Colorado tick fever

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Colorado Tick Fever (CTF) (also called Mountain tick fever, Mountain fever, and American mountain fever) is an acute viral infection transmitted from the bite of an infected wood tick (Dermacentor andersoni). A species of the genus Coltivirus, Colorado tick fever virus (CTFV) infects haemopoietic cells, particularly erythrocytes, which explains the viral pathway of transmission within bloodsucking ticks and also accounts for the incidence of transmission via blood transfusion. 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. [2]The virus particle, like other Coltiviruses, is ~80 nm in diameter and is generally non-envolped. The double stranded RNA viral genome is ~20,000bp 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 that 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 off direct entry and replication of CTFV in mature erythrocytes.[3]

Colorado tick fever remains a rare disease without a well established historical perspective.

There is currently no classification system established for Colorado tick fever.

Colorado tick fever is an Orbivirus or Coltivirus that chronically infects Rocky Mountain wood ticks. The virus typically infects cells in bone marrow causing issues with the development of certain blood cells. Infection is transmitted by the bite of an infected Rocky Mountain wood tick.

Colorado tick fever (CTF) must be differentiated from other diseases that cause fever,chills, headaches, body ache, and rash. When trying to differentiate CTF from other infections, it is important to recognize that the clinical manifestations of CTF greatly resemble those of other tick-borne illnesses, especially those caused by the Rickettsiae family. Examples of misdiagnoses, with the umbrella of tick-borne diseases include typhus-spotted fevers and Ehrlichiosis.

Colorado tick fever remains a rare disease with only 83 cases reported between the years of 2002 and 2012. Incidence of the disease remain primarily confined to the Rocky Mountain States, with a few outliers throughout the United States. Incidence of Colorado tick fever appears to be independent of both demographic and age. ^[1]

The primary risk factors associated with Colorado tick fever are exposure to endemic environment and the time of that exposure. Rocky Mountain wood ticks have been identified as the primary vector of Colorado tick fever infections, thus being bitten in an endemic area may result in the contraction of the disease.

First signs of symptoms can occur about 3-6 days after the initial tick bite, although it can have incubation periods of up to 20 days. Patients usually experience a two-staged fever and illness which can continue for three days, diminish, and then return for another episode of 1-3 days. The virus has the ability to live in the blood stream for up to 120 days; therefore coming in contact without proper precautions and the donation of blood are prohibited.

Initial symptoms include: fever, chills, headaches,pain behind the eyes, light sensitivity, muscle pain, generalized malaise abdominal pain, nausea, vomiting as well as a flat or pimply rash. [4] During the second phase of the virus a high fever can return with an increase in symptoms. Colorado tick fever can be very severe in cases involving children and have even required hospitalization. Complications with this disease have included aseptic meningitis, encephalitis, and hemorrhagic fever but these are rare.

Colorado tick fever will display itself with a multitude of clinical manifestations. The most common clinical manifestations associated with Colorado tick fever are fever, chills, headache, body aches, and lethargy.

Early onset signs include fever, lethargy, and overall weakness. As the infection progresses, further clinical manifestations will present themselves in the form of tachycardia, changes in blood pressure, sensitivity of the eye and skin, and the appearance of a rash. Signs may appear to be similar to other diseases within the umbrella of tick-borne fevers however a biphasic fever is a characteristic sign of a Colorado tick fever infection.

A combination of laboratory tests can confirm the likely hood of a Colorado tick fever infection. An Immunofluoresence assay remains the gold standard in testing for infection. Other tests include complement fixation to the viral components that cause Colorado tick fever or acute and convalescent serology. ^[2]

There is currently no specific treatment for Colorado tick fever. Supportive treatment is currently the primary method in care. Certain cases, depending on severity, will require hospitalization.

Colorado tick fever prevention strategies are based on avoiding potential, infected, tick bites. Avoiding tick bites may be accomplished through limited exposure to endemic areas. However if it is impossible or impractical to avoid these areas, several preventative strategies may be implemented. These strategies are indicated under the Prevention title below. Other prevention strategies include a proper removal of the tick. This process is also outlined below under the title, the best way to remove a tick.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Colorado tick fever remains a rare disease without a well established historical perspective.

• Colorado tick fever is a rare disease.
• Majority of information collected regarding CTF has been done over the past 15 years.
• Colorado tick fever remains a non-notifiable disease to the Centers for Disease Control and Prevention. ^[1]

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Colorado tick fever is an Orbivirus or Coltivirus that chronically infects Rocky Mountain wood ticks. The virus typically infects cells in bone marrow causing issues with the development of certain blood cells. Infection is transmitted by the bite of an infected Rocky Mountain wood tick.

• Genera of Colorado tick fever is wither an Orbivirus or Coltivirus.
• Four serotypes are responsible for human infections.^[1]

• Viral pathway involves targeting the cells in bone marrow or young child’s central nervous system.
• Inhibits the proper development of blood cells.
• A host defense mechanism, humoral immunity, is elicited by infection.^[1]

• Infection with Colorado tick fever occurs as a result of being bitten by an infected Rocky Mountain wood tick (Dermacentor andersoni).
• Colorado tick fever is transmitted to a tick during a blood meal involving a rodent reservoir such as a squirrels, chipmunks, and mice.
• Infection perpetuates as a tick continues to feed on another host.
• Viral transmission from human to human is rare, however may occur during blood transfusion.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Colorado Tick Fever (CTF) (also called Mountain tick fever, Mountain fever, and American mountain fever) is an acute viral infection transmitted from the bite of an infected 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 the virus transmission process by bloodsucking ticks and also accounts for the incidence of transmission via blood transfusion. The disease develops from March to September, with the highest infections occurring in May and June. [2] 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. [3]

