[Epidemiological situation and prophylaxis of zoonotic and natural-focal infectious diseases in Siberia and the Far East]

Analysis of zoonotic and natural-focal infectious disease morbidity in 2009 - 2011 in Siberia and the Far East is presented, and a complex of measures aimed at their prophylaxis is proposed. Analysis is carried out based on the data received by Reference Center of Monitoring of Natural-Focal Infection Causative Agents and Regional Center of Monitoring of I-II Pathogenicity Group Causative Agents at the Irkutsk Research Institute of Plague Control from departments and Centers of Hygiene and Epidemiology of Siberian, Far Eastern, 3 subjects of Urals Federal District and 5 Stations of Plague Control of Federal Service for Control in the Sphere of Protection of Consumers' Rights and Well-Being of Humans. In the morbidity structure in this region "tick-borne" infections were established to predominate--69.4%, among bacterial--yersiniosis dominates. Deterioration of epizootic situation on rabies is observed in the Republics of Tuva and Buryatia.

Vector-borne diseases in humans and animals: Activities of the Swiss Tropical Institute and risks for Switzerland

The recent outbreak of anaplasmosis in a Swiss cattle herd triggered a discussion of the risk of vector-borne diseases in animals and humans in relation to climate changes and other factors. This overview presents the Swiss Tropical Institute's (STI) activities on vector-borne diseases (malaria, trypanosomosis, and leishmaniosis in humans and tick-borne diseases in livestock), describes the possible risks for humans and animals in Switzerland, and discusses options for action in the domains of public health, livestock production and companion animals. Switzerland is increasingly confronted with vector-borne diseases in humans and animals, but this is mainly due to an increase in imported cases. The emergence of a disease in one sector (human or veterinary medicine) may predict future trends in the other. A stronger intersectoral collaboration between public health and veterinary institutions at the federal and cantonal level is needed.

Piroplasmen der Wiederkäuer in der Schweiz und zoonotische Bedeutung der Babesien

Piroplasms are tick-transmitted blood parasites belonging to the genera Babesia and Theileria. In western and southern Switzerland, B. divergens, a small Babesia species, has been known for a long time as a parasite of cattle. Recent investigations have revealed the autochthonous occurrence of this parasite also in central and eastern Switzerland. On the occasion of an outbreak of anaplasmosis in the canton of Grisons, however, B. bigemina, a large Babesia species, and Theileria of the buffeli/sergenti/orientalis species complex were for the first time identified; the epidemiology of these two piroplasms in Switzerland remains unknown until now. The recent identification by genetic analyses of B. divergens in wild ruminants contradicts the hitherto postulated strict host specificity of this Babesia species for cattle. B. divergens as well as the closely related Babesia spp. genotype EU1 have in single cases also been identified in splenectomized humans. The rodent babesia B. microti which causes a human infection that is considered an "emerging tick-borne disease" in the U.S.A., is widespread in rodent populations in Switzerland, but seems to be of minor relevance as zoonotic pathogen here. Reasons for this could be differences in virulence of the parasites or in the transmission by the respective tick-vectors on the two continents.

Cascading effect of economic globalization on human risks of scrub typhus and tick-borne rickettsial diseases

The increase in global travel and trade has facilitated the dissemination of disease vectors. Globalization can also indirectly affect vector-borne diseases through the liberalization of cross-border trade, which has far-reaching, worldwide effects on agricultural practices and may in turn influence vectors through the modification of the ecological landscape. While the cascading effect of economic globalization on vector-borne diseases, sometimes acting synergistically with regional agricultural policy, could be substantial and have significant economic, agricultural, and public health implications, research into this remains very limited. We evaluated how abandonment of rice paddies in Taiwan after joining the World Trade Organization, along with periodic plowing, an agricultural policy to reduce farm pests in abandoned fields can unexpectedly influence risks to diseases transmitted by ticks and chiggers (larval trombiculid mites), which we collected from their small-mammal hosts. Sampling was limited to abandoned (fallow) and plowed fields due to the challenge of trapping small mammals in flooded rice paddies. Striped field mice (Apodemus agrarius) are the main hosts for both vectors. They harbored six times more ticks and three times more chiggers in fallow than in plowed plots. The proportion of ticks infected with Rickettsia spp. (etiologic agent of spotted fever) was three times higher in fallow plots, while that of Orientia tsutsugamushi (scrub typhus) in chiggers was similar in both treatments. Fallow plots had more ground cover and higher vegetation than plowed ones. Moreover, ticks and chiggers in both field types were dominated by species known to infest humans. Because ticks and chiggers should exhibit very low survival in flooded rice paddies, we propose that farm abandonment in Taiwan, driven by globalization, may have inadvertently led to increased risks of spotted fever and scrub typhus. However, periodic plowing can unintentionally mitigate vector burdens. Economic globalization can have unexpected consequences on disease risk through modification of the agricultural landscape, but the outcome may also be influenced by agricultural policies, calling for further research on vector-borne diseases and their control from broader perspectives.

