Clearance of endosymbionts in the tick vector Rhipicephalus sanguineus

Abstract only availableVector-borne diseases reduce livestock production in areas whose human populations are starving, such as the Tsetse belt in Africa. In the United States, people are infected every year with Lyme disease, Rocky Mountain Spotted Fever, and Human Monocytic Ehrlichiosis. A method of controlling vectors, such as ticks, would have many uses. Previous studies have indicated that all ticks of the species Amblyomma americanum are infected with a Coxiella sp. bacterial symbiont. After treatment with the antibiotics rifampin and tetracycline, nymphs and adults were shown to have lower numbers of this symbiont and treatment of engorged adult females was shown to result in decreased fecundity (Zhong et al. 2007). It was speculated that this Coxiella symbiont plays a vital role in tick fitness and female fecundity. The goals of the current experiment are to: demonstrate the presence of the same or similar symbiont in Rhipicephalus sanguineus adults and larvae, demonstrate clearance of the symbiont in larvae after treatment with antibiotics, observe any negative effects on the fecundity of the treated females, and test the acquisition rate of larvae that feed on a carrier of Ehrlichia canis, a pathogen of which ticks are a vector. A Coxiella sp. symbiont was shown in adult and larvae R. sanguineus using PCR. Adult females were then fed with males on dogs to repletion, with several groups receiving different treatments of antibiotics prior to mating. Three of the treatment groups suffered significantly lower fecundity than the control. DNA from the resulting larvae was PCR assayed for symbionts, and the Coxiella symbiont has been found in lower numbers in the larvae of these treated groups. The next phase of the experiment is to feed symbiont cleared or reduced larvae on an E. canis carrier and compare their rate of acquisition to untreated larvae.Dr. Roger W. Stich, Veterinary Pathobiolog

Adding pieces to the monocytic ehrlichiosis puzzle : treatment, etiology and protection with a canine model

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from PDF of title page (University of Missouri--Columbia, viewed on May 31, 2011).Vita.Thesis advisor: Roger William Stich."May 2010"Ph. D. University of Missouri-Columbia 2010.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Infections with Ehrlichia canis cause Canine Monocytic Ehrlichiosis (CME), a disease which causes morbidity and mortality of dogs worldwide. Currently, there are questions in the literature regarding efficacy of treatment, etiology of severe disease and whether previous infections offer protection to dogs when they are challenged. Through careful experimentation it was determined that although treatment with doxycycline successfully ameliorates disease, it is not sufficient to clear bacteria from infected dogs and therefore a different treatment regimen should be explored which would fully clear the bacteria. Furthermore, it was determined that E. canis alone could induce severe acute CME in specific pathogen free dogs. Lastly, dogs were infected with E. canis, treated and then given a homologous challenge. Although the dogs demonstrated less severe signs of disease three out of four had levels of bacteria in their blood higher than what was seen during the initial infection.Includes bibliographical reference