In October 2006, the American Association of Swine Veterinarians developed a case definition¹ to describe porcine circovirus-associated disease (PCVAD). The following summary was adapted from that case definition.

PCVAD is a broad categorization of multi-systemic diseases. PCVAD can be subclinical (no obvious clinical signs in the herd) or include one or more of the following signs concurrently:

• Multi-systemic disease with weight loss (formerly known as PMWS)
• High mortality: Doubling of historical mortality rate without introduction of a new known pathogen.
• Respiratory signs, including pneumonia
• Porcine dermatitis and nephropathy syndrome (kidneys are affected)
• Enteric signs including diarrhea and weight loss
• Reproductive disorders, including abortions, stillbirths and fetal mummification

PCVAD must be properly diagnosed by a veterinary diagnostic laboratory that will confirm the following histopathological (microscopic) changes in affected pigs:

• Depletion of lymphoid cells in lymphoid tissues of growing pigs
• Identification of disseminated granulomatous inflammation in one or more tissues (e.g., spleen, lymph nodes, lung, kidney, tonsil, etc.)
• Detecting PCV2 virus in lesions of growing pigs
• Reproductive disorders associated with PCVAD confirmed by demonstrating presence of PCV2 antigen in fetal myocarditis lesions