Ticks feeding on humans: a review of records on human-biting Ixodoidea with special reference to pathogen transmission

Detection of Leishmania infantum DNA mainly in Rhipicephalus sanguineus male ticks removed from dogs living in endemic areas of canine leishmaniosis

BACKGROUND

Sand flies are the only biologically adapted vectors of Leishmania parasites, however, a possible role in the transmission of Leishmania has been proposed for other hematophagous ectoparasites such as ticks. In order to evaluate natural infection by Leishmania infantum in Rhipicephalus sanguineus ticks, taking into account its close association with dogs, 128 adult R. sanguineus ticks removed from 41 dogs living in endemic areas of canine leishmaniosis were studied.

METHODS

Individual DNA extraction was performed from each tick and whole blood taken from dogs. Dog sera were tested for IgG antibodies to L. infantum antigen by ELISA and L. infantum real-time PCR was performed from canine whole blood samples and ticks.

RESULTS

Leishmania infantum PCR was positive in 13 ticks (10.1%) including one female, (2.0%) and 12 males (15.2%), and in only five dogs (12.2%). Male ticks had a significantly higher infection rate when compared to female R. sanguineus. The percentage of L. infantum seroreactive dogs was 19.5%. All but two PCR positive dogs were seroreactive. Leishmania infantum PCR positive ticks were removed from seropositive and seronegative dogs with a variety of PCR results.

CONCLUSIONS

This study demonstrates high prevalence of L. infantum DNA in R. sanguineus ticks removed from L. infantum seropositive and seronegative dogs. The presence of L. infantum DNA was detected mainly in male ticks possibly due to their ability to move between canine hosts and feed on several canine hosts during the adult life stage. Additional studies are needed to further explore the role of R. sanguineus ticks and in particular, male adults, in both the epidemiology and immunology of L. infantum infection in dogs in endemic areas.

Rate of evolution and molecular epidemiology of tick-borne encephalitis virus in Europe, including two isolations from the same focus 44 years apart

Tick-borne encephalitis virus (TBEV) is a member of the family Flaviviridae. It is transmitted by Ixodes spp. ticks in a cycle involving rodents and small mammals. TBEV has three subtypes: European, Siberian and Far Eastern. The virus causes thousands of cases of meningoencephalitis in Europe annually, with an increasing trend. The increase may be attributed to a complex network of elements, including climatic, environmental and socio-economic factors. In an attempt to understand the evolutionary history and dispersal of TBEV, to existing genetic data we add two novel complete ORF sequences of TBEV strains from northern Europe and the completion of the genome of four others. Moreover, we provide a unique measure for the natural rate of evolution of TBEV by studying two isolations from the same forest on an island in Åland archipelago 44 years apart. For all isolates, we analysed the phylogeny, rate of evolution and probable time of radiation of the different TBEV strains. The results show that the two lineages of TBEV in different Ixodes species have evolved independently for approximately 3300 years. Notably, rapid radiation of TBEV-Eur occurred approximately 300 years ago, without the large-scale geographical clustering observed previously for the Siberian subtype. The measurements from the natural rate of evolution correlated with the estimates done by phylogenetic programs, demonstrating their robustness.

Saliva, salivary gland, and hemolymph collection from Ixodes scapularis ticks

Ticks are found worldwide and afflict humans with many tick-borne illnesses. Ticks are vectors for pathogens that cause Lyme disease and tick-borne relapsing fever (Borrelia spp.), Rocky Mountain Spotted fever (Rickettsia rickettsii), ehrlichiosis (Ehrlichia chaffeensis and E. equi), anaplasmosis (Anaplasma phagocytophilum), encephalitis (tick-borne encephalitis virus), babesiosis (Babesia spp.), Colorado tick fever (Coltivirus), and tularemia (Francisella tularensis) (1-8). To be properly transmitted into the host these infectious agents differentially regulate gene expression, interact with tick proteins, and migrate through the tick (3,9-13). For example, the Lyme disease agent, Borrelia burgdorferi, adapts through differential gene expression to the feast and famine stages of the tick's enzootic cycle (14,15). Furthermore, as an Ixodes tick consumes a bloodmeal Borrelia replicate and migrate from the midgut into the hemocoel, where they travel to the salivary glands and are transmitted into the host with the expelled saliva (9,16-19). As a tick feeds the host typically responds with a strong hemostatic and innate immune response (11,13,20-22). Despite these host responses, I. scapularis can feed for several days because tick saliva contains proteins that are immunomodulatory, lytic agents, anticoagulants, and fibrinolysins to aid the tick feeding (3,11,20,21,23). The immunomodulatory activities possessed by tick saliva or salivary gland extract (SGE) facilitate transmission, proliferation, and dissemination of numerous tick-borne pathogens (3,20,24-27). To further understand how tick-borne infectious agents cause disease it is essential to dissect actively feeding ticks and collect tick saliva. This video protocol demonstrates dissection techniques for the collection of hemolymph and the removal of salivary glands from actively feeding I. scapularis nymphs after 48 and 72 hours post mouse placement. We also demonstrate saliva collection from an adult female I. scapularis tick.

First report of human biting activity of Ixodes acutitarsus (Acari: Ixodidae) collected in Taiwan

Ixodes acutitarsus is said to be the largest Ixodes tick in the world. Human biting activity of I. acutitarsus was reported for the first time in Taiwan. Ticks were observed from April to December and collected from infested humans during trips to the mountainous areas of northern, central, southern and eastern Taiwan. Host range, seasonal prevalence, and the vectorial capacity of I. acutitarsus ticks for various human pathogens need to be further identified.

