[Progress in research of epidemiology of relapsing fever and prevention and control measures].

Relapsing fever, caused by Borreliae of the relapsing fever groups, is an infectious disease, which would cause spirochaetaemia and repeated fever in human. To comprehensively understand the classification and distribution of relapsing fever, as well as correlated factors, this paper summarizes the progress in research of epidemiology of relapsing fever in the world, and suggests prevention and control measures. The disease is heterogenous and can be divided into three groups according to vectors, i.e. tick-borne relapsing fever, louse-borne relapsing fever and the avian relapsing fever. Tick borne relapsing fever can be further divided into two types: soft tick transmission and hard tick transmission. Soft tick-borne relapsing fever generally has obvious geographical distribution characteristics, while hard tick-borne relapsing fever is widely distributed all over the world. Louse-borne relapsing fever, also known as epidemic forms of relapsing fever, is caused by body lice, and the incidence is usually associated with war, famine, refugees and poor sanitation. The prevention and control of relapsing fever should be based on local conditions.

Single Dose of Doxycycline for the Prevention of Tick-borne Relapsing Fever.

The current postexposure prophylaxis regimen for tick-borne relapsing fever (TBRF) consists of 5 days' doxycycline. In this observational study of 77 spelunkers at high risk for TBRF, a single dose of 100 mg doxycycline taken up to 72 hours after exposure to ticks was 100% effective in preventing the disease.

Outbreak of Louse-Borne Relapsing Fever among Urban Dwellers in Arsi Zone, Central Ethiopia, from July to November 2016.

We report epidemiological and clinical aspects of an outbreak of louse-borne relapsing fever (LBRF) in Asella in Arsi Zone, central Ethiopia, from July to November 2016. A total of 63 LBRF cases were reported. The overall case fatality rate was 13% among treated patients. In this article, the first-line epidemiological assessment, individual prevention and control measures, and public health investigations and interventions in relation to this outbreak are described. Treatment recommendations for resource-limited settings are discussed by review of the latest literature.

An Alternative Strategy of Preventive Control of Tick-Borne Relapsing Fever in Rural Areas of Sine-Saloum, Senegal.

In Senegal, tick-borne relapsing fever (TBRF) is a major cause of morbidity and a neglected public health problem. Borreliosis cases commonly detected in two villages led us to implement a borreliosis preventive control including cementing of floors in bedrooms and outbuildings attended by inhabitants to avoid human contacts with tick vectors. Epidemiological and medical monitoring of the TBRF incidence was carried out at Dielmo and Ndiop by testing the blood of febrile patients since 1990 and 1993, respectively. Intra-domiciliary habitat conditions were improved by cementing, coupled with accompanying measures, from March 2013 to September 2015. Application of this strategy was associated with a significant reduction of borreliosis incidence. This was more evident in Dielmo, dropping from 10.55 to 2.63 cases per 100 person-years (P < 0.001), than in Ndiop where it changed from 3.79 to 1.39 cases per 100 person-years (P < 0.001). Thirty-six cases of TBRF were estimated to be prevented at a cost of €526 per infection. The preventive control strategy was successful in Dielmo and Ndiop, being associated with decreased incidence by 89.8% and 81.5%, respectively, suggesting that TBRF may be widely decreased when the population is involved. Public health authorities or any development stakeholders should adopt this effective tool for promoting rural health through national prevention programs.

Borrelia miyamotoi: a widespread tick-borne relapsing fever spirochete.

Borrelia miyamotoi is a relapsing fever spirochete that has only recently been identified as a human pathogen. Borrelia miyamotoi is genetically and ecologically distinct from Borrelia burgdorferi sensu lato, while both are present in Ixodes ticks. Over 50 patients with an acute febrile illness have been described with a B. miyamotoi infection, and two infected immunocompromised patients developed a meningoencephalitis. Seroprevalence studies indicate exposure in the general population and in specific risk groups, such as patients initially suspected of having human granulocytic anaplasmosis. Here, we review the available literature on B. miyamotoi, describing its presence in ticks, reservoir hosts, and humans, and discussing its potential impact on public health.

Development of vaccines against Ornithodoros soft ticks: An update.

