Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by feeding on the blood of mammals, birds, and sometimes reptiles and amphibians. The timing of the origin of ticks is uncertain, though the oldest known tick fossils are from the Cretaceous period, around 100 million years old. Ticks are widely distributed around the world, especially in warm, humid climates.
|Ixodes ricinus, a hard tick|
|18 genera, about 900 species|
Ticks belong to two major families, the Ixodidae or hard ticks, and the Argasidae, or soft ticks. Nuttalliella, a genus of tick from southern Africa is the only member of the family Nuttalliellidae, and represents the most primitive living lineage of ticks. Adults have ovoid/pear-shaped bodies (idiosomas) which become engorged with blood when they feed, and eight legs. Their cephalothorax and abdomen are completely fused. In addition to having a hard shield on their dorsal surfaces, known as the scutum, hard ticks have a beak-like structure at the front containing the mouthparts, whereas soft ticks have their mouthparts on the underside of their bodies. Ticks locate potential hosts by sensing odor, body heat, moisture, and/or vibrations in the environment.
Ticks have four stages to their lifecycle, namely egg, larva, nymph, and adult. Ticks belonging to the Ixodidae family undergo either a one-host, two-host, or three-host lifestyle. Argasid ticks have up to seven nymphal stages (instars), each one requiring blood ingestion, Argasid ticks undergo a multihost lifestyle. Because of their hematophagous (blood-ingesting) diets, ticks act as vectors of many serious diseases that affect humans and other animals.
Taxonomy and phylogenyEdit
Ticks belong to the Parasitiformes, a distinctive group of mites that are separate from the main group of mites, the Acariformes. Whether the two groups are more closely related to each other than to other arachnids is uncertain, and studies often recover them as not closely related. Within the Parasitiformes, ticks are most closely related to the Holothyrida, a small group of free living scavengers with 32 described species confined to the landmasses that formed the supercontinent Gondwana.
Fossilized ticks have been discovered from the end of the Early Cretaceous onwards, most commonly in amber. The oldest discovered tick fossils are an argasid bird tick from Late Cretaceous (Turonian ~94-90 million years ago) aged New Jersey amber, and various ticks found in Burmese amber, including Khimaira and Deinocroton, which do not belong to any living family of tick, and members of the living ixodid genera Amblyomma and Ixodes dating the earliest Cenomanian stage of the Late Cretaceous, around . An undescribed juvenile tick is known from late Albian Spanish amber, dating to 105 million years ago. The younger Baltic and Dominican ambers have also yielded examples that can be placed in living genera. A phylogenetic analysis suggests that the last common ancestor of all living ticks likely lived around 195 million years ago in the Southern Hemisphere, in what was then Gondwana.
Ticks belong to three different families. The majority of tick species belong to the two families: Ixodidae (hard ticks) and Argasidae (soft ticks). The third living family is Nuttalliellidae, named for the bacteriologist George Nuttall. It comprises a single species, Nuttalliella namaqua, and as such is a monotypic taxon. Nuttalliella namaqua is found in southern Africa ranging from Tanzania to Namibia and South Africa.
The Ixodidae contain over 700 species of hard ticks with a scutum or hard shield, which the Argasidae lack. The Argasidae contain about 200 species; the genera accepted as of 2010[update] are Antricola, Argas, Nothoaspis, Ornithodoros, and Otobius. They have no scutum, and the capitulum (mouth and feeding parts) is concealed beneath the body. The phylogeny of the Ixodida within the Acari is shown in the cladogram, based on a 2014 maximum parsimony study of amino acid sequences of 12 mitochondrial proteins. The Argasidae appear monophyletic in this study.
Anatomy and physiologyEdit
Ticks, like mites, belong to the subclass Acari that lack their primary somatic segmentation of the abdomen (or opisthosoma), rather these parasitic arachnids present a subsequent fusion of the abdomen with the cephalothorax (or prosoma). The tagmata typical of other Chelicerata have developed into the gnathosoma (head), which is retractable and contains the mouthparts, and idiosoma (body), which contains the legs, digestive tract, and reproductive organs. The gnathosoma is a feeding structure with mouthparts adapted for piercing skin and sucking blood; it is the front of the head and contains neither the brain nor the eyes. Features of the gnathosoma include two palps, two chelicerae, and hypostome. The hypostome acts as stabilizer and helps to anchor the tick's mouthparts to the host. The chelicerae are specialized appendages used for cutting and piercing into the host's skin while palps are leglike appendages that are sensory in function.
The ventral side of the idiosoma bears sclerites, and the gonopore is located between the fourth pair of legs. In the absence of segmentation, the positioning of the eyes, limbs, and gonopore on the idiosoma provide the only locational guidance.
Most ticks are inornate and appear to be brown or reddish brown in color. However, some species are ornate and have distinctive white patterns on the scutum.
Larval ticks hatch with six legs, acquiring the other two after a blood meal and molting into the nymph stage. In the nymphal and adult stages, ticks have eight legs, each of which has seven segments and is tipped with a pair of claws. The legs are sometimes ornamented and usually bear sensory or tactile hairs. In addition to being used for locomotion, the tarsus of leg I contains a unique sensory structure, Haller's organ, which can detect odors and chemicals emanating from the host, as well as sensing changes in temperature and air currents. Ticks can also use Haller's organs to perceive infrared light emanating from a host. When stationary, their legs remain tightly folded against the body.
Ticks are extremely tough, hardy, and resilient animals. They can survive in a near vacuum for as long as half an hour. Their slow metabolism during their dormant periods enables them to go prolonged durations between meals. During droughts, they can endure dehydration without feeding for as long as eighteen weeks, however, ticks with limited energy reserves may succumb to desiccation after thirty-six weeks. To keep from dehydrating, ticks hide in humid spots on the forest floor or absorb water from subsaturated air by secreting hygroscopic fluid produced by the salivary glands onto the external mouthparts and then reingesting the water-enriched fluid.
