Typhus, Tick

Key Features

• Denotes a variety of spotted rickettsial fevers, often named by their

  • Geographic location (eg, Mediterranean spotted fever, Queensland tick typhus, Oriental spotted fever, African tick bite fever, Siberian tick typhus, North Asian tick typhus)

  • Morphology (eg, boutonneuse fever)

• Illnesses are caused by various rickettsial organisms (eg, R africae, R australis, R conorii, R japonica, R massiliae, R parkeri, R sibirica, and R 364D)

• Dogs and wild animals, usually rodents and even reptiles, may serve as reservoirs

• Travel is a risk factor for disease, particularly among elderly ecotourists

Clinical Findings

• Fever, headache, myalgias, and rash

• Pathogens usually produce an eschar or black spot (tâche noire); rarely, however, a "spotless" form occurs, termed "spotless boutonneuse fever"

• Painful lymphadenopathy or lymphangitis may also occur

• Rarely, papulovesicular lesions may resemble rickettsialpox

• Endothelial injury produces perivascular edema and dermal necrosis

• Regional adenopathy, disseminated lesions, kidney disease, splenic rupture, and focal hepatic necrosis are observed

• Rare manifestations include

  • Encephalitis

  • Internuclear ophthalmoplegia

  • Vertebral arteritis with glossopharyngeal nerve-associated dysphagia

  • Coronary involvement

  • Purpura fulminans

  • Hemophagocytic lymphohistiocytosis syndrome

Diagnosis

• Clinical

• Serologic tests or polymerase chain reaction (PCR) used for confirmation

Treatment

• Start therapy upon clinical suspicion since delayed therapy is the usual cause of increased morbidity

• Oral treatment with doxycycline (100 mg/day twice daily) or chloramphenicol (50–75 mg/kg/day in four divided doses) for 7–10 days is indicated

• Caution is advised with use of ciprofloxacin because it

  • Is associated with a poor outcome

  • Increases the severity of Mediterranean spotted fever

• The combination of erythromycin and rifampin is effective and safe in pregnancy

• Severe cases may require ICU care for multiorgan failure (particularly respiratory failure) since fatalities have been reported (more often than with scrub typhus)

• Prevention entails protective clothing, repellents, and inspection for and removal of ticks