The Effect of Male Ticks on the Feeding Performance of Immature Stages of Rhipicephalus Sanguineus and Amblyomma Americanum (Acari: Ixodidae)

A unique group of immunoglobulin-binding proteins (IGBPs), produced by ixodid male ticks during the latter half of their prolonged feeding period, improves the feeding performance of co-feeding females. As a follow-up to this observation, we investigated whether male tick feeding also affects the feeding of other developmental stages. Immature stages of Rhipicephalus sanguineus (Latreeille) and Amblyomma americanum (L.) were fed on rabbits in the presence or absence of conspecific males. The mean weight of larvae and nymphs of both species that fed around males and detached from the host on the first day of dropping was significantly higher than when the immature ticks fed on rabbits in the absence of males. However, larvae of both species and nymphs of R. sanguineus that fed slower and detached on the second day of dropping did not show significant differences in weight. A similar pattern was observed for A. americanum nymphs although, unlike R. sanguineus, the presence of males also influenced the feeding performance of the nymphs that fed slowly and detached on the second day of drop-off. The improved feeding performance demonstrated by immature ticks in the presence of males may be due to immunomodulatory saliva proteins, such as immunoglobulin-binding proteins (IGBPs) that are introduced into the co-feeding site. The results are considered in relation to the distribution of ixodid tick species on their natural hosts.     

The limiting effect of host availability for the immature stages on population growth in economically important ixodid ticks.

Of 12 southern African species of ixodid ticks in which the adults are commonly parasitc on cattle, only 4 exhibited massive increases in abundance in the absence of dipping. It is suggested that host availability for the immature stages is the major factor limiting population growth in a given environment. The species showing large increases in abundance are those in which the immature stages are predominantly parasitic on cattle, whereas the species showing small to moderate increases in abundance are those in which the immature stages are parasitic on specific nonungulate hosts.     

硬蜱一些生物学特性的研究

实验室内饲养17种硬蜱,分析和比较了它们生长发育的一些特性.硬蜱成虫、幼虫和若虫的吸血时间受温度影响不大.同一种成虫在不同寄主上吸血时间略有差别.雌虫吸血时间的长短与其生理年龄和与雄虫交配的早晚有关.雄虫较雌虫吸血时间稍长.产卵前期、产卵期、孵化期及饱食幼虫和若虫的蜕化期在不同月份有较大差异,受温度影响很大.其中,产卵前期是生活史中变异范围最大者,有些种类还具有产卵延迟的滞育现象.     

Differential distribution of immature Ixodes dammini (Acari: Ixodidae) on rodent hosts

Ectoparasites such as ixodid ticks that remain attached to hosts for several days while feeding on blood are able to overcome the inflammatory and immune responses of some hosts and not others. The immature stages of the deer tick Ixodes dammini are found more frequently on the white-footed mouse, Peromyscus leucopus, than on other rodents. We propose that P. leucopus is more tolerant to I. dammini than is a less common host, the meadow vole, Microtus pennsylvanicus. To test this hypothesis, the distribution patterns and engorgement indices were determined for larval and nymphal I. dammini collected from wild-caught P. leucopus and M. pennsylvanicus. There were more immature ticks, which were more fully engorged, on P. leucopus than on M. pennsylvanicus. There were more and better engorged ticks on male than on female hosts. Laboratory studies on the number and weights of larval I. dammini collected off naive and previously exposed P. leucopus and M. pennsylvanicus support the results of the field study. Fewer larval ticks were recovered from previously exposed M. pennsylvanicus than P. leucopus, and the ticks weighed less. Larval and nymphal ticks aggregated among hosts in the study grid, and higher densities per male P. leucopus were correlated with higher engorgement indices, suggesting that immature I. dammini feed better at higher densities. The feeding success of I. dammini on its preferred host species might be due to its adaptation to the immune and inflammatory reactions of the host.     

