Tularaemia in Swedish wildlife: a One Health perspective

Gete Hestvik

Tularaemia in Swedish wildlife: a One Health perspective

Gete Hestvik

Publikation: Avhandling › Doktorsavhandling

14 Nedladdningar

Sammanfattning

Tularemi (harpest) orsakas av bakterien Francisella tularensis och är en zoonos som kan infektera ett stort antal värdar. Det subspecies som orsakar sjukdom i Europa är F. tularensis subsp. holarctica. Känsligheten för att insjukna varierar mellan djurslag. Skogshare (Lepus timidus) och många smågnagararter är exempel på djurarter med hög känslighet och dessa dör ofta snabbt i akut sjukdom. Många karnivorer och omnivorer visar inga sjukdomstecken efter infektion. I denna avhandling har patologiska och serologiska undersökningar utförts på några vilda djurarter. En översikt av kunskapsläget om tularemi hos människa, djur och vektorer i Europa har sammanställts ur ett One Health-perspektiv. Tularemi finns i majoriteten av Europas länder, men variationer i sjukdoms-övervakning och rapportering, ekosystem, vilda djurarter och arthropoda vektorer gör det svårt att göra direkta jämförelser mellan länderna. Patologin var likartad hos fälthare (Lepus europaeus), skogshare och två större skogsmöss (Apodemus flavicollis). De hade alla akut harpest involverande många organ. Några av fälthararna hade, förutom akuta, även subakuta eller kroniska förändringar. Detta väcker frågan huruvida fälthare i Sverige kan vara potentiell reservoar för F. tularensis. F. tularensis kunde även påvisas i muskulaturen hos infekterade harar, medförande en risk för infektion vid konsumtion av otillräckligt tillagat harkött. Många rovdjur bildar antikroppar vid infektion, vilket kan göra dem lämpliga som biologiska indikatorer för förekomsten av tularemi i ett område. Blodprover som togs i fält och förvarades och transporterades under bristfälliga förhållanden var ofta av dålig kvalitet, vilket försvårade de serologiska undersökningarna. I studien påvisades antikroppar hos brunbjörn, järv, vildsvin och rödräv. Det är första gången antikroppar mot F. tularensis påvisas hos dessa djurarter i Sverige. Denna avhandling bidrar med kunskap om tularemi i Europa, sjukdomens patologi hos fältharar, skogsharar och större skogsmöss, samt möjliga infektions- och utsöndringsvägar. Därtill bidrar arbetet till förståelsen av den roll rovdjur och asätare kan spela. Resultatet av våra studier visar vikten av att fortsätta studera vilda djurslag för att utröna deras roll i tularemins epidemiologi, och huruvida de kan utgöra potentiella infektionskällor, smittspridare och reservoarer.

Originalspråk	Engelska
Kvalifikation	Doktor i filosofi
Förlag	Swedish University of Agricultural Sciences
Tryckta ISBN	978-91-7760-096-1
Elektroniska ISBN	978-91-7760-097-8
Status	Publicerad - 2017

Nyckelord

Francisella tularensis
hare
omnivore
pathology
predator
serology
tularaemia
wildlife
yellow-necked mouse

SLU-serie

Acta Universitatis Agriculturae Sueciae

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title = "Tularaemia in Swedish wildlife: a One Health perspective",

abstract = "Tularaemia is a zoonotic disease caused by the bacterium Francisella tularensis, which may infect a wide range of hosts. The subspecies known to cause disease in Europe is F. tularensis subsp. holarctica. The susceptibility to develop disease varies between animal species. For example, mountain hares (Lepus timidus) and many small rodent species succumb to fulminate disease, while many carnivores and omnivores show no signs of clinical disease. This thesis has investigated the pathology and serology of tularemia in selected wildlife hosts. It has also reviewed the status of tularaemia in Europe in a One-Health perspective. Tularaemia is widely distributed throughout Europe. Differences in surveillance and reporting between countries, different ecosystems, the presence of different species of arthropod vectors and wildlife species, present difficulties in making direct comparisons across all of Europe. The pathology of tularaemia in European brown hares (Lepus europaeus), mountain hares and two yellow-necked mice (Apodemus flavicollis) were similar, all presenting with acute disseminated disease. However, some of the European brown hares, in addition to the acute lesions, also had subacute or chronic changes. This raises the question of whether European brown hares in Sweden might play an epidemiological role as reservoir of F. tularensis. F. tularensis was also demonstrated in muscles of infected hares, which highlights the risk of acquiring infection through consumption of under-cooked meat. Many predators and omnivores develop antibodies upon infection and therefore may be suitable sentinels of the presence of tularaemia. The study revealed seropositivity in brown bear, red fox, wild boar and wolverine, for the first time reported in Sweden. This thesis contributes to the knowledge of tularaemia in Europe, its pathology in European brown hares and yellow-necked mice, and its possible routes of infection and shedding. Additionally, it contributes to the understanding of the role of predators and scavengers. The results of our studies highlight the importance of further investigations of different wildlife species to explore their role in the epidemiology of tularaemia, as possible sources of infection, transmitters of disease and potential reservoirs.",

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