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PubMed1992

Epidemiology and ecology of tick-borne encephalitis in the eastern part of Germany between 1960 and 1990 and studies on the dynamics of a natural focus of tick-borne encephalitis.

From 1960 to 1990, attempts to isolate TBE virus from ticks and small mammals were made and investigations to detect TBE antibody in small mammals, game and humans were performed in the five new federal Länder of Germany. The confirmed TBE cases for which the site of exposure could be determined were also registered. As a result of these epidemiological and ecological investigations, a map is presented showing the natural foci of TBE which are primarily located in the subatlantic and mountainous climatic regions. TBE was endemic in the area of investigation from 1960 to 1990 showing a morbidity of up to 0.7 per 100,000 inhabitants which decreased in recent years to 0.02 per 100,000 inhabitants. The natural foci of TBE virus in eastern Germany showed a high activity between 1960 and 1970. Since that time, there have hardly been any cases of human disease and TBE virus could no longer be detected, neither in ticks nor in small mammals. Taking the natural focus on the Island of Usedom as an example, attempts have been made to elucidate whether such foci have become extinct or whether they have persisted. From 1983 to 1989, a surveillance programme was performed to detect antibodies to TBE virus in small mammals and game and to attempt to culture virus from ticks and small mammals. The attempts to isolate virus from a total of 8200 ticks were negative. Attempts to isolate virus from the brains of small mammals were also negative. Antibody prevalence in 446 small mammals and 500 animals of game was ca. 1%. At one site, the sero-positive reactions converted from 0% (1983-1988) to 4.5% (1989) among small mammals population. The investigations performed on the Island of Usedom have shown that this natural focus has not disappeared but is in a state of endemic latency. Moreover, the seroconversion observed in the small mammals population shows that further surveillance of such foci is necessary. This becomes obvious by the sporadic occurrence of single TBE cases as well as by a low antibody prevalence of 1% in small mammals and game. The epidemiological situation in eastern Germany is thus completely different from that in western Germany where an average of 70-120 TBE cases per year are registered, occurring mainly in Bavaria and Baden-Württemberg.

Animals↗
PubMed1998

Traffic of the tick embryo basic protein during embryogenesis of the camel tick Hyalomma dromedarii (Acari: Ixodidae).

The tick embryo basic protein (TEBP) is present in the nucleus as a counterpart of histones at early embryonic stages of the tick Hyalomma dromedarii. The sharp drop in the TEBP nuclear level and elimination of the N-terminal dipeptide (leucine-serine) between days 12 and 15 after oviposition suggested the transport of TEBP to the cytoplasm for protein turnover. The traffic of TEBP during tick embryogenesis was examined. The level of TEBP was detected in the cytoplasm from the different embryonic stages by the established enzyme-linked immunosorbent assay (ELISA) and confirmed by immunoblotting. At day 12, a 2-fold increase in the cytoplasmic TEBP level coincided with its decrease in the nucleus. This result indicates that TEBP starts to leave the nucleus for the cytoplasm at day 12. The changes in the cytoplasmic leucine aminopeptidase (LAP)-specific activity were followed during tick embryogenesis. The LAP activity started to increase at day 12 and reached its maximum level at day 21. The enzyme displayed an optimum pH between 7.5 and 8.8 and a K(m) value of 0.5 microM for leucine-p-nitroanilide. The involvement of the exopeptidase activity in the TEBP turnover after its translocation to the cytoplasm is discussed.

Amino Acid Sequence↗
PubMed2003

RNA interference in ticks: a study using histamine binding protein dsRNA in the female tick Amblyomma americanum.

RNA interference (RNAi), a gene silencing process, has been recently exploited to determine gene function by degrading specific mRNAs in several eukaryotic organisms. We constructed a double stranded RNA (dsRNA) from a previously cloned putative Amblyomma americanum histamine binding protein (HBP) to test the significance of using this methodology in the assessment of the function and importance of gene products in ectoparasitic ticks. The female salivary glands incubated in vitro with HBP dsRNA had a significantly lower histamine binding ability. In addition, the injection of HBP dsRNA into the unfed females led both to a reduced histamine binding ability in the isolated salivary glands and to an aberrant tick feeding pattern or host response. Molecular data demonstrated less expression of the HBP mRNA in the RNAi group. Taken together, these results suggest that RNAi might be an important tool for assessing the significance of tick salivary gland secreted proteins modulating responses at the tick-host interface.

