Showing papers on "Tick published in 2006"
TL;DR: Crimean-Congo haemorrhagic fever (CCHF) is an often fatal viral infection described in about 30 countries, and it has the most extensive geographic distribution of the medically important tickborne viral diseases, closely approximating the known global distribution of Hyalomma spp ticks.
Abstract: Crimean-Congo haemorrhagic fever (CCHF) is an often fatal viral infection described in about 30 countries, and it has the most extensive geographic distribution of the medically important tickborne viral diseases, closely approximating the known global distribution of Hyalomma spp ticks. Human beings become infected through tick bites, by crushing infected ticks, after contact with a patient with CCHF during the acute phase of infection, or by contact with blood or tissues from viraemic livestock. Clinical features commonly show a dramatic progression characterised by haemorrhage, myalgia, and fever. The levels of liver enzymes, creatinine phosphokinase, and lactate dehydrogenase are raised, and bleeding markers are prolonged. Infection of the endothelium has a major pathogenic role. Besides direct infection of the endothelium, indirect damage by viral factors or virus-mediated host-derived soluble factors that cause endothelial activations and dysfunction are thought to occur. In diagnosis, enzyme-linked immunoassay and real-time reverse transcriptase PCR are used. Early diagnosis is critical for patient therapy and prevention of potential nosocomial infections. Supportive therapy is the most essential part of case management. Recent studies suggest that ribavirin is effective against CCHF, although definitive studies are not available. Health-care workers have a serious risk of infection, particularly during care of patients with haemorrhages from the nose, mouth, gums, vagina, and injection sites. Simple barrier precautions have been reported to be effective.
982 citations
TL;DR: Over 8000 expressed sequence tags from six different salivary gland cDNA libraries from the tick Ixodes scapularis support the hypothesis that gene duplication, most possibly including genome duplications, is a major player in tick evolution.
355 citations
01 Jan 2006
TL;DR: In this paper, the impacts of climate change and adaptation on Lyme borreliosis (LB) in Europe were reviewed and it was concluded that future climate change in Europe will facilitate a spread of LB into higher latitudes and altitudes, and contribute to increased disease occurrence in endemic areas.
Abstract: Stockholm University and WHO, within a project funded by the European Commission (EVK2-2000-00070), reviewed the impacts of climate change and adaptation on Lyme borreliosis (LB) in Europe. LB is the most common vector-borne disease in Europe. The highest incidence is reported from Austria, the Czech Republic, Germany, and Slovenia, as well as from the northern countries bordering the Baltic Sea. LB is a multi-system disorder that is treatable with antibiotics, but may lead to severe complications of the neurological system, the heart, and the joints. LB is caused by a spirochete (Borrelia burgdorferi s.l.), which is transmitted to humans by ticks, in Europe mainly the species Ixodes ricinus. Reservoir animals are small rodents, insectivores, hares and birds. Ticks may live for more than three years and are highly sensitive to changes in seasonal climate. Daily seasonal climatic conditions directly impact tick survival and activity. Indirectly, climate affects both tick and pathogen occurrence through effects on habitat conditions and reservoir animal density. In addition, climate-induced changes in land use and in recreational behaviour influence human exposure to infected ticks and thus disease prevalence. Since the 1980s, tick vectors have increased in density and spread into higher latitudes and altitudes in Europe. It can be concluded that future climate change in Europe will facilitate a spread of LB into higher latitudes and altitudes, and contribute to increased disease occurrence in endemic areas. In some locations, where climate conditions will become too hot and dry for tick survival, LB will disappear. There is a need to strengthen preventive measures such as information to the general public, surveillance activities within a pan-European network and to use standardized methods to provide data for future research activities.
277 citations
TL;DR: The medical and economic importance of ticks has long been recognized due to their ability to transmit diseases to humans and animals, which are of great economic importance world-wide.
Abstract: The medical and economic importance of ticks has long been recognized due to their ability to transmit diseases to humans and animals. Ticks cause great economic losses to livestock, and adversely affect livestock hosts in several ways. Loss of blood is a direct effect of ticks acting as potential vector for haemo-protozoa and helminth parasites. Blood sucking by large numbers of ticks causes reduction in live weight and anemia among domestic animals, while their bites also reduce the quality of hides. However, major losses caused by ticks are due to their ability to transmit protozoan, rickettsial and viral diseases of livestock, which are of great economic importance world-wide. There are quite a few methods for controlling ticks, but every method has certain shortcomings. The present review is focused on ticks importance and their control.
224 citations
TL;DR: Preliminary studies have suggested the possibility of vaccine strategies directed toward both tick control and the blocking of pathogen transmission, and development of vaccines against multiple tick species may be possible using highly conserved tick‐protectiveAntigens or by antigens showing immune cross‐reaction to different tick species.
