Animal Health at the farm level: PMWS and PRRS

Table of Contents

1. Introduction
   1. Objectives
   2. Learning goals
   3. Teacher page
2. Unit 1: Importance of PRRS and PMWS to the European pig industries
3. Unit 2: PRRS - causes and predisposing factors
   1. Transmission
   2. Predisposing factors
4. Unit 3: PMWS - causes and predisposing factors
   1. Transmission
   2. Predisposing factors
5. Unit 4: Alternative strategies for managing PRRS and PMWS
   1. Biosecurity and farm management
   2. Vaccination
   3. Depopulation and repopulation (De-pop / re-pop)
   4. Other strategies proposed for PRRS control
6. Unit 5: Outlook for the future
7. Unit 6: Conclusions
8. Completion
   1. Comments
   2. Self-assessment
   3. Evaluation
   4. Bibliography and Useful websites
9. Acknowledgments

Transmission

Animal movement is thought to be one of the main ways the virus is spread from farm to farm and within farms. PCV-2 can be excreted in faeces, urine, semen and nasal mucus. Diseased pigs tend to excrete more virus than healthy animals. The virus can be transmitted from an infected pig to a non-infected pig by direct contact: oral-nasal and oral-faecal routes and through semen of infected boars even where artificial insemination is used. Transmission from infected sows to the foetus is possible.

What happens to the virus outside the pig? PCV-2 is very resistant to high temperatures and a wide range of pH conditions and it is quite resistant to some disinfectants, products containing alcohol, iodine and formaldehyde or chlorhexidine compounds. On the other hand, products containing phenol, quaternary compounds, oxidising or an alkali as active ingredients can reduce virus infectivity by 30 to 73%. These results however, are taken from trials in the lab and might differ from situations in the farm. Nonetheless we should keep them in mind, and we will come back to them in the section on 'strategies for managing PMWS and PRRS'