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Tifo Murino: Aspectos clinicos y epidemiologicos.

Murine typhus: clinical and epidemiological aspects


Bacteria belonging Rickettsia Genus are intracelular obligate organisms, gram negative with ability to infect arthropods like fleas, ticks as well as small vertebrates.

Initially, bacteria from Rickettsia Genus have been grouped, based on their clinical manifestation, immunological reactivity, intracellular localization and G+C amount on his DNA in two groups: Tifus group (TG) and Spotted Fever Group (SFG). Phylogenetic evaluation based comparing 16RNAe gene, have been proved that Rickettsia belongs to Proteobacteria class sub group (1). Complete genome analysis from several Rickettsia species actually propose a new division in four rickettsial groups: Tifus group (Rickettsia typhi y Ricketsiaprowazekii); Spotted fever Group (Rickettsia conorii, Rickettsia sibirica, Rickettsia rickettsii); Ancestral Group (Rickettsia canadensis y Rickettsia bellii) and transition Group (Rickettsia felis y Rickettsia akari) (2).

This study will focus about infection caused by Rickettsia typhi, Rickettsia specie that belongs to Tifus Group who causes murine tifus. Rickettsia typhi was identified in 1928 by Dr. Hermann Mooser, Dr. Maximiliano Ruiz Castaneda and Dr. Hans Zinsser in Mexico studying the so-called "Mexican typhus" because of the similarity in symptoms with the exantemic typhus caused by Rickettsia prowazekii, reporting that this disease, contrary to exantemic typhus, which is transmitted by the louse is transmitted by rats and their fleas species will detail later. Initially, this Rickettsia was called like his discoverer: Hermann Mooser so the initial name was rickettsia mooserrii (3). Subsequently, this bacteria was identified in others continents considering as a bacteria with a worldwide distribution (Table 1).


Rickettsia typhi as well as Rickettsia prowazekii, belongs to Tifus Group in the Rickettsiaceae Family from Rickettsialis Order and is the causative organism of murine or endemic typhus (2). Actually, infections with Rickettsia felis are considered as a murine typhus due to similarity in symptoms with murine typhus. This causal agents, share common characteristic from all the Rickettsia species. Both are genetically similar, his classification was based on cell surface protein characterization (OmpA and OmpB) and lipopolysaccharides (LPS); due to both groups have the 17 kDa protein, lipopolysaccharides and OmpB but, unlike Rickettsia typhi, Rickettsia felis have an additional outer membrane protein OmpA2 this is why initially R. felis was considered a Spotted Fever Group Rickettsia. To date, R. felis share characteristics from both gropus are considered as a Rickettsia belonging to the transition Group (2).

Both bacterias a located in celular cytoplasm at the infection time, having the characteristic of freedom from the vacuole formed when Rickettsia enter to the cell by induced phagocytosis by the same Rickettsia (3)


This cycle are composed by mammals host (rats and humans) and vectors (fleas). The classic natural cycle of this agent includes as a reservoirs two rats species (Rattus rattus and Rattus norvergicus) and the flea Xenopsilla cheopsis as a vector. Figure 1. The fleas acquire the infection from rats with rickettsemia maintaining the infection during all his life but not killing the vector. Infection in humans are acquire in three different ways, being the most frequent way he self-inoculation from feces of fleas in the bite area and nails, this due to the presence of fleas in skin which produces itching that leads to the itching. Other transmission way includes bite and inhalation of flea infected feces when the hygienic conditions are inapropiated (4). This classic cycle is still the main cause of endemic typhus in some regions in Greece, United States (5). In other areas, murine thyphus have other patterns not characterized. The main aspect is the presence of others reservoirs (i. e. cats, dogs or opossums), other vector and many others Rickettsia species (6). In United States, contrary to the classic cycle rat-flea-rat, the most important reservoirs are opossums from the gender Dydelphis and catsl the cat flea, Ctenocephalides felis also have been identified as a vector (4).


Results obtained about endemic typhus pathogeny are mainly based in vitro studies.

