Journal name: Research and Reports in Tropical Medicine Article Designation: REVIEW Year: 2018 Volume: 9 Research and Reports in Tropical Medicine Dovepress Running head verso: Bermúdez C and Troyo Running head recto: Rickettsia in Central America open access to scientific and medical research DOI: http://dx.doi.org/10.2147/RRTM.S160951 Open Access Full Text Article R E V I E W A review of the genus Rickettsia in Central America Sergio E Bermúdez C1 Abstract: In this paper, we present a historical review of rickettsiosis in Central America and Adriana Troyo2 also the most recent findings of Rickettsia in ectoparasites. All countries of Central America have 1 records of rickettsiosis. Regarding the typhus group rickettsioses, there is clinical or serological Department of Medical Entomology, Gorgas Memorial Institute for evidence of Rickettsia prowazekii in Guatemala, Rickettsia typhi in Panama, Guatemala, and Health Research, Panamá; 2Vector Costa Rica and unidentified species of the typhus group in El Salvador. Concerning spotted Research Laboratory, Tropical Diseases Research Center, Faculty fever group rickettsiosis, there is serological evidence of infection by Rickettsia akari in Costa of Microbiology, University of Costa Rica and confirmed cases involving Rickettsia rickettsii in Panama and Costa Rica. There are Rica, San Jose, Costa Rica also reports of spotted fever group rickettsiosis in acute patients from Guatemala, Honduras, and Nicaragua. Serological studies in Central America show reactivity of Rickettsia ambyommatis, Rickettsia bellii, Rickettsia felis, Rickettsia rhipicephali, and R. rickettsii in domestic and wild mammals. Eight species of Rickettsia have been detected in ectoparasites from Central America: R. africae (or very similar), R. amblyommatis, R. asembonensis, R. bellii, R. felis, R. parkeri, R. rhipicephali, and R. rickettsii, in addition to undescribed strains such as Atlantic Rainforest, Colombianensi, IbR/CRC, Barva, Aragaoi, and Candidatus “Rickettsia nicoyana;” the latter being the only one associated with Argasidae (Ornithodoros knoxjonesi). R. amblyommatis is the most common species in Central America, seeing as it has been reported in 10 species of ticks and one of fleas in five of the seven countries of the region. In this study, we demonstrate that the genus Rickettsia is widely distributed in Central America and that rickettsiosis could be an underestimated problem in the absence of greater diagnostic efforts in undetermined febrile cases. Keywords: rickettsiosis, Rickettsia, Rocky Mountain spotted fever, vector, Central America Introduction Rickettsia is a genus composed of 27 species of obligate intracellular bacteria, and ~17 of them are considered pathogens of animals and humans.1 Pathogenic species are divided into the typhus group (TG), transmitted by insects, and the spotted fever group (SFG), which is mainly transmitted by mites and hard ticks.1,2 Regarding the differences between the two groups, TG rickettsiae lack the capacity to polymerize actin and produce infections only in the cytoplasm of host cells, whereas SFG rickettsiae can polymerize actin and infect nuclei; in addition, there are differences in optimal growth Correspondence: Sergio E Bermúdez C temperatures (35°C for TG and 32°C for SFG), G-C content (29% in TG and 32%–33% Medical Entomology Department, Gorgas Memorial Institute for Health Research, in SFG), and outer membrane proteins (type B in TG and types A and B in SFG). 3 PO Box 0816-02593, Justo Arosemena y The TG includes two pathogens: Rickettsia prowazekii causes epidemic typhus Calle 35, Panamá, Panamá Tel +507 527 4000 and is transmitted mainly by contact with infected feces of the human body louse; Email sbermudez@gorgas.gob.pa Rickettsia typhi is responsible for endemic or murine typhus, and its transmission is submit your manuscript | www.dovepress.com Research and Reports in Tropical Medicine 2018:9 103–112 103 Dovepress © 2018 Bermúdez C and Troyo. