Reemerging threat of epidemic typhus in Algeria

La Valentine disease: An outbreak of exanthematic typhus in Marseille, France, in 1810

BACKGROUND

Exanthematic typhus was highly frequent in the early 19th century among military troops and prisoners and at hospitals.

METHODS

Based on old reports, we describe an outbreak in a village, in Southern France, in 1810.

RESULTS

Twenty-eight cases were identified, over a period of 10 days following the death of the index case, in a soldier. Symptoms included notably persistent constant fever, myalgia and headaches, gastro-intestinal symptoms, prostration and stupor. Three patients suffered delirium and nine died (31.0%). Overall, symptoms persisted for 13-14 days. A total of 16 cases were secondary to contacts with the index case, and 10 cases were in house-hold contacts of secondary cases. Five familial clusters were described.

CONCLUSION

This data suggest that exanthematic typhus outbreaks among civilian populations also occurred outside the context of hospitals, in link with introduction of the disease by prisoners or soldiers.

Emerging bacterial infectious diseases/pathogens vectored by human lice

Human lice have always been a major public health concern due to their vector capacity for louse-borne infectious diseases, like trench fever, louse-borne relapsing fever, and epidemic fever, which are caused by Bartonella quintana, Borrelia recurrentis, and Rickettsia prowazekii, respectively. Those diseases are currently re-emerging in the regions of poor hygiene, social poverty, or wars with life-threatening consequences. These louse-borne diseases have also caused outbreaks among populations in jails and refugee camps. In addition, antibodies and DNAs to those pathogens have been steadily detected in homeless populations. Importantly, more bacterial pathogens have been detected in human lice, and some have been transmitted by human lice in laboratories. Here, we provide a comprehensive review and update on louse-borne infectious diseases/bacterial pathogens.

Pathogenicity and virulence of Rickettsia

Rickettsiae include diverse Gram-negative microbial species that exhibit obligatory intracellular lifecycles between mammalian hosts and arthropod vectors. Human infections with arthropod-borne Rickettsia continue to cause significant morbidity and mortality as recent environmental changes foster the proliferation of arthropod vectors and increased exposure to humans. However, the technical difficulties in working with Rickettsia have delayed our progress in understanding the molecular mechanisms involved in rickettsial pathogenesis and disease transmission. Recent advances in developing genetic tools for Rickettsia have enabled investigators to identify virulence genes, uncover molecular functions, and characterize host responses to rickettsial determinants. Therefore, continued efforts to determine virulence genes and their biological functions will help us understand the underlying mechanisms associated with arthropod-borne rickettsioses.

The History of Epidemic Typhus

Epidemic typhus caused by Rickettsia prowazekii is one of the oldest pestilential diseases of humankind. The disease is transmitted to human beings by the body louse Pediculus humanus corporis and is still considered a major threat by public health authorities, despite the efficacy of antibiotics, because poor sanitary conditions are conducive to louse proliferation. Epidemic typhus has accompanied disasters that impact humanity and has arguably determined the outcome of more wars than have soldiers and generals. The detection, identification, and characterization of microorganisms in ancient remains by paleomicrobiology has permitted the diagnosis of past epidemic typhus outbreaks through the detection of R. prowazekii. Various techniques, including microscopy and immunodetection, can be used in paleomicrobiology, but most of the data have been obtained by using PCR-based molecular techniques on dental pulp samples. Paleomicrobiology enabled the identification of the first outbreak of epidemic typhus in the 18th century in the context of a pan-European great war in the city of Douai, France, and supported the hypothesis that typhus was imported into Europe by Spanish soldiers returning from America. R. prowazekii was also detected in the remains of soldiers of Napoleon's Grand Army in Vilnius, Lithuania, which indicates that Napoleon's soldiers had epidemic typhus. The purpose of this article is to underscore the modern comprehension of clinical epidemic typhus, focus on the historical relationships of the disease, and examine the use of paleomicrobiology in the detection of past epidemic typhus outbreaks.

Molecular and serological evidence of flea-associated typhus group and spotted fever group rickettsial infections in Madagascar

Background

Rickettsiae are obligate intracellular bacteria responsible for many febrile syndromes around the world, including in sub-Saharan Africa. Vectors of these pathogens include ticks, lice, mites and fleas. In order to assess exposure to flea-associated Rickettsia species in Madagascar, human and small mammal samples from an urban and a rural area, and their associated fleas were tested.

