Molecular differentiation of metastriate tick immatures

Hard ticks, family Ixodidae, are divided into two groups, the Metastriata and the Prostriata, based on morphological differences. In the United States, there are four medically important genera of the Ixodidae: Ixodes, Amblyomma, Dermacentor, and Rhipicephalus. Ixodes is the only genus in and representative of the Prostriata, whereas the latter three genera are members of the Metastriata. All developmental stages of the Prostriata can be easily differentiated from the Metastriata using morphology. Similarly, the three Metastriate genera are highly identifiable as adults, yet as immatures, the discriminating characteristics can be difficult to use for differentiation, especially if the specimens are damaged or engorged with blood. All three Metastriate genera represent medically important vectors, thus accurate differentiation is necessary. To this end, we have developed a multiplexed-PCR diagnostic assay that, when combined with RFLP analysis will differentiate between the Metastriate genera--Amblyomma, Dermacentor, Rhipicephalus, and Haemaphysalis based on the length of the PCR amplicon and subsequent restriction digestion profile. The intended use for this diagnostic is to verify morphological identifications, especially of immatures, as well as to identify samples destroyed for molecular analysis, which will lead to more accurate field data as well as implication of vectors in disease transmission.

[Ticks (Acarina: Ixodidae) as vectors and reservoirs of pathogen microorganisms in Spain]

Hard and soft-ticks are obligate haematophagous arachnids of medical and veterinary significance mainly because of the animal disease agents transmitted by them, which include an array of different pathogens (virus, bacteria, protozoa and nematodes). Ticks transmit microbes by several routes including salivary secretions, coxal fluids, regurgitation and faeces. Among the biological factors that contribute to the high vector potential of ticks are their living habits and characteristic properties of their saliva secretions and blood digestion. In the Iberian Peninsula, the prostriata tick Ixodes ricinus, and the metastriata Dermacentor marginatus, Rhipicephalus sanguineus and Hyalomma marginatum are the main species that could bite man, and are involved in the transmission of Borrelia burgdorferi sensu lato, several genoespecies of Rickettsia (R. conorii, R. slovaca, R. aeschlimannii) and Anaplasma phagocytophila.

Lyme borreliosis in Europe and North America

Since the discovery of the Lyme disease spirochete in North America in 1982 and in Europe in 1983, a plethora of studies on this unique group of spirochetes that compriseBorrelia burgdorferisensu lato has been accumulated. In an attempt to compare and contrast Lyme borreliosis in Europe and North America we have reviewed the biology of the aetiologic agents, as well as the clinical aspects, diagnosis and treatment of this disease on both continents. Moreover, we have detailed the ecology of theIxodesticks that transmit this infection and the reservoir hosts that maintain the spirochete cycle in nature. Finally, we have examined the transmission dynamics of the spirochete on both continents, as well as the available prevention strategies. Although it has been over two decades since the discovery of the Lyme disease spirochete, Lyme borreliosis is an expanding public health problem that has defied our attempts to control it. By comparing the accumulated experience of investigators in North America and Europe, where the disease is most frequently reported, we hope to advance the cause of developing novel approaches to combat Lyme borreliosis.

[ELISA and RT-PCR-based research of viruses in the ticks collected in the foci of Crimean-Congo fever in Kazakhstan and Tajikistan in 2001-2002]

Different species of ticks were found, in the territories of Kazakhstan and Tajikistan, to be infected with the virus of Crimean-Congo hemorrhagic fever (CKHF). The virologic evaluation included determination of antigen and RNA of the CKHF virus by ELISA and RT-PCR, respectively. The below tick species were found to be involved in the epidemic process: Hyalomma asiaticum, Dermacentor niveus (Kazakhastan) and Hyalomma anatolicum (Tajikistan). The results testify to the fact that Hyalomma ticks are the main carrier of the above virus in the Middle Asia. At the same time, Dermacentor niveus ticks are infection carriers in Kazakhstan.

Biology and control of ticks infesting dogs and cats in North America

At least 15 different infectious agents and diseases are transmitted or produced by ticks parasitizing dogs and cats in North America. Those infectious agents and diseases are distributed among eight different tick species that commonly infest dogs and cats. All but one of these species are hard ticks with a three-host development cycle in which each motile stage (larva, nymph, and adult) feeds on a different host after molting. Tick species, disease occurrence, and peak activity of each tick life stage can vary dramatically depending on geographic and climatic conditions. Gaining an understanding of tick distribution, tick ecology, and seasonal occurrence of different tick life stages can help with the management of tick infestations and reduce the incidence of tick-transmitted diseases in dogs and cats. Control should be based on an understanding and management of ecologic factors responsible for tick infestations and selection of appropriate acaricides. Occasionally, topical acaricides will appear not to have prevented tick infestations. This lack of control may be real or perceived based on reinfestation rates and/or pet owner expectations of product performance.

