Reemergence of murine typhus in Galveston, Texas, USA, 2013.
Physicians who were aware of the study alerted our team of investigators to patients [greater than or equal to] 18 years of age who had reported fever during February-December 2013. Alternative syndromes that warranted exclusion included skin and soft tissue infections, urinary tract infections, cavitary or lobar pneumonia, and pyogenic intraabdominal processes (e.g., abscesses, appendicitis, cholecystitis, and diverticulitis). We obtained informed consent, medical history, and physical examination to record symptoms, signs, and laboratory data from each patient. We collected blood for use in real-time PCR, shell vial culture, and immunofluorescence assay (IFA) for the diagnosis of murine typhus (4-6). The conjugate used in IFA assays was Alexa Fluor 488 goat anti-human IgG ([gamma]-chain-specific) at a dilution of 1:400 (Jackson ImmunoResearch Laboratories, West Grove, PA, USA). We made extensive attempts to collect blood from enrollees for convalescent IFA testing. Further PCR analysis to amplify portions of the 17-kDa antigen, citrate synthase, and outer membrane protein B (ompB) genes were performed on DNA from a cell culture isolate (7-9). Amplicons were cloned and sequenced (4).
A confirmed case of murine typhus was defined as having compatible signs and symptoms and seroconversion (diagnostic cutoff of 1:64) or a 4-fold increase in IgG titer against R. typhi from acute- and convalescent-phase serum samples; PCR detection of rickettsial DNA within acute-phase blood; or isolation of R. typhi from blood. A probable case was defined as having a single IgG titer of [greater than or equal to] 1:256 during acute illness.
In addition to identifying acutely ill patients, we sought to determine the local prevalence of those who had R. typhi reactive antibodies. We repurposed serum samples collected from 500 Galveston residents; the samples were scheduled to be discarded after being used for routine clinical testing from outpatient clinics during the summer and fall of 2013. We screened for the presence of R. typhi IgG at a titer of 1:128 by IFA as described above. Endpoint titers were established in reactive samples. We performed IFA against spotted fever antigens (R. rickettsii) and Western blot analysis using R. typhi and R. rickettsii antigens to confirm the specificity of samples reactive to R. typhi as previously described (6,10). The University of Texas Medical Branch institutional review board approved these studies.
Eighteen patients who met study criteria were enrolled. Of these, 10 were determined to have murine typhus (7 confirmed and 3 probable) (Table 1). In addition to those identified prospectively, 2 probable cases were identified retrospectively. Serologic testing was the primary diagnostic method (6 of 7 confirmed cases). One case was confirmed by isolation of R. typhi from blood. This patient was an alcoholic man, 48 years of age, who sought care 4 days after the onset of fever, chills, and myalgias. Sequences of portions of the citrate synthase (GenBank accession no. KJ648945) and ompB (accession no. KJ648946) genes of this isolate revealed 100% homology to R. typhi Wilmington strain, and the sequence of the 17-kDa antigen gene (accession no. KJ648944) revealed 1 base pair difference. Real-time PCR screening of DNA extracted from whole blood demonstrated the presence of rickettsial DNA in the patient from whom the R. typhi isolate was obtained.
In addition to fever, the 12 patients, all reported headache, 7 (58%) had chills, 6 (50%) reported myalgias, 6 (50%) had rashes, and 9 (75%) had elevated hepatic transaminases (75%). Seven (58%) were hospitalized, and 2 (17%) were admitted to the intensive care unit. Except for 1 of the retrospectively identified cases, all patients were treated empirically for murine typhus (Table 1). Eleven (92%) were treated with either doxycycline or minocycline; minocycline was prescribed for some because of a national shortage of oral doxycycline. All patients had subsequent resolution of illness with no obvious difference in recovery between the 2 drugs. One patient (identified retrospectively) was treated with levofloxacin and reported slow resolution of her symptoms.
The 500 serum samples screened by IFA represent [approximately equal to] 1% of Galveston's population (48,733 by the 2013 census [http://quickfacts.census.gov/qfd/states/48/4828068. html; cited 2014 Dec 27]). The mean age of patients whose samples were tested was 61.5 years. IFA and Western blot testing showed 8 (1.6%) samples to be reactive, which supported typhus group specificity (Table 2). Of those seroreactive, the mean age was 60.9 years, and 5 (62.5%) were women. The geometric mean reciprocal titer was 181.
Galveston is a small city on a barrier island off the upper Texas coast, along the Gulf of Mexico. As with other port cities where rat population numbers are high, the incidence of murine typhus in this city was historically high.