Abstract: SUMMARY
Ticks are distributed worldwide and impact human and animal health, as well as food animal production. Control of ticks has been primarily by application of acaricides, which has resulted in selection of resistant ticks and environmental pollution. Vaccines have been shown to be a feasible tick control method that offers a cost-effective, environmentally friendly alternative to chemical control. However, identification of tick-protective antigens remains the limiting step in vaccine development. Tick antigens exposed naturally to the host during tick feeding and those concealed have both shown promise as candidate vaccine antigens. Development of vaccines against multiple tick species may be possible using highly conserved tick-protective antigens or by antigens showing immune cross-reaction to different tick species. Vaccines made from a combination of key protective antigens may greatly enhance vaccine efficacy. Preliminary studies have suggested the possibility of vaccine strategies directed toward both tick control and the blocking of pathogen transmission. Characterization of the tick genomes will have a great impact on the discovery of new protective antigens. The future of research directed toward tick vaccine development is exciting because of new and emerging technologies for gene discovery, and vaccine formulation and delivery.
210 citations
TL;DR: Rickettsial infection was evaluated in 669 Amblyomma aureolatum adult ticks collected from naturally infested dogs in Taiaçupeba, a BSF‐endemic area in the state of São Paulo, and results suggest that A. a Aureolatum is an important vector of R. rickettsii in Brazil.
Abstract: Brazilian spotted fever (BSF) is a highly lethal disease caused by Rickettsia rickettsii. In the present study, rickettsial infection was evaluated in 669 Amblyomma aureolatum adult ticks collected from naturally infested dogs in Taiacupeba, a BSF-endemic area in the state of Sao Paulo. Ten (1.49%) ticks were infected with Rickettsia bellii, and 6 (0.89%) ticks were infected with R. rickettsii. Both Rickettsia species were isolated and established in Vero cell cultures. The Rickettsia isolates were characterized by molecular analyses, sequencing fragments of different rickettsial genes. Our results suggest that A. aureolatum is an important vector of R. rickettsii in Brazil.
201 citations
TL;DR: The results of both studies show that D. reticulatus presently occurs at far more sites than previously known in Germany and thus most likely has expanded its range.
200 citations
TL;DR: Birds host vector ticks and Borrelia species and vary in effectiveness as reservoirs, and these species can be beneficial to humans and wildlife.
Abstract: To define the role of birds as reservoirs and disseminators of Borrelia spirochetes, we characterized tick infestation and reservoir competence of migratory passerine birds in Sweden. A total of 1,120 immature Ixodes ricinus ticks were removed from 13,260 birds and assayed by quantitative polymerase chain reaction (PCR) for Borrelia, followed by DNA sequencing for species and genotype identification. Distributions of ticks on birds were aggregated, presumably because of varying encounters with ticks along migratory routes. Lyme borreliosis spirochetes were detected in 160 (14%) ticks. Borrelia garinii was the most common species in PCR-positive samples and included genotypes associated with human infections. Infestation prevalence with infected ticks was 5 times greater among ground-foraging birds than other bird species, but the 2 groups were equally competent in transmitting Borrelia. Migratory passerine birds host epidemiologically important vector ticks and Borrelia species and vary in effectiveness as reservoirs on the basis of their feeding behavior.
189 citations
TL;DR: The first isolation of Rickettsia massiliae from a patient is reported, leading us to believe that this isolate may cause a Mediterranean spotted fever–like disease that was described in children in Spain.
Abstract: To the Editor: The number of new rickettsial species that cause diseases in humans is rapidly increasing (1). Moreover, many of the species first described in ticks have been recently shown to be pathogenic. Of the 10 species or subspecies found to be pathogens after 1984, a total of 7 were first isolated from ticks (2). We report the first isolation of Rickettsia massiliae from a patient. The bacterium was isolated in Sicily in 1985 and identified in 2005.
A 45-year-old man was hospitalized in Palermo, Italy, on June 6, 1985, for fever and a rash. He had been febrile since May 25 and did not respond to antimicrobial drug treatment using cefamezin, a first-generation cephalosporin. On examination, he had a necrotic eschar on his right ankle, a maculopapular rash on his palms and soles (Figure A1), and slight hepatomegaly. Leukocyte count was normal; he received tetracyclines for 13 days and fully recovered. He seroconverted (from 0 to 1:80 between day 11 and day 24) by indirect immunofluorescence to Rickettsia conorii (R. conorii spot, bioMerieux, Marcy l'Etoile, France).