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms. http://dx.doi.org/10.2147/RRTM.S160951 php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php). Bermúdez C and Troyo Dovepress associated with fleas.4,5 Both the rickettsiae seem to be cos- methods for detection of rickettsiae in arthropods have gener- mopolitan because of the wide geographical distribution of ated a large number of scientific literature around the world.11 their vectors.1 General symptoms of infection with TG rick- In Central America, although rickettsial diseases are ettsiae are non-specific: headache, fever (higher in epidemic known, the low number of cases per year and the higher typhus), muscle and joint pain; patients also present nausea prevalence of other infectious diseases have prevented greater and vomiting, cough, rash (moderate in murine typhus, but attention from professionals and institutions working in severe in epidemic typhus), chills, decrease in blood pres- human health. In the present study, we present a historical sure, stupor, photosensitivity, delirium, and death in untreated review and the most recent findings pertaining species of cases of epidemic typhus.6 In fact, mortality in untreated Rickettsia and rickettsioses in Central America. For this, we cases of epidemic typhus is usually high (10%–60%), but searched for scientific publications in English and Spanish decreases significantly if the adequate antibiotic treatment in databases and search engines such as PubMed, Scielo, is administered within the first days of infection.6 In addition LILACS, and Google Scholar, and by using keywords to these species, other pathogenic bacteria are recognized as (Rickettsia, rickettsiosis, country names). An initial selection etiological agents of “typhus,” although they belong to the was made when the title and abstract suggested reports of SFG (eg, Queensland ticks typhus, Rickettsia australis) or to rickettsiae or rickettsiosis in any country of Central America, another genus (eg, scrub typhus by Orientia tsutsugamushi). and complete documents were read when in doubt about the More than 25 species belong to the SFG, and they pres- content. Local libraries and retired rickettsiologists in Panama ent geographical distributions in accordance with the range and Costa Rica were contacted to locate and obtain publica- of their principal tick vectors, with the exception of the tions that were not readily available. All resulting articles cosmopolitan Rickettsia felis, associated mainly with fleas.7 were read in detail, as well as any additional publications Of these, currently 15 pathogenic species are reported world- that were cited in them but had not been identified previously. wide, in addition to several other species that are considered potential human pathogens, but for which clinical evidence Rickettsioses in Central America has not been conclusive.1 The severity of SFG rickettsial TG rickettsioses infections vary greatly between species, and similar to TG Both epidemic and endemic (murine) typhus have been docu- rickettsial infections, there are usually no specific symptoms mented in Central America (Table 1). Epidemic typhus is one that can be used to clearly differentiate SFG rickettsioses of the most ancient human diseases known, and outbreaks from several other fevers caused by viruses (eg, dengue) or have occurred along the history of humanity, with numer- bacteria (eg, Leptospira sp.). In general, and depending on ous deaths.4 Although epidemics of this disease decreased the Rickettsia species involved, patients may present mild or high fever, an eschar at the site of bacterial entry, inflamma- tion of regional or satellite lymph nodes, and exanthema or Table 1 Rickettsial infections in humans reported in Central erythematous maculopapular rash; also, damage to different America organs may be involved due to vasculitis and, in extremes Country Rickettsia spp. Humans References cases, death may occur.8 Rickettsia rickettsii is the most lethal Clinical No clinical agent within the genus and the most important tick-borne dis- Belize SFGR No Yes 43 ease in America, as it presents high fatality rates in untreated Costa Rica Rickettsia akari No Yes 18 cases.9,10 Infection by R. rickettsii causes the disease known Rickettsia rickettsii Yes No 18,34–37,39 SFGR Yes Yes 36,38 as Rocky Mountain spotted fever (RMSF) in the USA, but El Salvador TGR No Yes 18,19 it also has regional names like “fiebre maculosa Brasileira” Guatemala SFGR Yes Yes 18,40 (Brazil) or “fiebre de Tobia” (Colombia).10 Rickettsia typhi No Yes 18 In the last three decades, rickettsial