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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Cytotaxonomy of ticks

Kahn, Jacob January 1961 (has links)
(1) This study of the nuclear cytology of ticks was undertaken in the hope that it might assist in problems of identification. Papers published hitherto on the nuclear cytology of ticks and mites are reviewed. (2) The material studied consists of laboratory bred specimens of ten species representing five Ixodid genera. The source and identifications as well as the rearing of Ixodid ticks are described in detail. (3) The preparation of organs and eggs, and the equipment used in this study are described. (4) An exhaustive account is given of (a) male and female mitosis of all ten species, (b) male meiosis of nine species and female meiosis of one species. (5) General aspects of the nuclear eytology of ticks, such as endomitosis, spermatogenesis and karyomerokinesis, are discussed in conjunction with the material described. (6) Incidental observations on the anatomy of Ixodes testes and their accessory glands are compared with Douglas' description of D. andersoni. (7) The discussion summarises the eytologioal observations and their bearing on taxonomy and phylogeny. It is suggested that Ixodes should be given the status of a family.
22

Alterações morfológicas em glândulas salivares de fêmeas de carrapatos Amblyomma cajennense Fabricius, 1787, (Acari: Ixodidae) em diferentes estágios de alimentação durante sucessivas infestações em coelhos /

Nunes, Pablo Henrique. January 2009 (has links)
Resumo: O contato dos carrapatos com os hospedeiros e a liberação de antígenos por meio da saliva estimula o desenvolvimento de respostas imune por parte dos hospedeiros. Os objetivos deste trabalho foram os de analisar e comparar morfo-histoquimicamente as glândulas salivares de fêmeas de Amblyomma cajennense fixadas em hospedeiros naive e reinfestados, e os resultados revelaram que coelhos reinfestados por A. cajennense desenvolvem resistência contra os mesmos em apenas uma infestação e essa resistência provoca efeitos no ciclo de atividade e na degeneração das glândulas salivares. Fêmeas fixadas em coelhos resistentes apresentaram aumento do tempo necessário para atingir o completo ingurgitamento e fêmeas ingurgitadas apresentaram redução significativa do peso final. As glândulas salivares dessas fêmeas apresentaram alterações morfológicas, que foram mais evidentes naquelas submetidas à terceira infestação. A histologia e a histoquímica mostraram que os ácinos I não sofreram alterações em comparação com aqueles das fêmeas fixadas em coelhos naive. As células c dos ácinos II apresentaram sinais de degeneração precoce, o que resultou na diminuição da eficiência alimentar. No ácino III as células d estenderam o tempo de atividade, provavelmente relacionado ao aumento do tempo de permanência das fêmeas nos hospedeiros resistentes. / Abstract: The contact with the ticks and hosts and the antigen releasing by saliva, stimulates the immune response development by the hosts. This study aims to analyze and compare morphohistochemically the salivary glands of Amblyomma cajennense females fixed on naive and reinfested hosts. The results show that re-infested rabbits by A. cajennense develop resistance against them in only one infestation and such resistance shows effects in the development and degeneration cycle of salivary glands. Females fixed on resistant rabbits showed an increase in the time required to complete the engorgement while the final weight of engorged females showed significant reduction. These female salivary glands showed morphological changes, which were more evident in females subjected to the third infestation. The acini I, no changes had been occurred compared with those of females fixed in naive rabbits. The acini II, the c cells showed early degeneration signs, which may result in feed efficiency reduction. In acini III, the d cells extended the activity time, which may be associated with the increase in the female fixation time which had been fed on resistant hosts. / Orientador: Maria Izabel Camargo Mathias / Coorientador: Gervásio Henrique Bechara / Banca: Marcelo Bahia Labruna / Banca: Itabajara da Silva Vaz Junior / Banca: Teresinha Tizu Sato Schumaker / Banca: Karim Christina Scopinho Furquim / Doutor
23

Development of formulations and delivery systems to control economically important ticks with entomopathogenic fungi

