Reason for fluctuation in the demographic structure of the taiga tick population (Ixodidae) in dark conifer-leaf forests of Kemchug Upland

It was found out, that mean ratio of unfed taiga ticks Ixodes persulcatus having a life cycle of 3-5 and 6 years counts respectively (N = 6) 33.6, 52.8, 13.2 and 0.4%. Data on absolute number of I. persulcatus individuals in the process of onthogenesis is given. It is shown, that mortality of different unfed stages increases from larva to imago. In the autumn-winter period, the mean ratio of eliminated individuals counted 16% of larvae, 20% of nymphs, and 38 of imago. The mortality in the spring-summer period caused mainly by the deficit of hosts and counted for these stages 3, 82 and 98% respectively. Engorged ticks successfully undertake unfavorable conditions both in the spring-summer and autumn-winter periods. Their mean mortality in the period from feeding to moulting does not exceed 12%.     

Demographic structure of the population of taiga tick (Ixodidae) in coniferous forests of the Kemchug upland in 1986-1991

It is recovered, that full engorged females of Ixodes persulcatus lay average of 25,250 eggs per 1 ha during the season in the test area. It produces 13,750 larvae. The abundance of hungry larvae is reduced up to 12,500 during the winter period. 11,643 larvae become engorged. The total abundance of hungry nymphs counts: 10,933 in autumn, and 9895 in spring. The total abundance of hungry adults, half of which is represented by females, makes 1774 in autumn, and 1084 in spring. About 10 females found their hosts and became successfully engorged.     

Variability of the life cycle duration in the taiga tick from mixed coniferous-broad-leaved forests of the Udmurt Republic

Seasonal cohorts of the unfed Ixodes persulcatus imago in the study area were found to consist of the ticks passed through three-, four-, and five-year life cycles, in the ratio 72.6, 26.4, and 2.0% respectively, on the base of mean long-term values. Such ratio is established if 91.7% of larvae and 79.9% of nymphs develop without diapause, while the rest of larvae and nymphs develop with diapause. Mean duration of the tick generation is 3.3 years, with the fluctuations in certain of the years within the limits of 3.15-3.36 years.     

The correlation variability of the morphometric traits in 4 species of ixodid tick species (Ixodidae)]

Correlation analysis of 10 characters was run in three species of Dermacentor, D. nuttalli, D. ushakovae, D. niveus, and in Ixodes persulcatus, separately for each phase and sex. Correlation coefficients are very low in larvae of all species. In male nymphs correlation coefficients are on the same level in all species while the correlation coefficient level in female nymphs reflects the degree of independence of the development of characters. This defines the degree of manifestation of sexual dimorphism at the nymphal phase: the more rigid the connections between the characters the less number of characters shows sexual differences. At the phase of imago the lowest correlation coefficients are in I. persulcatus. This species displays most distinct differences in the morphology of females and males. On the basis of comparison of correlation and variability coefficients the functional role of the characters is discussed.     

The meadow tick Dermacentor reticulatus in natural foci of tick-borne encephalitis in Udmurtia

In southern Udmurtia, where occur both Dermacentor reticulatus and Ixodes persulcatus, in the years of high abundance of small mammals feeding periods of larvae and nymphs of these ticks coincide completely. The duration of simultaneous parasitism of preimago of the above ixodid species on animals is of epidemiological significance as far as within this period the infection of young stages of D. reticulatus with the virus of tick-borne encephalitis occurs. This is confirmed by the isolation of I strain of the virus from D. reticulatus collected at the state of engorged nymphs on hosts common with I. persulcatus and moulted in the laboratory.     

Transovarial and transphasic transmissions of Borrelia by the taiga tick Ixodes persulcatus (Ixodidae)

Three generations of the taiga tick Ixodes persulcatus, the descendants from naturally infected females, have been examined by means of dark field and phase contrast microscopies and indirect immunofluorescent reactions with monoclonal antibodies. Location of borreliae in oocytes was examined by means of electron microscopy. The examined ticks derived from 9 females collected in the Novgorod Province, from 6 females of 1st laboratory generation and 5 females of the 2nd generation. In total, 250 larvae, 178 nymphs, 59 females and 70 males of three consequent generation have been examined. Almost 100% of descendants of naturally infected females were infected with Borrelia burgdorferi s. l. and similar infection rate was observed in unfed tick larvae collected in field conditions. The borreliae received transovarially to larvae of the 1st generation then were transmitted to 100% nymphs and imago of this generation and two next generations.     