Tick cell lines for study of Crimean-Congo hemorrhagic fever virus and other arboviruses

Continuous cell lines derived from many of the vectors of tick-borne arboviruses of medical and veterinary importance are now available. Their role as tools in arbovirus research to date is reviewed and their potential application in studies of tick cell responses to virus infection is explored, by comparison with recent progress in understanding mosquito immunity to arbovirus infection. A preliminary study of propagation of the human pathogen Crimean-Congo hemorrhagic fever virus (CCHFV) in tick cell lines is reported; CCHFV replicated in seven cell lines derived from the ticks Hyalomma anatolicum (a known vector), Amblyomma variegatum, Rhipicephalus (Boophilus) decoloratus, Rhipicephalus (Boophilus) microplus, and Ixodes ricinus, but not in three cell lines derived from Rhipicephalus appendiculatus and Ornithodoros moubata. This indicates that tick cell lines can be used to study growth of CCHFV in arthropod cells and that there may be species-specific restriction in permissive CCHFV infection at the cellular level.

Tick-borne diseases in Minnesota: an update

Tick-borne diseases endemic to Minnesota include Lyme disease, babesiosis, anaplasmosis/ehrlichiosis, Powassan virus illness and Rocky Mountain spotted fever. Physicians need to be aware of these diseases and be vigilant about testing for them when patients present with acute febrile illness or rash within one month of potential tick exposure. In addition, they need to educate patients about these diseases and encourage prevention measures, especially use of tick repellents. This article reviews the epidemiology of these illnesses in Minnesota and the current recommendations for diagnosis and treatment.

Capybaras and ticks in the urban areas of Uberlândia, Minas Gerais, Brazil: ecological aspects for the epidemiology of tick-borne diseases

In Brazil capybara, the biggest existing rodent species, and associated tick species, Amblyomma cajennense and Amblyomma dubitatum, are undergoing an unplanned host and parasite population expansion in both urban and rural areas. However, scientific information about such issue, particularly in urban areas, is scanty. Such rodent and ticks are associated in some municipalities, particularly in southeastern Brazil, with the transmission of the highly lethal Rickettsia rickettsia caused spotted-fever. In this study ecological aspects related to the establishment and expansion of capybaras and ticks in urban areas of Uberlândia, Minas Gerais State, Brazil were evaluated. For this purpose, capybara and tick abundance in four urban areas and an ecological reserve was determined. Abundance of capybaras varied between areas and over the sampling period and these differences were related to human activities. A positive correlation was found between capybara and tick abundance, however, the tick species had an uneven distribution within the municipality and environmental factors rather than host availability were blamed for such. On the whole these observations show that capybara populations in urban areas are associated to high environmental infestation of ticks and the increased risk of bites and of pathogen transmission to humans. At the same time the uneven distribution of tick species might implicate in an unequal risk of tick-borne diseases within the same urban area.

Ticks of Poland. Review of contemporary issues and latest research

The paper presents current knowledge of ticks occurring in Poland, their medical importance, and a review of recent studies implemented in the Polish research centres on ticks and their significance in the epidemiology of transmissible diseases. In the Polish fauna there are 19 species of ticks (Ixodida) recognized as existing permanently in our country: Argas reflexus, Argas polonicus, Carios vespertilionis, Ixodes trianguliceps, Ixodes arboricola, Ixodes crenulatus, Ixodes hexagonus, Ixodes lividus, Ixodes rugicollis, Ixodes caledonicus, Ixodes frontalis, Ixodes simplex, Ixodes vespertilionis, Ixodes apronophorus, Ixodes persulcatus, Ixodes ricinus, Haemaphysalis punctata, Haemaphysalis concinna, Dermacentor reticulatus. Occasionally, alien species of ticks transferred to the territory of Poland are recorded: Amblyomma sphenodonti, Amblyomma exornatum, Amblyomma flavomaculatum, Amblyomma latum, Amblyomma nuttalli, Amblyomma quadricavum, Amblyomma transversale, Amblyomma varanensis, Amblyomma spp., Dermacentor marginatus, Hyalomma aegyptium, Hyalomma marginatum, Ixodes eldaricus, Ixodes festai, Rhipicephalus rossicus, Rhipicephalus sanguineus. The most common species of the highest medical and veterinary importance in Poland is invariably Ixodes ricinus. The review also sets out information on the risks of tickborne diseases in recreational areas of large cities in Poland, ticks as the cause of occupational diseases and dangerous species of ticks attacking people outside the Polish borders. Selected problems of the biology of ticks, the spread of alien species transferred on hosts and prevention of tick attacks have also been presented. The Polish studies on ticks are a valuable contribution to global research on the Ixodida.

