Murine typhus in Cyprus: 21 paediatric cases

Vaccine Design and Vaccination Strategies against Rickettsiae

Rickettsioses are febrile, potentially lethal infectious diseases that are a serious health threat, especially in poor income countries. The causative agents are small obligate intracellular bacteria, rickettsiae. Rickettsial infections are emerging worldwide with increasing incidence and geographic distribution. Nonetheless, these infections are clearly underdiagnosed because methods of diagnosis are still limited and often not available. Another problem is that the bacteria respond to only a few antibiotics, so delayed or wrong antibiotic treatment often leads to a more severe outcome of the disease. In addition to that, the development of antibiotic resistance is a serious threat because alternative antibiotics are missing. For these reasons, prophylactic vaccines against rickettsiae are urgently needed. In the past years, knowledge about protective immunity against rickettsiae and immunogenic determinants has been increasing and provides a basis for vaccine development against these bacterial pathogens. This review provides an overview of experimental vaccination approaches against rickettsial infections and perspectives on vaccination strategies.

GroEL is an immunodominant surface-exposed antigen of Rickettsia typhi

Rickettsioses are neglected and emerging potentially fatal febrile diseases that are caused by obligate intracellular bacteria, rickettsiae. Rickettsia (R.) typhi and R. prowazekii constitute the typhus group (TG) of rickettsiae and are the causative agents of endemic and epidemic typhus, respectively. We recently generated a monoclonal antibody (BNI52) against R. typhi. Characterization of BNI52 revealed that it specifically recognizes TG rickettsiae but not the members of the spotted fever group (SFG) rickettsiae. We further show that BNI52 binds to protein fragments of ±30 kDa that are exposed on the bacterial surface and also present in the periplasmic space. These protein fragments apparently derive from the cytosolic GroEL protein of R. typhi and are also recognized by antibodies in the sera from patients and infected mice. Furthermore, BNI52 opsonizes the bacteria for the uptake by antigen presenting cells (APC), indicating a contribution of GroEL-specific antibodies to protective immunity. Finally, it is interesting that the GroEL protein belongs to 32 proteins that are differentially downregulated by R. typhi after passage through immunodeficient BALB/c CB17 SCID mice. This could be a hint that the rickettsia GroEL protein may have immunomodulatory properties as shown for the homologous protein from several other bacteria, too. Overall, the results of this study provide evidence that GroEL represents an immunodominant antigen of TG rickettsiae that is recognized by the humoral immune response against these pathogens and that may be interesting as a vaccine candidate. Apart from that, the BNI52 antibody represents a new tool for specific detection of TG rickettsiae in various diagnostic and experimental setups.

Selection of Diagnostic Cutoffs for Murine Typhus IgM and IgG Immunofluorescence Assay: A Systematic Review

Murine typhus is a neglected but widespread infectious disease that results in acute fever. The immunofluorescence assay (IFA) is the "gold standard" to identify IgM or IgG antibodies, although there is a lack of standardization in methodologies. The objective of this review is to summarize 1) the differences in published methodologies, 2) the diagnostic cutoff titers, and 3) the justification of diagnostic cutoffs. Searches were performed by combining the following search terms: "murine typhus," "rickettsia typhi," "immunofluorescence," "IFA," and "serologic" with restrictions (i.e., "rickettsia typhi" or "murine typhus," and "IFA" or "immunofluorescence," or "serologic*"). The search identified 78 studies that used IFA or immunoperoxidase assay (IIP) antibody cutoffs to diagnose murine typhus, 39 of which were case series. Overall, 45 studies (57.7%) provided little to no rationale as to how the cutoff was derived. Variation was seen locally in the cutoff titers used, but a 4-fold or greater increase was often applied. The cutoffs varied depending on the antibody target. No consensus was observed in establishing a cutoff, or for a single-value diagnostic cutoff. In conclusion, there is a lack of consensus in the establishment of a single-value cutoff. Further studies will need to be executed at each distinct geographic location to identify region-specific cutoffs, while also considering background antibody levels to distinguish between healthy and infected patients.