Rickettsial pathogeny depends of intracythoplasmatic niche rich in nutrients and grows requirements inside the cell host. Invasion to cell is an essential previous requirement for intracellular replication and afterall intracellular diffusion.

After the entry of the organism through the skin or the respiratory system spread via the lymphatic and / or blood to the endothelial cells that are its main target. Endothelial injury is the key element in the pathogenic and pathophysiology of endemic typhus. R. typhi adheres to endothelial cells through outer membrane proteins. Among the major outer membrane surface proteins are OmpA and OmpB which are present in the Rickettsial Spotted Fever Group and the Transition Group, while the Typhus Group Rickettsia only have OmpB and his cellular receptor still unknown. Although, initial OmpA inhibition studies, identified as a protein critical for R. rickettsii adhesion to host cells (7), recent studies based on proteomic analysis has revealed two new alleged Rickettsial adhesins, one of which is the C-terminal peptide of [beta] rOmpB and the other is encoded by the gene RC1281 in R. conorii and RP828 gene in R. prowazekii (8). Interestingly, OmpB interacts with Ku70 a predominance of nuclear DNA-dependent of protein kinase, which is also present in the cytoplasm and plasma membrane, and this interaction has been implicated in the internalization R. conorii in Vero cells and HeLa Cells. Immediately to his adhesion, R. typhi penetrate endothelial cells by phagocytosis induced by the pathogen. Rickettsial invasion requires the presence of cholesterol-rich microdomains containing Ku70 and the ubiquitin ligase, c-CBL, the input focus to the ubiquitination of Ku70 (9).

There is additional evidence for possible involvement coordinated upstream through the signaling mechanisms Cdc42 (a GTPase), phosphoinositide 3-kinase, c-Src and other tyrosine kinases in the activation of pathways Arp2 / 3 complex or other. However, activation of p38 MAPK suggests a role for actin polymerization in host cell internalization Rickettsia (15,16). this way, recent evidence also suggests that Ku70-rOmpB interactions are sufficient to mediate invasion of host cells and Rickettsia non phagocytic internationalization process also includes contributions to endocytosis via clathrin-and caveolin-2-dependent (10). Recent research with electron microscopy indicate that the entry of Rickettsia in mammalian cells occurs within minutes after contact, this interaction, therefore, is almost instantaneous and once internalized, Rickettsia is able to escape quickly in the cytoplasm, probably before fusion phage-lisosoma and is suspected is done through a phospholipase activity (11).

In fact, phospholipase activity may be responsible for damage to the host cell membrane that occurs during entry and exit of the Rickettsia from cells. Once inside, spreads to nearby cells by a peculiar mechanism involving rearrangement of actin and endothelial cell production of direct endothelial injury in which free oxigen radicals are involved (7).


Clinical manifestations begin after 7-14 days nonspecifically incubation period; the most common symptoms are fever, musculoskeletal pain, headache and rash. This occurs in 60-70% of cases, usually appears on the fifth day of onset of symptoms and lasts an average of 4 days is usually maculopapular thin, affecting the trunk and extremities and respects the palms and soles. The clinical course in most cases is mild with fever and disappearance of additional symptoms in 10-14 days, the specific treatment defervescence occurs in 2-4 days. The percentage of organ-specific complications (pneumonitis, hepatitis, meningoencephalitis, renal failure) does not usually exceed 10%, and severe cases (development of refractory shock, respiratory distress, multiple organ failure, hemorrhagic diathesis, consumptive coagulopathy, or severe neurological compromise) there are only around 2-4%, mortality of murine typhus ranges from 0-1%. Different factors have been associated with a more severe course of disease, among which are age, the presence of various hematologic diseases (hemoglobinopathies), early laboratory abnormalities such as renal failure, hypoalbuminemia, hyponatremia and hypokalemia, the late start of treatment effective treatment cotrimoxazol (12).


Historically, differentiation between Rickettsia species has been carried out by serological and many other methods.

