Identification of the caustive agent of Human Monocytic Ehrlichiosis in hardbodied ticks in various Missouri counties.

Ehrlichioses are emerging infectious diseases which have become a cause for concern due to their morbidity and mortality among humans and animals, both domestic and wild. Human Monocytic Ehrlichiosis (HME) is a vector-borne disease transmitted through the bite of Ixodid ticks carrying the obligate intraleucocytic bacterium Ehrlichia chaffeensis. E. chaffeensis was identified in 1986 as the causative agent in Human Monocytic Ehrlichiosis, infecting mononuclear phagocytes in blood and tissues. Mortality is estimated at 2-5% within days of the first symptoms. Patients at risk have delayed treatment in addition to being older and/or immunocompromised. Missouri holds the national record for the number of cases (145), three times higher than the next highest state. Missouri is especially vulnerable due to its economy, heavily dependent on farming, as well as the outdoor lifestyles that Missourians enjoy. Three species of ticks, including Amblyomma americanum, Dermacentor variabilis, and Ixodes scapularis were collected from animals as well as from public areas by flagging vegetation in 25 different counties in order to determine areas of greatest risk. Ticks were preserved by freezing, and then processed individually. DNA was extracted from over 450 ticks. Regions of the 16s rRNA gene were amplified in nested reactions. Representative positive testing samples were then sequenced. Among these positives, I. scapularis and A. americanum had noticeably higher positive rates compared to D. variabilis. Data collected from the vectors of HME may result in a more adequate means of control of this infectious disease.

* Lee, J.K. and A. J. Candee. Biology Department, William Woods University.