Four milliliters of heparinized blood sampled before treatment were inoculated in a 25-cm2 flask containing Vero cells and incubated at 33°C in a CO2 incubator (1). Direct immunofluorescence test on a sample of the patient's serum was positive 7 days later. The strain was stored for 20 years and tested in 2005 at the Unite des Rickettsies for identification, and R. massiliae was identified. DNA was extracted from the cell culture supernatant and used as template in 2 previously described polymerase chain reaction (PCR) assays that targeted a portion of the rickettsial ompA gene as well as a portion of the rickettsial gltA gene (3,4). Amplification products of the expected size were obtained from this extract but from no concurrently processed control materials, including 3 negative controls. DNA sequencing of the positive PCR products gave 100% identity with R. massiliae for ompA (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"RBU43792","term_id":"1174112","term_text":"gb||RBU43792"}}RBU43792) and 99.9% homology for gltA (GenBank accession no. RSU 59720).
R. massiliae was first isolated from Rhipicephalus ticks in Marseilles (5). It is transmitted transovarially in Rhipicephalus turanicus (2). R. massiliae is commonly found in Rhipicephalus sanguineus or R. turanicus in France, Greece, Spain (identified as Bar 29) (6), Portugal, Switzerland, Sicily (D. Raoult, unpub. data), Central Africa, and Mali (2). R. massiliae may be commonly associated with these ticks, which are distributed worldwide.
R. massiliae is grouped phylogenically with Rickettsia rhipicephali and Rickettsia aeschlimannii (Figure A2). Bacteria from this group have a natural resistance to rifampin that is associated with an rpoB sequence that is different from that of other rickettsiae. This isolate was not tested for antimicrobial drug susceptibly (7). Rifampin resistance leads us to believe that this isolate may cause a Mediterranean spotted fever–like disease that was described in children in Spain (7,8). Serologic findings were recently reported that showed some patients in Barcelona, Spain, with reactions that indicate R. massiliae (B29 strain) rather than R. conorii (6). However, serologic reactions are only presumptive; isolation from a patient is the required to initially describe a new disease (9).
This Sicilian index case shows that R. massiliae is a human pathogen. It contraindicates using rifampin to treat Mediterranean spotted fever in areas where R. massiliae is endemic, as it cannot as yet be differentiated from R. conorii infection. R. massiliae is a new example of a strain identified in ticks for several years before its first isolation from a human patient (10). The longest delay was observed for Rickettsia parkeri, which was isolated from ticks in 1939 but not from a patient until 2004. Many authors labeled R. parkeri a nonpathogenic rickettsia during this time (1). In the present case, the human isolate was obtained before the tick isolate but was not further identified. When this strain was isolated, R. conorii was the sole Rickettsia sp. found in ticks in southern Europe. Moreover, only 1 tickborne pathogenic Rickettsia sp. was believed to circulate in a single area. Since that time, several tickborne rickettsial diseases have been shown to exist in the same area, which prompted us to retrospectively identify this strain. The patient was reexamined in May 2005, after this identification. He is healthy and has no remaining antibodies against Rickettsia spp.
187 citations
TL;DR: These are the first four cases of human parasitism by Rhipicephalus sanguineus (Latrielle) in Brazil and the possible implications of this finding are discussed here.
Abstract: The objective of this paper is to describe four cases of human parasitism by Rhipicephalus sanguineus (Latrielle) in Brazil. During an investigation regarding the species of ectoparasites of domestic dogs from the metropolitan region of Recife, Pernambuco state, four dog owners were found to be parasitized by ticks. The ticks were collected from these individuals and their dogs. All the ticks were identified as Rhipicephalus sanguineus . These are, to our knowledge, the first four cases of human parasitism by this tick species in Brazil. The possible implications of this finding are discussed here.
183 citations
TL;DR: The prevalence of infection of Ehrlichia chaffeensis, E. ewingii, “Borrelia lonestari,” and R. amblyommii within A. americanum ticks was determined and underscores the nonhomogeneous distribution of pathogen foci of infection.
Abstract: Ambyomma americanum (L.) (Acari: Ixodidae) is an aggressive tick that feeds on humans during all postembryonic life stages. In many regions of the United States, it is the tick most commonly found attached to humans. Public health interest has grown recently, due to the recognition of new human pathogens transmitted by A. americanum and the expanding distribution of the tick. A.americanum is a vector of several bacteria pathogenic to humans. Ehrlichia chaffeensis and Ehrlichia ewingii cause moderate-to-severe febrile illness. "Rickettsia amblyommii," a member of the spotted fever group Rickettsia, also has recently been implicated as a possible human pathogen based on serologic evidence from persons recovering from illness after a tick bite. We have determined the prevalence of infection of Ehrlichia chaffeensis, E. ewingii, "Borrelia lonestari," and R. amblyommii within A. americanum ticks from 29 sites in nine states. Overall infection prevalences were 4.7% for E. chaffeensis (range, 0 Ð27%), 3.5% for E. ewingii (range, 0 Ð18.6%), 2.5% for B. lonestari (range, 0 Ð12.2%), and 41.2% for R. amblyommii (range, 0 Ð 84.0%). In addition, 87 ticks (4.3%) were infected with two or more bacteria. This report documents new distribution records for E.ewingii,B.lonestari, and R. amblyommii and underscores the nonhomogeneous distribution of pathogen foci of infection. Additional surveillance throughout the range of A.americanum is warranted to increase physician and public awareness of the risk of disease to humans from exposure to the agents transmitted by this tick.