Results

Anti-typhus group (TGR)- and anti-spotted fever group rickettsiae (SFGR)-specific IgG were detected in 24 (39%) and 21 (34%) of 62 human serum samples, respectively, using indirect ELISAs, with six individuals seropositive for both. Only two (2%) Rattus rattus out of 86 small mammals presented antibodies against TGR. Out of 117 fleas collected from small mammals, Rickettsia typhi, a TGR, was detected in 26 Xenopsylla cheopis (24%) collected from rodents of an urban area (n = 107), while two of these urban X. cheopis (2%) were positive for Rickettsia felis, a SFGR. R. felis DNA was also detected in eight (31%) out of 26 Pulex irritans fleas.

Conclusions

The general population in Madagascar are exposed to rickettsiae, and two flea-associated Rickettsia pathogens, R. typhi and R. felis, are present near or in homes. Although our results are from a single district, they demonstrate that rickettsiae should be considered as potential agents of undifferentiated fever in Madagascar.

CD4+ T Cells Are as Protective as CD8+ T Cells against Rickettsia typhi Infection by Activating Macrophage Bactericidal Activity

Rickettsia typhi is an intracellular bacterium that causes endemic typhus, a febrile disease that can be fatal due to complications including pneumonia, hepatitis and meningoencephalitis, the latter being a regular outcome in T and B cell-deficient C57BL/6 RAG1^-/- mice upon Rickettsia typhi infection. Here, we show that CD4⁺ T_H1 cells that are generated in C57BL/6 mice upon R. typhi infection are as protective as cytotoxic CD8⁺ T cells. CD4⁺- as well as CD8⁺-deficient C57BL/6 survived the infection without showing symptoms of disease at any point in time. Moreover, adoptively transferred CD8⁺ and CD4⁺ immune T cells entered the CNS of C57BL/6 RAG1^-/- mice with advanced infection and both eradicated the bacteria. However, immune CD4⁺ T cells protected only approximately 60% of the animals from death. They induced the expression of iNOS in infiltrating macrophages as well as in resident microglia in the CNS which can contribute to bacterial killing but also accelerate pathology. In vitro immune CD4⁺ T cells inhibited bacterial growth in infected macrophages which was in part mediated by the release of IFNγ. Collectively, our data demonstrate that CD4⁺ T cells are as protective as CD8⁺ T cells against R. typhi, provided that CD4⁺ T_H1 effector cells are present in time to support bactericidal activity of phagocytes via the release of IFNγ and other factors. With regard to vaccination against TG Rickettsiae, our findings suggest that the induction of CD4⁺ T_H1 effector cells is sufficient for protection.

Endemic typhus caused by Rickettsia typhi usually is a relatively mild disease. However, CNS inflammation and neurological symptoms are complications that can occur in severe cases. This outcome of disease is regularly observed in T and B cell-deficient C57BL/6 RAG1^-/- mice upon infection with R. typhi. We show here that CD4⁺ T cells are as protective as cytotoxic CD8⁺ T cells against R. typhi as long as they are present in time. This is evidenced by the fact that neither CD8⁺ nor CD4⁺ T cell-deficient C57BL/6 mice develop disease which is also true for R. typhi-infected C57BL/6 RAG1^-/- mice that receive immune CD8⁺ or CD4⁺ at an early point in time. Moreover, adoptive transfer of immune CD4⁺ T cells still protects approximately 60% of C57BL/6 RAG1^-/- mice when applied later in advanced infection when the bacteria start to rise. Although CD8⁺ T cells are faster and more efficient in bacterial elimination, R. typhi is not detectable in CD4⁺ T cell recipients anymore. We further show that immune CD4⁺ T cells activate bactericidal functions of microglia and macrophages in the CNS in vivo and inhibit bacterial growth in infected macrophages in vitro which is in part mediated by the release of IFNγ. Collectively, we demonstrate for the first time that CD4⁺ T cells alone are sufficient to protect against R. typhi infection. With regard to vaccination our findings suggest that the induction of R. typhi-specific CD4⁺ T_H1 effector T cells may be as effective as the much more difficult targeting of cytotoxic CD8⁺ T cells.

