Clinical Importance ofSalmonella Paratyphi AInfection to Enteric Fever in Nepal

Abstract

Enteric fever in Nepal is caused by infection with Salmonella typhi or Salmonella paratyphi A. The clinical presentation of these two illnesses has never been compared in a population of travelers and expatriates. If the illnesses are clinically comparable, and if S. paratyphi A infection is sufficiently common, the choice of typhoid vaccine for Nepal may have to take into account the vaccine's efficacy in preventing infection with S. paratyphi A. NonNepalese patients presenting to the CIWEC Clinic with a history of 3 days of fever or greater were considered eligible for the study. Patients with positive blood or stool cultures for S. typhi or S. paratyphi A were entered into the study (along with three patients who had positive Widal titers only). A questionnaire was administered by a physician to determine signs and symptoms. Treatment with oral chloramphenicol was openly compared to treatment with oral ciprofloxacin. Forty-five cases of enteric fever were diagnosed during the 2 years of the study. Infection with S. typhi accounted for 20 cases, and S. paratyphi A was isolated in 22 cases. The illnesses were clinically indistinguishable. Treatment with chloramphenicol and ciprofloxacin was clinically comparable. Infection with S. paratyphi A accounts for a significant percentage of enteric fever presentations among tourists in Nepal, and the illness is comparable to infection with S. typhi. Therefore, the choice of typhoid vaccine for long-term travelers or expatriates in Nepal should take into account the vaccine's potential ability to also prevent S. paratyphi A infection. The only typhoid vaccine that can currently offer this type of cross protection is the whole-cell killed preparation.