Typhoid Fever

Pathophysiology

1) cause is infection with Salmonella typhi (and occasionally S. paratyphi) 2) disease progresses through two distinct phases 3) first phase – organism migrates from mouth after ingestion to small intestine to lymph system and bloodstream to organ infestation where microbe multiplies 4) second phase – release of the organism from viscera with heavier infestation and the onset of clinical illness; reinvasion of the intestine also occurs

Signs and Symptoms

1) gradual onset 2) characteristic “rose spot” rash on trunk (10%) 3) fever 4) malaise 5) headache 6) constipation/abdominal pain 7) bradycardia 8) myalgias/arthralgias 9) hepatosplenomegaly 10) pharyngitis 11) epistaxis 12) neuropsychiatric conditions (muttering delirium” and “coma vigil” 13) profuse watery diarrhea (late) 14) intestinal hemorrhage and perforation/rigid abdomen, if no treatment 1

Characteristic Test Findings

Laboratory – 1) leukopenia 2) anemia 3) increased transaminases 4) mild coagulopathy 5) normal, decreased, or increased WBCs 6) diagnosis is by culture from marrow, intestinal secretions, or blood

Histology

1) gram-negative enteric rod 2) hyperplastic and necrotic lymphoid tissue 3) focal necrosis of liver 4) inflammation of ileum, colon, and gallbladder 5) enlarged Peyer’s patches and mesenteric lymph nodes

Associated Conditions

Atypical presentations – 1) fever only 2) UTI-type symptoms 3) endocarditis 4) meningitis 5) osteomyelitis 6) soft tissue abscesses 7) glomerulitis 8) pancreatitis 9) hepatitis

Inheritance/Epidemiology

1) incubation period is 10-14 days 2) mortality is 10-15% in untreated; 1% in treated 3) in developed countries, transmission is usually by asymptomatic food handlers 4) carriers – S. typhi is found in feces, gallbladder, and biliary system 5) in active disease – S. typhi found in stool and urine 6) 400-500 cases occur annually in USA

Treatment

1) treatment of choice – ceftriaxone or cefoperazone for 2 weeks 2) quinolones (in adults) and chloramphenicol are also used 3) prednisone for 3 days in severe toxicity (controversial) 4) antibiotics given in first phase of the disease increases the incidence of relapse 5) a typhoid whole-cell vaccine is available for children more than 6 years old; shorter-acting vaccines are used for travelers to endemic areas 6) carriers receive antibiotics for at least 6 weeks

Tips for USMLE

1) patients remain febrile for up to 1 month with a slow defervescence 2) 2 weeks later, 8-10% of patients suffer a relapse 3) hallmarks of the disease are fever and abdominal pain 4) if question mentions patient “picking” at the bed sheets or pajamas, think typhoid fever