Rickettsialpox is a mild, self-limiting disease caused by the bacterial organism Rickettsia akari . It is transmitted by the bite of an infected mouse mite ( Liponyssoides sanguineus ). Primarily an urban disease, it was first discovered in New York City in 1946. Since then a small number of cases are reported in NYC each year. In 2007, there were 14 cases reported among New York City residents (rate of 1.7 cases per 1,000,000 persons).
|Rickettsialpox infections in New York City by Borough, 2000-2007|
* Case reports increased in the fall of 2001 and continued in 2002, following the anthrax attacks in New York City, New Jersey, Washington, D.C. , and Florida. An early sign of this disease is an eschar, a black crusty scab on the skin, which looks very similar to the skin form of anthrax (cutaneous anthrax). This prompted medical providers to test more people and report more cases of rickettsialpox, especially during the months after the anthrax attacks.
Anyone bitten by infected mites can get rickettsialpox. Patients often report exposure to rodents in the home or workplace. Most people who get infected experience only very mild illness or no illness at all.
Rickettsialpox is spread by the bite of an infected mouse mite ( Liponyssoides sanguineus ). Unlike ticks, mites do not attach and feed for long periods of time, so most people do not notice the mite or recall being bitten by an insect. Mites become infected by feeding on infected mice, but infected adult mites can also pass the infection to their eggs.
Rickettsialpox occurs in urban areas, usually where rodent infestation is common. House mouse mites only tend to feed on people where rodent infestation is severe, or when rodent control is taking place (because the mites leave their dying mouse hosts and feed on people). There is no apparent seasonality to rickettsialpox infection, as cases are reported year round.
Initially, patients infected with R. akari develop an eschar (a painless, dry thickened scab with a black center) at the site of the mite bite. This is followed by fever, headache, and a rash which can look like chickenpox. Symptoms can last for several days to a week.
The incubation period for rickettsialpox can be days to weeks.
It is likely that infection confers long-term immunity.
Diagnosis is based on symptoms and either a positive antibody test or a biopsy of the affected skin.
Antibiotics such as tetracycline or doxycycline have been effective in treating this disease, but a lot of people get better without antibiotics.
he key to prevention is rodent control. To reduce rodent infestation, remove and secure trash around the home and workplace. Extermination may be necessary if infestation is severe. Mite control may also be necessary during rodent extermination in areas where rickettsialpox is known to occur.