The incorporation of radio-labelled nucleic acid precursors by Theileria parva in bovine blood and salivary glands of Rhipicephalus appendiculatus ticks

Irvin A.D., Boarer C.D.H., Kurtti T.J. and Ocama J.G.R. 1981. The incorporation of radio-labelled nucleic acid precursors by Theileria parva in bovine blood and salivary glands of Rhipicephalus appendiculatus ticks. International Journal for Parasitology11:451–456. The uptake of radio-labelled nucleic acid precursors by blood and tick salivary gland forms of Theileria pana was studied. Piroplasms took up tritiated purines, particularly hypoxanthine, but not pyrimidines. Similar uptake was recorded by T. parva, both in tick saliva and in salivary glands maintained in vitro. Intermediate parasite stages were those most readily labelled in glands; this reflected active nucleic acid synthesis associated with rapid parasite division. Radio-labelling of T. parva in tick salivary glands could be of value in procedures used for concentrating and purifying theilerial sporozoites.     

Babesia ugwidiensis,a new species of Avian piroplasm from Phalacrocoracidae in South Africa

A new species of haematozoa, Babesia ugwidiensis sp. nov. from a cormorant is described. This is the first species of piroplasm to be recorded from the Phalacrocoracidae and the relationship of this parasite to other Babesia spp. from marine hosts is discussed.     

Pharmacological characterization of a tyramine receptor from the southern cattle tick,Rhipicephalus (Boophilus) microplus

The southern cattle tick (Rhipicephalus (Boophilus) microplus) is a hematophagous external parasite that vectors the causative agents of bovine babesiosis or cattle tick fever, Babesia bovis and B. bigemina, and anaplasmosis, Anaplasma marginale. The southern cattle tick is a threat to the livestock industry in many locations throughout the world. Control methods include the use of chemical acaricides including amitraz, a formamidine insecticide, which is proposed to activate octopamine receptors. Previous studies have identified a putative octopamine receptor from the southern cattle tick in Australia and the Americas. Furthermore, this putative octopamine receptor could play a role in acaricide resistance to amitraz. Recently, sequence data indicated that this putative octopamine receptor is probably a type-1 tyramine receptor (TAR1). In this study, the putative TAR1 was heterologously expressed in Chinese hamster ovary (CHO-K1) cells, and the expressed receptor resulted in a 39-fold higher potency for tyramine compared to octopamine. Furthermore, the expressed receptor was strongly antagonized by yohimbine and cyproheptadine, and mildly antagonized by mianserin and phentolamine. Tolazoline and naphazoline had agonistic or modulatory activity against the expressed receptor, as did the amitraz metabolite, BTS-27271; however, this was only observed in the presence of tyramine. The southern cattle tick's tyramine receptor may serve as a target for the development of anti-parasitic compounds, in addition to being a likely target of formamidine insecticides.     

NMR structure determination of tick anticoagulant peptide (TAP).

Tick anticoagulant peptide (TAP) is a potent and selective 60-amino acid inhibitor of the serine protease Factor Xa (fXa), the penultimate enzyme in the blood coagulation cascade. The structural features of TAP responsible for its remarkable specificity for fXa are unknown, but the binding to its target appears to be unique. The elucidation of the TAP structure may facilitate our understanding of this new mode of serine protease inhibition and could provide a basis for the design of novel fXa inhibitors. Analyses of homo- and heteronuclear two-dimensional NMR spectra (total correlation spectroscopy, nuclear Overhauser effect spectroscopy [NOESY], constant time heteronuclear single quantum correlation spectroscopy [CT-HSQC], and HSQC-NOESY; 600 MHz; 1.5 mM TAP; pH 2.5) of unlabeled, 13C-labeled, and 15N-labeled TAP provided nearly complete 1H sequence-specific resonance assignments. Secondary structural elements were identified by characteristic NOE patterns and D2O amide proton-exchange experiments. A three-dimensional structure of TAP was generated from 412 NOESY-derived distance and 47 dihedral angle constraints. The structural elements of TAP are similar in some respects to those of the Kunitz serine protease inhibitor family, with which TAP shares weak sequence homology. This structure, coupled with previous kinetic and biochemical information, confirms previous suggestions that TAP has a unique mode of binding to fXa.     

Exploring the midgut proteome of partially fed female cattle tick (Rhipicephalus (Boophilus) microplus)

The continued development of effective anti-tick vaccines remains the most promising prospect for the control of the cattle tick, Rhipicephalus (Boophilus) microplus. A vaccine based on midgut proteins could interfere with successful tick feeding and additionally interfere with midgut developmental stages of Babesia parasites, providing opportunities for the control of both the tick and the pathogens it transmits. Midgut proteins from partially fed adult female cattle ticks were analysed using a combination of 2-DE and gel-free LC-MS/MS. Analysis of the urea-soluble protein fraction resulted in the confident identification of 105 gut proteins, while the PBS-soluble fraction yielded an additional 37 R. microplus proteins. The results show an abundance of proteins involved in mitochondrial ATP synthesis, electron transport chain, protein synthesis, chaperone, antioxidant and protein folding and transport activities in midgut tissues of adult female ticks. Among the novel products identified were clathrin-adaptor protein, which is involved in the assembly of clathrin-coated vesicles, and membrane-associated trafficking proteins such as syntaxin 6 and surfeit 4. The observations allow the formulation of hypotheses regarding midgut physiology and will serve as a basis for future vaccine development and tick-host interaction research.     

