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PubMed2026

Detection and phylogenetic characterization of Jingmen tick virus in Amblyomma mixtum ticks from Costa Rica.

UNLABELLED: Jingmenviruses are a group of segmented flaviviruses detected in arthropods and vertebrates that have attracted growing public health interest due to the recognition of some members as emerging human arboviral pathogens. As part of a study aimed at deciphering the virome of ticks of medical and veterinary importance in Costa Rica, we detected Jingmen tick virus (JMTV) in host-feeding Amblyomma mixtum ticks collected from horses. We assembled three complete genome segments and one partial segment from tick pools. Phylogenetic analyses revealed that JMTV from Costa Rica (JMTV Costa Rica) shares a common viral ancestor with JMTV viruses identified in ticks from the Caribbean and Latin America. Two distinct clades of Jingmenviruses were identified in the American continent, suggesting two distinct introductions: one from Europe/Asia and the other from Africa/Asia. Of note, JMTV Costa Rica falls in the same clade as viruses from Europe and Western Asia, including sequences found in humans. Our study constitutes the first detection of JMTV in Amblyomma mixtum. This tick species feeds on a wide range of hosts, including wildlife, domestic animals, and frequently parasitizes humans in Central America. Further research involving the detection of active and past infections by JMTV in humans and horses after tick bites is needed to evaluate the risk of spillover in Central America, including Costa Rica. IMPORTANCE: Jingmenviruses are flaviviruses detected in arthropods and vertebrates, reported in several countries worldwide. Some members cause disease and infections in humans; therefore, they are considered emergent human arboviruses. In Costa Rica and Central America, there is no information on tick-associated viruses or the role of ticks as putative vectors of viruses. Here, we report the first regional detection of Jingmen tick virus (JMTV) in Amblyomma mixtum ticks collected from horses. We assembled three complete and one partial viral segment from tick pools. Phylogenetic analysis revealed that the JMTV detected in Costa Rica is closely related to other detections from Latin America and the Caribbean and is located in the same clade as viruses reported in humans. Additionally, we detected two separate introductions of JMTV to Latin America. To determine whether this JMTV is an emergent arbovirus locally, research on past or active infections in humans is required.

Animals↗
PubMed2005

Migratory songbirds disperse ticks across Canada, and first isolation of the Lyme disease spirochete, Borrelia burgdorferi, from the avian tick, Ixodes auritulus.

During a 3-yr comprehensive study, 196 ixodid ticks (9 species) were collected from 89 passerine birds (32 species) from 25 localities across Canada to determine the distribution of avian-associated tick species and endogenous Lyme disease spirochetes, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt, and Brenner. We report the following first records of tick parasitism on avian hosts: the rabbit-associated tick, Ixodes dentatus Marx, from Manitoba and Ontario; the mouse tick, Ixodes muris Bishopp and Smith, from British Columbia; and the blacklegged tick, Ixodes scapularis Say, from New Brunswick. Moreover, we provide the first record of the Neotropical tick, Amblyomma humerale Koch (1 nymph), in Canada and its parasitism of any bird. This tick was compared morphologically with nymphs of other Neotropical Amblyomma spp., and genetically, using a 344-bp fragment of the 12S rDNA sequence of 41 New World Amblyomma species. The first collections of the western blacklegged tick, Ixodes pacificus Cooley and Kohls, from passerine species in Alberta and British Columbia, are also reported. Notably, we further report the first isolation of B. burgdorferi from the bird tick, Ixodes auritulus Neumann, collected from an American robin, Turdus migratorius L., on Vancouver Island. Furthermore, B. burgdorferi-positive I. auritulus larvae were collected from a reservoir-competent fox sparrow, Passerella iliaca (Merrem). Our findings indicate that ground-dwelling passerines, in particular, are parasitized by certain ixodid ticks and play an important role across Canada in the wide dispersal of B. burgdorferi-infected ticks and increased risk of Lyme disease exposure.