TL;DR: The new isolate, AZT80, does not elicit cytotoxic effects in Vero cells and causes a persistent infection in XTC-2 cells, and is susceptible to doxycycline but resistant to rifampin and erythromycin.
Abstract: Twenty Rhipicephalus sanguineus ticks collected in eastern Arizona were tested by PCR assay to establish their infection rate with spotted fever group rickettsiae. With a nested PCR assay which detects a fragment of the Rickettsia genus-specific 17-kDa antigen gene (htrA), five ticks (25%) were found to contain rickettsial DNA. One rickettsial isolate was obtained from these ticks by inoculating a suspension of a triturated tick into monolayers of Vero E6 monkey kidney cells and XTC-2 clawed toad cells, and its cell culture and genotypic characteristics were determined. Fragments of the 16S rRNA, GltA, rOmpA, rOmpB, and Sca4 genes had 100%, 100%, 99%, 99%, and 99%, respectively, nucleotide similarity to Rickettsia massiliae strain Bar29, previously isolated from R. sanguineus in Catalonia, Spain (L. Beati et al., J. Clin. Microbiol. 34:2688-2694, 1996). The new isolate, AZT80, does not elicit cytotoxic effects in Vero cells and causes a persistent infection in XTC-2 cells. The AZT80 strain is susceptible to doxycycline but resistant to rifampin and erythromycin. Whether R. massiliae AZT80 is pathogenic or infectious for dogs and humans or can cause seroconversion to spotted fever group antigens in the United States is unknown.
TL;DR: The 64TRP vaccine demonstrates the potential to control vector-borne disease by interfering with pathogen transmission, apparently by mediating a local cutaneous inflammatory immune response at the tick-feeding site.
Abstract: Vaccines that target blood-feeding disease vectors, such as mosquitoes and ticks, have the potential to protect against the many diseases caused by vector-borne pathogens. We tested the ability of an anti-tick vaccine derived from a tick cement protein (64TRP) of Rhipicephalus appendiculatus to protect mice against tick-borne encephalitis virus (TBEV) transmitted by infected Ixodes ricinus ticks. The vaccine has a “dual action” in immunized animals: when infested with ticks, the inflammatory and immune responses first disrupt the skin feeding site, resulting in impaired blood feeding, and then specific anti-64TRP antibodies cross-react with midgut antigenic epitopes, causing rupture of the tick midgut and death of engorged ticks. Three parameters were measured: “transmission,” number of uninfected nymphal ticks that became infected when cofeeding with an infected adult female tick; “support,” number of mice supporting virus transmission from the infected tick to cofeeding uninfected nymphs; and “survival,” number of mice that survived infection by tick bite and subsequent challenge by intraperitoneal inoculation of a lethal dose of TBEV. We show that one dose of the 64TRP vaccine protects mice against lethal challenge by infected ticks; control animals developed a fatal viral encephalitis. The protective effect of the 64TRP vaccine was comparable to that of a single dose of a commercial TBEV vaccine, while the transmission-blocking effect of 64TRP was better than that of the antiviral vaccine in reducing the number of animals supporting virus transmission. By contrast, the commercial antitick vaccine (TickGARD) that targets only the tick's midgut showed transmission-blocking activity but was not protective. The 64TRP vaccine demonstrates the potential to control vector-borne disease by interfering with pathogen transmission, apparently by mediating a local cutaneous inflammatory immune response at the tick-feeding site.
TL;DR: The presence of the vector tick in most villages investigated and its high infection rate suggest that TBRF is a common cause of fever in most rural areas of Senegal, Mauritania, and Mali.
TL;DR: Migratory birds appear to be reservoir hosts for B. lusitaniae-infected larvae, and ticks infected by Borrelia burgdorferi sensu lato on birds during their migrations was studied in Switzerland.