Nchu, Felix 03 December 2009 (has links)
Due to the rapid development of tick resistance to synthetic chemical acaricides and the potential risk posed by these chemicals to non-target species, efforts are intensifying towards the development of entomopathogenic fungi as an environmentally benign alternative tick control strategy. The main objective of this study is the development of formulations and delivery systems for control of ticks with entomopathogenic fungi. Screening of entomopathogenic fungal isolates is the first step towards the development of mycoacaricides. Twelve isolates of Metarhizium anisopliae (Metschnik.) Sorok. and three isolates of Beauveria bassiana (Bals.) Vuill. (Ascomycota: Hypocreales) were evaluated for pathogenicity against unfed Rhipicephalus pulchellus Gerstäcker (Acari: Ixodidae) adults under laboratory conditions. Out of the 15 isolates screened, 4 isolates were virulent against R. pulchellus, inducing significantly (F value = 11.86; DF = 14, 75; P < 0.0001) higher tick mortalities; i.e. ICIPE 78 (76.1 ± 5.9%), ICIPE 69 (62.6 ± 5%), ICIPE 62 (49.8 ± 5.8%) and ICIPE 60 (49.6 ± 7.7%), four weeks post-treatment compared to the others. The results of this study demonstrate that R. pulchellus ticks were susceptible to some M. anisopliae isolates. Since the process of strain selection is an important step in the development of insect pathogens for biological control, an appropriate bioassay technique for infecting different life stages of a host is of paramount importance. Bioassays were conducted in the laboratory to evaluate the efficacy of different methods of inoculation using R. pulchellus as a model. In a preliminary experiment, an oil-based formulation of M. anisopliae titred at 109 conidia ml-1 was applied to R. pulchellus adults using a Burgerjon spray tower or a microapplicator. Inoculation by microapplicator yielded poor results (25.0% tick mortality) compared to Burgerjon’s spray tower (52.3% tick mortality) , although the mean number of fungal conidia on R. pulchellus adults was lower (1.5 x 104 ± 1.1 x 103 conidia ml-1) after spraying by Burgerjon’s spray tower compared to 1 x 106 conidia ml-1 obtained with the microapplicator. Thus, inoculation by Burgerjon’s spray tower was selected for further investigations. Different modes of inoculation were tested and included direct spray of inoculum on the tick and substrate (SS), direct spray on the substrate and tick followed by transfer of the tick to clean uncontaminated Petri dish (SP) or indirect inoculation of ticks through substrate (SW). The LC50 values following contamination of nymphs (LC50 = 1.4 x 107 conidia ml-1) and adults (LC50 = 6.7 x 107 conidia ml-1) in SS were significantly lower compared to SP; nymphs (LC50 = 5.7 x 108 conidia ml-1) and adults (LC50 = 5.3 x 109 conidia ml-1) and SW; nymphs (LC50 = 5 x 108 conidia ml-1) and adults (LC50 > 1010 conidia ml-1). Although the LC50 value in SS was the lowest, it recorded the highest tick mortality among control ticks (24.2% at two weeks post-treatment) and (23.3% at three weeks post-treatment) in nymphs and adults respectively compared to SP (2.5 and 5.8% respectively) and SW (0.0 and 0.0). Results show that among the modes of contamination tested, SP was the most appropriate for contaminating R. pulchellus adults. SW and SP were identified as appropriate techniques for infecting the R. pulchellus nymphs with conidia formulated in oil. The integrated use of semiochemicals and entomopathogenic fungus (hypocreales) may optimise the performance of a fungus as a biocontrol agent against ticks. Initially, experiments were conducted to evaluate the attraction of the hunter tick Amblyomma variegatum Fabriscius (Acari: Ixodidae) to semiochemicals. In one of the experiments, the simultaneous release of 1-octen-3-ol and AAAP together with CO2 from a trap in simulated field plots attracted up to 94 ± 6% of adult ticks from a distance of 6 m, and up to 24.0 ± 5.1% from 8 m. Formulations of M. anisopliae (dry powder, oil, and emulsifiable) applied within the trap baited with AAAP and 1-octen-3-ol resulted in high levels of contamination of the ticks attracted to the traps. However, 48 hr after autoinoculation, 89.1 and 33.3% of conidia were lost in dry powder and oil formulations, respectively. Emulsifiable formulation lost the lowest number of propagules (17.1%). Samples of ticks attracted to the baited traps were transferred to plastic basins containing grass and maintained for 5 weeks. The experiment was conducted in the rainy and dry seasons. The emulsifiable formulation gave the highest relative reduction in tick numbers in both seasons: 54.7 and 46.5% in the rainy and dry seasons, respectively, followed by the oil formulation (32 and 23.8%) and the powder formulation (38.0 and 24.4%). Following the high attraction and contamination of A. variegatum under semi-field conditions, experiments were done to evaluate the efficacy of M. anisopliae-treated semiochemical-baited traps for control of A. variegatum under field conditions. Unfed A. variegatum adults (118) were seeded in each 100-m plot. An emulsifiable formulation of M. anisopliae (consisting of 49.5% sterile distilled water, fungal conidia, 49.5% corn oil [CHEF cooking oil, Premier Oil Mills LTD] and 1% Tween 80) titrated at 109 conidia ml-1- was applied in a semiochemical-baited traps (900 cm2) which were placed at 5 spots within the plot. The control and fungal treatments were repeated after 14 and 28 days soon after rotating the traps clockwise (45o) in order to cover different sections of the plot. In the control plots, traps baited with semiochemicals only were used. Six weeks after the initiation of the experiments, five semiochemical-baited traps (untreated) were deployed in each plot for 3 successive days to trap ticks in the treated and control plots. The percentage of ticks recovered in the fungus-treated plots were significantly lower (31.1 ± 5.2%) than in the control plots (85.6% ± 3%) (P < 0.001), which represented a relative tick reduction of 63.7%. Mortality of 93.8 ± 2.3% was observed among the ticks that were recovered from the field and maintained in the laboratory for two weeks; while only 3.3 ± 0.9% died from the control plots. The results of this study open up the possibility of developing an environmentally friendly, low cost product to control these economically important ticks. / Thesis (PhD)--University of Pretoria, 2009. / Paraclinical Sciences / unrestricted
24

