Spatial transmission of Swine Vesicular Disease virus in the 2006-2007 epidemic in Lombardy

• Published in: PloS one Vol. 8; no. 5; p. e62878
• Main Authors: Nassuato, Claudia, Boender, Gert Jan, Eblé, Phaedra L, Alborali, Loris, Bellini, Silvia, Hagenaars, Thomas J
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 07.05.2013; Public Library of Science (PLoS)
• Subjects: Agriculture; Analysis; Animals; Biology; Culling; CVI Diagnostics and Crisis; CVI Diagnostiek en Crisisorganisatie; CVI Virologie; CVI Virology; Data processing; Diagnostics & Crisis Organization; Diagnostiek & Crisisorganisatie; Disease transmission; Enterovirus B, Human - physiology; Epidemics; Epidemics - statistics & numerical data; Farms; Hogs; Infections; Influenza; Italy - epidemiology; Livestock; Mathematical models; Medicine; Municipalities; Outbreaks; Pork industry; Poultry; Provinces; Spatial Analysis; Swine; Swine vesicular disease; Swine Vesicular Disease - epidemiology; Swine Vesicular Disease - transmission; Veterinary Science; Virologie; Virology; Viruses; Italy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0062878

In 2006 and 2007 pig farming in the region of Lombardy, in the north of Italy, was struck by an epidemic of Swine Vesicular Disease virus (SVDV). In fact this epidemic could be viewed as consisting of two sub-epidemics, as the reported outbreaks occurred in two separate time periods. These periods differed in terms of the provinces or municipalities that were affected and also in terms of the timing of implementation of movement restrictions. Here we use a simple mathematical model to analyse the epidemic data, quantifying between-farm transmission probability as a function of between-farm distance. The results show that the distance dependence of between-farm transmission differs between the two periods. In the first period transmission over relatively long distances occurred with higher probability than in the second period, reflecting the effect of movement restrictions in the second period. In the second period however, more intensive transmission occurred over relatively short distances. Our model analysis explains this in terms of the relatively high density of pig farms in the area most affected in this period, which exceeds a critical farm density for between-farm transmission. This latter result supports the rationale for the additional control measure taken in 2007 of pre-emptively culling farms in that area.