noms dans le fil d’Ariane
American dog ticks are vectors for diseases such as Rocky Mountain spotted fever and tularemia. Dogs and humans may also be affected by tick paralysis if they become hosts. Rocky Mountain spotted fever is a disease that affects small blood vessels, causing an initial rash followed by other symptoms that include fever, vomiting, and diarrhea. There is an approximate 20% mortality rate if untreated, but ticks must remain attached for at least 6 hours in order to transmit the disease. Tularemia has a mortality rate of approximately 7% if untreated; symptoms include chills, fever, and swollen lymph nodes. Tick paralysis can occur in dogs and humans, and is caused by a neurotoxic protein produced in a tick's salivary glands that may enter the bloodstream during feeding. The mortality rate is about 10%, but individuals are likely to recover if the tick is removed.
Negative Impacts: injures humans (bites or stings, causes disease in humans ); causes or carries domestic animal disease
Although American dog ticks are very well protected by their exoskeletons, they do have some natural predators, including centipedes, newts, salamanders, skinks, spiders, toads and turkeys.
Known Predators:
American dog ticks are typically larger than other Ixodes species, and are characterized by ornate, light-colored dorsal patterns including various shapes such as diamonds and other geometric designs on an otherwise brown to reddish-brown body. These ticks have rounded or oval bodies. Their coxae (first leg segments) are split into two parts, which have characteristic spurs. Shortened mouthparts and palps, along with their ornate dorsal patterns, distinguish American dog ticks from similar tick species. Adults and nymphs of this species have eight legs, though larvae have only six. Nymphs also lack a genital pore, which is found on the underside of adults.
This species is sexually dimorphic. Females range in size from 4 mm before a meal to as high as 15 mm long and 10 mm wide following, and their dorsal patterning only covers the anterior portion of their scutum (dorsal shields). Males are smaller and their patterning extends over the entire scutum.
Range length: 3.6 to 15 mm.
Average length: 4 mm.
Other Physical Features: ectothermic ; bilateral symmetry
Sexual Dimorphism: female larger; sexes colored or patterned differently; male more colorful
Longevity of American dog ticks depends on whether hosts are found for feeding in a appropriate amount of time. Larvae can survive 11 months before their first feeding, nymphal stages can survive 6 months without feeding, and adults can survive 2 years without feeding. The life cycle of this species can be completed in as few as 54 days but may take up to two years. Adult females die soon after breeding, while males may live to breed over multiple seasons.
Range lifespan
Status: wild: 2 to 24 months.
Average lifespan
Status: wild: 11 months.
American dog ticks are generally found in forests, densely wooded areas, and grasslands, which support a large number possible hosts. They are also commonly found in areas regularly visited by potential mammalian hosts, such as vegetation on the sides of roads, near trails, and in grassy areas near highway rest stops.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: taiga ; savanna or grassland ; forest ; scrub forest ; mountains
Other Habitat Features: suburban ; agricultural ; riparian
American dog ticks are found in the United States, mainly east of the Rocky Mountains (from Montana to south Texas), with some reports of the species from California and the Pacific Northwest, west of the Cascade and Sierra Nevada Mountains. They are most commonly found in the United States along the east coast. This species is also found in parts of Canada, east of Saskatchewan, as well as in northern Mexico.
Biogeographic Regions: nearctic (Native )
This species parasitizes almost all mammals and feeds exclusively on blood, making it an obligate sanguivore. Feeding occurs periodically for 3-11 days at a time and these animals can live for long periods of time without feeding, at all stages of development. Adult ticks, which consume greater quantities of blood, prefer larger hosts. Though this list is not all-inclusive, some specific mammals known to be hosts of this tick include dogs, humans, rabbits, raccoons, rats, mice, porcupines squirrels, and voles.
Animal Foods: blood
Primary Diet: carnivore (Sanguivore )
American dog ticks are obligate ectoparasites in all stages of development. Larvae and nymphs target smaller mammals such as mice and other rodents, while adults target larger mammals such as dogs, raccoons, cattle, and humans. Different abundance patterns are observed for engorged and non-engorged ticks. For example, engorged tick abundance is primarily a function of host age, with younger hosts more easily supporting engorged ticks. Non-engorged tick abundance depends more on abiotic factors such as season or collection site. A wooded or grassy area in the spring will have a high abundance of non-engorged ticks.