Ticks are parasites of great medical and veterinary importance since they are vectors of numerous pathogens that affect humans, livestock and pets. Among the argasids, several species of the genus Ornithodoros transmit serious diseases such as tick-borne human relapsing fever (TBRF) and African Swine Fever (ASF). In particular, Ornithodoros erraticus is the main vector of these two diseases in the Mediterranean while O. moubata is the main vector in Africa. The presence of these Ornithodoros ticks in domestic and peridomestic environments may greatly hinder the eradication of TBRF and ASF from endemic areas. In addition, there is a constant threat of reintroduction and spreading of ASF into countries from where it has been eradicated (Spain and Portugal) or where it was never present (the Caucasus, Russia and Eastern Europe). In these countries, the presence of Ornithodoros vectors could have a tremendous impact on ASF transmission and long-term maintenance. Therefore, elimination of these ticks from at least synanthropic environments would contribute heavily to the prevention and control of the diseases they transmit. Tick control is a difficult task and although several methods for such control have been used, none of them has been fully effective against all ticks and the problems they cause. Nevertheless, immunological control using anti-tick vaccines offers an attractive alternative to the traditional use of acaricides. The aim of the present paper is to offer a brief overview of the current status in control measure development for Ornithodoros soft ticks, paying special attention to the development of vaccines against O. erraticus and O. moubata. Thus, our contribution includes an analysis of the chief attributes that the ideal antigens for an anti-tick vaccine should have, an exhaustive compilation and analysis of the scant anti-soft tick vaccine trials carried out to date using both concealed and salivary antigens and, finally, a brief description of the new reverse vaccinology approaches currently used to identify new and more effective protective tick antigens.

Postexposure prophylaxis of tick-borne relapsing fever: lessons learned from recent outbreaks in Israel.

Tick-borne relapsing fever (TBRF) is endemic in Israel. Military activities pose a particular risk for TBRF, and its prevention is based on heightened awareness and risk stratification by active surveillance of tick bites and selective postexposure prophylaxis (PEP) with doxycycline for tick-bitten individuals. We report three outbreaks of TBRF affecting 35 exposed military personnel, with an average recognized tick bite rate of approximately 50% and an attack rate of 25-50%. Of 10 TBRF cases, 20% had no evidence of tick bites and thus restriction of PEP administration to individuals with recognized tick bites contributed to TBRF occurrence. As a result of a revised policy, 24 soldiers (including eight with recognized and 16 with unrecognized tick bites) received antimicrobials following the diagnosis of TBRF among their cohorts, and none of these individuals subsequently developed TBRF. The probability for TBRF among exposed individuals associated with well-established cases of TBRF warrants that prompt doxycycline administration be considered in all individuals who share risk factors, regardless of tick bite status.

Relapsing fever--a forgotten disease revealed.

Borrelial relapsing fever was once a major worldwide epidemic disease that made a significant impact on Livingstone during his epic travels through Africa and throughout Europe. Indeed, the term 'relapsing fever' was first used to describe clinical cases of this disease in Edinburgh. During the last century, we have witnessed the demise of the louse-borne infection, largely through improving standards of living resulting in a reduction in body lice, the vector for Borrelia recurrentis [louse-borne relapsing fever (LBRF)]. The tick-borne zoonotic form of the disease persists in endemic foci around the world [tick-borne relapsing fever (TBRF)]. Indeed, TBRF is reportedly the most common bacterial infection from Senegal and listed within the top ten causes of mortality in children under five in Tanzania. In Ethiopia, LBRF is again within the top ten causes of hospital admission, associated with significant morbidity and mortality. Despite these figures, many now regard relapsing fever as an unusual tropical disease. Certainly, recent cases have been imported following travel from endemic zones. More surprisingly, cases have been reported following family reunions in Colorado, USA. A further case was reported from the Mt Wilson observatory in Los Angeles, USA. In many regions, the infection is zoonotic with natural reservoirs in several vertebrate species. In West Africa, infection is again primarily zoonotic. Whether those species found predominantly in East Africa are zoonoses or are infections of humans alone is still debated, however, the life cycle may be determined by the feeding preferences of their arthropod vectors.

Post exposure prophylaxis of tick-borne relapsing fever.

Tick-borne relapsing fever (TBRF) is endemic to Israel. Since 2004, the Israel Defence Forces (IDF) has mandated the prophylaxis of tick-bitten subjects with a five-day doxycycline course. We examined the safety and effectiveness of this policy in preventing TBRF. We analyzed the records from January 2004 to January 2007, and identified all reported events of tick bites or TBRF cases. Data were available on 27 events in which 816 soldiers have undergone physical examination following exposure, and seven TBRF cases were recorded in this group-an attack rate of 0.86% compared with the expected rate of 5.34% from previous army data (relative risk [RR] = 0.16). Of those screened, 128 (15.7%) had tick-bite and were intended for prophylaxis, of which four TBRF cases occurred-3.13% attack rate compared with an expected rate of 38.4% in these bitten individuals without prophylaxis (RR = 0.08, number needed to treat = 3). In all cases in which screening and prophylaxis were provided within 48 h of tick bite, complete prevention of TBRF was achieved. No cases of Jarisch-Herxheimer reaction (JHR) was recorded. Tick-bite screening and prophylactic treatment with doxycycline in endemic areas is a practical, safe, and highly effective policy for preventing TBRF.