The characteristics of the ixodid tick-vertebrate animal parasitic system]

The parasitic system ixodid tick (parasite)--vertebrate animal (host) is relatively stable in space and time. Equilibrium state in the system is maintained at the low levels of the hosts' infection and moderate intensity of their immunity. Parasite sensitizes the host's organism at the stage of feeding on antigens of its saliva and the host develops different degrees of resistance preventing the subsequent individuals of ticks from normal feeding. Antitick immunity is species specific. Its intensity is defined by the species belonging of the parasite and host, intensity and intervals between infections, availability of "anti-immune mechanisms" in tick and by many other factors, which are realized at the feeding stage. Regulation of the number of ticks, depending on their abundance in the host's population, is attained due to the oversparse, close to negative binomial distribution on hosts. This mechanism functions on the principle of feedback, so that at the excessive number of the parasite some individuals in the host's population, which are especially subjected to infection, do not cope with parasitic burden and die. However, ticks, which failed to finish their feeding and represent a disproportionately great part of the whole parasite's population, die together with them and the parasitic system quickly restores its stability. In anthropocoenoses and ecosystems at different stages of anthropogenic transformation mutual regulation mechanisms of the parasite and host number break down. As a consequence, extremely high rises in the number of ticks and epizootics of agricultural animals associated with them can occur.     

Experimental study of micro-habitat selection by ixodid ticks feeding on avian hosts

Mechanisms of on-host habitat selection of parasites are important to the understanding of host-parasite interactions and evolution. To this end, it is important to separate the factors driving parasite micro-habitat selection from those resulting from host anti-parasite behaviour. We experimentally investigated whether tick infestation patterns on songbirds are the result of an active choice by the ticks themselves, or the outcome of songbird grooming behaviour. Attachment patterns of three ixodid tick species with different ecologies and host specificities were studied on avian hosts. Ixodes arboricola, Ixodes ricinus and Ixodes frontalis were put on the head, belly and back of adult great tits (Parus major) and adult domestic canaries (Serinus canaria domestica) which were either restricted or not in their grooming capabilities. Without exception, ticks were eventually found on a bird’s head. When we gave ticks full opportunities to attach on other body parts – in the absence of host grooming – they showed lower attachment success. Moreover, ticks moved from these other body parts to the host's head when given the opportunity. This study provides evidence that the commonly observed pattern of ticks feeding on songbirds’ heads is the result of an adaptive behavioural strategy. Experimental data on a novel host species, the domestic canary, and a consistent number of published field observations, strongly support this hypothesis. We address some proximate and ultimate causes that may explain parasite preference for this body part in songbirds. The link found between parasite micro-habitat preference and host anti-parasite behaviour provides further insight into the mechanisms driving ectoparasite aggregation, which is important for the population dynamics of hosts, ectoparasites and the micro-pathogens for which they are vectors.     

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.     

Demography and population models of ticks of the genus Ixodes with long-term life cycles

The most important parameters necessary for the creation of population models for threehost species with long-term life cycles are discussed with an example of ticks Ixodes persulcatus and I. ricinus. In these species, specimens of the same biological age may belong to different age cohorts and their calendar age may differ by several months or even years. Accurate estimation of the calendar age of separate individuals is dofficult; it is based on the extrapolation by its possible biological age and by belonging to the certain age cohort of a natural population. Population models that can predict simultaneous abundance of activated hungry specimens of all the three developmental stages and probability of host-finding in hyngry ticks during questing period possess the prognostic value. Daily mortality of ticks of different developmental stages and phases of each stage (questing, feeding, preparation for molting, and diapause) must also be known. The abundance of questing hungry ticks in the ecosystem is determined by the balance between recruitment of the population with new individuals, their selection by hosts, dying of ticks from starvation, and consumption of ticks by predators. At present, unfortunately, only some of these parameters are known rather sufficiently.     

Mammals as hosts of Ixodid ticks (Acarina,Ixodidae)

Trophic association between adult ticks of the world fauna with their mammal hosts (511 tick species out of 650 species of Ixodidae of the world fauna) are reviewed. Specific tick species parasitize on representatives of 22 (out of 27) mammal orders, but species of Paucituberculata, Notoryctemorphia, Peramelemorphia, Scandentia, and Dermoptera have no specific parasites. The highest number of tick species was recorded from Artiodactyla and rodents. Mammals, on which representatives of all the 14 genera of the family parasitize, provide the diversity of the ixodid tick fauna. The conclusion on the priority of ecological factors in comparison with phylogenetic status of hosts in the formation of specific characteristics of ticks confirms Balashov’s (1982) concept on the character of host-parasite association between ticks and mammals.     