Predation of Galendromus helveolus (Acari: Phytoseiidae) on Brevipalpus californicus (Acari: Tenuipalpidae)

The false spider mite, Brevipalpus californicus (Banks), is a major citrus pest in Texas. This phytophagous mite causes damage to fruit, leaves and stems of citrus, and is also a vector of citrus leprosis virus. Galendromus helveolus (Chant) is one of the most prevalent predacious mite species found on Texas citrus. The predation potential of G. helveolus on different stages of B. californicus was evaluated in the laboratory. An individual immature G. helveolus mite consumed an average of 30.7 eggs, 53.6 larvae, or 22.7 nymphs of B. californicus before developing to an adult. An individual adult female G. helveolus consumed an average of 164.8 eggs, 369.6 larvae, or 80.9 nymphs of B. californicus. Both immature and adult G. helveolus never fed on adult stage of B. californicus and never completed development. The development times of the immature stages of G. helveolus were 4.5, 4.1 and 4.6 days when fed on eggs, larvae and nymphs of B. californicus, respectively. When G. helveolus fed on the larval stage of B. californicus, the adults had the longest longevity (18.5 days) and the highest fecundity (14.0 eggs/female).     

Life history of the predatory mite Lasioseius athiasae (Acari, Ascidae) on various kinds of food substances: a polypeptide analysis of prey consideration

The predacious ascid mite Lasioseius athiasae Nawar and Nasr was found in association with herbaceous plants, fallen leaves and in debris under deciduous fruit trees. The larvae fed and developed on different prey, such as 'motile stages of the eriophyid grass mite Aceria dioscoridis (Soliman and Abou-Awad), eggs of house fly Musca domestica L., nymphs of the two-spotted spider mite Tetranychus urticae Koch, and eggs of the root-knot nematode Meloidogyne incognita Chitwood. Eriophyids of grasses caused the immature stages to develop faster than did other prey. During the oviposition period, daily consumtion by a female of L. athiasae was 97  A. dioscoridis , four M. domestica eggs, and 10 T. urticae nymphs . The average number of eggs/female per day was 3.21, 1.63 and 1.26 for the above-mentioned prey, respectively. A low rate was recorded on M. incognita eggs (0.35). The intrinsic rate of increase ( rm ) was increased when fed on A. dioscoridis , but decreased on other prey species. The multiplication per generation ( R _o) was 44.73 times in a generation time ( T ) of 17.92 days when fed on eriophyids. The eriophyid grass mite proved to be the more suitable prey. The polypeptide analysis of different prey revealed that A. dioscoridis has the most important contents in both number (11 polypeptides) or total molecular weight (682 kDa).     

Phenology of the tick, Ixodes ricinus, in its southern distribution range (central Spain)

The abundance, seasonal activity patterns and development rates of the tick Ixodes ricinus (L.) (Acari: Ixodidae), as well as microclimate features of the site of study, are described for a 9-year-long study (1994-2002) in north-central Spain. According to drag captures, larvae had a unimodal activity pattern, with a maximum observed around July-August, whereas nymphs displayed a bimodal pattern (May-June and August-September) with strong dominance of spring activity. An inversion of this pattern, with larger autumn peak, was observed in years with humid summers. Adults showed a small spring peak and a large autumn one. In the later years of the study, a small increase in the adult spring peak of activity was noticed, correlated with mild winters. Over the entire period of study, a clear increase in the total tick abundance was detected. Statistically significant differences between years were observed for some climate variables (saturation deficit, winter temperatures and number of days with temperatures above 6 degrees C), but a consistent and constant pattern of change was not observed in any climate variable. Temperature requirements for developing stages showed a sharp decrease in weeks 35-51 (eggs) and 38-50 (larvae and nymphs), a feature attributed to the presence of the morphogenetic diapause, beginning around September. Development rates obtained under quasi-natural conditions were almost twice those reported for other sites, suggesting an adaptation of this local, largely isolated I. ricinus population. According to drag captures and field-obtained development rates, interchange of nymphs between the two cohorts is common in this site, and seems to be influenced by the winter temperature and the date of larval engorgement.     

