Natural reservoirs and vectors of Francisella tularensis in Sweden

Broman, Tina (1,2), Forsman, Mats (2); Eliasson, Henrik (3); Bäckman, Stina (2); Grunow, Roland (4); Larsson, Eva (2); Bäck, Erik (3); Eriksson, Ulla (3); Johansson, Anders (1,2); Sjöstedt, Anders (1)

(1) Dept Clinical Microbiology, University Umeå, Sweden;
(2) Swedish Defence Research Agency, Umeå, Sweden;
(3) Örebro University Hospital, Örebro, Sweden;
(4) Bundeswehr Institute of Microbiology, Munich, Germany

Francisella tularensis is a highly virulent bacterium capable of infecting many mammals, and the etiological agent of the zoonotic, arthropod-borne disease tularemia. F. tularensis is one of the most infectious bacteria known, and in humans inoculation or inhalation of as few as 10 organisms may cause severe disease. There are four recognized subspecies of F. tularensi; tularensis, holarctica, mediaasiatica, and novicida, each of which is predominantly associated with a different region of the world. Although strains from these different subspecies show a close phylogenetic relationship, they show marked variations in their virulence for mammals. Strains from subspecies holarctica (type B) or tularensis (type A) are the most clinically important.

The former subspecies is found over the whole Northern Hemisphere including Sweden, whereas the latter species is predominantly found in North America. F. tularensis subsp. holartica has been recovered from certain streams during various seasons over many years. This relatively constant contamination has led to the hypothesis that F. tularensis reproduces in aquatic environments. With the aim to clarify the natural occurrence of F. tularensis in Sweden, we have initiated field epidemiological studies in two areas; one with a history of being an endemic tularensis area, and one being an emerging endemic area. In these regions, most human patients contract the disease through mosquito bites, while ticks only occasionally are suspected to transmit the disease in Sweden. We hypothesize that protozoa are the ecological reservoir for F. tularensis, and that water-associated rodents and/or insects that hatch in water or mud propagate the infection. The current status of the project, as well as the interaction of F. tularensis with protozoa in model systems, will be presented.

Keynote speaker - Andersson S et al.: Phylogeny and Distribution of Vector-Borne Pathogens: What to Expect from Genomics?

Keynote speaker - Barbour A et al.: Interrupting transmission of Lyme borreliosis by targeting a reservoir for vaccination: a longitudinal study of a field site in North America

Keynote speaker - Broman T et al.: Campylobacter jejuni and wild birds

Keynote speaker - Broman T et al.: Natural reservoirs and vectors of Francisella tularensis in Sweden

Keynote speaker - Fouchier R: Influenza virus zoonoses

Keynote speaker - Fouchier R: A Novel Corona Virus Causing Severe Acute Respiratory Syndrome

Keynote speaker - Lundström J: Intercontinental dispersal and local adaptation of a mosquito-borne bird virus

Keynote speaker -Stervander M: Research activities and possibilities at Ottenby Bird Observatory

Bladh L et al.: Rapid detection and quantification of RNA of Crimean-Congo Hemorrhagic Fever Virus by Real-Time Reversed Transcription-PCR

Dahlgren D et al.: Survival of Campylobacter jejuni within Acanthamoeba polyphaga; a possible transmission route.

Ehrenborg C et al.: Genetic diversity over short geographic distances and no host specificity among Bartonella grahamii infecting woodland rodents of central Sweden

Ekerfelt C et al.: Involvement of cytolytic immune cells in human Lyme borreliosis - indication of intracellular persistance of the Borrelia spirochete?

Ekstrom J-O et al.: Characterization of the Ljungan virus

Haglund M: Characterization of human TBEV-strains from Sweden and a short review of the phylogenetic relationships within TBEV and Louping Ill.

Jarefors S et al.: Suppressed response to Borrelia-antigen in patients co-exposed to Borrelia burgdorferi and Anaplasma phagocytophila

Johansson M et al.: Development of molecular diagnostics for Orthopoxvirus

Mirazimi A et al.: Phatogenesis and the role of innate immunity in emerging patogen (Crimean Congo Heamorraghic fever virus)

Nejedla P et al.: A Six-year study of the presence of Borrelia burgdorferi s.l. in Ixodes ricinus ticks in the town park of Brno, Czech Republic.

Olsson G et al.: Hot zones in time and space on human hantavirus infections in northern sweden

Palo T et al.: Changing climate and emerging infectious diseases

Persson T et al.: Biological mosquito control in Sweden and risk assessment for non-target wetland insects

Schäfer M et al.: Biological diversity versus risk for mosquito nuisance and disease transmission in constructed wetlands

Shinikar S et al.: Genetic analysis of Crimean-Congo Hemorrhagic Fever virus in Iran

Skarphedinsson S et al.: Detection by PCR of Anaplasma in Danish Roe deer

Vostal K et al.: A Five-year Study of the Presence of Borrelia and Antibodies to Borrelia in Small Rodents.

Widhe M et al.: Borrelia specific IFN-γ and IL-4 secretion in CSF and blood during the course of Human Lyme Borreliosis: relation to clinical outcome

You E et al.: Host Immune Mechanisms in Recurrent Lyme Erythema Infection with Focus on the Cytokines Interleukin-4, Interferon-gamma and Interleukin-10

Zakovska A et al.: Spirochaetes and pathogenic Borrelia burgdorferi s.l. in mosquitoes (larvae and adults) in the Czech Republic