Porcine reproductive + respiratory syndrome virus

Question 1

What is Porcine Reproductive and Respiratory Syndrome Virus? (PRRSV)

Answer 1

*Most important agent causing reproductive failure in sows + severe pneumonia in piglets
*2 isolates = European type 1 + American type 2

Question 2

What type of virus is PRRS? what is it related to?

Answer 2

*Arteriviruses
-other members = Equine arteritis virus , Simian haemorrhagic fever virus, Lactate Dehydrogenase-elevating virus

Question 3

Where do arteriviruses replicate?

Answer 3

*Replicate in the perinuclear cytoplasm of their host cells
*Primary target cell of PRRSV = alveolar macrophage = immune system

Question 4

What is the pathogenesis of PRRSV?

Answer 4

1. Transmission by inhalation, ingestion, coitus, skin damage + contaminated needles
2. Replicate in mucosal, pulmonary or regional macrophages
3. Regional lymph nodes + viraemia
4. Systematic distribution to mononuclear cells and tissue macrophages
5. Clinical disease (Age dependent)

Question 5

What is seen with PRRSV in Sow, Neonatal pig, nursery / grower pig, finishing pig and boar?

Answer 5

*Sow – abortion of premature farrowing, stillborn pigs, weak live born pigs.
*Neonatal pig - dyspnea, CNS signs, high mortality
*Nursery or grower pig – increased mortality, secondary infections, failure to thrive.
*Finishing pig – fever and less feed consumption.
*Boar – Fever, semen changes.

Question 6

In addition to reproductive failure what else may be seen in sows / gilts?

Answer 6

*anorexia
*fever
*lethargy
*pneumonia
*agalactica
*red/blue discolouration of the ears and vulva
*subcutaneous and hind limb oedema
*delayed return to oestrus after weaning
*in rare cases, death

Question 7

What are seen with subclinical infections in growers + finishing pigs?

Answer 7

*destruction of macrophages
*thickening of the alveolar septa
*occasional lesions in blood and lymphatic vessels
*minor heart lesions

Question 8

What is seen with clinical infections of PRRSV in growers + finishing pigs?

Answer 8

*fever
*sneezing
*hyperpnea
*dyspnoea
*coughing
*pneumonia
*lethargy
*periocular oedema
*occulonasal discharge.

Question 9

How does PRRSV interact with other pathogens?

Answer 9

*Mycoplasma enhances pathological effects of PRRSV
*PRRSV enhances the pathological effect of Porcine influenza virus
*PRRSV predisposes pigs to infection and disease caused by streptococcus suis
*PRRSV can cause loss of bactericidal function of pulmonary intravascular macrophages

Question 10

How is PRRSV diagnosed?

Answer 10

*Serology
*Virus isolation
*ELISA

Question 11

What are PRRSV vaccines targeting?

Answer 11

Target surface glycoproteins