Perpetuation of the agent of human granulocytic ehrlichiosis in a deer tick-rodent cycle.

TLDR

Cotransmission of diverse pathogens by the aggressive deer tick may uniquely impact public health in endemic areas. A human‑derived strain of Ehrlichia was maintained in mice, transmitted by deer ticks to nymphs, detected in tick salivary glands and field ticks, and white‑footed mice served as reservoirs, with about 10 % of host‑seeking ticks infected and 20 % of those also carrying Lyme spirochetes.

Abstract

A human-derived strain of the agent of human granulocytic ehrlichiosis, a recently described emerging rickettsial disease, has been established by serial blood passage in mouse hosts. Larval deer ticks acquired infection by feeding upon such mice and efficiently transmitted the ehrlichiae after molting to nymphs, thereby demonstrating vector competence. The agent was detected by demonstrating Feulgen-positive inclusions in the salivary glands of the experimentally infected ticks and from field-derived adult deer ticks. White-footed mice from a field site infected laboratory-reared ticks with the agent of human granulocytic ehrlichiosis, suggesting that these rodents serve as reservoirs for ehrlichiae as well as for Lyme disease spirochetes and the piroplasm that causes human babesiosis. About 10% of host-seeking deer ticks were infected with ehrlichiae, and of these, 20% also contained spirochetes. Cotransmission of diverse pathogens by the aggressively human-biting deer tick may have a unique impact on public health in certain endemic sites.