Ticks can withstand temperatures just above −18 °C (0 °F) for more than two hours and can survive temperatures between −7 and −2 °C (20 and 29 °F) for at least two weeks. Ticks have even been found in Antarctica, where they feed on penguins.
In nymphs and adults, the capitulum is prominent and projects forwards from the body. The eyes are close to the sides of the scutum and the large spiracles are located just behind the coxae of the fourth pair of legs. The hard protective scutellum, a characteristic of this family, covers nearly the whole dorsal surface in males, but is restricted to a small, shield-like structure behind the capitulum in females and nymphs. When an ixodid attaches to a host the bite is typically painless and generally goes unnoticed. They remain in place until they engorge and are ready to molt; this process may take days or weeks. Some species drop off the host to molt in a safe place, whereas others remain on the same host and only drop off once they are ready to lay their eggs.
The body of a soft tick is pear-shaped or oval with a rounded anterior portion. The mouthparts cannot be seen from above, as they are on the ventral surface. A centrally positioned dorsal plate with ridges projecting slightly above the surrounding surface, but with no decoration are often present. Soft ticks possess a leathery cuticle as well. A pattern of small, circular depressions expose where muscles are attached to the interior of the integument. The eyes are on the sides of the body, the spiracles open between legs 3 and 4, and males and females only differ in the structure of the genital pore.
Nuttalliellidae can be distinguished from both ixodid and argasid ticks by a combination of a projecting gnathosoma and a soft leathery skin. Other distinguishing characteristics include the position of the stigmata, the lack of setae, the strongly corrugated integument, and the form of the fenestrated plates.
Diet and feedingEdit
Ticks are ectoparasites and consume blood to satisfy all of their nutritional requirements. They are obligate hematophages, and require blood to survive and move from one stage of life to another. Ticks can fast for long periods of time, but eventually die if unable to find a host. Hematophagy evolved independently at least six times in arthropods living during the late Cretaceous; in ticks it is thought to have evolved 120 million years ago through adaptation to blood-feeding. This behavior evolved independently within the separate tick families as well, with differing host-tick interactions driving the evolutionary change.
Some ticks attach to their host rapidly, while others wander around searching for thinner skin, such as that in the ears of mammals. Depending on the species and life stage, preparing to feed can take from ten minutes to two hours. On locating a suitable feeding spot, the tick grasps the host's skin and cuts into the surface. It extracts blood by cutting a hole in the host's epidermis, into which it inserts its hypostome and prevents the blood from clotting by excreting an anticoagulant or platelet aggregation inhibitor.
Ticks find their hosts by detecting an animals' breath and body odors, sensing body heat, moisture, or vibrations. A common misconception about ticks is they jump onto their host or they fall from trees, however, they are incapable of flying or jumping. Many tick species, particularly Ixodidae, lie in wait in a position known as "questing". While questing, ticks cling to leaves and grasses by their third and fourth pairs of legs. They hold the first pair of legs outstretched, waiting to grasp and climb on to any passing host. Tick questing heights tend to be correlated with the size of the desired host; nymphs and small species tend to quest close to the ground, where they may encounter small mammalian or bird hosts; adults climb higher into the vegetation, where larger hosts may be encountered. Some species are hunters and lurk near places where hosts may rest. Upon receiving an olfactory stimulus or other environmental indication, they crawl or run across the intervening surface.
Other ticks, mainly the Argasidae, are nidicolous, finding hosts in their nests, burrows, or caves. They use the same stimuli as non-nidicolous species to identify hosts, with body heat and odors often being the main factors. Many of them feed primarily on birds, though some Ornithodoros species, for example, feed on small mammals. Both groups of soft tick feed rapidly, typically biting painfully and drinking their fill within minutes. Unlike the Ixodidae that have no fixed dwelling place except on the host, they live in sand, in crevices near animal dens or nests, or in human dwellings, where they come out nightly to attack roosting birds or emerge when they detect carbon dioxide in the breath of their hosts.
Ixodidae remain in place until they are completely engorged. Their weight may increase by 200 to 600 times compared to their prefeeding weight. To accommodate this expansion, cell division takes place to facilitate enlargement of the cuticle. In the Argasidae, the tick's cuticle stretches to accommodate the fluid ingested, but does not grow new cells, with the weight of the tick increasing five- to tenfold over the unfed state. The tick then drops off the host and typically remains in the nest or burrow until its host returns to provide its next meal.
Tick saliva contains about 1,500 to 3,000 proteins, depending on the tick species. The proteins with anti-inflammatory properties, called evasins, allow ticks to feed for eight to ten days without being perceived by the host animal. Researchers are studying these evasins with the goal of developing drugs to neutralise the chemokines that cause myocarditis, heart attack, and stroke.
Ticks do not use any other food source than vertebrate blood and therefore ingest high levels of protein, iron and salt, but few carbohydrates, lipids or vitamins. Ticks’ genomes have evolved large repertoires of genes related to this nutritional challenge, but they themselves cannot synthesize the essential vitamins that are lacking in blood meal. To overcome these nutritional deficiencies, ticks have evolved obligate interactions with nutritional endosymbionts. The first appearance of ticks and their later diversification were largely conditioned by this nutritional endosymbiosis lasting for millions of years. The most common of these nutritional endosymbionts belong to the Coxiella and Francisella bacterial genera. These intracellular symbiotic microorganisms are specifically associated with ticks and use transovarial transmission to ensure their persistence. Although Coxiella and Francisella endosymbionts are distantly related bacteria, they have converged towards an analogous B vitamin-based nutritional mutualism with ticks. Their experimental elimination typically results in decreased tick survival, molting, fecundity and egg viability, as well as in physical abnormalities, which all are fully restored with an oral supplement of B vitamins. The genome sequencing of Coxiella and Francisella endosymbionts confirmed that they consistently produce three B vitamin types, biotin (vitamin B7), riboflavin (B2) and folate (B9). As they are required for tick life cycle, these obligate endosymbionts are present in all individuals of the tick species they infect, at least at early stages of development since they may be secondarily lost in males during nymphal development. Since Coxiella and Francisella endosymbionts are closely related to pathogens, there is a substantial risk of misidentification between endosymbionts and pathogens, leading to an overestimation of infection risks associated with ticks.