diseases have awak- Rickettsia prowazekii Yes Yes 13 Honduras SFGR Yes Yes 18,41 ened the interest of specialists in public health due to the TGR No Yes 18 increase of reported cases and the possibility that they will Nicaragua SFGR Yes Yes 18,42 continue rising due to anthropogenic modifications and global Panamá SFGR Yes Yes 20 climate change, in addition to the threat that these bacteria R. rickettsii Yes No 20,24,26–32 R. typhi Yes Yes 17,18,20 represent as a potential bioterrorism weapon.4 Therefore, Abbreviations: SFGR, spotted fever group rickettsiosis; TGR, typhus group efforts to improve the diagnosis of rickettsioses and the rickettsiosis. 104 submit your manuscript | www.dovepress.com Research and Reports in Tropical Medicine 2018:9 Dovepress Dovepress Rickettsia in Central America considerably after the control of lice populations and the use 1950s.24 During the investigation of these cases, R. rickettsii of antibiotic treatment, cases still occur in poor villages in was isolated from the tick Amblyomma mixtum (cited as cold regions of North America, Eastern Europe, Asia, and Amblyomma cajennense), and Rhipicephalus sanguineus mountainous towns in Central and Eastern Africa, as well as s.l. was implicated as a potential vector in an urban case.25,26 South and Central America.6 According to Hume, epidemic After these cases, no more spotted fevers were reported in typhus may have entered Central America during the Euro- Panama for several decades; however, a serosurvey showed pean conquest.12 Since then, this disease has remained as a relatively high prevalence (5.4%–15.2%) of antibodies to isolated outbreaks in mountainous areas of Central America, SFG rickettsiae in 1,400 volunteers, but without determining in particular in villages and town of Guatemala with eleva- the possible Rickettsia species.27 tions between 2,500 and 3,500 m above sea level.13 A high Indeed, almost 60 years passed until new cases of RMSF mortality was reported in Guatemala during outbreaks in were confirmed in Panama: one case in 2004, three in 2007, 1932–1934, with ~180 fatal cases per year.13 one in 2008, one in 2012, one in 2015, and three in 2017 (only Regarding murine typhus, it is present worldwide but two of them were reported in the scientific literature).28–32 predominantly in areas of tropical and subtropical regions Nine of the patients died, with a 90% fatality. Recently, R. that have poor sanitation, where humans inhabit close rickettsii was detected in intradomiciliary R. sanguineus s.l. to rodents.14,15 Currently, murine typhus is present in the as part of an investigation of an urban case in the City of Mediterranean basin, some countries of Africa, Asia, and Panama. This may represent a new scenario as to the ecol- America.16 In Central America, the first mention of murine ogy of RMSF transmission, where dogs and their ticks may typhus was in the descriptions of clinical symptoms of cases play an important role in urban areas.32 In addition to these diagnosed in Panama.17 In this country, more than 50 cases confirmed cases, a serological study revealed a relatively were confirmed during 1932–1947, with the last outbreak high seroprevalence of SFG infections (29%–31%) in people (13 patients) in the City of Panama that affected mostly from rural areas.20,33 people working or visiting a storeroom where dead rats had In Costa Rica, SFG infections were reported for the first been reported.17 time in 1952 from serological studies.34,35 Regardless, no A serological survey in Central America showed anti- febrile cases were documented until 1974, when patients body titers against TG Rickettsia in humans in Guatemala, presented symptoms compatible with SFG rickettsiosis.36 In Honduras, El Salvador, Nicaragua, and Panama, with a high 1975, the first confirmations of RMSF cases in Costa Rica positivity to endemic typhus in the highlands of Guatemala.18 were given, including a fatal case.37 Additional serological Later, in a global surveillance study developed by WHO in studies in humans and animals followed.38 In contrast to 1993, eight volunteers (n=40) from El Salvador had a posi- Panama, several cases of RMSF have been confirmed in tive reaction to TG rickettsiae, using an end titer of 64 as Costa Rica since these reports in the