All Posts Tagged With: "Ehrlichia chaffeensis"

Link: http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=21279705&retmode=ref&cmd=prlinks

Excerpt:

Human ehrlichiosis is the term for a collection of tick-borne diseases
caused primarily by obligate intracellular bacteria of the Ehrlichia
species.
Ehrlichiosis is characterized by a mild to severe illness, with
approximately 3-5% of cases proving fatal despite receiving appropriate
care. This report presents the case of a 60 year-old woman who was found
collapsed and unresponsive in her home after an indeterminate time; possibly
for up to 48 h.
Despite rigorous resuscitative care and antibiotic treatment, the patient
lapsed into multi-organ failure and died. Subsequent analysis by microscopic
examination, PCR and immunohistochemistry revealed the patient died from an
infection of Ehrlichia chaffeensis. Clinicians and pathologists must be
aware of this emergent disease in order to make a timely and appropriate
diagnosis.
Discussion of the patient’s clinical, laboratory and autopsy findings as
well as treatment of Ehrlichia chaffeensis infections is presented.

Excerpt:

Because tick-borne diseases are becoming increasingly important throughout the world, monitoring their causative agents in wildlife may serve as a useful indicator of potential human exposure. We assessed the presence of known and putative zoonotic, tick-borne agents in four wildlife species in Mississippi. Animals were tested for exposure to or infection with Ehrlichia chaffeensis, Ehrlichia ewingii, Borrelia lonestari, Rickettsia spp.,Anaplasma phagocytophilum, and Francisella tularensis

. Whole blood and serum were tested from white-tailed deer (WTD; Odocoileus virginianus) and feral swine (Sus scrofa); serum was tested from raccoons (Procyon lotor) and opossums (Didelphis virginiana). We used polymerase chain reaction to detect all agents in blood, whereas an indirect fluorescent antibody assay was used to detect antibodies to E. chaffeensis, B. lonestari, and Rickettsia parkeri (spotted fever group rickettsiae) antigens in serum.

Excerpt:

Human monocytotropic ehrlichiosis is caused by Ehrlichia chaffeensis, a Gram-negative bacterium lacking lipopolysaccharide. We have shown that fatal murine ehrlichiosis is associated with CD8(+)T cell-mediated tissue damage, tumor necrosis factor-alpha, and interleukin (IL)-10 overproduction, and CD4(+)Th1 hyporesponsiveness. In this study, we examined the relative contributions of natural killer (NK) and NKT cells in Ehrlichia-induced toxic shock. Lethal ehrlichial infection in wild-type mice induced a decline in NKT cell numbers, and late expansion and migration of activated NK cells to the liver, a main infection site that coincided with development of hepatic injury. The spatial and temporal changes in NK and NKT cells in lethally infected mice correlated with higher NK cell cytotoxic activity, higher expression of cytotoxic molecules such as granzyme B, higher production of interferon-gamma and tumor necrosis factor-alpha, increased hepatic infiltration with CD8alphaCD11c(+) dendritic cells and CD8(+)T cells, decreased splenic CD4(+)T cells, increased serum concentrations of IL-12p40, IL-18, RANTES, and monocyte chemotactic protein-1, and elevated production of IL-18 by liver mononuclear cells compared with nonlethally infected mice. Depletion of NK cells prevented development of severe liver injury, decreased serum levels of interferon-gamma, tumor necrosis factor-alpha, and IL-10, and enhanced bacterial elimination. These data indicate that NK cells promote immunopathology and defective anti-ehrlichial immunity, possibly via decreasing the protective immune response mediated by interferon-gamma producing CD4(+)Th1 and NKT cells.

Full article: http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=20513551&retmode=ref&cmd=prlinks

Excerpt:

Human ehrlichiosis and anaplasmosis are acute febrile tick-borne
diseases caused by various members of the genera Ehrlichia and
Anaplasma (Anaplasmataceae).
Human monocytotropic ehrlichiosis has become one of the most
prevalent life-threatening tick-borne disease in the United
States. Ehrlichiosis and anaplasmosis are becoming more
frequently diagnosed as the cause of human infections, as animal
reservoirs and tick vectors have increased in number and humans
have inhabited areas where reservoir and tick populations are
high.
Ehrlichia chaffeensis, the etiologic agent of human
monocytotropic ehrlichiosis (HME), is an emerging zoonosis that
causes clinical manifestations ranging from a mild febrile
illness to a fulminant disease characterized by multiorgan system
failure. Anaplasma phagocytophilum causes human granulocytotropic
anaplasmosis (HGA), previously known as human granulocytotropic
ehrlichiosis. This article reviews recent advances in the
understanding of ehrlichial diseases related to microbiology,
epidemiology, diagnosis, pathogenesis, immunity, and treatment of
the 2 prevalent tick-borne diseases found in the United States,
HME and HGA.

Excerpt:

In this study, we evaluated Amblyomma americanum (lone star tick)
in Mississippi for the presence of Ehrlichia chaffeensis,
causative agent of human monocytic ehrlichiosis; Ehrlichia
ewingii, causative agent of human and canine granulocytic
ehrlichiosis; Borrelia lonestari, putative agent of southern
tick-associated rash illness; Francisella tularensis, the agent
of tularemia; and Rickettsia spp., particularly R. amblyommii, a
suspected pathogen. We collected adult A. americanum from four
regions of Mississippi: Northeast, Northwest, Southeast, and
East. Of the ticks collected, 192 were dissected and DNA was
extracted for nested polymerase chain reaction (PCR) assays to
detect the above bacteria. In all, 3% of tick extracts had
evidence of Borrelia sp., 4% for E. chaffeensis, 6% for E.
ewingii, and 44% for a Rickettsia species. As determined by
sequencing, most Rickettsia spp. were R. amblyommii. In addition,
extracts from 42 pools (total of 950) of larval A. americanum
collected in Southwest Mississippi were tested for the presence
of E. chaffeensis and Rickettsia species. Of these extracts from
pools, nine of 37 (24%) were PCR positive for a Rickettsia sp.,
most often, R. amblyommii; none had evidence of E. chaffeensis,
supporting the ability of lone star ticks to transovarially
transmit R. amblyommii, but not E. chaffeensis. This study
demonstrates E.

Rates of infection of Amblyomma americanum (L.) by Ehrlichia chaffeensis were
compared in 100 ticks collected from sites in each of four states: Indiana,
North Carolina, Kentucky, and Mississippi. The overall infection rates were
similar among sites, ranging from 1 to 4%. Because pathogenic differences may
exist between E. chaffeensis strains, nested polymerase chain reaction (PCR)
amplification of the variable-length PCR target (VLPT), and sequencing of the
amplicons were performed to differentiate between strains. The most common
infecting strains at all sites exhibited a repeat profile of 1,2,3,4
(corresponding to the Arkansas/Jax/Osceola and Liberty strains). To determine
whether the minimum infection rates (MIRs) or the most common infecting strain
were changing over time in southern Indiana sites, 2765 ticks from six counties
in 2000 and 837 ticks from seven counties in 2004 also were examined in pools of
five ticks per pool. The MIRs for 2000 and 2004 were 3.5 and 4.2% respectively,
suggesting that the overall MIRs remained low. At two sites, in Pike and
Harrison counties, however, infection rates more than doubled from 2000 to 2004
(7 to 16% and 0.3 to 2.7% respectively). Across all sites, the most common
infecting strains (Arkansas/Jax/Osceola and Liberty) did not significantly
change (68% in 2000; 79% in 2004). Continued