Range and habitatEdit
Tick species are widely distributed around the world. They tend to flourish more in warm, humid climates, because they require a certain amount of moisture in the air to undergo metamorphosis, and low temperatures inhibit their development of eggs to larvae. The occurrence of ticks and tick-borne illnesses in humans is increasing. Tick populations are spreading into new areas, due in part to the warming temperatures of climate change.
Tick parasitism is widely distributed among host taxa, including marsupial and placental mammals, birds, reptiles (snakes, iguanas, and lizards), and amphibians. Ticks of domestic animals cause considerable harm to livestock through pathogenic transmission, causing anemia through blood loss, and damaging wool and hides. The Tropical Bont tick wreaks havoc on livestock and wildlife in Africa, the Caribbean, and several other countries through the spread of disease, specifically heartwater disease. The spinose ear tick has a worldwide distribution, the young feed inside the ears of cattle and various wildlife.
A habitat preferred by ticks is the interface where a lawn meets the forest, or more generally, the ecotone, which is unmaintained transitional edge habitat between woodlands and open areas. Therefore, one tick management strategy is to remove leaf litter, brush, and weeds at the edge of the woods. Ticks like shady, moist leaf litter with an overstory of trees or shrubs and, in the spring, they deposit their eggs into such places allowing larvae to emerge in the fall and crawl into low-lying vegetation. The 3 meter boundary closest to the lawn's edge are a tick migration zone, where 82% of tick nymphs in lawns are found.
In general, ticks are found wherever their host species occur. Migrating birds carry ticks with them on through their migrations; a study of migratory birds passing through Egypt discovered more than half the bird species examined were carrying ticks. It was also observed the tick species varied depending on the season of migration, in this study it is spring and autumn migrations, this is thought to occur due to the seasonal periodicities of the different species.
For an ecosystem to support ticks, it must satisfy two requirements; the population density of host species in the area must be great enough and it must be humid enough for ticks to remain hydrated. Due to their role in transmitting Lyme disease, Ixodid ticks, particularly the North American I. scapularis, have been studied using geographic information systems to develop predictive models for ideal tick habitats. According to these studies, certain features of a given microclimate – such as sandy soil, hardwood trees, rivers, and the presence of deer – were determined to be good predictors of dense tick populations.
Mites and nematodes feed on ticks, which are also a minor nutritional resource for birds. More importantly, ticks act as a disease vector and behave as the primary hosts of many different pathogens such as spirochaetes. Ticks carry various debilitating diseases therefore, ticks may assist in controlling animal populations and preventing overgrazing.
Ticks can transmit an array of infectious diseases that affect humans and other animals. Ticks that carry zoonotic pathogens often tend to have a wide host range. The infective agents can be present not only in the adult tick, but also in the eggs produced plentifully by the females. Many tick species have extended their ranges as a result of the movements of people, domesticated pets, and livestock. With increasing participation in outdoor activities such as wilderness hikes, more people and their dogs may find themselves exposed to ticks.
Ixodidae ticks have three different life cycles. Depending on the species, Ixodids can either possess a one-host lifecycle, two-host lifecycle, or three-host lifecycle.
In one-host ticks the tick remains on the host through the larval, nymphal, and adult stages, only to leave the host to lay eggs. Eggs laid in the environment hatch into larvae, which immediately seek out a host in which to attach and feed. Fed larvae molt into unfed nymphs that remain on the host. After engorging on the host's blood, the nymphs molt into sexually mature adults that remain on the host in order to feed and mate. Once a female is both fed and ready to lay eggs, only then does she leave the host in search of a suitable area to deposit her eggs. Ticks that follow this life cycle are called one-host ticks. The winter tick Dermacentor albipictus and the cattle tick Boophilus microplus are examples of one-host ticks.
The lifecycle of a two-host tick often spans two years. During fall the pregnant female tick will drop off her second host and lay her eggs. The eggs hatch during winter, the following spring the larvae emerge and attach to their first host. Newly hatched larvae attach to a host in order to obtain a blood meal. They remain on the host then develop into nymphs. Once engorged, they drop off the host and find a safe area in the natural environment in which to molt into adults, this typically occurs during the winter. Both male and female adults seek out a host on which to attach, which may be the same body that served as host during their early development but is often a larger mammal. Once attached, they feed and mate. Gravid females drop from the host to oviposit in the environment. Ticks that complete their life cycle in this manner are called two-host ticks, like Hyalomma anatolicum excavatum.
Most ixodid ticks require three hosts, and their lifecycles typically span three years. The female tick drops off its host, often in the fall, and lays thousands of eggs. The larvae hatch in the winter and emerge in the spring. When the larvae emerge, they attach and feed primarily on small mammals and birds. During the summer the larvae become engorged and drop off the first host to molt and become nymphs, this often occurs during the fall. The following spring the nymphs emerge and seek out another host, often a small rodent. The nymphs become engorged and drop off the host in the fall to molt and become adults. The following spring the adult ticks emerge and seek out a larger host, often a large mammal such as cattle or even humans. Females will mate on their third host. Female adults then engorge on blood and prepare to drop off to lay her eggs on the ground, while males feed very little and remain on the host in order to continue mating with other females.
