LETTERS

Rickettsia felis 398-nt fragment of the rickettsial gltA for the other Ricketttsia species was gene and an 856-nt fragment of the considered homologous to the fi rst in Chile rickettsial ompB gene (7,8). Rickettsia species or to a very closely To the Editor: Rickettsiosis due A total of 21 individual fl eas related genotype (7,9). In each slide, a to Rickettsia felis is an emerging dis- (70%) yielded expected PCR prod- nonreactive cat serum specimen (neg- ease that has been reported worldwide ucts for both gltA and ompB genes. ative control) and a known reactive (1). Fever, headache, myalgia, and PCR gltA products from the 21 fl eas cat serum specimen (positive control) macular rash have been attributed to and ompB products from 5 fl eas were were tested at the 1:64 dilution (7). R. felis infection in humans (1). In subjected to DNA sequencing as de- IFA detected antibodies reactive South America, R. felis infection in scribed (7). The gltA partial sequences with R. felis (titer >64) in 16 (72.7%) fl eas (mostly Ctenocephalides spp.) obtained from 21 fl eas were identical, of 22 cats. Among those, 5 (22.7%) has been reported only in Brazil, Peru, as were the ompB partial sequences also reacted with R. rhipicephali, 4 and Uruguay (2–3). Although a grow- from 5 fl eas. These sequences were (18.2%) with R. bellii, 3 (13.6%) with ing number of articles have reported 100% identical to corresponding se- R. parkeri, 2 (9.1%) with R. rickettsii, that R. felis is transmitted by fl eas, the quences in the R. felis genome (Gen- and 1 (4.5%) with R. amblyommii. No acquisition mechanism of R. felis by Bank accession no. CP000053). serum reacted with any other Rickett- vertebrates or uninfected fl eas in na- Blood serum samples were col- sia species without reacting with R. ture remains unknown (4). lected from the 22 cats and tested by felis (Table). Four cat serum speci- Cats experimentally exposed to R. indirect immunofl uorescence assay mens (cats 1, 3, 8, and 11) showed felis–infected fl eas have been shown (IFA) with crude antigens derived titers to R. felis at least 4-fold higher to become seropositive (5). How- from 6 Rickettsia isolates from Bra- than those to any of the other 5 an- ever, neither serologic nor molecular zil: R. bellii, R. amblyommii, R. rhipi- tigens. The antibody titers in these 4 evidence of R. felis infection has been cephali, R. rickettsii, R. parkeri, and animals were considered to have been reported in cats under natural condi- R. felis (7,9). Serum was considered to stimulated by R. felis infection. For tions, despite the fact that most C. felis contain antibodies against rickettsiae if the remaining 12 seropositive cats, fl eas are infected by R. felis (6,7). it displayed a reaction at 1:64 dilution. we could not discern whether R. felis In November 2006, we investi- End-point titers against each Rickett- had been the infection agent because gated the presence of rickettsial DNA sia species were determined by testing the results displayed a single titer of in 30 C. felis fl eas randomly collected serial 2-fold serum dilutions. Reactive 64 for R. felis or showed similar titers from 22 domestic cats privately owned serum specimens were tested in 2 or for other Rickettsia species. and housed indoors in a single house- 3 replications by 2 readers before the We report 70% R. felis–infected hold in Santiago, Chile. To detect rick- end-point titer was determined. Serum fl eas in this study on the basis of the ettsial DNA in each individual fl ea, showing a Rickettsia species titer at concordant results of 2 PCR ampli- PCRs were performed that targeted a least 4-fold higher than those observed fi cations (gltA and ompB) and DNA

Table. End-point titers of indirect immunofluorescence assay (IFA) for 6 Rickettsia species in cats from a household in Santiago, Chile* IFA titers for Rickettsia antigens Cat no. R. felis R. rhipicephali R. bellii R. parkeri R. rickettsii R. amblyommii PAIHR 1128–––––R. felis 2 256 256 128 – – – 3 512 128 64 – – – R. felis 564––––– 66464– – – – 764––––– 8 128–––––R. felis 964––––– 1064––––– 11 128 – – – – – R. felis 1264––––– 14 128 – 64 128 – 128 1564––––– 1964––––– 21 128 64 128 128 128 – 22 64 64 – 64 64 – *PAIHR, possible antigen involved in a homologous reaction (serum showing for a Rickettsia species titer at least 4-fold higher than that observed for any other Ricketttsia species was considered homologous to the first Rickettsia species); –, nonreactive at titer >64.

1794 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 13, No. 11, November 2007 LETTERS

