Thesis (MSc (Veterinary Tropical Diseases)--University of Pretoria, 2009. / Includes bibliographical references. Also available in print format.

Infestation of cattle by Lone Star ticks, Amblyomma americanum, leads to damage of hides intended for leather, weight loss, infertility, and potentially death of cattle, which contribute to production losses for farmers. Public concerns regarding chemical residues in food and the environment necessitate development of chemical-free alternative tick controls, such as breeding for tick-resistant phenotypes and developing anti-tick vaccines. Thus, the goal of this study was elucidation of mechanisms that mediate immune responses in cattle infested with A. americanum using gene expression techniques. Methods for isolation of total RNA from bovine tick bite-site biopsies and blood leukocytes were optimized to provide RNA suitable for gene expression studies. Tick bite-site biopsies (6 mm) and blood leukocytes were collected from a total of 13 calves (N=6, Group 4 and N=7, Group 5 calves) during experimental tick infestations to determine A. americanum tick-susceptible and -resistant phenotypes. Microarray experiments compared gene expression in tick bite-sites from tick-susceptible, moderately tick-resistant, and highly tick-resistant calves. A total of 35 genes were profiled in tick bite-site biopsies and 12 genes were evaluated in blood leukocytes via gene-specific qRT-PCR assays, and analyzed for each phenotype and for each group of calves as a whole. Analysis of microarray data revealed differential expression of IL-1R-mediators among the three cattle phenotypes. Expression profiles generated by qRT-PCR for TLR-mediating genes such as TLR2, TLR4, CD14, and MyD88 suggest that a MyD88-dependent signaling pathway may mediate the development of acquired immunity in cattle infested with Lone Star ticks. Additionally, increased expression for IL12, IFNgamma, and TNFalpha suggests that a Th1-type cell-mediated reaction may be activated, whereas increased expression of IL6, IL10, and IGHG1 supports the involvement of a Th2-type humoral-mediated response at tick bite-sites in cattle infested with at A. americanum. Regression analyses identified strong correlations between factors involved in pattern recognition in tick bite-site biopsies, including associations between TLR4 and IL1alpha, and between IL1alpha and IL1RN. In conclusion, this dissertation reports optimal methodology for gene expression studies in tick-infested cattle and provides preliminary data concerning the underlying mechanisms associated with the immune response in Lone Star tick-infested cattle.

No description available.

In 1994 and 1995, seven cases of Human monocytic ehrlichiosis were reported in Indiana; six cf these were from southern counties. To test whether Ehrlichia cha ffeensis is present in native ticks, adult ticks representing two species, Dermacentor variabilis and Amblyomma americanum were collected in southern Indiana during the first week of May, 1995 and tested by PCR. A total of 510 D. variabilis ticks were collected and placed into 102 pools (5 ticks per pool). A total of 430 adult A. americanum ticks were collected and placed into 88 pools of 5 ticks or less.D. variabilis ticks were used to optimize the isolation of PCR amplifiable DNA and determine the minimum number of bacterial cells detected. A modified CTAB-phenol method permitted the detection of as few as 100 bacterial cells. The optimal amount of isolated DNA for a PCR amplification was determined to be 2.7 pg of total nucleic acid.The 88 pools of adult A. americanum were subjected to DNA isolation, PCR amplification, and Southern analysis to determine the presence of E. chaffeensis bacteria. Using the 16S rRNA gene from E. chaffeensis, with species specific primers Hut and HE3. Of the 88 pools (430 ticks; 21 were determined to be positive for the presence E. chaffeensis bacteria. Thus, minimal field infection rate for adult A. americanum ticks in Southern Indiana was 4.88%. This calculation is based upon the assumption that at least one tick was positive in each positive pool. / Department of Biology

The genomic RNA encoding the structural proteins of louping ill, a tickborne flavivirus, was cloned and sequenced. Sequence comparisons of louping ill envelope protein showed greater homology with tick-borne than mosquito-borne flaviviruses and greater homology with the western than the far eastern subtype of tick-borne encephalitis virus. Louping ill and tick-borne encephalitis viruses are probably varieties of a common tick-borne ancestral virus. The average amino acid sequence diversity between members of the tick-borne serogroup was significantly lower than that of mosquito-borne serogroups, suggesting that tick-borne flaviviruses have been subjected to different evolutionary immune selection pressure from the mosquito-borne viruses. Using the published model of tick-borne encephalitis envelope protein and the derived sequence data on louping ill virus, three discontinuous peptides (amino acids 81-88, 207-212 and 230-234) which may represent critical molecular determinants within the receptor binding site of tick-borne flaviviruses, were identified. These peptides may provide a specific genetic marker for these viruses. Recombinant baculoviruses and vaccinia viruses containing cloned DNA, encoding either the envelope protein or the structural proteins of louping ill virus, were constructed. Glycosylated envelope protein, presented both inside and on the surface of insect and mammalian cells, was expressed by all four recombinant viruses. Differences in antigenic presentation of envelope protein were observed between envelope protein and structural protein constructs as well as between insect cell and mammalian cell expression systems. Despite the expression of epitopes known to elicit neutralizing and protective antibodies when present in authentic antigen, the recombinant envelope protein expressed by either baculovirus or vaccinia virus failed to induce, under the experimental conditions employed, either neutralizing or protective antibodies in both mice and rabbits against louping ill virus. Hence, louping ill envelope protein expressed by baculoviruses and vaccinia viruses was antigenically reactive but immunogenically inert.

Thesis (M.S.)--University of Missouri--Columbia, 2004. / "May, 2004." Typescript. Includes bibliographical references (leaves 35-38). Also issued on the Internet.

Thesis (MSc (Veterinary Tropical Diseases, Veterinary Science))--University of Pretoria, 2008. / Includes bibliographical references. Also available in print format.

Thesis (M.S.)--University of Calif. 1912. / Reprint from the Public health reports, vol. XXVII, no. 36, Sept. 6, 1912. This paper originally appeared in the Military surgeon, vol. XXIX, no. 6, Dec. 1911, p. 631-657, under title, "The problem of Rocky Mountain spotted fever." As republished here the text and bibliography have been amended so as to cover the subject to the present time. cf. p. 3. Bibliography: p. 23-29.

Thesis (M.S.)--University of Missouri--Columbia, 2004. / Typescript. Includes bibliographical references (leaves 35-38). Also issued on the Internet.

This study is focused on characterization of fibrinogen-related proteins (FREPs) from the tick Ixodes ricinus using molecular methods - PCR, cloning, qRT-PCR, RNA interference via dsRNA synthesis and injection, and also pathogen (Borrelia sp.) transmission on animal model.