Argasid ticks, unlike ixodid ticks, may go through up to seven nymphal stages (instars), requiring a meal of blood each time. Often, egg laying and mating occurs detached from the host in a safe environment. The eggs hatch and the larvae feed on a nearby host for anywhere from a few hours to several days, this depends on the species of tick. After they feed the larvae drop and molt into their first nymphal instars, then the nymph seeks out and feeds on its second host, often this is the same as the first host, within an hour. This process occurs repeatedly and until the last nymphal instar occurs, thus allowing the tick to molt into an adult. Once an adult these ticks feed rapidly and periodically their entire lifecycle. In some species an adult female may lay eggs after each feeding. Their lifecycles range from months to years. The adult female argasid tick can lay a few hundred to over a thousand eggs over the course of her lifetime. Both male and female adults feed on blood, and they mate off the host. During feeding, any excess fluid is excreted by the coxal glands, a process that is unique to argasid ticks.
Nuttalliellidae is an elusive monotypic family of tick, that is, possesses a single species, Nuttalliella namaqua. There is little to nothing known about the lifecycle and feeding habits of N. namaqua but it is speculated this species of tick has multiple different hosts.
Relationship with humansEdit
Ticks are implicated in the transmission of a number of infections caused by pathogens such as bacteria, viruses, and protozoa. A tick can harbor more than one type of pathogen, making diagnosis more difficult. Species of the bacterial genus Rickettsia are responsible for typhus, rickettsialpox, boutonneuse fever, African tick bite fever, Rocky Mountain spotted fever, Flinders Island spotted fever, and Queensland tick typhus (Australian tick typhus). Other tick-borne diseases include Lyme disease and Q fever, Colorado tick fever, Crimean–Congo hemorrhagic fever, tularemia, tick-borne relapsing fever, babesiosis, ehrlichiosis, Bourbon virus, and tick-borne meningoencephalitis, as well as bovine anaplasmosis and the Heartland virus. In the United States, Lyme disease is the most commonly reported vector-borne disease in the country.
Some species, notably the Australian paralysis tick, are also intrinsically venomous and can cause tick paralysis. Eggs can become infected with pathogens inside a female tick's ovaries, in which case the larval ticks are infectious immediately at hatching, before feeding on their first host. Tropical bont ticks transmit the heartwater, which can be particularly devastating in cattle. The ticks carried by migratory birds act as reservoirs and vectors of foreign infectious diseases. In the Egyptian migratory bird study, over 20 strains of pathogenic viruses were detected within the tick sample from autumn.
Not all ticks in an infective area are infected with transmittable pathogens, and both attachment of the tick and a long feeding session are necessary for diseases to be transmitted. Consequently tick bites often do not lead to infection, especially if the ticks are removed within 36 hours. While adult ticks can be removed with fine-tipped tweezers or proprietary tick removal tools then disinfecting the wound, there is growing consensus that ticks should be killed in-situ and frozen with either a custom spray or medical wart remover and left to fall out to avoid anaphylactic/allergic reactions. Professor Sheryl van Nunen, whose research in 2007 identified tick-induced mammalian meat allergy, famously said "tweezers are tick squeezers", referring to the tick toxins squeezed into people attempting to remove ticks with tweezers. Ticks can be disposed of by flushing them down the toilet, placing them in a container of soapy water or alcohol, or sticking them to tape that can then be folded over and thrown away.
Bifenthrin and permethrin, both pyrethroids, are sometimes used as tick-control measures, although they have the disadvantage of being carcinogenic and able to attack the nervous systems of other species besides ticks. Those who walk through tick-infested areas can make it harder for ticks to latch onto them by tucking their trousers into boots made of smooth rubber, which ticks have trouble climbing.
Research since 2008 has documented red-meat allergies (mammalian meat allergy and Alpha-gal allergy) in the U.S. due to lone star tick bites. The range of the problem has been expanding with the range of the tick. Other species of ticks are known for being responsible for meat allergies in other countries, including Sweden, Germany, and Australia.
Many tick-transmitted viruses, such as Crimean–Congo hemorrhagic fever virus, Kyasanur Forest disease virus, Alkhumra hemorrhagic fever virus, and Omsk hemorrhagic fever virus, are classified as dangerous enough to require biosafety level 4 precautions in laboratory environments. This includes five levels of containment, viz., storage vials within humidified desiccators, within environmental chambers, within a tick suite, within a BSL4 laboratory. Precautions such as glove boxes, sticky pads, Vaseline barriers, safety suits, gloves, sticky tape, silicone vacuum grease, sticky trap paste, and micro mesh are used to safely contain ticks and prevent them from escaping.
Population control measuresEdit
With the possible exception of widespread DDT use in the Soviet Union, attempts to limit the population or distribution of disease-causing ticks have been quite unsuccessful. The parasitoid encyrtid wasp Ixodiphagus hookeri has been investigated for its potential to control tick populations. It lays its eggs into ticks;[a] the hatching wasps kill their hosts.
Predators and competitors of tick hosts can indirectly reduce the density of infected nymphs, thereby lowering tick-borne disease risk by lowering the density and/or tick burden of reservoir-competent hosts. A study in the Netherlands found that the number of larval ticks on bank voles and wood mice was lower at sites with significant red fox (Vulpes vulpes) and stone marten (Martes foina) activity.
This supports the results of a study from the northeastern United States, in which the incidence of Lyme borreliosis was negatively correlated with the density of red fox, possibly because foxes decrease the density of white-footed mice (Peromyscus leucopus), the most important reservoir-competent host for Borrelia burgdorferi.
Another natural form of control for ticks is the helmeted guineafowl, a bird species that consumes mass quantities of ticks. Opossums groom themselves, swallowing many ticks; they are net destroyers of ticks, killing around ninety percent of the ticks that attempt to feed on them. More generally, high animal diversity has a strongly protective effect against tick-borne disease.
