infections
Overview of Rickettsial Infections
Diagnosis of Rickettsial Infections
A doctor's evaluation Blood tests and biopsy of the rash Because rickettsiae and rickettsia-like bacteria are transmitted by ticks, mites, fleas, and lice, doctors ask people Whether they have been bitten by a tick or another vector Whether they have traveled to an area where these infections are common Being bitten is a helpful clue—particularly in geographic areas where rickettsial or a related infection is common. However, many people do not recall such a bite. If doctors suspect Q fever, they may also ask whether people were at or near a farm (because cattle, sheep, and goats are the host for the bacteria that cause this infection). Symptoms also help doctors diagnose these infections. Doctors ask people How long it took for the rash to appear after they were bitten (if known) Whether they have other symptoms A physical examination is done to determine which parts of the body are affected and what the rash looks like. Doctors also look for an eschar (a sore covered by a black scab) that people may not have noticed and for swollen lymph nodes. Testing is usually needed to confirm the diagnosis. Often, doctors cannot confirm an infection with rickettsiae or rickettsia-like bacteria quickly because these bacteria cannot be identified using commonly available laboratory tests. Special blood tests for these bacteria are not routinely available and take so long to process that people usually need to be treated before test results are available. Doctors base their decision to treat on the person's symptoms and the likelihood of possible exposure. Useful tests include Blood tests that detect antibodies to rickettsiae or rickettsia-like bacteria If people have a rash, removal of a small sample of affected skin for testing (biopsy) Doctors use two techniques to make the bacteria easier to detect and identify: In immunofluorescence assays, foreign substances produced by the bacteria (antigens) are labeled with a fluorescent dye. The polymerase chain reaction (PCR) technique is used to increase the amount of the bacteria's DNA, so that the bacteria can be detected more rapidly. 