Spatial variation of tick abundance and seroconversion rates of indigenous cattle to Anaplasma marginale, Babesia bigemina and Theileria parva infections in Uganda

Tick abundance and seroconversion rates of 640 indigenous cattle in a mixed crop-livestock system in Uganda were investigated in a 14 months longitudinal study. Up to 100% of the cattle in Buyimini, Kubo, Nanjeho, Ojilai and Sitengo villages (high tick challenge zone) were consistently infested with Rhipicephalus appendiculatus, whereas on average 50% of the cattle in Bunghaji, Hitunga and Magoje villages (low tick challenge zone) were inconsistently infested. Likewise, up to 50% of the cattle in Buyimini, Kubo, Nanjeho, Ojilai and Sitengo villages were consistently infested with R. (Boophilus) decoloratus ticks, while on average 30% of the cattle in Bunghaji, Hitunga and Magoje were inconsistently infested. Seroconversion rates of cattle to Anaplasma marginale infection under low tick challenge were higher than those under high tick challenge, but the reverse was true for Babesia bigemina infection. For Theileria parva infection, seroconversion rates of cattle older than 6 months under low tick challenge were significantly higher than those under high tick challenge (P < 0.05). However, the likelihood of occurrence of theileriosis cases among calves (0-6 m) under high tick challenge was 6 times (Odds ratio = 5.82 [1.30-36.37]) higher than under low tick challenge. The high density of anti-tick plants Lantana camara and Ocimum suave that were widespread in villages with low tick challenge, among other factors, was probably the cause for unfavourable tick survival.

[Perspectives of creation of vaccines against tick bite for nonspecific prophylaxis of vector borne diseases]

Prophylaxis of infectious diseases transferred by ticks is an important problem of contemporary medicine. One of the perspective approaches to solve this problem is the creation of vaccines against tickbite (anti-tickvaccines). Contemporary methods of the control of infectious diseases transferred by ticks are described in the review. Features of naturally and artificially acquired immunity against ticks are examined. Candidate tick antigens for the construction of vaccines against genus Ixodes tick bite are described. Perspectives of use of anti-tick vaccines against tick vector borne diseases are evaluated.

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.

Modeling transmission dynamics and control of vector-borne neglected tropical diseases

Neglected tropical diseases affect more than one billion people worldwide. The populations most impacted by such diseases are typically the most resource-limited. Mathematical modeling of disease transmission and cost-effectiveness analyses can play a central role in maximizing the utility of limited resources for neglected tropical diseases. We review the contributions that mathematical modeling has made to optimizing intervention strategies of vector-borne neglected diseases. We propose directions forward in the modeling of these diseases, including integrating new knowledge of vector and pathogen ecology, incorporating evolutionary responses to interventions, and expanding the scope of sensitivity analysis in order to achieve robust results.

The Gulf Coast tick: a review of the life history, ecology, distribution, and emergence as an arthropod of medical and veterinary importance

The Gulf Coast tick, Amblyomma maculatum Koch (Acari: Ixodidae), is a unique univoltine ectoparasite of seven vertebrate host classes in the Western Hemisphere that is increasingly recognized as a pest of livestock and wildlife, a vector of pathogens to humans and canines, and a putative vector of Ehrlichia ruminantium, the causal agent of heartwater, a fatal foreign animal disease of ruminants resident in the Caribbean. This review assembles current and historical literature encompassing the biology, ecology, and zoogeography of this tick and provides new assessments of changes in cyclical population distribution, habitat associations, host utilization, seasonal phenology, and life history. These assessments are pertinent to the emergence of A. maculatum as a vector of veterinary and medical importance, and its pest management on livestock and other animals.

