Dermacentor variabilis
Encyclopedia
Dermacentor variabilis, also known as the American dog tick, is a species of tick
that is known to carry bacteria
responsible for several diseases in humans, including Rocky Mountain spotted fever
and tularemia
(Francisella tularensis). It is one of the most well-known hard ticks.
Though D. variabilis may be exposed to Borrelia burgdorferi, the causitive agent of Lyme disease, these ticks are not competent vectors for the transmission of this disease. The primary vector for Borrelia burgdorferi is the deer tick Ixodes scapularis
in Eastern parts of the United States, and Ixodes pacificus
in California and Oregon. Dermacentor variabilis may also carry Anaplasma phagocytophilum
, the causative agent of HGE (human granulocytic ehrlichiosis), and Ehrlichia chaffeensis
, the causative agent of HME (human monocytic ehrlichiosis).
Dermacentor ticks may also induce tick paralysis
by elaboration of a neurotoxin that induces rapidly progressive flaccid quadriparesis
similar to Guillain-Barré syndrome
. The neurotoxin prevents presynaptic release of acetylcholine from neuromuscular junctions.
Tick
Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...
that is known to carry bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
responsible for several diseases in humans, including Rocky Mountain spotted fever
Rocky Mountain spotted fever
Rocky Mountain spotted fever is the most lethal and most frequently reported rickettsial illness in the United States. It has been diagnosed throughout the Americas. Some synonyms for Rocky Mountain spotted fever in other countries include “tick typhus,” “Tobia fever” , “São Paulo fever” or “febre...
and tularemia
Tularemia
Tularemia is a serious infectious disease caused by the bacterium Francisella tularensis. A Gram-negative, nonmotile coccobacillus, the bacterium has several subspecies with varying degrees of virulence. The most important of those is F...
(Francisella tularensis). It is one of the most well-known hard ticks.
Though D. variabilis may be exposed to Borrelia burgdorferi, the causitive agent of Lyme disease, these ticks are not competent vectors for the transmission of this disease. The primary vector for Borrelia burgdorferi is the deer tick Ixodes scapularis
Ixodes scapularis
Ixodes scapularis is commonly known as the deer tick or blacklegged tick , and in some parts of the USA as the bear tick. It is a hard-bodied tick of the eastern and northern Midwestern United States...
in Eastern parts of the United States, and Ixodes pacificus
Ixodes pacificus
Ixodes pacificus, the Western blacklegged tick, is a species of Ixodes, a parasitic tick found on the western coast of North America. It is the principal vector of Lyme Disease in that region....
in California and Oregon. Dermacentor variabilis may also carry Anaplasma phagocytophilum
Anaplasma phagocytophilum
Anaplasma phagocytophilum is a gram-negative bacterium that is unusual in its tropism to neutrophils...
, the causative agent of HGE (human granulocytic ehrlichiosis), and Ehrlichia chaffeensis
Ehrlichia chaffeensis
Ehrlichia chaffeensis is a species of rickettsiales bacteria.It is named for Fort Chaffee.It is the causative agent of human monocytic ehrlichiosis....
, the causative agent of HME (human monocytic ehrlichiosis).
Dermacentor ticks may also induce tick paralysis
Tick paralysis
Tick paralysis is the only tick-borne disease that is not caused by an infectious organism. The illness is caused by a neurotoxin produced in the tick's salivary gland. After prolonged attachment, the engorged tick transmits the toxin to its host...
by elaboration of a neurotoxin that induces rapidly progressive flaccid quadriparesis
Flaccid paralysis
Flaccid paralysis is a clinical manifestation characterized by weakness or paralysis and reduced muscle tone without other obvious cause .-Polio:...
similar to Guillain-Barré syndrome
Guillain-Barré syndrome
Guillain–Barré syndrome , sometimes called Landry's paralysis, is an acute inflammatory demyelinating polyneuropathy , a disorder affecting the peripheral nervous system. Ascending paralysis, weakness beginning in the feet and hands and migrating towards the trunk, is the most typical symptom...
. The neurotoxin prevents presynaptic release of acetylcholine from neuromuscular junctions.
External links
- Ohio State University Extension Fact Sheet
- Illinois photographs
- Iowa tick images
- American dog tick on the University of FloridaUniversity of FloridaThe University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...
/ Institute of Food and Agricultural SciencesInstitute of Food and Agricultural SciencesThe University of Florida’s Institute of Food and Agricultural Sciences is a federal-state-county partnership dedicated to developing knowledge in agriculture, human and natural resources, and the life sciences, and enhancing and sustaining the quality of human life by making that information...
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