Typhoid and paratyphoid fever

Abstract

The bacteriology, epidemiology, pathogenesis, clinical characteristics, diagnosis, treatment and control of enteric fever is reviewed. The prolonged febrile state caused by Salmonella typhi and S. paratyphi A, B or C is a major public health problem in many parts of the world, especially in the developing countires, and international travel has created the problem of 'holiday typhoid'. Over 1800 different serotypes belong to the genus Salmonella, S. typhi being strictly a parasite of man, although S. paratyphi may infect animals also. Spread is principally by contaminated water (often causing explosive widespread outbreaks) or such foods as raw fruit and vegetables or unpasteurized milk and milk products. Ingestion of an adequate infecting dose is followed by penetration through the intestinal mucous membrane, passage to the mesenteric lymph nodes via the lymphatics, hematogenous spread to the reticuloendothelial tissues, and later secondary bacteremia with involvement of many organs, especially the gallbladder. Endotoxemia is not the major mechanism of the prolonged fever and toxemic state, but local effects of the endotoxin with release of endogenous pyrogens is possible. There is no correlation between the presence of O, H and Vi antibodies and relapse or reinfection. Relapse occurs in 8-20% of patients and is usually mild, but one attack generally confers immunity. The most dreaded complications are intestinal hemorrhage or perforation, the latter usually requiring surgery. Other complications include delirium, confusional states, encephalitis, convulsions, disseminated intravascular coagulation, glomerulitis, toxic myocarditis, etc. Confirmation of typhoid and paratyphoid fever requires isolation of the organism from blood, bone marrow, feces or urine. The Widal reaction plays a very minor role in the diagnosis except in tropical countries where bacteriologic confirmation is not possible. Detection and treatment of the carrier state poses special problems and cholecystectomy is often needed. For the treatment of the acute phase, chloramphenicol, ampicillin, amoxycillin and co-trimoxazole have proven effective, but drug-resistent strains are sporadically reported. Immunoprophylaxis is best accomplished by two subcutaneous doses four weeks apart, the protection lasting for up to five years. Although TAB vaccines are widely used, there is little evidence that the paratyphoid component is effective. Immunoprophylaxis should be considered for endemic areas, travellers to such areas, exposed laboratory workers and people living with a chronic carrier. Other control measures require sanitary improvement programs. Unsolved problems in enteric fever requiring future research are listed.