Enteric Fever Overview

Enteric Fever

• Causative Agent: Salmonella genus, specifically S. typhi and S. paratyphi A, B, and C.
• Gram Negative Motile Bacilli: Aerobes and facultative anaerobes, grow on ordinary media.
• Reservoir: Humans are the only known reservoir, either as cases or carriers.
• Carriers: Can be temporary (incubatory or convalescent) or chronic.
  • Convalescent carriers excrete bacilli for 6-8 weeks.
  • Less than 4% of cases still excrete organisms after 3 months.
  • Average carrier rate is around 3% after one year.
  • Chronic carriers harbor the organism in the gallbladder, biliary tract, or rarely the intestine or urinary tract.
• Transmission:
  • Common Vehicle: Shellfish from contaminated sewage and milk products.
  • Vector: Flies.
  • Indirect Contact: Transmission from articles soiled with urine or feces.
  • Direct Contact: With patients or carriers.
• Period of Communicability: From the second week throughout convalescence, commonly 1-2 weeks for paratyphoid.
• Susceptibility and Resistance: Gastric achlorhydria and HIV/AIDS patients are more susceptible.
  • Relative specific immunity follows clinical disease, unapparent infection, and immunization.
  • No solid immunity; second attacks can occur.
• Pathogenesis:
  • Primary Bacteremic Phase (7-10 days): Oral route → small intestine → intestinal lymphatic → thoracic duct → blood → disseminated into organs (liver, spleen, bone marrow).
  • Secondary Bacteremia: After multiplication in organs, bacteria return to the blood, causing pyrexia and other clinical signs.
  • Gallbladder to Intestine: Bacteria from the liver travel through the biliary tract to the gallbladder, then to the intestine.
  • Localization in the Kidney: Bacteria can localize in the kidney and appear in the urine.
• Clinical Picture: Incubation period depends on the infective dose and host factors.
  • Typhoid: 8-14 days.
  • Paratyphoid: 1-10 days.
  • Signs and Symptoms:
    • First Week: Headache, malaise, anorexia, muscle pains, fatigue, abdominal pain, stepladder fever, relative bradycardia (Faget sign), constipation (diarrhea in children), bronchitis with dry cough.
    • Second Week: High and sustained fever (around 40°C), toxic and disoriented, abdominal pain and distension, diarrhea, doughy sensation on abdominal examination, hepatosplenomegaly in 50% of patients, rose spots (7th-10th day), rhonchi and rales heard.
    • Third Week: Ill and dehydrated, rapid and thready pulse, disoriented, mental cloudiness, hemorrhage and perforation.
    • Fourth Week: Improvement, afebrile.
  • Relapse: Occurs in 10% of patients, 1-3 weeks after stopping treatment.
• Complications:
  • Intestinal Perforation: Late second or early third week.
  • Intestinal Hemorrhage.
  • Hepatobiliary: Mild jaundice, asymptomatic typhoid hepatitis with elevated ALT and AST, acute or chronic cholecystitis, pancreatitis.
  • Cardiopulmonary: Toxic myocarditis, thrombosis, mild bronchitis, pericarditis (toxic myocarditis may cause Faget sign in the first week).
  • Genitourinary: Immune complex mediated glomerulonephritis, nephrotic syndrome, acute tubular necrosis, pyelonephritis, pyelitis.
  • Hematological: Subclinical disseminated intravascular coagulation (DIC), thrombocytopenia, anemia, leucopenia, and relative lymphocytosis.