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PubMed2000

Impact of climatic change on the northern latitude limit and population density of the disease-transmitting European tick Ixodes ricinus.

We examined whether a reported northward expansion of the geographic distribution limit of the disease-transmitting tick Ixodes ricinus and an increased tick density between the early 1980s and mid-1990s in Sweden was related to climatic changes. The annual number of days with minimum temperatures above vital bioclimatic thresholds for the tick's life-cycle dynamics were related to tick density in both the early 1980s and the mid-1990s in 20 districts in central and northern Sweden. The winters were markedly milder in all of the study areas in the 1990s as compared to the 1980s. Our results indicate that the reported northern shift in the distribution limit of ticks is related to fewer days during the winter seasons with low minimum temperatures, i.e., below -12 degrees C. At high latitudes, low winter temperatures had the clearest impact on tick distribution. Further south, a combination of mild winters (fewer days with minimum temperatures below -7 degrees C) and extended spring and autumn seasons (more days with minimum temperatures from 5 to 8 degrees C) was related to increases in tick density. We conclude that the relatively mild climate of the 1990s in Sweden is probably one of the primary reasons for the observed increase of density and geographic range of I. ricinus ticks.

Animals↗
PubMed2006

Two secreted cystatins of the soft tick Ornithodoros moubata: differential expression pattern and inhibitory specificity.

Two genes coding for cysteine peptidase inhibitors of the cystatin family (Om-cystatin 1 and 2) were isolated from a gut-specific cDNA library of the soft tick Ornithodoros moubata. Both cystatins were clearly down-regulated after a blood meal. Om-cystatin 1 is mainly expressed in the tick gut, while Om-cystatin 2 mRNA was also found in other tick tissues. Authentic Om-cystatin 2 was significantly more abundant than Om-cystatin 1 in the gut contents of fasting ticks and was associated with hemosome-derived residual bodies accumulated in the gut lumen. Om-cystatin 2 was also expressed by type 2 secretory cells in the salivary glands of unfed ticks. The inhibitory specificity of recombinant Om-cystatins 1 and 2 was tested with mammalian cysteine peptidases, as well as endogenous cysteine peptidases present in the tick gut. Both cystatins efficiently inhibited papain-like peptidases, including cathepsin B and H, but differed significantly in their affinity towards cathepsin C and failed to block asparaginyl endopeptidase. Our results suggest that the secreted cystatin isoinhibitors are involved in the regulation of multiple proteolytic targets in the tick digestive system and tick-host interaction.

Amino Acid Sequence↗
PubMed2001

Testosterone depresses innate and acquired resistance to ticks in natural rodent hosts: a force for aggregated distributions of parasites.

The effects of testosterone on acquired resistance to ticks, Ixodes ricinus, in their natural rodent hosts (voles, Clethrionomys glareolus, and wood-mice, Apodemus sylvaticus) were investigated by manipulating testosterone levels and exposing the hosts to repeated tick infestations. Testosterone reduced both innate and acquired resistance to tick feeding. During primary infestations, attachment rates were higher on rodents with high testosterone levels than on oil-implanted controls. Successive infestations on voles were accompanied by a decrease in tick feeding success and survival, but this decrease was significantly greater in ticks fed on control voles than in those fed on voles implanted with testosterone. When reduced feeding success had been induced, either by vaccination with tick salivary gland extract or by 4 successive infestations, implantation with testosterone partially reversed the acquired resistance. These effects of testosterone will generate heterogeneities within the rodent population with respect to tick distribution and microparasite transmission. The lowest innate and acquired resistance to tick feeding occurs in that fraction of the host population, i.e., sexually active males, most actively involved in the transmission of both Babesia microti and Borrelia burgdorferi s.l.

Animals↗
PubMed1989

Experimental studies on the replication and transmission of Crimean-Congo hemorrhagic fever virus in some African tick species.