Abstract: The prevalence of ticks infected by Borrelia burgdorferi sensu lato on birds during their migrations was studied in Switzerland. A total of 1,270 birds captured at two sites were examined for tick infestation. Ixodes ricinus was the dominant tick species. Prevalences of tick infestation were 6% and 18.2% for birds migrating northward and southward, respectively. Borrelia valaisiana was the species detected most frequently in ticks, followed by Borrelia garinii and Borrelia lusitaniae. Among birds infested by infected ticks, 23% (6/26) were infested by B. lusitaniae-infected larvae. Migratory birds appear to be reservoir hosts for B. lusitaniae.
TL;DR: Results suggest that ticks comprising five species from two genera should be considered in differential diagnosis while examining cases of acute febrile illnesses in humans as well as animals in the ROK.
Abstract: In order to investigate the prevalence of tick-borne infectious agents among ticks, ticks comprising five species from two genera (Hemaphysalis spp. and Ixodes spp.) were screened using molecular techniques. Ticks (3,135) were collected from small wild-caught mammals or by dragging/flagging in the Republic of Korea (ROK) and were pooled into a total of 1,638 samples (1 to 27 ticks per pool). From the 1,638 tick samples, species-specific fragments of Anaplasma phagocytophilum (1 sample), Anaplasma platys (52 samples), Ehrlichia chaffeensis (29 samples), Ehrlichia ewingii (2 samples), Ehrlichia canis (18 samples), and Rickettsia rickettsii (28 samples) were amplified by PCR assay. Twenty-one pooled and individual tick samples had mixed infections of two (15 samples) or three (6 samples) pathogens. In addition, 424 spleen samples from small captured mammals (389 rodents, 33 insectivores, and 2 weasels) were screened for selected zoonotic pathogens. Species-specific DNA fragments of A. phagocytophilum (110 samples), A. platys (68 samples), E. chaffeensis (8 samples), E. ewingii (26 samples), E. canis (51 samples), and Rickettsia sp. (22 samples) were amplified by PCR assay. One hundred thirty small mammals had single infections, while 4, 14, and 21 striped field mice (Apodemus agrarius) had mixed infections of four, three, and two pathogens, respectively. Phylogenetic analysis based on nucleotide sequence comparison also revealed that Korean strains of E. chaffeensis clustered closely with those from China and the United States, while the Rickettsia (rOmpA) sequences clustered within a clade together with a Chinese strain. These results suggest that these agents should be considered in differential diagnosis while examining cases of acute febrile illnesses in humans as well as animals in the ROK.
TL;DR: The study suggests that B. burgdorferi-infected I. scapularis can be found over a wide geographic range in Canada, although most may be adventitious ticks carried from endemic areas in the United States and Canada by migrating birds.
Abstract: Passive surveillance for the occurrence of the tick Ixodes scapularis Say (1821) and their infection with the Lyme borreliosis spirochaetes Borrelia burgdorferi s.l. has taken place in Canada since early 1990. Ticks have been submitted from members of the public, veterinarians, and medical practitioners to provincial, federal, and university laboratories for identification, and the data have been collated and B. burgdorferi detected at the National Microbiology Laboratory. The locations of collection of 2,319 submitted I. scapularis were mapped, and we investigated potential risk factors for I. scapularis occurrence (in Quebec as a case study) by using regression analysis and spatial statistics. Ticks were submitted from all provinces east of Alberta, most from areas where resident I. scapularis populations are unknown. Most were adult ticks and were collected in spring and autumn. In southern Quebec, risk factors for tick occurrence were lower latitude and remote-sensed indices for land cover with woodland. B. burgdorferi infection, identified by conventional and molecular methods, was detected in 12.5% of 1,816 ticks, including 10.1% of the 256 ticks that were collected from humans and tested. Our study suggests that B. burgdorferi-infected I. scapularis can be found over a wide geographic range in Canada, although most may be adventitious ticks carried from endemic areas in the United States and Canada by migrating birds. The risk of Lyme borreliosis in Canada may therefore be mostly low but more geographically widespread than previously suspected.
TL;DR: Because of the critical role that 4D8 plays during tick feeding and oviposition, which ultimately results in the reduction of tick progeny, the generic name "subolesin" (Latin, suboles: offspring, progeny) is proposed for tick 4D9 proteins and subA for the subolesin-encoding gene.
TL;DR: The saliva of ticks (Suborder Ixodida) is critical to their survival as parasites and should result in strong responses from the host defence systems but tick saliva appears to have evolved to counter these responses.
TL;DR: Analysis of bacterial communities present in Ixodes scapularis ticks collected from Westchester and Dutchess Counties, New York State indicated significant variations in the bacterial communities depending on tick developmental stage and degree of engorgement, suggesting that these two elements affect microbial diversity within the tick and may in turn influence pathogen transmission to humans and animals after tick bite.