However, in 1946, as part of an ectoparasite eradication program, the insecticide DDT was applied to common rat paths; subsequently, the number of ectoparasites spread by rats in human habitats was reduced. As a result, the incidence of murine typhus in Galveston decreased dramatically (2) and continued to decline through subsequent decades (11). This study describes what is probably the reemergence of murine typhus in this area.
The patients in this study exhibited typical signs and symptoms consistent with murine typhus (12). Although we cannot exclude the possibility of a different fleaborne rickettsia (i.e., R. felis) infecting some patients, the single rickettsial isolate identified supports R. typhi as a causative agent. The seroprevalence supports the occurrence of additional undiagnosed cases. Based solely on the titers of these reactive serum samples, it is not possible to elucidate recent versus distant infections. Sporadic cases may have gone undiagnosed.
Dynamic shifts in the epidemiology and transmission of murine typhus are not unprecedented. Although the ratto-rat cycle of transmission by fleas is often referred to as an urban cycle, the rural South experienced high rates of murine typhus in the 1940s as a result of a proliferation of rats after a change in crop production from cotton to peanuts, because rats were attracted to the peanuts as a source of food (13). In southern California, opossums infested with R. typhi- and R. felis-infected cat fleas (C. felis) have been associated with a shift of fleaborne rickettsioses from the urban center of Los Angles to suburban areas (14). This suburban cycle of transmission involving C. felis plays a recognized role in Corpus Christi, Texas, a coastal city [approximately equal to] 220 miles southwest of Galveston (1). Additionally, this cycle has been suspected in a recent outbreak of murine typhus in the central Texas city of Austin (15).
The recent recognition of murine typhus in Galveston may reflect the reemergence of R. typhi in rats; it may also reflect a cycle involving opossums and cats. Additionally, R. felis may play a role as a serologically cross-reacting culprit of illness. Further study is required to better understand the ecology and epidemiology of murine typhus as it reemerges in Galveston. Physicians and public health officials should be aware of this reemerging threat. Furthermore, vector control is of utmost importance.
We thank the faculty and staff of the University of Texas Medical Branch who helped identify patients with murine typhus. We also thank Anthony Okorodudu and Tho Nguyen for their help in the clinical laboratory.
This work was supported by the Carmage and Martha Walls Distinguished University Chair in Tropical Diseases Endowment.
Dr. Blanton is an infectious disease physician at the University of Texas Medical Branch. His research interests are in the study of rickettsial diseases.
(1.) Azad AF, Radulovic S, Higgins JA, Noden BH, Troyer JM. Fleaborne rickettsioses: ecologic considerations. Emerg Infect Dis. 1997; 3:319-27. http://dx.doi.org/10.3201/eid0303.970308
(2.) Strandtmann RW, Eben DJ. A survey of typhus in rats and rat ectoparasites in Galveston, Texas. Tex Rep Biol Med. 1953; 11:144-51.
(3.) Basra G, Berman MA, Blanton LS. Murine typhus: an important consideration for the nonspecific febrile illness. Case Rep Med. 2012; 2012:134601 [cited 2014 Dec 12]. http://www.pubfacts.com/ detail/23326268/Murine-typhus:-an-important-consideration-for the-nonspecific-febrile-illness
(4.) Blanton LS, Walker DH, Bouyer DH. Rickettsiae and ehrlichiae within a city park: is the urban dweller at risk? Vector Borne Zoonotic Dis. 2014; 14:168-70. http://dx.doi.org/10.1089/ vbz.2013.1473
(5.) Marrero M, Raoult D. Centrifugation-shell vial technique for rapid detection of Mediterranean spotted fever rickettsia in blood culture. Am J Trop Med Hyg. 1989; 40:197-9.
(6.) Philip RN, Casper EA, Ormsbee RA, Peacock MG, Burgdorfer W. Microimmunofluorescence test for the serological study of Rocky Mountain spotted fever and typhus. J Clin Microbiol. 1976; 3:51-61.
(7.) Webb L, Carl M, Malloy DC, Dasch GA, Azad AF. Detection of murine typhus infection in fleas by using the polymerase chain reaction. J Clin Microbiol. 1990; 28:530-4.
(8.) Regnery RL, Spruill CL, Plikaytis BD. Genotypic identification of rickettsiae and estimation of intraspecies sequence divergence for portions of two rickettsial genes. J Bacteriol. 1991; 173:1576-89.
