Over the last 45 years, infectious diseases have negatively impacted shrimp aquaculture production worldwide, resulting in the loss of billions of dollars in revenue. Despite this challenge, annual shrimp aquaculture production increased from ~0.15 million metric tons (MMT) in the early 1980s to >7 MMT currently. Arguably, the largest driver of this increase was the availability of Specific Pathogen Free (SPF), genetically improved Pacific white shrimp, Litopenaeus vannamei and their subsequent introduction to Asia. In fact, global shrimp production was <1 MMT in the early 2000s when L. vannamei farming began in Asia, but quickly increased to ~3 MMT by 2006.
In 1984, the U.S. Marine Shrimp Farming Program (USMSFP) was formed to solve problems constraining the U.S. shrimp farming industry. At that time, L. vannamei had become the dominant farmed shrimp in the Western Hemisphere and the USMSFP committed resources to develop culture technologies for this species, including domestication. Infectious Hypodermal and Haematopoietic Necrosis Virus (IHHNV) was not lethal to L. vannamei, but it caused an economically significant disease where infected populations exhibited reduced growth and cuticular deformities. Thus, efforts to eradicate this pathogen from captive shrimp populations were needed to improve commercial production. In 1989, USMSFP members Oceanic Institute (OI) and the University of Arizona (UAZ) began developing the world’s first SPF population of L. vannamei which was free of IHHNV and other known pathogens at that time. In 1994, OI started the first family-based breeding program to improve growout performance and pathogen resistance of L. vannamei. During these early years, OI generated basic information about shrimp genetics and distributed SPF, selectively bred shrimp to the U.S. industry. By 2010, OI distributed >2.5 million shrimp, with U.S. broodstock suppliers playing a critical role in catalyzing L. vannamei farming in Asia. Selective breeding has continued to gain importance within the industry and L. vannamei farming now relies exclusively on selectively bred lines.
Developments in disease diagnostics and pathogen-challenge assays, as well as the implementation of biosecurity measures, have greatly aided selective breeding efforts and the shrimp farming industry as a whole. Histopathology has played a significant role in developing and maintaining SPF populations, as pathogen-specific diagnostic tools are typically developed after the disease etiology is known. In the late 1990s-2000s, molecular techniques for disease diagnostics were developed and the widespread use of these techniques, particularly PCR, has played a critical role in the implementation of biosecurity measures. Routine pathogen testing at commercial facilities has greatly reduced risks associated with the transfer of diseased shrimp. An effective disease-challenge assay for Taura syndrome virus was developed in the mid-1990s and was used to develop lines of L. vannamei that are highly tolerant to this pathogen. These lines were the first to be introduced to Asia and they continue to be the foundation for many selectively bred populations. Challenge assays continue to be used to develop lines of shrimp which are tolerant/resistant to a number of important shrimp pathogens.