Animals↗
PubMed1997

Tick-borne encephalitis virus transmission between ticks cofeeding on specific immune natural rodent hosts.

To determine whether the portion of a vertebrate host population having specific immunity to tick-borne encephalitis (TBE) virus can participate in the TBE virus transmission cycle, natural hosts immunized against TBE virus were challenged with infected and uninfected ticks. Yellow-necked field mice (Apodemus flavicollis) and bank voles (Clethrionomys glareolus) were either immunized with TBE virus by subcutaneous inoculation of the virus, or they were exposed to virus-infected Ixodes ricinus ticks. One month later, when serum neutralizing antibody was detectable, the animals were infested with infected (donor) adult female ticks and uninfected (recipient) nymphal ticks; recipients were allowed to feed either in close contact (chamber 1) or physically separated (chamber 2) from the infected donor ticks. Following challenge with infected (and uninfected) ticks, viremia developed in all the control, nonimmune animals, whereas viremia was undetectable in all those animals naturally immunized by previous exposure to infected ticks. Despite the presence of neutralizing antibodies in all the immunized animals, 89% (24/ 27) immune animals supported virus transmission between infected and uninfected cofeeding ticks. Most transmission was localized, occurring within chamber 1; disseminated transmission from chamber 1 to chamber 2 was reduced. Immunization by tick bite was more effective than immunization by syringe inoculation in blocking cofeeding virus transmission. Nevertheless 76% (9/12) animals with "natural" immunity still supported transmission. The results demonstrate that natural hosts having neutralizing antibodies to TBE virus (and no detectable viremia) can still support virus transmission between infected and uninfected ticks feeding closely together on the same animal. These observations have important epidemiological implications relating to the survival of TBE virus in Nature.

Animals↗
PubMed2006

A comparison of Chryseobacterium indologenes pathogenicity to the soft tick Ornithodoros moubata and hard tick Ixodes ricinus.

A yellow-pigmented Gram-negative bacterium, Chryseobacterium indologenes, was found in the gut contents of about 65% of soft ticks Ornithodoros moubata from a perishing laboratory colony. The isolated putative pathogen, C. indologenes, was susceptible to cotrimoxazol and addition of this antibiotic (Biseptol 480) to the blood meal significantly decreased the tick mortality rate. The artificial infection of healthy O. moubata by membrane feeding on blood contaminated with C. indologenes was lethal to all ticks at concentrations 10(6) bacteria/ml. On the contrary, a similar infection dose applied to the hard tick Ixodes ricinus by capillary feeding did not cause significant mortality. Examination of guts dissected from infected O. moubata and I. ricinus revealed that C. indologenes was exponentially multiplied in the soft tick but were completely cleared from the gut of the hard ticks within 1 day. In both tick species, C. indologenes were found to penetrate from the gut into the hemocoel. The phagocytic activity of hemocytes from both tick species was tested by intrahaemocoelic microinjection of C. indologenes and evaluated by indirect fluorescent microscopy using antibodies raised against whole bacteria. Hemocytes from both tick species displayed significant phagocytic activity against C. indologenes. All O. moubata injected with C. indologenes died within 3 days, whereas the increase of the mortality rate of I. ricinus was insignificant. Our results indicate that hard ticks possess much more efficient defense system against infection with C. indologenes than the soft ticks. Thus, C. indologenes infection has the potential to be a relevant comparative model for the study of tick immune reactions to transmitted pathogens.

Animals↗
PubMedDate not supplied

[The isolation of Borrelia from the tick Ixodes trianguliceps (Ixodidae) and the possible significance of this species in the epizootiology of ixodid tick-borne borrelioses].

