Murine Typhus, Texas, USA | CDC EID

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Volume 16, Number 3–March 2010
Research
Murine Typhus in Austin, Texas, USA, 2008
Jennifer Adjemian,1,2 Sharyn Parks,1 Kristina McElroy, Jill Campbell, Marina E. Eremeeva, William L. Nicholson, Jennifer McQuiston, and Jeffery Taylor
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (J. Adjemian, S. Parks, K. McElroy, M.E. Eremeeva, W.L. Nicholson, J. McQuiston); Texas Department of State Health Services, Austin, Texas, USA (S. Parks, J. Taylor); and Austin/Travis County Health Department, Austin (J. Campbell)

Suggested citation for this article

Abstract
In August 2008, Texas authorities and the Centers for Disease Control and Prevention investigated reports of increased numbers of febrile rash illnesses in Austin to confirm the causative agent as Rickettsia typhi, to assess the outbreak magnitude and illness severity, and to identify potential animal reservoirs and peridomestic factors that may have contributed to disease emergence. Thirty-three human cases of confirmed murine typhus were identified. Illness onset was reported from March to October. No patients died, but 23 (70%) were hospitalized. The case-patients clustered geographically in central Austin; 12 (36%) resided in a single ZIP code area. Specimens from wildlife and domestic animals near case-patient homes were assessed; 18% of cats, 44% of dogs, and 71% of opossums had antibodies reactive to R. typhi. No evidence of R. typhi was detected in the whole blood, tissue, or arthropod specimens tested. These findings suggest that an R. typhi cycle involving opossums and domestic animals may be present in Austin.

Murine typhus, also known as endemic or flea-borne typhus, is caused by Rickettsia typhi, a gram-negative, obligate intracellular bacillus. This zoonotic disease is primarily maintained in rodent–flea cycles and is transmitted to humans when infected flea feces contaminate the flea feeding site or other skin abrasions (1). After an incubation period of 6–14 days, a nonspecific febrile illness may develop with symptoms of headache, arthralgia, abdominal pain, and confusion. Approximately 50% of patients also report the development of a diffuse macular or maculopapular rash, which starts on the trunk and spreads peripherally (sparing the palms and soles) nearly 1 week after the initial onset of fever and can last from 1 to 4 days. Although the disease is easily treated with doxycycline, it can be severe or even fatal if not diagnosed and treated properly (2,3).

Throughout its global distribution, R. typhi has been primarily concentrated in coastal urban areas where it is maintained among rats (Rattus spp.) and oriental rat fleas (Xenopsylla cheopis) (3). Within the United States, murine typhus is endemic in parts of California, Hawaii, and Texas, where <100 cases are reported annually (4–7) with a 1%–4% fatality rate when left untreated (3,4). Recent studies in southern Texas and California indicate that the classic rodent-flea cycle of R. typhi has been augmented in these suburban areas by a peridomestic cycle involving free-ranging cats, dogs, opossums, and their fleas (1,6,7). In addition, R. felis, which may produce a febrile illness in humans (8), may also circulate within these same zoonotic cycles (7,9). Although both agents have been documented in opossum-flea cycles in parts of southern Texas (7,9), these diseases are rare in the Austin/Travis County area. Though Austin is only 140 km from the Texas coast, where murine typhus is endemic, only 4 cases have been reported there in the past 25 years; 2 of those 4 cases were reported in September 2007 (Texas Department of State Health Services [TDSHS], unpub. data).

From March through July 2008, the Austin/Travis County Department of Health and Human Services (ATCDHHS) identified 13 cases of febrile illness, half of which had a rash or a severe headache, or both. Laboratory tests conducted at the TDSHS and the Centers for Disease Control and Prevention (CDC) indicated that these patients all had antibodies reactive to R. typhi. Active infection with R. typhi was also identified in 1 patient by PCR. In August 2008, TDSHS, CDC, and ATCDHHS initiated a detailed epidemiologic investigation to confirm the causative agent as R. typhi, to assess the outbreak magnitude and illness severity, and to identify potential animal reservoirs and peridomestic factors that may have contributed to disease emergence.

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Suggested Citation for this Article
Adjemian J, Parks S, McElroy K, Campbell J, Eremeeva ME, Nicholson WL, et al. Murine typhus in Austin, Texas, USA. Emerg Infect Dis [serial on the Internet]. 2010 Mar [date cited]. Available from http://www.cdc.gov/EID/content/16/3/412.htm

DOI: 10.3201/eid1603.091028