Resistance of the Tick Dermacentor variabilis (Acari: Ixodidae) Following Challenge with the Bacterium Escherichia coli (Enterobacteriales: Enterobacteriaceae)

• Published in: Journal of medical entomology 2002-03, Vol.39 (2), p.376-383
• Main Authors: Ceraul, S M, Sonenshine, DE, Hynes, W L
• Format: Article
• Language: English
• ISSN: 0022-2585
• DOI: 10.1043/0022-2585(2002)039(0376:ROTTDV)2.0.CO;2

In addition to a soluble response, many invertebrates control bacterial infections by means of phagocytosis or melanotic encapsulation. In some insects, Escherichia coli growth is reported to be inhibited by aggregation/encapsulation. Soluble and phagocytic responses to bacterial challenge have been reported in ticks, but evidence of an aggregation/encapsulation response was reported only for inanimate (araldite) implants. Ticks were challenged by direct inoculation of bacteria into the hemocoel cavity. By plating, no viable E. coli were detected 6 h postinoculation. A direct fluorescence assay (DFA) revealed aggregated bacteria 1 h postinoculation. Furthermore, DFA showed aggregated bacteria at 6, 24, and 48 h postinoculation associated with masses of tissue, presumably of cellular origin, suggesting events similar to those described as nodulation. These findings suggest that encapsulation/nodulation may be an important component of the immune response in ticks.