Ixodes trianguliceps is a common tick species of the Eurasian forest zone. These ticks live probably in natural foci of ixodid tick-borne borrelioses (ITBB) from Western Europe to Transbaikalia, but their role in circulation of corresponding pathogens remains unclear. This study was performed in a natural ITBB focus located in the Perm region of Russia (near the Urals), where Borrelia garinii and B. afzelii circulate and I. persulcatus serves as their main vector. In July-August of 1994, 296 small mammals (mostly Clethrionomys glareolus) were tested for tick infestation. From these mammals, 49 I. trianguliceps and 252 I. persulcatus ticks were collected (16.3 and 83.7%, respectively). I. trianguliceps ticks were found on 33 rodents of three species: Cl. glareolus, Cl. rutilus, and Microtus oeconomus. The abundance of I. trianguliceps (on average, less than 0.2 ticks per animal) was approximately five times lower than that of I. persulcatus. I. trianguliceps larvae, nymphs, and adults (22, 15, and 5 specimens, respectively) were analyzed for Borrelia infection by plating their internal organs on the BSK-2 medium. Spirochete isolates were obtained from four nymphs. Three infected nymphs were collected from different Cl. glareolus specimens, and one was found on Cl. rutilus. According to the results of RFLP analysis, all four isolates were classified as B. garinii. This experiment is the first successful attempt to isolate one of ITBB pathogens from I. trianguliceps ticks. These ticks do not attack people, and their role in ITBB foci should be analyzed only in terms of epizootiology. The results of previous zoological-parasitological and bacteriological studies performed in the Ural region suggest that I. trianguliceps and I. persulcatus populations are maintained there by the same species of small rodents and insectivores, which mostly belong to the genera. Clethrionomys and Sorex. Many of them were identified as the reservoir hosts of Borrelia. These data, in complex with the fact of B. garinii isolation from I. trianguliceps, suggest that I. trianguliceps ticks are involved in the maintenance of Borrelia circulation in natural ITBB foci. Taking into account the low abundance of these ticks in the Ural forests, they should be regarded as an important but not principal component of the epizootic process. It is suggested that such a conclusion about the significance of I. trianguliceps ticks also pertains to ITBB foci of other regions.

Animals↗
PubMed2003

Thresholds for disease persistence in models for tick-borne infections including non-viraemic transmission, extended feeding and tick aggregation.

Lyme disease and Tick-Borne Encephalitis (TBE) are two emergent tick-borne diseases transmitted by the widely distributed European tick Ixodes ricinus. The life cycle of the vector and the number of hosts involved requires the development of complex models which consider different routes of pathogen transmission including those occurring between ticks that co-feed on the same host. Hence, we consider here a general model for tick-borne infections. We assumed ticks feed on two types of host species, one competent for viraemic transmission of infection, the second incompetent but included a third transmission route through non-viraemic transmission between ticks co-feeding on the same host. Since a blood meal lasts for several days these routes could lead to interesting nonlinearities in transmission rates, which may have important effects.We derive an explicit formula for the threshold for disease persistence in the case of viraemic transmission, also for the case of viraemic and non-viraemic transmission. From this formula, the effect of parameters on the persistence of infection can be determined. When only viraemic transmission occurs, we confirm that, while the density of the competent host has always a positive effect on infection persistence, the density of the incompetent host may have either a positive effect, by amplifying tick population, or a negative ("dilution") effect, by wasting tick bites on an incompetent host. With non-viraemic transmission, the "dilution" effect becomes less relevant. On the other hand, if the nonlinearity due to extended feeding is included, the dilution effect always occurs, but often at unrealistically high host densities. Finally, we incorporated the effects of tick aggregation on the hosts and correlation of tick stages and found that both had an important effect on infection persistence, if non-viraemic transmission occurred.

Animals↗
PubMed1984

Characterization of tick antigens inducing host immune resistance. I. Immunization of guinea pigs with Amblyomma americanum-derived salivary gland extracts and identification of an important salivary gland protein antigen with guinea pig anti-tick antibodies.

