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Outbreak of tick-borne relapsing fever at the north rim of the Grand Canyon: evidence for effectiveness of preventive measures.

An outbreak of tick-borne relapsing fever (TBRF) originating at the North Rim of Grand Canyon National Park was investigated in 1990. To determine risk factors for the disease, almost 7,000 parties of visitors were surveyed; over half responded, representing > 10,000 people. Fifteen cases of confirmed or probable TBRF were identified in visitors and 2 in employees. All patients except one experienced symptoms after overnight stays in a group of cabins that had not been rodent-proofed after a TBRF outbreak in 1973 (relative risk for visitors [RR] 8.2, 95% confidence interval [CI] 1.1-62). Seven cases of TBRF were associated with a single cabin (RR 98, 95% CI 30-219). Structural flaws and rodent nests were common in the implicated cabins and rare in unaffected cabins. This investigation suggests that measures to rodent-proof cabins at sites where TBRF is endemic prevent reinfestation of cabins by infected rodents and tick vectors, thereby preventing the spread of disease in humans.

Adolescent↗

Experimental louse-borne relapsing fever in the grivet monkey, Cercopithecus aethiops. I. Clinical course.

Fifteen grivet monkeys, Cercopithecus aethiops, were infected with an Ethiopian strain of Borrelia recurrentis, the causative agent of louse-borne relapsing fever. An initial spirochetemia occurred in all. Inactivity, fever, and leukocytosis accompanied the infections. Eight of the monkeys experienced 1 relapse and 1 monkey had 2 relapses. The relapses tended to be less severe than the initial infections. The only deaths, however, occurred in 2 of the 3 monkeys with severe relapses. The clinical course of the experimental infection in grivet monkeys closely resembles that of natural infections in man.

Alkaline Phosphatase↗

Relapsing fever in Cape Town. A case report.

A 19-year-old male member of the South African Defence Force presented in Cape Town with fever soon after returning from service in northern South West Africa. The typical clinical features of relapsing fever were confirmed by the finding of spirochaetes on stained blood smears. A case report and short review of a disease which has not been reported previously in Cape Town is presented.

Adult↗

Physical mapping of the Borrelia miyamotoi HT31 chromosome in comparison with that of Borrelia turicatae, an etiological agent of tick-borne relapsing fever.

We report the construction of physical maps of chromosomes for Borrelia miyamotoi HT31 (a new species of Borrelia) and Borrelia turicatae (relapsing fever agent) by pulsed-field gel electrophoresis of DNA fragments generated by digestion of chromosomal DNA with rare-cutting restriction endonucleases and reciprocal hybridization. The size of the B. miyamotoi HT31 chromosome was calculated to be approximately 925 kilobase pairs, and the chromosome for B. turicatae was estimated to be 951 kilobase pairs. The chromosomes of B. miyamotoi HT31 and B. turicatae consisted of single linear molecules. The locations of several genes have been assigned to the chromosome maps by Southern hybridization by using specific gene probes. Comparison of the genetic maps of the two species of Borrelia provided evidence that the gene order on the chromosomes is quite similar to that of Borrelia burgdorferi sensu lato strains and is highly conserved in the genus Borrelia.

Blotting, Southern↗

The bdr gene families of the Lyme disease and relapsing fever spirochetes: potential influence on biology, pathogenesis, and evolution.

Species of the genus Borrelia cause human and animal infections, including Lyme disease, relapsing fever, and epizootic bovine abortion. The borrelial genome is unique among bacterial genomes in that it is composed of a linear chromosome and a series of linear and circular plasmids. The plasmids exhibit significant genetic redundancy and carry 175 paralogous gene families, most of unknown function. Homologous alleles on different plasmids could influence the organization and evolution of the Borrelia genome by serving as foci for interplasmid homologous recombination. The plasmid-carried Borrelia direct repeat (bdr) gene family encodes polymorphic, acidic proteins with putative phosphorylation sites and transmembrane domains. These proteins may play regulatory roles in Borrelia. We describe recent progress in the characterization of the Borrelia bdr genes and discuss the possible influence of this gene family on the biology, pathogenesis, and evolution of the Borrelia genome.

Abortion, Veterinary↗

Population structure of the relapsing fever spirochete Borrelia hermsii as indicated by polymorphism of two multigene families that encode immunogenic outer surface lipoproteins.