An interview with Robert S. Lane, Ph.D. Interviewed by Vicki Glaser

Dr. Robert Lane received a B.A. degree in psychology from the University of California at Berkeley (UCB), an M.A. degree in biology at San Francisco State College, and a Ph.D. in entomology at UCB. While employed as a California State public health biologist he began his long-standing studies of the biology of ticks and the ecology and epidemiology of tick-borne disease agents. In 1984, Dr. Lane joined the faculty of UCB as a medical entomologist, a position he has held until the present. The diseases he and his many co-workers have investigated include Colorado tick fever, human granulocytic anaplasmosis, relapsing fever, Rocky Mountain spotted fever, tularemia, and particularly Lyme disease. Findings from these studies have elucidated the basic transmission cycles of and risk factors for spotted fever-group rickettsiae and Lyme disease spirochetes in the far western United States. Bob is a Fellow of both the California Academy of Sciences and the American Association for the Advancement of Science, a recipient of a UCB Biology Faculty Research Award and the C.W. Woodworth Award from the Pacific Branch of the Entomological Society of America, and a member of the Council for the International Congresses of Entomology. Also, he has served as president of the Acarological Society of America, the International Northwestern Conference on Diseases in Nature Communicable to Man, the Northern California Parasitologists, and the Society for Vector Ecology, as well as the Chair of Section D (Medical/Veterinary Entomology), Entomological Society.

Spread of parasites transported with their hosts: case study of two species of cattle tick

Like all parasites, ticks can be spread easily along with their hosts. Ticks are obligate parasites of vertebrates, to which they attach themselves for varying periods of time, and are well-adapted to this mode of transport. Once the transport stage is complete and they have detached at destination, they are also able to wait several months for the arrival of a new host on which they will continue their life cycle. This leads to the establishment of a secondary tick population. Two tropical cattle tick species, Rhipicephalus microplus and Amblyomma variegatum, have perfected this strategy of colonisation and occupation of favourable zones. Rhipicephalus microplus, which originated from South and Southeast Asia, is highly specific for ungulates, and thanks to cattle movements it has spread throughout the tropical belt, apart from the remotest areas. Amblyomma variegatum, which originated in Africa, was transported to Madagascar and the Mascarene Islands, as well as to the West Indies, during the time of the Atlantic triangular trade. These two ticks are vectors of particularly serious cattle diseases: babesiosis and anaplasmosis in the case of R. microplus, and heartwater (cowdriosis) in the case of A. variegatum. Anticipated climate changes are likely to modify the potential geographical range of these two parasite species and numerous others. Even now there are still many areas of the Americas, Asia and Oceania into which A. variegatum has not yet spread, but which it would find favourable. It could be spread not only by the transport of cattle, but also by the migration of some of its other hosts, such as birds. Surveillance--and know-how--is needed to identify these parasites when they first appear and to rapidly contain new outbreaks. Efforts should be made to raise the awareness of livestock professionals about the risks of transporting cattle. Regulations should be implemented and precautions taken to avoid such artificial expansion of the range of ticks and the diseases they transmit.

[Ticks and transmission of some important diseases by ticks]

Ticks which are commonly found all around the world are ectoparasites which are obliged to suck blood from vertebrates such as mammals and birds during all of their periods of develeopment. They may cause toxicities and paralyses in the course of blood sucking through saliva injection and the attachment sites may become ports of entry for secondary agents. Healthy animals that are severely infested by ticks can show a decreased yield and anemia. Young and sick animals can even die. Besides this, ticks are both biological and mechanical vectors for viruses, bacteria, rickettsias, spirochaetas, protozoons and helminths. Ten percent of the ticks identified in the world are associated with 200 diseases. In this review the taxonomy and morphology of ticks, some of the important diseases they carry and the diagnosis and treatment of these diseases are mentioned.

[Transmission and circulation of tick borne pathogens (TBE and Lyme borreliosis) and the role of changing environment]

Ixodes ricinus is regarded as a species with great medical and veterinary meaning. Transmission of tick borne pathogens in mammals depends not only on systemic infection. Transmission of B. burgdorferi and tick-borne encephalitis virus in an infected organism differs, because of different location in tick, the differences in dissemination of the virus and bacteria (own motility) as well as mechanisms supporting bacterial infection. The mechanisms governing the transmission of these pathogens in nature have epidemiological importance and are essential in understanding the pathogenesis of diseases. The increase in the incidence of tick-borne encephalitis in recent years, is a marker of tick borne diseases. In the 90s, the number of cases among humans in many European countries remains at a higher level compared to the eighties. Similar observations consider to Lyme borreliosis. Natural environmental changes, mainly related to climate, as well as regional and local changes in distribution of the small rodents species, wild animals, anthropogenic factors (reforestation, drainage of swamps, increasing the reservoir of animals), and social change (increased human activities in forests, vaccinations) may have a significant impact on rates of tick-borne diseases.