Guinea pigs immunized by subcutaneous injection of an emulsion of incomplete Freund's adjuvant (IFA) containing tick salivary gland extract antigens (SGA) from partially fed female ticks expressed a significant level of tick rejection when challenged 17 days later. This level of tick rejection was similar to animals actively sensitized by tick feeding and challenged at the same time. SGA emulsified with complete Freund's adjuvant (CFA) or administered with saline was ineffective. However, ticks that fed on animals immunized with SGA+IFA or SGA+CFA expressed significant reductions in engorgement weight. SGA was active when prepared with or without protease inhibitors. The minimum effective immunizing dose of SGA was between 100 and 280 micrograms per animal. Extracts made from salivary gland-derived cement material (CA) from partially fed female ticks administered at 50 micrograms in IFA induced levels of tick rejection comparable to animals immunized with 280 micrograms of SGA+IFA. Sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS/PAGE) of 35S- and 125I-radiolabeled SGA and CA extracts immunoprecipitated by guinea pig anti-tick serum that transferred immune resistance demonstrated a unique protein of 20,000 m.w. Serum from animals immunized with SGA+IFA (successful immunization) recognized this same protein, whereas serum from animals immunized with SGA+CFA (unsuccessful immunization) did not. The results of this study suggest that a 20,000 m.w. protein derived from the tick salivary gland may be responsible for the induction and perhaps elicitation of host immune resistance responses to Amblyomma americanum ticks.

Animals↗
PubMed2000

Ticks and tick-borne disease systems in space and from space.

Analyses within geographical information systems (GISs) indicate that small- and large-scale ranges of hard tick species (Ixodidae) are determined more by climate and vegetation than by host-related factors. Spatial distributions of ticks may therefore be analysed by statistical methods that seek correlations between known tick presence/absence and ground- or remotely-sensed (RS) environmental factors. In this way, local habitats of Amblyomma variegatum in the Caribbean and Ixodes ricinus in Europe have been mapped using Landsat RS imagery, while regional and continental distributions of African and temperate tick species have been predicted using multi-temporal information from the National Oceanic and Atmospheric Administration-Advanced Very High Resolution Radiometer (NOAA-AVHRR) imagery. These studies illustrate ways of maximizing statistical accuracy, whose interpretation is then discussed in a biological framework. Methods such as discriminant analysis are biologically transparent and interpretable, while others, such as logistic regression and tree-based classifications, are less so. Furthermore, the most consistently significant variable for predicting tick distributions, the RS Normalized Difference Vegetation Index (NDVI), has a sound biological basis in that it is related to moisture availability to free-living ticks and correlated with tick mortality rates. The development of biological process-based models for predicting the spatial dynamics of ticks is a top priority, especially as the risk of tick-borne infections is commonly related not simply to the vector's density, but to its seasonal population dynamics. Nevertheless, using statistical pattern-matching, the combination of RS temperature indices and NDVI successfully predicts certain temporal features essential for the transmission of tick-borne encephalitis virus, which translate into a spatial pattern of disease foci on a continental scale.

Animals↗
PubMed1994

Experimental transmission of Langat (tick-borne encephalitis virus complex) virus by the soft tick Ornithodoros sonrai (Acari: Argasidae).

Laboratory studies determined that the soft tick Ornithodoros sonrai Sautet & Witkowski is a competent vector of Langat (tick-borne encephalitis virus complex) virus. When ticks fed on suckling mice having a mean viremia of 10(7.2) plaque-forming units per ml, 52% (n = 208) became infected, and 84% (n = 87) of the infected ticks transmitted virus by bite when fed individually on suckling mice > or = 27 d after the infectious blood meal. Overall, 79 of 184 (43%) of ticks exposed to the original viremic mice individually transmitted virus by bite when tested up to 351 d after the infectious blood meal. In addition, ticks transmitted virus both transstadially and transovarially. Some ticks that transmitted virus during their first transmission attempt were retested. These ticks transmitted virus during 81 (99%) of 82 refeeding attempts, including ticks that transmitted virus 512 d after the initial infectious meal. Therefore, Ornithodoros spp. should be considered as potential vectors of Langat and other tick-borne encephalitis viruses.

Animals↗
PubMed2006

Determining the tick scutal index allows assessment of tick feeding duration and estimation of infection risk with Borrelia burgdorferi sensu lato in a person bitten by an Ixodes ricinus nymph.

