''Dermacentor variabilis'', also known as the American dog tick or wood tick, is a species of

tick Ticks are parasitic arachnids of the order Ixodida. They are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, and species, but can become larger when engorged. Ticks a ...

that is known to carry

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

responsible for several diseases in humans, including

Rocky Mountain spotted fever Rocky Mountain spotted fever (RMSF) is a bacterial disease spread by ticks. It typically begins with a fever and headache, which is followed a few days later with the development of a rash. The rash is generally Petechial rash, made up of small s ...

and

tularemia Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium '' Francisella tularensis''. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat ...

(''Francisella tularensis''). It is one of the best-known

hard tick The Ixodidae are the family of hard ticks or scale ticks, one of the three families of ticks, consisting of 771 species, . They are known as 'hard ticks' because they have a scutum or hard shield, which the other major family of ticks, the 'sof ...

s. Diseases are spread when it sucks blood from the host. It may take several days for the host to experience symptoms. Though ''D. variabilis'' may be exposed to ''

Borrelia burgdorferi ''Borrelia burgdorferi'' is a bacterial species of the spirochete class in the genus '' Borrelia'', and is one of the causative agents of Lyme disease in humans. Along with a few similar genospecies, some of which also cause Lyme disease, it m ...

'', the causative agent of

Lyme disease Lyme disease, also known as Lyme borreliosis, is a tick-borne disease caused by species of ''Borrelia'' bacteria, Disease vector, transmitted by blood-feeding ticks in the genus ''Ixodes''. It is the most common disease spread by ticks in th ...

, these ticks are not competent vectors for the transmission of this disease. The primary vectors for ''B. burgdorferi'' are the deer ticks ''

Ixodes scapularis ''Ixodes scapularis'' is a hard-bodied tick found in much of the eastern half of North America. It is commonly known as the deer tick, owing to its habit of parasitizing the white-tailed deer. It is also sometimes known as the black-legged tick ( ...

'' in eastern parts of the United States, ''

Ixodes pacificus ''Ixodes pacificus'', the western black-legged tick, is a species of tick found on the western coast of North America. The western black-legged tick is a hard tick, i.e., a member of the family Ixodidae. The larvae and nymphs typically feed on li ...

'' in California and Oregon, and ''

Ixodes ricinus ''Ixodes ricinus'', the castor bean tick, is a chiefly European species of hard-bodied tick. It may reach a length of when engorged with a blood meal, and can transmit both bacterial and viral pathogens such as the causative agents of Lyme disea ...

'' in Europe. ''D. variabilis'' may also carry ''

Anaplasma phagocytophilum ''Anaplasma phagocytophilum'' (formerly ''Ehrlichia phagocytophilum'') is a Gram-negative bacterium that is unusual in its tropism to neutrophils. It causes anaplasmosis in sheep and cattle, also known as tick-borne fever and pasture fever, an ...

'', the causative agent of

human granulocytic anaplasmosis Human granulocytic anaplasmosis (HGA) is a tick-borne, infectious disease caused by '' Anaplasma phagocytophilum'', an obligate intracellular bacterium that is typically transmitted to humans by ticks of the '' Ixodes ricinus'' species complex, ...

, and ''

Ehrlichia chaffeensis ''Ehrlichia chaffeensis'' is an obligate intracellular, Gram-negative species of Rickettsiales bacteria. It is a zoonotic pathogen transmitted to humans by the lone star tick (''Amblyomma americanum''). It is the causative agent of human monoc ...

'', the causative agent of human monocytic

ehrlichiosis Ehrlichiosis is a tick-borne bacterial infection, caused by bacteria of the family Anaplasmataceae, genera '' Ehrlichia'' and '' Anaplasma''. These obligate intracellular bacteria infect and kill white blood cells. The average reported annua ...

. ''Dermacentor'' ticks may also induce

tick paralysis Tick paralysis is a type of paralysis caused by specific types of ticks. Unlike tick-borne diseases caused by infectious organisms, the illness is caused by a neurotoxin produced in the tick's salivary gland. After prolonged attachment, the en ...

by elaboration of a

neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function ...

that induces rapidly progressive flaccid quadriparesis similar to

Guillain–Barré syndrome Guillain–Barré syndrome (GBS) is a rapid-onset Paralysis, muscle weakness caused by the immune system damaging the peripheral nervous system. Typically, both sides of the body are involved, and the initial symptoms are changes in sensation ...

. The neurotoxin prevents presynaptic release of

acetylcholine Acetylcholine (ACh) is an organic compound that functions in the brain and body of many types of animals (including humans) as a neurotransmitter. Its name is derived from its chemical structure: it is an ester of acetic acid and choline. Par ...

from

neuromuscular junctions A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. Muscles require innervation to ...

Life cycle

The life cycle of ticks can vary depending on the species. Most ticks go through four stages: egg, six-legged larva, eight-legged nymph, and adult. After hatching from the egg, a tick must obtain a blood meal at every stage to survive. Ticks can feed on mammals, birds, reptiles, and amphibians. Unlike most tick species,'' D. variabilis'' prefers the same host during all of its life stages. Life Cycle

Dermacentor variabilis-female.jpg, Female on human skin Dermacentor variabilis-male.jpg, Male on human skin

Distribution and seasonal activity

Within North America, the normal range is in the eastern part of the continent, with some reports in California. At the northernmost extent of its geographical range, in

Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...

and

Massachusetts Massachusetts ( ; ), officially the Commonwealth of Massachusetts, is a U.S. state, state in the New England region of the Northeastern United States. It borders the Atlantic Ocean and the Gulf of Maine to its east, Connecticut and Rhode ...