Murine Typhus in South Texas Children: An 18-year Review

BACKGROUND

Murine typhus is a zoonotic infection caused by Rickettsia typhi that remains endemic in South Texas. In 2003, only 9 Texas counties reported murine typhus compared with 41 counties in 2013.

METHODS

A retrospective study of children discharged with a confirmed diagnosis of murine typhus from Driscoll Children's Hospital between January 1998 and September 2016.

RESULTS

Two hundred thirteen children (113 female) 3 months through 19 years of age (mean, 11.2 ± 4.5 years) were identified. Cases occurred throughout the year. Children were admitted after a mean of 7.7 ± 5.3 days of fever. The most common symptoms were fever (100%), poor appetite (71.9%), malaise/fatigue (69.0%) and headache (67.6%). The most common laboratory abnormalities were elevated C-reactive protein, hypoalbuminemia, elevated erythrocyte sedimentation rate, elevated transaminases and elevated band count with normal total white blood cell count. Children defervesced in a mean of 31.87 ± 21.36 hours after initiation of doxycycline. Hospitalization lasted for a mean of 2.7 ± 1.8 days when children were administered doxycycline within 24 hours of admission compared with, 4.1 ± 1.8 days, P ≤ 0.0001 when started later. Eleven patients (5.1%) were admitted to the pediatric intensive care unit and were older, P = 0.0009. No children died.

CONCLUSIONS

Murine typhus is endemic in South Texas. Children who were treated earlier with doxycycline had a shorter hospitalization than were those who began therapy later. Recognition of murine typhus is important to prevent delay in treatment and development of complications.

Murine Typhus with Marked Thrombocytopenia in a Child in Northern Greece and Literature Review

We report a case of murine typhus in a 4-year-old boy living in northern Greece. Although the illness started with mild symptoms, a maculopapular rash appeared by the end of the first week of illness followed by marked thrombocytopenia. The detection of IgM antibodies against Rickettsia typhi in the patient's blood and a positive polymerase chain reaction result combined with sequencing confirmed the diagnosis of infection by Rickettsia typhi. Clinicians in northern Greece should be aware of the disease, even in cases presenting with no specific initial symptoms.

Clinical and laboratory characteristics, epidemiology, and outcomes of murine typhus: A systematic review

Murine or endemic typhus, a febrile disease caused by Rickettsia typhi, is often misdiagnosed due to its non-specific presentation. We sought to evaluate all available evidence in the literature regarding the clinical and laboratory manifestations, epidemiological characteristics, and outcomes of murine typhus. Pubmed was searched for all articles providing available data. In an effort to incorporate contemporary data, only studies from 1980 were included. Thirty-three case series including 2074 patients were included in final analysis. Available evidence suggests that the classic triad of fever, headache and rash is encountered in only one-third of patients. Other frequent symptoms were chills, malaise, myalgia, and anorexia. A tetrad of reported laboratory abnormalities consisting of elevated liver enzymes, lactate dehydrogenase, erythrocyte sedimentation rate and hypoalbuminemia was detected. Complications were observed in one-fourth of patients, reported mortality was extremely low, but untreated patients had notably longer duration of fever. Among epidemiological characteristics, a seasonal distribution with most cases reported during warmer months, was the most prominent finding. Murine typhus in children exhibits several different characteristics, with abdominal pain, diarrhea, and sore throat reported more commonly, higher frequency of anemia, lower frequency of hypoalbuminemia, hematuria and proteinuria and a much lower rate of complications. This systematic review of published evidence provides a thorough description of the clinical and laboratory features of murine typhus and highlights important differences in children.

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.

Comparative evaluation of two Rickettsia typhi-specific quantitative real-time PCRs for research and diagnostic purposes

Rickettsioses are caused by intracellular bacteria of the family of Rickettsiaceae. Rickettsia (R.) typhi is the causative agent of endemic typhus. The disease occurs worldwide and is one of the most prevalent rickettsioses. Rickettsial diseases, however, are generally underdiagnosed which is mainly due to the lack of sensitive and specific methods. In addition, methods for quantitative detection of the bacteria for research purposes are rare. We established two qPCRs for the detection of R. typhi by amplification of the outer membrane protein B (ompB) and parvulin-type PPIase (prsA) genes. Both qPCRs are specific and exclusively recognize R. typhi but no other rickettsiae including the closest relative, R. prowazekii. The prsA-based qPCR revealed to be much more sensitive than the amplification of ompB and provided highly reproducible results in the detection of R. typhi in organs of infected mice. Furthermore, as a nested PCR the prsA qPCR was applicable for the detection of R. typhi in human blood samples. Collectively, the prsA-based qPCR represents a reliable method for the quantitative detection of R. typhi for research purposes and is a promising candidate for differential diagnosis.