The risk of Borrelia burgdorferi sensu lato transmission from an infected vector tick to a host increases with increasing duration of tick feeding. In Ixodes ricinus nymphs, the main vector of B. burgdorferi s.l. in most parts of Europe, the transmission risk appears low to moderate within the first 24h of feeding but increases to >70% after only 36 h. In this study, the so-called scutal index, the ratio between tick abdominal length and scutum width, a very good measure of the level of tick engorgement, was investigated for its potential to assess the feeding duration of detached I. ricinus nymphs, thereby indicating the level of human infection risk with B. burgdorferi s.l. I. ricinus nymphs were allowed to feed in capsules on tick-naive Mongolian gerbils for 0, 12, 24, 36 h, or to repletion, in groups of up to 9 individuals. After tick removal, the scutal index of each tick (n=516) was determined using a stereomicroscope with an ocular micrometer. This was also possible, if the tick mouthparts were damaged. Although the scutal indices determined at 24 h versus 36 h post-attachment (a critical interval for B. burgdorferi transmission) differ significantly, there was some overlap between the two groups. However, by choosing a scutal index of 1.1 as a cut-off, it was possible to assign 93.2% of the ticks attached for 24h (n=310) to one group (low-risk group ticks) and 85.6% of those attached for 36 h (n=97) to the other (high-risk group ticks). This means that those people from whom I. ricinus nymphs with a scutal index >1.1 detached have a distinctly elevated risk of Borrelia infection and therefore more likely require medical attention.

Animals↗
PubMed2000

Swiss Army Survey in Switzerland to determine the prevalence of Francisella tularensis, members of the Ehrlichia phagocytophila genogroup, Borrelia burgdorferi sensu lato, and tick-borne encephalitis virus in ticks.

A total of 6071 Ixodes ricinus ticks were collected on Swiss Army training grounds in five regions of Switzerland. The aim of the survey was to assess the prevalence of ticks infected with the human pathogens Francisella tularensis, members of the Ehrlichia phagocytophila genogroup, Borrelia burgdorferi sensu lato, and the European tick-borne encephalitis virus. TaqMan PCR (PE Biosystems, USA) and TaqMan RT-PCR (PE Biosystems) analyses were performed on DNA and RNA extracted from pools of ten ticks grouped by gender. Here, for the first time, it is shown that ticks may harbor Francisella tularensis in Switzerland, at a rate of 0.12%. Furthermore, 26.54% of the ticks investigated harbored Borrelia burgdorferi sensu lato, 1.18% harbored members of the Ehrlichia phagocytophila genogroup, and 0.32% harbored the European tick-borne encephalitis virus. A new instrumentation was applied in this study to carry out and analyze more than 2300 PCR reactions in only 5 days. Furthermore, the results reveal that people working in outdoor areas, including army personnel on certain training grounds contaminated with ticks containing tick-borne pathogens, are at risk for different tick-borne diseases.

Animals↗
PubMed2004

Pheromones and other semiochemicals of ticks and their use in tick control.

This review addresses the role of compounds secreted into the external environment that mediate important aspects of tick behaviour. Known as semiochemicals, these information-containing compounds include pheromones (used for conspecific communication), allomones (defence secretions) and kairomones (used for host identification and location). An impressive body of knowledge has accumulated concerning the identification of the compounds that comprise these semiochemicals. Pheromones are the best known and intensively studied, including arrestment (=assembly) pheromones, attraction-aggregation-attachment (AAA) pheromones and sex pheromones. Arrestment behaviour is mediated by contact with excreta from other ticks. In contrast, aggregating and sexual behaviours comprise a hierarchy of responses to different types of chemical compounds that must be recognized in a sequential order to achieve the end result. Ixodid ticks also produce an allomone that protects against certain insect predators. Finally, ticks use kairomones for host identification, e.g. volatiles such as CO2 and NH3 and various oils such as glandular secretions from deer. Knowledge of tick pheromones has been used to develop innovative new technologies for tick control. These products incorporate tick pheromones and small amounts of pesticide to attract and kill ticks on their hosts or in vegetation. The kairomones and the tick allomone also may be of interest for use in controlling ticks.

