Using field-based epidemiological methods to investigate FMD outbreaks: an example from the 2002 outbreak in Korea.

Relevant to foot and mouth disease (FMD), most published epidemiological studies have been conducted using quantitative methods and substantial regional or national datasets. Veterinary epidemiology also plays a critical role during outbreak investigations, both to assist with herd-level decision-making and to contribute relevant information to assist with ongoing national or regional control strategies. Despite the importance of this role, however, little information has been published on the use of applied (field-based) epidemiological methods during disease outbreaks. In this study, we outline an investigative template for FMD, and a case study of its use during the 2002 FMD outbreak in Korea. Suitable for use during field-based epidemiological investigations of individual farms within a broader regional/national response, the template considers three steps including confirming infection, estimating date of introduction and determining method of introduction. A case study was conducted on IP13 (the 13th infected premises), the only IP during the 2002 FMD outbreak in Korea that was geographically isolated from all other known cases. The authorities first became aware of FMD on IP13 on 2 June, however, infection may have been present from 12 May. Infection was confirmed on 3 June 2002. FMD was probably spread to IP13 by a contract worker who had participated during 2-4 May in the culling operations on IP1. Other routes of spread were ruled out during the investigation. The contract worker lived in the locality of IP13 and worked on a part-time basis at a pork-processing plant that was adjacent to this farm. The contractor became heavily contaminated during the cull, but did not comply fully with cleaning and disinfection requirements once the cull had been completed. The investigative template contributed structure and focus to the field-based investigation. Results from this case study demonstrate the need for strict management of personnel in disease control and adherence to the sanitary rules by all those involved.