The Weil-Felix test was used in the past as a presumptive test for the identification of rikettsiosis in routine laboratories, is based on the detection of antibodies to various Proteus species which contain antigens that cross-react against epitopes of members of the genus Rickettsia with the exception of R. akari (13). However, the low sensitivity and specificity of the Weil-Felix test for diagnosis of RMSF (Rocky Mountain Spotted Fever) (14), place it as a test of limited relevance to be used in the clinic.


ELISA Test (enzyme immunoassay) was the first to be introduced for the detection of antibodies against R. typhi and R. prowazekii, the use of this technique is very sensitive and reproducible. This technique allows the differentiation of IgG and IgM, and has been adapted for the diagnosis of RMSF and scrub typhus (15).

Another serological test hasn't been widely used, is the microagglutination due to the need of large quantities of purified rickettsial antigen and these antigens are not available commercially (15).

The IFA (immunofluorescence assay) technique is the "gold standard" and is used as a reference technique in most research laboratories for serodiagnosis of rickettsiasis, to determine IgG and / or IgM. IFA identification of specific IgM antibodies in several species of Rickettsia provides strong evidence of recent active infection, although the diagnosis may be obscured by a prozone phenomenon and can also be affected by the rheumatoid factor (16).

The immunoperoxidase assay was developed as an alternative to IFA for the diagnosis of scrub typhus and was later evaluated for use in the diagnosis of infections caused by R. conorii and R. typhi, the sensitivity and specificity obtained by immunoperoxidase assay for the serodiagnosis of scrub typhus, epidemic typhus, and MSF (Mediterranean spotted fever) is similar to those obtained by IFA17. The first proposed method of identification based on molecular biology was the PCR / RFLP method of the gene that encodes citrate synthase, which allowed differentiation of nine species of rickettsiae of SFG. Later, using a combination with a method based on PCR-RFLPs analysis of ompB gene fragment allowed differentiation of 36 strains of SFG (18)


This disease is endemic in temperate climates and especially in coastal areas. In the United States, Asia, Australia, Mexico and Spain. Table 1, Figure 2. Also have been founded R. typhi infection in different species of wild mammals in different parts of the world which can include rodents (Rattus rattus, Rattus norvergicus), opossums (Gender Dydelphis) and dogs as well as consider endemic typhus as a disease imported by travelers and refugees (19). It has been shown by studies of incidence of this disease in different countries, which are seasonal, in which the majority of cases occurring in a year is higher during warm weather, while cold weather, infection is very low or almost zero. This disease occurs in all age groups and is relatively common in children. As regards distribution by sex, race and occupation of patient no significant differences, although people living in rural or disadvantaged areas are more prone to infection

In America, there are records of this disease caused by Rickettsia typhi in Mexico since 1928, which, as already mentioned in the introduction, in collaboration with Hermann Mooser, Maximiliano Ruiz Castaneda and Hans Zinsser identify the causative agent of murine typhus or endemic in Mexico (3). Currently there have been reports of the presence of Rickettsia typhi in America in countries like Brazil in 2005, which reports the presence of rickettsial antibodies to Rickettsia typhi in a rural community as well as other Rickettsia and Rickettsia rickettsii, causal agent of Rocky Mountain Spotted Fever (20); similar study was conducted in Argentina also founding these antibodies in a healthy population of a community rural (21). The importance about these studies is the presence of R. typhi in the population which has already been infected possibly being misdiagnosed.


Rickettsia typhi is a common bacteria all over the world, is preferably in warm climates and coastal areas. His wild vectors and reservoirs are very common in most countries. Murine typhus, the disease caused by this bacterium is related through history with famine and overcrowding, with the rural population more susceptible to infection. Today, in Mexico, the knowledge that we have about this disease is very rare because there have been no reports of this infection in our country since the mid-twentieth century, where in central Mexico which subsequently caused epidemics able to control disease was considered eradicated. It was early 2000 when it was detected in a seroprevalence study in the State of Mexico, the presence of antibodies against R typhi and in late 2009 where he reported the first case of Rickettsia typhi infection in Yucatan State, Mexico by possibly have been filed or are filing cases of infection by R. typhi and ignorance of the disease is not diagnosed correctly. In Mexico, medical school curricula listed as a rickettsial disease which is not present in the country which leads to ignorance of the disease and its confusion with a fever caused by Dengue in most cases. A serious strategy to update the curriculum to include rickettsial infection as a health problem in Mexico and possibly other countries. Also, the needs to identify their presence and life cycle not only in Mexico but in the Americas since principlamete are tropical regions where they might be other vectors of this rickettsial species which unfortunately to be low-income areas, can be a greater likelihood of infection, since it has the geographic and climatic conditions to dwell this bacterium. This study was conducted with the aim of presenting the most complete information about R. typhi and the disease it causes to which the Mexican community and the continent is exposed.


