Porcine Epidemic Diarrhea (PED)

Porcine epidemic diarrhea (PED) is a highly infectious gastrointestinal infection in pigs, characterized by acute symptoms of diarrhea and dehydration. It is caused by the porcine epidemic diarrhea virus (PEDV). The initial discovery of this disease dates back to 1971 in the United Kingdom, and it has subsequently spread to numerous countries globally. Over the past few years, both the geographical reach and severity of the epidemic have increased, leading to a significant mortality rate among nursing piglets. Consequently, PED has emerged as a pronounced concern within the swine industry.

Pathogen and Pathogenesis

PEDV stands as an enveloped RNA virus, with a genome measuring approximately 28 kilobases. Classified within the Alphacoronavirus genus, it exhibits substantial genetic resemblances to both the transmissible gastroenteritis virus (TGEV) and the porcine respiratory coronavirus (PRCV).

Fig. 1 The process of PEDV replication and assembly.¹

The primary mode of PEDV transmission is via the fecal-oral route. Upon entering a pig's system, PEDV infiltrates the small intestine and binds to specific receptors situated on the surface of intestinal cells. This interaction facilitates viral entry into the cells, where it reproduces through a budding process. The virus engenders extensive damage to the villi in the small intestine, resulting in malabsorption and the onset of watery diarrhea.

Fig. 2 Schematic diagram of the pathogenic process after PEDV invades the host.²

Signs and Symptoms

The clinical manifestations of PED differ depending on the age and immune condition of the pig. In the case of suckling piglets, the disease typically presents with abrupt onset of watery diarrhea, dehydration, anemia, and septic shock, often resulting in fatal outcomes. The feces may appear yellowish and emit a noticeably unpleasant odor. Additionally, affected piglets may display signs of depression, loss of appetite, and impaired growth.

In older pigs, clinical signs are usually less severe, with diarrhea being the predominant symptom. However, the disease can still have a major impact on growth performance and feed efficiency, resulting in economic losses for producers.

Fig. 3 Symptoms of piglets infected with PEDV.³

Diagnosis of PED

Diseases such as coccidiosis, transmissible gastroenteritis, and E. coli diarrhea can induce clinical symptoms closely resembling those of PED. Thus, precise PED diagnosis necessitates the identification of PEDV-specific nucleic acid, protein, or virus-specific antibodies. Leveraging various diagnostic methodologies, BioVenic employs a range of cutting-edge technologies to deliver dependable solutions for disease diagnosis.

• PCR: Rapid and highly sensitive, RT-PCR enables the detection of PEDV RNA in stool or intestinal samples.
• RT-LAMP: This technique stands out by discerning TGEV, PRV, PRRSV, and porcine pseudorabies virus, exhibiting heightened sensitivity compared to RT-PCR and ELISA methods.
• ELISA: Given the challenges in cultivating PEDV in vitro, ELISA proves valuable for identifying PEDV antigens or antibodies within serum or fecal samples.
• Lateral flow assay: We help customers develop rapid diagnostic test strips for PEDV antibody detection by coating nitrocellulose membranes with PEDV M protein antigen and anti-SPA polyantiserum. This approach facilitates rapid assessment.

Prevention and Control

BioVenic is steadfast in its ability to furnish clients with comprehensive solutions to preclude the introduction and diffusion of PED. Halting disease propagation mandates rigorous biosecurity protocols, encompassing regulated pig transportation, meticulous disinfection regimes, and controlled access to contaminated zones. Minimization of contact between infected and vulnerable pigs is imperative, necessitating the enforcement of stringent hygiene measures.

Vaccination stands as a proven and dependable strategy for PED prevention. Given the disease's swift onset, high mortality rates, and early age of occurrence, relying solely on active immunity often proves unviable. Consequently, PED vaccines are primarily administered to sows, furnishing robust piglet protection through colostrum-derived antibodies. Presently, the market offers a variety of PEDV vaccines, including inactivated and genetically modified attenuated variants.

Treatment

Unfortunately, there is no specific treatment for PED. Supportive care, including fluid therapy and electrolyte replacement, is essential to manage dehydration and restore pig health. Maintaining optimal nutrition and providing a clean and stress-free environment can also aid in the recovery of affected animals.

Prevalence of PED in the United States

The prevalence of PED within the United States has emerged as a pivotal concern for the swine sector. Its arrival in 2013 exerted a substantial impact on pig production, leading to substantial economic losses. During the initial years following its introduction, PED swiftly propagated throughout states, contributing to heightened piglet mortality. In response, the United States Department of Agriculture (USDA) and industry stakeholders have collaboratively instituted a comprehensive surveillance initiative to monitor PED prevalence and dissemination. Over time, the prevalence of PED has exhibited fluctuations across distinct regions of the nation. Occasional outbreaks have transpired, differing in intensity.

Nonetheless, it's imperative to acknowledge that PED remains an enduring hazard within the US, capable of resurfacing in susceptible swine populations. Thus, consistent vigilance and proactive disease management strategies stand as imperative necessities.

BioVenic is resolutely dedicated to advancing the comprehension of PEDV biology, epidemiology, and pathogenesis. Our active involvement includes aiding clients in devising tailored PED vaccines, creating precise diagnostic solutions, and extending drug development services as required. If this proposal strikes a chord with you, we wholeheartedly encourage you to promptly get in touch.

References

1. Lee, Changhee. "Porcine epidemic diarrhea virus: an emerging and re-emerging epizootic swine virus." Virology journal 12 (2015): 1-16.
2. Langel, Stephanie N., et al. "Host factors affecting generation of immunity against porcine epidemic diarrhea virus in pregnant and lactating swine and passive protection of neonates." Pathogens 9.2 (2020): 130.
3. Yang, Dan, et al. "Isolation and characterization of a variant subgroup GII-a porcine epidemic diarrhea virus strain in China." Microbial pathogenesis 140 (2020): 103922.