late 1970s, and children cutoff for reactivity in immunofluorescence assays (IFAs).19 seemed to be the most affected.34,35,39 More recently, IgG antibodies against TG rickettsiae have A serological survey carried out in the late 1960s showed been found in humans from a rural town of Panama.20 To antibodies to SFG Rickettsia in sera from Costa Rica (13 the authors’ knowledge, no more recent references of TG positives of 507 samples), Honduras (3/348), Nicaragua rickettsioses in Central America are available in the scientific (1/312), and Panama (4/336).18 In that study, antibodies literature. against Rickettsia akari were detected in Costa Rica. With the exception of this report, no other information is available SFG rickettsioses about R. akari in the region. Currently, RMSF or other SFG rickettsioses have been con- At the beginning of the 21st century and in accordance firmed in the seven countries of Central America (Table 1). with the re-emergence of fatal cases of RMSF in Panama, Spotted fever rickettsiosis, and specifically RMSF, was new evidence of rickettsial diseases in other countries of originally described in the early 20th century as “piroplas- Central America was confirmed. In 2007, an investigation mosis hominis” from cases in Bitterroot Valley Montana of febrile illness in a rural area of Guatemala caused at least (USA); Dermacentor ticks were associated with transmis- 17 cases of SFG rickettsiosis, including two fatalities.40 Dur- sion.21 Later, cases were diagnosed in México (1918), Brazil ing the epidemiological investigation, DNA closely related (1929), and Colombia (1938).10,22,23 In Central America, the to Rickettsia africae and Rickettsia sibirica was detected first records of RMSF were registered in Panama in the early in A. cajennense s.l. Subsequently, in 2009, a case of SFG Research and Reports in Tropical Medicine 2018:9 submit your manuscript | www.dovepress.com 105 Dovepress Bermúdez C and Troyo Dovepress rickettsiosis was reported from a US traveler who returned R. rickettsii, R. felis, Rickettsia parkeri, and R. africae (or from Honduras.41 In Nicaragua, the first evidence of SFG very similar), as well as strains of undescribed or Candidatus rickettsiosis was reported in 2016 from patients in the acute species (Table 3). phase of infection, which also included diagnosis of Q fever.42 R. rickettsii has been detected in R. sanguineus s.l. and In this study, the sample included 825 patients and about 1% Dermacentor nitens from Panama,32,44 A. mixtum from was considered positive for SFG rickettsiosis, but specifi- Panama and Costa Rica,24,31,45 and Amblyomma varium and cally RMSF was not confirmed. In Belize, there is only one Haemaphysalis leporispalustris from Costa Rica.45,46 Con- report that supports SFG rickettsial infection in humans; the trary to A. mixtum and R. sanguineus s.l., the findings of study found a seroprevalence of 54% (IFA using R. rickettsii R. rickettsii in D. nitens, H. leporispalustris, and A. varium antigen) in a group of healthy pregnant women.43 were not associated with febrile cases, but may have impli- It is important to note that R. rickettsii has been isolated cations in public health because these are ticks that present and molecularly identified from symptomatic human cases different behavior. For example, D. nitens is a one-host tick only in Panama and Costa Rica, but not in the cases from that mainly parasitizes horses in paddocks and stubble, and Guatemala, Honduras, and Nicaragua (Table 1). In addition, parasitism in humans is rare.47 D. nitens commonly shares only Panama and Costa Rica have serological studies in environments and hosts (equines) with A. mixtum, although domestic and wild mammals (Table 2). this last species is considered an eclectic parasite, and the reports parasitizing humans are frequent.47 In contrast, adults Rickettsia species in ectoparasites in of A. varium parasite almost exclusively sloths and immature Central America have been found parasitizing birds, but very few studies men- For many decades, R. rickettsii, R. akari, R. typhi (=Rickettsia tion humans as hosts.45,48,49 Similarly, H. leporispalustris is mooseri), and R. prowazekii were the only known species an almost exclusive parasite of wild rabbits (Sylvilagus), and of Rickettsia in the