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Arthropod-borne virus encephalitis
Published in Avindra Nath, Joseph R. Berger, Clinical Neurovirology, 2020
Colorado tick fever (CTF) is usually a self-limited febrile illness, but it can be complicated by neurological involvement [97]. Caused by a virus in the Coltivirus genus of the Reoviridae family, it is transmitted by Dermacentor andersoni ticks [98]. Often found in persons who work or have recreation in the Rocky Mountains [99], it has for years been confused with Rocky Mountain spotted fever. However, CTF is often distinguished by a biphasic, or saddlebacked, fever pattern and leukopenia. Rash, while occasionally found, is infrequent. The onset is abrupt with fever, headache and muscle aches. Duration of illness is seven to 10 days, punctuated often by a two to three day afebrile period midway in the course. Neurological complications include meningitis, meningoencephalitis, and encephalitis [97,98,100]. Virus isolation can be achieved from the blood throughout the febrile course. No treatment or preventative measure is currently available for CTF [101].
Ticks
Published in Gail Miriam Moraru, Jerome Goddard, The Goddard Guide to Arthropods of Medical Importance, Seventh Edition, 2019
Gail Miriam Moraru, Jerome Goddard
Colorado tick fever (CTF) is a generally moderate, acute, self-limited, febrile illness caused by a Coltivirus in the Reoviridae. Typically, the onset of CTF is sudden, with chilly sensations, high fever, headache, photophobia, mild conjunctivitis, lethargy, myalgias, and arthralgias. The body temperature pattern may be biphasic, with a 2- to 3-day febrile period, a remission lasting 1 to 2 days, then another 2 to 3 days of fever, sometimes with more severe symptoms.80 Rarely, the disease may be worse in children with encephalitis, myocarditis, or tendency to bleed. Infrequently, a transient rash may accompany infection. Recovery is usually prompt, but patients may be hospitalized or even (rarely) die. In one study of 91 cases, 18% were hospitalized.81 CTF occurs in areas above 4000 feet in at least 11 western states (South Dakota, Montana, Wyoming, Colorado, New Mexico, Utah, Idaho, Nevada, Washington, Oregon, and California) and in British Columbia and Alberta, Canada. Exact case numbers are difficult to ascertain, as many cases may be mild and sick persons fail to seek medical care, but approximately 200 to 400 cases are reported in the United States annually. Peak incidence is during April and May at lower elevations and during June and July at higher elevations. The virus is maintained in nature by cycles of infection among various small mammals and the ticks that parasitize them. Infection in humans is by the bite of an infected tick. Several tick species have been found infected with the virus, but Dermacentor andersoni is by far the most common. This tick is especially prevalent where there is brushy vegetation to provide good protection for small mammalian hosts of immature ticks and yet with sufficient forage to attract large hosts required for the adults.
Ticks
Published in Jerome Goddard, Public Health Entomology, 2022
Viruses associated with ticks. Tick-borne encephalitis (TBE) is a disease complex encompassing at least three syndromes caused by closely related viruses spanning from the British Isles (Louping ill), across Europe (Central European tick-borne encephalitis), to far-eastern Russia [Russian spring-summer encephalitis (RSSE)] (Figure 10.12). In Central Europe the typical case has a biphasic course with an early, viremic, flulike stage, followed about a week later by the appearance of signs of meningoencephalitis.15 Central nervous system (CNS) disease is relatively mild, but occasional severe motor dysfunction and permanent disability occur. Powassan encephalitis (POW)—also in the TBE subgroup—is a relatively rare infection of humans that mostly occurs in the northeastern United States and adjacent regions of Canada. Characteristically, there is sudden onset of fever with temperature up to 40°C along with convulsions. Also, accompanying encephalitis is usually severe, characterized by vomiting, respiratory distress, and prolonged, sustained fever. Cases of POW are still relatively rare in North America, although its reported incidence is increasing.4,16 There were 21 cases reported in 2018.4 Colorado tick fever is a moderate, self-limiting febrile tick-borne illness occurring in the Rocky Mountain region of the United States and Canada. The primary vector is Dermacentor andersoni. Small mammals such as ground squirrels and the ticks themselves serve as reservoirs of the virus. Crimean-Congo hemorrhagic fever is a rather serious tick-borne illness occurring in many countries in central and eastern Europe, Russia, China, India, Pakistan, the Middle East, and parts of Africa. Transmission is mainly by Hyalomma marginatum and other closely related species. Rabbits, cattle, and goats are believed to be the reservoir hosts. Kyasanur forest disease, transmitted primarily by Haemaphysalis spinigera and related species, occurs in southern India. The disease is believed to be contracted by people working in/near the Kyasanur forest or cattle grazing at the forest edge. In the last decade, several new tick-borne viruses have been identified. Heartland virus (a Phlebovirus) is associated with the Lone Star tick, Amblyomma americanum and has been recognized in Missouri, Oklahoma, Kentucky, and Tennessee.17,18 Only about 50 cases of Heartland virus have been identified. A couple of cases of a new Thogotovirus called Bourbon virus have been identified in the Midwest and southern United States with an unknown tick vector.19 Evidence suggests the lone star tick may be a potential vector.20
How relevant are in vitro culture models for study of tick-pathogen interactions?
Published in Pathogens and Global Health, 2021
Cristiano Salata, Sara Moutailler, Houssam Attoui, Erich Zweygarth, Lygia Decker, Lesley Bell-Sakyi
In the first report describing the in vitro growth of an arbovirus in tick organ cultures, the kinetics of replication of Colorado tick fever virus (CTFV) were followed in vector (D. andersoni) developing adult explants [15]. A latent phase of ~10 days preceded detection of active viral replication, the virus persisted in the tissues until 166 days post infection, and the titer in the medium decreased with the senescence of the organ culture. Moreover, using nymphal ticks infected by feeding on viremic animals, CTFV replicated at much higher levels in vitro in developing adult explants than in vivo in live, intact ticks, showing the efficiency of this system for virus propagation.