Background
Microbiology
- Disease caused by Rickettsia akari, an intracellular Gram-negative bacterium
- Unlike most rickettsiae, it has a plasmid
Epidemiology
- Transmitted by the house mouse mite (Liponyssoides sanguineus)
- Rodents are the reservoir
- Most cases are in New York, but it is found worldwide
- Most likely rickettsiosis to be found in Ontario
- Homelessness and IV drug use are risk factors
Clinical Manifestations
- Incubation period of 7 to 14 days
- Present with fever, vesicular rash, and eschar
- The eschar is painless, and appears as a papule about a week after innoculation, followed by vesicle that dries and leaves a brown or black eschar
- The rash is vesicular, but may be papulovesicular or any other type of rash
- Lesions leaves black crust and heal without scarring
- Spares palms and soles
- Resolves in two to three weeks
- May find leukocytosis
Diagnosis
- Detection of a four-fold rise in convalescent titres by complement fixation or indirect fluorescent antibodies
Management
- Usually self-limited, resolving in 7 to 10 days, though antibiotics help
- Doxycycline 100 mg po bid for 2 to 5 days and 48 h after fever resolves
