacific emergency regional consultation on the emerging shrimp disease: Early mortality syndrome (EMS)/acute hepatopancreatic necrosis syndrome (AHPNS), 9–10 August 2012. Published by the Network of Aquaculture Centres in Asia-Pacific, Bangkok, Thailand.

Newman, S. (2015). Microsporidian impacts shrimp production. Global Aquaculture Advocate. https://www.aquaculturealliance.org/advocate/microsporidian-impacts-shrimp-production/

OIE (2019). Manual of Diagnostic Tests for Aquatic Animals – 14/11/2019. https://www.oie.int/fileadmin/Home/eng/Health_standards/aahm/current/chapitre_ahpnd.pdf

Sánchez-Paz, A (2010). White spot syndrome virus: an overview on an emergent concern. Vet Res. 2010 Nov-Dec; 41(6): 43. Published online 2010 Feb 26. doi: 10.1051/vetres/2010015

Sritunyalucksanaa, K., l Intaraprasonga, A., Sa-nguanruta, P., Filerc, K., Fegand, D. (2011). Organic selenium supplementation promotes shrimp growth and disease resistance to Taura syndrome virus. Science Asia 37 (2011): 24-30. doi: 10.2306/scienceasia1513-1874.2011.37.024

Zhang, J., Liu, Y., Tian, L., Yang, H., Liang, G., Xu, D. (2012), Effects of dietary mannan oligosaccharide on growth performance, gut morphology and stress tolerance of juvenile Pacific white shrimp, Litopenaeus vannamei. Fish & Shellfish Immunology 33 (2012) 1027-1032. https://www.hinter.com.cn/Upload/pdf/en/4.pdf

 

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