The morphogenic diapause of the taiga tick and the methods for its quantitative assessment in a field experiment]

Methods of quantitative estimation of critical photoperiod and critical date of entering the diapause in ixodids have been worked out. S-shaped dependence of the number of diapausing larvae and nymphs of Ixodes persulcatus on their feeding periods has been shown. It has been established that in Central Udmurtia the average critical date of entering the diapause in 50% of satiated larvae and nymphs falls at the 18th and 29th of June, respectively, with the light day length of 17 hr 10 min and 16 hr 22 min.     

The infection of ixodid ticks collected from humans with the tick-borne encephalitis virus in Tomsk city and its suburbs

The ticks Ixodes persulcatus and I. pavlovskyi collected from people visited gardens and suburban forests have been examined by the IFA methods on the presence of tick-borne encephalitis virus (TEV). It was established, that the most part of ticks collected from humans belongs to I. persulcatus, despite the fact that I. pavlovskyi dominates on the territory of the city and its suburbs. TEV infection was registered more often in fed ticks, in comparison with those without signs of preceding feeding. Infected specimens constituted 9.4% of 53 I. persulcatus individuals examined. In I. pavlovskyi 3.7% of 27 examined specimens were infected. In fed ticks (41 specimens of I. persulcatus and 20 I. pavlovskvi) the rates of infected specimens were higher and constituted 48.8 and 35%, respectively. In suburban forests, as well as in the city, I. persulcatus was found to attack humans more often than I. pavlovskyi. TEV infection was recorded in 12.7% of 220 unfed I. persulcatus specimens examined and in 41.6% of 142 fed individuals. In I. pavlovskyi, 6.6% of unfed and 25% of fed specimens was infected (33 unfed and 24 fed specimens were examined). Thus, in all territories examined, percent of infected specimens was significantly lower in I. pavlovskyi, and in fed ticks of both species, TEV was recorded more often.     

Development of Iphiseiodes quadripilis (Banks) (Acari: Phytoseiidae) on pollen or mite diets and predation on Aculops pelekassi (Keifer) (Acari: Eriophyidae) in the laboratory

Development and reproduction of Iphiseiodes quadripilis (Banks) were evaluated on single food diets of pollen (Malephora crocea Jacquin [ice plant] or Quercus sp. [oak]), spider mites, [Eutetranychus banksi (McGregor) or Panonychus citri (McGregor) (Acari: Tetranychidae)], or the citrus rust mite Phyllocoptruta oleivora (Ashmead) (Acari: Eriophyidae). Experiments were conducted in an environmental chamber at 28 degrees +/- 1 degrees C, 14:10 (L:D) daylength, and 45% RH. I. quadripilis completed development and laid viable eggs that subsequently hatched on diets of either ice plant or oak pollen or eggs and motile stages of E. banksi. P. citri was acceptable as prey, but survival of larvae to adults was only 36%, whereas survival on E. banksi, ice plant pollen, and oak pollen was 48, 60, and 68%, respectively. The webbing produced by P. citri seemed to inhibit foraging behavior of I. quadripilis larvae and nymphs. Larvae of I. quadripilis developed only to the second nymphal instar on a diet of P. oleivora alone or water alone. Starved I. quadripilis females and deutonymphs were observed preying on the pink citrus rust mite, Aculops pelekassi (Keifer) (Eriophyidae). During 4-min observation trials, two series of I. quadripilis fed on 1.8 +/- 0.47 and 3.5 +/- 0.45 A. pelekassi motile stages after being starved for 6 and 24 h, respectively. I. quadripilis females did not prey on P. oleivora in arenas containing both rust mite species.     