A study about tick vectors of bovine theileriosis in an endemic region of Iran

The aim of this study was to determine the population of ticks in infected cattle and to identify the tick vectors of bovine theileriosis in an endemic area of Iran from 1998 to 1999. A total of 120 suspected cattle suffering from theileriosis were clinically examined and investigated for the presence of Theileria annulata in blood smears and the presence of any tick species on the body of cattle. In this study, 680 ticks were collected from 107 cattle infected with T. annulata. The prevalence of ticks infesting cattle was 92.35% Hyalomma anatolicum excavatum, 5.14% H. marginatum marginatum, 1.17% H. asiaticum asiaticum and 1.32% Rhipicephalus sanguineus. The examination of 510 tick salivary glands revealed that 51% of H. a. excavatum and 1.3% of H. a. asiaticum were infected with sporozoites of T. annulata.

Aponomma hydrosauri, the reptile-associated tick reservoir of Rickettsia honei on Flinders Island, Australia

Rickettsia honei is the etiologic agent of Flinders Island (Australia) spotted fever. The tick Aponomma hydrosauri is associated with reptiles and is the arthropod reservoir for this rickettsia on Flinders Island. The rickettsia appears to be maintained in the tick via vertical transmission. Of 46 ticks examined, 29 (63%) were positive for spotted fever group rickettsiae by detection of the citrate synthase gene by a polymerase chain reaction (PCR). From the positive tick samples, seven were sequenced and found to be 100% homologous with R. honei. Of 17 reptiles examined, none had evidence of rickettsiae by PCR or culture of blood.

Coinoculation of Borrelia spp. with tick salivary gland lysate enhances spirochete load in mice and is tick species-specific

C3H/HeN mice were inoculated with 10(6) spirochetes, either Borrelia burgdorferi strain N40 or the Portuguese strain of B. lusitaniae, PotiB2. Mice receiving spirochetes coinoculated with salivary gland lysate (SGL) demonstrated significantly higher spirochete loads in target organs as measured by quantitative real-time polymerase chain reaction. This effect was tick dependent, in that Ixodes ricinus SGL specifically enhanced B. lusitaniae load, whereas I. scapularis SGL specifically increased B. burgdorferi N40 load, but did not significantly affect the dissemination of B. lusitaniae. Protein profile analysis indicated at least 5 major protein differences between I. scapularis and I. ricinus SGL, which can possibly account for this specific tick-spirochete interaction.

Introduction of potential heartwater vectors and other exotic ticks into Florida on imported reptiles

Following the discovery of establishment of the African tortoise tick Amblyomma marmoreum in Florida, the present study was undertaken to determine the extent of introduction of exotic ticks into Florida on imported reptiles. Exotic ticks were identified on 29 (91%) of 32 reptile premises in 18 counties of Florida. The ticks, found on a variety of imported tortoises, snakes, and monitor lizards, belonged to 4 Amblyomma species (A. marmoreum, Amblyomma nuttalli, Amblyomma sabanerae, and Amblyomma sparsum) and 4 Aponomma species (Aponomma exornatum, Aponomma flavomaculatum, Aponomma latum, and Aponomma varanensis). The most commonly encountered ticks were A. latum and A. marmoreum. The identifications of A. marmoreum on 8 premises in 7 counties, and of A. sparsum on 1 premises, are of great concern because both species are vectors of heartwater, a lethal disease of cattle, sheep, goats, and deer.

[Ehrlichiosis in Switzerland--significance for veterinary medicine]

Ehrlichiosis is a rickettsial disease of animals and humans caused by various species of Ehrlichia. These obligate intracellular microorganisms infect granulocytes or monocytes of mammalian hosts and are transmitted mostly by ticks. The febrile disease is often undiagnosed and characterized by leukopenia, anemia and thrombocytopenia. The diagnosis of ehrlichiosis is based on clinical findings, tick infestation, direct or indirect detection of the agent, and serology. The role of native and imported ehrlichiae of animals in Switzerland is discussed.