American dog ticks are carriers of the pathogen which causes Rocky Mountain spotted fever (Rickettsia rickettsii, a type of coccobacillus), as well as Francisella tularensis (a bacteria), which causes tularemia, also known as "rabbit fever." They can also carry and transmit Cytauxzoon felis, a protozoan, from wild cats to domestic cats.
Ecosystem Impact: parasite
Species Used as Host:
Commensal/Parasitic Species:
This species provides no known economic benefits to humans.
American dog ticks hatch from eggs as 6-legged larvae and then become 8-legged nymphs, before finally reaching adulthood. A blood meal from a different host is required before each stage. This can make development a long process, as suitable hosts are not always readily available. After hatching, larvae wait on the ground for a small mammal host such as a mouse for their first blood meal. They then drop off this first host and wait for a second host, typically a larger mammal such as a raccoon. This process is repeated until adulthood is achieved, generally taking at least 54 days but possibly years, depending on host availability, as feeding takes several days at each stage and these animals may have to wait for several months to a year for subsequent hosts. After adult females find final hosts, they feed and engorge a last time before dropping off to mate, lay eggs, and die.
Development - Life Cycle: metamorphosis
This species has no special conservation status.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
These ticks locate hosts by climbing a blade of grass or small plant and extending their legs in anticipation of a mammal host. There is evidence suggesting that ticks "quest" on paths followed by mammals, led by their odors. Males are attracted to females by sensing pheromones. In addition, all ticks of the suborder Ixodida have a sense organ on their first legs termed Haller's Organ. This organ contains sensilla that are sensitive to carbon dioxide and infrared radiation, likely aiding them in locating hosts.
Communication Channels: tactile ; chemical
Other Communication Modes: pheromones ; scent marks ; vibrations
Perception Channels: infrared/heat ; tactile ; vibrations ; chemical
American dog ticks mate once yearly, typically in mid-April after emerging from over-wintering in soil. Adult females partially engorge while on their host and then release pheromones to incite males to drop off their hosts. Once males have been attracted and copulation is complete, females finish feeding before dropping off to lay eggs. While females die after laying eggs and so only mate with one male, a single male may mate with multiple females.
Mating System: polygynous
American dog ticks reproduce sexually with breeding occurring in the spring (most typically in mid-April). Once a male has dropped off his host, attracted by pheromones released by a female, he approaches her. After making contact, a male mounts a female, locates her genital opening, and inserts a spermatophore into her using his mouthparts. Mating takes place on the host. Within 5-14 days, females drop from their hosts, fully engorged. Four to ten days later, once egg development is complete, females will lay up to 6500 eggs before dying. The number of eggs laid is positively correlated with temperature and amount of blood taken during the final blood meal, up to temperatures exceeding 35°C or final blood meals exceeding 665 mg.
Breeding interval: American dog ticks breed once yearly.
Breeding season: Breeding season is in the spring, most often mid-April.
Range number of offspring: 4000 eggs to 6500 eggs.
Range gestation period: 4 to 10 days.
Range age at sexual or reproductive maturity (female): 1 to 17 months.
Average age at sexual or reproductive maturity (female): 3 months.
Range age at sexual or reproductive maturity (male): 1 to 17 months.
Average age at sexual or reproductive maturity (male): 3 months.
Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Males exhibit no parental investment following copulation. Females protect and nourish eggs in the body, before dying after egg laying is complete. Once eggs hatch, larvae search for their first small mammal host without any parental assistance.