Topical tick medicines may be toxic to animals and humans. The synthetic pyrethroid insecticide phenothrin in combination with the hormone analogue methoprene was a popular topical flea and tick therapy for felines. Phenothrin kills adult ticks, while methoprene kills eggs. Some products were withdrawn, and others are known to cause adverse reactions.
- Micrographs of the wasp laying eggs into a tick, and the hole by which the young wasps emerge from the tick's dead body, are available in Plantard et al 2012.
- "How ticks spread disease". Centers for Disease Control and Prevention. 21 September 2020. Retrieved 29 November 2020.
- "Ticks". CDC - DPDx. 23 January 2019. Retrieved 29 November 2020.
- Giribet, Gonzalo (March 2018). "Current views on chelicerate phylogeny—A tribute to Peter Weygoldt". Zoologischer Anzeiger. 273: 7–13. doi:10.1016/j.jcz.2018.01.004. S2CID 90344977.
- Beati, Lorenza; Klompen, Hans (7 January 2019). "Phylogeography of Ticks (Acari: Ixodida)". Annual Review of Entomology. 64 (1): 379–397. doi:10.1146/annurev-ento-020117-043027. ISSN 0066-4170. PMID 30354695. S2CID 53023797.
- Klompen H, Grimaldi D (2001). "First Mesozoic Record of a Parasitiform Mite: a Larval Argasid Tick in Cretaceous Amber (Acari: Ixodida: Argasidae)" (PDF). Annals of the Entomological Society of America. 94 (1): 10–15. doi:10.1603/0013-8746(2001)094[0010:FMROAP]2.0.CO;2.
- Peñalver E, Arillo A, Delclòs X, Peris D, Grimaldi DA, Anderson SR, et al. (December 2017). "Ticks parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages". Nature Communications. 8 (1): 1924. Bibcode:2017NatCo...8.1924P. doi:10.1038/s41467-017-01550-z. PMC 5727220. PMID 29233973.
- Chitimia-Dobler, Lidia; Mans, Ben J.; Handschuh, Stephan; Dunlop, Jason A. (n.d.). "A remarkable assemblage of ticks from mid-Cretaceous Burmese amber". Parasitology. 149 (6): 820–830. doi:10.1017/S0031182022000269. ISSN 0031-1820. PMID 35241194. S2CID 247227499.
- Dunlop JA, Apanaskevich DA, Lehmann J, Hoffmann R, Fusseis F, Ehlke M, et al. (October 2016). "Microtomography of the Baltic amber tick Ixodes succineus reveals affinities with the modern Asian disease vector Ixodes ovatus". BMC Evolutionary Biology. 16 (1): 203. doi:10.1186/s12862-016-0777-y. PMC 5057450. PMID 27724841.
- Guglielmone et al. (2010)
- Goddard (2008): p. 80
- Keirans et al. (1976)
- Molyneux (1993) p. 6
- Gu XB, Liu GH, Song HQ, Liu TY, Yang GY, Zhu XQ (July 2014). "The complete mitochondrial genome of the scab mite Psoroptes cuniculi (Arthropoda: Arachnida) provides insights into Acari phylogeny". Parasites & Vectors. 7: 340. doi:10.1186/1756-3305-7-340. PMC 4223567. PMID 25052180.
- Ruppert EE, Fox RS, Barnes RD (2004). Invertebrate Zoology (7th ed.). Cengage Learning. pp. 590–595. ISBN 978-81-315-0104-7.
- Wall & Shearer (2001): p. 55
- Richter D, Matuschka FR, Spielman A, Mahadevan L (December 2013). "How ticks get under your skin: insertion mechanics of the feeding apparatus of Ixodes ricinus ticks". Proceedings. Biological Sciences. 280 (1773): 20131758. doi:10.1098/rspb.2013.1758. ISSN 0962-8452. PMC 3826218. PMID 24174106.
- Sirois M (2015). Laboratory Procedures for Veterinary Technicians. St. Louis, MO: Elsevier. ISBN 978-0-323-16930-1.
- "Common Ticks". Illinois Department of Public Health. Retrieved 11 April 2014.
- "Soft ticks". CVBD: Companion Vector-Borne Diseases. Retrieved 6 December 2016.
- Sonenshine (2005): p. 14
- Nicholson et al. (2009): p. 486
- For Haller's organ, see also: Mehlhorn (2008): p. 582.
- Mitchell RD, Zhu J, Carr AL, Dhammi A, Cave G, Sonenshine DE, Roe RM (August 2017). "Infrared light detection by the haller's organ of adult american dog ticks, Dermacentor variabilis (Ixodida: Ixodidae)". Ticks and Tick-Borne Diseases. 8 (5): 764–771. doi:10.1016/j.ttbdis.2017.06.001. PMC 5588665. PMID 28647127.
- Yonge (15 March 2012). "Stuffed in a vacuum and bombarded by electrons, a tick waves hello". Discover.
- Miller M (20 November 2018). "UC study: Hungry ticks work harder to find you". UC Cincinnati.
- Rosendale AJ, Dunlevy ME, Fieler AM, Farrow DW, Davies B, Benoit JB (August 2017). "Dehydration and starvation yield energetic consequences that affect survival of the American dog tick". Journal of Insect Physiology. 101: 39–46. doi:10.1016/j.jinsphys.2017.06.012. PMID 28648807.
- Zimmer C (30 April 2013). "The Rise of the Tick". Outside.
- Gray JS, Kahl O, Lane RS, Levin ML, Tsao JI (July 2016). "Diapause in ticks of the medically important Ixodes ricinus species complex". Ticks and Tick-Borne Diseases. 7 (5): 992–1003. doi:10.1016/j.ttbdis.2016.05.006. PMC 5659180. PMID 27263092.
