Colorado tick fever

Abstract

able 15-1. Clinical Manifestations of Colorado Tick Fever Time after exposure Clinical manifestations Laboratory analyses Other notes 3-6 days 8-16 days Acute onset of malaise, myalgia, high fever, chills, intense headache, painful skull, photophobia, retroorbital pain, and lumbar back pain. Nausea and vomiting may occur. This phase lasts for 5-10 days Convalescent phase begins, with asthenia, weakness, and malaise resolving within a few weeks. Some patients may experience prolonged convalescence for months Demonstration of viral antigens in erythrocytes by immunofluorescence Viral isolation from erythrocytes Serology (less useful) A biphasic pattern occurs in half of patients, with initial febrile illness for 2-3 days, followed by an asymptomatic afebrile period for 1-2 days, then a second symptomatic febrile period lasting for 2 more days CLINICAL MANIFESTATIONS The clinical manifestations of CTF are described in Table 15-1. Neither respiratory nor gastrointestinal symptoms are prominent with this infection. Associated skin rash with CTF is not a prominent, common, or characteristic feature. In two large clinical series, the incidence of skin eruption ranged from 5 to 12% [12,13]. The associated exanthem is often transient and faint, and it may be limited to the trunk or become generalized [12-15]. Macular, maculo- Table 15-2. Differential Diagnoses for Colorado Tick Fever Rocky Mountain spotted fever: Fever, headache, and rash are typical manifestations of RMSF. It is seen predominately in children in the eastern United States, but a similar illness occurs in Brazil. A tick bite history is inconstant. Fever occurs 2-8 days later. The rash, a vasculitis due to endothelial cell involvement, blanches initially, then turns purpuric, perhaps hemorrhagic or even necrotic. It appears on the wrists and ankles frequently involving the palms and soles, then spreads centrally. Absence of the rash occurs in proven disease. The headache may be associated with meningeal signs, and altered mental status or coma may occur. Cardiac involvement results in failure and arrhythmias. Myositis and pneumonia are seen and edema may occur. Thrombocytopenia is common as is leukocytopenia, but leukocytosis occurs with secondary infectious complications. Treatment with chloramphenicol or tetracycline must be based on suspicion of diagnosis; untreated disease may be fatal Lyme disease: A tick bite precedes the classic erythema migrans eruption early in the course of disease. Late manifestations are arthritis, aseptic meningitis, cranial nerve palsy, or heart block Tularemia: Tularemia may be associated with a tick bite, but the site of inoculation becomes painful and ulcerated, with associated lymphadenopathy. The less common presentation with bacteremia or meningitis is similar to CTF but may be more severe Enteroviral infections: Patients have fever, headache and nuchal rigidity. Cerebrospinal fluid studies show lymphocytic predominance with elevated protein. Enteroviral meningoencephalitis will be clinically indistinguishable from other central nervous system diseases. Serology, viral isolation, or where available, nucleic acid amplification testing will prove the etiology Herpes simplex virus (HSV) encephalitis: HSV encephalitis should be excluded because of its severe outcome and response to antiviral therapy. Rapid testing for HSV is commonly employed. A hemorrhagic, necrotizing encephalitis of the temporal lobes is typical, but it may appear as meningitis or frank encephalitis with seizures and coma Other Arboviral Infections: ONN is suggested by sub-Sarahan travel, fever, arthritis, a morbilliform rash, and lymphadenopathy. Sindbis is suggested by fever, rash, arthritis with travel in Europe, Asia, Africa, or Australia, and mosquito exposure Mayaro is suggested by fever, chills, headache, myalgia, arthralgia, and a maculopapular rash as the fever fades and travel to Brazil or Trinidad, with mosquito exposure. Travel to Australia, mosquito exposure, fever, arthritis, and rash suggests Ross River virus or Barmah Forest disease Oropouche is suggested by travel to Trinidad or northern South America, fever, myalgia, anorexia, headache, photophobia, leukopenia, with exposure to Culicoides midges or suggestive season and habitat Sandfly fever is suggested by travel to Africa, southern Europe, central Asia or the Americas in the summer, exposure to small flies, or habitat with fever, myalgia, photophobia, retro-orbital pain, and conjunctival injection Other Arboviral Encephalitis: Eastern equine encephalitis is suggested by encephalopa- thy (altered mental status, coma, seizures), by salt marsh habitat in North and South America, deaths in horses and pheasants, and mosquito exposure in hot, damp months Western equine encephalitis is suggested by encephalopathy with mosquito exposure in western United States and Canada and an equine epizootic Venezuelan equine encephalitis is suggested by encephalopathy with travel in South and Central America, the Florida Everglades, Mexico or Texas, inflammation of conjunctivae or pharynx, flushed facies and muscular tenderness, an equine epizootic, and exposure to mosquitoes in wet, warm months West Nile fever is suggested by travel to rural Africa, southern Europe, central or south Africa, or northeastern United States, mosquito exposure, symptoms of headache, myalgia, lymphadenopathy, leukopenia, and a nonpruritic maculopapular rash California encephalitis is suggested by encephalopathy with rural midwest United States travel in July through September Japanese encephalitis is suggested by severe encephalopathy in children in Asia in the monsoon season St. Louis encephalitis is suggested by encephalopathy with central and western United States travel, mosquito exposure in late summer to early autumn Tick-borne encephalitis is suspected by tick exposure in Russia or central Europe in late spring or summer after heavy rainfall or exposure to raw milk in a patient with altered mental status, fever, thrombocytopenia, and leukopenia Powassan encephalitis occurs in Russia, Canada, and the United States. Young boys are more commonly affected, and tick exposure is frequent papular, morbilliform, and petechial eruptions have been described [12].