Rickettsia species cause Rocky Mountain spotted fever, rickettsialpox, other spotted fevers, epidemic typhus, and murine typhus. Orientia (formerly Rickettsia) tsutsugamushi causes scrub typhus.
Other diagnostic options include molecular tests, such as PCR, in some centers and skin biopsy. In addition to suggestive or positive serologic tests, patients with rickettsial infections may also have thrombocytopenia, hyponatremia, and cerebrospinal fluid pleocytosis.
Tickborne spotted fever rickettsioses are the most frequently reported travel-associated rickettsial infections. Those who go on safari—especially those walking in the bush, game hunters, and ecotourists to southern Africa—are at risk for African tick-bite fever.
Ehrlichiosis, anaplasmosis, and spotted fever rickettsiosis are nationally notifiable diseases in the United States. Commercial laboratories offer rickettsial testing for rickettsioses, anaplasmosis, ehrlichiosis, and scrub typhus.
INFECTIOUS AGENTS. Rickettsial infections are caused by multiple bacteria from the order Rickettsiales and genera Rickettsia, Anaplasma, Ehrlichia, Neorickettsia, Neoehrlichia, and Orientia ( Table 4-19 ). Rickettsia spp. are classically divided into the spotted fever group (SFG) and the typhus group, although more recently these have been ...
Immediate empiric treatment with a tetracycline is recommended for all ages, most commonly doxycycline. Chloramphenicol may be an alternative in some cases, but its use is associated with increased risk of death, particularly from R. rickettsii infection, compared with use of a tetracycline. In some areas, tetracycline-resistant scrub typhus has been reported, and azithromycin may be an effective alternative. Limited clinical experience has shown that A. phagocytophilum and R. africae infections respond to treatment with rifampin, which may be an alternative drug for some pregnant or doxycycline-intolerant patients. Expert advice should be sought if alternative agents are being considered.
Rickettsia spp. are classically divided into the spotted fever group (SFG) and the typhus group, although more recently these have been classified into as many as 4 groups. Orientia spp. make up the scrub typhus group.
More than 1 million cases occur annually, often in farmers or other occupationally exposed people. Most travel-acquired cases of scrub typhus are reported after visits to rural areas in countries where O. tsutusgamushi is endemic, but urban cases have also been described.
Rocky Mountain spotted fever is characterized by fever, headache, nausea, and abdominal pain. A rash is commonly reported but eschars are not. Patients with murine or epidemic typhus usually present with a severe but nonspecific febrile illness, and approximately half present with a rash.
Scrub typhus can be transmitted by many species of trombiculid mites encountered in high grass and brush and is endemic to northern Japan, Southeast Asia, Indonesia, eastern Australia, China, several parts of south-central Russia, India, and Sri Lanka; rare cases have been reported from the United Arab Emirates and Chile.
Most cases acquired in the United States are reported from Hawaii, California, and Texas. Epidemic typhus caused by R. prowazekii infection is reported rarely among tourists but can occur in communities and in refugee or incarcerated populations where body lice are prevalent. Outbreaks often occur during the colder months.
Rickettsial infection. Rickettsial infections are caused by a variety of obligate intracellular bacteria in the genus Rickettsia and are grouped into one of four categories: the spotted fever group rickettsiae, typhus group rickettsiae, the ancestral group, and the transitional group 1). Rickettsia species cause Rocky Mountain spotted fever, ...
Rickettsia are obligate intracellular Gram-negative coccobacillary bacteria that multiply within eukaryotic cells in ticks, lice, fleas, mites, chiggers, and mammals 5). Rickettsiae do not stain well with Gram stain, but they take on a characteristic red color when stained by the Giemsa or Gimenez stain.
Rickettsia is typically vector-borne, transmitted by ticks, body lice , and fleas. In most cases, humans are thought to be accidental hosts 9). The transmitting ticks vary depending on the region and organism, with Dermacentor variabilis (American dog tick), Dermacentor andersoni (Rocky Mountain wood tick), and Amblyomma americanum (Lone Star tick) associated with most cases of Rocky Mountain Spotted Fever in the United States. Alternatively, Amblyomma cajennense has been associated with spotted fever in South America and Amblyomma hebraeum or Amblyomma variegatum in South Africa. Because of the association with ticks and other vectors, infections with Rickettsiae are more common during warmer months and in people exposed to the outdoor and outdoor activities. Epidemic typhus, Rickettsia prowazekii, is transmitted by body lice and associated with crowded conditions and poor hygiene. Murine typhus (Rickettsia typhi) is most commonly reported in tropical and subtropical areas and is associated with flea bites 10).
Rickettsial infection symptoms. Patients typically present with symptoms four to ten days after exposure to the Rickettsia via a flea or tick bite. Symptoms classically include the triad of fever, headache, and a petechial or maculopapular rash.
Other diagnostic options include molecular tests, such as PCR, in some centers and skin biopsy. In addition to suggestive or positive serologic tests, patients with rickettsial infections may also have thrombocytopenia, hyponatremia, and cerebrospinal fluid pleocytosis.
Epidemic typhus, Rickettsia prowazekii, is transmitted by body lice and associated with crowded conditions and poor hygiene. Murine typhus (Rickettsia typhi) is most commonly reported in tropical and subtropical areas and is associated with flea bites 10).
Ticks may be carried into the house on clothing. Any ticks that are found should be removed. Tumble dry clothes in a dryer on high heat for 10 minutes to kill ticks on dry clothing after you come indoors. If the clothes are damp, additional time may be needed. If the clothes require washing first, hot water is recommended. Cold and medium temperature water will not kill ticks.