- "Ticks are even tougher and nastier than you thought". Science Daily. 25 September 2017.
- Walker JB, Keirans JE, Horak IG (2005). The Genus Rhipicephalus (Acari, Ixodidae): A Guide to the Brown Ticks of the World. Cambridge University Press. p. 39. ISBN 978-1-316-58374-6.
- Salman MD, Tarrés-Call J, Estrada-Peña A (2013). Ticks and Tick-borne Diseases: Geographical Distribution and Control Strategies in the Euro-Asia Region. CABI. pp. 6–12. ISBN 978-1-84593-853-6.
- "Soft ticks". CVBD: Companion Vector-Borne Diseases. Retrieved 6 December 2016.
- Roshdy et al. (1983)
- Brouwers L (30 August 2011). "Long Lost Relative of Ticks Pops Up Again". Scientific American. Retrieved 4 December 2016.
- "Life cycle of Hard Ticks that Spread Disease". Centers for Disease Control and Prevention. Retrieved 22 June 2013.
- Mans BJ, Louw AI, Neitz AW (October 2002). "Evolution of hematophagy in ticks: common origins for blood coagulation and platelet aggregation inhibitors from soft ticks of the genus Ornithodoros". Molecular Biology and Evolution. 19 (10): 1695–705. doi:10.1093/oxfordjournals.molbev.a003992. ISSN 1537-1719. PMID 12270896.
- Goddard (2008): p. 82
- "Host seeking". CVBD: Companion Vector-Borne Diseases. Retrieved 8 December 2016.
- Allan (2001)
- "Hard ticks". CVBD: Companion Vector-Borne Diseases. Retrieved 6 December 2016.
- University of Oxford (27 June 2017). "From bug to drug—tick saliva could be key to treating heart disease". Phys.org.
- Duron O, Gottlieb Y (October 2020). "Convergence of Nutritional Symbioses in Obligate Blood Feeders" (PDF). Trends in Parasitology. 36 (10): 816–825. doi:10.1016/j.pt.2020.07.007. PMID 32811753. S2CID 221181791.
- Binetruy F, Buysse M, Lejarre Q, Barosi R, Villa M, Rahola N, et al. (March 2020). "Microbial community structure reveals instability of nutritional symbiosis during the evolutionary radiation of Amblyomma ticks" (PDF). Molecular Ecology. 29 (5): 1016–1029. doi:10.1111/mec.15373. PMID 32034827. S2CID 211065648.
- Duron O, Binetruy F, Noël V, Cremaschi J, McCoy KD, Arnathau C, et al. (June 2017). "Evolutionary changes in symbiont community structure in ticks". Molecular Ecology. 26 (11): 2905–2921. doi:10.1111/mec.14094. hdl:10067/1422810151162165141. PMID 28281305. S2CID 40962020.
- Buysse M, Plantard O, McCoy KD, Duron O, Menard C (June 2019). "Tissue localization of Coxiella-like endosymbionts in three European tick species through fluorescence in situ hybridization" (PDF). Ticks and Tick-Borne Diseases. 10 (4): 798–804. doi:10.1016/j.ttbdis.2019.03.014. PMID 30922601.
- Duron O, Morel O, Noël V, Buysse M, Binetruy F, Lancelot R, et al. (June 2018). "Tick-Bacteria Mutualism Depends on B Vitamin Synthesis Pathways". Current Biology. 28 (12): 1896–1902.e5. doi:10.1016/j.cub.2018.04.038. PMID 29861133. S2CID 44095809.
- Lalzar I, Friedmann Y, Gottlieb Y (December 2014). "Tissue tropism and vertical transmission of Coxiella in Rhipicephalus sanguineus and Rhipicephalus turanicus ticks". Environmental Microbiology. 16 (12): 3657–68. doi:10.1111/1462-2920.12455. ISSN 1462-2920. PMID 24650112.
- Guizzo MG, Parizi LF, Nunes RD, Schama R, Albano RM, Tirloni L, et al. (December 2017). "A Coxiella mutualist symbiont is essential to the development of Rhipicephalus microplus". Scientific Reports. 7 (1): 17554. Bibcode:2017NatSR...717554G. doi:10.1038/s41598-017-17309-x. ISSN 2045-2322. PMC 5730597. PMID 29242567.
- Ben-Yosef M, Rot A, Mahagna M, Kapri E, Behar A, Gottlieb Y (22 April 2020). "Rhipicephalus sanguineus Is Required for Physiological Processes During Ontogeny". Frontiers in Microbiology. 11: 493. doi:10.3389/fmicb.2020.00493. ISSN 1664-302X. PMC 7188774. PMID 32390951.
- Smith TA, Driscoll T, Gillespie JJ, Raghavan R (January 2015). "A Coxiella-like endosymbiont is a potential vitamin source for the Lone Star tick". Genome Biology and Evolution. 7 (3): 831–8. doi:10.1093/gbe/evv016. PMC 4994718. PMID 25618142.
- Duron O, Sidi-Boumedine K, Rousset E, Moutailler S, Jourdain E (November 2015). "The Importance of Ticks in Q Fever Transmission: What Has (and Has Not) Been Demonstrated?" (PDF). Trends in Parasitology. 31 (11): 536–552. doi:10.1016/j.pt.2015.06.014. ISSN 1471-4922. PMID 26458781. S2CID 25636125.
- Duron O (September 2015). "The IS1111 insertion sequence used for detection of Coxiella burnetii is widespread in Coxiella-like endosymbionts of ticks". FEMS Microbiology Letters. 362 (17): fnv132. doi:10.1093/femsle/fnv132. ISSN 0378-1097. PMID 26269380.