Lyme disease

Lyme borreliosis, the most common vector-borne disease in the northern hemisphere, is caused by bacteria belonging to the Borrelia burgdorferi complex. The disease is multisystemic, affecting mainly the skin, nervous system, heart and joints. In Europe, the vector of the disease is the tick Ixodes ricinus, whereas in the United States of America, two primary tick vectors exist, namely: I. scapularis in the north-eastern and mid-western regions and I. pacificus on the west coast. Several species of small and medium-sized mammals and ground-feeding birds serve as reservoirs for the bacteria in endemic areas. The prognosis for patients with Lyme borreliosis is excellent, particularly when diagnosed and treated early in the course of infection. Prevention of Lyme borreliosis can be achieved using two approaches, either prevention of infection by immunisation, or prevention of tick bites through avoidance, personal protection and tick control.

[The intraspecific taxonomic structure and identification of closely related species of ixodid ticks (Ixodidae)]

Two variants of intraspecific morphological differentiation of 7 palearctic species of Ixodidae and respectively two variants of their intraspecific taxonomic pattern have been revealed on the basis of the study of geographic variation of each species. Three species--Ixodes pavlovskyi Pom., 1946, Haemaphysalis erinacei Pavesi, 1884, Hyalomma asiaticum Sch. et Schl., 1929, are subdivided into subspecies, and four ones--I. ricinus (L., 1758), I. persulcatus Sch., 1930, I. crenulatus Koch, 1844, Dermacentor marginatus (Sulzer, 1776),--into morphotypes by the degree of distinction of the whole complex of active stages in ontogenesis. Acknowledging the conventional character of the categories of subspecies and morphotype their criteria have been formulated for ixodid ticks. Paleogeographic and ecological grounds are given. Some data of geographic variation of immature stages favour the identification of closely related species in concrete localities.

Molecular phylogenetic analysis of ixodid ticks based on the ribosomal DNA spacer, internal transcribed spacer 2, sequences

An internal transcribed spacer (ITS2) sequence between the 5.8S and 28S rRNA genes was used to estimate the phyletic relationships among Ixodes spp. tick vectors of Lyme disease-causing Borrelia spirochetes. Analysis indicates that Borrelia burgdorferi sensu lato species associated with Lyme disease are found mainly in ticks of the Ixodes ricinus species complex. Other closely related tick species are not known to transmit the Borrelia-that cause Lyme disease in humans, but they appear to have a specific association with other closely related Borrelia species. There is a high degree of concordance in the phylogenetics of Borrelia taxa and the phylogenetic relationships among Ixodes ticks.

[The sympatry of closely related species of ixodid ticks and its possible role in the parasitic systems of natural foci of transmissible diseases]

Sympatry of the following pairs (or groups) of closely related species in the territory of the former Soviet Union amd some neighbouring countries has been revealed as a result of a revision of the fam. Ixodidae: I. persulcatus-I. ricinus, I. persulcatus-I. pavlovskyi, I. crenulatus-I. kaiseri, Dermacentor marginatus-D. silvarum-D. ushakovae, D. ushakovae-D. niveus, D. pavlovskyi-D. montanus, Rhipicephalus turanicus-R. sanguineus, R. turanicus-R. rossicus, R. turanicus-R. pumilio, R. rossicus-R. pumilio. Biotope and host relationships of sympatric species, as well as seasons of parasitizing have been described on the basis of the field researches conducted by the author, the collections of the Zoological Institute, Russian Academy of Sciences, and the publications substantiated by collection materials studied by the author. Hypothetic ways of the paleogenesis of each sympatric area and geological age have been considered. The recent sympatric area for I. persulcatus-I. ricinus (fig. 1) is of Holocene age (max. 8.000-10.000 years). During that period approximately 1600-2000 sympatric generations could have been realized. Some recent sympatric areas (I. persulcatus-I. pavlovskyi, and some species of other genera) are of Pleistocene and even Pliocene age (2-10 million years). In these areas the number of realized sympatric generations must have been much higher. Several variants of joint simultaneous and successive feeding on one and the same host individual have been established for stages of life cycles of sympatric species of ticks. Contacts of this kind could have created canals for multiple oscillatory exchange of pathogenic taxa (species, genospecies, strains) in a few or many thousands of sympatric generations of closely related vectors. Thus, the same taxon of a pathogen may be subject to different influence of ixodid vectors in sympatric area and in the area of separate habitat of close species of vectors.