Animals↗
PubMed1995

Bacteriocidal qualities of ixodid tick (Acarina: Ixodidae) salivary cement plugs and their changes under the influence of a viral tick-borne pathogen.

The abundance of bacteriocidal compounds contained in the salivary cement plug of ixodid ticks was changed because of the reproduction of tick-borne encephalitis virus (TBEV) in their bodies. The size of TBEV-infected Ixodes persulcatus Shulze lytic zone surrounding the cement plug enlarged to that of naive ticks, whereas Micrococcus lysodeikticus (Cohn) lytic zones induced by the cement plugs of TBEV-infected Amblyomma hebraeum Koch nymphs or Rhipicephalus appendiculatus Neumann females were reduced, compared with those produced by noninfected specimens. It is possible that an increase of lysozyme production by the primary TBEV vectors (Ixodinae) infected salivary gland cells, compared with suppression of the bacteriocidal qualities of saliva of ticks that are not TBEV vectors in nature (Amblyomminae), is an indication of the specificity of a I. persulcatus-TBEV interface.

Animals↗
PubMed2001

The shifting landscape of tick-borne zoonoses: tick-borne encephalitis and Lyme borreliosis in Europe.

The two major vector-borne diseases of northern temperate regions, tick-borne encephalitis (TBE) and Lyme borreliosis (LB), show very different epidemiological patterns, but both have increased significantly in incidence since the 1980s. Insight into the temporal dynamics of TBE, gained from statistical analysis of spatial patterns integrated with biological explanation, suggests that the recent increases in TBE cases in Central Europe and the Baltic States may have arisen largely from changes in human behaviour that have brought more people into contact with infected ticks. Under forecast climate change scenarios, it is predicted that enzootic cycles of TBE virus may not survive along the southern edge of their present range, e.g. in Slovenia, Croatia and Hungary, where case numbers are indeed decreasing. New foci, however, are predicted and have been observed in Scandinavia. At the same time, human impact on the landscape, increasing both the habitat and wildlife hosts of ticks, has allowed tick populations to multiply significantly. This probably accounts for a genuine emergence of LB, with its high potential transmission rate, in both the USA and Europe, although the rate of emergence has been exaggerated by improved surveillance and diagnosis.

Animals↗
PubMed1987

In vivo reassortment of Thogoto virus (a tick-borne influenza-like virus) following oral infection of Rhipicephalus appendiculatus ticks.

Arboviruses with segmented genomes have the potential to reassort in both their vertebrate hosts and arthropod vectors. Reassortment of Thogoto virus, a tick-borne orthomyxo-like virus, has been demonstrated following dual infection of hamsters by temperature-sensitive mutants. To investigate whether similar events can occur in ticks, Rhipicephalus appendiculatus larvae and nymphs were dually infected by interrupted feeding on viraemic hamsters. Wild-type reassortant virus was isolated from the ticks 12 to 15 days after engorgement. Following moulting, nymphs and adults transmitted reassortant virus to uninfected hamsters. This is the first reported evidence that a tick-borne arbovirus can reassort in vivo in a naturally infected arthropod vector. The relative roles of vector and vertebrate host in generating and perpetuating reassortant viruses in nature are discussed.

Animals↗
PubMed1986

Amitraz: a tick and flea repellent and tick detachment drug.

A topical formulation of amitraz (Mitaban Liquid Concentrate, The Upjohn Company, Kalamazoo, Michigan, U.S.A.) was evaluated as a tick repellent and detachment agent, and flea repellent. The diluted liquid concentrate (250 p.p.m. active drug) was topically applied as a single treatment to dogs; the concentration was identical to the rate recommended for treatment of demodicosis and scabies. Brown dog tick (Rhipicephalus sanguineus) and American dog tick (Dermacentor variabilis) populations were eliminated and repelled. Repellent activity (92-95%) was observed against R. sanguineus for 2 weeks post-treatment; the treatment was moderately active (63%) during the third week, and at 4 weeks post-treatment the drug was inactive. Established R. sanguineus populations were also treated, and the diluted liquid concentrate had 100% tick-detachment efficacy. Repellent activity (99%) was also detected against D. variabilis; the activity was monitored for only 7 days. The ectoparasiticide had low to moderate flea (Ctenocephalides felis) repellent activity (42%) for 4 days post-treatment; thereafter the treatment was ineffective. Side-effects were not observed in any of the dogs treated with amitraz, or the placebo.

Administration, Topical↗
PubMed1997

Infestation with pathogen-free nymphs of the tick Ixodes scapularis induces host resistance to transmission of Borrelia burgdorferi by ticks.

