Livestock density as risk factor for livestock-associated methicillin-resistant Staphylococcus aureus, the Netherlands

Abstract

To determine whether persons living in areas of high animal density are at increased risk for carrying livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA), we used an existing dataset of persons in the Netherlands with LA-MRSA carriage and controls who carried other types of MRSA. Results of running univariate and multivariate logistic regression models indicated that living in livestock-dense areas increases the odds of nasal carriage of LA-MRSA. We found that doubling pig, cattle, and veal calf densities per municipality increased the odds of LA-MRSA carriage over carriage of other types of MRSA by 24.7% (95% CI 0.9%-54.2%), 76.9% (95% CI 11.3%-81.3%), and 24.1% (95% CI 5.5%-45.9%), respectively, after adjusting for direct animal contact, living in a rural area, and the probable source of MRSA carriage. Controlling the spread of LA-MRSA thus requires giving attention to community members in animal-dense regions who are unaffiliated with livestock farming.

Figure 1

A) Case-patients with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and controls with typeable MRSA, according to population density, the Netherlands, 2003–2005. B) Density of cattle per municipality. C) Density of pigs per municipality. D) Density of veal calves by municipality.

Figure 2

A) Spatial intensity of case-patients with livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA); B) spatial Intensity of controls with typeable MRSA (T-MRSA); and C) calculated spatial odds for LA-MRSA compared with those for T-MRSA, the Netherlands, 2003–2005.

Figure 3

Clusters of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) in the Netherlands, 2003–2005, taking into account 20% population at risk with overlays showing veal calf density (A), cow density (B), and pig density (C). RR, relative risk.