Seafood Safety: Pathogen Detection in the Seafood Industry

Millions of people rely on seafood as a primary source of protein. However, seafood is responsible for a significant proportion of foodborne illnesses and outbreaks each year. Chemicals, metals, marine toxins, and infectious agents have been found in seafood, including bacteria, viruses, and parasites causing symptoms that range from mild stomach irritation to life-threatening illnesses.

How does seafood become contaminated with pathogens?

Certain seafood products inherently carry higher risks due to several factors, including their origins, environmental conditions, feeding habits, harvesting season, and the methods employed in their preparation and serving. Pathogens can enter the seafood supply chain at different stages, from harvesting and processing to transportation and distribution.

All types of seafood are vulnerable to contamination originating from the marine environment, either on their surface or within tissues. For example, bivalve mollusks, such as clams and oysters, filter significant volumes of seawater during their feeding process. This makes them particularly prone to accumulating and concentrating pathogenic microorganisms, like Vibrio, which are naturally present in harvesting waters.

Pathogen contamination in seafood can also occur when growing areas become tainted with human sewage. Seafood-associated illnesses linked to polluted waters have been attributed to calicivirus, hepatitis A, and Salmonella enterica Typhi. Sources of seafood contamination encompass activities like overboard sewage discharge into harvesting areas, unauthorized harvesting from sewage-contaminated waters, and sewage runoff from inland areas following heavy rains or flooding.

Furthermore, seafood is susceptible to contamination during handling, processing, or preparation. Contributing factors include inappropriate storage and transportation temperatures, contamination by infected food handlers, and cross-contamination from contact with contaminated seafood or seawater. Furthermore, seafood is often consumed raw or prepared in ways that may not effectively eliminate harmful organisms, unlike other foods such as meat and poultry that are typically fully cooked.

Common pathogens associated with seafood-borne illnesses

Bacteria

Vibrio

Vibrio are Gram-negative bacteria prevalent in marine environments and peak in warm waters. The Vibrio genus comprises 30 species, with at least 14 recognized as pathogenic to humans. Vibrio parahaemolyticus and Vibrio vulnificus are the primary culprits of seafood-borne disease, causing symptoms ranging from watery diarrhea, abdominal cramps, and nausea to severe infections, particularly in individuals with liver disease.

Salmonella

Salmonellae are Gram-negative bacilli with approximately 2,500 serotypes. Seafood-associated outbreaks have been caused by fish, shrimp, oysters, and clams, and incidents of Salmonella infection are more prevalent among infants and the elderly during summer and early fall. Historically, sewage contamination of shellfish harvest beds has led to large shellfish-associated outbreaks of Salmonella Typhi infections.

Shigella

Shigella species are Gram-negative bacilli that manifest diverse clinical presentations, from watery stools to severe symptoms like fever and bloody diarrhea. Due to their low infectious dose, Shigella are highly communicable and have the potential to contribute to large outbreaks. Seafood contamination may occur when harvested from sewage-contaminated waters. While Shigella can survive outside the host, they are killed readily by cooking.

Clostridium botulinum

Clostridium botulinum is an anaerobic, spore-forming Gram-positive bacillus that produces potent neurotoxins. Rare but serious, botulism results from ingesting food contaminated with these toxins and causes weakness and paralysis. If paralysis progresses to the respiratory tract, individuals may require ventilatory support. Seafood-associated cases often stem from home-canned foods and fermented or salted seafood.

Staphylococcus aureus

Staphylococcus aureus produces enterotoxins causing acute gastrointestinal illness. The incubation period is short, with the onset of nausea, vomiting, and mild diarrhea occurring within 1 to 6 hours after ingestion of contaminated food. S. aureus contamination often results from improper food handling during preparation.

Viruses

Norovirus

Norovirus, a compact RNA virus within the caliciviruses, leads to illness marked by diarrhea, vomiting, nausea, and abdominal cramps. The virus spreads through contaminated food or water with low infectious doses and high attack rates, and persists in the environment, often causing outbreaks in confined settings. Norovirus is associated with seafood contamination in sewage-contaminated waters and has been linked to gastroenteritis outbreaks.

Hepatitis A

Hepatitis A causes the most severe viral infection associated with seafood consumption, manifesting as fever, malaise, jaundice, anorexia, and nausea. Transmission occurs through the fecal-oral route, and foodborne outbreaks are often linked to oysters and clams. The virus's heat resistance necessitates proper cooking to eliminate live viruses, emphasizing prevention strategies focused on controlling contamination before food preparation.

Parasites

Helminths

Large, worm-like parasites known as helminths pose a risk to raw seafood consumption. Clinical manifestations range from no symptoms to mild or chronic gastrointestinal issues, allergic reactions, and rare invasive diseases. Although helminths are present naturally in marine and fresh waters, they rarely cause reported outbreaks due to their inability to multiply in food, long incubation periods, and likely underdiagnosis. Freezing and cooking effectively kill helminths.

Protozoa

Protozoa, an uncommon cause of foodborne illnesses, are primarily waterborne. Giardia spp. is a notable protozoan associated with seafood-related diseases, with infections causing abdominal pain, anorexia, and prolonged watery diarrhea.

The importance of real-time, automated pathogen monitoring

Real-time, automated pathogen monitoring stands as a critical advancement in ensuring the safety of seafood. This technology addresses the limitations of traditional monitoring methods, offering a more dynamic and proactive approach to identifying and mitigating potential risks associated with pathogen contamination.

One of the primary advantages of real-time monitoring is its ability to provide swift and automated results. Traditional laboratory analyses often involve time-consuming processes, leading to delays in identifying contamination issues. In contrast, real-time monitoring systems continuously collect and analyze data, enabling the early identification of deviations from established safety standards. This early warning system allows for timely correction actions, preventing the spread of contamination. Moreover, real-time monitoring facilitates a more thorough understanding of the factors influencing pathogen presence, aiding in the development of targeted preventive measures and industry best practices.

Beyond its role in protecting public health, real-time, automated pathogen monitoring streamlines regulatory compliance for seafood producers. The ability to generate and maintain comprehensive, real-time records ensures that industry players adhere to stringent quality and safety standards. This not only fosters consumer confidence but also positions the seafood industry as a reliable source of safe and high-quality products.

Conclusion

As the demand for seafood continues to rise, maintaining the safety and quality of these products is paramount. By adopting advanced pathogen detection techniques, the industry can safeguard the well-being of consumers and adhere to more rigorous regulatory standards. As we move forward, continued research and collaboration will be crucial to staying ahead of emerging pathogens and ensuring a resilient and secure seafood supply chain.

About Kraken Sense

Kraken Sense develops all-in-one pathogen detection solutions to accelerate time to results by replacing lab testing with a single field-deployable device. Our proprietary device, the KRAKEN, has the ability to detect bacteria and viruses down to 1 copy/mL. It has already been applied for epidemiology detection in wastewater and microbial contamination testing in food processing, among many other applications. Our team of highly-skilled Microbiologists and Engineers tailor the system to fit individual project needs. To stay updated with our latest articles and product launches, follow us on LinkedIn, Twitter, and Instagram, or sign up for our email newsletter. Discover the potential of continuous, autonomous pathogen testing by speaking to our team.

References

Iwamoto, M., Ayers, T., Mahon, B. E., & Swerdlow, D. L. (2010). Epidemiology of seafood-associated infections in the United States. Clinical microbiology reviews, 23(2), 399–411. https://doi.org/10.1128/CMR.00059-09