Swine Enteric Coronavirus Disease (SECD)

Swine enteric coronavirus disease (SECD) is caused by porcine enteric coronaviruses (SECoV) that primarily affect the gastrointestinal tract of pigs, including porcine epidemic diarrhea virus (PEDV) and porcine delta corona virus (PDCoV). The disease has ravaged North America, causing economic losses to the swine industry in the United States and around the world. BioVenic has been engaged in the research of SECD for many years, has a unique understanding of it, and can provide customers with strong technical support.

Causes and Effects of SECD

PEDV and PDCoV belong to the genera Alphacoronavirus and Deltacoronavirus, respectively, of the family Coronaviridae. These two viruses disrupt the normal function of the gastrointestinal tract, causing severe enteritis and diarrhea. However, the exact mechanism by which these viruses cause disease is still being researched, but viral replication and immune responses are believed to play crucial roles.

Fig.1 The process by which swine enteric coronavirus enters host cells.^1,2

The impact of SECD on pig production is profound. Infected pigs may exhibit a range of clinical symptoms. In some cases, the disease can be fatal, especially in piglets. In addition, SECD can have a large economic impact due to increased veterinary costs, reduced reproductive performance, and reduced overall productivity.

Occurrence and Distribution

PEDV entered the United States in April 2013 and is widely disseminated. PDCoV was discovered in the United States in 2014. SECD has been reported in several US states since PEDV and PDCoV emerged in US swine herds. Monitoring and surveillance programs are essential for tracking the prevalence of SECD in the United States. Veterinary authorities, industry organizations, and research institutions collaborate to gather data and assess the impact of the disease. These efforts help in understanding the geographic distribution of SECD within the country and aid in the development of targeted control strategies.

Transmission

The transmission routes of SECD are divided into direct and indirect contact. Infected pigs shed viruses in feces, contaminating the environment and becoming a source of infection for susceptible animals. Direct contact between infected and susceptible pigs, i.e., fecal-oral transmission, is the predominant route of transmission.

Indirect transmission can occur through contaminated feed, water, equipment, and fomites. The highly resilient nature of SeCoVs allows them to survive in the environment for extended periods, increasing the risk of transmission. Therefore, implementing robust biosecurity measures and proper sanitation practices are crucial for preventing and controlling the spread of SECD.

Signs and Symptoms of SECD

SECD outbreaks may occur within 24 hours after exposure to SECoVs in pig herds. Diarrhea, often water and profuse, is one of the hallmark signs of the disease. However, specific symptoms may vary depending on the age and immune status of the pig.

• Piglets: Diarrhea, dehydration, decreased appetite, weight loss, 100% mortality.
• Nursery pigs: Mild to moderate diarrhea, accompanied by decreased growth performance, 5-15% mortality.
• Finisher pigs: Mild to moderate diarrhea, accompanied by decreased growth performance, 1-2% mortality.
• Sows: Mild symptoms or no symptoms, mortality rate <1%, miscarriage rate 5-10%.

It is important to note that not all infected pigs show clinical signs, making the detection and control of SECD challenging.

Diagnosis of SECD

The clinical symptoms of the disease are similar to other gastrointestinal diseases in pigs, and laboratory diagnosis is the only way to confirm SECD infection. As an experienced animal disease diagnostics CRO, BioVenic provides customers with precise SECD diagnostics development services, covering immunodiagnostics and molecular diagnostics, such as,

• PCR and real-time PCR, that detect viral genetic material in stool samples.
• ELISA, which detects antibodies against viruses in blood samples.

Treatment, Control, and Prevention of SECD

Treatment of SECD focuses primarily on supportive care and management strategies. In affected pigs, proper nutritional support and electrolyte balance are crucial. BioVenic recommends specific nutritional interventions and the use of antimicrobial agents on an emergency basis to control secondary bacterial infections. However, it is important to note that there is no specific antiviral treatment for SECD.

The prevention and control of SECD rely heavily on the implementation of strong biosecurity measures. Farm-level biosecurity protocols should include measures to prevent viruses from entering the farm and minimize their spread within and between farms. This includes:

• Ensure that the pigs you purchase are SECD-negative, isolate them for a week, and monitor them closely for signs of diarrhea.
• Keep pets such as dogs and cats away from swine areas.
• Keep the breeding environment clean and hygienic, and disinfect it regularly.
• Visitors are restricted from entering the farm, and the farmer also avoids visiting places that may be contaminated with SECD.
• Vehicles are not allowed on the farm. Before entering, it should be cleaned and disinfected if it cannot be avoided.

Vaccination has also emerged as a potential tool for SECD control. BioVenic provides custom vaccine development services to clients to enhance the immune response and provide protection against SECoV. Vaccination strategies focus on stimulating the piglet's active immune response.

BioVenic is making progress in preventing and controlling SECD by developing robust surveillance, accurate laboratory diagnostics, comprehensive biosecurity measures, and ongoing research and development. If you want to get more details, please feel free to contact us.

References

1. Yan, Quanhui, et al. "Swine enteric coronavirus: diverse pathogen–host interactions."International Journal of Molecular Sciences 23.7 (2022): 3953.
2. Image retrieved from Figure 3 "Attachment and entry of SeCoV." Yan, Quanhui, et al., 2022, used under [CC BY 4.0], the image title was changed to "The process by which swine enteric coronavirus enters host cells."