Comparative aspects of the tick–host relationship: immunobiology, genomics and proteomics
G. F. Wiegertjes, G. Flik in Host-Parasite Interactions, 2004
Ixodid ticks also transmit Ehrlichia species, which are Gram-negative intracellular organisms responsible for cases of HGE and also human monocytic ehrlichiosis (HME). Ehrlichia chaffeensis and Ehrlichia ewingii have been identified as the agents of HME, while Anaplasma phagocytophilum is responsible for HGE (Dumler and Bakken, 1998; Telford et al., 1996). Most cases of HME have been shown to occur in areas where the metastriate Amblyomma americanum (Lone Star Tick) predominates although this illness has also been detected within the geographic distribution of the American dog tick, Dermacentor variabilis. These two species of metastriate ticks are also known to transmit spotted fever, a disease caused by obligate intracellular bacteria belonging to the genus Rickettsia, and tularaemia, an illness caused by the Gram-negative coccobacillus Francisella tularensis. In addition to tularaemia, the Rocky Mountain wood tick Dermacentor andersoni transmits Rickettsia rickettsii (spotted fever), and the Colorado tick fever virus.
Doxycycline
M. Lindsay Grayson, Sara E. Cosgrove, Suzanne M. Crowe, M. Lindsay Grayson, William Hope, James S. McCarthy, John Mills, Johan W. Mouton, David L. Paterson in Kucers’ The Use of Antibiotics, 2017
This is a tick-borne infection caused by small obligate intracellular bacteria of the genus Ehrlichia. These organisms proliferate within white blood cells, with Anaplasma phagocytophilum and Ehrlichia ewingii organisms invading neutrophils, and with Ehrlichia chaffensis organisms infecting human monocytes. Severe infection and mortality are associated with delays in diagnosis and treatment. The treatment of choice is doxycycline, administered for 5 to 14 days (Dumler et al., 2007). Hemophagocytic lymphohistiocytosis (HLH) is sometimes related to ehrlichiosis (Otrock et al., 2015). This severe clinical syndrome responds to doxycycline. It parallels the HLH that arises from other infections and generally resolves with treatment of the underlying disease. The absence of proven alternative antimicrobial regimens and the necessity for prompt empirical therapy mandate doxycycline treatment in all patients with suspected ehrlichiosis, including children < 8 years of age (Dumler et al., 2007). Concomitant Ixodes-borne pathogens including those that cause Lyme disease and tick-borne encephalitis require diagnostic and management considerations.
Ticks
Gail Miriam Moraru, Jerome Goddard in The Goddard Guide to Arthropods of Medical Importance, Seventh Edition, 2019
Goddard and Varela-Stokes114 provided a detailed review of the disease potential of this species. It transmits the pathogen of tularemia to humans; it is a known vector of the agent of human ehrlichiosis (Ehrlichia chaffensis) and is reported to rarely transmit the agent of Rocky Mountain spotted fever (RMSF). Borrelia species spirochetes (but not true Lyme disease agent) have been recovered from this species.115 This tick is also found naturally infected with heartland virus (pathogenic), Rickettsia amblyommatis (mostly nonpathogenic),116,117Rickettsia parkeri (pathogenic),118,119 and Ehrlichia ewingii (pathogenic).120 Indirectly, this species may cause red meat allergy in humans.121
A novel Ehrlichia strain (Rickettsiales: Anaplasmataceae) detected in Amblyomma triste (Acari: Ixodidae), a tick species of public health importance in the Southern Cone of America
Published in Pathogens and Global Health, 2020
Gabriel L. Cicuttin, María N. De Salvo, Paula Díaz Pérez, Darío Silva, María L. Félix, José M. Venzal, Santiago Nava
Bacteria of the genus Ehrlichia (Rickettsiales: Anaplasmataceae) are alpha-proteobacterial, tick-transmitted, obligate intracellular parasites with medical and veterinary importance that can infect monocytes, neutrophils, endothelial cells or neutrophils [1,2]. Formally there are six recognized species: Ehrlichia canis, Ehrlichia chaffeensis, Ehrlichia ewingii, Ehrlichia ruminantium, Ehrlichia muris and Ehrlichia minasensis, but different strains of putative novel species of Ehrlichia have been molecularly detected in the last 20 years [1–14, among others].
Related Knowledge Centers
- Alphaproteobacteria
- Anaplasma
- Bacteria
- Ehrlichia
- Ehrlichia Canis
- Ehrlichia Chaffeensis
- Wolbachia
- Rickettsiales
- Pseudomonadota
- Ehrlichiaceae