[Analysis of the incidence of tularemia in the Breclav District 1994-1999]. / Analýza výskytu tularémie na okrese Breclav v letech 1994-1999.

Southern Moravia is one of the areas where there are long-term natural foci of tularaemia. In 1994 in the Breclav district an exacerbation of the disease was recorded in hares. During autumn hunts a positive reaction was recorded in 5.75% of examined hares. An elevated seropositivity persisted also in subsequent years and at the same time a higher human morbidity in the mentioned region. The objective of the investigation was to assess the causes and circumstances which led to the exacerbation of old known but in recent years quiescent foci in the mentioned region. To this end 350 small terrestrial mammals were examined. In one case it proved possible to detect the causal agent in Microtus arvalis. By examination of arthropods it proved possible to isolate 33 strains, i.e. 32 strains from ticks Dermacentor reticulatus and one strain from Ixodes ricinus. The results of the examination revealed that tularaemia as a classical infection with a natural focus may persist in areas where there are prerequisites for survival of the causal agent in the environment. One of the important factors of the environment are susceptible individuals (hares, small terrestrial mammals) as well as blood sucking arthropods as vectors of the disease.

Frequent isolation of Francisella tularensis from Dermacentor reticulatus ticks in an enzootic focus of tularaemia.

A total of 924 questing Dermacentor reticulatus (Fabricius), 504 Ixodes ricinus (L.), sixty Haemaphysalis concinna Koch and 718 mosquitoes (Aedes spp.) were examined in a floodplain forest ecosystem during the 1994-95 outbreak of tularaemia in South Moravia, Czech Republic. Francisella tularensis was not isolated from H.concinna ticks or Aedes spp. mosquitoes, whereas twenty-one isolates were recovered from the other haematophagous arthropods. Dermacentor reticulatus revealed a significantly higher infection rate (2.6%) than I.ricinus (0.2%). This tick species acts as principal vector for tularaemia in the enzootic focus. Monitoring of D.reticulatus for F.tularensis thus seems to be a very efficient approach in the surveillance of tularaemia in the flood-plain forest ecosystems of Europe.