Ticks 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.
The Argasidae are the family of soft ticks, one of the three families of ticks. The family contains 193 species, although the composition of the genera is less certain, and more study is needed before the genera can become stable. The currently accepted genera are Antricola, Argas, Nothoaspis, Ornithodoros, and Otobius. The Argasidae are very common in South Asia, along with 96 other species of ticks, making South Asia the region with the highest biodiversity of ticks worldwide. Soft ticks are resistant to desiccation and can live for several years in arid conditions.
Tick-borne diseases, which afflict humans and other animals, are caused by infectious agents transmitted by tick bites. They are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. The economic impact of tick-borne diseases is considered to be substantial in humans, and tick-borne diseases are estimated to affect ~80 % of cattle worldwide. Most of these pathogens require passage through vertebrate hosts as part of their life cycle. Tick-borne infections in humans, farm animals, and companion animals are primarily associated with wildlife animal reservoirs. many tick-borne infections in humans involve a complex cycle between wildlife animal reservoirs and tick vectors. The survival and transmission of these tick-borne viruses are closely linked to their interactions with tick vectors and host cells. These viruses are classified into different families, including Asfarviridae, Reoviridae, Rhabdoviridae, Orthomyxoviridae, Bunyaviridae, and Flaviviridae.
Nuttalliella namaqua is a tick found in southern Africa from Tanzania to Namibia and South Africa, which is placed in its own family, Nuttalliellidae. It can be distinguished from ixodid ticks and argasid ticks by a combination of characteristics including the position of the stigmata, lack of setae, strongly corrugated integument, and form of the fenestrated plates. It is the most basal lineage of ticks.
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. 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.
Ixodes is a genus of hard-bodied ticks. It includes important disease vectors of animals and humans, and some species inject toxins that can cause paralysis. Some ticks in this genus may transmit the pathogenic bacterium Borrelia burgdorferi responsible for causing Lyme disease. Additional organisms that may be transmitted by Ixodes are parasites from the genus Babesia, which cause babesiosis, and bacteria from the related genus Anaplasma, which cause anaplasmosis.
Rhipicephalus sanguineus, commonly called the brown dog tick, kennel tick, or pantropical dog tick, is a species of tick found worldwide, but more commonly in warmer climates. This species is unusual among ticks in that its entire lifecycle can be completed indoors. The brown dog tick is easily recognized by its reddish-brown color, elongated body shape, and hexagonal basis capituli. Adults are 2.28 to 3.18 mm in length and 1.11 to 1.68 mm in width. They do not have ornamentation on their backs.
Dermacentor is a genus of ticks in the family Ixodidae, the hard ticks. The genus has a cosmopolitan distribution, with native species on all continents except Australia. Most are found in North America.
Rhipicephalus is a genus of ticks in the family Ixodidae, the hard ticks, consisting of about 74 or 75 species. Most are native to tropical Africa.
Ixodes pacificus, the western black-legged tick, is a species of parasitic tick found on the western coast of North America. I. pacificus is a member of the family Ixodidae. It is the principal vector of Lyme disease in that region. I. pacificus typically feeds on lizards and small mammals therefore its rate of transmission of Lyme disease to humans is around 1% of adults. It is an ectoparasite that attaches itself to the outside of its host and feeds on the host's blood. It can have a heteroxenous lifestyle or monoxenous life cycle depending on how many hosts it feeds on in each cycle. I. pacificus has a four stage life cycle that takes around 3 years to complete. These stages include egg, larva, nymph, and adult. They prefer dense woodland habitats or areas of brush and tall grass.
Ornithodoros is a genus in the soft-bodied tick family, Argasidae.
Ticks of domestic animals directly cause poor health and loss of production to their hosts. Ticks also transmit numerous kinds of viruses, bacteria, and protozoa between domestic animals. These microbes cause diseases which can be severely debilitating or fatal to domestic animals, and may also affect humans. Ticks are especially important to domestic animals in tropical and subtropical countries, where the warm climate enables many species to flourish. Also, the large populations of wild animals in warm countries provide a reservoir of ticks and infective microbes that spread to domestic animals. Farmers of livestock animals use many methods to control ticks, and related treatments are used to reduce infestation of companion animals.
Ornithodoros savignyi, known as sand tampan, African eyed tampan or Kalahari sand tampan, is one of some 37 species in the genus Ornithodoros and is a soft tick with a leathery, mammillated integument, causing paralysis and tampan toxicosis, two unrelated conditions. The sand tampan is an ectoparasite on humans, their livestock and wild animals, including birds and bats. Occurring in semi-desert areas of Africa, Saudi Arabia and other parts of the Persian Gulf, India, Sri Lanka and into Asia, it is able to survive for lengthy periods without feeding, spending most of its life burrowed under sand or loose soil, often in wait for animals that rest or sleep under trees or in the lee of rocks, but also in places where people or their animals congregate such as marketplaces, places of worship, cattle kraals and village squares. The timing of its activity is geared to coincide with that of potential hosts, but hot sunny conditions are usually avoided. Because of its habit of feeding and dropping from its host, adult dispersal is limited, whereas larvae may remain attached to their hosts for several days. During its life cycle it will feed on multiple hosts between moults.
Dermacentor reticulatus, also known as the ornate cow tick, ornate dog tick, meadow tick, and marsh tick, is a species of tick from the family Ixodidae. It is the type species for the genus Dermacentor. D. reticulatus is an ornate tick. The female varies in size from 3.8–4.2 mm (unfed) to 10 mm when engorged after feeding. The unfed male is 4.2–4.8 mm long. D. reticulatus is found in Europe and Western Asia, generally in wooded areas.
The zebra tick or yellow back tick is a species of hard tick. It is common in the Horn of Africa, with a habitat of the Rift Valley and eastward. It feeds upon a wide variety of species, including livestock, wild mammals, and humans, and can be a vector for various pathogens. The adult male has a distinctive black and ivory ornamentation on its scutum.
Maria Vladimirovna Pospelova-Shtrom (1902–1991) was a 20th century parasitologist best known for her work delineating the biology and public health importance of ticks in western Asia and eastern Europe, contributing to the reduction of the incidence of tick-borne diseases, especially tick-borne relapsing fever.
Ixodes angustus is a species of parasitic tick, whose range encompasses the majority of Canada and the United States, along with parts of northern Mexico. I. angustus is a member of the Ixodidae (hard-bodied) family of ticks. It is most abundant in cool, moist biomes such as riparian, boreal or montane zones. I. angustus is a host generalist and has been discovered feeding on more than 90 different host species, including humans and domestic dogs. I. angustus has been identified as a potential vector for Lyme disease but is not considered a principal vector due to the relative rarity with which it feeds on humans.
Ixodes tasmani, colloquially known as the common marsupial tick, is an Australian species of hard-bodied tick. It is a common vector for certain pathogens. There are around 70 species of ticks found in Australia, 16 of which, Ixodes tasmani included, are able to parasitize humans.
Natalia Aleksandrovna Filippova was a world authority on the taxonomy of mites and especially ticks. Her monographs on the identification, morphology, development, distribution and behaviour of the family Argasidae and the sub-families of Ixodinae and Amblyomminae are standard works on these important vectors of disease.