Authors of this manuscript declare that there are any conflict of interest (financial, research, heritage, etc.) in the submitted manuscript.

Article info

Article history:

Received 28 march 2011

Received in revised form 13 June 2011

Accepted 11 Augost 2011

Available online 25 june 2012


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(3.) Martinez Mendoza MdlD. Historia del tifo epidemico desde la epoca prehispanica hasta nuestros dias. Sist Nal de Vig Epidemiol. 2005;22(42):1-4.

(4.) Boostrom A, Beier MS, Macaluso JA, et al. Geographic association of Rickettsia felis-infected opossums with human murine typhus, Texas. Emerg Infect Dis. 2002;8(6):549-554.

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(6.) Sorvillo FJ, Gondo B, Emmons R, et al. A suburban focus of endemic typhus in Los Angeles County: association with seropositive domestic cats and opossums. Am J Trop Med Hyg. 1993;48(2):269-273.

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(16.) 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(1):51-61.

(17.) Suto T. A ten years experience on diagnosis of rickettsial diseases using the indirect immunoperoxidase methods. Acta Virol. Nov 1991;35(6):580-586.

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(19.) Rolain JM, Jensenius M, Raoult D. Rickettsial infections-a threat to travellers? Curr Opin Infect Dis. Oct 2004;17(5):433-437.

(20.) da Costa PS, Brigatte ME, Greco DB. Antibodies to Rickettsia rickettsii, Rickettsia typhi, Coxiella burnetii, Bartonella henselae, Bartonella quintana, and Ehrlichia chaffeensis among healthy population in Minas Gerais, Brazil. Mem Inst Oswaldo Cruz. Dec 2005;100(8):853-859.

(21.) Ripoll CM, Remondegui CE, Ordonez G, et al. Evidence of rickettsial spotted fever and ehrlichial infections in a subtropical territory of Jujuy, Argentina. Am J Trop Med Hyg. Aug 1999;61(2):350-354.

Gaspar Peniche Lara * (ab), Karla R. Dzul-Rosado (ac), Jorge Ernesto Zavala Velazquez (ab), Jorge Zavala-Castro (ac)

(a) Universidad Autonoma de Yucatan, Mexico

(b) Unidad Interinstitucional de Investigacion clinica y Epidemiologica, Facultad de Medicina,

(c) Centro de Investigaciones Regionales "Dr Hideyo Noguchi", Facultad de Medicina,

* Corresponding author

E-mail adress: (Peniche G), karla.dzul@ (Dzul-Rosado KR), ( Zavala JE), (Zavala J)
Table 1. R. typhi reports in the XXI century

