Detection of Vector-Borne Agents in Lone Star Ticks, <I>Amblyomma americanum</I> (Acari: Ixodidae), From Mississippi

Abstract

In this study, we evaluated Amblyomma americanum (lone star tick) in Mississippi for the presence of Ehrlichia chaffeensis, causative agent of human monocytic ehrlichiosis; Ehrlichia ewingii, causative agent of human and canine granulocytic ehrlichiosis; Borrelia lonestari, putative agent of southern tick-associated rash illness; Francisella tularensis, the agent of tularemia; and Rickettsia spp., particularly R. amblyommii, a suspected pathogen. We collected adult A. americanum from four regions of Mississippi: Northeast, Northwest, Southeast, and East. Of the ticks collected, 192 were dissected and DNA was extracted for nested polymerase chain reaction (PCR) assays to detect the above bacteria. In all, 3% of tick extracts had evidence of Borrelia sp., 4% for E. chaffeensis, 6% for E. ewingii, and 44% for a Rickettsia species. As determined by sequencing, most Rickettsia spp. were R. amblyommii. In addition, extracts from 42 pools (total of 950) of larval A. americanum collected in Southwest Mississippi were tested for the presence of E. chaffeensis and Rickettsia species. Of these extracts from pools, nine of 37 (24%) were PCR positive for a Rickettsia sp., most often, R. amblyommii; none had evidence of E. chaffeensis, supporting the ability of lone star ticks to transovarially transmit R. amblyommii, but not E. chaffeensis. This study demonstrates E. chaffeensis, E. ewingii, "B. lonestari", and R. amblyommii in A. americanum by PCR for the first time in Mississippi. Understanding the prevalence and epidemiology of these agents in Mississippi should increase awareness of tick-borne disease in the medical community.

Ticks infesting dogs and cats in North America: Biology, geographic distribution, and pathogen transmission

“…Transovarial transmission of E. chaffeensis in A. americanum does not appear to take place ( Long et al, 2003 ). Numerous publications exist reporting the presence of E. chaffeensis and E. ewingii DNA in A. americanum throughout the geographic range of the tick, and prevalence generally ranges from <1.0% to approximately 10% ( Anderson et al, 1993 ; Lockhart et al, 1997 ; Yu et al, 1997 ; Burket et al, 1998 ; Murphy et al, 1998 ; Roland et al, 1998 ; Steiner et al, 1999 ; Ijdo et al, 2000 ; Irving et al, 2000 ; Whitlock et al, 2000 ; Wolf et al, 2000 ; Stromdahl et al, 2001 ; Steiert and Gilfoy, 2002 ; Goddard et al, 2003 ; DeShields et al, 2004 ; Long et al, 2004 ; Mixson et al, 2004 ; Varela et al, 2004a ; Schulze et al, 2005 ; Mixson et al, 2006 ; Castellaw et al, 2010 ; Cohen et al, 2010 ; Yabsley, 2010 ; Schulze et al, 2011 ; Fritzen et al, 2011 ; Fitak et al, 2014 ; Gaines et al, 2014 ; Maegli et al, 2016 ; Sayler et al, 2016 ; Simpson et al, 2019 ) depending on experimental design, detection methodology, and sample size.…”