Characteristics of acquired resistance of lambs to mature ticks Hyalomma asiaticum asiaticum (experimental studies)]

A new method was employed for studies of parasite-host relationships between ixodid ticks and their hosts. It has been established that ixodid ticks are able to desensibilize the reactive sensibility of the host and to satiate themselves without unhibiting the latter. Every day and long parasitism of the ticks on cattle (in nature) and increasing doses of secretion of the ticks' saliva (sensibilizer) lead apparently to the weakening of the host's organism (desensitization). However, under laboratory conditions in hosts a resistence to bites of ixodid ticks can appear.     

Goats,hares, and rabbits as hosts for the New Zealand cattle tick,Haemaphysalis longicornis

Abstract

Feral goats and hares were commonly infested by immature stages of the New Zealand cattle tick, Haemaphysalis longicornis. No explanation could be found for the low prevalence of adult ticks on these hosts. The ears of both host species were almost the exclusive feeding site of the ticks and this may be a consequence of grooming behaviour. Another potential host, the rabbit, was examined but few were found to be infested.

The less restricted range of non-domesticated hosts, together with feeding habits that differ from domestic stock, make them an important additional source of information on the ecology and seasonal pattern of activity of H. longicornis. Also, they are a source of contamination for tick-free pasture, and could possibly maintain the tick population in the absence of sheep and cattle. It is important that their role as alternative hosts be understood and considered in tick-control programmes.     

Structure of populations and ecological nishes of ectoparasites in the parasite communities of small forest mammals

The paper reports the results of eight-year investigations on the ectoparasites of rodents and insectivores carried out in southern taiga of the Ilmen-Volkhov lowland (Novgorod Region) and Kurgolovsky reserve (Leningrad Region). Twelve species of small mammals were captured including three dominate species--bank vole Clethrionomys glareolus (2722 specimens), common shrew Sorex araneus (1658 specimens), and wood mouse Apodemus uralensis (367 specimens). Parasite community of the bank vole comprises 34 species of mites, ticks, and insects, the community of common shrew comprises 25 species, and the community of A. uralensis includes 28 species. Taxonomic diversity of the ectoparasite communities was shown to be based on the diversity of types of parasitism and ecological nishes of the host body. Permanent ectoparasites are found to be represented by 2 species of lie and 14 species of acariform mites. The group of temporary parasites includes 13 species of fleas, 10 species of gamasid mites. 3 ixodid species and 1 Trombiculidae. There is a common pool of temporary parasites of small mammals in the ecological system of taiga. Significance of different shrew and rodent species as hosts were found to be dependent on the population density in possible hosts and many other factors. Species diversity in the parasite communities of different small mammal species is dependent on the number of possible ecological nishes in the host body. Actual infill of these nishes by ectoparasites is usually lesser than potential one. Species composition of temporary parasites, their occurrence and abundance changes according to season. Interspecific competition in the temporary parasite species can decrease because of the seasonal disjunction of their population peaks. Diversification of the ecological niches of ectoparasites allow simultaneous feeding of more parasite individuals on one host, than in the case of parasitising of single species or several species with similar ecological nishes. The distribution of parasites on their hosts was also studied. The aggregative distribution has been found in ixodid larvae only, and the distribution of fleas was close to the Poisson distribution. Deviations from the aggregative distribution can be an effect of several independent factors, including limited ability of small mammals for providing numerous parasites with food. On the most part of hosts simultaneous parasitizing of no more than 1-3 individuals of each tick, mite, and flea species was registered. Excessive infestation by ectoparasites may probably be limited by effective reactions of self-purification in the mammal hosts.     

Influence of Abiotic Factors on Different Developmental Stages of the Taiga Tick <Emphasis Type="Italic">Ixodes persulcatus</Emphasis> and the Sheep Tick <Emphasis Type="Italic">Ixodes ricinus</Emphasis>

This paper presents an analytical literature review of the effects of abiotic factors on the different developmental stages of the ixodid ticks Ixodes persulcatus and I. ricinus. These widespread species are generally well adapted to the potential variation gradient of the factors most important for their development, such as temperature and humidity, and also other environmental conditions. Their variation usually does not significantly affect the mortality of ticks at various “passive” stages of their development cycle. However, the number of generations of both species can vary if these factors influence the percentage of fully engorged diapausing individuals.     