- Magnarelli (2009)
- Nuttall (1905)
- "Lyme and Other Tickborne Diseases Increasing". Centers for Disease Control. 21 October 2021. Retrieved 4 March 2022.
- Chrobak, Ula (3 February 2022). "Lyme and other tick-borne diseases are on the rise. But why?". Knowable Magazine. doi:10.1146/knowable-020222-1. Retrieved 4 March 2022.
- Gilbert, Lucy (7 January 2021). "The Impacts of Climate Change on Ticks and Tick-Borne Disease Risk". Annual Review of Entomology. 66 (1): 373–388. doi:10.1146/annurev-ento-052720-094533. ISSN 0066-4170. PMID 33417823. S2CID 231300522. Retrieved 4 March 2022.
- Dantas-Torres F, Oliveira-Filho EF, Soares FA, Souza BO, Valença RB, Sá FB (2008). "Ticks infesting amphibians and reptiles in Pernambuco, Northeastern Brazil". Revista Brasileira de Parasitologia Veterinaria. 17 (4): 218–21. doi:10.1590/S1984-29612008000400009. PMID 19265581.
- "Ticks of Livestock". Ectoparasites of Livestock. Butox. Retrieved 14 January 2017.
- "tropical bont tick - Amblyomma variegatum". entnemdept.ufl.edu. Retrieved 29 November 2020.
- "Ticks". Livestock Veterinary Entomology. Texas A&M AgriLife. Retrieved 14 January 2017.
- Beans C (20 July 2016). "Taking The Battle Against Lyme Disease Ticks To The Backyard". NPR.
- "Integrated Tick Management" (PDF). Connecticut Agricultural Experimental Station.
- Tucker B (11 May 2018). "The tick-resistant yard". Dirt Magazine.
- Hoogstraal H, Kaiser MN, Traylor MA, Guindy E, Gaber S (1963). "Ticks (Ixodidae) on birds migrating from Europe and Asia to Africa 1959-61". Bulletin of the World Health Organization. 28 (2): 235–62. PMC 2554471. PMID 13961632.
- Ray CC (28 May 2012). "The mighty tick". New York Times. Retrieved 15 December 2016.
- "Disease transmission". CVBD: Companion Vector-Borne Diseases. Retrieved 9 December 2016.
- Dennis & Piesman (2005): p. 5
- Sonenshine D (1991). Biology of Ticks. New York: Oxford University Press.
- Aeschlimann & Freyvogel, 1995: p. 182
- Mans BJ, de Klerk D, Pienaar R, Latif AA (17 August 2011). "Nuttalliella namaqua: a living fossil and closest relative to the ancestral tick lineage: implications for the evolution of blood-feeding in ticks". PLOS ONE. 6 (8): e23675. Bibcode:2011PLoSO...623675M. doi:10.1371/journal.pone.0023675. ISSN 1932-6203. PMC 3157464. PMID 21858204.
- Wenner, Melinda (11 June 2021). "Let's Do a Tick Check - These pervasive bloodsuckers can give you more than just Lyme disease. Here's how to protect yourself. (Interactive)". The New York Times. Retrieved 19 June 2021.
- Unsworth NB, Stenos J, Graves SR, Faa AG, Cox GE, Dyer JR, et al. (April 2007). "Flinders Island spotted fever rickettsioses caused by "marmionii" strain of Rickettsia honei, Eastern Australia". Emerging Infectious Diseases. 13 (4): 566–73. doi:10.3201/eid1304.050087. PMC 2725950. PMID 17553271.
- "Q fever". Centers for Disease Control. Retrieved 7 November 2010.
- "Heartland virus". 8 November 2018.
- Eisen RJ, Kugeler KJ, Eisen L, Beard CB, Paddock CD (December 2017). "Tick-Borne Zoonoses in the United States: Persistent and Emerging Threats to Human Health". ILAR Journal. 58 (3): 319–335. doi:10.1093/ilar/ilx005. ISSN 1084-2020. PMC 5610605. PMID 28369515.
- Feldman G, Feldman L, Macnair P (6 March 2014). "All about ticks: why it's so important to remove a tick". Netdoctor. Retrieved 8 December 2016.
- "Correct tick removal". 26 October 2015. Retrieved 27 January 2018.
- "Tick removal". Lyme Disease Action. Retrieved 24 October 2014.
- "Tick removal". Centers for Disease Control and Prevention. Retrieved 24 October 2014.
- "Catalyst: Tick allergy – ABC TV Science". www.abc.net.au. 17 February 2015. Retrieved 10 December 2015.
- Salleh A (1 January 2020). "Tweeze vs freeze: Here's the lowdown on how to get rid of a tick". ABC News. Retrieved 15 February 2020.
- "TIARA - Tick Induced Allergies Research and Awareness". TIARA - Tick Induced Allergies Research and Awareness. Retrieved 15 February 2020.
- Atwell T (3 January 2016). "Pesticides may get rid of ticks, but at what cost?". Press Herald.
- Figura D (4 June 2014). "Outdoors experts: Keep ticks off by spraying repellent on your clothes". Syracuse.com.
- Aubrey A (25 June 2018). "Red Meat Allergies Caused By Tick Bites Are On The Rise". NPR. Retrieved 26 June 2018.
- Thangamani S, Bente D (July 2014). "Establishing protocols for tick containment at Biosafety Level 4". Pathogens and Disease. 71 (2): 282–5. doi:10.1111/2049-632X.12187. PMC 4107070. PMID 24838773.
- Dennis & Piesman, 2005: p. 3
- Plantard O, Bouju-Albert A, Malard MA, Hermouet A, Capron G, Verheyden H (2012). "Detection of Wolbachia in the tick Ixodes ricinus is due to the presence of the hymenoptera endoparasitoid Ixodiphagus hookeri". PLOS ONE. 7 (1): e30692. Bibcode:2012PLoSO...730692P. doi:10.1371/journal.pone.0030692. PMC 3266912. PMID 22292021.