Risk factors associated with ixodid tick species distributions in the Basque region in Spain

Ixodid tick abundance was investigated in the Basque region in Spain in two 1-year longitudinal studies, in 1992-1993 and 2003-2004. Forty zones were visited monthly and 162 672 ticks (87% larvae, 12% nymphs and 1% adults) were collected by blanket dragging. Eleven tick species belonging to the genera Ixodes, Haemaphysalis, Rhipicephalus and Dermacentor were identified including Haemaphysalis concinna Koch, which had not previously been reported in Spain. Tick species abundance differed between zones, studies and seasons. In 1992-1993, Haemaphysalis punctata Canestrini & Fanzago was the predominant species and distinct spring-summer and autumn-early winter peaks of activity were observed. In 2003-2004, Ixodes ricinus (Linneaus) was the most common species and was active throughout the winter. Larval and nymph seasonal activity patterns coincided in both 1993 and 2003 and this could facilitate co-feeding transmission of pathogens. Higher tick abundance was associated with increased livestock abundance in 1992-1993 and milder winter temperatures in 2003-2004. Tick collection rates in areas with moderate and high tick density were positively associated with the interaction between ambient temperature at sampling and rainfall 7 days prior to sampling. Collection rates were also significantly higher at medium rather than higher altitude, in forested areas than in open grasslands and lower in recreational areas frequented by people and with wet vegetation at sampling.     

Molecular characterization of an ancient Hepatozoon species parasitizing the 'living fossil' marsupial 'Monito del Monte' Dromiciops gliroides from Chile

The Microbiotheriid Dromiciops gliroides , also known as 'Monito del Monte', is considered to be a threatened species and the only living representative of this group of South American marsupials. During the last few years, several blood samples from specimens of 'Monito del Monte' captured at Chiloé island in Chile have been investigated for blood parasites. Inspection of blood smears detected a Hepatozoon species infecting red blood cells. The sequences of DNA fragments corresponding to small subunit ribosomal RNA gene revealed two parasitic lineages belonging to Hepatozoon genus. These parasite lineages showed a basal position with respect to Hepatozoon species infecting rodents, reptiles, and amphibians but are phylogenetically distinct from Hepatozoon species infecting the order Carnivora. In addition, the Hepatozoon lineages infecting D. gliroides are also different from those infecting other micro-mammals living in sympatry, as well as from some that have been described to infect an Australian species of bandicoot. The potential vector of this parasite appears to be the host-specific tick Ixodes neuquenensis because the sequencing of a long amplicon determined the presence of one of the two lineages found in the marsupial.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 568–576.     

The impact of RNA interference of the subolesin and voraxin genes in male <Emphasis Type="Italic">Amblyomma hebraeum</Emphasis> (Acari: Ixodidae) on female engorgement and oviposition

Reducing or replacing the use of chemical pesticides for tick control is a desirable goal. The most promising approach would be to develop vaccines that protect hosts against tick infestation. Antigens suitable for the development of anti-tick vaccines will likely be those essential for vital physiological processes, and in particular those directly involved in feeding and reproduction. In this study genes from Amblyomma hebraeum Koch that encode for subolesin and voraxin were studied in male ticks by RNA interference (RNAi). Males (unfed or fed) were injected with dsRNA of (1) subolesin, (2) voraxin, (3) subolesin plus voraxin or (4) injection buffer, after which they were held off-host overnight and then allowed to feed on rabbits together with normal female A. hebraeum. Females that fed together with male ticks injected with subolesin or subolesin + voraxin dsRNA had a higher rate of mortality, weighed substantially less and produced a smaller egg mass than the controls. However, females feeding with males injected with voraxin dsRNA alone were not significantly different from the controls with respect to mortality, engorged weight or fecundity. However, as assessed by semi-quantitative RT-PCR, voraxin was not silenced in this study, the reasons for which remain unknown. The results of this study suggest that A. hebraeum subolesin is worthy of further testing as a candidate tick vaccine antigen.     

蜱类分类系统的变更

随着分子生物学技术在蜱类研究中的应用,及对蜱类系统发生的深入研究,蜱的分类及命名发生了很大变更。而中国在这一领域的研究还停留在20世纪90年代,分类系统过时。文章对中国曾经采用的蜱类分类系统与现今世界上普遍认可的分类系统进行了详细比较,以期引起注意,从而促进蜱类系统学及其他研究领域的发展。     

Characterization of vitellin protein in the twospotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

In mites, vitellogenin synthesis, regulation and uptake by the oocytes as vitellin remain practically unknown. Although a partial sequence of the gene is now available, no previous studies have been conducted that describe the native vitellin protein in mites. The objective of this study was to characterize vitellin in the twospotted spider mite, Tetranychus urticae. The native twospotted spider mite vitellin migrated as a single major band with a molecular weight of 476 ± 14.5 kDa as compared to 590 ± 25.5 kDa for vitellin from the American dog tick, Dermacentor variabilis. However, isoelectric focusing analysis of native spider mite vitellin showed five bands with pI values slightly acidic to neutral (pH 5.8, 6.2, 6.7, 7.0 and 7.2), as is the case for insect and tick vitellins. Reducing conditions (SDS-PAGE) also revealed multiple subunits ranging from 290.9 to 3.6 kDa and was similar to that found in D. variabilis. Spider mite vitellin weakly bound lipids and carbohydrates compared to the tick. Unlike D. variabilis, the spider mite egg yolk protein does not bind heme. The significance of non-heme binding in mites is discussed.