Seasonal abundance and activity of the hard tick Haemaphysalis longicornis (Acari: Ixodidae) in North China

Seasonal abundance and activity of all the three post-embryogenic stages of Haemaphysalis longicornis, both feeding and free-living phases, were evaluated over a period of 2 years, from February 2008 to January 2010, in North China. Feeding ticks were removed weekly from head and ears of domestic sheep and the attachment sites of this tick were assessed co-instantaneously; free-living ticks were collected weekly in four habitat types by flag-dragging. The results suggested that H. longicornis mainly resides in shrubs and completes one generation per year with population attrition between stages. Infestation of nymphs was detected from March to September with highest peak between late April and early May; adults were detected from April to September with highest peak between late June and July, and an overwintering male population was found during late September to March; infestation of larvae was observed from June to October and peaked between middle August and early September. Most of this tick (91%) attached to head and ears of hosts. Additionally, we captured rodents from April to September 2008, but only a negligible number of nymphs were detected. This result suggested that rodents are not the principal hosts for this tick in the study area.

A tick mannose-binding lectin inhibitor interferes with the vertebrate complement cascade to enhance transmission of the lyme disease agent

The Lyme disease agent Borrelia burgdorferi is primarily transmitted to vertebrates by Ixodes ticks. The classical and alternative complement pathways are important in Borrelia eradication by the vertebrate host. We recently identified a tick salivary protein, designated P8, which reduced complement-mediated killing of Borrelia. We now discover that P8 interferes with the human lectin complement cascade, resulting in impaired neutrophil phagocytosis and chemotaxis and diminished Borrelia lysis. Therefore, P8 was renamed the tick salivary lectin pathway inhibitor (TSLPI). TSLPI-silenced ticks, or ticks exposed to TSLPI-immune mice, were hampered in Borrelia transmission. Moreover, Borrelia acquisition and persistence in tick midguts was impaired in ticks feeding on TSLPI-immunized, B. burgdorferi-infected mice. Together, our findings suggest an essential role for the lectin complement cascade in Borrelia eradication and demonstrate how a vector-borne pathogen co-opts a vector protein to facilitate early mammalian infection and vector colonization.

Gotch ear: a poorly described, local, pathologic condition of livestock associated primarily with the Gulf Coast tick, Amblyomma maculatum

Gotch ear is a condition in animals in which the ear is swollen, deformed, curled, drooped, possibly necrotic, and is usually associated with attachment by the Gulf Coast tick, Amblyomma maculatum. Little is known of the etiology or epidemiology of gotch ear in livestock. Reports generally describe the condition in cattle, but it has also been reported in horses and mules and more recently in a goat. This review explores the history and etymology of the term "gotch ear" and reports on current status, pathogenesis, differential diagnosis, and epidemiology of gotch ear. Finally, clinical definition of gotch ear is offered.

An assessment of genetic differences among ixodid ticks in a locus within the nuclear large subunit ribosomal RNA gene

We examined the usefulness of the D3 domain and flanking core regions (=D3(+)) of the nuclear large subunit (LSU) ribosomal DNA as a genetic marker for species-level identification and the inference of evolutionary relationships of ixodid ticks. Genetic variation was also examined in relation to the secondary structure of the LSU rDNA. The results revealed a lack of sequence difference in the D3(+) among species of Dermacentor and among some species of Ixodes, demonstrating that this gene region is not suitable as a species marker for all species of ixodid ticks. Of the 45 variable nucleotide positions in the sequence alignment of the D3(+), 23 did not alter the secondary structure of the LSU rDNA, because they occurred in unpaired positions, whereas 16 represented partial or full compensatory changes which maintained the secondary structure. Six deletions in the D3(+) sequence of all Ixodes species examined resulted in a shorter d4_1 helix compared with that of other tick species. The results of the phylogenetic analyses also showed that the D3(+) is of limited value in resolving evolutionary relationships among ixodid ticks. In addition, we also demonstrated that the D3(+) of ascomycete fungi could also be amplified along with, or instead of, the D3(+) of some tick species, depending upon the primers used in PCR. Nonetheless, the D3(+) of the fungal contaminants are readily distinguished from the D3(+) of ixodid ticks because of a shorter length and the absence of helix d4_1 in the secondary structure of the LSU rDNA.

Transport of Babesia venatorum-infected Ixodes ricinus to Norway by northward migrating passerine birds

Background

Bovine babesiosis is regarded as a limited health problem for Norwegian cows, and the incidence has decreased markedly since the 1930s. Rare cases of babesiosis in splenectomised humans from infection with Babesia divergens and B.venatorum have been described. The objective of this study was to determine whether birds can introduce Babesia-infected ticks. There are between 30 and 85 million passerine birds that migrate to Norway every spring.

Methods

Passerine birds were examined for ticks at four bird observatories along the southern Norwegian coast during the spring migrations of 2003, 2004 and 2005. The presence of Babesia was detected in the nymphs of Ixodes ricinus by real-time PCR. Positive samples were confirmed using PCR, cloning and phylogenetic analyses.

Results

Of 512 ticks examined, real-time PCR revealed five to be positive (1.0%). Of these, four generated products that indicated the presence of Babesia spp.; each of these were confirmed to be from Babesia venatorum (EU1). Two of the four B. venatorum-positive ticks were caught from birds having an eastern migratory route (P< 0.001).

Conclusions

Birds transport millions of ticks across the North Sea, the Skagerrak and the Kattegat every year. Thus, even with the low prevalence of Babesia-infected ticks, a substantial number of infected ticks will be transported into Norway each year. Therefore, there is a continuous risk for introduction of new Babesia spp. into areas where I. ricinus can survive.