region, and they were mainly character- parasitism of humans is rare.47 Thus, it is possible that the ized from patients with acute phase infections or isolated relevance of these ticks in RMSF transmission is associated from ticks in eco-epidemiological studies.23 After several with enzootic cycles. decades, and with the use of molecular tools, the detection of A. mixtum and R. sanguineus s.l. have been previously rickettsiae was extended to ecological studies, especially in implicated as vectors of R. rickettsii; in fact, several species more species of ticks. In recent years, research in the region of the A. cajennense and R. sanguineus species complexes has involved many species of ticks and fleas, which has are among its main vectors in many countries.50 Both are resulted in the detection of pathogenic rickettsiae including common in or around anthropogenic environments, but differ in preferences: A. mixtum is an eclectic parasite that Table 2 Serological evidence of rickettsial infection in domestic inhabits paddocks, stubble, and riparian vegetation, while R. and wild mammals of Central America sanguineus s.l. feeds mainly from dogs and is a nidicolous Country Rickettsia spp. Mammals References species that may thrive inside houses, including highly urban- 31,51 Costa Rica Rickettsia amblyommatisa Dog 54 ized areas. Therefore, their presence could be considered Rcikettsia felis Dog 54 as a first caveat in the transmission of RMSF.31 Even so, Cat 53 many aspects of the ecology of RMSF transmission remain Rickettsia rhipicephali Dog 54 Rickettsia rickettsii Dog 54 unknown in Central America, especially the role of domestic SFGR Dog 38,54 and wild vertebrates as reservoirs, because few studies in Wild rabbit 38 the region have focused on them. Research has resulted in (Sylvilagus sp.) serologic evidence of SFG exposure in dogs and horses from Panamá SFGR Coyoteb 55 Didelphis marsupialis 55 Panama, 51 domestic dogs and cats from Costa Rica,53,54 and R. amblyommatisa Dog 52 wild opossums (Didephis marsupialis) and coyotes from Horse 52 Panama.55 These results are a first clue of rickettsial infection D. marsupialis 55 in vertebrates that deserves further investigation. Rickettsia bellii Horse 52 R. rickettsii Horse 52 Another closely related pathogenic species, R. parkeri, Notes: aCited as Rickettsia amblyommi or Candidatus “Rickettsia amblyommii.” bThis was recently reported in Central America, infesting coyote showed symptoms similar to those described for R. rickettsii infections in Amblyomma maculatum and Amblyomma ovale (specifi- dogs. Abbreviation: SFGR, spotted fever group rickettsiosis. cally the strain Atlantic rainforest) from Belize.56,57 Although 106 submit your manuscript | www.dovepress.com Research and Reports in Tropical Medicine 2018:9 Dovepress Dovepress Rickettsia in Central America Table 3 Checklist of Rickettsia species detected in arthropods from Central America Country Rickettsia spp. Arthropod species Referencesa Belize Rickettsia amblyommatisb Amblyomma pacae 56 Amblyomma cajennense s.l.c 57 Amblyomma nr. maculatum 57 Rickettsia parkeri A. maculatum 57 Rickettsia st. Atlantic Rainforest Amblyomma ovale 56 Rickettsia sp. Ixodes affinis 56 Rhipicephalus sanguineus s.l. 56 A. ovale 56 Costa Rica R. amblyommatisb Amblyomma longirostre 96 Amblyomma mixtumd 73 A. ovale 45 Dermacentor nitens 45 R. sanguineus s.l. 45 Amblyomma geayi 85 Rickettsia bellii Amblyomma sabanerae 96 Rickettsia felis Ctenocephalides felis 73 Rickettsia rickettsii A. mixtum 45 Amblyomma varium 45 Haemaphysalis leporispalustris 46 Rickettsia sp. st. IbR/CRC Ixodes boliviensis 95 Rickettsia sp. Ixodes nr. minor 96 Rickettsia asembonensise C. felis 74 Pulex simulans 45 A. ovale 45 Rhipicephalus microplus 45 Rickettsia rhipicephali Dermacentor latus 85 Ca. “Rickettsia nicoyana” Ornithodoros knoxjonesi 92 Rickettsia sp. st. Colombianensi Amblyomma dissimile 85 El Salvador R. bellii A. sabanerae 86 Guatemala R. felis C. felis 74 Rickettsia sp. A. cajennense s.l.c 40 Honduras R. amblyommatisb A. longirostre 93 A. mixtum 93 Rickettsia st. Colombianensi A. dissimile 93 Nicaragua R. amblyommatisb Amblyomma sculptumf 98 Rickettsia africae A. ovale 98 Rickettsia st. Aragoi Amblyomma tristeg 98 Rickettsia spp. A. maculatum 97 Dermacentor dissimilis 97 