Proximal determinants of risk for tularemia outbreaks
Principal Investigator: Sam Telford
Abstract: DESCRIPTION (provided by the applicant): Although much is known about the biology of Francisella tularensis, the factors that regulate its natural prevalence remain un-described. We seek to test the 'rule of the incumbent' hypothesis: by analogy with politics, F. tularensis epizootics in the northeastern United States are limited by interactions with a 'ruling' endosymbiotic Francisella sp. (previously classified as Wolbachia sp.) common within tissues of dog ticks, Dermacentor variabilis. The recent outbreak of tularemia on Martha's Vineyard provides a unique opportunity for identifying factors that serve as the basis for increased transmission of this rare infection because sites there appear to be longstanding natural foci of this infection. However, testing this hypothesis requires identification of these natural foci, which may comprise small patches of vegetation; transmission is not homogeneously distributed over the entire 100,000-hectare island. Accordingly, we first seek to identify such natural foci by (1) determining whether striped skunks (Mephitis mephitis) serve as effective sentinels for F. tularensis transmission; and (2) complementing skunk-based predictions by enlisting landscapers and others who are occupationally exposed to tularemia and other tick borne infections to actively report, in real time, the presence of animal carcasses encountered during their work. Natural foci will be definitively confirmed by intensive longitudinal epizootiologic analyses (prevalence of F. tularensis infection in ticks and other potential vector arthropods; evidence of exposure in rodents and other animals). In this manner, we shall accumulate reliable study sites and the preliminary data required for a comprehensive test of the 'rule of the incumbent' hypothesis. In addition, our mapping of risky sites may serve as the basis for local public health measures. We anticipate that the epidemiologic and epizootiologic methods developed or validated during the proposed work may contribute towards enhanced investigations of tularemia outbreaks; new prevention strategies for those at risk of natural or illicit tularemia exposure; enhanced detection of F. tularensis in the environment; and, ultimately, a better understanding of F. tularensis-host interactions.
Funding Period: 2003-09-30 - 2006-08-31
more information: NIH RePORT
- Diversity of Francisella species in environmental samples from Martha's Vineyard, MassachusettsZenda L Berrada
Tufts Cummings School of Veterinary Medicine, North Grafton, MA, USA
Microb Ecol 59:277-83. 2010..tularensis and Francisella novicida were detected from samples collected from the brackish-water pond. We conclude that diverse Francisella spp. are present in the environment where human cases of pneumonic tularemia occur...
- Survival of Francisella tularensis Type A in brackish-waterZenda Lea Berrada
Department of Biomedical Sciences, Tufts Cummings School of Veterinary Medicine, 200 Westboro Road, Building 20, North Grafton, MA 01536, USA
Arch Microbiol 193:223-6. 2011....
- Raccoons and skunks as sentinels for enzootic tularemiaZenda L Berrada
Tufts University Cummings School of Veterinary Medicine, North Grafton, Massachusetts 01536, USA
Emerg Infect Dis 12:1019-21. 2006..Skunks and raccoons were frequently seroreactive, whereas white-footed mice, cottontail rabbits, deer, rats, and dogs were not. Tularemia surveillance may be facilitated by focusing on skunks and raccoons...
- Pneumonic tularemia on Martha's Vineyard: clinical, epidemiologic, and ecological characteristicsBela T Matyas
Massachusetts Department of Public Health, 305 South Street, Room 506, Boston, MA 02130, USA
Ann N Y Acad Sci 1105:351-77. 2007..Why tularemia is prevalent on Martha's Vineyard and why it commonly presents as a pneumonic disease there remain undescribed...
- Molecular detection of Bartonella schoenbuchensis from ectoparasites of deer in MassachusettsKotaro Matsumoto
Division of Infectious Diseases, Tufts University School of Veterinary Medicine, North Grafton, Massachusetts 01536, USA
Vector Borne Zoonotic Dis 8:549-54. 2008..Five of 6 keds were found to contain B. schoenbuchensis DNA, and 2 deer ticks cofeeding on deer with such keds did as well. The detection of Bartonella DNA in deer ticks probably represents contamination by infected deer blood...