Infectious Diseases

Livelihoods play a role in the infectious diseases that a population can be exposed to and the risk attached to it. Poor living conditions, lack of income and other basic amenities such as safe drinking water and toilets, poor healthcare facilities and low literacy levels have contributed to the spread of infectious diseases in rural communities. Depending on the mode of transmission these diseases can spread from one person, to communities, to a country, across borders and a whole region. This makes infectious diseases one of the most dangerous threats to the global population. There are still millions of people affected by infectious diseases worldwide, most of which live in poor rural regions of developing countries. These rural communities, which depend on livelihoods such as farming, fishing, livestock rearing, hunting and so on, are vulnerable to infectious diseases and their livelihoods are affected by the impact of these diseases.

Drought and epidemic typhus, central Mexico, 1655-1918

Epidemic typhus is an infectious disease caused by the bacterium Rickettsia prowazekii and transmitted by body lice (Pediculus humanus corporis). This disease occurs where conditions are crowded and unsanitary. This disease accompanied war, famine, and poverty for centuries. Historical and proxy climate data indicate that drought was a major factor in the development of typhus epidemics in Mexico during 1655–1918. Evidence was found for 22 large typhus epidemics in central Mexico, and tree-ring chronologies were used to reconstruct moisture levels over central Mexico for the past 500 years. Below-average tree growth, reconstructed drought, and low crop yields occurred during 19 of these 22 typhus epidemics. Historical documents describe how drought created large numbers of environmental refugees that fled the famine-stricken countryside for food relief in towns. These refugees often ended up in improvised shelters in which crowding encouraged conditions necessary for spread of typhus.

Human rickettsioses in the Batna area, eastern Algeria

In order to investigate the prevalence of rickettsioses in febrile exanthemas in eastern Algeria, we conducted a prospective serological analysis of all patients presenting with this clinical picture at the Infectious Diseases Department in the Batna Hospital from January 2000 to September 2006. One hundred and eight adult patients were included in the study, 46% of whom younger than 25 years, and 72.5% were admitted from May to September. Patients were tested for antibodies to Rickettsia conorii conorii, R. conorii israelensis, R. aeschlimannii, R. felis, R. sibirica mongolitimonae, R. africae, R. massiliae, R. typhi, and R. prowazekii using microimmunofluorescence and Western blot as confirmation procedure. Both methods confirmed the diagnosis of Mediterranean spotted fever in 5 patients (4.6%), flea spotted fever in 2 patients (1.9%), and R. aeschlimannii infection in 2 patients (1.9%). In addition, 4 patients were diagnosed as having murine typhus (3.7%) and one with epidemic typhus (0.9%). To the best of our knowledge, this is the first report of R. felis infection and R. aeschlimannii infection in Algeria. In conclusion, at least 5 different kinds of rickettsiosis coexist in eastern Algeria and, being responsible for 13% of cases of febrile exanthemas, should be considered among major causes of this clinical picture in this area. In addition, we emphasize the high incidence of typhus group rickettioses, including epidemic typhus, in this area.

Structure of 3-ketoacyl-(acyl-carrier-protein) reductase from Rickettsia prowazekii at 2.25 Å resolution

Rickettsia prowazekii, a parasitic Gram-negative bacterium, is in the second-highest biodefense category of pathogens of the National Institute of Allergy and Infectious Diseases, but only a handful of structures have been deposited in the PDB for this bacterium; to date, all of these have been solved by the SSGCID. Owing to its small genome (about 800 protein-coding genes), it relies on the host for many basic biosynthetic processes, hindering the identification of potential antipathogenic drug targets. However, like many bacteria and plants, its metabolism does depend upon the type II fatty-acid synthesis (FAS) pathway for lipogenesis, whereas the predominant form of fatty-acid biosynthesis in humans is via the type I pathway. Here, the structure of the third enzyme in the FAS pathway, 3-ketoacyl-(acyl-carrier-protein) reductase, is reported at a resolution of 2.25 Å. Its fold is highly similar to those of the existing structures from some well characterized pathogens, such as Mycobacterium tuberculosis and Burkholderia pseudomallei, but differs significantly from the analogous mammalian structure. Hence, drugs known to target the enzymes of pathogenic bacteria may serve as potential leads against Rickettsia, which is responsible for spotted fever and typhus and is found throughout the world.