Animals↗
PubMed2004

Tick ecology: processes and patterns behind the epidemiological risk posed by ixodid ticks as vectors.

The population ecology of ticks is fundamental to the spatial and temporal variation in the risk of infection by tick-borne pathogens. Tick population dynamics can only be fully understood by quantifying the rates of the demographic processes, which are influenced by both abiotic (climatic) factors acting on the free-living tick stages and biotic (host) responses to the tick as a parasite. Within the framework of a population model, I review methods and results of attempts to quantify (1) rates of tick development and the probability of diapause, (2) the probability of questing for hosts by unfed ticks, (3) the probability of ticks attaching to a host, and (4) tick mortality rates. Biologically, these processes involve the physiological and behavioural response of ticks to temperature, moisture stress and day length that result in specific patterns of seasonal population dynamics and host relationships. Temperate and tropical patterns will be illustrated with reference mostly to Ixodes ricinus and Rhipicephalus appendiculatus, respectively.

Adaptation, Physiological↗
PubMed2002

Tick-borne encephalitis virus prevalence in Ixodes ricinus ticks collected in high risk habitats of the south-Bohemian region of the Czech Republic.

A survey for tick-borne encephalitis virus in trades ricinus ticks was conducted in May 2000 in two districts of the South-Bohemian region of the Czech Republic with a high occurrence of tick-borne encephalitis (TBE) in humans. Homogenized ticks were tested on PS cells, which were examined for any cytopathic effect, plaque assay and indirect fluorescent antibody test (IFT). The IFT has proved to be the most sensitive and most rapid test to demonstrate the virus in ticks. TBE virus was found in 17 of 187 pooled samples. consisting of a total of 2,968 ticks. The mean minimum infection rate was 0.6% for all tick stages combined. Infection rates in nymphs collected in different locations varied between 0.2 and 1.3% and between 5.9 and 11.1% in adult ticks. The observed TBE prevalence in ticks was compared with data obtained elsewhere in the Czech Republic. It is concluded that screening of ticks for TBE virus prevalence using IFT is a valuable indicator for the degree of risk to contract TBE in as particular habitat.

Animals↗
PubMed2001

Prevalence of infection in ticks submitted to the human tick test kit program of the U.S. Army Center for Health Promotion and Preventive Medicine.

In 1997, ticks removed from humans and received alive by the Tick-Borne Disease Laboratory of the U.S. Army Center for Health Promotion and Preventive Medicine (USACHPPM) were tested for pathogens by polymerase chain reaction (PCR). Thirty-three of 222 (15%) Amblyomma americanum (L.) DNAs produced amplicons of the expected size of Ehrlichia chaffeensis Anderson, Dawson & Wilson and 26/222 (12%) produced amplicons indicating Borrelia burgdorferi Johnson, Schmid, Hyde, Steigalt & Brenner. Five (2%) appeared to be co-infected with both organisms. Thirteen of 308 (4%) Dermacentor variabilis (Say) were PCR-positive for spotted fever group rickettsiae. Restriction fragment-length polymorphism analysis indicated all were Rickettsia montana. One hundred twenty-seven D. variabilis from Monroe County, WI, were tested for B. burgdorferi and 14 (11%) were positive. Five of 24 (21%) Ixodes scapularis Say were positive for B. burgdorferi and one (2%) was positive for the agent of human granulocytic ehrlichiosis. Different species of ticks transmit different pathogens, and most tick-borne diseases have similar early symptoms, therefore knowing the species and infection status of the tick enhances the physician's ability to consider tick-borne agents as a potential cause of disease and recommend appropriate therapy. Ongoing surveillance of the vector species of human diseases provides an additional estimate of human encounters with infected ticks, and testing ticks removed from humans may increase our knowledge of the vector status of tick species for transmitting tick-borne pathogens.