R. sanguineus s.l. 97 Panamá R. amblyommatisb A. mixtum 44 A. ovale 44 D. nitens 44 Haemaphysalis juxtakochi 99 R. sanguineus s.l. 44 C. felis 52 R. bellii A. sabanerae Unpublished R. felis C. felis 52 A. mixtum 52 R. rickettsii A. mixtumd 25 R. sanguineus s.l. 32 D. nitens 44 Notes: Ticks associated with human cases of RMSF are represented in bold format. aOnly the first mention in the scientific literature is presented. bCited as Rickettsia amblyommii or Candidatus “Rickettsia amblyommii.” cA. cajennense s.l. probably corresponds to A. mixtum. dCited as A. cajennense. eCited also as R. felis genotype RF2125. fA. sculptum probably corresponds to A. mixtum. gA. triste probably corresponds to A. maculatum. Abbreviation: RMSF, Rocky Mountain spotted fever. Research and Reports in Tropical Medicine 2018:9 submit your manuscript | www.dovepress.com 107 Dovepress Bermúdez C and Troyo Dovepress A. maculatum and A. ovale frequently parasitize humans,47,58 very high serological titers in dogs.77 In Central America, until now there are no reports of human infection by these there is serological evidence of exposure in dogs, horses, species in the region. Although R. parkeri was isolated in and opossums (D. marsupialis) from Panama and dogs from 1939, its involvement as a pathogen for humans was not con- Costa Rica.52,54,55 In this country, the strain 9-CC-3-1 of R. firmed until 2004.59,60 Clinical evidence shows that R. parkeri amblyommatis was able to generate pathology and an immune infections are usually not lethal and have been confirmed response in guinea pigs, and it was protective against a sub- in several states of the USA, Argentina, and Uruguay.61–63 sequent infection with a lethal R. rickettsii strain. Therefore, Vectors of R. parkeri include A. maculatum in the USA, the presence of R. amblyommatis in the region may modulate as well as Amblyomma triste and Amblyomma tigrinum in the epidemiology and severity of RMSF in areas where both South America.60,63 the species circulate.78 In humans, despite its frequent pres- The strain Atlantic rainforest was first detected in Brazil ence in several species of ticks, there are no confirmed cases as Rickettsia sp., but recent studies suggest that it belongs of human rickettsiosis caused by R. amblyommatis, although to the species R. parkeri.64–66 This strain has been associated some authors suggest that humans develop an immune with human cases of spotted fever in Brazil, and A. ovale response and that it may cause clinical manifestations.79–82 seems to be the main vector.65 In addition to Brazil and Rickettsia rhipicephali is a species that has been reported Belize, R. parkeri strain Atlantic rainforest has been detected only once in ticks from Central America. It was first isolated in Argentina (in Amblyomma dubitatum) and Colombia (in and described in 1975 from R. sanguineus in the USA, but it A. ovale).67,68 is known to be present also in South America.83,84 This species Of the species recognized as human pathogens in Central was detected by PCR in Dermacentor latus from Costa Rica, America, R. felis is the only one that has been detected in although currently very few information is available about fleas, although no human cases have been confirmed in the this finding.85 Moreover, there is also serologic evidence of region. This Rickettsia was first observed in Ctenocephali- possible exposure of dogs to this or a very similar Rickettsia des felis in 1990; it was officially described in 1996 and the sp. from that same country, which supports its possible pres- descriptions were emended in 2002.69,70 It is distributed ence in the region.54 The pathogenic potential of R. rhipi- worldwide, as is its main invertebrate host, C. felis. Disease in cephali in humans is unknown, although the disease has been humans, known as flea-borne spotted fever, was first reported confirmed in meadow voles after experimental infections.83 in the USA, Mexico, and Brazil, although it has now been In Central America, Rickettsia bellii has been detected in reported from countries around the world; when they occur, Amblyomma sabanerae from El Salvador, Costa Rica, and symptoms are usually mild and unspecific, but severe cases Panama (S Bermúdez, unpublished data).85,86 This tick is a have been described.71,72 The