Seven African tick species were studied as potential vectors of Crimean-Congo hemorrhagic fever (CCHF) virus. Engorged nymphae of 4 ixodid species, Hyalomma marginatum rufipes, H. truncatum, Rhipicephalus evertsi mimeticus, and Amblyomma hebraeum, were inoculated intracoelomically with CCHF virus and assayed for virus content at varying times post-inoculation. The virus replicated in all 4 species, reaching maximum titers of 4.6-5.5(10) fluorescence focus units per ml on days 5-9 post-inoculation. Virus titers declined up to the molt, but increased slightly on emergence of adult ticks. Thereafter, virus titers declined progressively, but infectivity could still be detected in adult ticks for up to 205 days post-inoculation. Groups of H. m. rufipes, H. truncatum, and R.e. mimeticus infected adults were fed on susceptible sheep and successfully transmitted CCHF infection. CCHF virus was not isolated from pools of the larval and nymphal progeny of the female ticks nor did the larvae transmit infection to guinea pigs by bite. CCHF virus failed to replicate in adults and nymphae of 3 argasid tick species, Argas walkerae, Ornithodorus porcinus porcinus, and O. savignyi, after intracoelomic inoculation and could be reisolated from the ticks no later than 1 day post-inoculation. The results suggest that all ixodid ticks are capable of transmitting CCHF virus but argasid ticks do not appear to be capable of serving as vectors.

Animals↗
PubMed1992

Spotted fever rickettsiae in ticks from the northern Sinai Governate, Egypt.

A field study was initiated in 1988 to investigate whether spotted fever group rickettsiae occur in geographic areas in Egypt that are adjacent to an area in the southern Israeli Negev that has a defined focus of spotted fever disease. Ticks were collected from dogs, sheep, and camels at four study sites in the northern Sinai. Tick hemolymph was processed for rickettsial detection by staining with fluorescein isothiocyanate-conjugated antibody to Rickettsia rickettsii. Of the 442 hemolymphs examined, 15 contained immunofluorescent rickettsiae. Eight hemolymph test-positive (HT+) ticks were Rhipicephalus sanguineus removed from dogs; the other HT+ ticks comprised three Hyalomma species, H. anatolicum, H. impeltatum, and H. dromedarii. Both HT+ and HT- ticks were tested for rickettsial DNA using the polymerase chain reaction (PCR). Eight of 10 HT+ field-collected ticks were PCR positive (PCR+). All laboratory colony R. rickettsii-infected ticks were PCR+. No HT- ticks from field or laboratory isolates were PCR+.

Animals↗
PubMed2000

SALP16, a gene induced in Ixodes scapularis salivary glands during tick feeding.

Guinea pigs infested with Ixodes scapularis acquire antibody-mediated resistance to tick bites, a phenomenon known as tick-immunity. An I. scapularis salivary gland cDNA expression library was therefore probed with sera from tick-immune guinea pigs to identify antigens that elicit humoral responses in the host. Sera from sensitized guinea pigs strongly recognized 3 of 4,500 library clones in an initial screening. The open reading frames of all 3 clones encoded a putative 16.4-kD acidic protein, designated Salp16, with an N-terminal signal sequence and signal peptidase cleavage sites specific for secretory proteins. The salp16 mRNA and Salp16 protein were detected in the salivary glands of engorged, but not unfed, nymphal and adult ticks, and Salp16 was also found in the saliva of engorged ticks. Immunization with recombinant Salp16 induced high antibody titers in guinea pigs, but did not elicit tick-immunity. Salp16 is the first feeding inducible gene that has been cloned from L. scapularis. Molecular characterization of I. scapularis salivary antigens that are induced upon tick feeding should help to facilitate our understanding of tick-host interactions.

Amino Acid Sequence↗
PubMed1999

Dispersal and distribution of the tick Ixodes uriae within and among seabird host populations: the need for a population genetic approach.

