Survival of Francisella tularensis Type A in brackish-water
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S H O R T CO M MU N I C A T I O N
Survival of Francisella tularensis Type A in brackish-water Zenda Lea Berrada · Sam R. Telford III
Received: 30 September 2010 / Revised: 10 November 2010 / Accepted: 10 November 2010 / Published online: 7 December 2010 © Springer-Verlag 2010
Abstract Martha’s Vineyard (MV), Massachusetts has been the location of two outbreaks of pneumonic tularemia; landscaping activities have been associated with risk, suggesting environmental inhalation exposure. We determined whether salinity or other components of brackish-water present in a location with endemic tularemia may prolong survival of F. tularensis. In addition, we demonstrate for the Wrst time that F. tularensis Type A appears similar to Type B with respect to environmental stability. The results of this study suggest an explanation for why MV is the site of pneumonic tularemia transmission as opposed to sites in the southcentral USA, where tularemia is more commonly reported: Bacteria may be more prone to surviving in saltinXuenced soil or moisture in the island setting. Keywords Tularemia · Environmental stability · Microcosm · Type A · Martha’s Vineyard The occurrence of pneumonic tularemia on the island of Martha’s Vineyard, Massachusetts is highly suggestive of an unusual relationship between the ecology of the island and the human activity on this island. From 2000 to 2006, 59 cases of tularemia due to Francisella tularensis subsp. tularensis (Type A) were reported, of which nearly 2/3 were pneumonic in clinical presentation (Matyas et al. 2007). A case–control study conducted by the Center for Disease Control and Prevention and the Massachusetts Communicated by Erko Stackebrandt. Z. L. Berrada · S. R. Telford III (&) Department of Biomedical Sciences, Tufts Cummings School of Veterinary Medicine, 200 Westboro Road, Building 20, North Grafton, MA 01536, USA e-mail: [email protected]
Department of Public Health established that landscaping activities on the island increase the risk for tularemia (OR, 6.7; P = 0.04), suggestive of an aerosolization of F. tularensis-contaminated environmental material while undertaking these activities (Feldman et al. 2001, 2003). Field investigations, however, have failed to identify the fomites that serve as an aerosol risk Feldman et al. (2001). Although F. tularensis subsp. holarctica (Type B) is well known to contaminate and survive in freshwater and has been identiWed in environmental matrices contaminated by infected animal sources (Dahlstrand et al. 1971; Jellison et al. 1942; Parker et al. 1951; Pollitzer et al. 1967; Stewart 1996; Syrjala et al. 1985), F. tularensis Type A has yet to be isolated from such sources. Indeed, we are unaware of peer-reviewed evidence that Type A may persist for prolonged periods in the environment; reviews of the biology of tularemia conXate what is known for Type B with evidence for Type A to have such capacity. There are approximately 249 hectares of freshwater or mostly freshwater ponds on Martha’s Vineyard, and 27 coastal/salt ponds that cover ne
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