• The Rocky Mountain wood tick is the primary host for Colorado tick fever.
• 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 months, it will stay under ground until spring when it can resume its search.
• The wood tick typically does not seek out available hosts in the hottest summer months as well.
• Adult ticks, for the most part, tend to climb to the top of grass and low shrubs to attach themselves to a host that is wandering by.
• These ticks are able to attach to their hosts by secreting a cement-like substance from their mouths and inserting it into the host.[4]

• The virus particle, like other Coltiviruses, is ~80 nm in diameter and is generally non-envolped.
• The double stranded RNA viral genome is ~20,000bp 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 that 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 off direct entry and replication of CTFV in mature erythrocytes.[5]

• The life cycle of Rickettsia rickettsii is considered to be a complex one.
• Survival is dependent on both an invertebrate vector, (the hard tick- Family Ixodidae) and a vertebrate host (including mice, dogs, rabbits).
• Humans are considered to be accidental vectors and are not essential in the rickettsial cycle.
• In addition, a sequence of events occur between both hosts in the successful transmission of rickettsial disease.
• (Rickettsia rickettsii mostly affects canines and humans.) ^[1]

• Genera of Colorado tick fever is wither an Orbivirus or Coltivirus.
• Four serotypes are responsible for human infections.^[2]

• Viral pathway involves targeting the cells in bone marrow or young child’s central nervous system.
• Inhibits the proper development of blood cells.
• A host defense mechanism, humoral immunity, is elicited by infection.^[2]

• Infection with Colorado tick fever occurs as a result of being bitten by an infected Rocky Mountain wood tick (Dermacentor andersoni).
• Colorado tick fever is transmitted to a tick during a blood meal involving a rodent reservoir such as a squirrels, chipmunks, and mice.
• Infection perpetuates as a tick continues to feed on another host.
• Viral transmission from human to human is rare, however may occur during blood transfusion.

• Colorado tick fever is not a nationally notifiable disease.
• The name Rocky Mountain spotted fever is somewhat of a misnomer. Cases of Rocky Mountain spotted fever have been reported in every continent except Antarctica, and in every state in the U.S. except for Alaska, and Hawaii.
• 83 cases of Colorado tick fever have been reported between the years of 2002 and 2012.^[4]

Specifically reported in the following six states:

• Arizona
• Colorado
• Montana
• Oregon
• Utah
• Wyoming^[4]

• It is estimated that approximately 1200 or more new cases of RMSF will present on a yearly basis. ^[5]

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Colorado tick fever (CTF) must be differentiated from other diseases that cause fever,chills, headaches, body ache, and rash. When trying to differentiate CTF from other infections, it is important to recognize that the clinical manifestations of CTF greatly resemble those of other tick-borne illnesses, especially those caused by the Rickettsiae family. Examples of misdiagnoses, with the umbrella of tick-borne diseases include typhus-spotted fevers and Ehrlichiosis.

Examples of tick-borne diseases that may be misdiagnosed for Colorado tick fever may be found in the table below:

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Colorado tick fever remains a rare disease with only 83 cases reported between the years of 2002 and 2012. Incidence of the disease remain primarily confined to the Rocky Mountain States, with a few outliers throughout the United States. Incidence of Colorado tick fever appears to be independent of both demographic and age. ^[1]

• Colorado tick fever is not a nationally notifiable disease.
• 83 cases of Colorado tick fever have been reported between the years of 2002 and 2012.^[1]

Specifically reported in the following six states:

• Arizona
• Colorado
• Montana
• Oregon
• Utah
• Wyoming^[1]

• There is no notifiable correlation between incidence rate and age.

• There is no notifiable correlation between incidence rate and demographics.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

The primary risk factors associated with Colorado tick fever are exposure to endemic environment and the time of that exposure. Rocky Mountain wood ticks have been identified as the primary vector of Colorado tick fever infections, thus being bitten in an endemic area may result in the contraction of the disease.

• Individuals with frequent exposure to dogs and who reside near wooded areas or areas with high grass may also be at increased risk of infection.

• Individuals living in areas inhabited by Rocky Mountain wood ticks.
• Highest incidence reported in Arizona, Colorado, Montana, Oregon, Utah, and Wyoming. Exposure to these areas will increase an individual’s risk of infection.
• Although the disease is randomly dispersed throughout regions of the United States. ^[1]

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

First signs of symptoms can occur about 3-6 days after the initial tick bite, although it can have incubation periods of up to 20 days. Patients usually experience a two-staged fever and illness which can continue for three days, diminish, and then return for another episode of 1-3 days. The virus has the ability to live in the blood stream for up to 120 days; therefore coming in contact without proper precautions and the donation of blood are prohibited.

Initial symptoms include: fever, chills, headaches,pain behind the eyes, light sensitivity, muscle pain, generalized malaise abdominal pain, nausea, vomiting as well as a flat or pimply rash. ^[1] During the second phase of the virus a high fever can return with an increase in symptoms. Colorado tick fever can be very severe in cases involving children and have even required hospitalization. Complications with this disease have included aseptic meningitis, encephalitis, and hemorrhagic fever but these are rare.

• Usual incubation period of 3-6 days, however the incubation period may occur for up to 20 days.
• Fever for three days.
• Chills
• Headache
• Sensitivity to the light
• Muscular pain
• Malaise
• Nausea
• Maculopapular rash

• Rash
• Two stage fever. Once the first fever resides after 3 days, a second fever will onset for one to three more days.

• Coloardo tick fever should resolve itself.

Complications are rarely associated with Colorado tick fever. However complications that may be associated with this disease include:

• Aseptic meningitis
• Encephalitis
• Hemorrhagic fever

• The prognosis is usually good in individuals with fully developed and normally functioning immune systems.
• Colorado tick fever may manifest into a severe illness within young populations, especially young children.