The aim of this study was to characterize the spatial distribution of the tick Ixodes uriae within and among populations of its seabird hosts and to consider the potential insight that could be gained by a population genetic approach to the issue of dispersal of this tick. Analyses of data collected around the Avalon Peninsula, Newfoundland, indicated that both the prevalence and mean abundance of ticks varied significantly among sample locations. Whereas ticks were found on all 4 host species examined (Rissa tridactyla, Uria aalge, Alca torda, Fratercula arctica), infestation prevalence and mean abundance differed among the species. On R. tridactyla, ticks were significantly aggregated at the among-nest scale and nestling infestation was spatially autocorrelated. Conversely, ticks were not aggregated among chicks within nests. These results enabled us to make a priori predictions regarding tick dispersal and host specificity and suggest there may be spatial structure of Ixodes uriae populations at both macro- and microgeographic scales. Investigating the population genetic structure of ticks within and among populations of hosts with different breeding biologies should provide direct insight into the metapopulation dynamics of such a spatially structured system.

Animals↗
PubMed1975

[Studies on the retention of R. burneti in Rh. bursa and H. detritum ticks].

The role played by ixodes ticks in the epizootiology and epidemiology of Q fever was studied by following up the transphasal and transovarial passing of Rickettsia burnetii in ticks of the Rhipicephalus bursa and Hyalomma detritum species. Use was made of the 269th passage of the rickettsial strain BP, isolated in this country from sheep. The infection was followed up from larva Ist generation to larva IInd generation of the two ticks. In 10 out of the eleven samples of ticks studied there were rickettsiae in all developmental stages of the ticks, and this pointed to the phase transmission of strain BP via the metamorphosis. Of all 16 samples of eggs and second generation larvae of infected ticks, three egg samples were positive of both species of ticks, and one samples of larvae was positive of H. detritum ticks. Results showed that the infection may be passed transovarially, however, in a comparatively low per cent.

Animals↗
PubMed2002

Tick-borne lymphadenopathy (TIBOLA).

INTRODUCTION: From 1996 through 2000, we collected data on 86 patients with similar symptoms following a tick bite. The inclusion criteria were: enlarged regional lymph nodes and/or vesicular-ulcerative local reaction at the site of the tick bite. METHODS: Epidemiological and clinical data on these 86 patients were statistically analysed. All patients were tested for borrelia and 73 cases for Rickettsia slovaca antibodies by immunoblot. Fine-needle lymph node and/or skin biopsy was done in 13 patients. Gehomic PCR amplification was performed on these biopsy samples. RESULTS: Seventy-six patients described an "extremely big" tick, and/or recognised a Dermacentor spp. tick from a collection of several species indigenous to Hungary. The tick bite was usually (96%) located on the scalp region. The time from the recognition of the tick bite to the first symptom varied between 0 and 55 (mean nine) days. A characteristic local reaction (eschar) was seen in 70 (82%) patients. The eschar can be surrounded by a circular erythema (18 cases, 21%). The other main symptoms are the enlarged and sometimes painful lymph nodes in the region of the tick bite, characteristically in the occipital region and/or behind the sternocleidomastoideal muscle. The most frequent general symptoms were low-grade fever, fatigue, dizziness, headache, sweat, myalgia, arthralgia, and loss of appetite. Without treatment, the symptoms were seen to persist for as long as 18 months. One of the patients reported symptoms suggestive of encephalitis. The infection occurs most commonly in young children (age range: 2-57 years, mean: 12.6 years, 63% less than 10 years of age). A female predominance was registered (50/36). Doxycycline treatment can shorten the usually benign illness. R. slovaca PCR gave positive results from skin or lymph node biopsy samples in 10/13 (77%) patients. CONCLUSION: We have described a new and frequent tick-borne infection, most probably caused by R. slovaca.

Adolescent↗
PubMed2004

[Doubling of the number of cases of tick bites and lyme borreliosis seen by general practitioners in the Netherlands].