First survey on hard ticks (Ixodidae) collected from humans in Romania: possible risks for tick-borne diseases

The importance of studies on the diversity of ticks attacking humans resides mostly in the relatively highly-specific tick-pathogen associations. Human tick bites are commonly reported worldwide but removal of ticks from patients is rarely followed by specific identification of the ticks, leaving to some degree of hazard the preventive treatment of possible associated diseases. A total number of 308 ticks were collected between April and June 2010 from 275 human patients who voluntarily presented to a hospital from Cluj-Napoca, Romania. The mean intensity of infection was 1.12 ± 0.46. Four species of ticks were identified Ixodes ricinus, Dermacentor marginatus, Haemaphysalis concinna and H. punctata. Ixodes ricinus was the most abundant species feeding on humans in the study area. A brief review of possible associated pathogen is provided.

Ticks on humans in Ankara, Turkey

In this study, a total of 5,094 ticks found on humans were examined in terms of species, development stage, gender, host features and seasonality for a year period. Of these ticks 17 were argasid and 5,077 were ixodid. Predominantly species of the ixodid genera Hyalomma, Dermacentor, Rhipicephalus and Haemaphysalis were found on humans in Ankara (Anatolia). Most abundant were Hyalomma nymphs (29.8%) and adults (28.2%). Primary factors in terms of tick bite risk were region, habitat and season.

Ixodid ticks in Bosnia and Herzegovina

Ticks of the Ixodidae family represent an enormous threat to human and animal health. From January to December 2004, a total of 10,050 ixodid ticks were collected from 26 areas in Bosnia and Herzegovina and determined to the species level. Ticks were collected from dogs, sheep, cows, goats, rodents, humans and plants. Ixodes ricinus was the most prevalent species, followed by Dermacentor marginatus marginatus, Rhipicephalus bursa, Hyalomma marginatum marginatum, Rhipicephalus sanguineus, Haemaphysalis punctata, Dermacentor reticulatus and Ixodes hexagonus.

Growth of Coxiella burnetii in the Ixodes scapularis-derived IDE8 tick cell line

Q fever, a zoonotic disease, is caused by a gram-negative intracellular bacterium, Coxiella burnetii. Although normally transmitted during exposure to infectious aerosols, C. burnetii is also found in arthropod vectors. In the environment, ticks are thought to play a crucial role in bacterial maintenance and transmission by infecting various mammalian species. However, the nature of the pathogen-tick relationship is not well defined. To determine C. burnetii's interactions with a cultured tick cell line, we introduced purified C. burnetii NMII into Ixodes scapularis-derived IDE8 cells and assayed for bacterial presence, replication, gene expression, and subsequent infectivity for mammalian cells. Tick cells were harvested at 24 h, 72 h, 7 days, and 11 days postinfection (PI). C. burnetii uptake and subsequent replication was demonstrated by indirect immunofluorescence assay, electron microscopy, and real-time polymerase chain reaction (PCR). When a genome equivalent multiplicity of infection of 30 was used, 30%-40% of exposed cells were seen to have small, rounded, vacuoles at 72 h PI, whereas at 7 and 11 days PI, 60%-70% of cells contained enlarged vacuoles harboring large numbers of bacteria. Quantitative PCR analysis of total genomic DNA confirmed that C. burnetii genome numbers increased significantly from 24 h to 11 days PI. Expression of C. burnetii type four secretion system homologs at 7 days PI was demonstrated by reverse transcriptase PCR. Finally, indirect immunofluorescence assay demonstrated that C. burnetii propagated within IDE8 cells were infectious for mammalian cells. These studies demonstrate the utility of cultured tick cell lines as a model to investigate C. burnetii's molecular interactions with its arthropod vectors.

Assessment of bacterial diversity in the cattle tick Rhipicephalus (Boophilus) microplus through tag-encoded pyrosequencing

Background

Ticks are regarded as the most relevant vectors of disease-causing pathogens in domestic and wild animals. The cattle tick, Rhipicephalus (Boophilus) microplus, hinders livestock production in tropical and subtropical parts of the world where it is endemic. Tick microbiomes remain largely unexplored. The objective of this study was to explore the R. microplus microbiome by applying the bacterial 16S tag-encoded FLX-titanium amplicon pyrosequencing (bTEFAP) technique to characterize its bacterial diversity. Pyrosequencing was performed on adult males and females, eggs, and gut and ovary tissues from adult females derived from samples of R. microplus collected during outbreaks in southern Texas.

Results

Raw data from bTEFAP were screened and trimmed based upon quality scores and binned into individual sample collections. Bacteria identified to the species level include Staphylococcus aureus, Staphylococcus chromogenes, Streptococcus dysgalactiae, Staphylococcus sciuri, Serratia marcescens, Corynebacterium glutamicum, and Finegoldia magna. One hundred twenty-one bacterial genera were detected in all the life stages and tissues sampled. The total number of genera identified by tick sample comprised: 53 in adult males, 61 in adult females, 11 in gut tissue, 7 in ovarian tissue, and 54 in the eggs. Notable genera detected in the cattle tick include Wolbachia, Coxiella, and Borrelia. The molecular approach applied in this study allowed us to assess the relative abundance of the microbiota associated with R. microplus.

Conclusions

This report represents the first survey of the bacteriome in the cattle tick using non-culture based molecular approaches. Comparisons of our results with previous bacterial surveys provide an indication of geographic variation in the assemblages of bacteria associated with R. microplus. Additional reports on the identification of new bacterial species maintained in nature by R. microplus that may be pathogenic to its vertebrate hosts are expected as our understanding of its microbiota expands. Increased awareness of the role R. microplus can play in the transmission of pathogenic bacteria will enhance our ability to mitigate its economic impact on animal agriculture globally. This recognition should be included as part of analyses to assess the risk for re-invasion of areas like the United States of America where R. microplus was eradicated.

