The Serological Diagnosis of Relapsing Fever* Bh

Diagnosis in relapsing fever is often difficult because of the inadequacy of available methods. Clinical identification of the disease may be unreliable since the physical signs vary and are frequently atypical. Moreover, the symptomatology may resemble any one of several acute infectious diseases, particularly those having an intermittent febrile course. Outstanding among the infections which may be confused clinically with relapsing fever are malaria, spotted fever, typhus, Well's disease, and certain of the enteric diseases particularly in their early stages. According to Magee (1) the occurrence of pulmonary involvement in relapsing fever may cause difficulty in making a differential diagnosis from certain acute respiratory infections. In some instances rat bite fever may also be confused with relapsing fever. The laboratory diagnosis of relapsing fever is more dependable. Although frequently direct microscopic demonstration of the spirochetes in the blood of patients is possible, this method often meets with failure. In that event blood from suspected cases may be injected into suitable experimental animals. Here again, however, unless conditions are optlmn!, demonstration of the characteristic spirochetes in the blood of experimental animals may be unsuccessful. Various explanations have been advanced to account for difficulties in detecting the etiological agent. Patients' blood obtained during the "decline" phase of the paroxysm often shows no spirochetes and may rapidly lose infectivity. An inter-relapse specimen may be repeatedly negative both by direct examination and animal inoculation. Inability to induce experimental infection may be attributed in certain instances to the absence of spirochetes from the inoculum, ~nd in others to loss of viability, even though the organisms are present. Failure to infect may also be due to variations in virulence of the spirochetes as well as to differences in host susceptibilities.