Relapsing Fever

Relapsing fever is an acute, febrile illness that can be transmitted through lice or ticks. Disease is characterized by the sudden onset of high fever, chills, myalgia, delirium, joint pain, and nausea. The initial fever may occur 2 days to 2 weeks following infection, with symptoms that last 3-9 days. Successive relapses can occur after as little as 2-3 days, or as long as 2 months after the primary infection, and relapses can occur from 1 to 13 times. Secondary spirochaetemia and fever relapses occur because of antigenic variation in the variable major surface protein (vmp) of the organism. Rearrangement of silent and expressed genetic loci alters the vmp gene, and the result is an altered antigenic surface structure that allows the organism to temporarily evade the immune

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Louse-borne relapsing fever is caused by B. recurren-tis, which enters the host through skin abrasions or through mucous membranes that have made contact with hemolymph from crushed lice. Borrelia are not transmitted through a louse bite, as they are not present in the louse saliva. B. recurrentis is the only Borrelia species for which humans are the sole host; all other species are maintained in various wild-animal reservoirs. Because of the nature of the vector, including the increased prevalence in regions with poor hygienic practices, louse-borne relapsing fever can result in epidemics, and it is often referred to as epidemic relapsing fever. Mortality rates can be greater than 50% for untreated cases, although this drops to less than 5% following antibiotic treatment. Currently, disease outbreaks are relatively rare, and they are primarily found in Africa, although historically, cases have been reported throughout Europe and Asia as well.

Tick-borne relapsing fever, or endemic relapsing fever, is isolated to regions containing the vectors and their reservoir hosts. Infection is a result of the direct transfer of Borrelia from the tick saliva to the host. The soft-bodied ticks, which are implicated as vectors, feed for only a short duration, and infection of the host occurs very rapidly, as opposed to the extended feedings that are required for transmission of Lyme-disease-causing spirochetes. Relapsing fever is caused by a number of different characterized Borrelia species, and most are associated with a species-specific vector. As with louse-borne relapsing fever, cases of the tick-borne variety are uncommon. For example, less than 1000 cases have been reported in the United States in the past 40 years. Nevertheless, it is not likely that tick-borne relapsing fever will ever be eradicated, considering that there are a number of natural reservoirs, and that vertical transmission can occur in ticks.

While the documentation of recurring febrile episodes in a patient is diagnostic for relapsing fever, the rarity of the disease, the variable pattern of recurrences (or the lack of recurrences), and the fact that patients may not recall being bitten by a tick can make diagnosis difficult. Laboratory diagnosis can be helpful in some instances. Organisms can be visualized by microscopy (using Giemsa or Wright stains) in blood smears obtained during a spirochaetemic/febrile phase, or they may be directly viewed using darkfield microscopy. It has been estimated that the detection sensitivity of microscopy is approximately 70%.[41 In addition to direct observation, organisms can be cultured from specimens, and the cultures can then be monitored by microscopy for the growth of

Borreliae. Aside from microscopic techniques, there have been few advances in relapsing fever diagnosis. This is, for the most part, due to the relatively few outbreaks that occur, and the consequent lack of utility for such tests. Serology is generally not used in diagnosis, and although molecular detection methods involving amplification of specific Borrelia genes using the polymerase chain reaction (PCR) have been devised,[51 they are rarely utilized. The low disease prevalence coincides with a low demand for these tests, and it also means that such tests are not considered to be useful for routine differential diagnoses of febrile illnesses.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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