Identification and characterization of Ixodes scapularis antigens that elicit tick immunity using yeast surface display

Repeated exposure of rabbits and other animals to ticks results in acquired resistance or immunity to subsequent tick bites and is partially elicited by antibodies directed against tick antigens. In this study we demonstrate the utility of a yeast surface display approach to identify tick salivary antigens that react with tick-immune serum. We constructed an Ixodes scapularis nymphal salivary gland yeast surface display library and screened the library with nymph-immune rabbit sera and identified five salivary antigens. Four of these proteins, designated P8, P19, P23 and P32, had a predicted signal sequence. We generated recombinant (r) P8, P19 and P23 in a Drosophila expression system for functional and immunization studies. rP8 showed anti-complement activity and rP23 demonstrated anti-coagulant activity. Ixodes scapularis feeding was significantly impaired when nymphs were fed on rabbits immunized with a cocktail of rP8, rP19 and rP23, a hall mark of tick-immunity. These studies also suggest that these antigens may serve as potential vaccine candidates to thwart tick feeding.

Differences in questing tick species distribution between Atlantic and continental climate regions in Spain

Climate and vegetation in Spain vary from north to south, affecting tick distribution and consequently the presence of tick-borne diseases. The aim of this study was to investigate throughout a 2-yr study the distribution of the different exophilic questing tick species present in 18 areas: eight located in central and 10 in northern Spain. The same methodology was used in both areas, sampling vegetation on a monthly basis by blanket dragging for 20- to 30-min intervals. A total of 12 species belonging to the genera Ixodes, Haemaphysalis, Rhipicephalus, Dermacentor, and Hyalomma was identified. Differences in species distribution and prevalence were dramatically different. The most frequent and abundant species in northern Spain were Ixodes ricinus (67% of adult ticks) and Haemaphysalis punctata (8%), whereas Hyalomma lusitanicum (86%) and Dermacentor marginatus (12%) were the most abundant in central Spain. There were important differences in the monthly seasonal patterns for the different tick species. These results highlight important differences in tick distribution in neighboring areas and underline the need for ongoing surveillance programs to monitor tick population dynamics and the prevalence of tick-borne pathogens.

Omsk haemorrhagic fever

Omsk haemorrhagic fever is an acute viral disease prevalent in some regions of western Siberia in Russia. The symptoms of this disease include fever, headache, nausea, severe muscle pain, cough, and moderately severe haemorrhagic manifestations. A third of patients develop pneumonia, nephrosis, meningitis, or a combination of these complications. The only treatments available are for control of symptoms. No specific vaccine has been developed, although the vaccine against tick-borne encephalitis might provide a degree of protection against Omsk haemorrhagic fever virus. The virus is transmitted mainly by Dermacentor reticulatus ticks, but people are mainly infected after contact with infected muskrats (Ondatra zibethicus). Muskrats are very sensitive to Omsk haemorrhagic fever virus. The introduction of this species to Siberia in the 1930s probably led to viral emergence in this area, which had previously seemed free from the disease. Omsk haemorrhagic fever is, therefore, an example of a human disease that emerged owing to human-mediated disturbance of an ecological niche. We review the biological properties of the virus, and the epidemiological and clinical characteristics of Omsk haemorrhagic fever.

Frecuencia relativa de Boophilus microplus (Canestrini 1888) & Amblyomma cajennense (Fabricius 1787) (Acari: Ixodida) en ganado bovino, en la zona de colonización de Yucumo, Provincia Gral. José Ballivián Departamento del Beni, Bolivia

El estudio sobre la abundancia relativa de Boophilus microplus & Amblyomma cajennense se realizó en 32 colonias, distribuidas en dos zonas ecológicas (ZE) y dos regímenes pluviales de la zona de Yucumo, Beni Bolivia. Se efectuaron visitas cada veinte día para recolectar acarinos de la población de ganado bovino utilizando el método del derribe. El número total de acarinos se consideraba, el total de ectoparásitos muestreados de cada animal y se sumaban todos los animales muestreados de cada colonia, el valor de cada animal se lo dividía entre el total de los animales de cada colonia para determinar el promedio de garrapatas por colonia. Se detectó B. microplus en todas las colonias, a lo largo de los meses de mayo a octubre (2008). Se hicieron análisis estadísticos de comparación de medias y no se encontraron diferencias entre ZE, colonias para Boophilus microplus, en tanto Amblyomma cajennense se la encontró en asociación con Boophilus microplus en la pradera. Pese a que no se encontraron diferencias entre sistemas de producción, se hace énfasis en que la frecuencia relativa de infestación del ganado en las ZE estudiadas es muy similar a excepción de la colonia 6 de agosto que corresponde a la ZE serranía que presenta valores elevados de acarinos por animal. Se recomienda la necesidad de desarrollar trabajos que permitan conocer la diversidad de este importante grupo de artrópodos en la zona de colonización de Yucumo, provincia Gral. José Ballivián, Beni, Bolivia, teniendo en cuenta la posibilidad que estas provoquen problemas de salud publica no solo en animales, sino que lleguen a afectar al ser humano.