Evidence of a louse-borne outbreak involving typhus in Douai, 1710-1712 during the war of Spanish succession

Background

The new field of paleomicrobiology allows past outbreaks to be identified by testing dental pulp of human remains with PCR.

Methods

We identified a mass grave in Douai, France dating from the early XVIII^th century. This city was besieged during the European war of Spanish succession. We tested dental pulp from 1192 teeth (including 40 from Douai) by quantitative PCR (qPCR) for R. prowazekii and B. quintana. We also used ultra-sensitive suicide PCR to detect R. prowazekii and genotyped positive samples.

Results and Discussion

In the Douai remains, we identified one case of B. quintana infection (by qPCR) and R. prowazekii (by suicide PCR) in 6/21 individuals (29%). The R. prowazekii was genotype B, a genotype previously found in a Spanish isolate obtained in the first part of the XX^th century.

Conclusion

Louse-borne outbreaks were raging during the XVIII^th century; our results support the hypothesis that typhus was imported into Europe by Spanish soldiers from America.

Rickettsial and ehrlichial infections

Rickettsial diseases represent a clinically homogeneous group of infections characterized by fever, headache myalgias, variable presence of a rash, and a broad spectrum of neurological manifestations. Epidemiological information including time of year, geography, history of arthropod exposure, and animal contact gives important clues to the diagnosis, and should be actively elicited. Abnormalities in hematological indices of liver function tests should also increase suspicion for illness. Delay in initiation of doxycycline therapy while awaiting laboratory confirmation of infection has been associated with progressive neurological impairment and death. Clinicians should maintain a low threshold to initiate empiric therapy for rickettsial diseases in any patient with neurological findings and compatible exposures, signs, or laboratories, as these syndromes represent readily treatable causes of neurological dysfunction.

Adipose tissue serves as a reservoir for recrudescent Rickettsia prowazekii infection in a mouse model

Brill-Zinsser disease, the relapsing form of epidemic typhus, typically occurs in a susceptible host years or decades after the primary infection; however, the mechanisms of reactivation and the cellular reservoir during latency are poorly understood. Herein we describe a murine model for Brill-Zinsser disease, and use PCR and cell culture to show transient rickettsemia in mice treated with dexamethasone >3 months after clinical recovery from the primary infection. Treatment of similarly infected mice with cyclosporine failed to produce recrudescent bacteremia. Therapy with doxycycline for the primary infection prevented recrudescent bacteremia in most of these mice following treatment with dexamethasone. Rickettsia prowazekii (the etiologic agent of epidemic typhus) was detected by PCR, cell culture, and immunostaining methods in murine adipose tissue, but not in liver, spleen, lung, or central nervous system tissues of mice 4 months after recovery from the primary infection. The lungs of dexamethasone-treated mice showed impaired expression of beta-defensin transcripts that may be involved in the pathogenesis of pulmonary lesions. In vitro, R. prowazekii rickettsiae infected and replicated in the murine adipocyte cell line 3T3-L1. Collectively these data suggest a role for adipose tissue as a potential reservoir for dormant infections with R. prowazekii.

Epidemiology of rickettsioses in North Africa

The first description of Mediterranean spotted fever (MSF) was made by Conor and Brush in 1910 in Tunisia, where, at the same time, Nicolle described the role of lice in transmission of epidemic typhus. However, along this century, there have been few and fragmentary reports about ecology and epidemiology of rickettsioses in North Africa. This region was always considered, for these diseases, like other Mediterranean regions. The most human tick-borne rickettsiosis known to occur in North Africa is MSF caused by R. conorii and transmitted by the brown dog tick, Rhipicephalus sanguineus. Recent studies showed that other arthropode-transmitted rickettsiae are prevalent in North Africa: R. aeschlimannii, R. massiliae, and R. felis. Moreover, R. felis and R. aeschlimannii human infection were respectively confirmed, by serology in Tunisia, and by PCR in Morocco. The seroprevalence of R. conorii among healthy population was ranging from 5% to 8% in most of the countries. Epidemiological and clinical features are frequently resumed in an eruptive fever with eschar occurring in hot season in rural areas. Typhus group rickettsioses, caused by R. typhi and R. prowazekii are less frequently reported than in the 1970s. Seroprevalence of R. typhi among blood donors was from 0.5% to 4%. In Algeria about 2% of febrile patients had R. prowazekii antibodies. Moreover, reemerging threat of epidemic typhus should be considered, after the two cases recently diagnosed in the highlands of Algeria. Murine typhus, considered as "benign" typhus, is underestimated. When R. typhi was inserted in serologic tests, murine typhus became more frequently confirmed. In a recent study in Central Tunisia, we confirmed an emergence of murine typhus mistaken for R. conorii or viral infection. In addition to typhus surveillance, future studies have to determine which spotted fever group rickettsiae are prevalent in vectors and in human pathology.