PAIS               METODO          REFERENCIA

  Brazil           IFA         Gonzalez et al. Mem Inst Oswaldo Cruz
                                 2005; 100(8): 853-859.
  Argentina        IFA         Ripio et al. Am. J. Trop. Med. Hyg,
                                 1999; 61(2), 350-354.
  Estados Unidos   IFA         Adjemian et al. Emerg Infect Dis.
                                 2010; 16(3): 412-417.
                   IFA         Purcell et al. Emerg Infect Dis. 2007;
                                 13(6): 926-927
                   IFA         Smith et al. J Infect Dis. 2002;
                   PCR         Eremeeva et al. Emerg Infect Dis.
                                 2008; 14(10): 1613-1615.
                   IFA         Reeves et al. Vector Borne Zoonotic
                                 Dis. 2006; 6(3): 244-247.
                   IFA         Reeves et al. J Vector Ecol.
                                 2008; 33(1): 205-207.
                   IFA,        Boostrom et al. Emerg Infect Dis.
                   PCR           2002; 8(6): 549-554.
  Mexico           PCR         Zavala--Castro et al. Emerg Infect Dis.
                                 2009; 15(6): 972-974
  Colombia         IFA         Hidalgo. Am. J. Trop. Med. Hyg.
                                 2008; 78(2): 321-322.
  Francia          IFA         La Scola et al. Clin Diagn Lab Immunol.
                                 2000 July; 7 (4): 612-616.
  Espana           IFA         Lledo et al. Eur J Epidemiol.
                                 2001; 17(10):.927-928.
                   IFA         Hernandez-Cabrera. Emerg Infect Dis.
                                 2004; 10 (4): 740-743.
                   IFA,        Lledo et al. Int J Environ Res
                   PCR           Public Health. 2009; 6: 2526-2533.
  Croacia          IFA         Punda-Polic. Epidemiol Infect.
                                 2008; 163; 972-979.
  Portugal         PCR         De Sousa et al. Am J Trop Med Hyg
                                 2006; 75(4): 727-731.
  Chipre           IFA         Koliou et al. Eur J Clin Microbiol
                                 Infect Dis. 2007; 26: 491-493.
  Grecia           IFA         Gikas et al. Clin Microbiol Infect.
                                 2009;15 Suppl 2:.211-2.
  Corea            PCR         Kim et al. J Wildl Dis.
  Indonesia        IFA         Gasem et al. Emerg Infect Dis.
                                 2009; 15(6):975-7.
                   ELISA         Richards et al. Am J Trop Med Hyg.
                                 2002; 66(4):431-4.
  Nepal            PCR         Zimmerman et al. Emerg Infect Dis.
                                 2008; 14(10):1656-9
  China            IFA         Zhang et al. Emerg Infect Dis.
                                 2008; 14(6):938-40
  Japon            IFA         Sakaguchi et al Emerg Infect Dis.
                                 2004; 10(5):964-5
  Sri Lanka        IFA         Kularatne et al. Trop Med Int Health.
                                 2003; 8(9):803-11.
  Bangkok          IFA         Siritantikorn et al. J Med Assoc Thai.
                                 2003; 86(6):516-21
  Singapur         IFA         Ong A et al Singapore Med J. 2001;
                                 42(12): 549-552
  Malasia          Inmu-no     Tay y Rohani. Southeast Asian J Trop
                   peroxidasa    Med Public Health. 2002 Jun;
                   Indirecta    33(2): 314-20

  Kuala Lumpur     ELISA       Sekhar y Devi. Singapore Med J.
                                 2000; 41(5):226-31.
  Nueva Zelanda    IFA         Roberts et al. N Z Med J. 2001;
                                 114(1138): 372-375.
                   IFA,        Roberts et al. New Zealand Public
                    PCR          Health Report. 2001; 8(10): 73-75
                   IFA         Gray et al. N Z Med J. 2007 August;
                                 120(1259): 19-26.
  Australia        ---         Graves y Stenos. Ann N Y Acad Sci.
                                 2009; 1166:151- 155.
  Tunez            IFA         LetaTef et al. Int J Infect Dis.
                                 2005; 9: 331-334.
                   IFA         Khairallahet al. Br J Opthalmol.
                                 2009; 938-942.
  Egipto           IFA         Rozsypal et al. Klin Mikrobiol Infekc
                                 Lek. 2006; 12(6): 244-246
  Argelia          Western     Mouffok et al. Emerg Infect Dis.
                     Blot            2008; 14 (4); 676-678.
  Libia            Syntoma-    Sable et al. Southeast Asian J Trop
                     tology      Med Public Health. 2009; 40(4):
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Title Annotation:articulo en ingles
Author:Peniche Lara, Gaspar; Dzul-Rosado, Karla R.; Zavala Velazquez, Jorge Ernesto; Zavala-Castro, Jorge
Publication:Colombia Medica
Article Type:Perspectiva general de la enferm
Date:Apr 1, 2012
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