first findings of R. felis in Cen- parasite of reptiles, in particular turtles and tortoises.47,51 This tral America were documented in Panama and Costa Rica in Rickettsia belongs to ancestral group different from the TG 2011, from C. felis.52,73 The report from Costa Rica recorded and SFG.3 Although no studies demonstrate its pathogenicity the first isolation of this Rickettsia in a cell line (C6/36) in the in humans, there is experimental evidence showing rickett- region. R. felis has also been detected in C. felis in Guatemala sial ability to elicit an immune responses in capybaras.87 and in dogs from Nicaragua, which suggests that it is also In Central America, there is serologic evidence of R. bellii present in fleas in that country.74,75 The absence of reports exposure in horses from Panama.52 Thus, the role of R. bellii from the other countries of Central America is probably due as a potential human pathogen deserves further investigation. to a lack of investigation of rickettsiae in fleas. Rickettsia asembonensis, which is closely related to R. It is possible that Rickettsia amblyommatis (referred felis, is also present in Central America. This is a recently to as Rickettsia amblyommii and “Candidatus Rickettsia described species, which was isolated from C. felis from amblyommii”) is the most common Rickettsia detected in Kenya,88 although it seems to be the same Rickettsia sp. Central America. It has been reported in 10 species of ticks genotype RF2125 that had been reported much earlier in and one of fleas in five of the seven countries of Central the same flea species in the Thailand–Myanmar border.89–91 America (Tables 2 and 3). This Rickettsia was isolated from R. asembonensis was first documented in C. felis from the Amblyomma americanum from the USA and has since been Caribbean slope of Costa Rica as the genotype RF2125.74 It reported along the continent.23,76 The effects of R. amblyom- was later reported from C. felis in the metropolitan area of that matis infection on vertebrates is not clearly defined. Some same country (Cartago province), as well as from other spe- authors have pointed out that repeated exposure can induce cies of ectoparasites including Pulex simulans, Rhipicephalus 108 submit your manuscript | www.dovepress.com Research and Reports in Tropical Medicine 2018:9 Dovepress Dovepress Rickettsia in Central America microplus, and A. ovale.45,54 It is unknown if this species is and fleas suggest that these bacteria are widely distributed able to infect humans or generates disease. in the region; thus, rickettsioses could be an underestimated In addition to the described species of rickettsiae, several problem in the absence of greater diagnostic efforts in unde- rickettsiae that have not been formally described have been termined febrile cases. reported in Central America. “Candidatus R. nicoyana” was first isolated from Ornithodoros knoxjonesi ticks collected Acknowledgments from bats in Costa Rica.92 Two isolates of this Rickettsia The authors thank Dr Nicole Gottdenker (University of were obtained in Vero E6 cell lines, and a partial molecular Georgia) for the helpful comments, grammatical editing, and characterization placed it in the SFG, close to “Candidatus revision of English language. A Troyo’s contributions were Rickettsia wissemanii” and Rickettsia peacockii. In addi- supported in part by University of Costa Rica project ED-548. tion, Rickettsia sp. strain Colombianensi has been detected in Amblyomma dissimile from both Honduras and Costa Disclosure Rica.85,93 This strain was first reported in A. dissimile and R. The authors report no conflicts of interest in this work. sanguineus from Colombia, and it groups phylogenetically with Rickettsia tamurae and R. monacensis within the SFG.94 References In Guatemala, a Rickettsia sp. genetically similar to R. afri- 1. Fang R, Blanton LS, Walker DH. Rickettsiae as emerging infectious agents. Clin Lab Med. 2017;37(2):383–400. cae and Rickettsia sibrica was detected in A. cajennense s.l. 2. Fenollar F, Fournier P, Raoult D. Diagnostic strategy of rickettsioses (probably A. mixtum).40 and ehrlichioses. In: Raoult D, Parola P, editors. Rickettsial Diseases. New York: Informa Healthcare; 2007:315–330. 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