Seasonal dynamics of the brown dog tick, Rhipicephalus sanguineus, on a confined dog population in Italy

This study evaluated the seasonal dynamics of Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae) on naturally infested dogs in a private shelter in southern Italy. From March to May 2008, 39 autochthonous mixed-breed young dogs and 10 beagles were enrolled in the study. From March 2008 until March 2009, every 21 +/- 2 days, 11 body sites of each dog were checked for ticks. At each follow-up, the number of ticks, their developmental stage, sex and location on the dog's body were recorded. Adult ticks were found throughout the year, but immatures were absent in January and February. The adult tick population increased from July to August, whereas the load of immatures increased in early July and peaked in September, which suggests that R. sanguineus develops one generation per year in this area. The mean number of immature ticks per infested dog was higher than that of adults from March to October 2008. Ears, interdigital areas and armpits were the most frequent attachment sites of adult ticks. At the last follow-up, a total of 2266 ticks were collected and identified as R. sanguineus. The results suggest that R. sanguineus develops one generation per year in the study area, but that it infests dogs in all seasons. This information should be taken into account when planning control programmes against this tick species and the pathogens it transmits.

A proteomics approach for the analysis of hemolymph proteins involved in the immediate defense response of the soft tick, Ornithodoros savignyi, when challenged with Candida albicans

A proteomics approach was employed to identify proteins secreted into the hemolymph of Ornithodorus savignyi ticks 2 h after immune-challenge with the yeast, Candida albicans. Profiling of the proteins present in hemolymph of unchallenged ticks versus ticks challenged with heat-killed yeast revealed five proteins to be differentially expressed. The modulated protein spots were subjected to tandem mass spectrometry (MS/MS) analysis, but could not be positively identified. These proteins can be assigned to the immune response as they were not induced after aseptic injury. In an attempt to identify hemolymph proteins that recognize and bind to yeast cells, hemolymph obtained from both unchallenged and challenged ticks was incubated with C. albicans. Elution of the bound proteins followed by SDS-PAGE analysis indicated that three proteins (97, 88 and 26 kDa) present in both unchallenged and challenged hemolymph samples bind to yeast cells. The constant presence of these three proteins in tick hemolymph leads us to believe that they may be involved in non-self recognition and participate in yeast clearance from tick plasma. The analyzed yeast-binding proteins could also not be positively identified, suggesting that all the tick immune proteins investigated in this study are novel.

Discrimination of relapsing fever Borrelia persica and Borrelia microtti by diagnostic species-specific primers and polymerase chain reaction-restriction fragment length polymorphism

Tick-borne relapsing fever (TBRF) is endemic in Africa and Eurasia and attributed to different Borrelia species. In the Central Asia and Middle Eastern countries, TBRF is caused mainly by Borrelia persica; however, other Borrelia species such B. microtti, B. latyschewii, B. baltazardi, and B. caucasica have also been described. The classic taxonomy of Borrelia spp. is based on the cospeciation concept that is very complex and rather confusing. In this study, we report two DNA-based methods to discriminate B. persica and B. microtti, the two main prevalent species in the region. Molecular typing of the species was performed using (i) restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified fragments of either 16S-rRNA or glpQ genes, and (ii) species-specific PCR of glpQ gene. Sequence analyses of the data obtained in this study indicate that the glpQ gene is more variable than 16S-rRNA (6.9% vs. 1.2%); thus glpQ is a more useful marker for discrimination of B. persica from B. microtti. The 16S-rRNA fragment comprises only one useful species-specific restriction site (TaqI), whereas the glpQ fragment includes several species-specific restriction sites and its digestion by DraI, TaqI, EcoRV, HinfI, or SspI results in distinctively different PCR-restriction fragment length polymorphism patterns for the two species. Further, the species-specific primers amplified a 253-bp fragment for B. persica and a 451-bp one for B. microtti. Phylogenetic analysis of the data revealed that B. microtti and B. persica are associated to the African and new world RF agents, respectively. This study demonstrates that both typing methods are simple, sensitive, and fast, and that they allow one to differentiate between B. persica and B. microtti. This could prove that both methods are important and useful in monitoring of TBRF disease in endemic areas.

Biology and ecology of the brown dog tick, Rhipicephalus sanguineus

The brown dog tick (Rhipicephalus sanguineus) is the most widespread tick in the world and a well-recognized vector of many pathogens affecting dogs and occasionally humans. This tick can be found on dogs living in both urban and rural areas, being highly adapted to live within human dwellings and being active throughout the year not only in tropical and subtropical regions, but also in some temperate areas. Depending on factors such as climate and host availability, Rh. sanguineus can complete up to four generations per year. Recent studies have demonstrated that ticks exposed to high temperatures attach and feed on humans and rabbits more rapidly. This observation suggests that the risk of human parasitism by Rh. sanguineus could increase in areas experiencing warmer and/or longer summers, consequently increasing the risk of transmission of zoonotic agents (e.g., Rickettsia conorii and Rickettsia rickettsii). In the present article, some aspects of the biology and ecology of Rh. sanguineus ticks are discussed including the possible impact of current climate changes on populations of this tick around the world.

Ticks (Acari: Ixodidae) on domestic dogs in Serra de Caldas Novas State Park, Goiás: epidemiological aspects

We herein report tick (Acari: Ixodidae) infestation of four domestic dogs wandering inside Serra de Caldas Novas State Park, Goiás. Twenty seven ticks were collected from these hosts along nine days in November 2008. Ticks were identified as adults of Amblyomma cajennense, Amblyomma ovale, Amblyomma tigrinum and Rhipicephalus sanguineus as well as Amblyomma spp. nymphs. One of the dogs displayed facial myoclonus, a symptom of canine distemper. Such disease is a serious viral and contagious disease of dogs and also of several wild animals. Overall tick species found on dogs clearly showed the transit of these hosts between the natural areas of the park and anthropic areas, urban or rural. Such situation illustrates the potential of dogs to transmit contagious and vector-borne diseases to wild canids. Our results reinforce the importance of control of dogs living free without responsible owner, to the Brazilian fauna conservation, particularly close to conservation units.

