Ehrlichia chaffeensis and its interaction with tick salivary glands

Ticks are an ideal example of efficient ecto-parasites that are able to steal blood, a rich source of nutrients, from their vertebrate hosts for prolonged periods of time. The tick life cycle is comprised of egg, larval, nymphal and adult stages. Nymphs are epidemiologically important for disease transmission to the human host. Our experiment is an attempt to develop a weight-based sex differentiation tool for our RNAi and in vitro pathogen infections among the adult females. The relationship between weights of engorged nymphs and their adult sexes in Amblyomma americanum was addressed in this study. Flat nymphs were fed to complete repletion on New Zealand white rabbits, weighed individually and divided into groups based on their weight, and kept until they molted. This suggests that nymphs of both species that become female presumably imbibe more blood than those that became male. To further confirm, we inoculated an obligate intracellular bacterium, Ehrlichia chaffeensis Arkansas strain infected DH82 cells in the heavier engorged nymphs and kept them for molting at 34°C and 90% relative humidity. Freshly molted adults were used to test the E. chaffeensis infection rate. E. chaffeensis genomic DNA was extracted from individual unfed and partially fed midguts and salivary glands. The tissue samples were tested for the presence of E. chaffeensis using nested Polymerase Chain Reaction (PCR). PCR amplified fragments were detected in unfed and partially fed tissues. Our experiment demonstrated successful E. chaffeensis infection of female adult salivary glands for our proposed RNAi studies.