Parental Investment: female parental care ; pre-fertilization (Provisioning, Protecting: Female)
Dermacentor variabilis, often known as the American Dog Tick, is a 3-host tick that occurs mainly in the eastern United States (although it occurs outside this region as well), where adults are commonly encountered on dogs. These ticks generally feed on smaller mammals as larvae and nymphs and on larger mammals as adults. Although often found on dogs, these ticks will also feed on larger animals, such as cattle, horses, and even humans. Adults are vectors for Rocky Mountain spotted fever, tularemia, and canine tick paralysis. (Chan and Kaufman 2008 and references therein)
The 8-legged adult male and female D. variabilis ticks are typically brown to reddish-brown in color with gray/silver markings on their scutum (dorsal shield). Females have a very short scutum, present just behind the mouthparts, while the male scutum covers the majority of its dorsal surface. Once engorged with blood, a typical 5 mm female can enlarge to 15 mm in length and 10 mm in width. Larvae are yellow before blood-feeding and gray to black when engorged. Nymphs are a pale, yellowish brown before feeding; they become slate gray when engorged. Both larvae and nymphs have red markings near their eyes and lack any white on the scutum. Dermacentor variabilis ticks require a blood meal before progression from 6-legged larva to 8-legged nymph, and from nymph to adult, and adult females require a blood meal for egg production (typically laying between 4,000 and 6,500 eggs on the ground). Between each of these stages, the developing tick drops off its host and must then locate a new host for its next meal. Because larval and nymphal D. variabilis rarely bite humans, the adult tick is the primary stage of concern for humans. (Chan and Kaufman 2008 and references therein)
After hatching, larvae remain on the ground or climb onto vegetation, where they wait for small mammals, such as mice, to serve as hosts for their first blood meal. This host location behavior is known as "questing". Under favorable conditions, larvae can survive up to 11 months without feeding. After contacting and attaching to a host, larvae require from two to 14 days to complete blood feeding. After feeding, larvae detach from their host and fall to the ground, where they digest their blood meal and molt into the nymphal stage. This process can take as little as a week, although it often takes longer. Nymphs can survive six months without a blood meal. After successfully questing for their second host, which is typically a slightly larger mammal (such as a raccoon or opossum), the nymphs feed for three to 10 days. After engorging, they fall off the host, digest their blood meal and molt into an adult. This process can take anywhere from three weeks to several months. Adults can survive two years without feeding. Questing adult ticks climb onto a grass blade or other low vegetation, cling to it with their third pair of legs, and wave their other legs as a potential host approaches. As the hosts brush the vegetation, the ticks grab onto the passing animal. The complete life cycle requires at least 54 days to complete, but can take up to two years depending on host availability, host location, and ambient temperature. Mating occurs on the host and the female engorges within six to 13 days, after which she drops from the host to lay her eggs and then dies, thus completing the cycle. (Chan and Kaufman 2008 and references therein)
Dermacentor variabilis, often known as the American Dog Tick, is a 3-host tick that occurs mainly in the eastern United States (although it occurs outside this region as well), where adults are commonly encountered on dogs. These ticks generally feed on smaller mammals as larvae and nymphs and on larger mammals as adults. Although often found on dogs, these ticks will also feed on larger animals, such as cattle, horses, and even humans. Adults are vectors for Rocky Mountain spotted fever, tularemia, and canine tick paralysis. (Chan and Kaufman 2008 and references therein)
The 8-legged adult male and female D. variabilis ticks are typically brown to reddish-brown in color with gray/silver markings on their scutum (dorsal shield). Females have a very short scutum, present just behind the mouthparts, while the male scutum covers the majority of its dorsal surface. Once engorged with blood, a typical 5 mm female can enlarge to 15 mm in length and 10 mm in width. Larvae are ~0.62 mm long and are yellow before blood-feeding and gray to black when engorged. Nymphs are about 0.9 mm long and a pale, yellowish brown before feeding; they become slate gray when engorged. Both larvae and nymphs have red markings near their eyes and lack any white on the scutum. Dermacentor variabilis ticks require a blood meal before progression from 6-legged larva to 8-legged nymph, and from nymph to adult ,and adult females require a blood meal for egg production. Between each of these stages, the developing tick drops off its host and must then locate a new host for its next meal. (Chan and Kaufman 2008 and references therein)