sequencing. This infection rate is References Possible Typhoon- within the range (13.5%–90%) that 1. Parola P, Davoust B, Raoult D. Tick- and related Melioidosis has been reported for R. felis infect- fl ea-borne rickettsial emerging zoonoses. ing Ctenocephalides fl eas in Brazil Vet Res. 2005;36:469–92. Epidemic, Taiwan, and Uruguay (2,3,7). Sixteen (72.7%) 2. Horta MC, Pinter A, Cortez A, Soares 2005 cats contained R. felis–reactive anti- RM, Gennari SM, Schumaker TTS, et al. Rickettsia felis (Rickettsiales: Rick- bodies; 4 of them showed titers to R. ettsiaceae) in Ctenocephalides felis felis To the Editor: Melioidosis is a se- felis at least 4-fold higher than those to (Siphonaptera: Pulicidae) in the State of vere infection caused by Burkholderia the other 5 rickettsial strains, fi ndings São Paulo, Brazil. Arq Bras Med Vet Zoot. pseudomallei. This organism is pres- that enabled us to technically conclude 2005;57:321–5. ent in tropical and subtropical regions 3. Venzal JM, Perez-Martinez L, Felix ML, that these cats were exposed to R. felis Portillo A, Blanco JR, Oteo JA. Prevalence where melioidosis is endemic. Before or a closely related organism (1,7,9). of Rickettsia felis in Ctenocephalides felis 1995, melioidosis was rare in Taiwan. Our fi nding of 70% R. felis infection and Ctenocephalides canis from Uruguay. In 2001, when the annual number of in fl eas infesting the cats indicates that Ann N Y Acad Sci. 2006;1078:305–8. cases of melioidosis in Taiwan was de- 4. Pornwiroon W, Pourciau SS, Foil LD, cats acquired the infection through in- Macaluso KR. Rickettsia felis from cat termined to be 1–3 per year from 1996 fected fl eas. However, the mechanism fl eas: isolation and culture in a tick-de- to 2000, the idea was fi rst proposed of R. felis transmission by fl eas is yet rived cell line. Appl Environ Microbiol. that the disease was endemic (1). to be demonstrated under experimen- 2006;72:5589–95. From July 21 through August 24, 5. Wedincamp J Jr, Foil LD. Infection and tal conditions. seroconversion of cats exposed to cat 2005, an unusually large number (54) To our knowledge, the presence of fl eas (Ctenocephalides felis Bouche) in- of melioidosis cases occurred in Tai- R. felis, or a spotted fever group Rick- fected with Rickettsia felis. J Vector Ecol. wan. This number exceeded the aver- ettsia species, has not been reported in 2000;25:123–6. age case number of 9.4 per year from 6. Hawley JR, Shaw SE, Lappin MR. Preva- Chile. Recent investigations have pro- lence of Rickettsia felis DNA in the blood 2001 to 2004. Since this outbreak ap- vided clinical and serologic evidence of cats and their fl eas in the United States. peared to be a common-source epi- of canine (10) and human (K. Abarca J Feline Med Surg. 2007;9:258–62. demic, all persons were suspected of and J. Lopez, unpub. data) infection 7. Horta MC. Epidemiological study of Rick- becoming infected from this source at ettsia felis in areas endemic and non-en- by spotted fever rickettsia in Chile, demic for Brazilian spotted fever in the the same time. confi rmed by IFA that used R. conorii state of São Paulo [in Portuguese]. São To determine this common commercial antigen. Since substantial Paulo: University of São Paulo (PhD the- source, we investigated the role of Ty- serologic cross-reaction occurs be- sis); 2006. phoon Haitang, which hit Taiwan on 8. Guedes E, Leite RC, Prata MCA, Pacheco tween R. conorii and R. felis antigens RC, Walker DH, Labruna MB. Detection July 18 and 19, 2005, and resulted in (1), R. felis could be causing infection of Rickettsia rickettsii in the tick Am- heavy rainfall. Because the date of this in dogs or humans in Chile. blyomma cajennense in a new Brazilian typhoon overlapped the incubation pe- spotted fever–endemic area in the state of riod (1–21 days in most cases) (2) and Minas Gerais. Mem Inst Oswaldo Cruz. rain is a factor in outbreaks of melioi- This research was fi nancially sup- 2005;100:841–5. dosis (3), Typhoon Haitaing may have ported by Clinica Veterinária Alcantara 9. Labruna MB, Horta MC, Aguiar DM, Cavalcante GT, Pinter A, Gennari SM, been the cause. (Chile), Fundação de Amparo à Pesquisa et al. Prevalence of Rickettsia infection All 57 clinical strains of B. pseu- do Estado de São Paulo (Brazil), and in dogs from the urban and rural areas of domallei isolated during this outbreak Conselho Nacional de Desenvolvimento Monte Negro Municipality, western Ama- were typed by pulsed-fi eld gel electro- Científi co e Tecnológico (Brazil). zon, Brazil. Vector Borne Zoonotic Dis. 2007;7:249–56. phoresis (PFGE) DNA macrorestric- 10. López J, Abarca K, Azocar T. Clinical and tion analysis (4). A higher incidence Marcelo B. Labruna,* serological evidence of canine rickettsio- sis in Chile [in Spanish]. Rev Chil Infect. rate (8.86% per million) and clonal Maria Ogrzewalska,* 2007;24:189–93. diversity (9 PFGE types) of B. pseu- Jonas Moraes-Filho,* domallei were observed in the sub- Paulina Lepe,† Address for correspondence: Marcelo B. tropical zone (south of 23.5°N) of Tai- Jose Luis Gallegos,† Labruna, Laboratório de Doenças Parasitárias, wan than in the temperate zone (north and Javier López† Departamento de Medicina Veterinária Preventiva e Saúde Animal, Faculdade de of 23.5°N) (0.18% per million and 2 *University of São Paulo, São Paulo, Bra- Medicina Veterinária e Zootecnia, Universidade PFGE types) (Table). Because clonal zil; and †Alcantara Veterinary Clinics, San- de São Paulo, Av Prof Dr. Orlando Marques diversity in outbreaks of melioidosis is tiago, Chile de Paiva 87, São Paulo, SP, Brazil 05508-270; characteristic of extreme weather (5), email: [email protected] these data support possible involve- ment of the typhoon in this outbreak.

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