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Investigation of the ecological cycle of Francisella tularensis in an enzootic area, during an inter-epizootic period
Remport Ágnes - year 5
SzIU, Faculty of Veterinary Science, Department of Microbiology and Infectious Diseases
Supervisor: Miklós Gyuranecz DVM


The aim of the study was the direct and indirect detection of Francisella tularensis in potential animal reservoirs, domestic animals, arthropod vectors and natural waters in order to obtain data about the ecological cycle of F. tularensis in an enzootic area (Dévaványa-Ecseg, Körös-Maros National Park) during an inter-epizootic period.

197 European brown hares (Lepus europaeus) shot during the annual hunting events were screened with F. tularensis specific slide and tube agglutination tests. Seropositive hares were necropsied, submitted for histological, immunohistochemical examinations and F. tularensis strains were isolated from tissue samples through mouse passage. 177 small mammals including 38 common voles (Microtus arvalis), 110 yellow-necked mice (Apodemus flavicollis), 15 striped field mice (Apodemus agrarius) and a by-catch of 8 Eurasian pygmy shrews (Sorex minutus) and 6 common shrews (Sorex araneus) were live-trapped in woodland and grassland habitats. The blood samples of these small mammals were screened by slide agglutination test, in addition lung, liver, spleen and kidney tissue pools were taken from each individual. 250 ml water samples were taken from all the existing seven water sources, filtered on 0.2 µm membrane filters, and these filters such as the small mammal tissue pools were analyzed by using a F. tularensis specific real-time TaqMan polymerase chain reaction (PCR) system. 1106 Ixodes ricinus and 476 Haemaphysalis concinna ticks were collected from the vegetation and 404 I. ricinus, 28 H. concinna ticks and 15 Ctenophtalmus assimilis and 10 Nosopsyllus fasciatus fleas were combed off the small mammals sorted to each individual and tested by real-time TaqMan PCR. Furthermore, blood samples were taken from 100 sheep, 50 cattle and 50 buffalos grazed at the study area and were screened by both slide and tube agglutination tests.

The seroprevalence of tularemia in the European brown hare population was 5,1% (10/197) with low antibody titers (1/10 and 1/20) and tularemic lesions demonstrating in-situ F. tularensis specific immunolabelling were identified in each individual. F. tularensis ssp. holarctica was isolated from four hares. Bacteria were not detected in small mammals and water samples. One H. concinna female and one nymph collected from the vegetation was found infected with F. tularensis ssp. holarctica thus resulting a 0.39 % (2/504) prevalence. The examined ruminants grazed at the study area were all seronegative.

We would recommend considering the modification of the diagnostic titer in tube agglutination test to 1/10 for screening European brown hares. According to our results during inter-epizootic periods F. tularensis ssp. holarctica seems to persist only in European brown hare and H. concinna at the studied habitat. H. concinna may not serve exclusively as an arthropod vector but it may also harbor bacteria for three-four years through multiple life stages and act as an important reservoir of F. tularensis. Rodent species probably do not serve as true reservoir hosts of tularemia in the study area.

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