After five to 14 days of blood feeding, a fully engorged female D. variabilis drops from the host. She digests the blood meal and develops her egg clutch over the next four to 10 days. She then lays anywhere from 4,000 to 6,500 eggs on the ground. About 26 to 40 days later, depending on the temperature, the eggs hatch into larvae. After hatching, larvae remain on the ground or climb vegetation, where they wait for small mammals, such as mice, to serve as hosts for their first blood meal. This host location behavior is known as "questing". Under favorable conditions, larvae can survive up to 11 months without feeding. After contacting and attaching to a host, larvae require from two to 14 days to complete blood feeding. After feeding, larvae detach from their host and fall to the ground where they digest their blood meal and molt into the nymphal stage. This process can take as little as a week, although it often takes longer. Nymphs can survive six months without a blood meal. After successfully questing for their second host, which is typically a slightly larger mammal (such as a raccoon or opossum), the nymphs feed for three to 10 days. After engorging, they fall off the host, digest their blood meal and molt into an adult. This process can take anywhere from three weeks to several months. Adults can survive two years without feeding, but readily feed on dogs or other larger animals when available. Questing adult ticks climb onto a grass blade or other low vegetation, cling to it with their third pair of legs, and wave their other legs as a potential host approaches. As the hosts brush the vegetation, the ticks grab onto the passing animal. The complete life cycle requires at least 54 days to complete, but can take up to two years depending on host availability, host location, and ambient temperature. Mating occurs on the host and the female engorges within six to 13 days after which she drops from the host to lay her eggs and then dies, thus completing the cycle. (Chan and Kaufman 2008 and references therein)
Adult D. variabilis overwinter in the soil and are most active from around mid-April to early September. Larvae are active from about March through July and nymphs are usually found from June to early September. Dermacentor variabilis is the primary vector for the pathogen causing Rocky Mountain spotted fever (RMSF) and is also known to transmit the bacteria that cause tularemia. The ticks themselves can cause canine tick paralysis. Overwintering larvae can also acquire RMSF transovarially (mother to egg) yielding RMSF-infected larvae. Because larval and nymphal D. variabilis rarely bite humans, the adult tick is the primary stage of concern for humans. (Chan and Kaufman 2008 and references therein)
Dermacentor variabilis ist ein Vertreter der Gattung der Buntzecken. Die Zeckenart ist in den Vereinigten Staaten von Amerika beheimatet und tritt vor allem in den östlichen zwei Dritteln des Landes auf. Hauptwirt der Adulten sind Hunde, gelegentlich werden auch Katzen oder der Mensch befallen. Larven und Nymphen befallen kleine Nagetiere. Der Parasit kann eine Zeckenparalyse verursachen und spielt als Vektor für das Rocky-Mountain-Fleckfieber und das Colorado-Zeckenfieber des Menschen eine Rolle. Außerdem kann er die Tularämie, bei Hunden die Ehrlichiose und die Borreliose sowie bei Rindern die Bovine Anaplasmose übertragen.[1]
Männchen sind 3 bis 4 mm lang, Weibchen 4 mm, in vollgesogenem Zustand bis zu 15 mm. D. variabilis ist blassbraun und der Rückenschild zeigt graue Ornamente. Die Mundwerkzeuge sind kurz. Die Basis des Capitulums ist breit und kurz. Das erste Beinpaar trägt einen deutlichen Dorn.[1]
D. variabilis ist dreiwirtig. Weibchen saugen bis zu zwei Wochen an ihrem Wirt, lassen sich dann abfallen und legen 4000 bis 6500 Eier. Aus diesen schlüpfen nach vier Wochen die Larven und suchen sich einen Wirt. Nach vier bis fünf Tagen lassen sie sich abfallen und häuten sich zur Nymphe. Diese saugt fünf bis sechs Tage an einem Nagetier und lässt sich wiederum abfallen, um sich zum Adulten zu häuten. Unter günstigen Bedingungen dauert die Entwicklung drei Monate.[1]
Dermacentor variabilis ist ein Vertreter der Gattung der Buntzecken. Die Zeckenart ist in den Vereinigten Staaten von Amerika beheimatet und tritt vor allem in den östlichen zwei Dritteln des Landes auf. Hauptwirt der Adulten sind Hunde, gelegentlich werden auch Katzen oder der Mensch befallen. Larven und Nymphen befallen kleine Nagetiere. Der Parasit kann eine Zeckenparalyse verursachen und spielt als Vektor für das Rocky-Mountain-Fleckfieber und das Colorado-Zeckenfieber des Menschen eine Rolle. Außerdem kann er die Tularämie, bei Hunden die Ehrlichiose und die Borreliose sowie bei Rindern die Bovine Anaplasmose übertragen.
Dermacentor variabilis, also known as the American dog tick or wood 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 best-known hard ticks. 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, the causative agent of Lyme disease,[1] these ticks are not competent vectors for the transmission of this disease.[2][3][4] The primary vectors for B. burgdorferi are the deer ticks Ixodes scapularis in eastern parts of the United States, Ixodes pacificus in California and Oregon, and Ixodes ricinus in Europe. D. variabilis may also carry Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis, and Ehrlichia chaffeensis, the causative agent of human monocytic ehrlichiosis.[1][5]
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.
