Porcine dermatitis and nephropathy syndrome in New Zealand

Abstract

CASE HISTORY: An outbreak of fatal or debilitating disease characterised by wasting and cutaneous lesions that usually necessitated euthanasia, occurred over a period of 4 months in pigs 14–16 weeks of age from a commercial ‘farrow-to-finish’ unit in the North Island of New Zealand. During the outbreak, 67 deaths were attributed to the condition, accounting for 2–3% of total production. The outbreak preceded the diagnosis of post-weaning multisystemic wasting syndrome (PMWS) on this farm.

CLINICAL FINDINGS: Sick pigs were thin, depressed, and pyrexic, and most had multiple extensive erythematous crusting cutaneous lesions that were most prominent in the region of the hindquarters, forequarters and head. Those with cutaneous lesions affecting the hindlimbs had subcutaneous oedema and enlarged superficial inguinal lymph nodes. Diarrhoea was commonly present.

PATHOLOGICAL FINDINGS AND DIAGNOSIS: In addition to the skin lesions, the main gross pathological changes were renal petechiation and lymphadenomegaly.

The cutaneous and renal lesions resulted from necrotising and neutrophilic vasculitis, and thrombosis and infarction of adjacent tissues. Vascular lesions were variably present in the spleen, liver, lymph nodes and intestines. Renal tubules were distended by sero-haemorrhagic fluid and proteinaceous casts. Lymphoid tissue changes typical of porcine circovirus type 2 (PCV2)-associated disease included depletion of mature lymphocytes, histiocytic infiltrations and circoviral inclusion bodies. Lesions associated with PCV2 in non-lymphoid tissues included granulomatous or non-suppurative interstitial pneumonia, interstitial nephritis, gastroenteritis, and hepatitis with hepatocellular apoptosis.

DIAGNOSIS: Porcine circovirus-associated disease (PCVAD) represented by concurrent porcine dermatitis and nephropathy syndrome (PDNS) and emergent PMWS.

CLINICAL RELEVANCE: This is the first published description of PDNS and of combined PDNS and PMWS in pigs in New Zealand. In addition, the prevalence of PDNS, which is usually a sporadic disorder, was inconsistent with a diagnosis of PDNS alone.

KEY WORDS:

• Porcine circovirus-associated disease
• porcine dermatitis and nephropathy syndrome
• porcine circovirus type 2
• post-weaning multisystemic wasting syndrome
• necropsy
• histopathology
• immunohistochemistry
• in-situ hybridisation

Acknowledgements

The authors wish to acknowledge the perseverance of the farmer in the face of a protracted and complex disease investigation. Thanks are also extended to Pat Davy, Evelyn Lupton, Mary Gaddum and Diane Knight for provision of histological and ISH technologies.