Effect of vaccination with a recombinant metalloprotease from Haemaphysalis longicornis

We report the cloning, expression and characterization of an Haemaphysalis longicornis metalloprotease (named HLMP1). The gene encodes a predicted 550 aminoacid protein with similarity to metalloproteases of the reprolysin family. The protein sequence contains a signal sequence, the zinc-binding motif (HEXXHXXGXXH) common to metalloproteases and a cysteine-rich region. Reverse transcription-PCR expression analysis indicates the presence of mRNA in the salivary gland of larva, nymph and adult ticks. Rabbit repeatedly infested with H. longicornis recognized rHLMP1, suggesting that the immune-response against HLMP1 is naturally induced through the feeding of ticks. Vaccination of rabbit with rHLMP1 produced protective immunity against ticks, resulting in 15.6 and 14.6% mortality in nymph and adult ticks, respectively. This work provides information to understand the tick's defense system, and offers new insights to develop strategies to block this defense system with an anti-tick vaccine based on a metalloprotease.

Acaricidal effects of Corymbia citriodora oil containing para-menthane-3,8-diol against nymphs of Ixodes ricinus (Acari: Ixodidae)

The toxicity of para-menthane-3,8-diol (PMD), the main arthropod-repellent compound in the oil of the lemon eucalyptus, Corymbia citriodora, was evaluated against nymphs of Ixodes ricinus using five methods (A-E) of a contact toxicity bioassay. Mortality rates were estimated by recording numbers of dead nymphs at 30 min intervals during the first 5 h after the start of exposure and at longer intervals thereafter. The mortality rate increased with increasing concentration of PMD and duration of exposure with a distinct effect after 3.5 h. From the results obtained by methods A, C and E, the LC(50) range was 0.035-0.037 mg PMD/cm(2) and the LC(95) range was 0.095-0.097 mg PMD/cm(2) at 4 h of exposure; the LT(50) range was 2.1-2.8 h and the LT(95) range was 3.9-4.2 h at 0.1 mg PMD/cm(2). To determine the duration of toxic activity of PMD, different concentrations (0.002, 0.01, 0.1 mg PMD/cm(2)) were tested and mortality was recorded at each concentration after 1 h; thereafter new ticks were tested. This test revealed that the lethal activity of PMD remained for 24 h but appeared absent after 48 h. The overall results show that PMD is toxic to nymphs of I. ricinus and may be useful for tick control.

Genetic variation in the 16S mitochondrial DNA gene of two Canadian populations of Dermacentor andersoni (Acari: Ixodidae)

The Rocky Mountain wood tick, Dermacentor andersoni Stiles, 1908, is of medical and veterinary importance because it can transmit pathogenic agents to humans, domestic livestock, and wildlife. The preferred attachment sites of D. andersoni adults and their ability to induce paralysis in hosts vary among populations, which may have a genetic basis. In this study, polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) analyses and DNA sequencing were used to determine the genetic variation in the 16S mitochondrial DNA gene of two D. andersoni populations from the Canadian prairies: Saskatchewan Landing Provincial Park, Saskatchewan, and Lethbridge, Alberta. Five haplotypes were detected in each population, but this was considerably lower than the 14 haplotypes reported in a previous study of a laboratory colony of D. andersoni originating from the Rocky Mountains in Montana. In addition, the Canadian populations did not share any haplotypes with the population from Montana. Differences in the genetic composition of the two Canadian prairie populations of D. andersoni compared with the montane population in the United States may have arisen through geographical isolation. These genetic differences between tick populations may also have important implications with respect to their ability to transmit pathogens to hosts. Further studies are needed to determine the extent of genetic variation and the vector potential of ticks from different populations throughout the range of D. andersoni in the United States and Canada.

Amblyomma americanum (L): tick macrophage migration inhibitory factor peptide immunization lengthens lone star tick feeding intervals in vivo

Immunizations of New Zealand White rabbits with specific macrophage migration inhibitory factor (MIF) tick peptide (PEP) produced circulating anti-tick PEP antibodies in the hosts. Antibody titers of greater than 1:5000 to tick MIF peptide were observed for crude sera from PEP-immunized rabbits. PEP- and BSA-vaccinated rabbits were infested with Amblyomma americanum adults. Feeding intervals, female weights, egg masses and percent egg hatch were measured for ticks feeding on control and immunized hosts. Feeding intervals were significantly lengthened to 13.3 days for PEP-vaccinated hosts compared to BSA-vaccinated controls at 12.4 days, while female engorgement weights and egg masses were unchanged. By immunizing hosts using specific tick PEP, we were able to alter the length of time the ticks fed on their hosts.

Ticks and associated pathogens collected from domestic animals in the Netherlands