Endemic tickborne infectious diseases in Louisiana and the Gulf South

Most emerging infectious diseases today, such as West Nile virus and sudden acute respiratory distress syndrome (SARS), arise from zoonotic reservoirs and many are transmitted by arthropod vectors. Ticks are among the most competent and versatile arthropod vectors of infectious diseases because ticks of all ages and both sexes remain infectious for generations without having to reacquire infections from reservoir hosts. Today, ticks transmit the most common arthropod-borne infectious disease in the United States (US), Lyme disease (LD); and the most lethal arthropod-borne infectious disease in the US, Rocky Mountain spotted fever (RMSF). Both LD and RMSF are endemic in Louisiana and the Gulf South. Ticks have also become frequent vectors of emerging zoonotic diseases in the Gulf South, including southern tick-associated rash illness (STARI), transmitted by the lone star tick, and Maculatum disease, transmitted by the Gulf Coast tick. Recent environmental changes and human lifestyle choices now place humans and ticks together outdoors in the Gulf South for longer periods in welcoming ecosystems for breeding, blood-feeding, and infectious disease transmission. An increasing incidence of emerging and re-emerging, endemic infectious diseases transmitted by existing and unanticipated tick vectors may be expected.

[Climate- and vector-borne diseases]

The predicted changes in climate have raised concerns that vector-borne diseases may emerge or expand in tempered regions. Malaria, leishmaniasis and tick-borne illnesses are discussed in terms of climate change and their endemic potential, especially in Denmark. While climate may play an important role in disease patterns, it is evident that transmission potential is governed by a complex of factors, including socio-economy, health-care capacity and ecology. In Denmark, malaria and leishmaniasis are unlikely to become public health problems, whereas the potential for tick-borne illnesses may increase.

[Ecology and epidemiology of tick-borne infections in the Primorsky Krai]

Interrelation of parasitological and epidemiological estimations of potential danger of different territories Primorsky Krai concerning presence of natural foci of tick-borne diseases is discussed. Comparative analysis of long-term dynamics of the tick-borne diseases' sickness rate in comparison with long-term dynamics of the vector ticks' abundance has been carried out.

Tick-borne disease systems: mapping geographic and phylogenetic space

Evidence is presented that the evolution of the tick-borne flaviviruses is driven by biotic factors, principally the exploitation of new hosts as transmission routes. Because vector-borne diseases are limited by climatic conditions, however, abiotic factors have the potential to direct and constrain the evolutionary pathways. This idea is explored by testing the hypothesis that closely related viruses occupy more similar eco-climatic spaces than do more distantly related viruses. A statistical comparison of the conventional phylogenetic tree derived from molecular distances and a novel phenetic tree derived from distances between the climatic spaces within which each virus circulates, indicates that these trees match each other more closely than would be expected at random. This suggests that these viruses are indeed limited in the degree to which they can evolve into new environmental conditions.

The relationship between spotted fever group Rickettsiae and ixodid ticks

Spotted fever group Rickettsiae are predominantly transmitted by ticks. Rickettsiae have developed many strategies to adapt to different environmental conditions, including those within their arthropod vectors and vertebrate hosts. The tick-Rickettsiae relationship has been a point of interest for many researchers, with most studies concentrating on the role of ticks as vectors. Unfortunately, less attention has been directed towards the relationship of Rickettsiae with tick cells, tissues, and organs. This review summarizes our current understanding of the mechanisms involved in the relationship between ticks and Rickettsiae and provides an update on the recent methodological improvements that have allowed for comprehensive studies at the molecular level.

[Effect of coinfections in Ixodidae ticks on transmission of blood microparasites]

The purpose of this review was to describe and discuss the current spectrum of coinfections in Ixodidae ticks and their effects on the transmission of blood microparasites. Coinfections with Borrelia burgdorferi s. l. and Anaplasma phagocytophilum and/or Babesia sp. in ticks from Poland appear to be common, however, the potential influence on transmission dynamics, the mechanism of genetic variation and the ecology of interactions between pathogens remain poorly understood compared with infections by single pathogen.

