Porcine Circoviruses

Also known as: Post-weaning Multisystemic Wasting Syndrome — PMWS — Porcine Dermatitis and Nephropathy Syndrome — PDNS — PCV

Introduction

There are two serotypes of porcine circovirus, which are as follows; PCV1 which is harmless and PCV2 which is virulent. The virulent serotype, PCV2, causes Post-weaning Multisystemic Wasting Syndrome (PMWS) in young pigs and Porcine Dermatitis and Nephropathy Syndrome (PDNS) in older pigs.
PCV2 is the most important widespread porcine virus as it causes detrimental losses to the industry and predisposes to secondary infection, which obviously can result in further losses. It is easily misdiagnosed. Route of transmission is via the faeco-oral route or venereal route. The host often mounts a poor immune response to the virus.

PMWS

This disease causes enlarged lymph nodes and lymphopenia, as the virus concentrates in germinal centers.

Signalment

Typically strikes weaners of around 8-12 weeks old.

Clinical Signs

Clinical signs include pale skin colour and/or jaundiced skin, enlarged lymph nodes and kidneys, and unthrifty appearance and lameness. There may also be signs of respiratory disease, such as mild interstitial pneumonia, failure of lungs to collapse on opening the thoracic cavity and also diarrhoea. Some may present as sudden death and mortality rates can reach 40% in an outbreak.

Differential Diagnoses

There are a large range of differentials, particularly Classical Swine Fever, African Swine Fever, Pasteurella, and colisepticemia.

PDNS

This condition can follow PMWS or can be seen as a stand alone condition and presents as an immune-mediated necrotising vasculitis.

Signalment

It is typically seen in growers and finishers.

Clinical Signs

Signs can include extensive hemorrhages of kidneys and skin, especially in the scrotal region, accompanied by pyrexia.

Diagnosis

Diagnosis of these conditions is based on clinical signs and history and signalment. Definitive diagnosis can be achieved by performing a PCR for the PCv nucleic acid, however some positive animals can show no clinical signs. Differentials such as Classical Swine Fever must be ruled out.

Treatment and Control

There are currently no vaccines available for this condition. Antibiotics can be used to treat/prevent any secondary bacterial infections.

Control measures include good ventilation, bio-security and proper management. Passive antibody can sometimes be used in severe circumstances.

Porcine Circoviruses Learning Resources
Full Text Articles Full text articles available from CAB Abstract (CABI log in required)	Porcine circovirus structure and replication: a minireview. Weingartl, H. M.; University of Maribor, Faculty of Agriculture, Maribor, Slovenia, Agricultura (Slovenia), 2002, 1, 1, pp 11-14, 28 ref.