Animals↗
PubMed1990

The impact of natural infestations of ticks in Zambia on the productivity of cattle and implications for tick control strategies in central Africa.

Studies were carried out in Zambia using a farming systems approach to quantify the effects of tick control on traditionally managed Sanga cattle. In the first trial to investigate the effect of tick control, significant improvements in liveweight gain (LWG) occurred only in periods of medium to high challenge with adult Amblyomma variegatum. However, during the first 18 months of the study when animals were young, the acaricide used caused a suppression in weight gains. A supplementary experimental study indicated that the adverse effects of ticks on weight gain may be delayed when animals are on a low plane of nutrition. In both studies on the effects of ticks on LWG, estimates of weight loss per female A. variegatum were in the range of 46 to 69 g. In the second long term trial to measure the impact of tick control on overall heard productivity, outputs of milk and weaner calf per livestock unit carrying capacity were about 25% higher in a tick-free herd. The annual cost of control in 1988 at ZK286.26/livestock unit was greater than the increase in value of the products at ZK175.48/livestock unit carrying capacity. It is concluded from these studies that intensive tick control in the multipurpose livestock system in Zambia is not justified in the absence of serious tick-borne disease. However, strategic seasonal tick control of adult ticks from November to April would probably be economically viable. Calves should not be treated until they are 3 months of age.

Africa, Central↗
PubMed2004

[Tick-borne human pathogenic microorganisms found in Europe and those considered nonpathogenic. Part I: Ticks and Viruses].

The importance of tick-borne encephalitis (TBE) and Lyme borreliosis-the main European tick-borne diseases-is steadily growing. This fact is due to many different factors including climate changes. However, across Europe many other human pathogenic viruses, bacteria, and parasites are found in ticks. This article gives an overview of tick-borne human pathogenic viruses present in Europe as well as those considered nonpathogenic. It also deals with the various species of vector-competent ticks. Among these ticks, viruses from 6 families encompassing 8 genera and 35 species are found,whereby the families Flaviviridae, Bunyaviridae, and Reoviridae with the genera flavivirus, nairovirus, and orbivirus are the most prevalent. Because of their special importance Omsk hemorrhagic fever, louping-ill disease, tick-borne encephalitis, and Crimean-Congo hemorrhagic fever are discussed in detail. Although West Nile virus is mainly transmitted to man by mosquitoes, it is discussed in detail, because West Nile fever has become a good example for a new and rapidly spreading vector-borne disease in the USA and for a recurrent one in Europe. Secondly, besides the mosquito-bird cycle an interesting tick--bird cycle is emerging. The overview clearly demonstrates that in Europe (particularly in Germany) tick-borne viruses, with the exception of TBE, constitute an extremely ignored research subject. This lack of attention is in contrast to their importance and results in a lack of necessary scientific data.

Adrenal Cortex Hormones↗
PubMed1998

Phospholipase A2 activity in salivary glands and saliva of the lone star tick (Acari: Ixodidae) during tick feeding.

Phospholipase A2 (PLA2) activity levels in tick [Amblyomma americanum (L.)] salivary glands and saliva were examined during tick feeding by using 14C-phosphatidylcholine as the substrate. Saliva produced by stimulating female ticks to salivate with dopamine contains PLA2 (ts-PLA2) activity. The ts-PLA2 activity level in saliva did not change significantly during tick feeding except for a decrease in the last rapid feeding phase (> 200 mg) and in replete ticks. Phospholipase A2 activity was higher in salivary glands of fed than unfed ticks, both in males and females; activity increased during tick feeding correlating with salivary secretory rates during tick feeding suggesting that much of the PLA2 activity measured in whole salivary glands is synthesized for subsequent secretion. During the time course of in vitro salivation, the first 10 microliters of saliva contained higher ts-PLA2 activity than saliva secreted thereafter. Phospolipase A2 was identified in the saliva of artificially fed ticks indicating that ts-PLA2 is a physiological component of tick saliva.

Animals↗