OBJECTIVE: To obtain detailed information about the current geographical distribution and incidence of tick bites and Lyme borreliosis in the Netherlands and to identify regional differences in the ecological risk factors that might be involved. DESIGN: Retrospective questionnaire study. SETTING: All Dutch general practitioner's (GP) practices. METHODS: In April 2002, all GPs in the Netherlands were asked to complete a short questionnaire on the number of cases of tick bites and erythema migrans seen in 2001 and the size of their practice. Associations with possible risk factors were determined at the municipal level. Results were compared with the results of a similar study done in 1995. RESULTS: The response of the GPs was 64.5% (4730/7330). Together, all GPs reported seeing approximately 61,000 patients in 2001 with tick bites and 12,000 patients with erythema migrans. The incidence of erythema migrans was estimated at 73 per 100,000 inhabitants. There were obvious risk areas. At the municipal level, tick bites and erythema migrans were positively associated with the area covered by forest, sandy soil, the number of roe deer and tourism. There was a negative association with the degree of urbanisation. Increases in tourism in areas with many ticks, new forests in urban regions and an increased number of horses were positively associated with the increase in tick bites and erythema migrans since 1994. CONCLUSION: The number of patients with tick bites and erythema migrans seen by GPs in the Netherlands had doubled between 1994 and 2001. This increase may be attributed partly to changes in ecological risk factors and human behaviour. The number of cases of Lyme borreliosis may be reduced by giving prophylactic information annually about ticks and ways to remove them, plus additional education of patients about the recognition of erythema migrans.

Animals↗
PubMed2005

Immunization of mice with recombinant P27/30 protein confers protection against hard tick Haemaphysalis longicornis (Acari: Ixodidae) infestation.

The success of immunological control methods is dependent upon the use of potential key antigens as tick vaccine candidates. Previously, we cloned a gene encoding 27 kDa and 30 kDa proteins (P27/30) of Haemaphysalis longicornis, and identified the P27/30 is a troponin I-like protein. In this study, the recombinant P27/30 (rP27/30) expressed in Escherichia coli was used to immunize mice and the mice were challenge-infested with ticks at different developmental stages of the same species. The rP27/30 protein stimulated a specific protective anti-tick immune response in mice, evidenced by the statistically significant longer pre-feeding periods in adult ticks. Furthermore, significantly longer feeding periods were noted in both larval and adult ticks. On the other hand, only larval ticks exhibited low attachment rates (31.1%). Immunization of mice with rP27/30 protein confers protection against hard tick Haemaphysalis longicornis infestation. These results demonstrated that the rP27/30 protein might be a useful vaccine candidate antigen for biological control of ticks.

Animals↗
PubMed2006

[Epidemiology of tick-borne diseases in Poland].

The paper summarizes state of art knowledge on tick-borne diseases epidemiology in Poland. The most prevalent diseases are Lyme borreliosis (LB) and tick-borne encephalitis (TBE). Although there is growing number of data published on anaplasmosis and babesiosis prevalence in ticks and humans, there is no national data on these diseases and their epidemiological features remain unclear. All tick-borne agents have a common vector tick--the sheep tick Ixodes ricinus. LB and TBE are mandatory reportable diseases. In 2005 case definitions were implemented in Poland to allow a better comparability of data within the country and with other European countries. LB is widespread in Poland. Studies of prevalence of infected ticks indicate that from 6 to 15% of I. ricinus ticks in different sites are infected with the spirochete. Data from seroepidemiologic studies and from routine surveillance (started in 1996) confirm that the disease is widespread in Poland, and its incidence is increasing. It has increased from 2.31 per 100,000 in 1999 to 11.55 in 2005. One reason of this increase is the improvement in diagnosis of the disease. There is a need to promote personal protection during outdoor activities and knowledge on LB symptoms, especially among populations at risk--forestry workers, farmers. TBE incidence is limited to two main foci--one in the Northeast of Poland bordering Baltic states endemic region, and the second on the South of Poland, neighbouring the Czech and Slovak republics. Seroepidemiologic data, supported by surveillance data, indicate that there are areas of particularly high TBEV activity. The mostly affected occupational groups are: unemployed, retired, students, and farmers. This is a reason to promote personal protection and prophylactic vaccination of both inhabitants of endemic regions and tourists visiting endemic regions.

