Colorado tick fever
| Colorado tick fever virus | |
|---|---|
| Virus classification | |
| Group: | Group III (dsRNA) |
| Order: | Unassigned |
| Family: | Reoviridae |
| Subfamily: | Spinareovirinae |
| Genus: | Coltivirus |
| Species: | Colorado tick fever virus |
| Colorado tick fever | |
|---|---|
| Classification and external resources | |
| Specialty | Infectious disease |
| ICD-10 | A93.2 |
| ICD-9-CM | 066.1 |
| DiseasesDB | 31134 |
| MedlinePlus | 000675 |
| eMedicine | emerg/586 |
| MeSH | D003121 |
Colorado tick fever (CTF) (also called mountain tick fever, American tick fever, and American mountain tick fever) is a viral infection (Coltivirus) transmitted from the bite of an infected Rocky Mountain wood tick (Dermacentor andersoni). It should not be confused with the bacterial tick-borne infection, Rocky Mountain spotted fever.
The type species of the genus Coltivirus, Colorado tick fever virus (CTFV) infects haemopoietic cells, particularly erythrocytes, which explains how the virus is transmitted by ticks and also accounts for the incidence of transmission by blood transfusion.
The disease develops from March to September, with the highest infections occurring in June. The disease is found almost exclusively in the western United States and Canada, mostly in high mountain areas such as Colorado and Idaho. The CTFV was first isolated from human blood in 1944.
The virus particle, like other coltiviruses, is about 80 nm in diameter and is generally not enveloped. The double-stranded RNA viral genome is about 20,000 bp long and is divided into 12 segments, which are termed Seg-1 to Seg-12. Viral replication in infected cells is associated with characteristic cytoplasmic granular matrices. Evidence suggests viral presence in mature erythrocytes is a result of replication of the virus in hematopoitic erythrocyte precursor cells and simultaneous maturation of the infected immature cells rather than of direct entry and replication of CTFV in mature erythrocytes.
The Rocky Mountain wood tick is usually found attached to a host, but when it is without a host, it hides in cracks and crevices, as well as soil. If for some reason the tick is not able to find a host before the winter, it will stay under groundcover until spring, when it can resume its search. The wood tick does not typically seek hosts in the hottest summer months. Adult ticks tend to climb to the tops of grasses or low shrubs, attaching themselves to a host wandering by. They secure the attachment by secreting a cement-like substance from their mouths, inserting it into the host.
Colorado tick fever is acquired by tick bite. No evidence of natural person-to-person transmission has been found. However, rare cases of transmission from blood transfusions have been reported. The virus which causes Colorado tick fever may stay in the blood for as long as four months after onset of the illness.
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