Figure. Agarose gel electrophoresis of PCR products amplified with Ehrlichia chaffeensis (Ec) variable-length PCR target primers. Rc, Rickettsia conorii (negative control). The sources of DNA templates used for amplification are Amblyomma parvum ticks collected from different hosts: A) 1–5 humans; B) 1 dog, 2 foxes, 3–6 cattle, 7–8 goats. Variable amplicon size represents different genotypes that result from differences in the number of tandem repeats in the 5′ end of the variable-length PCR target; PCR products’ sizes range from 500 bp to 600 bp.