[Enzootic reservoir for new Ixodes ricinus-transmitted infections]

In the last decade new tick-transmitted zoonoses have emerged as threats to the public health in Europe. They are mostly due to infection by Borrelia burgdorferi s.I., Babesia divergens, B. microti and Ehrlichia sp. All these pathogens are transmitted by the rodent-feeding ticks of Ixodes persulcatus "complex". Also there is first serological information of coexistence of antibodies to B. burgdorferi, B. microti and Ehrlichia sp. in human exposured to these multiple tick-transmitted pathogens. Actually in Poland, the identification of the host species that act as zoonotical reservoir for these pathogens on which the competent vector becomes infected, is crucial to understand the dynamics of enzootic cycle of these pathogens. It is also important to assess the risk factor of infection in different habitats, especially in environmental condition where changing in farming system has left great land area under grassland or pasture, e.g. in Mazury Lakes District. Under such circumstances, susceptible rodent species, at least for two of these pathogens: B. micrnti and B. burgdorfeń s.l., increasingly became competent reservoirs. This aspect is currently receiving considerable attention in Europe.

Protozoal parasites in tick species infesting camels in Sinai Peninsula

A faunistic survey of ticks infesting camels was carried out in 7 localities of Sinai; El-Arish, Beer El Abd, Nakhel, Ain Mousa, St. Catherine, Wadi Hadra, and Dahab. The protozoal organisms present in the gut and haemolymph of the collected tick species were investigated. Results revealed the presence of six species of tick infesting camels, Hyalomma dromedarii, H. impeltatum, H. an. excavatum, H. an. anatolicum, H. marginatum and H. schulzei. The first 3 species were most common, whereas the latter 3 species were found in certain limited localities. Babesia sp. and Theilera sp. were recorded in both tick guts and haemolymph in most species allover the studied areas. Trypanosoma sp. was recorded in the guts of ticks collected from Beer El Abd, Nakhel and Dahab. Anaplasma sp. was found in tick guts from Beer El Abd and Dahab, however the same organism was detected in the haemolymph of ticks collected in Nakhel and Dahab.

Isolation of Theileria taurotragi and Theileria mutans from cattle in Botswana

Two Theileria species demonstrated in peripheral Giemsa-stained blood smears of sick cattle from various parts of Botswana were subsequently identified as Theileria mutans and T. taurotragi using DNA hybridization and the polymerase chain reaction. Initial screening for Theileria species was done using microscopy, the indirect fluorescent antibody technique and the micro Elisa test. The syndrome was characteristically that of high morbidity but low mortality and vague malaise. A low parasitaemia of pleomorphic intra-erythrocytic piroplasms and the absence of schizont stages in circulating lymphocytes and lymph node aspirates were evident. Dual infections were common and often complicated by intercurrent disease conditions.

Lyme disease spirochetes in ticks from northeastern China

During May 1996, field surveys on Lyme disease spirochetes were conducted in Beijing, Shenyang, Fushun, and Inner Mongolia in northeastern China. The ticks collected consisted of 3 genera and 12 species. Of these, Ixodes persulcatus was dominant in sun-exposed vegetation in forests in Inner Mongolia; 57 Borrelia strains (55/123 unfed adults and 2/5 immature stages fed on a rodent) were obtained from this tick by BSK culture. Additionally, 2/2 Apodemus peninsulae were positive. Ixodes nipponensis, Ixodes pavlovskyi, Haemaphysalis douglasi, and Haemaphysalis megaspinosa, newly recorded in China, and other Haemaphysalis spp. were all negative for Borrelia. Based on a polymerase chain reaction restriction fragment length polymorphism analysis of the 45 strains successfully subcultured, these were classified as 29 Borrelia garinii and 16 Borrelia afelii. These strains seemed to be more closely related to Japanese strains in genetic features than to those from Europe. The result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested more diversity in both genospecies, but Borrelia burgdorferi sensu stricto was not found.

Searching for Lyme disease in Colombia: a preliminary study on the vector

Lyme disease is an infectious multisystemic illness with dermatologic, neurologic, cardiac, and rheumatic manifestations. A total of 4,355 ticks was collected in Colombia, of which 2,805 were identified as Ixodes spp. The midgut contents of 2,600 specimens were fixed on microscope slides and examined by an indirect immunofluorescence assay (IFA) using monoclonal antibodies, anti-ospA H5332, and anti-flagellin 9724. All of the ticks examined by IFA tested negative.

Ixodid ticks infesting rodents and sheep in diverse biotopes of southern India

A total of 127 rodents were trapped in southern India. Examination of these rodents revealed the presence of 2 species of ticks, Haemaphysalis spinigera and Rhipicephalus ramachandrai. The former species is the principal vector of Kyasanur Forest Disease (KFD) in India, and the latter's role, if any, is unknown. Sheep grazing in 1 of the study area were infested with another ixodid tick. Haemaphysalis intermedia, which is a vector of Bhanja virus in India. The presence of H. spinigera on domestic rats is important from the standpoint of KFD enzootiology. This tick shows a narrow habitat preference but a wide host range. In peridomestic situations, the field rodent Bandicota bengalensis did not harbor any tick species. Contiguity of feral and domestic biotopes in some areas contributed to the transfer of R. ramachandrai from its preferred wild rodent host, Tatera indica, to domestic rats Rattus sp.