Adolescent↗
PubMed1989

[Ixodid ticks and rickettsia].

Ixodid ticks are an important link in the ecology of rickettsiae. Some tick species became specific vectors as well as reservoirs of certain species of rickettsiae ensuring their long lasting maintenance via interstadial and transovarial transmission often over generations in nature. To now many significant questions on relationship between ticks and rickettsiae became clear, however, most of them still remain to be elucidated. The open question, for instance, involves the data on the differences in sensitivity of various tick species to a certain species of rickettsiae what has its significance concerning the transmission of an agent to a host. Intracoelomal injection of a tick with rickettsiae does not solve its role as a vector in nature, because the main natural barrier of tick organism against pathogens, i.e. alimentary tract with its specific biochemical properties, has been avoided. To specify a tick as a vector of rickettsiae, data on their maintenance in various developmental stages of the arthropod as well as transmission to a host through feeding the blood are desirable. More attention should be focused to investigation on antibacterial (antirickettsial) effect of lysosyme, interferon and cellular elements in arthropods. Certainly mixed infections in ticks and namely their interactions, as well as the significance of rickettsia-like organisms in these arthropods, require also further investigations. Sufficient conclusive evidence concerning the effect of vector's organism on the biological properties of rickettsiae or in reverse, are almost unavailable. Investigations on above problems require the involvement of the modernest methods of immunology, immunochemistry, biochemistry and morphology.

Animals↗
PubMed1987

The control of heartwater by means of tick control.

Two main methods are currently being used by farmers in the heartwater regions to control this disease in cattle and other stock, namely strategic control of ticks and total control of ticks. Some farmers make successful use of the latter method, particularly in areas which are marginal for the disease. Total tick control requires top managerial skills, which includes continual expert supervision, a relatively rare asset. The majority of farmers, often unintentionally, apply strategic control of ticks to control heartwater, either without or with vaccination against the disease. In this case the objective of tick control is to minimize "tick worry" without interfering too drastically with natural transmission of the disease. This method would make provision for natural immunization of young animals (a more uncertain method than vaccination) and the maintenance of immunity. In practice these methods appear to diminish deaths from heartwater appreciably, but do not protect all animals from the disease. Furthermore, they appear to be more effective in cattle than other stock. Although strategic control has an evolutionary background and considerable merit under African conditions, it is being applied in an empirical way because of paucity of information on the epidemiology of heartwater. More information on the infection rate in and infectivity of ticks (percentage of infected ticks) offer challenging research possibilities.

Animals↗
PubMed1987

Parasites of domestic and wild animals in South Africa. XXII. Ixodid ticks on domestic dogs and on wild carnivores.

Ixodid ticks were collected from 4 dogs on smallholdings near Grahamstown, eastern Cape Province, on 1 or more occasions each week for periods ranging from 9-36 months. Fourteen tick species were recovered and the seasonal abundance of adult Haemaphysalis leachi and adult Rhipicephalus simus was determined. Complete collections of ticks were made from 50 caracals (Felis caracal) in the Cradock, Graaff-Reinet and Southwell regions in the eastern Cape Province. The animals from Cradock and Graaff-Reinet harboured 13 ixodid tick species. The caracals from Southwell were infested with 11 tick species and the seasonal abundance of Ixodes pilosus on these animals was determined. A small-spotted genet (Genetta genetta), 1 bat-eared fox (Otocyon megalotis), 1 aardwolf (Proteles cristatus) and 6 black-backed jackal (Canis mesomelas) from various localities in the eastern Cape Province were examined for ticks and 9 species were collected. Complete tick collections were made from a side-striped jackal (Canis adustus), 2 wild dogs (Lycaon pictus), a spotted hyaena (Crocuta crocuta), a several (Felis serval), 2 African civets (Civettictis civetta), 2 leopards (Panthera pardus) and a lion (Panthera leo) in the Kruger National Park in the north-eastern Transvaal. Twelve ixodid tick specis were recovered from these animals.

