Risk factors for porcine reproductive and respiratory syndrome outbreaks in Vietnamese small stock farms

Abstract

AIM: To examine risk factors that could have played a role in the 2010 porcine reproductive and respiratory syndrome (PRRS) outbreak in Yenhung district, Quangninh province, North-Vietnam, with the purpose of establishing why existing control measures implemented after previous outbreaks had failed to prevent further outbreaks.

METHODS: A case-control study was carried out in Yenhung district. Data were obtained by an interview-based questionnaire survey. The sampling unit was households, which equated to small-scale pig farms. A total of 150 case and 150 control households were selected at communes affected by the 2010 PRRS epidemic during April to June. Risk factors were analysed using binary logistic regression and unconditional multiple logistic regression.

RESULTS: Households infected with PRRS were significantly associated with multiple variables belonging to three main groups: (1) location of the farms: i.e. farms positioned <1,000 m from a pig abattoir or within 500 m of local markets or 100 m of main roads; (2) farm management: i.e. where there was non-application of weekly farm disinfection, feeding uncooked swill, new introduction of purchased pigs without isolation, or usage of water from irrigation systems for raising pigs; (3) people and animal contact: i.e. where households kept animals with either no confinement or partial confinement, had visits by family members to other affected farms or had frequent visits by neighbours. The use of water from irrigation systems was found to be the risk factor most strongly associated with infected households in the 2010 outbreak (OR=22; 95% CI=12–42).

CONCLUSIONS: The results show that the epidemiology of PRRS in Quangninh province was linked to sociological and cultural practices, and that effective PRRS control needs an integrated approach coupled with behavioural changes in the pig raising practices of the general public. Failure to recognise this could explain why further outbreaks have occurred.

KEY WORDS:

• South East Asia
• Vietnam
• Quangninh province
• porcine reproductive and respiratory syndrome
• PRRS
• risk factors
• epidemiology
• husbandry practices
• pigs
• case-control study

Acknowledgements

The authors would like to thank the Department of Animal Health of Vietnam and the Quangninh sub-Department of Animal Health for facilitating the study. We are grateful to the experts for their estimations of proportion of household controls exposed to each risk factor, and to all farmers and veterinary officers who took part in this study.

The project was funded by James Cook University and in-kind contribution was provided by the Quangninh sub-Department of Animal Health.

The study was supported by the Department of Animal Health, Ministry of Agriculture and Rural Development, Vietnam.

Notes

*Non-peer-reviewed