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Ticks
Published in Jerome Goddard, Public Health Entomology, 2022
Ehrlichiosis and anaplasmosis. Ehrlichia and Anaplasma organisms may be transmitted by ticks as well. They are rickettsia-like bacteria that primarily infect circulating leukocytes. The most common of them, Ehrlichia chaffeensis, the causative agent of human monocytic ehrlichiosis (HME), occurs mostly in the central and southern United States, and infects mononuclear phagocytes in blood and tissues.12 There were 1,799 cases of HME in the United States in 2018.4 A new species of Ehrlichia causing human illness in Minnesota and Wisconsin has recently been recognized.13 Another, Anaplasma (formerly Ehrlichia) phagocytophilum, infects granulocytes and causes human granulocytic anaplasmosis (HGA); it is mostly reported from the upper Midwest and northeastern United States. There were 4,008 cases of HGA in the United States in 2018.4
Encephalitis and Its Mimics in the Critical Care Unit
Published in Cheston B. Cunha, Burke A. Cunha, Infectious Diseases and Antimicrobial Stewardship in Critical Care Medicine, 2020
Patients with rickettsia (particularly Rocky Mountain spotted fever [RMSF]) and ehrlichia/anaplasma (particularly human monocytic and granulocytic ehrlichiosis) infected patients can have severe headaches and prominent mental status changes. In both, the disorder caused by these intracellular organisms probably is less an encephalitis than an infectious vasculitis. Rocky Mountain spotted fever in particular can be associated with significant cerebral edema and stupor. Cerebrospinal fluid typically demonstrates a modest lymphocytic pleocytosis and increased protein; CSF glucose is most often normal. Autopsy studies demonstrate perivascular inflammatory infiltrates and occasionally intravascular thrombi in the brain, pathologic changes that could easily explain the seizures that sometime accompany RMSF. Focal CNS findings are relatively infrequent in patients with these infections, and survivors typically do not have prominent neurologic sequelae. Whether ehrlichia infections have significant neurologic involvement remains unclear—although headaches and alterations of consciousness are described frequently, only a few case reports have described focal brain abnormalities.
Nalidixic Acid and Other Quinolones
Published in 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, Kucers’ The Use of Antibiotics, 2017
Chlamydia trachomatis is resistant to nalidixic acid (Heessen and Muytjens, 1984). Ehrlichia spp. are probably resistant to nalidixic acid; this drug was ineffective in eliminating E. risticii from macrophages in vitro (Rikihisa and Jiang, 1988).
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
The medical and veterinary significance of Ehrlichia sp. strain Delta remains to be demonstrated. However, it is important to mention that A. triste adults are aggressive to humans and domestic mammals as cattle and dogs [16]. Therefore, the potential role of A. triste in the transmission of Ehrlichia agents to humans or domestic animals across its distributional range should be highlighted, even more considering that Ehrlichia sp. strain Delta is phylogenetically related to the zoonotic E. chaffeensis, which is recognized as pathogenic to both humans and animals [40]. The finding of this work plus those data obtained in the last years in South America regarding the circulation of Ehrlichia spp. other than E. canis (i.e. E. minasensis, Ehrlichia sp.strain Córdoba, Ehrlichia sp.strain San Luis, Ehrlichia sp. strain L8 (Iberá), Ehrlichia sp. strain La Dormida, Ehrlichia sp. cf. E. chaffeensis, Ehrlichia sp. clone 15B, Ehrlichia sp. from Didelphis albiventris, Ehrlichia sp. from Cerdocyon thous, Ehrlichia sp. from sloth, Ehrlichia sp. from horse, Ehrlichia sp. strain Jaguar and Ehrlichia sp. strain Delta [5,6,8,11–14,26,27,43,44, this work]), clearly highlight the need to consider as targets these microorganisms when serological, molecular and clinical studies on tick-borne pathogens in humans and domestic and wild mammals are conducted in countries of this continent.
How relevant are in vitro culture models for study of tick-pathogen interactions?
Published in Pathogens and Global Health, 2021
Cristiano Salata, Sara Moutailler, Houssam Attoui, Erich Zweygarth, Lygia Decker, Lesley Bell-Sakyi
Like the Anaplasma spp. covered in the previous section, most strictly tick-transmitted bacterial pathogens are obligately intracellular, and cannot replicate in the extracellular environment. These include other members of the order Rickettsiales – Ehrlichia spp. and Neoehrlichia spp. that form colonies of multiplying bacteria, or morulae, within cytoplasmic vacuoles, and Rickettsia spp. that grow directly in the host cell cytoplasm (Figure 4B). Some examples of the use of tick cell lines as models for study of Ehrlichia and Rickettsia spp. will be reviewed.