Years before travelers were required to quarantine or get polymerase chain reaction (PCR) tests for COVID-19, a research center rigorously required the same for shrimp.
In a seaside town in Iloilo, a birthing center for tiger shrimp doubles as a quarantine and PCR testing facility in efforts to keep out viruses and other pathogens that continue to devastate shrimp farms worldwide to the tune of billions of dollars yearly.
Pathogens are disease-causing agents of which there are plenty for shrimp. After releasing their eggs, the mother shrimp, called spawners, are tested for the white spot syndrome virus (WSSV), monodon baculovirus (MBV), infectious hypodermal and hematopoietic necrosis virus (IHHNV), yellow head virus (YHV), acute hepatopancreatic necrosis disease (AHPND), and the parasite Enterocytozoon hepatopenaei (EHP).
Because pathogens can be passed on from spawners to eggs, all the eggs are disinfected before they are given entry to the highly biosecure tiger shrimp hatchery of the Southeast Asian Fisheries Development Center Aquaculture Department (SEAFDEC/AQD).
Shrimp farms rely on hatcheries to produce shrimp postlarvae which are seeded into ponds, but keeping stocks free of viruses has been a constant challenge, especially because minute traces of pathogens at the hatchery can quickly escalate to an outbreak at the farm and cause millions of pesos in losses.
The SEAFDEC/AQD shrimp hatchery is at the centerpiece of the research center’s Oplan Balik Sugpo program launched in 2017 by its Chief, Dan Baliao, to boost the production of high-quality shrimp seeds and help revive the tiger shrimp industry in the Philippines.
The Philippines was once one of the top shrimp-producing countries in the world, harvesting 120,000 metric tons of tiger shrimp in 1992, worth US$ 300 million that year (US$ 571 million or Php 27.4 billion in 2020, accounting for inflation). Due to various shrimp diseases, the current national production is only roughly a third of the volume in 1992 at 42.45 thousand metric tons, worth Php 20.60 billion.
Saving shrimp eggs from infected mothers
At the frontlines of the battle against shrimp diseases is Dr. Leobert de la Peña, a scientist at SEAFDEC/AQD and head of its Research Division.
For the past two years, Dr. de la Peña noticed that an increasing number of wild-caught spawners, or shrimp mothers ready to lay eggs, delivered to the facility are already found to be infected with the notorious WSSV.
“In the mid-2000s, we found that between 0.3 to ten percent of shrimp in the wild are infected with WSSV. Recently, we found out that about 60 percent of the spent spawners that we have tested are infected,” he remarked.
While spawning stress may help make pathogens more detectable in PCR, the tenfold increase gives a rough estimation of the alarming spread of WSSV that leads to a significant loss for hatcheries.
Back in 2018, eggs from infected mother shrimp would be promptly chlorinated and disposed, all 200,000 to 1 million of them per brood. Each spawner costs P1,500 to P2,000 while eggs that successfully develop to postlarvae are 20 to 25 centavos per piece.
“Now we collect the eggs from each spawner and wash them with UV (ultraviolet) light-sterilized seawater, after which the washed eggs are then disinfected with iodine before being finally rinsed with sterilized seawater” said Dr. de la Peña.
The Food and Agriculture Organization of the United Nations recommends that shrimp eggs and nauplii (newly-hatched shrimp) must be washed and disinfected appropriately to prevent the transmission of viral, bacterial, fungal, and other diseases from broodstock.
Dr. de la Peña said eggs from infected and uninfected spawners are stocked separately but all continue to be tested for pathogens every five days until day-15 when the postlarvae are referred to as PL15. Postlarvae may be harvested for stocking into ponds between PL15 and PL20.
To date, disinfected eggs from several batches of infected spawners continue to be free from diseases, helping the experimental hatchery achieve a 19 percent survival rate (newly hatched shrimp to postlarvae) in 2020, more than double compared to only 9 percent in 2018 before egg disinfection was done.
Biosecurity measures
“Technologies in shrimp farming are constantly evolving, and we, as scientists, need to adapt depending on the current situation on the field,” stated Dr. de la Peña.
Due to the prevalence of shrimp diseases that can spread through contact with infected shrimp, water, and other surfaces, the SEAFDEC/AQD shrimp hatchery takes extreme measures to keep out pathogens.
Hand sanitizers and foot baths are provided at entry points so that staff and visitors can disinfect themselves as humans can also be a passive carrier of diseases.
Guests cannot be admitted into the facility for 48 hours if they previously visited an outside hatchery. Both staff and visitors who do enter are required to take a shower and use scrub suits and boots.
Both the water and air supply are UV-sterilized, while a 0.45-micrometer cartridge filter guards the aeration system. Wastewater from the facility is also disinfected before being discharged.
Chief Baliao also shared that SEAFDEC/AQD is further refining its protocols and technology for future collaborations with national agencies such as the Bureau of Fisheries and Aquatic Resources (DA-BFAR) and the National Fisheries Research Development Institute (NFRDI).
“SEAFDEC/AQD is only getting started,” he added. “There is still much to be done, but our scientists and technicians are hard at work at refining our protocols and technology for the benefit of our stakeholders.”