The toxicity and repellent properties of plant extracts used in ethnoveterinary medicine to control ticks

Mawela, Kedibone Gloria 16 February 2009 (has links)
Six plant species (Aloe ferox, Aloe marlothii, Clerodendrum glabrum, Jatropha curcas, Ricinus communis and Strychnos madagascariensis) used by communities in the northern parts of South Africa to control ticks on livestock were selected from the database of the Onderstepoort Veterinary Institute. The leaves of these species were extracted with organic solvents ranging from polar to non-polar (methanol, acetone and dichloromethane). Infusions (soap-water-paraffin) and decoctions traditionally used were also prepared. The tick repelling and toxicity activities of the extracts were evaluated against the livestock tick, Rhipicephalus appendiculatus. Initial results of the tick-climbing repellency bioassay illustrated that a 30% concentration of crude acetone extracts of A. ferox, A. marlothii and C. glabrum; DCM extracts of R. communis and A. marlothii and MeOH extract of J. curcas repelled the ticks to a statistically significant level. Of all the aqueous extracts only the decoction of S. madagascariensis repelled ticks significantly. At lower concentration of 10%, only acetone extracts of C. glabrum were effective. Three types of bioassays were conducted for toxicity i.e., dipping, topical and dry extract applications. Organic extracts were not effective. Infusions of A. ferox and S. madagascariensis. had strong topical application toxicity at a concentration of 35.5 % while the same concentration of infusions of A. ferox and J. curcas had a strong dipping toxicity effect. Both A. ferox and S. madagascariensis extracts were still toxic at the concentration of 30% in topical and dipping bioassays. In general acetone was a good extractant with lower yields but higher percentage repellency. Polar aqueous extracts had high yields but lower percentage repellencies. It may be that volatiles present in organic extracts are repellents and non-volatiles from aqueous extracts are toxic. Some of the fractions of C. glabrum had a higher tick repellency activity than the commercial tick control agents used as positive controls. Unfortunately the activity decreased after 2.5 hours probably due to a volatility of the biologically active compound. Attempts were made to isolate the repellent compound from the acetone extract of C. Glabrum. The process gave very good results up to a late stage of the bioassay guided fractionation. At that stage the repellent activity was lost. When two fractions were combined the repellent activity was present again. This is strong evidence for the existence of a synergistic effect. Further attempt to isolate the compounds at this stage and characterize them by nuclear magnetic resonance spectroscopy failed probably through decomposition of the compounds. This aspect can probably be followed up in more detail. The results substantiated the rationale behind the use of these plant extracts to control ticks. Even a simple acetone extract of leaves of some species has excellent tick repelling activities. If the duration of this effect could be increased it could very well develop into a commercially useful product. The tick repelling activity of S. madagascariensis decoctions and tick killing activity of A. ferox soap infusion holds great promise for the control of ticks by rural farmers. In vivo trials under controlled conditions should provide useful results. / Dissertation (MSc)--University of Pretoria, 2008. / Paraclinical Sciences / unrestricted
25

Oviposition habits of the tick Dermacentor parumapertus Neumann and factors influencing egg development

Jorgensen, Clive D. 01 May 1957 (has links)
This paper includes data concerning the influence of relative humidity, temperature, and percentage of engorgement on the pre-oviposition period, oviposition period, post-oviposition period, and incubation period of the tick Dermacentor parumapertus Neumann. The influence of the percentage of engorgement on the oviposition period, oviposition rate, and egg number is considered. Data on the disposition and number of eggs in nature are discussed.
26