Following an outbreak of autochthonous canine babesiosis in the Netherlands, a request made to veterinarians and the public to collect ticks from companion animals resulted in 4298 ticks submitted between July 2005 and October 2006 to our center. Ticks were identified as Ixodes ricinus adults (2907/4298, 67.6%), Ixodes sp. nymphs (529/4298, 12.3%) and Ixodes sp. larvae (385/4298, 9.0%), I. hexagonus adults (328/4298, 7.6%), Dermacentor reticulatus (72/4298, 1.7%), and several other exotic tick species such as Amblyomma flavomaculatum (formerly Aponomma flavomaculatum), Hyalomma marginatum rufipes, Rhipicephalus sanguineus, and R. turanicus (55/4298, 1.3%). Eight localities were surveyed for the presence of local D. reticulatus, a tick not indigenous to the Netherlands, based on multiple submissions of D. reticulatus ticks from these areas. D. reticulatus was collected from the vegetation in six of these localities, confirming the presence of populations of this tick in the Netherlands. Adult I. ricinus (n=251), I. hexagonus (n=237), and D. reticulatus (n=344) ticks were selected at random and subsequently screened by polymerase chain reaction (PCR) and reverse line blot (RLB) hybridization for the presence of Borrelia, Babesia, Theileria, Anaplasma, Ehrlichia, and Rickettsia species. I. ricinus ticks were infected with Rickettsia helvetica (24.7%), spirochetes belonging to the Borrelia burgdorferi sensu lato group (7.2%), the Ehrlichia-like "Schotii" variant (2.4%), Anaplasma phagocytophilum (1.6%), Babesia sp. (EU1) (1.2%), Babesia divergens (0.4%), and Babesia microti (0.4%). A. phagocytophilum (5.9%) and R. helvetica (0.8%) were also detected in adult I. hexagonus ticks. Spotted fever group Rickettsiae, previously reported as Rickettsia sp. DnS14/RpA4 (14.0%), and Borrelia burgdorferi sensu lato (0.3%) were detected in the D. reticulatus ticks, which appeared to be free from B. canis infection. We concluded that a much broader spectrum of ticks and tick-borne pathogens is present in the Netherlands than previously thought, including several potential zoonotic pathogens.

[Influence of aggregation on the molting process of Rhipicephalus sanguineus, (Latreille, 1806) (Acari: Ixodidae) under laboratory conditions]

The objective of this experiment was to evaluate the influence of different aggregations on the molting process of Rhipicephalus sanguineus (Latreille, 1806). Tick-naïve domestic rabbits (Oryctolagus cuniculus) were used as experimental hosts for the parasitic phase. A total of 10 rabbits were used on the experiment. All tick free-living phases were kept in incubator at 27+/-1 degrees C, 80+/-5% relative humidity and scotophase. The periods of pre-molt, molt, percentage of ecdisis and molt rhythm of larvae and nymphs were studied. A total of 1560 engorged larvae and 1560 nymphs of R. sanguineus were divided in six groups of aggregations: 1, 5, 10, 20, 40 and 80 ticks with ten repetitions each one. The ecdises of nymphs and adults were daily observed. The percentage of ecdysis was the only parameter with no aggregations effects. All others parameters were statistically different (p<0,05). The results suggested that highest aggregations accelerate the molting process.

Growth of tick-borne encephalitis virus (European subtype) in cell lines from vector and non-vector ticks

We undertook a comparative study of the susceptibility of different tick cell lines to infection with the European subtype of tick-borne encephalitis virus (TBEV), prototype strain Neudoerfl. The growth of TBEV was investigated in lines derived from vector Ixodes ricinus L. ticks (IRE/CTVM18, 19, and 20), as well as non-vector ticks, namely Ixodes scapularis Say (IDE2), Boophilus microplus Canestrini (BME/CTVM2), Hyalomma anatolicum anatolicum Koch (HAE/CTVM9), Rhipicephalus appendiculatus Neumann (RA-257) and recently established and herein described lines from the argasid tick Ornithodoros moubata Murray (OME/CTVM21 and 22). All the tick cell lines tested were susceptible to infection by TBEV and the virus caused productive infection without any cytopathic effect. However, there was a clear difference between the TBEV growth in vector and non-vector cell lines, since I. ricinus cell lines produced 100-1000-fold higher virus yield than the non-vector cell lines. The lowest virus production was observed in O. moubata and R. appendiculatus cell lines.

Human perception and awareness of ticks in a South Australian rural community and implications for management of Amblyomma triguttatum triguttatum

The ornate kangaroo tick, Amblyomma triguttatum triguttatum, is invasive on Yorke Peninsula, South Australia. To assess the potential for developing comprehensive management strategies for the species, we mailed 1,000 surveys to Yorke Peninsula residents to investigate community perceptions of ticks, gather information on tick-host ecology, and assess whether or not occupation and length of residence affected whether residents had seen ticks. The response rate was 32%; most respondents (63%) had not seen ticks on Yorke Peninsula. Of those who had (n = 104), 56% had seen ticks on animals, especially lizards (31%) and kangaroos (20%); 50% had seen ticks on humans. Of the 64 respondents who believed places on Yorke Peninsula had many ticks, 56% identified Innes National Park and 75% areas on southern Yorke Peninsula. The likelihood of seeing ticks was not related to occupation. Whether respondents had seen ticks was related to length of residence on Yorke Peninsula (<10 years = 23.6%, 10-30 years = 44.0%, 31-50 years = 47.6%, 51-70 years = 30.9%, 71+ years = 21.4%). The number of respondents who had seen ticks on humans suggests that tick-borne diseases could become a public health issue on Yorke Peninsula. This finding is of particular concern because A. t. triguttatum is implicated in the epidemiology of Q fever in Queensland. Finally, respondents were unaware of the responsibility for tick management, which demonstrates a need for collaboration amongst stakeholders.

Molecular detection of spotted fever group rickettsiae in ticks from Ethiopia and Chad

DNA extracted from 363 ticks collected in Ethiopia and 9 ticks collected in Chad, Africa were screened by PCR to detect DNA from spotted fever group rickettsiae. Fifteen ticks (4.1%) collected in Ethiopia and one tick (11%) collected in Chad tested positive when PCR targeting the gltA and ompA rickettsial genes was performed. PCR-positive products of the gltA and ompA genes were used for DNA sequencing. Rickettsia africae was detected in 12/118 Amblyomma lepidum and in 1/2 A. variegatum. Also, 2/12 Hyalomma marginatum rufipes collected in Ethiopia and one H. marginatum rufipes collected in Chad were positive for R. aeschlimannii. Our results confirm the previously reported presence of R. africae in Ethiopia and also show the first evidence of R. aeschlimannii in ticks collected in Ethiopia and Chad.

