Porcine circovirus type 2 (PCV2) can be isolated from the intestines of pigs with diarrhea; however, infection is more commonly associated with multisystemic diseases, including postweaning multisystemic wasting syndrome.
Etiology and Pathogenesis of Circovirus-Associated Enteritis in Pigs
Porcine circovirus type 2 is a single-stranded DNA virus with a closed circular genome. The diarrhea and enteritis associated with PCV2 infection are believed to be one component of PCV2-assocated systemic disease rather than a separate clinical entity. PCV2 infection leads to immunosuppression with depletion of T- and B-lymphocyte populations and an increase in macrophages and giant cells in lymphoid tissues throughout the body. The lymphoid tissues impacted can vary among pigs, with some having severe lymphoid depletion in gut-associated lymphoid tissue (GALT), specifically Peyer's patches.
Clinical Findings of Circovirus-Associated Enteritis in Pigs
Epizootics of diarrhea in 6- to 9-week-old pigs with PCV2 have been reported, with morbidity of approximately 30% (1). Some affected pigs have decreased growth rates or appear stunted.
Diagnosis of Circovirus-Associated Enteritis in Pigs
Given the ubiquitous nature of porcine circovirus, PCR assays can be of limited diagnostic specificity; histological evaluation followed by immunohistochemistry (IHC) for PCV2 antigens within lesions is of higher diagnostic value. The gross lesions of systemic PCV2 infection include enlarged lymph nodes and variable generalized wasting. Microscopically, lymphoid depletion in multiple organs with replacement of lymphoid germinal centers by macrophages and multinucleated giant cells (granulomatous lymphoid depletion) can be observed. IHC applied to depleted Peyer's patches is expected to be strongly positive in cases of PCV2 enteritis.
Treatment and Control of Circovirus-Associated Enteritis in Pigs
Many effective PCV2 vaccines are widely used in the swine industry, and the development of PCV2 systemic disease, including enteritis, in a population is often thought to be more a measure of vaccine compliance (eg, failure in administration by large vaccine crews) than of vaccine efficacy.
Key Points
Porcine circovirus type 2 enteritis is one component of PCV2 systemic disease.
Given the ubiquitous nature of PCV2, most commercial herds are vaccinated.
Populations that are not vaccinated for PCV2 can experience severe outbreaks of disease.
For More Information
Baró J, Segalés J, Martínez J. Porcine circovirus type 2 (PCV2) enteric disease: an independent condition or part of the systemic disease?Vet Microbiol. 2015;176(1-2):83-87.
Segalés J, Allan GM, Franzo G. Circoviruses. In: Zimmerman JJ, Burrough ER, Karriker LA, Schwartz KJ, Zhang J, eds. Diseases of Swine. 12th ed. John Wiley and Sons, Inc; 2026:527-545.
References
Kim J, Ha Y, Jung K, Choi C, Chae C. Enteritis associated with porcine circovirus 2 in pigs. Can J Vet Res. 2004;68(3):218-221. https://pmc.ncbi.nlm.nih.gov/articles/PMC1142143/