Ticks Feeding on Humans: A Review of Records on Human-Biting Ixodoidea with Special Reference to Pathogen Transmission

In this article, literature records of argasid and ixodid ticks feeding on humans worldwide are provided in view of increased awareness of risks associated with tick bites. Ticks can cause paralyses, toxicoses, allergic reactions and are vectors of a broad range of viral, rickettsial, bacterial and protozoan pathogens. Approximately 12 argasid species (Argas and Ornithodos) are frequently found attached to humans who intrude into tick-infested caves and burrows. Over 20 ixodid tick species are often found on humans exposed to infested vegetation: four of these are Amblyomma species, 7 Dermacentor spp., 3 Haemaphysalis spp., 2 Hyalomma spp. and 6 Ixodes species. Personal protection methods, such as repellents and acaricide-impregnated clothing are advised to minimize contact with infected ticks. Acaricidal control of ixodid ticks is impractical because of their wide distribution in forested areas, but houses infested with soft ticks can be sprayed with acaricidal formulations. Attached ticks should be removed without delay. The best way is to grasp the tick as close to the skin as possible with fine tweezers and pull firmly and steadily without twisting. Finally, despite the fact that most people who are bitten destroy the offending tick in disgust, it is recommended that they preserve specimens in ethanol for taxonomic identification and detection of pathogens by molecular methods.     

Effect of host lizard anemia on host choice and feeding rate of larval western black-legged ticks (Ixodes pacificus)

Although ticks are known to exhibit preferences among host species, there is little evidence that ticks select hosts within a species based on physiological condition. It may be beneficial for ticks to choose hosts that are easier to feed upon if the ticks can perceive indicative chemical or other signals from the host. For example, if ticks can detect host hematocrit they may choose hosts with high hematocrit, facilitating a faster blood meal. It may similarly be adaptive for ticks to avoid anemic hosts because it may be difficult for them to obtain an adequate meal and feeding duration may be extended. We tested the hypothesis that larval western black-legged ticks (Ixodes pacificus) detect host hematocrit using external cues and choose healthy over anemic hosts, allowing them to feed more quickly. We presented groups of larval ticks with pairs of healthy and anemic male western fence lizards (Sceloporus occidentalis), allowed them to select a host, and measured the feeding duration of the ticks. We found that the ticks did not exhibit a statistically significant preference for healthy over anemic lizards, but that the ticks fed to repletion significantly faster on healthy hosts than on anemic hosts. Larval ticks may not be able to detect external cues indicating the health of the host, at least not in terms of their hematocrit. The extended feeding duration likely reflects the extra time needed for the ticks to concentrate the blood meal of their anemic hosts.     

Birds as hosts of ixodid ticks (Acarina,Ixodidae)

rophic relations between ixodid ticks of the world fauna parasitizing as adults on birds are analyzed. These ticks include 60 out of 650 species of the family Ixodidae and belong to the genera Ixodes, Haemaphysalis, and Amblyomma. Relations between birds and ticks of the genus Ixodes are most ancient. Colonial marine birds seem to be the first hosts of ixodid ticks in the class of birds. Trophic specialization of ticks is not associated with bird taxa, because in most cases no tick specificity is caused by either phylogenetic features of hosts, or specific environmental conditions.     

Host-seeking behaviour by Australian ticks (Acari: Ixodidae) with differing host specificities

Ticks generally detach from their hosts into sites where they are later exposed to host species which may or may not be suitable for infestation. The question of how four species of ixodid ticks, with differing specificities, behave towards such potential host species was examined. Observations of the generalists,Aponomma hydrosauri andAmblyomma limbatum and the specialists,Aponomma fimbriatum andAponomma concolor, showed that the generalists were attracted to a wider range of potential host species than the specialists and that the larval stages of all tick species, regardless of specificity, contacted more potential host species than the adults. The interspecific differences may be attributed to reliance on different sets of host cues, while the intraspecific differences may reflect the developmental state of the sensory system.     

