On the spermatophore of ixodid ticks

Structure and formation of the spermatophore and the extrusion of its contents in ixodid ticks were studied. The structure of the ectospermatophore resembles that of argasid ticks, whereas that of the endospermatophore differs completely; it is composed of several organelles which are absent in argasids.The chemical nature of the components of the spermatophore was studied by histochemical methods. The male forms the spermatophore by ejaculating the components in a definite order. The components of the ectospermatophore are deposited one into another—while those of the endospermatophore one on top of the other and are linked together in a chain. The last component to be ejected is a plug that closes the endospermatophore.During extrusion of the endospermatophore all of the components burst out of the ectospermatophore. The endospermatophore sheath evaginates and forms the capsule into which the sperm is inserted. Each capsule has two tube-like appendices.     

Studies on the economics of ticks in Zambia

Two herds of experimental Sanga cattle were maintained under traditional savanna grazing management for three years in the Central Province of Zambia. One herd was kept free of ticks by regular acaricide treatment, while the other was given no tick control. Milk production, growth rate, fertility and mortality were monitored throughout the trial. The tick-free herd performed significantly better than the tick-infested herd, but the value of the additional production was much less than the cost of the acaricide used. it is concluded that there is no economic justification for intensive tick control under these conditions. However, strategic tick control would be justified if the quantity of acaricide used could be reduced by 50% without any major reduction in benefits. The results indicate that treating calves below 45 days of age reduces their performance, as does treating cows during periods of very low tick challenge. Therefore, it seems likely that economically beneficial strategic tick control policies could be developed.     

Hemolymph proteins in ticks

In comparison to insects and Crustacea, our knowledge of the predominant hemolymph proteins in ticks is minimal. The hemolymph protein most studied in ticks has been vitellogenin (Vg). Vg is synthesized by the tick fat body after female adults obtain a blood meal, is released into the hemolymph and is absorbed by developing oocytes as vitellin (Vn). Much of what we know about Vg is from studies of Vn. In general, the carbohydrate, lipid and amino acid composition is similar to insects except that in the tick, Vg contains heme, most likely from the digestion of host hemoglobin. In the American dog tick, Dermacentor variabilis, Vg is comprised of two native proteins and seven subunits on SDS-PAGE. Vg has been characterized in five tick species but the amino acid sequence is not yet available. Another predominant hemolymph protein, apparently a carrier protein (CP), has recently been studied in two tick species. This protein is found in the hemolymph of both male and females adults, in adult tissues outside of the hemolymph in some tick species, in coxal fluid of soft ticks and in whole body homogenates from eggs, larvae and nymphs. CP from the hard tick, D. variabilis, contains cholesterol, phospholipids, monoacylglycerides, triacylglycerides, free fatty acids, carbohydrate and heme. Under identical assay conditions, the analogous protein in the soft tick, Ornithodoros parkeri, did not contain heme. CP in the American dog tick consists of two subunits, one of which has 61% identity to the biliprotein, artemocyanin, from the fairy shrimp. CP is identical to a heme-lipoprotein (HeLp) from Boophilus microplus. The exact roles of CP and HeLp have not yet been fully determined, but they apparently are important in heme sequestration and as a storage depot for protein and lipid. Macroglobulin, lectin, antimicrobial, JH binding, JH esterase, and other tick hemolymph proteins are also discussed.     

蜱类系统学研究进展

本文介绍了近年来蜱的编目和分类及系统发育和演化等方面的研究进展。对软蜱科(Argasidae)说明了属的变动;硬蜱科(Ixodidae)介绍了璃眼蜱亚科(Hyalomminae)和凹沟蜱亚科(Bothriocrotoninae)以及相应变动的属(新建的凹沟蜱属Bothriocroton和须角蜱属Cornupalpatum,合并的牛蜱属Boophilus、暗眼蜱属Anocentor和盲花蜱属Aponomma)。根据新的分类变更对已知种类进行了分析。至2006年,世界已知蜱类有3科18属897种,中国有2科10属119种。阐明了有关蜱类系统发育研究的主要观点,并讨论了其不足和有待深入研究的问题。目前,把形态学和分子生物学数据结合在一起的全证据方法,并结合蜱类和不同宿主之间的关系、动物地理学、古生物学以及比较寄生虫学的资料,成为解决蜱类系统发育问题的有效途径。     

Artificial feeding of ixodid ticks

Ixodid ticks are economically important as they cause direct damage to livestock and are vectors of several pathogens that cause diseases in humans and animals. Some of the important tick-borne pathogens of livestock are Theileria parva, T. annulata, Babesia bigemina, B. bovis, Anaplasma marginale and Cowdria ruminantium. These pathogens are responsible for causing enormous losses in livestock. Identification of factors that influence transmission and development of these pathogens in ticks will greatly facilitate development of rational strategies for control of tick-borne diseases. This research has been hampered by the lack of suitable artificial feeding methods. In this paper, Sam Waladde, Aian Young and Subhash Morzaria review recent developments in the artificial feeding of ixodid ticks and evaluate how this method can potentially be exploited. They use an example the transmission of an important livestock pathogen, T. parva, by Rhipicephalus appendiculatus.     