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.[6]
Female on human skin
Male on human skin
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 and Massachusetts, ticks are active from April to August, with a peak in May to June.[7] In coastal Virginia, the adults are active from April to September or October, with peaks in May and July.[7] Seasonal activity in Ohio is from late April to September, with peaks in May to June and another smaller peak in August to September.[7] In Georgia, adults are active from late March to August, with peaks in early May, late May, and late June.[7] Florida adult activity is from April to July, with activity being restricted by high summer temperatures and low winter humidity.[7]
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.[6] When the tick finds a feeding spot, it grasps the skin and cuts into the surface, where it then inserts its feeding tube.[6] Many species also secrete a cement-like substance that keeps them firmly attached during the meal.[6] The feeding tube can have barbs to help keep the tick in place.[6] 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.[6] 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.[6] Small amounts of saliva from the tick may also enter the skin of the host animal during the feeding process.[6] If the tick contains a pathogen, the organism may be transmitted to the host animal in this way.[6] After feeding, most ticks drop off and prepare for the next life stage.[6] At its next feeding, it can then transmit an acquired disease to the new host.[6]
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.[8] In dogs additional symptoms may include lethargy, blood in the urine, irregular heartbeat, discolored spots on the skin (often bruised or purplish in color), inability to walk normally, loss of coordination, swelling or edema in the limbs, sudden bleeding from the nose or in the stools, difficulty with blood clotting, swollen lymph nodes, pain in the eyes, inflammation, hemorrhage, or conjunctivitis in the mucosal membranes.[9]
Symptoms of tularemia usually appear within 3–5 days, but can appear as late as 21 days after transmission. Oftentimes, patients experience chills, swollen lymph nodes, and an ulceration at the site of the bite.[10]
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[10] but sometimes as little as 3–6 hours,[11] 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.
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.[10] Doxycycline is the medication of choice to treat Rocky Mountain spotted fever in dogs.[12] Doxycycline is given for 7–21 days dependent on the dosage.[12] Tetracycline is effective and administered more frequently, being given for 14–21 days.[12] Other antibiotic choices include enrofloxacin and chloramphenicol.[12] Veterinary-approved flea and tick preparations[13] are recommended, along with other topicals, collars,[14] and shampoos.[15] 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.[15] Tweezers 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.[11] 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.[11] Another removal method is a tick removal hook: one places the prongs of the device on either side of the tick and twists upward.[11] Tick removal hooks are recommended in areas where ticks are common.[11] Removing the tick with fingers is never a good idea because squeezing to grasp the tick could potentially inject more infectious material.[11] Apply rubbing alcohol to the bite area afterward to thoroughly clean the wound.[11]
Dermacentor variabilis, also known as the American dog tick or wood 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 best-known hard ticks. 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, the causative agent of Lyme disease, these ticks are not competent vectors for the transmission of this disease. The primary vectors for B. burgdorferi are the deer ticks Ixodes scapularis in eastern parts of the United States, Ixodes pacificus in California and Oregon, and Ixodes ricinus in Europe. D. variabilis may also carry Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis, and Ehrlichia chaffeensis, the causative agent of 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.
Dermacentor variabilis, también conocida la garrapata americana del perro o la garrapata de madera, es una especie de garrapata que se conoce ser portadora (vector) de bacterias responsables de varias enfermedades en los seres humanos , incluyendo la fiebre de las Montañas Rocosas y tularemia (Francisella tularensis). Las enfermedades se propagan cuando chupa la sangre de sus huéspedes (generalmente mamíferos, como venados, gatos y perros], entre varias especies, pudiendo también alimentarse de seres humanos), los síntomas aparecen varios días después de la picadura. Aunque D. variabilis pueden estar expuesta a la Borrelia burgdorferi , el agente causal de la enfermedad de Lyme,[1] estas garrapatas no son vectores competentes para la transmisión de esta enfermedad.[2][3][4] El vector principal de Borrelia burgdorferi es la garrapata del venado Ixodes scapularis en partes del este de los Estados Unidos, y Ixodes pacificus en California y Oregón . Dermacentor variabilis también puede ser portadora del Anaplasma phagocytophilum y de Anaplasma chaffeensis, el agente causal de la HGA (Anaplasmosis granulocítica humana).[1] Las garrapatas del género Dermacentor, también pueden inducir un cuadro de parálisis por picadura de garrapata por la elaboración de una neurotoxina que induce rápidamente una progresiva parálisis flácida similar al Síndrome de Guillain-Barré. La neurotoxina impide la liberación presináptica de acetilcolina desde las uniones neuromusculares.