Female BALB/c mice were infested four times with pathogen-free Ixodes scapularis nymphs prior to infestation with nymphs infected with Borrelia burgdorferi B31. Each infestation was separated by a 14-day tick-free period. Mean weights of fed ticks and percentage reaching repletion did not indicate development of acquired resistance. Only 16.7% of mice repeatedly infested with pathogen-free ticks prior to infected I. scapularis nymph challenge became positive for B. burgdorferi. One hundred percent of control mice infested only with infected ticks were culture positive for B. burgdorferi.

Animals↗
PubMed1996

Comparison of infectivities of six tick-derived isolates of Borrelia burgdorferi for rodents and ticks.

The infectivity and dissemination to the skin of six isolates of Borrelia burgdorferi were evaluated by inoculating them into groups of deer mice (Peromyscus maniculatus), hamsters, and Swiss Webster mice. Rodent infection was assayed by culture of ear punch biopsy specimens taken at 4, 8, and 12 weeks postinoculation (p.i.). Spirochetes were detected in biopsy specimens from individuals of all three host species that had been inoculated with four isolates (CA3, CA4, CA7, and CA8). Ear punch biopsy specimens taken from Swiss Webster mice at 12 weeks p.i. yielded an additional reisolate (CA2), even though these animals did not seroconvert. The remaining isolate (CA9) was not recovered from any host. However, two deer mice and all hamsters and Swiss Webster mice inoculated with CA9 seroconverted. All six isolates were of low infectivity to ticks when inoculated intramuscularly into hosts. Only 4 (1.6%) of 250 Ixodes pacificus larvae acquired and transstadially maintained infection from hosts inoculated intramuscularly. Infectivity of three isolates for ticks also was tested in Swiss Webster mice injected intradermally. The mean prevalences of infection in xenodiagnostic ticks fed on these mice at 4 weeks p.i. were 47.9, 1.2, and 2.2% for isolates CA4, CA7, and CA8, respectively. The mean prevalences of infection for ticks fed on the same mice at 12 weeks p.i. were 36.4, 11.8, and 20.4%, respectively. Such differences in the infectivity and rate of dissemination of individual isolates of B. burgdorferi should be considered during studies of reservoir and vector competence.

Animals↗
PubMed2002

PCR detection of Borrelia burgdorferi sensu lato, tick-borne encephalitis virus, and the human granulocytic ehrlichiosis agent in Ixodes persulcatus ticks from Western Siberia, Russia.

PCR assays were used to test adult Ixodes persulcatus ticks from Western Siberia, Russia, for Borrelia burgdorferi sensu lato, tick-borne encephalitis virus (TBEV), and the human granulocytic ehrlichiosis (HGE) agent. Of the 150 ticks that were studied, 38% were infected with B. burgdorferi, 46% were infected with TBEV, and 8% were infected with the HGE agent. These three pathogens were distributed in the ticks independently of one another.

Animals↗
PubMedDate not supplied

[The clinical features of the acute period of mixed infection of tick-borne encephalitis and Ixodes tick-borne borreliosis in children].

The paper presents the results of a study of 176 cases of mixed infection of tick-borne encephalitis and Ixodes tick-borne borreliosis in children in the Kuznetsk coal fields. The mixed infection presented as meningeal, meningoencephalitic, and feverish forms. Mixed infection is characterized by a severe course and it is not attended by the symptoms that are characteristic for monoinfections, which requires the immunological verification of their diagnosis. Unlike tick-borne encephalitis, the meningeal and meningoencephalitic forms of the mixed infection are marked by the great magnitude and duration of a temperature reaction and overall cerebral and focal manifestations. The outcome is characterized by the formation of symptoms of chronic tick-borne encephalitis in 25% of the cases of the meningoencephalitic form of the mixed infection.

Acute Disease↗
PubMed1991

Preliminary observations on ticks and tick-borne diseases in the north west province of Cameroon. I. Babesiosis and anaplasmosis.

During a survey on ticks and tick-borne diseases in the North-Western Cameroon at the Bamenda cattle market, the ticks identified were Boophilus annulatus (20%) and B. decoloratus (80%). More than 50% of the ticks were collected during the dry season. Of 524 blood smears 47.3% were positive for Babesia bovis, 31.1% for B. bigemina and 2.2% for Anaplasma marginale. 19.4% were negative.