Reemergence of Rickettsiosis in Oran, Algeria

The presumptive cases of Mediterranean spotted fever have been identified in 1993 and since that time, its frequency has steadily increased. The prospective study, in summer 2004, was conducted in order to present the descriptive clinic and epidemiology, to identify more severe forms, the presence of the multiple eschars, and different rickettsial strains caused the disease in our region. In Oran, the cases were diagnosed clinically. In Marseille, serum specimens were tested by IFA using the panel of eight rickettsial antigen; Western blot and cross-adsorption studies were also performed in order to confirm the diagnosis. Ninety-three patients clinically diagnosed were recorded from July 3 to October 28, 2004. Eighty percent were male, the mean age was 44.3 years, 90% were exposed to dog and 32% reported tick bites. Clinical signs were as follow: presence of underlying disease (44%), sudden onset (78%), fever (100%), loss of weight (63%), conjunctivitis (43%), and a tache noire was noticed in 70%. Interestingly, two patients had two and three eschars, respectively. The rash was maculopapular (palm and sole) and purpuric in nine cases. Doxycycline was the most antibiotic (91%) with favourable outcome in 91% of the cases. Malignant form with death is reported for three patients (3.2%). Among the 93 patients, 104 serum from 65 patients were tested (serums of others patients were lost or ticket not found on tube. Sixty-three patients out of 65 had a positive serology by IFA with cross-reactive antibodies especially between R. conorii, R. felis and/or R. typhi. Two others negative serology were: one precocious serum and second from the patient, which presented symptoms of MSF and tested two serums, Western blot and cross-adsorption.

Rickettsia prowazekii and real-time polymerase chain reaction

This highly standardized and adaptable assay could improve epidemic typhus surveillance.

Rickettsia prowazekii is the causative agent of epidemic typhus and a potential bioterrorism agent. Sensitive and specific rapid assays are needed to complement existing methods of detecting this organism. We developed a real-time quantitative polymerase chain reaction assay by using a species-specific probe targeting the gltA gene. This assay, which was rapid, specific for R. prowazekii only, and sensitive (cutoff detection of 1 to 5 copies per sample), detected and directly identified R. prowazekii in blood of 12 experimentally infected mice sampled at day 3 and 6 postinfection or in naturally or experimentally infected lice. Because our assay is highly standardized and easily adaptable, it could improve epidemic typhus surveillance in public health programs, especially for countries with underdiagnosed or unrecognized human cases.

LOUSE-BORNE BACTERIAL PATHOGENS IN LICE (PHTHIRAPTERA) OF RODENTS AND CATTLE FROM EGYPT

We collected 1,023 lice, representing 5 species, from rats and domestic cattle throughout 13 governorates in Egypt and tested these lice for Anaplasma marginale, Bartonella spp., Brucella spp., Borrelia recurrentis, Coxiella burnetii, Francisella tularensis, and Rickettsia spp. by PCR amplification and sequencing. Five different louse-borne bacterial agents were detected in lice from rodents or cattle, including "Bartonella rattimassiliensis", "B. phoceensis", and Bartonella sp. near Bartonella tribocorum, Coxiella burnetii, and Rickettsia typhi. More lice from governorates bordering the Mediterranean and Red Seas contained pathogens. Our data indicate that lice of urban and domestic animals harbor pathogenic or potentially pathogenic bacterial agents throughout Egypt.