Dermacentor variabilis, juga dikenali sebagai sengkenit anjing Amerika atau sengkenit hutan, ialah satu spesies sengkenit yang diketahui membawa bakterium yang bertanggungjawab untuk beberapa penyakit pada manusia, termasuk demam bintik Pergunungan Rocky dan tularemia (Francisella tularensis). Ia merupakan salah satu daripada sengkenit keras yang paling diketahui. Penyakit tersebar apabila ia menyedut darah daripada perumah, yang boleh memakan masa beberapa hari untuk perumah mengalami sesetengah gejala.
Dermacentor variabilis, juga dikenali sebagai sengkenit anjing Amerika atau sengkenit hutan, ialah satu spesies sengkenit yang diketahui membawa bakterium yang bertanggungjawab untuk beberapa penyakit pada manusia, termasuk demam bintik Pergunungan Rocky dan tularemia (Francisella tularensis). Ia merupakan salah satu daripada sengkenit keras yang paling diketahui. Penyakit tersebar apabila ia menyedut darah daripada perumah, yang boleh memakan masa beberapa hari untuk perumah mengalami sesetengah gejala.
Dermacentor variabilis Say, 1908
Ареал
Dermacentor variabilis (лат.) — вид клещей из рода Dermacentor. Распространён в США, встречаясь преимущественно в восточной части страны. Основным хозяином являются собаки, иногда кошки или человек. Личинки и нимфы нападают на мелких грызунов. Может вызвать клещевой паралич, является переносчиком пятнистой лихорадки Скалистых гор и лихорадки Колорадо. Кроме того, может вызвать туляремию, у собак — эрлихиоз и боррелиоз, у крупного рогатого скота — анаплазмоз жвачных животных[1].
Самцы длиной от 3 до 4 мм, самки — 4 мм, в напившемся состоянии до 15 мм. Окраска тела бледно-коричневого цвета, спинной щиток имеет серый рисунок. Ротовые челюсти короткие. Основание гнатосомы широкое и короткое. Первая пара ног имеет острый шип[1].
D. variabilis имеет трёх хозяев. Самки сосут до двух недель на своём хозяине, затем отпадают и откладывают 4000—6500 яиц. Из них через четыре недели вылупляются личинки и начинают искать хозяина. После четырех или пяти дней они падают на землю и линяют, превращаясь в нимф. Затем нимфа присасывается на пять или шесть дней к грызунам и снова отпадает, линяя до взрослой стадии - имаго. При благоприятных условиях развитие длится три месяца[1].
Dermacentor variabilis (лат.) — вид клещей из рода Dermacentor. Распространён в США, встречаясь преимущественно в восточной части страны. Основным хозяином являются собаки, иногда кошки или человек. Личинки и нимфы нападают на мелких грызунов. Может вызвать клещевой паралич, является переносчиком пятнистой лихорадки Скалистых гор и лихорадки Колорадо. Кроме того, может вызвать туляремию, у собак — эрлихиоз и боррелиоз, у крупного рогатого скота — анаплазмоз жвачных животных.
Самцы длиной от 3 до 4 мм, самки — 4 мм, в напившемся состоянии до 15 мм. Окраска тела бледно-коричневого цвета, спинной щиток имеет серый рисунок. Ротовые челюсти короткие. Основание гнатосомы широкое и короткое. Первая пара ног имеет острый шип.
D. variabilis имеет трёх хозяев. Самки сосут до двух недель на своём хозяине, затем отпадают и откладывают 4000—6500 яиц. Из них через четыре недели вылупляются личинки и начинают искать хозяина. После четырех или пяти дней они падают на землю и линяют, превращаясь в нимф. Затем нимфа присасывается на пять или шесть дней к грызунам и снова отпадает, линяя до взрослой стадии - имаго. При благоприятных условиях развитие длится три месяца.
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