Abstract: Summary
Ixodes scapularis ticks play an important role in the transmission of a wide variety of pathogens between various mammalian species, including humans. Pathogens transmitted by ticks include Borrelia, Anaplasma and Babesia. Although ticks may harbour both pathogenic and non-pathogenic microflora, little is known about how the diversity of the microflora within ticks may influence the transmission of pathogens. To begin addressing this question, we examined the composition of bacterial communities present in Ixodes scapularis collected from Westchester and Dutchess Counties, New York State, at different developmental and nutritional stages. Genetic fingerprints of bacterial populations were generated by temporal temperature gradient gel electrophoresis (TTGE) separation of individual polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments, followed by DNA sequence analysis for bacterial identification. The fingerprints of the TTGE bands were grouped into five clusters. The most abundant DNA sequence found in all the samples was Rickettsia, followed by Pseudomonas and Borrelia. Ralstonia, Anaplasma, Enterobacterias, Moraxella, Rhodococcus and uncultured proteobacterium were present as well. We also determined the prevalence of Anaplasma phagocytophilum and Borrelia burgdorferi by PCR and DNA sequence analysis. Statistical analyses indicated significant variations in the bacterial communities depending on tick developmental stage and degree of engorgement. We suggest that these two elements affect microbial diversity within the tick and may in turn influence pathogen transmission to humans and animals after tick bite.
TL;DR: The results suggest that subolesin appears to be a candidate vaccine antigen that may contribute to control of multiple tick species and the reduction of tick-borne pathogens.
Abstract: Subolesin was recently shown by both gene silencing and immunization with the recombinant protein to protect against tick infestations, and to cause reduced tick survival and degeneration of gut and salivary gland tissues. In this research, we extended these studies by testing whether targeting subolesin by RNAi or vaccination interfered with the ability of ticks to become infected with two tick-borne pathogens, Anaplasma marginale which causes bovine anaplasmosis and Anaplasma phagocytophilum, the causative agent of human granulocytin anaplasmosis. For the A. marginale studies, Dermacentor variabilis males were injected with subolesin dsRNA or saline and then were allowed to feed on cattle with ascending rickettsemias, while for the A. phagocytophilum studies, mice were immunized with the recombinant subolesin protein, infected with the pathogen and then infested with larval Ixodes scapularis. Tick infections were determined by quantitative polymerase chain reaction of gut and salivary gland tissues. In both experimental approaches, tick infections were significantly reduced. These results suggest that subolesin appears to be a candidate vaccine antigen that may contribute to control of multiple tick species and the reduction of tick-borne pathogens.
TL;DR: The specific requirement of a pathogen for a tick salivary protein to persist within the arthropod is demonstrated and provided a paradigm for understanding how Rickettsia-like pathogens are maintained within vectors.
Abstract: Anaplasma phagocytophilum is the agent of human anaplasmosis, the second most common tick-borne illness in the United States. This pathogen, which is closely related to obligate intracellular organisms in the genera Rickettsia, Ehrlichia, and Anaplasma, persists in ticks and mammalian hosts; however, the mechanisms for survival in the arthropod are not known. We now show that A. phagocytophilum induces expression of the Ixodes scapularis salp16 gene in the arthropod salivary glands during vector engorgement. RNA interference-mediated silencing of salp16 gene expression interfered with the survival of A. phagocytophilum that entered ticks fed on A. phagocytophilum-infected mice. A. phagocytophilum migrated normally from A. phagocytophilum-infected mice to the gut of engorging salp16-deficient ticks, but up to 90% of the bacteria that entered the ticks were not able to successfully infect I. scapularis salivary glands. These data demonstrate the specific requirement of a pathogen for a tick salivary protein to persist within the arthropod and provide a paradigm for understanding how Rickettsia-like pathogens are maintained within vectors.
TL;DR: Both host-targeted chemical control and biocontrol of ticks show much promise, and would benefit from further research.
Abstract: Ticks are important vectors of disease-causing pathogens of humans, wildlife, and livestock. Reducing tick abundance is an important but elusive goal. Chemical pesticides applied to habitats occupied by ticks can be effective but appear to have significant negative effects on nontarget organisms. Devices that apply insecticides directly to vertebrate hosts for ticks reduce nontarget effects, and recent field tests support their effectiveness, but securing the devices and avoiding food subsidies to tick hosts remain significant challenges. Recent research has identified several types of organisms that show potential as biological control agents for ticks. Probably the most promising are the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana, which laboratory studies indicate are often highly lethal to several different tick species at multiple life stages. The few field tests undertaken show somewhat weaker impacts on tick survival, but suggest that the effectiveness of these fungi in controlling ticks could be enhanced by (a) identifying or selecting for highly lethal strains; (b) applying fungal spores directly to vertebrate hosts for ticks; and (c) optimizing the dose, delivery medium, and seasonal timing for environmental deployment. Thus both host-targeted chemical control and biocontrol of ticks show much promise, and would benefit from further research.
