Monday, December 10, 2007 - 8:53 AM

Rickettsia rickettsii and Francisella tularensis found in ticks collected from Arkansas pets

Rebecca T Trout, RTrout@uark.edu1, C Dayton Steelman, DSteelm@uark.edu1, Allen Szalanski, Aszalan@uark.edu1, and Phillip Williamson, phwilliam@hsc.unt.edu2. (1) University of Arkansas, Entomology, 319 Agri Bldg, 1 University of Arkansas, Fayetteville, AR, (2) University of North Texas Health Science Center, Department of Pathology and Human Identification, 3500 Camp Bowie Blvd, Ft. Worth, TX

Ticks vector pathogenic bacteria including Rickettsia rickettsii (Rocky Mountain Spotted fever), and Francisella tularensis (Tularemia). Rickettsia rickettsii is the most severe and frequently reported rickettsial illness in the United States, while Francisella tularensis is commonly septic but can also be airborne. In Arkansas, tick-borne pathogens are commonly misdiagnosed and underreported. Consequently, we examined ticks collected from Arkansas pet animals for the presence of each bacterium. Practicing veterinarians removed ticks from pets, stored the ticks in 100% ethanol vials, and shipped the collections to the University of Arkansas. Tick DNA was extracted using Qiagen DNEasy Insect kits and yielded tick genomic DNA, host genomic DNA, and potential bacteria genomic DNA. Tick DNA extractions underwent polymerase chain reactions (PCR) specific to each bacterium and were visualized with gel electrophoresis. Additionally, veterinarians collected a small amount of blood from each host and stored the blood samples on respectively labeled FTA filter paper cards. FTA cards were returned with the tick collections. Blood stored on the FTA cards also underwent DNA extraction using the Whatman Protocol and extracted DNA underwent PCR for each specific bacterium. Positive samples were verified through genetic sequencing at the DNA Identification Laboratory at the University of North Texas. Veterinarians sent over 600 ticks collected from more than 100 animals. Most of the ticks were Amblyomma americanum, and 25% of tested positive for a rickettsial species. Few Francisella species were detected. Interestingly, few pet animals tested positive for Rickettsia species and none tested positive for Francisella species.

Species 1: Acari Ixodidae Amblyomma americanum (lone star tick)