PCVAD – Porcine Circovirus Associated Diseases

Other issues related to PCV2

Causal agent	Porcine Circovirus II – and conditions where the virus may be found in high numbers. Extremely small DNA virus (genome in a circle) none enveloped. Name extremely confusing as PCVII is present in almost all pigs and therefore if isolated can be “associated” with any condition.
Age group	Foetus - death abortion and myocarditis Weaner – PCVAD, PMWS Grower – PCVAD, PMWS, PDNS, Granulomatous enteritis, Necrotic pneumonitis Adults – abortion and no symptoms
Clinical signs
Foetus	Abortion, infertility, mummification and stillborn piglets
Weaner	If the pigs are severely stressed with primary pathogens or management problems. Parvovirus and PRRSv can play significant roles in the induction of a PCVII problem. However, the problem will generally present as a single batch or a series of batches but only while the management/diseases problems persist.
	PMWS - 15-60 kg pigs present with acute wasting – generally within 4 days becoming extremely emaciated. Surrounding pigs are normal and then waste rapidly. Mortality generally extremely high – 20% or more. Death is associated with other infections already on the farm.
Grower	May present with part of the weaner PMWS issues on the farm. Growers may present with PDNS, however, role of PCVII in PDNS is not determined. Another virus Torque Teno virus may be associated. Granulomatous enteritis may be associated with PCVII and results in ileitis and wasting disorders. However, not all cases of Granulomatous enteritis are associated with PCVII. Necrotic pnuemonitis has been also associated with PCVII, however in about 15% cases PCV2 is not found.
Adult	Abortion is described. However, reproductive effects are minimal/non-existent. Could play a role in SMEDI syndromes on farms.
Normal pig	Most pigs and almost all pig farms are infected with PCVII completely asymptomatically.
Foetus myocarditis		PCVAD – PCVII+feeding issues	PMWS in a 20 kg weaner
PDNS		Abortion	Normal pigs with PCVII

Infectivity
	PCVII is extremely resistant virus.
Transmission
	PCVII can be found in semen
	PCVII occurs normally on all farms
Post-mortem Lesions – not PMWS or PDNS see separate pages
Normal pig	None
Weaner - PCVII	Pigs with enhanced wasting in excess of normal expectations
	Single or generally enlargement of lymph nodes.
	Liver may be pale. With associated starvation the pig may have a gastric ulcer. Lungs may present with an histiocytic interstitial pneumonia. There may be enlarged kidneys with white spots visible on the surface.
	Histological lesions include: lymphoid depletion, granulomatous inflammation with syncytial formation. Histiocytic infiltration. Presence of botryoid basophilic intra-cytoplasmic inclusion bodies which stain for PCVII by immunohistochemistry. Note these lesions are identical to those associated with PMWS. There will be no increase in PDNS cases.
Prominent lymph nodes		Pale liver	Enlarged, kidneys with white spots
Histiocytic Interstitial pneumonia		Gastrohepatic lymph node enlarged	Other lesions depending on primary cause – Salmonella colitis
Severe pneumonia – Pasteurella as a primary problem		Lymphoid depletion in the lymph node	Immunohistochemistry for PCVII
PCVAD histological scores

Grower	Granulomatous enteritis. This might be confused with PIA/ileitis and may be considered to be a differential diagnosis.
	Granulomatous enteritis	Granulomatous enteritis with associated PCVII IHC
Foetus	Foetal myocarditis with associated PCVII PCVII may act as a SMEDI virus in the pregnant sow resulting in death of the piglets – the stage of pregnancy results in a variety of clinical signs – infertility, embryonic death, mummification and stillborn piglets. Spread between foetuses is extremely limited
		Myocarditis of foetal heart with ICH for PCVII
Diagnosis
	Immunohistochemistry and characteristic histology changes Reading IHC slides
	Note need at least 5 lymph nodes to be considered a generalised problem General investigation
	Antibodies and virus isolation generally unrewarding as virus ubiquitous. There is no correlation with presence of antibody or virus in pigs. This is a waste of clients money to investigate using these techniques. Antibody concentration of marginal benefit. PCR unrewarding on blood as all pigs positive
	Move piglets to a separate ideal environment – with PMWS the weaners will still die, with PCVAD mortality problems will cease.
	With management changes post-weaning mortality will fall below 1.66xsd of normal herd mortality over period of 2 months
Treatment
Normal pig	Ensure feedback programmes are adequate to ensure stable herd immunity
	Ensure good pig flow management to achieve all-in/all-out
PCVAD (not PMWS)	Resolve management and pathogen overload problem
	Post-weaning feeding regimes
	Pig flow and internal biosecurity
	Resolve PRRSv and SIV problems and associated biosecurity issues
	Vaccination may be considered, but extremely expensive and management issues will need to be addressed eventually anyway Vaccinate pigs before 5 weeks of age. Vaccination of PCV2
PMWS	Vaccinate using PCVII pre-farrow to the sow or piglets in farrowing house or at weaning
	See PMWS advice sheets
Common differentials
	PMWS, Ileitis other causes of pneumonia and wasting. Other causes of abortion. Note a transient lymph node enlargement is normal in healthy young pigs –PCV2?
Other issues	There are now a variety of other viruses which are being associated with PCVAD conditions – Torque Teno virus and Toro viruses for example. Their true association (if any) will become apparent with time.
Zoonotic implications
	None specifically. May increase prevalence of meningitis and salmonella which are zoonotic.