Tick-borne relapsing fever in a new highland endemic focus of western Iran.

Tick-borne relapsing fever (TBRF) is a neglected zoonotic disease caused by infection with spirochaetes of the genus Borrelia. Humans usually contract it from the bite of infected soft ticks of the genus Ornithodoros. In Iran, where the disease is endemic in the mountainous north-western provinces, reports of over 200 cases annually probably under-estimate the true incidence. The species, distribution and infection of ticks that are potential vectors of Borrelia and the clinical and epidemiological characteristics of the local TBRF cases were recently investigated in the villages in and around the county town of Bijar, in north-western Iran. A blood sample from each suspected case of TBRF was checked for B. persica by dark-field microscopy, data were collected on the demographics and clinical manifestations of each confirmed case, and the prevalence of tick infection with borreliae and the monthly incidence of TBRF were evaluated. Between 2000 and 2007, 148 cases of TBRF (each with fever, chills and headache) were passively detected in the town. Most (115) of these were confirmed by microscopy, with the other subjects categorized as probable (21) or suspected cases (12) of TBRF. Most (91%) of the 148 subjects were young people, and most came from rural areas and lived in large households in the old mud-and-thatch houses of Bijar. Most (82%) of the cases occurred during the summer or early autumn. Overall, 8543 soft ticks (Ornithodoros tholozani, O. lahorensis, Argas persicus and A. reflexus) were collected by clustered random sampling. When a random sample of the O. tholozani ticks (96 of the 577 collected) was checked for B. persica infection, by being crushed and then inoculated intraperitoneally into a mouse or suckling Syrian hamster, 19 were found infected. Peaks in the monthly incidence of TBRF occurred as the numbers of O. tholozani in the tick collections peaked, and it seems likely that most of the cases were caused by B. persica transmitted by O. tholozani. Further studies in Iran, to map the geographical variation in the prevalence of soft-tick infection with Borrelia and identify any Borrelia reservoirs, are recommended.

Current issues in relapsing fever.

PURPOSE OF REVIEW: Relapsing fever has the highest incidence of any bacterial disease in Africa and a massive epidemic potential due to current political turmoil in the Horn of Africa. This review focuses on recent advances in diagnostics, molecular biology and host-pathogen interactions. RECENT FINDINGS: Complete relapsing fever genomes have recently been published, and the first site-specific genetic knockout complementation has been performed. Relapsing fever has gone from being a neglected disease to garnering interest in aspects such as tissue invasion, membrane biochemistry and complement evasion. Relapsing fever symptoms are variable, and the disease is commonly misdiagnosed as, for example, malaria. Although relapsing fever is considered a transient disease, it persists as a residual infection in the brain, which can be reactivated on immunosuppression. Therefore, single-dose antibiotic treatment should be avoided. Instead, treatment should cover a longer period, similar to the recommended regime for Lyme disease. Relapsing fever is a common cause of pregnancy complications such as intrauterine growth retardation and placental damage with spirochaetes crossing the maternal-foetal barrier, resulting in congenital infection. SUMMARY: Although relapsing fever remains a big problem, recently described host-pathogen interactions, diagnostics and molecular biology advances such as completed genome sequences and the dawn of genetic tools have brought relapsing fever research into the 21st century.

Tick talk: unusually severe case of tick-borne relapsing fever with acute respiratory distress syndrome--case report and review of the literature.

Borrelia hermsii causes tick-borne relapsing fever (TBRF) in the Pacific Northwest. There are few reports of TBRF-associated acute respiratory distress syndrome. One such unusually severe case is described. Literature is reviewed including diagnosis, treatment, and prevention.

Community knowledge, attitudes and practices related to tick-borne relapsing fever in dodoma rural district, central Tanzania.

Tick-borne Relapsing Fever (TBRF) is a vector-borne disease of humans which causes serious illness, primarily for children under five years old and pregnant women. Understanding people's knowledge, attitude and practices on the disease is important in designing appropriate interventions. This study was conducted to explore community knowledge, attitudes and practices regarding TBRF transmission and control to provide baseline data for the planned scaling up of intervention in Dodoma rural District in central Tanzania. A total of 198 heads of households were interviewed using a semi-structured questionnaire. Of these, 94.5% were aware of TBRF. Fever of unknown origin (69.5%), body pain (8.5%), headache (8.5%), chills (4.5%) and vomiting (3.5%) were the most commonly mentioned symptoms. The domestic tick-infestation and tick-bites was known to 82.8%. High domestic tick infestation reported to occur during dry season (85.4%). The majority believed that the disease spreads through tick-bites (85.9%). Regular plastering of house floors and walls was the most common method used by the community to control domestic tick infestation (96.5 %). Majority (84.3%) of the respondents preferred public healthcare facilities for treatment. Only a small proportion (15.7%) preferred using traditional medicines. Poor knowledge of the study subjects about the disease and its control underscores the need for health educational campaigns if any control and/or elimination programme is to succeed.