TL;DR: Little is known about how efficiently ticks acquire and maintain infection in ruminant populations or whether “carrier” domestic ruminants play an important role as reservoirs of infection, but deer, other free‐living ruminans, and wild rodents are also potential sources of infection.
Abstract: The agent that causes tick-borne fever (TBF) in sheep was first described in 1940, 8 years after the disease was first recognized in Scotland. The same agent was soon shown to cause TBF in sheep and pasture fever in cattle in other parts of the UK, Scandinavia, and other parts of Europe. After the initial use of the name Rickettsia phagocytophila, the organism was given the name Cytoecetes phagocytophila to reflect its association with granulocytes and its morphological similarity with Cytoecetes microti. This name continued to be used by workers in the UK until the recent reclassification of the granulocytic ehrlichiae affecting ruminants, horses, and humans as variants of the same species, Anaplasma phagocytophilum. TBF and pasture fever are characterized by high fever, recurrent bacteremia, neutropenia, lymphocytopenia, thrombocytopenia, and general immunosuppression, resulting in more severe secondary infections such as tick pyemia, pneumonic pasteurellosis, listeriosis, and enterotoxemia. During the peak period of bacteremia as many as 90% of granulocytes may be infected. The agent is transmitted transtadially by the hard tick Ixodes ricinus, and possibly other ticks. After patent bacteremia, sheep, goats, and cattle become persistently infected "carriers," perhaps playing an important role in the maintenance of infection, in the flock/herd. Little is known about how efficiently ticks acquire and maintain infection in ruminant populations or whether "carrier" domestic ruminants play an important role as reservoirs of infection, but deer, other free-living ruminants, and wild rodents are also potential sources of infection. During the late 1990s serological evidence of infection of humans was demonstrated in several European countries, creating a renewed interest and increased awareness of the zoonotic potential of TBF variants. More recently, a few cases of human granulocytic anaplasmosis (HGA) have been reported in some European countries, but it remains to be established whether the variants causing HGA in Europe are genetically and biologically different from those causing TBF in ruminants. TBF is readily diagnosed by demonstrating intracytoplasmic inclusions in peripheral blood granulocytes or monocytes of febrile animals or by detecting specific DNA by polymerase chain reaction (PCR), and TBF variants of A. phagocytophilum can be cultivated in tick cell lines, but the differentiation of TBF variants from HGA variants awaits further investigations.
TL;DR: Phylogenetic analysis indicated that the CCHFV isolates obtained in this study clustered in group 5, whose range encompasses southwestern Russian and Kosovo, which is the first evidence of C CHFV in ticks from Turkey.
Abstract: Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus in the family Bunyaviridae, genus Nairovirus. The virus is transmitted to humans through infected tick bites or from direct contact with viremic animals or humans. In the present study, a total of 1,015 adult ticks were collected from cattle (603 specimens), sheep (17 specimens), and goats (395 specimens) in the Kelkit Valley in Turkey. Four tick species were recognized on the animals in the surveyed region. The most abundant species were Rhipicephalus bursa and Hyalomma marginatum marginatum, at 47.68% (484/1,015) and 46.40% (471/1,015), respectively. Reverse transcriptase PCR was used to recover partial sequences of the CCHFV small (S) genome segment. The presence of CCHFV was determined in 3 of 33 (9.09%) R. bursa pools and in 1 of 31 (3.22%) H. m. marginatum pools. Virus sequences from R. bursa were extremely different from those of the Greek CCHFV strain (U04958) isolated from an R. bursa tick. Phylogenetic analysis indicated that the CCHFV isolates obtained in this study clustered in group 5, whose range encompasses southwestern Russian and Kosovo. This is the first evidence of CCHFV in ticks from Turkey. Even though Hyalomma is the main vector for CCHFV, R. bursa may play a role in CCHFV transmission.
TL;DR: Only 5 of the 13 ixodid tick species found were shared by Iberian red deer and wild boar, and these results are important for understanding the role of wild ungulates in the maintenance of tick infestations and to improve tick control programmes.
TL;DR: It is proposed that localized absence of deer (loss of a dilution host) increases tick feeding on rodents, leading to the potential for tick-borne disease hotspots.
