Growth of Ehrlichia canis, the causative agent of canine monocytic ehrlichiosis, in vector and non-vector ixodid tick cell lines

Abstract

Canine monocytic ehrlichiosis is caused by Ehrlichia canis, a small gram-negative coccoid bacterium that infects circulating monocytes. The disease is transmitted by the brown dog tick Rhipicephalus sanguineus s.l. and is acknowledged as an important infectious disease of dogs and other members of the family Canidae worldwide. E. canis is routinely cultured in vitro in the canine monocyte-macrophage cell line DH82 and in non-vector Ixodes scapularis tick cell lines, but not in cells derived from its natural vector. Here we report infection and limited propagation of E. canis in the tick cell line RSE8 derived from the vector R. sanguineus s.l., and successful propagation through six passages in a cell line derived from the experimental vector Dermacentor variabilis. In addition, using bacteria semi-purified from I. scapularis cells we attempted to infect a panel of cell lines derived from non-vector species of the tick genera Amblyomma, Dermacentor, Hyalomma, Ixodes and Rhipicephalus with E. canis and, for comparison, the closely-related Ehrlichia ruminantium, causative agent of heartwater in ruminants. Amblyomma and non-vector Dermacentor spp. cell lines appeared refractory to infection with E. canis but supported growth of E. ruminantium, while some, but not all, cell lines derived from Hyalomma, Ixodes and Rhipicephalus spp. ticks supported growth of both pathogens. We also illustrated and compared the ultrastructural morphology of E. canis in DH82, RSE8 and I. scapularis IDE8 cells. This study confirms that E. canis, like E. ruminantium, is able to grow not only in cell lines derived from natural and experimental tick vectors but also in a wide range of other cell lines derived from tick species not known to transmit this pathogen.

Francisella tularensis novicida infection competence differs in cell lines derived from United States populations of Dermacentor andersoni and Ixodes scapularis

“…3 ). Although identification of the specific mechanisms that allowed for prolonged bacterial levels and reduced tick cell mortality were beyond the scope of this initial study, they are consistent with previous observations that temperature can influence infection success and that intracellular pathogens can dampen virulence to prevent elimination 35 , 36 .…”

The Tick Cell Biobank: A global resource for in vitro research on ticks, other arthropods and the pathogens they transmit

“…This is exemplified by, at one end of the spectrum, the extremely fastidious Anaplasma centrale that only grew in two out of 32 cell lines tested ( Bell-Sakyi et al, 2015b ) and, at the other end, the much more catholic Ehrlichia spp. that grew in almost all tick cell lines tested ( Bell-Sakyi, 2004 ; Cabezas-Cruz et al, 2016 ; Ferrolho et al, 2016 ; L. Bell-Sakyi unpublished observations). Such studies can provide insights into the actual and potential range of possible vector species and the factors governing ability to transmit a particular pathogen, bearing in mind that vector competence is multi-factorial and tick cell lines may not fully represent the phenotypic and functional spectrum of cells and tissues present in the intact tick.…”

“…All species and strains of intracellular bacteria are stored as aliquots of one or more infected tick cell lines in vapour-phase liquid nitrogen. Bacterial species (strain) Host (country of origin) References Anaplasma centrale (Israeli vaccine strain) Bovine (South Africa) Shkap et al (2008) ; Bell-Sakyi et al (2015b) Anaplasma phagocytophilum (Old Sourhope) Sheep (Scotland) Foster and Cameron (1970) ; Woldehiwet et al (2002) Anaplasma phagocytophilum (Perth) Sheep (Scotland) Woldehiwet (2010) Anaplasma phagocytophilum (Harris) Sheep (Scotland) Woldehiwet (2010) Anaplasma phagocytophilum (Feral Goat) Goat (Scotland) Woldehiwet and Horrocks (2005) Anaplasma phagocytophilum (ZW122-05) Sheep (England) Z. Woldehiwet personal communication Anaplasma phagocytophilum (ZW144-05) Bovine (England) Z. Woldehiwet personal communication Anaplasma phagocytophilum (L610) Dog (Germany) Alberdi et al (2015) Ehrlichia canis (Spain 105) Dog (Spain) Zweygarth et al (2014) , Ferrolho et al (2016) . Ehrlichia minasensis (UFMG-EV T ) Rhipicephalus microplus engorged female tick (Brazil) Cabezas-Cruz et al (2016) Ehrlichia ruminantium (Gardel CTVM) Ehrlichia ruminantium (Gardel attenuated) Amblyomma variegatum ticks (Guadeloupe) In vitro culture (originally from A. variegatum t...…”

Efectividad de los métodos diagnósticos para la detección de ehrlichiosis monocítica humana y canina

“…Por otra parte, se ha reportado el aislamiento de E. canis en líneas celulares de garrapatas. Han presentado un porcentaje mayor al 50% de células infectadas las DVE1 (Dermacentor variabilis), IDE8 y ISE6 (Ixodes scapularis) y RAE25 (Rhipicephalus appendiculatus), demostrándose de esta manera su propagación in vitro en líneas celulares de garrapatas no-vectores 36 .…”