Infection Rates ofAmblyomma americanumandDermacentor variabilisbyEhrlichia chaffeensisandEhrlichia ewingiiin Southwest Missouri

Abstract

Both Ehrlichia chaffeensis and Ehrlichia ewingii are causative agents of human ehrlichiosis. Both pathogens are transmitted to humans through the bite of an infected lone star tick (Amblyomma americanum). Since Missouri has a high incidence of human monocytic ehrlichiosis, we investigated the prevalence of E. chaffeensis- and E. ewingii-infected A. americanum and Dermacentor variabilis (American dog tick) ticks to help assess the relative risk for humans exposed to these vectors. We used a nested polymerase chain reaction assay for the detection of ehrlichial DNA in the collected ticks. Infection rates for both ehrlichial species were calculated from the assay results for each of the tick species. E. chaffeensis was found to be present in 9.8% of adult A. americanum ticks (57 of 579) and 6.7% of D. variabilis ticks (eight of 120). E. ewingii DNA was present at an infection rate of 5.4% in adult A. americanum (31 of 579) and 3.3% of D. variabilis ticks (four of 120). A minimum infection rate for nymph pools of A. americanum was 1.7% for E. chaffeensis and 0.6% for E. ewingii.

Heterogeneous Associations of Ecological Attributes with Tick-Borne Rickettsial Pathogens in a Periurban Landscape

“…A previous study by Steiert and Gilfoy (2002) conducted in the year 2002 across six counties in southwestern Missouri (in relative close proximity to the sampling locations around the city of Pittsburg in the present study) reported infection prevalence for E. chaffeensis and E. ewingii (Table 3), and Berrada et al (2011) assessed infection rates of Rickettsia spp. among A. americanum and D. variabilis ticks in Kansas and Missouri (Table 3).…”

Increasing Incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000–2007

“…17,18 Ehrlichia ewingii may be maintained in a similar enzootic cycle, with deer and domestic dogs proposed as possible reservoir species. [19][20][21] Small mammals are the primary reservoir for A. phagocytophilum , and the vectors Ixodes scapularis (black-legged or deer tick) and Ixodes pacificus (western black-legged tick) maintain A. phagocytophilum prevalence primarily in the northeastern, the upper midwestern, and the Pacific coast regions. 16,17,22,23 Previous surveillance summaries found most cases reported within these areas.…”

Retrospective Study of Tick-Borne Pathogens and Observation of <i>Ehrlichia ewingii / Anaplasma phagocytophilum</i> and Hemotropic <i>Mycoplasma</i> spp. in Dogs’ Blood Films

“…E. ewingii DNA was detected in D. variabilis and Rh. sanguineus [14,[51][52][53][54]. These species and may be some other ticks are more important in other countries such as Brazil and Cameroon where E. ewingii has been detected [26,27].…”