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

Factors associated with Anaplasma spp. seroprevalence among dogs in the United States

Background Dogs in the United States are hosts to a diverse range of ticks and tick-borne pathogens, including A. phagocytophilum, an important emerging canine and human pathogen. Previously, a Companion Animal Parasite Council (CAPC)-sponsored workshop proposed factors purported to be associated with the infection risk for tick-transmitted pathogens in dogs in the United States, including climate conditions, socioeconomic characteristics, local topography, and vector distribution. Methods Approximately four million test results from routine veterinary diagnostic tests from 2011–2013, which were collected on a county level across the contiguous United States, are statistically analyzed with the proposed factors via logistic regression and generalized estimating equations. Spatial prevalence maps of baseline Anaplasma spp. prevalence are constructed from Kriging and head-banging smoothing methods. Results All of the examined factors, with the exception of surface water coverage, were significantly associated with Anaplasma spp. prevalence. Overall, Anaplasma spp. prevalence increases with increasing precipitation and forestation coverage and decreases with increasing temperature, population density, relative humidity, and elevation. Interestingly, socioeconomic status and deer/vehicle collisions were positively and negatively correlated with canine Anaplasma seroprevalence, respectively. A spatial map of the canine Anaplasma hazard is an auxiliary product of the analysis. Anaplasma spp. prevalence is highest in New England and the Upper Midwest. Conclusions The results from the two posited statistical models (one that contains an endemic areas assumption and one that does not) are in general agreement, with the major difference being that the endemic areas model estimates a larger prevalence in Western Texas, New Mexico, and Colorado. As A. phagocytophilum is zoonotic, the results of this analysis could also help predict areas of high risk for human exposure to this pathogen

Quantitative Factors Proposed to Influence the Prevalence of Canine Tick-Borne Disease Agents in the United States

The Companion Animal Parasite Council hosted a meeting to identify quantifiable factors that can influence the prevalence of tick-borne disease agents among dogs in North America. This report summarizes the approach used and the factors identified for further analysis with mathematical models of canine exposure to tick-borne pathogens

Targeting Tick-Pathogen-Host Interactions

Comparative Medicine - OneHealth and Comparative Medicine Poster SessionTicks transmit the majority of vector-borne diseases of human beings in the USA and of domestic animals worldwide. Among these, tick-borne rickettsial pathogens cause at least four important tick-borne zoonoses in the USA, and two of the five major vector- borne diseases of cattle worldwide. Notably, five of the aforementioned zoonotic and bovine diseases are endemic to Missouri. Tick-borne diseases of humans are zoonotic, and dogs are also naturally exposed to most of the etiologic agents of such maladies, suggesting potential roles of canine sentinels, reservoirs and models for tick-borne zoonoses. Our group utilizes canine ehrlichiosis (Ehrlichia canis and E. chaffeensis) and bovine anaplasmosis (Anaplasma marginale) models to better understand mechanisms of rickettsial infection of both acarine and mammalian hosts. Ticks used for these projects include Rhipicephalus sanguineus, Dermacentor variabilis, D. andersoni, Amblyomma americanum, A. maculatum and Ixodes scapularis. Projects currently underway include mechanisms responsible for rickettsial manipulation of host cell actin, and strategies that could lead to interference with tick acquisition and transmission of infections. In addition to the infectious cycles of these agents, we are also interested in pathogen interactions with the mammalian host, including the immunology and pathology of anaplasmosis and ehrlichiosis. These studies are expected to lead to better understanding of immune responses associated with different phases of ehrlichiosis, influence of vector feeding on biological and clinical outcomes of infection, immunoprophylaxis, and risk factors for exacerbation of clinical disease. The University of Missouri provides an optimal environment for this work, because i) MU has Veterinary, Medical and Agricultural colleges on the same campus; ii) MU has outstanding nucleic acid, proteomics, flow cytomety and microscopy (both fluorescence and electron) core facilities; iii) almost every tick-borne disease enzootic to the USA is in Missouri, thus allowing local access to diagnostic specimens from naturally infected hosts; iv) MU has established graduate programs in infectious disease research, pathobiology and comparative medicine; v) MU has BSL2 facilities to investigate tick-borne infections of dogs and cattle, which will soon be expanded with construction of a new Animal Resource Center; and vi) MU is home to the Missouri Regional Biocontainment Laboratory, for which an expansion of facilities is anticipated for investigation of tick-transmission of zoonotic BSL3 agents among dogs (e.g., Rickettsia rickettsii, Coxiella burnetii and Francisella tularensis). Our current capabilities center on large animal transmission, infection and disease models for anaplasmosis and ehrlichiosis. Mouse, guinea pig and rabbit models are also possible for certain tick and pathogen species. Technical skills include tick infestation of dogs and cattle, qualitative and quantitative PCR assay development and implementation, monitoring of clinical and hematologic parameters, and characterization of protective and pathogenic mechanisms with immunological and molecular methods. We are interested in opportunities to test new products designed to interfere with tick-pathogen-host interactions, and opportunities to investigate novel approaches for diagnosis or alleviation of ehrlichiosis and anaplasmosis

Observing How Glutathione and S-Hexyl Glutathione Bind to Glutathione S-Transferase from Rhipicephalus (Boophilus) microplus

Rhipicephalus (Boophilus) microplus is one of the most widespread ticks causing a massive loss to livestock production. The long-term use of acaracides rapidly develops acaracide resistance. In R. microplus, enhancing the metabolic activity of glutathione S-transferase (RmGST) is one of the mechanisms underlying acaracide resistance. RmGST catalyzes the conjugation of glutathione (GSH) to insecticides causing an easy-to-excrete conjugate. The active RmGST dimer contains two active sites (hydrophobic co-substrate binding site (H-site) and GSH binding site (G-site)) in each monomer. To preserve the insecticide efficacy, s-hexyl glutathione (GTX), a GST inhibitor, has been used as a synergist. To date, no molecular information on the RmGST-GSH/GTX complex is available. The insight is important for developing a novel RmGST inhibitor. Therefore, in this work, molecular dynamics simulations (MD) were performed to explore the binding of GTX and GSH to RmGST. GSH binds tighter and sits rigidly inside the G-site, while flexible GTX occupies both active sites. In GSH, the backbone mainly interacts with W8, R43, W46, K50, N59, L60, Q72, and S73, while its thiol group directs to Y7. In contrast, the aliphatic hexyl of GTX protrudes into the H-site and allows a flexible peptide core to form various interactions. Such high GTX flexibility and the protrusion of its hexyl moiety to the H-site suggest the dual role of GTX in preventing the conjugation reaction and the binding of acaracide. This insight can provide a better understanding of an important insecticide-resistance mechanism, which may in turn facilitate the development of novel approaches to tick control