The tick-borne relapsing fever spirochete Borrelia hermsii evades the mammalian immune system by periodically switching expression among members of two multigene families that encode immunogenic, antigenically distinct outer surface proteins. The type strain, B. hermsii HS1, has at least 40 complete genes and pseudogenes that participate in this multiphasic antigenic variation. Originally termed vmp (for variable major protein) genes, they have been reclassified as vsp (for variable small protein) and vlp (for variable large protein) genes, based on size and amino acid sequence similarities. To date, antigenic variation in B. hermsii has been studied only in the type strain, HS1. Nucleotide sequence comparisons of 23 B. hermsii HS1 genes revealed five distinct groups, the vsp gene family and four subfamilies of vlp genes. We used PCR with family- and subfamily-specific primers, followed by restriction fragment length polymorphism analysis, to compare the vsp and vlp repertoires of HS1 and seven other B. hermsii isolates from Washington, Idaho, and California. This analysis, together with pulsed-field gel electrophoresis genome profiles, revealed that the eight isolates formed three distinct groups, which likely represent clonal lineages. Members of the three groups coexisted in the same geographic area, but they could also be isolated across large geographical distances. This population structure may result from immune selection by the host, as has been proposed for other pathogens with polymorphic antigens.

Borrelia↗

Antibiotic treatment of louse-borne relapsing fever in Ethiopia: a report of 377 cases.

Single-dose non-random, antibiotic treatment was evaluated in 377 Ethiopians with louse-borne relapsing fever. Oral doses of tetracycline hydrochloride 500 mg, doxycycline 100 mg, erythromycin base 500 mg, chloramphenicol 500 mg, or a single intramuscular injection of 1,200,000 units of penicillin aluminum monostearate (PAM) were equally effective treatments. All drugs induced a Jarisch-Herxheimer reaction, which was clinically less severe in patients given PAM. The duration of spirochetemia after treatment was much longer after PAM treatment, however. Three critically ill patients died shortly after receiving antibiotic treatment, from complications of LBRF that were present on admission to hospital.

Ampicillin↗

Typing of Borrelia relapsing fever group strains.

Partial sequencing of the 16S-23S rDNA intergenic spacer showed two to four genotypes each for Borrelia hermsii and B. turicatae, both relapsing fever agents transmitted by argasid ticks, and for B. miyamotoi and B. lonestari, transmitted by ixodid ticks. Field surveys of Ixodes ticks in Connecticut and Sweden showed limited local diversity for B. miyamotoi.

Animals↗

The epidemiology of tick-borne relapsing fever in the United States.

Each year, many residents of and visitors to endemic regions of the western United States are exposed to the vector of tick-borne relapsing fever (TBRF), an underrecognized and underreported disease. Through review of report forms and literature review, we identified 450 cases of TBRF acquired in the United States in 11 western states (and in British Columbia by a U.S. resident) from January 1977 to January 2000. Exposure sites were in forested areas, at varying elevations, in mountainous regions (Cascade, Rocky Mountain, San Bernardino, and Sierra Nevada ranges) of the United States and Canada and in limestone caves in central Texas. Only 13 counties accounted for approximately 50% of all cases. Forty percent of the cases were not residents of the state where TBRF exposure occurred, including 7% from 11 states where TBRF is not endemic. TBRF is endemic in the United States and is a disease affecting travelers, who may return home with the disease to areas where physicians are not familiar with it.

Animals↗

Tick-borne relapsing fever in central Tanzania.

Between October 1985 and September 1986, 488 children aged less than 15 years, 45 pregnant women, 21 other women and 18 men with tick-borne relapsing fever (TBRF) were seen at Mvumi Hospital, Central Tanzania. 88% of the children were less than 5 years old and 36% were less than 1 year. Twelve children were less than 1 month old and some of the 10 infants diagnosed at between 4 and 12 days of age were cases of congenital infection. The clinical features of TBRF in the children and pregnant women were compared with 129 children with a similar age distribution and 52 pregnant women, respectively, who had blood smears positive for malaria but negative for spirochaetes. The common presenting features in children with TBRF were a high fever, splenomegaly, convulsions, and meningism. The difficulty of differentiation from malaria is described. Severe disease in both children and adults was associated with high density of spirochaetes in blood smears. Of the 45 infected pregnant women, 22 (49%) went into labour. One of the deliveries was an abortion and 10 were preterm infants, 4 of whom died. There were no maternal deaths. The estimated overall mortality for children was 1.6%, and 2.3% for those aged less than 1 years; for the 95 children admitted it was 8.4%. Penicillin was a satisfactory treatment for all ages, with a relapse rate of 4.7%. Recommendations for patient management are given.

Adolescent↗

Experimental louse-borne relapsing fever in the grivet monkey, Cercopithecus aethiops. III. Crisis following therapy.

Eight grivet monkeys infected with Borrelia recurrentis received tetracycline (12.5mg/kg body weight) on the 3rd or 4th day of spirochetemia. Leukopenia, fever, hyperpnea, and tachycardia developed within 2 hours as spirochete counts fell to undetectable levels. These events closely simulated the crisis in human louse-borne relapsing fever in both timing and extent.

Animals↗