Ehrlichia ruminantium grows in cell lines from four ixodid tick genera

Area of Science:

• Veterinary Entomology
• Microbiology
• Cell Biology

Background:

• Ehrlichia ruminantium (formerly Cowdria ruminantium) is a significant rickettsial pathogen affecting ruminants.
• The ability of E. ruminantium to infect and replicate in various tick cell lines is crucial for understanding its transmission and for developing control strategies.

Purpose of the Study:

• To assess the susceptibility of continuous tick cell lines to infection with E. ruminantium.
• To determine if E. ruminantium can be cultured in cell lines derived from ticks other than the natural vector genus, Amblyomma.

Main Methods:

• Inoculation of twelve tick cell lines (from Amblyomma variegatum, Boophilus decoloratus, Boophilus microplus, Hyalomma anatolicum anatolicum, Ixodes scapularis, Ixodes ricinus, and Rhipicephalus appendiculatus) with five isolates of E. ruminantium.
• Monitoring for continuous or finite growth of the pathogen within the cell lines at temperatures ranging from 28°C to 37°C.
• Attempting to re-establish E. ruminantium isolates in a bovine endothelial cell line (BPC) after prolonged maintenance in tick cells.

Main Results:

• Continuous growth of E. ruminantium was established in Ixodes scapularis, Ixodes ricinus, and Amblyomma variegatum cell lines.
• The pathogen was successfully transferred from these lines to Boophilus decoloratus, Boophilus microplus, and Rhipicephalus appendiculatus cell lines.
• Hyalomma anatolicum anatolicum cells did not support E. ruminantium infection, while all five isolates grew in at least one tick cell line.

Conclusions:

• Ehrlichia ruminantium is not restricted to growth in cells from its natural Amblyomma tick vectors.
• The study demonstrates the potential of various tick cell lines for continuous in vitro cultivation of E. ruminantium.
• These findings have implications for tick-borne disease research and diagnostics.