Sheep and goat tick management

Tick and tick-borne disease (TBD) problems of sheep and goats are less well studied than those of cattle. Nevertheless, small ruminants are able to acquire worthwhile resistance to most tick species and the principles of enzootic stability and the need to preserve it are similar to those with cattle. In practice, sheep and goats are often grazed nomadically and initial TBD infections may be delayed. This may well account for losses from Nairobi sheep disease and heartwater. Sheep and goats are also affected by direct tick damage including tick bite abscesses, tick paralysis, tick-induced dermatophilosis, etc. Otherwise direct damage is believed to be only slight and stress from dipping causes reductions in liveweight gain greater than those caused by the ticks. Even "pour-on" preparations produce no economic benefit in studied situations despite the lack of stress. A pragmatic approach to tick management is needed for varying situations although the need to preserve enzootic stability is of paramount importance.

Ticks and tick-borne diseases as a constraint to sheep and goat production in Italy. Selected features

The paper reviews basic information on small ruminant production in Italy and on the tick species commonly found on them. A total of 13 Ixodidae species have been reported to parasitise sheep in the country. The tick species were belonging to five genera: Ixodes (two species), Haemaphysalis (four species), Dermacentor (one species), Rhipicephalus (three species) and Hyalomma (three species). The same species, with the exception of Haemaphysalis inermis and Hyalomma detritum have been reported also on goats. Scarse data are available on the impact of tick borne diseases on small ruminants productivity. The zoonotic role which may be played by ticks in transmitting occupationally acquired diseases to people involved in animal husbandry and to common public which may accidentally invade grazing areas is also discussed.

Tick-borne diseases of sheep and goats and their related vectors in Iran

Haemoparasitic diseases have long been considered as a major problem to efficient sheep and goats production in Iran. Theileriosis due to Theileria hirci and babesiosis due to Babesia ovis and B. motasi are the most pathogenic protozoa. B. crassa, Anaplasma ovis and Eperythrozoon ovis are usually non-pathogenic and do not cause any apparent problem. The major tick genera found on sheep and goats are Hyalomma, Rhipicephalus, Haemaphysalis, Ixodes and rarely Dermacentor distributed in all part of Iran. Our studies indicate that only Hyalomma ticks transmit Theileria species but the others transmit Babesia, Anaplasma and Eperythrozoon. The two latter ones can also be transmitted through some biting flies and mechanical means. Control methods presently available in Iran rely almost entirely on: (i) vaccination of sheep and goats with cell culture vaccine for theileriosis; (ii) chemotherapeutic treatment for babesiosis and anaplasmosis; (iii) acaricides for control of tick vectors.

Epidemiological aspects of the Brazilian spotted fever: seasonal activity of ticks collected in an endemic area in São Paulo, Brazil

Ticks were collected from vegetation and animals at monthly intervals during one year (1993-1994) in an endemic area of Brazilian spotted fever in the Country of Pedreira, State of São Paulo. Six species of ticks were identified Amblyomma cajennense, Amblyomma cooperi, Amblyomma triste, Anocentor nitens, Rhipicephalus sanguineus and Boophilus microplus. Only the first species was sufficiently numerous to permit a quantitative study with seasonal activity, although the distribution and source of capture of other species were observed and are reported. This information is correlated with the epidemiology of tick-borne rickettsiosis.

Cattle infestation by Hyalomma ticks and prevalence of Theileria in H. detritum species in Tunisia

Seventy-four cattle, from three farms endemic for tropical theileriosis in the north of Tunisia, were studied for tick populations from June 1991 to June 1992. Ticks were removed from cattle twice a month in the summer and every month the rest of the year. They were identified and assessed for Theileria infection. A total of 5083 Hyalomma adult ticks were collected and the major species found was H. detritum (84.3%). The activity of this species is limited between June and August with a peak in numbers observed at the end of June and the beginning of July. Amongst the 2356 Hyalomma ticks dissected, no evidence of salivary gland infection was found in either H. m. marginatum or H. a. excavatum. However, 12.4% (277/2230) of H. d. detritum dissected ticks were infected with Theileria species and amongst these, 62% had one to two sporoblasts in their salivary glands (range 1-91). The prevalence, but not the intensity, of infection was greater in females than in male ticks, and the cases of tropical theileriosis followed the peak of infected females. This suggests that female ticks have a more important role in theileriosis transmission than male ticks. A significantly lower number of adult H. detritum were collected from calves, at their first tick season, than from adult cattle. Finally, this study showed that the infestation level of cattle by H. d. detritum and the prevalence of Theileria-infection in these cattle varied between the three farms studied.

