Typhoid and paratyphoid fevers

Typhoid and paratyphoid fever (the enteric fevers) are caused by specific serovars of the Gram-negative bacillus, Salmonella enterica. Sources of typhoid transmission are excreting chronic or convalescent carriers and the acutely infected, with transmission occuring through contamination by carriers of food or water by effluents containing infected urine or faeces. There are an estimated 27 million cases of enteric fever in the world each year, almost all in the developing world, with about 200 000 deaths.

Clinical features—the main symptom is fever (39–40° C); headache and malaise are common; constipation is a frequent early symptom, but most patients will experience diarrhoea; abdominal pain is usually diffuse and poorly localized. Physical examination is often unremarkable, apart from fever, but rose spots and relative bradycardia may be observed. In developing countries, patients may progress in the second to fourth week, with life-threatening manifestations including gastrointestinal bleeding, intestinal perforation, and the syndrome of mental confusion.

Diagnosis—the principal method for confirming the diagnosis is by isolating Salmonella Typhi or Salmonella Paratyphi from blood or bone marrow. The organisms may also be isolated from stool, urine, and bile aspirates, but such demonstration should be interpreted with caution in areas with many chronic carriers as the acute illness may be due to another cause.

Treatment—aside from supportive care, antibiotic therapy reduces mortality and complications and shortens the illness. Antibiotic resistance is a common and increasing problem, hence the choice of antibiotic should be informed by knowledge of likely local susceptibility. Fluoroquinolones are often given as first-line treatment, although low-level resistance to these agents (marked by nalidixic acid resistance) is widespread in Asia, with extended-spectrum cephalosporins and azithromycin as alternatives.

Prevention—typhoid has been eliminated from industrialized countries by (1) the provision of safe drinking water and safe disposal of sewage; (2) legal enforcement of high standards of food hygiene, and programmes to detect, monitor, and treat chronic carriers; and (3) prompt investigation and intervention when these safeguards are breached. Measures for individual protection are to (1) kill the organism in water by heating to 57° C, iodination, or chlorination; (2) take care with uncooked or reheated food; and (3) immunization—two typhoid vaccines are available and widely used in travellers, but their role as a public health tool in endemic areas is undefined; there is no paratyphoid vaccine.