The brown dog tick, Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae): from taxonomy to control

Rhipicephalus sanguineus, commonly known as the brown dog tick, is a three-host tick that feeds primarily on dogs and occasionally on other hosts, including humans. R. sanguineus ticks are widely distributed around the world and they are known vectors of pathogens, such as Babesia canis, Ehrlichia canis, and Rickettsia conorii. The increasing number of cases of human parasitism by R. sanguineus ticks reported in the literature indicates that the interaction between humans and R. sanguineus ticks may be more common than it is actually recognized. The indiscriminate use of acaricides is an emerging problem worldwide and has led to the selection of acaricide resistant tick strains. In this article, the medical and veterinary importance, taxonomy, biology, and ecology of R. sanguineus ticks around the world are reviewed. It also discusses the current strategies for the control of R. sanguineus, highlighting the potential risks associated to the improper use of acaricides, such as environmental pollution and toxicity to humans and other non-target organisms (e.g., tick predators).

Ticks biting humans in the urban area of Istanbul

A passive surveillance for tick bites in humans was undertaken in the city of Istanbul (Turkey) in the summer and autumn of 2006. From 1,054 reported tick bites, most were females of Ixodes ricinus (27%) and nymphs of Hyalomma aegyptium (50%). A few adults of Hyalomma m. marginatum, Rhipicephalus sanguineus and Dermacentor marginatus were also recorded. We investigated potential risk factors for I. ricinus and H. aegyptium with spatial statistics. Climate features at 1-km resolution (monthly minimum temperatures in late summer and autumn and rainfall) and vegetation features at high resolution (density and heterogeneity of forest-type vegetation as well as distance of reporting site to these vegetation features) are useful variables explaining high reporting clusters for both Ixodes and Hyalomma. While Ixodes is highly reported in dense highly heterogeneous vegetation patches, Hyalomma is commonly found in areas far from forest-type features and in the small, relatively dry vegetation patches within the urban fabric.

Experimental transmission of Anaplasma marginale by male Dermacentor reticulatus

BACKGROUND

Bovine anaplasmosis has been reported in several European countries, but the vector competency of tick species for Anaplasma marginale from these localities has not been determined. Because of the wide distributional range of Dermacentor reticulatus within Europe and the major role of Dermacentor spp. as a vector of A. marginale in the United States, we tested the vector competency of D. reticulatus for A. marginale.

RESULTS

Male D. reticulatus were allowed to feed for 7 days on a calf persistently infected with a Zaria isolate of A. marginale, after which they were removed and held off-host for 7 days. The ticks were then allowed to feed a second time for 7 days on a susceptible tick-naïve calf. Infection of calf No. 4291 was detected 20 days post exposure (p.i.) and confirmed by msp4 PCR. Thirty percent of the dissected acquisition fed ticks was infected. In addition, A. marginale colonies were detected by light microscopy in the salivary glands of the acquisition fed ticks. Transmission of A. marginale to calf No. 9191 was confirmed by examination of Giemsa-stained blood smears and msp4 PCR. Ticks were dissected after transmission feeding and presence of A. marginale was confirmed in 18.5% of the dissected ticks.

CONCLUSION

This study demonstrates that D. reticulatus males are competent vectors of A. marginale. Further studies are needed to confirm the vector competency of D. reticulatus for other A. marginale strains from geographic areas in Europe.

Tick vaccines and the transmission of tick-borne pathogens

Ticks transmit pathogens that cause diseases which greatly impact both human and animal health. Vaccines developed against Boophilus spp. using Bm86 and Bm95 tick gut antigens demonstrated the feasibility of using vaccines for control of tick infestations. These vaccines also reduced transmission of tick-borne pathogens by decreasing exposure of susceptible hosts to ticks. The recently discovered tick antigens, 64P putative cement protein and subolesin involved in the regulation of tick feeding and reproduction, were also shown to reduce tick infestations. These antigens, together with the TROSPA receptor for Burrelia burgdorferi OspA were effective against tick-borne pathogens by reducing the infection levels in ticks and/or the transmission of the pathogen. Development of a vaccine targeted at both the tick vector and pathogen would contribute greatly to the control of tick infestations and the transmission of tick-borne diseases. These results have demonstrated that tick vaccines can be developed for control tick infestations and show promise for the prevention of the transmission of tick-borne pathogens.

A ten-year review of commercial vaccine performance for control of tick infestations on cattle

Ticks are important ectoparasites of domestic and wild animals, and tick infestations economically impact cattle production worldwide. Control of cattle tick infestations has been primarily by application of acaricides which has resulted in selection of resistant ticks and environmental pollution. Herein we discuss data from tick vaccine application in Australia, Cuba, Mexico and other Latin American countries. Commercial tick vaccines for cattle based on the Boophilus microplus Bm86 gut antigen have proven to be a feasible tick control method that offers a cost-effective, environmentally friendly alternative to the use of acaricides. Commercial tick vaccines reduced tick infestations on cattle and the intensity of acaricide usage, as well as increasing animal production and reducing transmission of some tick-borne pathogens. Although commercialization of tick vaccines has been difficult owing to previous constraints of antigen discovery, the expense of testing vaccines in cattle, and company restructuring, the success of these vaccines over the past decade has clearly demonstrated their potential as an improved method of tick control for cattle. Development of improved vaccines in the future will be greatly enhanced by new and efficient molecular technologies for antigen discovery and the urgent need for a tick control method to reduce or replace the use of acaricides, especially in regions where extensive tick resistance has occurred.