Relapsing fever is a condition characterized by episodes of fever, headache, myalgias, arthralgias, and nausea followed by a few days of improvement after which there is a recurrence of symptoms. It is caused by some species of Borrelia spirochetes and can be of two types: the tick-borne relapsing fever and the louse-borne relapsing fever. Diagnosis depends on clinical features and identification of the causative organism.
Relapsing fever (RF) is a condition caused by a spirochete and is characterized by typical features of episodic and recurrent high fever, headache, myalgias, and arthralgias. The symptoms last for approximately 3 days, then abate for a week but then recur for another 3 days. This process could continue unless treated. There are two types of RF: tick-borne RF (TBRF) and louse-borne RF (LBRF). TBRF occurs after individuals have lived or slept in rodent-infested mountain cabins while LBRF is transmitted by the body louse and happens in refugee camps or developing regions of the world.
Clinical presentation of TBRF is sudden onset of high fever lasting up to a week and ending with rigors, hypertension, and tachycardia . The first episode is often accompanied by headaches, myalgias, arthralgias, neck stiffness, and nausea. Neurologic symptoms are more common in TBRF after the second episode of fever and include facial palsy, meningismus, myelitis, and radiculopathy followed in certain cases by deficits like hemiplegia and aphasia  . Ophthalmic involvement is associated with a possibility of permanent visual impairment secondary to unilateral or bilateral iridocyclitis or panophthalmitis. Hepatosplenomegaly and myocarditis may be present in fatal cases. Infection of pregnant women has a higher incidence of miscarriages and stillbirths. Gravid women and children have a more serious form of the disease  . During TBRF crises, adult respiratory distress syndrome is also known to develop .
The incidence of jaundice, petechiae, hemoptysis, epistaxis and CNS involvement is higher in LBRF . Patients of LBRF have been reported to have mainly one relapse while those with TBRF have averagely 3 relapses . Delirium and coma can arise in both TBRF and LBRF.
The diagnosis of RF depends on identifying the typical characteristics of the fever along with a thorough medical, social, and travel history as findings of physical examination are not predictable. Spirochetes can be detected on thin and thick peripheral blood smears using Wright’s or Giemsa stain or by isolating them in Kelly culture medium in the period between onset of fever and its peak   . Peripheral blood smears have a sensitivity of 70% and are more sensitive in detecting TBRF than LBRF .
Direct and indirect immunofluorescence can be used to visualize spirochetes with a fluorescence microscope while polymerase chain reaction testing can identify most Borrelia species  . Other laboratory findings include elevated erythrocyte sedimentation rate, anemia, proteinuria,leukocytosis, thrombocytopenia, increased serum unconjugated bilirubin levels, elevated hepatic transaminase levels, prolonged partial thromboplastin and prothrombin times and microhematuria. In TBRF myocarditis, an electrocardiogram may show a prolonged corrected Q-T interval   . Analysis of cerebrospinal fluid (CSF) in patients with neurological symptoms is likely to reveal mononuclear pleocytosis, an elevated protein level, and normal glucose levels  .
Features of pulmonary edema can be noticed on a plain chest X-ray when present. Other imaging studies are indicated only in cases where intracranial or other complications are suspected.
Histological studies help to detect spirochetes using silver stains like Warthin-Starry or modified Dieterle.