Anaplasmosis↗
PubMed1991

Tick-bite fever in Zimbabwe. Survey of antibodies to Rickettsia conorii in man and dogs, and of rickettsia-like organisms in dog ticks.

As part of a study of tick-bite fever in Zimbabwe, the prevalence of antibodies to Rickettsia conorii in dogs and humans was examined. Blood samples were obtained from 184 dogs in different parts of the country and tested by indirect immunofluorescence. In all, 150 (82%) were positive at a titre of 1/40 or higher. Dogs from the south and east of the country showed very high seroprevalence compared with dogs from the main urban centre, Harare. Human serum was obtained from blood donors, from people attending clinics with non-febrile illness and from agricultural workers. Antibodies to R. conorii were found in a high proportion of samples from the south and east, with 100% of blood donor samples in one area being positive. As with the dogs, a much lower proportion of samples from Harare were positive. The exact role of dogs and their ticks (Rhipicephalus sanguineus, R. simus and Haemaphysalis leachi) in the epidemiology of human tick-bite fever remains unclear, since dog ticks were seldom found to harbour rickettsia-like organisms and man is not one of their preferred hosts. While dogs may be of little importance in disease transmission, their value as sentinels of spotted-fever group rickettsias in the environment was confirmed.

Animals↗
PubMed1979

Resistance to tick-borne Francisella tularensis by tick-sensitized rabbits: allergic klendusity.

Mammals become hypersensitive to ticks that feed upon them. That hypersensitivity was thought responsible for an observation that a large number of Francisella tularensis-infected Dermacentor variabilis failed to infect a rabbit previously exposed to ticks of that species. In a series of tests of that hypothesis, rabbits sensitized to ticks were often significantly more resistant than control animals to tick-borne tularemia. The conditions that determine the klendusity are thought to be variable and complex but the phenomenon must be of importance in the epidemiology of some arthropod-borne agents.

Animals↗
PubMed1993

Amplification of tick-borne encephalitis virus infection during co-feeding of ticks.

Following engorgement of Rhipicephalus appendiculatus larvae on guinea-pigs infected with tick-borne encephalitis (TBE) virus, none of the engorged larvae or emergent nymphs contained detectable infectious virus. However, one of twelve pools, each containing three of the unfed nymphs, was positive when screened by polymerase chain reaction (PCR), indicating a low prevalence of TBE virus infection in the unfed nymphs. After engorgement of the nymphs on four uninfected guinea-pigs, 19/24 (79%) fed nymphs from one guinea-pig and 4/25 (16%) fed nymphs from a second guinea-pig were infected; all the ticks examined from the other two guinea-pigs were uninfected. The results suggest that TBE virus was transmitted from a low proportion of infected nymphs (infected as larvae) to uninfected nymphs as they fed together on an uninfected guinea-pig. Such amplification of the initial infection, at the population level, could play an important role in maintaining TBE virus infections in nature, particularly if there is a low level of vertical transmission from one tick generation to the next.

Animals↗
PubMedDate not supplied

[Interrelations between Ixodes persulcatus ticks and the tick-borne encephalitis virus of the red vole (Clethrionomys rutilis) in western Siberia].

We present the data of 12-year survey (1989-2001) of the red vole population in southeastern West Siberia, including estimation of host relative numbers, abundance of immature taiga ticks, and percentage of animals with antigemagglutitnins against tick-borne encephalitis (TBE) virus. We discuss the role of demographic groups of voles as tick's hosts and their participation in the maintenance of TBE causative agent population. The estimation of spontaneous TBE infection rate in summer as well as in winter and early spring seasons, which have been made using a set of molecular-biological, serological and virological methods, demonstrates that a high proportion of red voles maintain non-pathogenic TBE causative agent over a long time, presumably, in the form of persistent infection.

Animals↗
PubMedDate not supplied

[The experimental transmission of the tick-borne encephalitis virus by ixodid ticks (the mechanisms, time periods, species and sex differences)].

Females and males of ixodid ticks (Ixodes and Dermacentor) infected parenterally with the tick-borne encephalitis virus at the adult or nymphal phase and containing the virus in the saliva are able to transmit the agent in the first minutes after the bite of the sensitive animal host. Preservation of the cement conus produced by saliva in the animal skin enhances the infection intensity because the quantity of the virus in the conus is comparable with that in the tick's body. The virus quantity in the fluid saliva, excreted by I. persulcatus females and measured during different periods of bloodsucking (at least during the first three days), increases 10 to 100 times in comparison with a comparable volume of hungry ones.

Animals↗