Enteric fever (Typhoid & Paratyphoid fever) : Causes, Pathogenesis, Symptoms, Diagnosis, Treatment & Prevention

Typhoid / Enteric Fever : Causes, Pathogenesis, Symptoms, Diagnosis, Treatment & Prevention


  • Typhoid fever is caused by bacteria Salmonella enteritis & its 2 subtypes Salmonella typhi (Typhoid) and Salmonella paratyphi (Paratyphoid).
  • Humans are the sole reservoir for S. typhi and S. Paratyphi .
  • Salmonella tansmission occurs from person to person or via contaminated food or water.
  • Unlike Salmonella enteritis, Salmonella typhi can disseminate via blood & lymphatic vessels.

Clinical Symptoms :

  • The incubation period is typically about 10–14 days but can be longer, and the onset may be insidious.
  • Hallmark symptoms of Typhoid is Sustained fever .
  • Typhoid is clinically menifested by following symptoms :
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  • Acute infection is associated with anorexia, abdominal pain, bloating, nausea, vomiting, and bloody diarrhea followed by a short asymptomatic phase that gives way to bacteremia and fever with flu-like symptoms.

Complications :

  • Dissemination Salmonella typhi  into systemic circulation leads severe complication (Extraintestinal complications).
  • Haemorrhage from, or a perforation of, the ulcerated Peyer’s patches may occur at the end of the second week or during the third week of the illness.
  • A drop in temperature to normal or subnormal levels may be falsely reassuring in patients with intestinal haemorrhage.
  • Thus, Complications of Typhoid are as follows:
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Pathogenesis :

  • Very few viable Salmonella organisms are necessary to cause infection, and the absence of gastric acid, as in persons with atrophic gastritis or those on acid-suppressive therapy, further reduces the required inoculum.
  • Salmonellae possess virulence genes that encode a type III secretion system capable of transferring bacterial proteins into M cells and enterocytes. The transferred proteins activate host cell Rho GTPases, thereby triggering actin rearrangement and bacterial uptake into phagosomes where the bacteria can grow.
  • Salmonellae also secrete a molecule that induces epithelial release of a chemoattractant eicosanoid that draws neutrophils into the lumen and potentiates mucosal damage. Stool cultures are essential for diagnosis.

Diagnosis :

Salmonellae can be detected by following tests:

  • Agglutination test
  • Widal test / Tube dilution agglutination test

Treatment :

Typhoid can be treated by following drugs:

  • First line drugs (Quite ineffective due to resistence development)
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  • Second line drugs
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Choice of drug (antibiotic) depemnds upon the susceptibility of Salmonella strains in the area of residence or travel therefore, Typhoid is treated in following manner :

  • Empirical Treatment
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  •  Drug susceptible Typhoid
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  • Multi-Drug Resistant MDR Typhoid
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  • Quinolone Resistant / Decreased Ciprofloxacin Susceptibility DCS Typhoid
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Note :-

  • Ofloxacin 400 mg ( OD ) such as Zanocin OD ; is best preferred drug for Short course treatment of Typhoid for adults .
  • For paratyphoid , the course tends to be shorter and milder than that of typhoid fever and the onset is often more abrupt with acute enteritis.

Prevention :

  • Improved sanitation and living conditions reduce the incidence of typhoid.
  • Travellers to countries where enteric infections are endemic should be inoculated with one of the three available typhoid vaccines (two inactivated injectable and one oral live attenuated).
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