This review summarizes the literature about pathogens and predators of ticks and their potential use as biocontrol agents published since the beginning of this century. In nature, many bacteria, fungi, spiders, ants, beetles, rodents, birds, and other living things contribute significantly toward limiting tick populations, as do, for instance, the grooming activities of hosts. Experiments with the most promising potential tick biocontrol agents--especially fungi of the genera Beauveria and Metarhizium and nematodes in the families Steinernematidae and Heterorhabditidae, as well as oxpeckers--are described.

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Two previously undescribed rickettsiae were detected in Ixodes ricinus Ricketts by polymerase chain reaction. Ixodes ricinus Slovakia (IRS) 3 and IRS4 were identified in ticks collected in northeastern and southwestern Slovakia, respectively. Sequences of the 16S rRNA citrate synthase (gltA) and outer membrane protein rOmpA (ompA) encoding genes of both strains were nearly identical but were distinct from those of all other known rickettsiae. Phylogenetic relationships inferred from the comparison of these sequences with those of other members of the genus Rickettsia indicate that IRS3 and IRS4 constitute a new rickettsial genotype and form a separate cluster among the spotted fever group rickettsiae.

The name Rickettsia slovaca sp. nov. (type strain is strain B) is proposed for a member of the spotted fever group (SFG) rickettsiae which was isolated from Dermacentor marginatus ticks in Slovakia in 1968, and was recently implicated in human febrile illness. This rickettsia can be phenotypically distinguished from other SFG rickettsiae by microimmunofluorescence serotyping, SDS-PAGE, Western blotting and mAbs. Genotypic differences between R. slovaca and the other SFG representatives can be demonstrated by PCR-RFLP analysis, pulsed-field gel electrophoresis and sequencing of 16S rRNA, gltA and ompA genes.

The prevalence of ticks infected with F. tularensis was followed during a systematic surveillance in endemic area of tularemia in western Slovakia over the years 1984-93. Ticks were collected from vegetation in localities of Podunajské Biskupice, in the vicinity of the capital of Slovakia, Bratislava, near the river Danube. In total 6033 ticks, mostly adults of Dermacentor reticulatus and Ixodes ricinus (4994 and 1004, respectively) and 35 nymphs of Haemaphysalis concinna, were examined for the presence of F. tularensis. Out of 4542 starving ticks, 34 F. tularensis strains were isolated predominantly from D. reticulatus (30), and to a smaller extent also from I. ricinus (3) and H. concinna (1). Natural infection with F. tularensis was further proved from 1491 adults of D. reticulatus fed on laboratory animals, rabbits and white mice, together in 27 cases. From that, 21 times it was by positive isolation either from suspensions of partly or fully engorged ticks and their feaces, or from spleens of animals dead after the feeding of ticks. In addition, solely the development of antibodies against the agent was confirmed in 6 rabbit hosts. The presence of F. tularensis in all the above mentioned tick species and namely the relatively high and permanent infestation of D. reticulatus adults, ranging between 0.5-2% during the followed time period, demonstrated the maintenance of active natural focus of tularemia in the area under study. The present paper also emphasizes the epidemiologic consequence of various species of ticks in endemic foci of tularemia and the aspect of possible ways of transmission of the agent to humans.

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Between 1987-1989 almost 7000 adult Ixodes ricinus, Dermacentor reticulatus, Dermacentor marginatus, Haemaphysalis concinna, Haemaphysalis punctata and Haemaphysalis inermis ticks collected in all 38 districts of Slovakia were screened for the presence of Coxiella burnettii. The proportion of ticks containing C. burnetii as indicated by the haemocyte test was less than 3%. Attempts to recover C. burnetii by inoculation of yolk sacs of embryonated hen eggs from pools of 1-6 specimens of haemocyte test positive ticks resulted in the isolation of 10 rickettsial strains. Six strains were recovered from I. ricinus, the remaining ones from single pools of D. reticulatus, D. marginatus. H. concinna and H. inermis ticks. In addition to the previous recovery of C. burnetii from H. punctata ticks, the agent was thus isolated from all important ticks living in Slovakia. The agent was found in tick habitats regardless of the latitude and altitude in the entire country. These results are not consistent with the negligible number of Q fever cases occurring in past years in Slovakia.

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