Identification of a novel uncultured Rickettsia species strain (Rickettsia species strain Tselenti) in Cyprus

In a previous study conducted in Cyprus, various spotted fever group Rickettsia species were detected and identified in ticks by molecular analysis. Among them, a partially characterized Rickettsia species was detected in Hyalomma anatolicum excavatum and Rhipicephalus turanicus ticks. We report characterization of this rickettsial strain by using polymerase chain reaction sequencing analysis of partial citrate synthase A, outer membrane protein A, outer membrane protein B, and 17-kD protein genes. We propose a provisional name Rickettsia sp. strain Tselenti for this strain until it is isolated and further characterized.

Murine typhus in Cyprus: a 9-year survey

Epidemiological and clinical data of 193 human cases of murine typhus in Cyprus were recorded and analysed during a 9-year period (2000-2008). The incidence rate was estimated at 24.5 cases/100,000 population/year. The incidence rate varied considerably between rural, urban and semi-urban areas, with residents in rural areas accounting for 79.3% of the total cases. Most (72.5%) of the cases occurred in late summer (July and August) and early autumn (September to October) with a peak in September. Well-established persistent endemic foci with clusters of cases were identified and characterised as 'high risk' areas. Presence of or contact with rats and fleas, presence of domestic/peridomestic animals and residence in rural areas, especially locations near the 'green line' (a narrow zone patrolled by UN forces that separates the northern and southern parts of the island), increased the possibility of murine typhus infection. The results of the current study enhance the belief that murine typhus is a serious public health problem in Cyprus.

Murine typhus in the homeless

Homeless populations are particularly exposed to many vector-borne diseases because of their poor living conditions. We tested sera from 299 homeless people recruited in 2010 and 2011 in Marseilles, France for antibodies to Rickettsia typhi by microimmunofluorescence using a titer of 1:25 as a cut-off titer, and we confirmed the results by Western blot and cross-adsorption studies. Sixty-three persons (22%) had antibodies against R. typhi. The murine typhus seroprevalence rates have significantly increased in homeless populations between the 2000-2003 and 2010-2011 periods. These findings indicate that the homeless are increasingly exposed to flea-borne murine typhus in Marseilles. One might suggest that multiple strikes of sanitation workers resulting in the increase of waste and construction sites combined with the poor living conditions of the homeless expose this population to rodents and their fleas. Further annual studies are necessary to follow rodent-associated diseases among homeless people in Marseille.

Rickettsia typhi and Rickettsia felis in Xenopsylla cheopis and Leptopsylla segnis parasitizing rats in Cyprus

Fleas collected from rats during a three-year period (2000-2003) in 51 areas of all provinces of Cyprus were tested by molecular analysis to characterize the prevalence and identity of fleaborne rickettsiae. Rickettsia typhi, the causative agent of murine typhus, was detected in Xenopsylla cheopis (4%) and in Leptopsylla segnis (6.6%). Rickettsia felis was detected in X. cheopis (1%). This is the first report of R. typhi in X. cheopis and L. segnis from rats, in Cyprus, and the first report of R. felis in X. cheopis in Europe. The role of fleas (mainly X. cheopis) was confirmed in the epidemiologic cycle of murine typhus in Cyprus by interrelation of current results with those of previous studies. The geographic distribution of fleas coincided with the geographic distribution of the pathogen they can harbor, which emphasizes the potential risk of flea-transmitted infections in Cyprus.