Potential effects of mixed infections in ticks on transmission dynamics of pathogens: comparative analysis of published records

Ticks are often infected with more than one pathogen, and several field surveys have documented nonrandom levels of coinfection. Levels of coinfection by pathogens in four tick species were analyzed using published infection data. Coinfection patterns of pathogens in field-collected ticks include numerous cases of higher or lower levels of coinfection than would be expected due to chance alone, but the vast majority of these cases can be explained on the basis of vertebrate host associations of the pathogens, without invoking interactions between pathogens within ticks. Nevertheless, some studies have demonstrated antagonistic interactions, and some have suggested potential mutualisms, between pathogens in ticks. Negative or positive interactions between pathogens within ticks can affect pathogen prevalence, and thus transmission patterns. Probabilistic projections suggest that the effect on transmission depends on initial conditions. When the number of tick bites is relatively low (e.g., for ticks biting humans) changes in prevalence in ticks are predicted to have a commensurate effects on pathogen transmission. In contrast, when the number of tick bites is high (e.g., for wild animal hosts) changes in pathogen prevalence in ticks have relatively little effect on levels of transmission to reservoir hosts, and thus on natural transmission cycles.

Tularemia

Tularemia is a rare zoonotic infection caused by the bacterium Francisella tularensis. The disease is endemic in North America and parts of Europe and Asia. Arthropods (ticks and deer flies) are the main transmission vector, and small animals (rabbits, hares, and muskrats) serve as reservoir hosts. The clinical presentation depends on the bacterial subspecies and the route of infection. Recent world events have led to a new recognition of F tularensis as a viable agent of bioterrorism, which has sparked a renewed focus on this pathogen.

Tick-borne pathogens and diseases of animals and humans in Thailand

Tick-borne pathogens in Thailand can cause diseases that result in productivity and economic losses in the livestock sector as well as cause debilitating illnesses in humans and their companion animals. With the advent of molecular techniques, accurate identification of tick-borne pathogens and precise diagnosis of disease is now available. This literature review summarizes the various tick-borne pathogens that have been isolated from ticks and their vertebrate hosts in Thailand, covering those protozoa, rickettsiae, bacteria and viruses most responsible for human and veterinary disease with particular emphasis on those that have been characterized molecularly.

[Study on the relation of transmission of Lyme disease and ecological protection from western regions in China]

OBJECTIVE

To find out the relationship of ecological environment protection and the transmission of Lyme disease under economic development of western regions in China.

METHODS

Both scene molecular and traditional epidemiological methods were used to assess the effects of environmental protection on the transmission of Lyme disease.

RESULTS

Among areas as protected natural forests, semi-protected nursery forests and farmland, the vector tick species and reservoir rodents from protected natural forests area had the highest quantity of population and diversity index and followed by semi-protected nursery forests. Vector competence of reservoir hosts and value of natural foci from protected natural forests area were also remarkably higher than those areas of semi-protected nursery forests and farmland. Staff working in the areas who were bitten by ticks from protected natural forests areas had higher serological positive rate (66.7%) than those from semi-protected nursery forests areas (2.5%), and both showed remarkable difference (P = 6.45, E-11 < 0.01, df = 1). The difference of genetic divergence among these subpopulations from different habitats being surveyed showed that the biggest genetic divergence index (F(st)) of 0.557 42 was between protected natural forests area and farmland area. The index between semi-protected nursery forests area and farmland area was also bigger than zero with statistical significance. The genetic divergence index of 0.108 02 between semi-protected nursery forests area and protected natural forests area was the lowest which showed that genetic divergence between the subpopulations of the two sampling areas was not obvious. The genetic distance among these subpopulations had similar change along with their habitats.

CONCLUSION

Under economic development of western regions in China, when programs as natural forests protections, recovery prairie and grassland from farmland were actively performed, vectors insects and reservoir hosts of Lyme disease might also be protected to some degree but the risk and value of natural foci on Lyme disease might increase. Data suggested that people entering these areas should be told to strengthen their awareness on individual protection against the disease.