Die isolering en identifisering van die hondafwerende faktor in die kutikulêre afskeiding van die geelhondebosluis, Haemaphysalis leachi

Marx, Brenda 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: When in close contact with the Yellow Dog Tick, Haemaphysalis leachi, dogs show clear signs of disgust or even nausea. It is accepted that the secretion is produced by the tick in order to prevent the dog from removing the tick from its body with its teeth, thereby increasing the chances for the tick's survival. The composition of this secretion was studied in order to identify the chemical compounds responsible for the repellent action of the secretion. Because of the dog's keen sense of smell, the tick only needs to produce minute quantities of this repellant, which significantly complicated the detection of the different components by conventional GC-methods. Several sampling and sample enrichment methods were explored, including solvent extraction, SPME sample enrichment, adsorption on active charcoal, cryoprecipitation, sorption in a phasecoated open tubular trap, as well as solventless sampling, in order to determine which method would ensure an appropriate amount of sample for gas chromatographic detection. Two of these sampling methods yielded acceptable results: The first method consisted of rinsing irritated female ticks with dichloromethane and, after concentrating the sample by evaporation, GC-MS analysis using normal splitless injection. The second method entailed collecting secretions by wiping irritated ticks with glass micro fibre filter paper after which the paper was inserted directly into the inlet liner of the GCMS system, where thermal desorption of the volatile constituents of the secretion preceded gas chromatographic separation and mass spectral detection. Live dogs were needed for the evaluation of the isolated material to determine whether the samples had an aversive effect on them. The extract was separated into different fractions, which were further separated into subfractions. After each separation process, all the fractions were tested for efficacy in order to determine which fraction contained the active components, narrowing down the number of candidate target compounds. It was concluded that a combination of aldehydes, namely hexanal, heptanal, octanal, nonanal, decanal, undecanal and dodecanal, is responsible for the dog repelling action of the secretion. In most cases the semiochemicals of insects and mammals are secreted in a more complex matrix to ensure prolonged activity. For this reason some of the other compounds in the complex cuticular secretion of this tick species were also identified during the course of this study. / AFRIKAANSE OPSOMMING: Honde toon duidelike tekens van afkeer of selfs naarheid wanneer hulle in noue kontak kom met die afskeiding van 'n sekere bosluisspesie, die geelhondebosluis, Haemaphysalis leachi. Daar word aangeneem dat die bosluis die afskeiding produseer om te verhoed dat die hond dit met sy bek van sy liggaam verwyder. Hierdeur word die oorlewingskanse van die bosluis verbeter. 'n Studie is gemaak van die samestelling van die vlugtige komponente van hierdie afskeiding om die chemiese verbindings, wat verantwoordelik is vir die afweer van honde, te identifiseer. As gevolg van die sensitiwiteit van 'n hond se reuksintuig, is dit vir die bosluis nodig om slegs uiters klein kwantiteite van hierdie afweerstof af te skei, wat die waarneming van die verskillende komponente deur middel van konvensionele GC-metodes baie bemoeilik het. Ten einde die mees effektiewe metode te vind wat 'n gepaste hoeveelheid monster vir waarneming op 'n gaschromatograafdetektor sou verseker, is verskeie monsternemings en -verrykingsmetodes ondersoek, naamlik oplosmiddelekstraksie, SPME-monsterverrykingsmetodes, adsorpsie op aktiewe koolstof, kriopresipitasie, sorpsie in 'n fase-belaagde oopbuisval en oplosmiddellose monsterneming, Twee monsternemingsmetodes het aanvaarbare resultate gelewer: Met die eerste metode is geïrriteerde wyfiebosluise met dichlorometaan afgespoel en die ekstrak is na indamping met behulp van monsterinspuiting sonder inlaatstroomverdeling deur middel van GC-MS geanaliseer. Met die tweede metode is die afskeiding van geïrriteerde bosluise met mikroglasveselpapier afgevee en die papier is direk in die binnebuis van die inlaat van die GC-MS-sisteem geplaas, waar die vlugtige komponente termies gedesorbeer is vir gaschromatografiese skeiding en massaspektrometriese waarneming. Om die aktiwiteit van die geïsoleerde materiaal te evalueer, is van lewende honde gebruik gemaak, om vas te stel of hulle aversie teenoor die betrokke monsters toon. Die ekstrak is in verskillende fraksies geskei, wat weer in subfraksies verder geskei is. Alle fraksies is na elke skeidingsproses getoets vir effektiwiteit om vas te stel watter van die fraksies die aktiewe verbindings bevat. Sodoende is die aantal moontlikhede vir die teikenverbindings met elke skeidingstap verminder. Daar is gevind dat 'n reeks aldehiede, naamlik heksanaal, heptanaal, oktanaal, dekanaal, undekanaal en dodekanaal, gesamentlik verantwoordelik is vir die afweer van honde. Insekte en soogdiere skei dikwels semioverbindings in 'n draermateriaal af om daardeur meer langdurige werking te verseker. In hierdie ondersoek is dus ook 'n begin gemaak met die identifisering van die ander verbindings wat in die besonder komplekse kutikulêre afskeiding van hierdie bosluisspesie aanwesig is.
27