[Argas and arbovirus update]

At the opportunity of the recent discovery of a new Phlebovirus, Tunis virus, the authors discuss the importance of the genus Argas as for its potential role in the transmission of arboviruses: twelve species of Argas are known to carry about twenty viruses. The wide distribution of Argas reflexes hermanni prompt us to explain its position in the Argas reflexes "complex" group: this species seems to be more liable to infection by viruses. Some ecological and entomological data are added to facilitate its typing. The Tunisian specimens recollected are remarkable by the lack of seta n degree 5 on basis capituli.

Ticks and control methods

Ticks are the most important ectoparasites of livestock in tropical and sub-tropical areas, and are responsible for severe economic losses both through the direct effects of blood sucking and indirectly as vectors of pathogens and toxins. Feeding by large numbers of ticks causes reduction in live weight gain and anaemia among domestic animals, while tick bites also reduce the quality of hides. However, the major losses caused by ticks are due to the ability to transmit protozoan, rickettsial and viral diseases of livestock, which are of great economic importance world-wide. The authors review general aspects of tick biology, the taxonomy, pathogenic effects and vector role of these species, and methods for the control of ticks. The distribution of ticks is continuously changing, as illustrated by the spread of the African tick Amblyomma variegatum in the Caribbean, where a large-scale eradication campaign is now under way.

Lyme disease: a search for a causative agent in ticks in south-eastern Australia

Attempts were made to identify the causative organism of Lyme disease in Australia from possible tick vectors. Ticks were collected in coastal areas of New South Wales, Australia, from localities associated with putative human infections. The ticks were dissected; a portion of the gut contents was examined for spirochaetes by microscopy, the remaining portion inoculated into culture media. The detection of spirochaetes in culture was performed using microscopy, and immunochemical and molecular (PCR) techniques. Additionally, whole ticks were tested with PCR for spirochaetes. From 1990 to 1992, approximately 12,000 ticks were processed for spirochaetes. No evidence of Borrelia burgdorferi or any other spirochaete was recovered from or detected in likely tick vectors. Some spirochaete-like objects detected in the cultures were shown to be artifacts, probably aggregates of bacterial flagellae. There is no definitive evidence for the existence in Australia of B. burgdorferi the causative agent of true Lyme disease, or for any other tick-borne spirochaete that may be responsible for a local syndrome being reported as Lyme disease.

Observations on cattle ticks in Huila Province (Angola)

In Huila Province of Angola, 3864 ticks were collected during a parasitological survey carried out in the rainy season from October 1990 to April 1991. The samples were collected from cattle gathered for the annual vaccination campaign against contagious bovine pleuropneumonia, anthrax and blackleg in 18 veterinary stations of six municipalities. After tick classification, the following proportions of ticks were obtained: Rhipicephalus evertsi mimeticus (27.1%), Amblyomma pomposum (26.4%), Boophilus decoloratus (19.0%), Rhipicephalus zambesiensis (9.4%), Rhipicephalus duttoni (8.3%), Hyalomma marginatum rufipes (3.8%), Hyalomma truncatum (3.0%), Rhipicephalus punctatus (2.5%) and Ixodes cavipalpus, Rhipicephalus lunulatus, Rhipicephalus turanicus, Rhipicephalus evertsi evertsi, Rhipicephalus simus, each less than 1%. These ticks are well known in southern Africa as vectors of diseases caused by protozoa and rickettsiae (babesiosis, theileriosis, anaplasmosis and cowdriosis). Control programmes against ticks and tick-borne diseases should be based on critical studies regarding costs/risks/benefits in relation to socio-economic and ecological frameworks.

Ticks (Acari: Ixodidae) infesting medium-sized wild mammals in southwestern Tennessee

Seven species of ixodid ticks (n = 2,661) were found on medium-sized wild mammals (n = 295) during a 13-mo study in Shelby County, Tennessee. The seven tick species collected were Dermacentor variabilis (Say), Amblyomma americanum (L.), Rhipicephalus sanguineus (Latreille), Ixodes texanus (Banks), I. cookei (Packard), I. scapularis (Say), and Haemaphysalis leporispalustris (Packard). The raccoon had the greatest tick species diversity in all of the aforementioned ticks except H. leporispalustris and R. sanguineus. The raccoon and opossum accounted for 96.9% of the ticks collected and were the most commonly captured medium-sized mammals. The only tick collected in high enough numbers for statistical analysis was D. variabilis. Mammal species and habitat type were the most important factors affecting the mean number of adult D. variabilis per mammal. The mean number of D. variabilis adults carried by raccoons was significantly higher than opossums. Whether a habitat occurred within Memphis city limits or outside city limits also affected the number of adult D. variabilis on mammals. The interaction between habitat, mammal, and whether inside or outside the city limits was near statistical significance. It is suggested that there is biological significance; within city limits, medium-sized wild mammals are forced into wooded areas where there is a subsequent increase in tick populations in these habitat patches.