Abstract: Deer support high tick intensities, perpetuating tick populations, but they do not support tick-borne pathogen transmission, so are dilution hosts. We test the hypothesis that absence of deer (loss of a dilution host) will result in either an increase or a reduction in tick density, and that the outcome is scale dependent. We use a complementary methodological approach starting with meta-analysis, followed up by a field experiment. Meta-analysis indicated that larger deer exclosures reduce questing (host-seeking) tick density, but as the exclosure becomes smaller (<2.5 ha) the questing tick density is increased (amplified). To determine the consequences for tick-borne pathogen transmission we carried out a field experiment, comparing the intensity of ticks that fed on hosts competent for tick-borne pathogen transmission (rodents) in two small (<1 ha) deer exclosures and their replicated controls. Intensity of larval ticks on rodents was not significantly different between treatments, but nymph intensity, the tick stage responsible for tick-borne encephalitis (TBE) transmission, was higher in deer exclosures. TBE seropositive rodents were found in a deer exclosure but not in the controls. We propose that localized absence of deer (loss of a dilution host) increases tick feeding on rodents, leading to the potential for tick-borne disease hotspots.
TL;DR: The identification of B. divergens and B. major in ticks collected from wild ruminants cast doubt on the postulated strict host specificity of these bovine Babesia species.
Abstract: Concurrent infections with vector-borne pathogens affected a cattle herd in Switzerland, and one of the pathogens was identified as Babesia bigemina, which had never been observed in this country before. Therefore, a survey of the occurrence of ruminant Babesia spp. and their tick vectors in Switzerland was conducted. A total of 2,017 ticks were collected from sheep, goats, cattle, and wild ruminants (deer, roe deer, and chamois) in southern parts of Switzerland and identified morphologically. The vast majority of the ticks (99.2%) were Ixodes ricinus, but 14 ticks from sheep and goats were identified as Dermacentor marginatus and two ticks from wild ruminants were identified as Hemaphysalis punctata. PCR analyses of 700 ticks revealed the presence of Babesia divergens (n = 6), Babesia sp. genotype EU1 (n = 14), and B. major (n = 2), whose suggested occurrence was confirmed in this study by molecular analysis, and the presence of novel Babesia sp. genotype CH1 (n = 4), which is closely related to B. odocoilei and to Babesia sp. genotype RD61 reported from North America. The identification of B. divergens and B. major in ticks collected from wild ruminants cast doubt on the postulated strict host specificity of these bovine Babesia species. Furthermore, the zoonotic Babesia sp. genotype EU1 was detected in ticks collected from domestic animals but was obtained predominantly from ticks collected from wild ruminants. More than one tick containing DNA of different Babesia spp. were collected from two red deer. Hence, the role of these game animals as reservoir hosts of Babesia spp. seems to be important but requires further investigation.
TL;DR: Phylogenetic analysis revealed that the borreliae detected in these ticks belong to the relapsing-fever group and that these are closely related to, if not identical with, B. miyamotoi.
Abstract: We investigated whether host-seeking nymphs and adults of the western blacklegged tick, Ixodes pacificus Cooley & Kohls, the primary vector of Lyme disease spirochetes in far-western North America, are infected naturally with relapsing-fever group spirochetes in Mendocino County, California. Relapsing-fever group borreliae were detected in four (1.7%) of 234 nymphal and two (0.7%) of 282 adult host-seeking I. pacificus ticks by polymerase chain reaction and sequence analysis of the 16S rRNA and flagellin genes, respectively, exhibiting 99 and 98.5% sequence homology to Borrelia miyamotoi Fukunaga. Phylogenetic analysis based on these two genes revealed that the borreliae detected in these ticks belong to the relapsing-fever group and that these are closely related to, if not identical with, B. miyamotoi.
TL;DR: To the authors' knowledge, IricES1 is the most widespread and highly prevalent of any tick-associated symbiont, including tick colonies that have been maintained in the laboratory for varying periods of time.
Abstract: The tick Ixodes ricinus is responsible for the transmission of a number of bacterial, protozoan and viral diseases to humans and animals in Europe and Northern Africa. Female I. ricinus from England, Switzerland and Italy have been found to harbour an intracellular alpha-proteobacterium, designated IricES1, within the cells of the ovary. IricES1 is the only prokaryote known to exist within the mitochondria of any animal or multicellular organism. To further examine the distribution, prevalence and mode of transmission of IricES1, we performed polymerase chain reaction screening of I. ricinus adults from 12 countries across its geographic distribution, including tick colonies that have been maintained in the laboratory for varying periods of time. IricES1 was detected in 100% of field-collected female ticks from all countries examined (n = 128), while 44% of males were found to be infected (n = 108). Those males that are infected appear to harbour fewer bacteria than females. Sequencing of fragments of the 16S rRNA and gyrB genes revealed very low nucleotide diversity among various populations of IricES1. Transmission of IricES1 from engorged adult females to eggs was found to be 100% (n = 31). In tick colonies that had been maintained in the laboratory for several years, a relatively low prevalence was found in females (32%; n = 25). To our knowledge, IricES1 is the most widespread and highly prevalent of any tick-associated symbiont.