Saliva-activated transmission (SAT) of Thogoto virus: dynamics of SAT factor activity in the salivary glands ofRhipicephalus appendiculatus,Amblyomma variegatum,andBoophilus microplus ticks

Thogoto (THO) virus is transmitted from infected to uninfected ticks when co-feeding on uninfected guinea-pigs, even though the guinea-pigs do not develop a detectable viraemia. This form of non-viraemic transmission is potentiated by a factor (s) secreted by the saliva of ticks and hence has been termed saliva-activated transmission (SAT). The synthesis of the SAT factor by the salivary glands of three ixodid tick species was determined by placing uninfected nymphal ticks on guineapigs that were subsequently inoculated with a mixture of THO virus and salivary gland extract (SGE) derived from one of the tick species. SAT factor activity was measured by determining the number of nymphs that acquired THO virus. For the three-host ixodid species,Rhipicephalus appendiculatus andAmblyomma variegatum, maximum enhancement of THO virus transmission was observed when salivary glands were derived from uninfected, female ticks that had fed for a period of 6 or 8 days, respectively. In contrast, when salivary glands were derived form uninfected femaleBoophilus microplus, a one-host ixodid tick species, enhancement of THO virus transmission was observed throughout the tick feeding period. Thus, the natural feeding behaviour of ticks appears to be an important factor in determining the relative importance of these vectors in mediating SAT.     

Observations on Antricola ticks: small nymphs feed on mammalian hosts and have a salivary gland structure similar to ixodid ticks

Ticks use bloodmeals as a source of nutrients and energy to molt and survive until the next meal and to oviposit, in the case of females. However, only the larvae of some tick species are known to feed upon bats; females are obligatorily autogenous, and nymphal stages are believed to not feed. We investigated the presence of blood in a natural population of nymphal Antricola delacruzi ticks collected from bat guano; their ability to feed upon laboratory hosts; and the microscopic structure of both salivary glands and gut. DNA amplification of gut contents of freshly collected material was positive for a mammal in 4 of 11 first instar nymphs, but we were unsuccessful in the amplification of host bloodmeal DNA from late instar nymphs. All early nymphal stages (n = 10) fed on rabbits, and host DNA was detected and sequenced from gut contents. However, all the large nymphs (n = 10) rejected feeding, and host DNA remained undetected in these ticks. All stages of A. delacruzi have salivary glands similar in morphology to the ixodid agranular Type I salivary gland acini and to granular Type II or Type B acini. All stages of A. delacruzi had a similar gut structure, consisting of digestive cells in the basal portion that contained hematin granules. Neither regenerative nor secretory cell traces were observed in the sections of gut.     

Gluttony and sex in female ixodid ticks: how do they compare to other blood-sucking arthropods?

The central issue dealt with here is the role of copulation in the control of feeding behaviour in ticks and some haematophagous insects. Female ticks of the family Ixodidae normally engorge to approximately 100 x their unfed body weight, and then drop from the host, produce and lay eggs, and die. Virgins, on the other hand, normally do not exceed 5-40% (depending on species) of the normal engorged body weight. But instead of detaching voluntarily at that point most virgins remain fixed to the host for extended periods, waiting for males to find them so they can complete engorgement. Virgin haematophagous insects, and virgin ticks of the family Argasidae display little, if any, reduction in blood meal size compared to mated females, at least not during the first ovarian cycle. During subsequent ovarian cycles, meal size in some virgin insects may be somewhat reduced depending on how many eggs are retained in the reproductive tract, but the reduction is not nearly to the same extent as that observed for virgin ixodid females. The stimulatory effect of copulation on engorgement in the latter is caused by a pair of proteins (voraxin alpha and beta) produced in the testis and transferred to the female with the spermatophore. Here, I propose why it might be adaptive for an ixodid female to remain small until mated. The hypothesis is suggested from the facts that ixodid ticks remain attached to the host for days (rather than minutes), and that virgin ticks, above a certain critical weight, lose all opportunity for producing viable offspring should they be groomed off the host prematurely, or should the host die while ticks are still attached.