Animals↗
PubMed1986

Isolate of Anaplasma marginale not transmitted by ticks.

The tick-borne transmissibility of 2 isolates of Anaplasma marginale was compared. Dermacentor variabilis were exposed to A marginale as nymphs by feeding on 1 of 4 splenectomized calves during periods of ascending parasitemia (maximum 49% to 81% parasitized erythrocytes) induced by injection of a stabilate. Tick-borne transmission was attempted, using 26 to 224 adult ticks within 30 to 220 days after molting. Adult D variabilis did not transmit an Illinois isolate of A marginale in 7 tick-borne transmission experiments (P = 0.0047), including 2 experiments in which calves were inoculated IV with homogenates of adult ticks. In contrast, a Virginia isolate of A marginale was readily transmitted by the same tick colony. Thus, previously reported morphologic and immunologic differences among A marginale isolates may extend to tick-borne transmissibility. The Virginia and Illinois A marginale isolates had an inclusion appendage that was not a marker for tick transmissibility.

Anaplasmosis↗
PubMed1995

In vitro production of interleukin-4 and interferon-gamma by lymph node cells from BALB/c mice infested with nymphal Ixodes ricinus ticks.

In this study we compared the ability of lymphocytes taken from axillary and brachial lymph nodes of BALB/c mice that had been infested once three times with 15 nymphal Ixodes ricinus ticks, to produce interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) after in vitro stimulation with concanavalin A (Con A). They released high levels of IL-4 and low levels of IFN-gamma. An increase of IFN-gamma between the first and the third tick infestation was observed. Salivary gland extracts from female I. ricinus ticks induced specific in vitro proliferation of lymphocytes from infested mice. IL-4 production was correlated with the salivary gland extracts' ability to stimulate tick-specific lymphocyte proliferation. Its levels remained high from the first to the third infestation. IFN-gamma production was not necessarily associated with tick salivary gland antigen stimulation. In BALB/c mice, anti-tick immune response induction is regional and the contribution of other similar secondary lymphoid organs is negligible. Only cells from the lymph nodes which drained the tick-fixation site proliferated in vitro in the presence of tick antigens, and when stimulated with Con A produced IL-4 and IFN-gamma.

Animals↗
PubMed1997

[TIBOLA--a new tick-borne infection].

Twenty-seven cases of a tick-transmitted infection with similar symptoms were seen by the author in the last 14 months. These symptoms do not fit into the known tick-borne infections. The bite caused by a "strikingly big" engorged tick was almost uniformly located on the occipital scalp region. The infection occurred most commonly in young children: the larger half of the patients were less than 10 years of age. The main symptom, presented in all patients, was the enlargement of painful lymph nodes in the region of the tick bite, causing us to name the infection Tick-BOrne LymphAdenopathy ("TIBOLA"). The other major feature, presented more than a half of the cases, was a herpes-like eschar 0.5-3 cm in diameter at the site of the tick bite. The eruption could be surrounded by a circular erythema (6 cases). After healing of the eruption, alopecia remained at the site. The time from the bite to the first symptom varied between 1-30 (mean 8) days. Doxycyclin seemed to shorten the disease. The infection seemed benign since only 4 patients had high fever, while 3 patients had a low grade fever (37-38 degrees C). General symptoms lasted for 3-12 months. Contrary to Lyme borreliosis, which is highly distributed all over in Hungary, the new tick-transmitted infection seems geographically more restricted, with almost all of the patient reporting that the tick bite occurred in a 120 km wide and 200 km long region along the banks of the Danube. Most probably, the disease is caused by a rickettsia infection which is still needed to be proven.

Humans↗