Conspecificity of the ticks Ixodes scapularis and I. dammini (Acari: Ixodidae)

Reciprocal crosses between Ixodes dammini Spielman, Clifford, Piesman & Corwin from Massachusetts and Ixodes scapularis Say from Georgia produced offspring through the F3 generation when the experiment was discontinued. Reciprocal I. dammini x Ixodes pacificus Cooley & Kohls (California) and I. scapularis x I. pacificus crosses produced F1 progeny; however, all progeny were sterile. Assortative mating experiments between I. dammini and I. scapularis indicated that males and females of both species mated with the opposite sex of heterospecific or conspecific ticks when there was a choice. Conventional discriminant analysis of morphometric measurements of ticks from Georgia, North Carolina, Maryland, Massachusetts, and two populations of F1 hybrids indicated that there were recognizable differences. However, size-free (sheared) discriminant analysis indicated that these differences were largely size-dependent, with much overlap of the four eastern and two hybrid populations but no overlap with I. pacificus from California. Analysis of chromosomes (morphology and C band) indicated no differences between the Georgia and Massachusetts populations but showed a difference between them and the California population of I. pacificus. Analysis of isozymes showed that the genetic identity value for the Georgia and Massachusetts populations was within the normal range for conspecific populations, whereas the California population indicated congeneric but not conspecific relatedness to the Georgia and Massachusetts populations. Life cycle data collected under similar laboratory conditions showed no differences in length of feeding and molting periods among Georgia, Massachusetts, and California populations. These data and results of the work of other authors on tick host preferences and vector competence indicate that I. dammini is not a valid species separate from I. scapularis. Because the name Ixodes scapularis Say, 1821, has priority over the name Ixodes dammini Spielman, Clifford, Piesman & Corwin, 1979, I. dammini is relegated to a junior subjective synonym of I. scapularis (based on Article 23 of the International Code of Zoological Nomenclature).

Differentiation of Rhipicephalus ticks (Acari: Ixodidae) by gas chromatography of cuticular hydrocarbons

Gas chromatography of the cuticular hydrocarbons of 4 species of ticks belonging to the genus Rhipicephalus (R. sanguineus, R. turanicus, R. pusillus, and R. bursa) showed a unique pattern for each taxon. The hydrocarbon fractions were composed of a mixture of straight-chain, terminally methylated, and internally branched alkanes; however, only a small quantity of alkenes was detected. Freshly collected, dried, and alcohol-stored specimens of R. sanguineus were analyzed and their patterns found to be nearly identical. Collection of specimens from separate localities demonstrated a species-specific pattern for Spanish material.

[Differences in the distant transmission of the tick-borne encephalitis virus by ixodid ticks of 2 subfamilies]

Simultaneous but separate feeding of ticks on nonviremic animal (guinea pig) has shown that Amblyomminae ticks are practically unable to transmit distantly tick-borne encephalitis virus (TBEV) to the specimens of their own subfamily and to Ixodinae as well. Ixodes persulcatus and I. ricinus displayed their ability as donors and recipients of TBEV (adults and nymphs) not only for their own subfamily representatives but also as donors for recipients of Amblyomminae subfamily (nymphs and adults of Dermacentor and Rhipicephalus and nymphs of Haemaphysalis). Experimental and literature data analysis permits the authors to conclude that the very important role of TBEV circulation in nature belongs to the distant virus transmission. The absence of such type of virus exchange among Amblyomminae excludes this group of ticks from active virus circulation in TBEV foci.

Lyme disease in South Carolina

Lyme disease is present in South Carolina, though not as prevalent as in many other states in the country. The characteristics of South Carolina cases are similar to those of the nation as a whole. The tick vector of Lyme disease in the Southeast is not clearly established, but is thought to be Ixodes scapularis. Questions remain concerning the prevalence of infection in local ticks with Borrelia burgdorferi, and the risk to a person bitten by a tick in South Carolina.