, ticks are active from April to August, with a peak in May to June. In coastal Virginia, the adults are active from April to September or October, with peaks in May and July. Seasonal activity in Ohio is from late April to September, with peaks in May to June and another smaller peak in August to September. In Georgia, adults are active from late March to August, with peaks in early May, late May, and late June. Florida adult activity is from April to July, with activity being restricted by high summer temperatures and low winter humidity.

Disease transmission

Feeding ticks transmit pathogens to the host. Depending on the tick species and its stage of life, preparing to feed can take from 10 minutes to 2 hours. When the tick finds a feeding spot, it grasps the skin and cuts into the surface, where it then inserts its feeding tube. Many species also secrete a cement-like substance that keeps them firmly attached during the meal. The feeding tube can have barbs to help keep the tick in place. Ticks also can secrete small amounts of saliva with anesthetic properties so that the animal or person cannot feel that the tick has attached itself. Therefore, unless one feels the tick crawling, noticing the tick is difficult. If the tick is in a sheltered spot, it can go unnoticed and can slowly suck the blood for several days. If the host animal has a blood-borne infection, the tick will ingest the pathogens with the blood. Small amounts of saliva from the tick may also enter the skin of the host animal during the feeding process. If the tick contains a pathogen, the organism may be transmitted to the host animal in this way. After feeding, most ticks drop off and prepare for the next life stage. At its next feeding, it can then transmit an acquired disease to the new host. Symptoms of Rocky Mountain spotted fever appear within 3-12 days, usually beginning with a sudden onset of fever and headache, and frequently followed 2-4 days later by a rash around the wrists and ankles that moves slowly up to the rest of the body. Other symptoms include nausea, loss of appetite, abdominal pain, or muscle aches. Rocky Mountain spotted fever can be fatal within ''days'' of symptoms beginning, if left untreated. A tick bite does not automatically transfer diseases to the host. Instead, the tick must be attached to the host for a period of time, generally 6–8 hours but sometimes as little as 3–6 hours, before it is capable of transferring disease. The earlier the tick is removed from a host, the less likely it is to contract the illness.

Treatments and prevention in dogs

The American dog tick is commonly found in highly wooded, shrubby, and long-grass areas. Tick numbers can be reduced by cutting the grass, which creates a low-humidity environment, which is undesirable to ticks. Pesticides can also be used and are most effective when applied to vegetation that has been cut to a short level.

Doxycycline Doxycycline is a Broad-spectrum antibiotic, broad-spectrum antibiotic of the Tetracycline antibiotics, tetracycline class used in the treatment of infections caused by bacteria and certain parasites. It is used to treat pneumonia, bacterial p ...

is the medication of choice to treat Rocky Mountain spotted fever in dogs. Doxycycline is given for 7–21 days dependent on the dosage.

Tetracycline Tetracycline, sold under various brand names, is an antibiotic in the tetracyclines family of medications, used to treat a number of infections, including acne, cholera, brucellosis, plague, malaria, and syphilis. It is available in oral an ...

is effective and administered more frequently, being given for 14–21 days. Other antibiotic choices include

enrofloxacin Enrofloxacin, sold under the brand name Baytril, among others, is a fluoroquinolone antibiotic used for the treatment of animals. It is a bactericidal agent. The bactericidal activity of enrofloxacin is concentration-dependent, with susceptibl ...

and

chloramphenicol Chloramphenicol is an antibiotic useful for the treatment of a number of bacterial infections. This includes use as an eye ointment to treat conjunctivitis. By mouth or by intravenous, injection into a vein, it is used to treat meningitis, pl ...

. Veterinary-approved flea and tick preparations are recommended, along with other topicals, collars, and shampoos. Regularly checking dogs and oneself for ticks after hiking or playing in grassy areas and removing ticks as soon as possible decrease the chances a dog will contract a secondary illness carried by the tick.

Tweezers Tweezers are small hand tools used for grasping objects too small to be easily handled with the human fingers. Tweezers are thumb-driven forceps most likely derived from tongs used to grab or hold hot objects since the dawn of recorded history. ...

are the most common removal method, but fine-point tweezers are best to avoid tearing the tick and spreading possible infectious agents in the bite area. Spread the dog’s fur, grasp the tick as close to the skin as possible, and very gently pull straight upward in a slow, steady motion. Another removal method is a tick removal hook: one places the prongs of the device on either side of the tick and twists upward. Tick removal hooks are recommended in areas where ticks are common. Removing the tick with fingers is never a good idea because squeezing to grasp the tick could potentially inject more infectious material. Apply rubbing alcohol to the bite area afterward to thoroughly clean the wound.

References

External links

Tick borne disease
from

CDC The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency under the Department of Health and Human Services (HHS), and is headquartered in Atlanta, ...

Ohio State University Extension Fact Sheet

photographs

on the

University of Florida The University of Florida (Florida or UF) is a public university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...

Institute of Food and Agricultural Sciences An institute is an organizational body created for a certain purpose. They are often research organisations (research institutes) created to do research on specific topics, or can also be a professional body. In some countries, institutes ca ...

''Featured Creatures'' website {{Taxonbar, from=Q4297977 Arachnids of North America Ticks Parasites of dogs Arachnids described in 1821 Ixodidae