Development, survival, and oviposition of the rabbit tick, Haemaphysalis leporispalustris (Packard) (Acari: Ixodidae), at constant temperatures

The relationship between development, survival, and oviposition rates, and five constant temperatures is described for the developing and reproductive life stages of the rabbit tick, Haemaphysalis leporispalustris (Packard). Development was most rapid at 29.7 C for egg and larvae, and 35.6 C for nymphs. Survival was greatest between 14.7 and 29.7 C, but was reduced at 35.6 C for eggs and larvae. Oviposition was optimal between 19.9 and 29.7 C with a maximum mean daily oviposition of 253 eggs/female/day on the third day of oviposition at 29.7 C. Maximum mean total eggs per female produced was 1,157 with a range of 277 to 3,327. The total number of eggs produced per female correlated with the weight of the engorged female. Both linear and sigmoid curve equations were used to approximate the relationship between the temperature and development rates of eggs, larvae, and nymphs. The nymphs had the highest heat requirements of the 3 development stages. Comparisons with field host-parasite data indicate that the rabbit tick has a 2-yr life cycle in southwestern Nova Scotia.     

森林革蜱、草原革蜱感染和经期传播莱姆病螺旋体的实验研究

以实验室培育的非感染森林革蜱Dermacentor silvarum、草原革蜱D. nuttalli刺叮人工感染21天后的阳性KM鼠,利用分离培养和PCR方法检测蜱对螺旋体的保持能力以及体内螺旋体对敏感动物的感染能力。结果如下：非感染幼蜱均可以通过吸血获得莱姆病螺旋体,饱血森林革蜱和草原革蜱幼蜱PCR阳性率均为50.0%而分离阳性率都为20.0%。饱血脱落后,这些幼蜱只能在饱血后2天内分离到莱姆病螺旋体。PCR检测阳性也只能持续到4天,均不能跨越蜕皮阶段。蜕化为若蜱后,若蜱以及分别受到这些若蜱刺叮的KM鼠均未发现阳性感染。非感染若蜱吸食感染的KM鼠后,饱血森林革蜱和草原革蜱获得了莱姆病螺旋体,PCR检测阳性率分别为50.0%和20.0%。分离阳性率分别达到33.3%和60.0%。这些若蜱分别于饱血后2天和3天可以分离到莱姆病螺旋体,PCR扩增阳性也只能分别持续到饱血后4天和6天,均不能跨越蜕皮阶段;蜕化为成蜱后,成蜱以及受到它们攻击的KM鼠均未获阳性检测结果。同种蜱不同地理株在感染和保持莱姆病螺旋体的能力上也没有差异。森林革蜱、草原革蜱的幼蜱和若蜱虽可以吸血感染但均不具备经期传播莱姆病螺旋体Borrelia garinii CHNM4的能力,作为莱姆病媒介的可能性不大。     

Habitat requirements of the seabird tick, <Emphasis Type="Italic">Ixodes uriae</Emphasis> (Acari: Ixodidae), from the Antarctic Peninsula in relation to water balance characteristics of eggs,nonfed and engorged stages

The seabird tick Ixodes uriae is exposed to extreme environmental conditions during the off-host phase of its life cycle on the Antarctic Peninsula. To investigate how this tick resists desiccation, water requirements of each developmental stage were determined. Features of I. uriae water balance include a high percentage body water content, low dehydration tolerance limit, and a high water loss rate, which are characteristics that classify this tick as hydrophilic. Like other ticks, I. uriae relies on water vapor uptake as an unfed larva and enhanced water retention in the adult, while nymphs are intermediate and exploit both strategies. Stages that do not absorb water vapor, eggs, fed larvae and fed nymphs, rely on water conservation. Other noteworthy features include heat sensitivity that promotes water loss in eggs and unfed larvae, an inability to drink free water from droplets, and behavioral regulation of water loss by formation of clusters. We conclude that I. uriae is adapted for life in a moisture-rich environment, and this requirement is met by clustering in moist, hydrating, microhabitats under rocks and debris that contain moisture levels that are higher than the tick's critical equilibrium activity.     

Diagnostic DNA amplification from individual tick eggs,larvae and nymphs

The species of single tick eggs, larvae and nymphs was determined by PCR amplification and characterization of the hypervariable, second transcribed spacer (ITS2) of the multicopy ribosomal RNA gene (rDNA). Engorgement of larvae and nymphs did not preclude species identification. The method is generally applicable for ixodid and argasid ticks and can be used for epidemiological studies requiring the identification of individuals from pre-adult stages.     