Immunomodulatory arsenal of nymphal ticks

Ticks have developed their own immunomodulatory mechanisms to inhibit the host inflammatory response. One of them involves the ability to subvert the cytokine network at the site of tick feeding by secreting cytokine binding molecules. Most studies have focused on the immunomodulatory prowess of adult female ticks. Here we describe anti-cytokine activity in salivary gland extracts (SGEs) prepared from 2-day-fed nymphs of Dermacentor reticulatus Fabricius, Ixodes ricinus L., Rhipicephalus appendiculatus Neumann and Amblyomma variegatum Fabricius. Anti-CXCL8 activity was detected in nymphs of all species. Relatively high activity against CCL2, CCL3 and CCL11 was observed in SGEs of R. appendiculatus and A. variegatum nymphs, whereas SGEs of I. ricinus nymphs showed comparatively high anti-interleukin-2 (-IL-2) and anti-IL-4 activities. These data show that nymphs, which epidemiologically are usually more important than adults as disease vectors, possess a range of anti-cytokine activities that may facilitate pathogen transmission.     

Entomopathogenic nematodes for the biocontrol of ticks.

Entomopathogenic steinemematid and heterorhabditid nematodes are increasingly used to control insect pests of economically important crops. Laboratory and field simulation trials show that ticks are also susceptible to these nematodes. The authors review the potential of entomogenous nematodes for the control of ticks.     

中国蜱类名录

一、引言 蜱类对於疾病的传染,无论在人或其他动物,都是很重要的。文献告诉我们,这类节足动物,可以传染过滤性病毒(脑灾病),螺旋体(人和鸟的回归热病),立克次体(各种斑疹伤寒),以及原生动物(动物的焦虫病)所致的各种人和动物的病症。在我国,对於这些疾病的研究还不多,也无统计,但是无论在人和家畜,无疑蒙受了很大的损失。     

Observations on the separation of Theileria sporozoites from ticks

Hyalomma anatolicum anatolicum ticks infected with Theileria annulata were partially fed on rabbits and then ground up with tissue culture medium. The ground up ticks were treated by centrifugation at 100 g, filtration through membranes of 8 μm pore diameter and centrifugation on a discontinuous density gradient of Percoll. Counts of sporozoites and tick debris were made from Giemsa stained slides of samples at each stage of the separation. Debris was removed during light centrifugation and filtration at a greater rate than sporozoites. After filtration approximately 41% of the original sporozoites remained in the suspension. After density gradient centrifugation most sporozoites were found in a distinct zone, at approx. 1·08 g/cm³ density, separate from most dense debris and light debris and soluble contaminants. After this final centrifugation approximately 24% of the original sporozoites remained in the recovered suspension.     

Perspectives for subunit vaccines for the control of ticks

For the first time, successful vaccination against a tick has been carried out using a single defined antigen. Further, it has been shown that it is feasible to produce active antigenic material by recombinant DNA technology. This represents a significant advance towards the development of an alternative means of tick control. Nevertheless, as with any new product and new technology, much developmental work still has to be done before one can be confident that a practical means of tick control will result. From the published information, it does not seem that research on vaccines against other tick species is as advanced as that on Boophilus microplus. The work on B. microplus may, however, provide a short cut to the development of further tick vaccines.     

Advances in the genomics of ticks and tick-borne pathogens

Ticks and the diseases for which they are vectors engage in complex interactions with their mammalian hosts. These interactions involve the developmental processes of tick and pathogen, and interplay between the defensive responses and counter responses of host, tick and pathogen. Understanding these interactions has long been an intractable problem, but progress is now being made thanks to the flood of genomic information on host, tick and pathogen, and the attendant, novel experimental tools that have been generated. Each advance reveals new levels of complexity, but there are encouraging signs that genomics is leading to novel means of parasite control.     

An updated list of the ticks of Ghana and an assessment of the distribution of the ticks of Ghanaian wild mammals in different vegetation zones

Twenty one species of ticks belonging to five genera of the family Ixodidae (Order Acari, sub-order Ixodida) - Amblyomma, Haemaphysalis, Hyalomma, Ixodes and Rhipicephalus (including the sub-genus Rhipicephalus (Boophilus)) - were collected from 1260 mammals, representing 29 species, 14 families and 6 orders, in four vegetation zones in Ghana during the period 1971-1978. Four other species were collected from humans in 1977. In all, eight species appeared to be new records for Ghana: Amblyomma tholloni Neumann; Dermacentor circumguttatus Neumann; Haemaphysalis houyi Nuttall & Warburton; Ixodes loveridgei Arthur; Ixodes oldi Nuttall; Ixodes vanidicus Schultze; Rhipicephalus complanatus Neumann; Rhipicephalus cuspidatus Neumann. The updated list of tick species in Ghana given here includes 41 species of ixodid ticks and four species of argasid ticks. Most species have been found in neighbouring regions of West Africa but 56 of the 121 different combinations of ixodid tick species and host species found in the collection described here have not apparently been reported before. The new combinations recorded here bring the total number of different combinations of ixodid tick species and mammalian host species now reported in Ghana to 151. The tick species found on wild mammals in Ghana mostly differed from those reported from domestic stock by other authors. The data showed that different tick species occurred in different vegetation zones and that most species displayed a pronounced preference for certain groups of related host species. Some tick species were found in the savanna feeding mainly on large bovids and/or suids; others were found in forests feeding mainly on small bovids, large rodents or small carnivores.