[The use of smells of plant origin as indicators of the extensiveness and intensity of ixodid tick infection with the tick-borne encephalitis virus]

It has been shown that, using a simple olfactometer, through which moist air and smell of vegetative origin penetrate into the centre via different ends of the tube, ticks can be divided into two groups, those infected and not infected with tick-borne encephalitis virus. The method yielding a 100% division, is based on opposite changes in the behaviour of virus infected ticks: the attracting smells become repellent and vice versa. Normal reaction to smell measured by the length of the distance covered by an individual tick towards or from the smell source in the olfactometer tube varies in various groups of control and experimental ticks, but correlates with virus titre of ticks. It is greater in ticks with a higher level of virus reproducibility. The reaction to smell in infected ticks makes it possible to predict the intensity of their infestation.

[Tick-borne encephalitis in the Estonian SSR]

The foci of tick-borne encephalitis (TBE) of 2 types, differing in their morbidity rates, the character of their immunological structures, the species composition of carrier mites and their capacity for TBE virus carriership, have been shown to exist in Estonia. TBE morbidity is characterized by 4- to 5-year cycles, the overwhelming majority of TBE cases being registered in the area of the joint habitat of both species of mites. During the epidemic season 2 peaks of morbidity rise are registered, which corresponds to peaks in the number of mites in nature. Different epidemic importance of 2 species of carrier mites in TBE morbidity in Estonia has been shown.

[The taxonomic aspects of the transmission of the causative agent of Lyme disease]

According to world literature data 17 species of ixodid ticks have been studied for natural infection with the Lyme disease agent. Analysis of the data on the level of the infection, transovarial and transphase transmission has shown that main biological vectors of Borrelia burgdorferi are the species of the subgenus Ixodes s. str. - I. ricinus, I. persulcatus (Eurasia), I. dammini, I. pacificus (North America). Potential vectors are I. scapularis, I. dentatus, Amblyomma americanum, Dermacentor variabilis. Single isolations were registered for I. neotomae, Haemaphysalis leporispalustris, D. occidentalis. Nonidentified spirocheta was isolated from A. americanum, D. variabilis, D. parumapertum, Rhipicephalus sanguineus. No agent was isolated from I. cookey, D. albipictus, R. reticulatus, H. concinna. On the basis of comparative and ontogenetic data the species from a group of main vectors: I. ricinus, I. persulcatus, I. pacificus had been attributed by me to the phyletic group persulcatus before Lyme disease was discovered and its causative agent isolated. The question whether I. scapularis belongs to the group persulcatus was also discussed at that time but left open due to somewhat aberrant structure of gnathosoma at preimaginal phases (Filippova, 1969, 1971, 1973). 6 Palaearctic, 2 Indomalayan and 3 Nearctic species were referred to the group persulcatus at the time. I. dammini was described later, in 1979. Gnathosoma of its preimaginal phases has an intermediate structure between I. scapularis and other species of the group persulcatus. Sexually mature phase and nymph of I. dentatus have much in common with Palaearctic members of the group, I. pavlovskyi, I. kazakstani, I. kashmicus. Preimaginal phases of I. scapularis and nymph of I. dentatus were studied by me on the collection material. Thus, it is possible to speak of the belonging of main vectors of B. burgdorferi to a common phyletic group within the subgenus Ixodes s. str. and, therefore, of common origin of ecological medium for the agent. At the same time each species of the vector is an evolutionally developed difference of ecological medium for B. burgdorferi. Roots of the group persulcatus could originate as far as in Paleocene before the land connection between North America and Europe disappeared. Conditions for the existence of recent species, however, appeared considerably later and their flourishing is dated by Pliocene. The main epidemiological role belongs now to I. ricinus, I. persulcatus, I. dammini, I. pacificus.(ABSTRACT TRUNCATED AT 400 WORDS)

[Ixodid ticks of Pavlodar Province and their participation in the circulation of tularemia infection]

Investigations carried out in Pavlodar Province have shown that 7 species of ixodid ticks, Ixodes crenulatus, I. lividus, I. persulcatus, I. laguri laguri, Dermacentor marginatus, D. reticulatus, Haemaphysalis concinna, and one brought species, Hyalomma asiaticum, parasitize domestic animals and wild mammals. Maximum activity of pasture ticks of the genus Dermacentor falls on the end of April--beginning of May, that of H. concinna on the beginning of June. The growth in the abundance of pasture ticks, recorded during the last years, is favoured by the increase in the cattle live stock, its seasonal movements and pasture area reduction. Natural nidi of tularemia become more active. Since 1977 221 cultures of tularemia agent have been isolatid from pasture ticks. H. concinna takes the most active part in the infection circulation.