(9.) Roux V, Raoult D. Phylogenetic analysis of members of the genus Rickettsia using the gene encoding the outer-membrane protein rOmpB (ompB). Int J Syst Evol Microbiol. 2000; 50:1449-55. http://dx.doi.org/10.1099/00207713-50-4-1449
(10.) Vishwanath S. Antigenic relationships among the rickettsiae of the spotted fever and typhus groups. FEMS Microbiol Lett. 1991; 81:341-4. http://dx.doi.org/10.1111/j.1574-6968.1991. tb04783.x
(11.) Older JJ. The epidemiology of murine typhus in Texas, 1969. JAMA. 1970; 214:2011-7. http://dx.doi.org/10.1001/ jama.1970.03180110021004
(12.) Dumler JS, Taylor JP, Walker DH. Clinical and laboratory features of murine typhus in south Texas, 1980 through 1987. JAMA. 1991; 266:1365-70. http://dx.doi.org/10.1001/ jama.1991.03470100057033
(13.) Hill EL, Ingraham SC II. A study of murine typhus fever in Coffee County, Alabama. Public Health Rep. 1947; 62:875-81. http:// dx.doi.org/10.2307/4586165
(14.) Eremeeva ME, Karpathy SE, Krueger L, Hayes EK, Williams AM, Zaldivar Y, et al. Two pathogens and one disease: detection and identification of flea-borne rickettsiae in areas endemic for murine typhus in California. J Med Entomol. 2012; 49:1485-94. http://dx.doi.org/10.1603/ME11291
(15.) Adjemian J, Parks S, McElroy K, Campbell J, Eremeeva ME, Nicholson WL, et al. Murine typhus in Austin, Texas, USA, 2008. Emerg Infect Dis. 2010; 16:412-7. http://dx.doi.org/10.3201/ eid1603.091028
Lucas S. Blanton, Rahat F. Vohra, Donald H. Bouyer, David H. Walker
Author affiliation: University of Texas Medical Branch, Galveston, Texas, USA
Address for correspondence: Lucas S. Blanton, University of Texas Medical Branch, 301 University Blvd, Galveston, TX 77555-0435, USA; email: email@example.com
DOI: http://dx.doi.org/ 10.3201/eid2103.140716
Table 1. Summary of reciprocal antibody titers in 12 patients with murine typhus, Galveston, Texas, 2013 * Patient Illness Acute titer Convalescent no. duration (date titer (date ([dagger]) collected) collected) 1 12 d 256 (Apr 10) 1,024 (Apr 30) 4t 4 d NR (May 23) NA 6 4 d NR (Jun 16) 128 (Jul 2) 8 7 d NR (Jul 10) 512 (Aug 8) 9 10 d NR (Jul 16) 256 (Jul 30) 10 13 d NR (Jul 19) 256 (Jul 30) 17 6 d NR (Sep 27) 1,024 (Dec 13) 13 8 d 256 (Jul 29) NA 15 8 d 256 (Aug 9) NA 16 ([section]) 3 wk ([paragraph]) 256 (Jul 30) NA 19 3 wk 512 (Oct 30) NA 20 ([section]) 8 d 256 (Mar 26) NA Patient Diagnosis by no. case definition 1 Confirmed 4t Confirmed 6 Confirmed 8 Confirmed 9 Confirmed 10 Confirmed 17 Confirmed 13 Probable 15 Probable 16 ([section]) Probable 19 Probable 20 ([section]) Probable *NR, nonreactive at a titer of 1:64; NA, not available. ([dagger]) Duration of illness before workup and treatment. ([double dagger]) Confirmed by culture isolate. ([section]) Case identified retrospectively. ([paragraph]) Patient was treated with levofloxacin 2 weeks before murine typhus workup. Table 2. Analysis of serosurvey samples found reactive to Rickettsia typhi by IFA and Western blotting, Galveston, Texas, 2013 * Sample Reciprocal IFA titers R. typhi R. rickettsii 1 256 NR 2 128 NR 3 128 NR 4 128 NR 5 256 NR 6 128 NR 7 1024 128 8 128 NR Sample Western blot analysis R. typhi protein R. rickettsii protein lysate (OmpB) ([dagger]) lysate (OmpA([double dagger])) ([section]) 1 + -1 2 + - 3 + - 4 + - 5 + - 6 + - 7 + - 8 + - * Omp, outer membrane protein; NR, nonreactive at a titer of 1:128. ([dagger]) Reactivity to the panrickettsial 135-kDa OmpB. Reactivity to the spotted fever group 190-kDa OmpA. ([section]) All serum samples reacted with R. rickettsii OmpB as described for spotted fever and typhus group OmpB antigens (10). ([section]) Bands corresponding to reactivity to OmpB but not OmpA confirms typhus group specificity.
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|Author:||Blanton, Lucas S.; Vohra, Rahat F.; Bouyer, Donald H.; Walker, David H.|
|Publication:||Emerging Infectious Diseases|
|Date:||Mar 1, 2015|
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