Sex ratio in ixodid tick collections from Leningrad Province

The analysis of results of many-year regular collections of ixodid ticks has shown that females (56%) were dominant in I. persulcatus while in I. ricinus were dominant males (52%). The ratio between sexes in both species changed noticeably as in individual years so during the imago activity season. In summer collections of I. lividus females were dominant every year, the share of which accounted on the average for 70% and varied from 69 to 75% within different seasons and from 60 to 83% within imago activity season. During hibernation and in spring the share of males and females was nearly adequate.     

Observations on the biology of Rhabdochona kidderi texensis, a parasite of North American cichlids

An examination of a sample of benthic invertebrates collected from the Upper San Marcos River in southwestern Texas, USA in September 1999 revealed that the nymph of the ephemeropteran Tricorythodes curvatus served as natural intermediate host of the nematode Rhabdochona kidderi texensis (Nematoda: Rhabdochonidae), an intestinal parasite mainly of the Rio Grande perch (Cichlasoma cyanoguttatum) in this locality; the prevalence of the parasite's third- and fourth-stage larvae in mayflies was 6.8% with the intensity of 1-2 larvae per nymph. Live R. kidderi texensis eggs collected from nematodes recovered from C. cyanoguttatum in Texas were transported to the Czech Republic, where they were used to experimentally infect nymphs of the palaearctic mayfly species Paraleptophlebia submarginata; the development of infective third- and fourth-stage larvae in this experimental intermediate host was completed after approximately 10 days at 19 degrees C. Infected nymphs were fed to aquarium-reared fishes, four Cichlasoma nigrofasciatum and one Oreochromis niloticus, of which only three of the former became infected. The last (fourth) moult of a male nematode was observed in C. nigrofasciatum 23 days p.i. and adult males and gravid females with not fully mature (non-embryonated) eggs in uteri on days 40 and 51 p.i. The prepatent period of R. kidderi texensis is approximately two months.     

Ability of transovarially and subsequent transstadially infected Ixodes hexagonus ticks to maintain and transmit Borrelia burgdorferi in the laboratory

In a previous study, transstadial and transovarial survival of Borrelia burgdorferi in Ixodes hexagonus and transmission to laboratory mice via the bite of infected females were demonstrated. Here, we report the ability of I. hexagonus progeny infected transovarially to maintain and transmit the spriochaete to the host.Ticks were examined for spirochaetes by direct immunofluorescence antibody test. I. hexagonus larvae derived from the parental transstadially infected females were fed on two white mice: 21/54 (38.9%) of these ticks examined as unfed nymphs were infected. I. hexagonus nymphs were fed on three white mice and examined for spirochaetes after moulting as adults: 7/25 (28%) were found to harbour the spirochaete. The success of B. burgdorferi transmission to the mice by larval and nymphal I. hexagonus was determined by xenodiagnosis using I. ricinus larvae: 20/50 (40%) and 30/99 (30.3%) of the I. ricinus larvae fed on the mice infected by I. hexagonus larvae and nymphs respectively became infected.This study shows that B. burgdorferi can be maintained through transovarial and subsequent transstadial transmissions in I. hexagonus.     

Studies on the ecology of Amblyomma marmoreum Koch 1844 (Acarnia: Ixodidae).

In the Eastern Cape Province of South Africa, larvae and nymphs of Ablyomma marmoreum Koch occur in habitats in which there is tree cover and herbaceous ground cover. Immatures of A. marmoreum are parasitic on reptiles, birds, and mammals. Adults occur only on reptiles. The major host for all stages is the moutain tortoise (Geochelone pardalis), and in the home areas of tortoises the density of ticks is high. Larvae are active in late summer and autumn. The rate of feeding is temperature-dependent, and some larvae which attach on tortoises in late autumn do not complete feeding until the following spring. Nymphs which occur in the home area of a tortoise become active in response to CO2 in early spring. Adults, and nymphs which occur outside the home area of a tortoise, become active in summer in response to rising temperatures. In nymphs which feed in spring, and hence develop into adults in midsummer, the life cycle is completed in 1 year. In nymphs which fed in midsummer, the life cycle is completed in 2 years.