Spatio-temporal evaluation of cattle trade in Sweden: description of a grid network visualization technique

Abstract

Abstract. Understanding the intensity and spatial patterns of animal transfers is of prime importance as geographical moves play an important part in the spread and potential control of contagious animal diseases of veterinary importance. For the purpose of visualizing all registered between-herd animal movements in Sweden between 1 July 2005 and 31 December 2008 by map animation, a grid network technique based on the Bresenham line algorithm was developed. Potential spatio-temporal clustering of animals registered as sold or purchased based on location and month of trade was also detected and tested using a spatial scan statistic. Calculations were based on data from 31,375 holdings and 3,487,426 head of cattle. In total, 988,167 between-herd movements of individual bovines were displayed in a sequence of maps covering three and a half years by 2-week intervals. The maps showed that several cattle movements, both short-and long-distance, take place in Sweden each week of the year. However, most animals (75%) were only registered at one single holding during the study period and 23% were sold to a different holding once. Spatial scan statistics based on data from the year 2008 indicated uneven distributions of purchased or sold animals in space and time. During each autumn, there was an increase in cattle movements and October and November showed significantly more cases of sold or purchased animals (relative risk ~1.7, p = 0.001). Based on the results, we conclude that cattle trade is constantly active at a considerable level. This, in combination with possibly insufficient biosecurity routines applied on many farms, constitutes a risk that contagious diseases are spread in the population. The grid network maps were generated through the use of open-source tools and software in order to decrease software costs and facilitate sharing of programme code. In addition, the technique was based on scripts that allow for the inclusion of iterative processes and that comprise all main parts of map creation. Thereby, a large number of maps can be generated and the demands for high reproducibility are met.

Evaluation of Strategies to Control a Potential Outbreak of Foot-and-Mouth Disease in Sweden

“…This confirmed that epidemic size was mainly driven by infected cattle farms. It also confirmed the expected effect of long distance movements in keeping North and South of Sweden highly inter-connected (29). …”

Cryptosporidium parvum IId family: clonal population and dispersal from Western Asia to other geographical regions

“…This may be partially attributed to the introduction of new animals into the herd or area via animal trade. Indeed, data showed that cattle trade was maintained at a considerable level in Sweden31. Therefore, frequent animal trade in Sweden would increase the heterogeneity of C. parvum IId subtypes on farms and the complexity of infections.…”

Geographical distribution of salmonella infected pig, cattle and sheep herds in Sweden 1993-2010

“…Dublin or S . Typhimurium may be a reflection of the clustering of cattle movements in Sweden [15], where the largest number of movements occur within the same geographical region. These two types of salmonella are the most commonly detected in Swedish cattle [6] and the main route of spread between herds would be expected to be via livestock trade.…”