Infection and co-infection rates of Anaplasma phagocytophilum variants, Babesia spp., Borrelia burgdorferi, and the rickettsial endosymbiont in Ixodes scapularis (Acari: Ixodidae) from sites in Indiana, Maine, Pennsylvania, and Wisconsin

In total, 394 questing adult blacklegged ticks, Ixodes scapularis Say (Acari: Ixodidae), collected at four sites were analyzed by polymerase chain reaction (PCR) for five microbial species: Anaplasma phagocytophilum, Babesia microti, Babesia odocoilei, Borrelia burgdorferi, and the rickettsial I. scapularis endosymbiont. Identities of genetic variants of A. phagocytophilum were determined by sequencing a portion of the 16S DNA. In 55% of infected ticks (193/351), a single agent was detected. In 45% (158/351), two or more agents were detected; 37% harbored two agents and 8% harbored three agents. One male tick, collected from Ft. McCoy, WI, harbored all four microbial genera The highest rates of co-infection were by the Ixodes endosymbiont and B. burgdorferi (95/351). Two species of Babesia co-occurred within a single tick population in Wells National Estuarine Research Reserve, Wells, ME, whereas only B. odocoilei was found in other tick populations. Only A. phagocytophilum human anaplasmosis variant was detected in questing ticks from Tippecanoe River State Park, IN; from Wells; and Ft. McCoy, whereas a single infected tick from Presque Isle, PA, was infected by AP-Variant 1. Partially engorged ticks from deer in Tippecanoe River State Park were all infected with AP-Variant 1. Frequency of infections with each agent varied among populations. Rates and types of co-infections were not significantly different from random except for the Ixodes endosymbiont and B. burgdorferi in male ticks, which co-occurred less frequently than expected. Thus, I. scapularis hosts an array of pathogenic and symbiotic agents and potential evidence of interactions among microbial species was observed.

Man-threatening viruses isolated from ticks in Saudi Arabia

OBJECTIVE

To determine tick viruses transmissible to man in Saudi Arabia.

METHODS

We collected tick samples for identification from different region of Saudi Arabia during March 1992 - December 1992. Ticks collected from domestic animals were washed with buffer containing antibiotics, macerated, triturated in minimal essential media (MEM), centrifuged and the supernatant inoculated intracerebrally in suckling mice. Brains of mice showing disease signs were similarly treated and the supernatant inoculated on cell cultures. Antigen spot slides were prepared from material of blind-passed cell cultures showing cytopathic effects. The slides were overlaid by group-specific hyperimmune mouse ascetic fluid (HMAF) to different virus groups and stained with antimouse fluorescein isothiocyanate conjugate. Positive slides were retested with monoclonal antibodies or HMAF to individual viruses within the positive group.

RESULTS

Sindbis virus was isolated from Hyalomma dromedarii (H. dromedarii) from Al-Qasim and Jazan regions and Hyalomma impeltatum (H. impeltatum) from Al-Qasim, Ar-Riyadh and Jazan regions. Chick Ross and Kadam viruses were isolated from H. dromedarii from Al-Qasim region. Kadam virus was isolated from Hyalomma anatolicum (H. anatolicum) from Ar-Riyadh region. Dhori virus was isolated from H. impeltatum and Hyalomma schulzei (H. schulzei) from the Eastern region. Other alphaviruses were isolated from H. dromedarii from Al-Qasim and Tabuk regions, H. impeltatum from Jazan region, H. anatolicum from the Eastern region and Rhipicephalus sanguineus from Ar-Riyadh and Eastern regions.

CONCLUSION

In the Kingdom, ticks harbor viral infections transmissible from wildlife to man and his livestock. Local physicians should be aware of the symptoms and signs of these infections.

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.

Passive surveillance in Maine, an area emergent for tick-borne diseases

In 1989, a free-of-charge, statewide tick identification program was initiated in Maine, 1 yr after the first Ixodes scapularis Say (=I. dammini Spielman, Clifford, Piesman & Corwin) ticks were reported in the state. This article summarizes data from 18 continuous years of tick submissions during which >24,000 ticks of 14 species were identified. Data provided include tick stage, degree of engorgement, seasonal abundance, geographical location, host, and age of the person from whom the tick was removed. Maps depict the distributions of the three major species submitted. I. scapularis emerged first along the coast, and then it advanced inland up major river valleys, Dermacentor variabilis Say slowly expanded centrifugally from where it was initially reported in southwestern Maine, and the distribution of long-established Ixodes cookei Packard remained unchanged. Submissions of nymphal I. scapularis closely correlated with reported Lyme diseases cases at the county level. Annual fluctuations of nymphal submissions in Maine correlated with those of Lyme disease cases for New England, supporting the possibility of a regional influence on tick abundance. More ticks were removed from people < or =14 and > or =30 yr of age, and their degree of engorgement was greatest in people < or =20 yr of age and progressively increased in people > or =30 yr of age. This study demonstrates the usefulness and potential of tick identification programs.