An investigation into the potential immunogenicity of various extracts of the South African bont tick Amblyomma hebraeum

Adamson, Deborah Jane January 1993 (has links)
Rabbits and goats were inoculated with crude, membrane-associated and soluble components extracted from unengorged adult females and nymphs of the bont tick Amblyomma hebraeum. Inoculation provided some protection against nymphal infestation, however it had little effect on adult feeding. Histological examination of adults fed on inoculated hosts showed evidence of gut damage. Skin provocation testing with tick extracts elicited a Type I immediate hypersensitivity which was influenced by antihistamine. A delayed skin reaction was also evident. Whether this was attributable to Type III Arthus reaction or Type IV cell-mediated hypersensitivity was not determined. A comparative histological study of sites of tick extract injection, on inoculated and naive hosts, demonstrated the role of eosinophils in the hosts response to tick feeding. Serological examination revealed elevated anti-A hebraeum lgG titres following inoculation. These titres were found to decrease in the ten weeks after inoculation, despite the hosts being repeatedly infested with A hebraeum. Although the IgG titres of naive control hosts increased after each tick infestation, they failed to reach the titres achieved through inoculation. Western blot analysis of serum from inoculated hosts recognized most of the A. hebraeum proteins against which it was screened.
28

Socio-economic impact analysis of livestock disease control programmes with special reference to ticks and tick-borne diseases

Randela, Rendani 26 February 2007 (has links)
Please read the abstract in the section 00front of this document / Dissertation (MSc Agric)--University of Pretoria, 2007. / Agricultural Economics, Extension and Rural Development / unrestricted
29

Tick control in Tswana, Simmental and Brahman cattle by means of Neem seed extracts (Azadirachta indica)

Davidi, Matayo 17 February 2006 (has links)
Please read the abstract in the section 00front of this document / Dissertation (MSc Agric (Animal Science))--University of Pretoria, 2006. / Animal and Wildlife Sciences / unrestricted
30

Drug target discovery by transcriptome analysis of the brown dog tick, Rhipicephalus sanguineus, synganglion : initial characterisation of a nicotinic acetylcholine receptor

Lees, Kristin January 2008 (has links)
A normalised cDNA library was constructed from the synganglia of unfed adult <i>R. sanguineus.  </i>Of interest from a drug discovery perspective were ESTs encoding a chitinase enzyme and four transmembrane receptors including two glutamate-gated chloride receptors, a leucokinin-like receptor and a nicotinic acetylcholine receptor (nAChR) α subunit. The nAChR α subunit was chosen for further study.  This is the first identified full-length arachnid nAChR subunit.  Phylogenetically it is most similar to insect α1 nAChR group and has been called Rsα1.  This subunit is expressed in larval, nymphal and adult stages and within partially fed adult females.  <i>Rsα1 </i>was most abundant in the synganglion and also present in Malpighian tubules and oviduct yet was undetected in the salivary glands and gut tissues.  Using two-electrode voltage clamp in <i>Xenopus laevis </i>oocytes, Rsα1 did not functionally express as a homomer or when co-expressed with the vertebrate chicken β2 subunit using either RNA or DNA.  Chimeric constructs consisting of the tick N-terminal and the transmembrane portion of the <i>D. melanogaster </i>α2 nAChR (Dα2) (Rsα1-Dα2) and vice-versa were prepared.  Responses to acetylcholine were obtained from the Dα2-Rsα1 chimera showing that the Rsα1 nAChR can form a functional pore region.  However, no responses were obtained from the Rsα1-Dα2 chimera.  This preliminary data suggests that the Rsα1 nAChR cannot form a functional ligand binding region when expressed in Xenopus oocytes. The present study has proven that the tick synganglion is a rich source of transmembrane receptor targets for exploitation in future drug discovery.

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