- Tijsse-Klasen E, Braks M, Scholte EJ, Sprong H (December 2011). "Parasites of vectors--Ixodiphagus hookeri and its Wolbachia symbionts in ticks in The Netherlands". Parasites & Vectors. 4: 228. doi:10.1186/1756-3305-4-228. PMC 3248373. PMID 22152674.
- Hofmeester TR, Jansen PA, Wijnen HJ, Coipan EC, Fonville M, Prins HH, et al. (July 2017). "Cascading effects of predator activity on tick-borne disease risk". Proceedings. Biological Sciences. 284 (1859): 20170453. doi:10.1098/rspb.2017.0453. PMC 5543215. PMID 28724731. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
- Levi T, Kilpatrick AM, Mangel M, Wilmers CC (July 2012). "Deer, predators, and the emergence of Lyme disease". Proceedings of the National Academy of Sciences of the United States of America. 109 (27): 10942–7. Bibcode:2012PNAS..10910942L. doi:10.1073/pnas.1204536109. PMC 3390851. PMID 22711825.
- Duffy et al. (1992)
- Main D (13 June 2018). "'Destroyers of ticks': How opossums help fight ticks and Lyme Disease". Boston 25 News.
- "Hartz flea and tick drops for cats and kittens to be phased out". Environmental Protection Agency. 2005. Archived from the original on 11 January 2010.
- Aeschlimann A, Freyvogel TA (1995). "Biology and distribution of ticks of medical importance". In Meier J, White J (eds.). Handbook of Clinical toxicology of Animal Venoms and Poisons. Vol. 236. CRC Press. pp. 177–189. ISBN 978-0-8493-4489-3.
- Allan SA (2001). "Ticks (Class Arachnida: Order Acarina)". In Samuel WM, Pybus MJ, Kocan AA (eds.). Parasitic Diseases of Wild Mammals. Wiley-Blackwell. pp. 72–106. ISBN 978-0-8138-2978-4.
- Dennis DT, Piesman JF (2005). "Overview of tick-borne infections of humans". In Goodman JL, Dennis DT, Sonenshine DE (eds.). Tick-borne Diseases of Humans. ASM Press. pp. 3–11. ISBN 978-1-55581-238-6.
- Duffy DC, Downer R, Brinkley C (1992). "The effectiveness of Helmeted Guineafowl in the control of the deer tick, the vector of Lyme disease" (PDF). Wilson Bulletin. 104 (2): 342–345.
- de la Fuente J (2003). "The fossil record and the origin of ticks (Acari: Parasitiformes: Ixodida)". Experimental & Applied Acarology. 29 (3–4): 331–44. doi:10.1023/A:1025824702816. PMID 14635818. S2CID 11271627.
- Goddard J (2008). "Tick-borne diseases". Infectious Diseases and Arthropods. Springer. ISBN 978-1-60327-399-2.
- Guglielmone AA, Robbins RG, Apanaskevich DA, Petney TN, Estrada-Pena A, Horak IG, Shao R, Barker SC (2010). "The Argasidae, Ixodidae and Nuttalliellidae (Acari: Ixodida) of the world: a list of valid species names" (PDF). Zootaxa. 2528: 1–28. doi:10.5281/zenodo.196488.
- Keirans JE, Clifford CM, Hoogstraal H, Easton ER (1976). "Discovery of Nuttalliella namaqua Bedford (Acarina: Ixodoidea: Nuttalliellidae) in Tanzania and redescription of the female based on scanning electron microcopy". Annals of the Entomological Society of America. 69 (5): 926–932. doi:10.1093/aesa/69.5.926.
- Magnarelli LA (2009). "Global importance of ticks and associated infectious disease agents". Clinical Microbiology Newsletter. 31 (5): 33–37. doi:10.1016/j.clinmicnews.2009.02.001.
- Mehlhorn H, Armstrong PM, eds. (2001). "Ticks". Encyclopedic Reference of Parasitology. Springer. pp. 608–638. ISBN 978-3-540-66819-0.
- Molyneux DH (1993). "Vectors". In Cox FE (ed.). Modern Parasitology: a Textbook of Parasitology (2nd ed.). Wiley-Blackwell. pp. 53–74. ISBN 978-0-632-02585-5.
- Nicholson WL, Sonenshine DE, Noden BH, Brown RN (2009). "Ticks (Ixodida)". In Mullen G, Durden L (eds.). Medical and Veterinary Entomology. Academic Press. pp. 483–532. ISBN 978-0-12-372500-4.
- Nuttall GH (1905). "Ticks and tick-transmitted diseases". Transactions of the Epidemiological Society of London. 24: 12–26. PMC 5548484. PMID 29419268.
- Roshdy MA, Hoogstraal H, Banaja AA, El Shoura SM (1983). "Nuttalliella namaqua (Ixodoidea: Nuttalliellidae): spiracle structure and surface morphology". Parasitology Research. 69 (6): 817–821. doi:10.1007/BF00927431. S2CID 33872322.
- Sonenshine DE (2005). "The biology of tick vectors of human disease". In Goodman JL, Dennis DT, Sonenshine DE (eds.). Tick-borne Diseases of Humans. ASM Press. pp. 12–36. ISBN 978-1-55581-238-6.
- Wall R, Shearer D (2001). "Ticks (Acari)". Veterinary Ectoparasites: Biology, Pathology, and Control. John Wiley & Sons. pp. 55–82. ISBN 978-0-632-05618-7.
- Media related to Ixodida at Wikimedia Commons
- Parasitic Insects, Mites and Ticks: Genera of Medical and Veterinary Importance at Wikibooks