Optimal control on hybrid ode systems with application to a tick disease model

We are considering an optimal control problem for a type of hybrid system involving ordinary differential equations and a discrete time feature. One state variable has dynamics in only one season of the year and has a jump condition to obtain the initial condition for that corresponding season in the next year. The other state variable has continuous dynamics. Given a general objective functional, existence, necessary conditions and uniqueness for an optimal control are established. We apply our approach to a tick-transmitted disease model with age structure in which the tick dynamics changes seasonally while hosts have continuous dynamics. The goal is to maximize disease-free ticks and minimize infected ticks through an optimal control strategy of treatment with acaricide. Numerical examples are given to illustrate the results.

Global stability of equilibria in a tick-borne disease model

In this short note we establish global stability results for a four- dimensional nonlinear system that was developed in modeling a tick-borne disease by H.D. Gaff and L.J. Gross (Bull. Math. Biol., 69 (2007), 265-288) where local stability results were obtained. These results provide the parameter ranges for controlling long-term population and disease dynamics.

Detection of Rickettsia africae in Rhipicephalus (Boophilus) decoloratus ticks from the Republic of Botswana, South Africa

A total of 53 engorged adult ticks belonging to the species Rhipicephalus (Boophilus) decoloratus (N = 9), Rhipicephalus evertsi evertsi (N = 27), Rhipicephalus appendiculatus (N = 9), Amblyomma hebraeum (N = 5), and Hyalomma marginatum turanicum (N = 3), were removed from oryx in Botswana (South Africa). They were tested for the presence of spotted fever group (SFG) Rickettsia and Anaplasma phagocytophilum using polymerase chain reaction (PCR). Seventy-seven percent of R. decoloratus as well as twenty percent of A. hebraeum were positive for ompA, gltA and 16S rRNA SFG Rickettsia PCR assays. All nucleotide sequences were homologous to Rickettsia africae, the agent of African tick-bite fever (ATBF). None of the tested ticks was positive for 16S rRNA A. phagocytophilum PCR assays. These results suggest for the first time that R. decoloratus ticks may be reservoirs of R. africae, and support the ATBF risk in this area.

In vitro feeding assays for hard ticks

Prevention of tick bites and transmission of tick-borne pathogens requires the use of molecules that target physiological processes crucial to both tick and pathogen survival. These molecules are best tested in standardized in vitro assays. Because hard ticks require several days to feed to repletion, the development of in vitro feeding assays for these species is challenging. A standard and easily automated feeding assay has been developed for the tick Ixodes ricinus that involves feeding on blood through a membrane that mimics the elasticity of skin. The system can be adapted to feed other hard tick species in vitro. This assay permits, among others, investigations on the role of tick endosymbionts on tick survival, the identification of potential vaccine candidates and drugs, and the application of genomic tools in vitro, including RNA interference experiments.

Tick cell lines: tools for tick and tick-borne disease research

Over 40 cell lines are currently available from 13 ixodid and one argasid tick species. The successful isolation and propagation of several economically important tick-borne pathogens in tick cell lines has created a useful model to study interactions between tick cells and these viral and bacterial disease agents. Tick cell lines have already proved to be a useful tool in helping to define the complex nature of the host-vector-pathogen relationship. With the availability of genomics tools, tick cell lines will become increasingly important as a complement to tick and tick-borne disease research in vivo once genetic transformation and gene silencing using RNA interference become routine.

Upcoming and future strategies of tick control: a review

Ticks are distributed worldwide and significantly impact human and animal health. Due to severe problems associated with the continuous use of acaricides on animals, integrated tick management is recommended. Increasing public health concern over the tick-borne diseases demands the strategic control of ticks on animals that transmit diseases to human beings. Immunological control of tick vector of Kyasanur Forest Disease (KFD) on cattle and other wild reservoir hosts is one of the possible alternative strategy for reducing the transmission of KFD to man. Chemical-vaccine synergies have been demonstrated and a combination of chemical and vaccine for tick and tick-borne disease control has been identified as a sustainable option. Studies have suggested the possibility of vaccine strategies directed towards both tick control and transmission of pathogens. Besides tick vaccine, use of endosymbionts, which are essential for the survival of arthropod hosts, for the control of tick vectors will be one of the targeted areas of research in near future. India with huge natural resources of herbs and other medicinal plants, the possibilities of developing herbal acaricides is discussed. The future of research directed towards target identification is exciting because of new and emerging technologies for gene discovery and vaccine formulation.