Postexposure treatment with doxycycline for the prevention of tick-borne relapsing fever.

BACKGROUND: Tick-borne relapsing fever (TBRF) is an acute febrile illness. In Israel, TBRF is caused by Borrelia persica and is transmitted by Ornithodoros tholozani ticks. We examined the safety and efficacy of postexposure treatment to prevent TBRF. METHODS: In a double-blind, placebo-controlled trial, 93 healthy subjects with suspected tick exposure (52 with signs of tick bites and 41 close contacts--those without signs but with a similar risk of contact with ticks) were randomly assigned to receive either doxycycline (Dexxon, in a dose of 200 mg the first day and then 100 mg per day for four days) or placebo after presumed exposure to TBRF. Cases of TBRF were defined by fever and a positive blood smear. Serologic analysis for cross-reactivity to Borrelia burgdorferi and polymerase chain reaction (PCR) for the borrelia glpQ gene were also performed. RESULTS: After randomization, 47 subjects (26 with signs of tick bites and 21 close contacts) received doxycycline. Forty-six other subjects (26 with signs of tick bites and 20 close contacts) received placebo. All 10 cases of TBRF identified by a positive blood smear were in the placebo group of subjects with signs of a tick bite (P<0.001). These findings suggested a 100 percent efficacy of preemptive treatment (95 percent confidence interval, 46 to 100 percent). PCR for the borrelia glpQ gene was negative at baseline for all subjects and subsequently positive in all subjects with fever and a positive blood smear. Seroconversion was detected in eight of nine cases of TBRF. PCR and serum samples were negative for all of the other subjects tested. No major treatment-associated adverse effects were identified. CONCLUSIONS: Treatment with doxycycline is safe and efficacious in preventing TBRF after suspected exposure to ticks in a high-risk environment. (ClinicalTrials.gov number, NCT00237016 [ClinicalTrials.gov].).

[Tick-borne human pathogenic microorganisms found in Europe and those considered nonpathogenic. Part II: Bacteria, parasites and mixed infections]. / Durch Zecken übertragene humanpathogene und bisher als apathogen geltende Mikroorganismen in Europa. Teil II: Bakterien, Parasiten und Mischinfektionen.

The importance of tick-borne diseases has significantly increased objectively and subjectively during the last few years. This fact was demonstrated by the description of tick-borne viruses, in particular with respect to tickborne encephalitis published in part I. Here in part II, tick-borne bacteria and parasites will be discussed as well the significance of these agents, their vectors, clinical course, diagnostics, prophylaxis, and therapy. Naturally, Lyme borreliosis, one of the most important tick-borne bacterial illnesses of humans, is the center of our interest. In addition to basic understanding, critical practice-relevant advice regarding all agents is presented. Similarly all tick-borne bacterial diseases such as relapsing fever, tularemia, ehrlichiosis, and rickettsiosis including Q fever will be discussed. Tick-borne zoonotic babesiae are parasites whose veterinary importance has been known for the last 100 years but whose relevance for human medicine only became evident in 1957. The fact that multiple and mixed infections caused by ticks are possible has been known for years. Taking into account such a high prevalence of the infectious agents in ticks, such multiple infections were to be expected. During the last few years it has become evident that double and multiple infections of humans caused by tick bites occur far more frequently than has been known so far. As a result, in cases of unclear anamnesis,new diagnostic and therapeutic approaches should be taken. In general one can say that considerable additional scientific research is necessary to effectively reduce the incidence of tick-borne diseases.

Generation of a complement-independent bactericidal IgM against a relapsing fever Borrelia.

The spirochetemia of relapsing fever in mice is cleared by a complement-independent, polyclonal IgM response with reactivity to two prominent Ags of 20 and 35 kDa. In this study, we have dissected the polyclonal IgM Ab response against a relapsing fever spirochete to determine the specificity of its complement-independent bactericidal properties. Our experimental approach selectively generated an IgM murine mAb from the early specific immune response to a variable outer membrane protein. This IgM is bactericidal in the absence of complement and is part of the polyclonal Ab response that mediates the clearance of this bacterium from the blood. Purified monoclonal IgM caused direct structural damage to the outer membrane of the spirochete, in the absence of complement, and protected both B cell- and C5-deficient mice from challenge when administered passively. The direct, complement-independent, bactericidal activity of Abs is a critical mechanism of host defense against infection.