Rats as indicators of the presence and dispersal of six zoonotic microbial agents in Cyprus, an island ecosystem: a seroepidemiological study

A total of 622 rats (402 Rattus norvegicus and 220 R. rattus frugivorus) were collected in 51 different areas in Cyprus during 2000-2003 and used as indicators of the presence and dispersal of six zoonotic microbial agents. IgG antibodies against Rickettsia typhi (241/496, 48.6%), R. conorii (209/500, 41.8%), Toxoplasma sp. (138/494, 27.9%), Coxiella burnetti (63/494, 12.8%), Bartonella henselae (52/494, 10.5%) and Leishmania infantum (36/494, 7.3%) were detected by indirect immunofluorescence test. There was variation in the association between the seropositivity of the six microbial agents and other factors. Rat species affected R. typhi and R. conorii seropositivity, the prefecture where the rats were caught affected R. typhi, C. burnetii, B. henselae, T. gondii and L. infantum, the sampling season impacted on R. typhi, R. conorii, T. gondii and L. infantum, and the flea species affected R. typhi, R. conorii and B. henselae. These results were analysed using geographical information system (GIS) technology and the seropositivity in rats against the pathogens tested appeared to follow the occurrence of these pathogens in humans. This suggests that rats could be used as disease sentinels and, together with GIS technology, they could be a useful tool for the identification of endemic foci and high-risk areas for each pathogen.

Murine typhus as a cause of Fever in travelers from Tunisia and mediterranean areas

BACKGROUND

Travelers are exposed to a variety of health risks in unfamiliar environments and fever is a common problem in patients returning from travel abroad. Rickettsial diseases are increasingly frequently being reported among international travelers. Here we present cases of Rickettsia typhi infection, the agent of murine typhus, that were identified in our laboratory the last year, in travelers from Tunisia.

METHODS

For each patient we tested an acute-phase serum sample and for one patient we tested a convalescent-phase serum sample. IgG and IgM antibody titers were estimated with use of the microimmunofluorescence (MIF) assay. Western blot (WB) assay was performed for all the patients.

RESULTS

We identified three cases of murine typhus after a travel in Tunisia. All cases were observed during late summer and early autumn and patients were suffering by persistent fever. None of them presented rash or inoculation eschar. MIF was positive for Rickettsia sp. in the acute-phase serum samples of two patients. In one patient, two acute-phase serum samples were Rickettsia sp. negative whereas a third convalescent-phase serum sample that was obtained 2 weeks after was Rickettsia sp. positive. By WB assay we identified infection by R typhi. A treatment was immediately started and patients became apyretic.

CONCLUSIONS

In the countries of North Europe, although autochthones cases of murine typhus have not been described, sporadic cases of R typhi infection are identified in travelers who visited murine typhus endemic areas. Murine typhus should be considered in the diagnosis of febrile illness without rash in travelers returning from disease endemic areas, like the south Mediterranean area.

Intervening to reduce inequalities in infections in Europe

The European Centre for Disease Prevention and Control was founded in response to newly emerging infections such as severe acute respiratory syndrome and avian influenza. However, Europe faces other communicable disease challenges that have proven to be remarkably resilient to public health interventions. We present examples of communicable diseases with inequitable distribution among those with poor educational attainment, low income, or other socioeconomic factors in every European country. Because these findings are incompatible with social justice and fairness, we examine strategic interventions targeting upstream causes of communicable disease transmission keeping in mind 10 indispensable public health functions essential to reach marginalized groups. These interventions have to be tailored to the socio-political context and rely on community-based decision-making and intersectorial collaboration.

Fever of unknown origin in the returning traveler

The returning traveler with fever presents a diagnostic challenge for the health care provider. When evaluating such a patient, the highest priority should be given to diseases that are potentially fatal or may represent public health threats. A good history is paramount and needs to include destination, time and duration of travel, type of activity, onset of fever in relation to travel, associated comorbidities, and any associated symptoms. Pretravel immunizations and chemoprophylaxis may alter the natural course of disease and should be inquired about specifically. The fever pattern, presence of a rash or eschar, organomegaly, or neurologic findings are helpful physical findings. Laboratory abnormalities are nonspecific but when corroborated with clinical and epidemiologic data may offer a clue to diagnosis.