This document summarizes information about Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), including its history, etiology, prevalence, risk factors, transmission, immune response, pathogenesis, clinical signs, diagnosis, treatment, control and prevention. PRRSV causes reproductive losses and respiratory disease in pigs. It is endemic in many pig herds worldwide. Control and prevention strategies include vaccination, biosecurity measures, and managing exposure to reduce stress.

1. Porcine Reproductive and Respiratory Syndrome Virus(PRRSV) Katie Krimetz September 4, 2008 Western University of Health Sciences DVM 2010

2. History “Mystery Swine Disease” “Blue-eared Pig” Reproductive losses for adults, post-weaning pneumonia, suppression of growth for all ages Lelystad virus coined at first http://irrawaddy.org/articlefiles/8148-Pig.gif

3. Etiology Arteriveridae +sRNA, enveloped Spherical, 45-80nm Genus Arterivirus Also: equine arteritis virus Antigenic differences N. American v European 55% homologous U.S. v Canadian 90% homologous http://dantri.com.vn/Sukien/2007/4/173412.vip

4. Prevalence Endemic herds (30-70% seropositive) 60% of all herds have SOME seropositive pigs Morbidity/Mortality 50/25% - Death usually due to bacterial infection http://www.respig.com/images/prrs-weak-stillb.jpg

5. Risk Factors Dose/strain of virus exposed to Host Susceptibility Nursing/lacking maternal immunity Young growing/finishing and sows lacking acquired immunity Biosecurity Large turnover Replacements Lack of quarantine Naïve herd Sanitation http://www.mountairyalpacas.com/pblog/images/piglets.JPG

6. Transmission/Sources Confinement Direct contact (nasal d/c, urine, feces, saliva, tonsils) Persistent Infection Incomplete infection Variable periods of active immunity Boars Shed for 40 days in semen Replacement gilts Fomites Workers not a risk unless they are contaminated w/ viremic blood Airborne Rare, but possible Low temp, low sun, high humidity Densely populated Insects?

7. Immune Response Cell-mediated immune response Virus isolated from alveolar macrophages 40% destroyed within 7 days Antibodies are detectable by 14-21 days Seropositive sows pass colostral antibodies Which decline by 3-8 weeks Virus can persist in piglets for 6-9 weeks Viremia and Antibodies can exist together Prevents reinfection and reduces /eliminates shedding

8. Pathogenesis/Necropsy Viremia Distributed to body Clinical Signs Duration: 14 days Avid time for transplacental transmission 3rd and maybe 2nd trimester http://www.vetmed.iastate.edu/departments/vdpam/swine/diseases/pcv2/associated_diseases/webimages%202/lung-2.jpg Fetus 40-49d gestation Pulmonary lesions 90+d gestation Umbilical hemorrhage, necrotizing umbilical arteritis, parietal hemorrhage Piglets Lungs heavy and consolidated Severe, necrotizing, interstitial pneumonia http://www.hdcn.com/symp/lund/jtimg23.jpg

9. Clinical Signs, 2 stages Reproductive Loss Respiratory Disease Breeding/Gestation Rolling anorexia Lethargy Depression Pyrexia Chronic Form (1-2 years) increased stillbirths and pre-weaning mortality Farrowing Premature (105-107d) Increased stillbirths & mummies Agalactic no colostrum Piglets begin “thumping” Post-weaning Reduced ADG (-50-75%) Pneumonia Death (10-25%) Respond poorly to medication PRRSV infection without complication from opportunistic pathogens has little impact on herd health and performance

10. Diagnosis http://www.ga-international.com/PCR%20LABEL.100_0879CROP.jpg PCR (serum, semen, tissue) Measures IgGs to the virus Sensitive, available in short period (24-48hrs) ELISA Cannot differentiate antibodies from natural infection or vaccine Attempt to determine point of infection within life of pig 5-7 day old piglets are great samples for detection Catch before weaning if virus is shed during sow’s lactation

11. Treatment Breeding/Gestation Antibiotics for fever and reduce secondary bacterial infection Lactation Antibiotics and anti-inflammatory Diet reformulation? Suckling piglets Adequate environment Mortality >75%  destroy Electrolytes with vitamins Post-Weaning Antibiotics http://www.pfizerah.com.mx/PAHimages/gs_mx_sp_images/OverviewImages/excede_3.jpg http://www.valleyvet.com/swatches/821RX_L_vvs_000.jpg

12. Control and Prevention Overbreed Compensate for production loss Artificial Insemination Ensure adequate sperm cells Postpone castration/weaning Decrease stress during loss of maternal antibodies Dip needles between injections Avoid hematogenous spread of PRRS http://www.ars.usda.gov/is/graphics/photos/nov06/d630-1i.jpg

13. Control and Prevention Disinfect Chloroform, ether, formaldehyde, phenol-based compounds Nursery Depopulation Interrupts horizontal transmission Controls opportunistic pathogens more than PRRS Vaccinate (MLV) Pre-gestation sows/gilts Boars Best for prevention against homologous reinfection http://www.bi-vetmedica.com/product_sites/IngelvacPRRSATP/documents/IngelvacPRRSATP_l.jpg

14. http://www.cals.ncsu.edu/waste_mgt/smithfield_projects/ambient%20digester/aerialforweb.jpg Biosecurity AIAO Facility Reduces horizontal transmission Sanitation Disinfectants work well due to envelope PRRSV sensitive to pH changes <5 and >7 Quarantine 60-90 days minimum Acclimate new arrivals Housed in developer facility to allow natural exposure http://bvaler.blogspot.com/2007_08_01_archive.html

15. References APHIS. Vaccination Against Mycoplasma Pneumonia, Swine Influenza, and PRRS in Breeding Females, 2000 and 2006. In: Veterinary Services CfEaAH, ed2008. Benfield D, Calvert J, Chowdhury S, al e. Colloquium on Prospects for Development of an Effective PRRS Virus Vaccine2007; University of Illinois College of Veterinary Medicine. Cho JG, Dee SA. Porcine Reproductive and Respiratory Syndrome Virus. Theriogenoloogy. 2006;66:655-662. The Merck Veterinary Manual: Merck & Co., Inc.; 2008. RadostitsOM. Herd Health, Food Animal Production Medicine. 3rd Edition ed: W.B. Saunders Company; 2001.

16. Questions?