Activation of p38 stress-activated protein kinase during Rickettsia rickettsii infection of human endothelial cells: role in the induction of chemokine response

Rickettsia rickettsii, a Gram-negative and obligate intracellular bacterium, preferentially infects the vascular endothelium during human infections leading to inflammation and dysfunction. The aim of this study was to determine whether R. rickettsii infection of endothelial cells (EC) activates p38 and/or c-jun N-terminal kinases (JNK) mitogen-activated protein (MAP) kinase, key regulatory proteins that control the response to inflammatory stimuli. We show that infection of cultured human EC results in the dose-dependent activation of p38, as assessed by increased phosphorylation and activity, without affecting the status of JNK. Rickettsia inactivation by heat or formaldehyde abolished the activation of p38 kinase and inhibition of cellular invasion by infection at low temperature, pre-treatment of host EC with cytochalasin D, or pre-incubation of rickettsiae with an irreversible phospholipase inhibitor led to a diminished p38 phosphorylation, suggesting requirement of invasion by viable rickettsiae for this host cell response. SB 203580, a p38-specific inhibitor, had no effect on infection-induced activation of the ubiquitous transcriptional regulator nuclear factor-kappa B, but effectively reduced the expression and secretion of important chemoattractant cytokines interleukin (IL)-8 and monocyte chemoattractant protein (MCP)-1 by R. rickettsii-infected EC. Selective inhibition of p38 activity may be exploited as an anti-inflammatory target to prevent rickettsial vasculitis and to develop new and improved chemotherapeutic agents.

Multispacer typing of Rickettsia prowazekii enabling epidemiological studies of epidemic typhus

Currently, there is no tool for typing Rickettsia prowazekii, the causative agent of epidemic typhus, currently considered a potential bioterrorism agent, at the strain level. To test if the multispacer typing (MST) method could differentiate strains of R. prowazekii, we amplified and sequenced the 25 most variable intergenic spacers between the R. prowazekii and R. conorii genomes in five strains and 10 body louse amplicons of R. prowazekii from various geographic origins. Two intergenic spacers, i.e., rpmE/tRNA(fMet) and serS/virB4, were variable among tested R. prowazekii isolates and allowed identification of three and two genotypes, respectively. When the genotypes obtained from the two spacers were combined, we identified four different genotypes. MST demonstrated that several R. prowazekii strains circulated in human body lice during an outbreak of epidemic typhus in Burundi. This may help to discriminate between natural and intentional outbreaks. Our study supports the usefulness of MST as a versatile method for rickettsial strain genotyping.

Bacterial zoonoses and infective endocarditis, Algeria

Blood culture–negative endocarditis is common in Algeria. We describe the etiology of infective endocarditis in this country. Samples from 110 cases in 108 patients were collected in Algiers. Blood cultures were performed in Algeria. Serologic and molecular analysis of valves was performed in France. Infective endocarditis was classified as definite in 77 cases and possible in 33. Causative agents were detected by blood cultures in 48 cases. All 62 blood culture–negative endocarditis cases were tested by serologic or molecular methods or both. Of these, 34 tested negative and 28 had an etiologic agent identified. A total of 18 infective endocarditis cases were caused by zoonotic and arthropodborne bacteria, including Bartonella quintana (14 cases), Brucella melitensis (2 cases), and Coxiella burnetii (2 cases). Our data underline the high prevalence of infective endocarditis caused by Bartonella quintana in northern Africa and the role of serologic and molecular tools for the diagnosis of blood culture–negative endocarditis.

Enfermedades producidas por Rickettsia

Species of the genus Rickettsia are small, obligate intracelular, gramnegative bacteria, many of which are considered nowadays a paradigm of emergent pathogens. With the exception of R. prowazekii, they are maintained in the natural environment through a cycle involving different hosts (mainly mammals), and arthropod vectors (in general ticks, and fleas); humans are affected only by incidental transmission due to arthropod bites. The common pathogenesis of these diseases lie on the predominantly infection of endotelial cells, that determines the development of multisistemic small vessel vasculitis, which may affect lungs (interstitial pneumonitis), heart (miopericarditis), skin (rash), central nervous system (meningoencephalitis), as well as liver, and kidneys. They are classified in two groups: spotted-fever group, and typhus group rickettsia. In Spain the most prevalent rickettsioses of both groups are mediterranean spotted fever (caused by R. conorii), and murine typhus (caused by R. typhi), respectively. This review focuses mainly in these two diseases, and also in other rickettsioses of interest due to their recently emergence or reemergence (R. slovaca, R. africae, R. prowazekii, R. felis), or to their high incidence in other areas (R. rickettsii, Orientia tsutsugamushi).