Shrimp farming and the worry of disease outbreaks.

Việt Nam•02/10/2023

STO - Due to the heavy rains and storms, the environmental factors in the shrimp ponds are easily affected, causing shock to the shrimp and leading to the outbreak of dangerous diseases such as white spot disease, white feces syndrome, and recently EHP (Episporin). This is also the main reason why the area and stocking density in this season are very low compared to the main season.

It can be seen that, while the disease situation in shrimp farming from the beginning of the year until now has not been large-scale or widespread, it has had a significant impact on the productivity and profits of farmers. However, according to the author's observations, except for some areas where farming was infected leading to reduced productivity due to harvesting small-sized shrimp or complete losses, most farmers believe that this year's farming was very easy to achieve high productivity thanks to fast shrimp growth and high survival rates. However, farmers still did not make a profit or even suffered losses, mainly because shrimp prices fell below the production cost.

Businesses producing breeding stock are strengthening inspections and disease control management to ensure the supply of healthy and disease-free breeding stock. Photo: TICH CHU

Currently, the downstream provinces of the Mekong Delta are entering the peak of the rainy and stormy season, making the management and care of shrimp ponds extremely difficult. Furthermore, dangerous diseases such as white spot disease, white feces syndrome, and especially EHP (Epidermolysis Bullosa) are still prevalent in most farming areas, making the off-season shrimp farming even more challenging. This is worrying because shrimp prices have recently started to rise, ensuring profitability for farmers, so some households are preparing to raise capital to stock their ponds. It is concerning because most water sources for farming areas no longer have sufficient salinity. Therefore, apart from households with water reserves from the previous farming season, most others rely on groundwater. Meanwhile, according to the recommendations of the Department of Agriculture and Rural Development of Soc Trang province, farmers should not use groundwater for shrimp farming because this water source often contains high levels of heavy metals and toxic gases, posing many risks to shrimp farming.

Over the past decade, the shrimp industry has been severely affected by several emerging and recurring diseases. One of the main ones is AHPND, also known as Early Mortality Syndrome (EMS), a bacterial disease. This disease has led to severe mortality rates (up to 100%) in whiteleg shrimp and tiger shrimp populations, causing significant economic losses to the shrimp farming industry. After EMS subsided, shrimp farmers continued to face white feces disease and EHP disease, for which there is still no effective prevention or treatment. Particularly in the last two years, EHP disease, though insidious, has become widespread and a constant concern for shrimp farmers, even those using high-tech methods.

Still worried about the EHP disease outbreak, on the morning of September 13th, Mr. Ho Quoc Luc - Chairman of the Board of Directors of Sao Ta Food Joint Stock Company - shared another alarming piece of information: "Recently, I heard about the emergence of a new bacterium causing disease in post-larval shrimp that is thousands of times more dangerous than the one causing EMS." To verify this information, Mr. Luc immediately contacted Mr. Nguyen Hoang Anh - Chairman of the Binh Thuan Shrimp Hatchery Association - and received confirmation that it was true and that there is currently no effective prevention or treatment for this new bacterium, causing sleepless nights for shrimp hatchery businesses. Upon hearing this information, Mr. Luc was quite concerned because if this disease were to break out in shrimp hatcheries, it would cause a serious shortage of shrimp larvae for farming areas.

According to my research, in late 2019, shrimp hatcheries in China discovered a new disease that commonly occurs in the post-larval stage (PL) of 6-12 days old. This new disease is called "translucent post-larvae disease" (TPD) or "glass post-larvae disease" (GPD) by Chinese scientists. TPD affects whiteleg shrimp in the post-larval stage (6-12 days old) with a mortality rate of over 90% within 24-48 hours of the first signs of abnormalities. Typical overall clinical signs include an empty gut without food and pale or colorless hepatopancreas, making the affected shrimp appear transparent like glass, hence the name glass post-larvae disease.

To proactively respond to extreme weather conditions and limit disease outbreaks to protect the shrimp population in the remaining 14,000 hectares of farmland, the Soc Trang Department of Agriculture recommends that farmers strengthen measures regarding: paying attention to the quality of shrimp fry, managing the pond environment, feed, and disease control. Accordingly, farmers need to increase monitoring of environmental factors, regularly track the water color in the ponds before and after rain, and adjust environmental factors to ensure stability and optimal conditions for shrimp farming during this period. Hopefully, scientists will soon find effective solutions for preventing and treating dangerous diseases so that shrimp farmers can confidently care for their shrimp at the end of the season and prepare for the new farming season in 2024.

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