Question
A 12-year-old child complained of high fever (1010C), malaise and abdominal pain since 7 days. A blood culture and the Rapid Typhi-dot test was found positive.
- (a) What is most probable clinical diagnosis 1 mark(s)
- (b) Name the causative agent. 1 mark(s)
- (c) Mode of transmission of the infective agent 1 mark(s)
- (d) Pathogenesis of the disease condition e) Write the laboratory diagnosis of the disease f) Mention TWO drugs used in the treatment of the disease g) Write TWO complications of the disease h) Mention the prophylaxis 3 mark(s)
Answer
(a) Most probable clinical diagnosis: Enteric (typhoid) fever.
(b) Causative agent: Salmonella enterica serovar Typhi (occasionally Salmonella Paratyphi A/B/C for paratyphoid fever).
(c) Mode of transmission: Faeco-oral route, via ingestion of food or water contaminated with faeces/urine of an infected patient or a chronic carrier.
(d) Pathogenesis: after ingestion, the organism survives gastric acidity and invades the Peyer’s patches in the terminal ileum via M cells; it is taken up by macrophages, in which it survives and multiplies (facultative intracellular survival), disseminating via the lymphatics to the mesenteric lymph nodes and then into the bloodstream, causing a primary (transient) bacteraemia. The organism then seeds the reticuloendothelial system (liver, spleen, bone marrow), multiplies further, and re-enters the bloodstream as a secondary, sustained bacteraemia, correlating with the onset of clinical symptoms (fever, malaise). Localization back in the Peyer’s patches of the ileum causes hyperplasia, necrosis, and sloughing, producing the characteristic ileal ulcers (potential sites of haemorrhage/perforation in the third week of untreated illness).
(e) Laboratory diagnosis:
- Blood culture — the gold standard, most sensitive in the first week of illness (during bacteraemia).
- Bone marrow culture — most sensitive overall, remains positive even after antibiotic therapy has begun or later in the illness.
- Stool and urine culture — become positive later in the illness (from the second/third week onward), useful for detecting carriers.
- Widal test — detects agglutinating antibody to O and H antigens, meaningfully interpretable from the second week (a rising titre in paired sera is most reliable); limited by cross-reactivity and prior vaccination.
- Rapid immunochromatographic tests (e.g., Typhidot, as used in this case) — detect IgM/IgG antibody against S. Typhi-specific antigens, providing rapid results.
(f) Two drugs used in treatment: Ceftriaxone (third-generation cephalosporin, first-line for complicated/severe cases and in areas with resistance) and Azithromycin (effective oral option, particularly for uncomplicated disease and where fluoroquinolone/MDR resistance is a concern).
(g) Two complications: Intestinal haemorrhage and Intestinal perforation (both occurring typically in the third week of untreated illness, due to necrosis and ulceration of the ileal Peyer’s patches). Other complications include typhoid encephalopathy, myocarditis, and cholecystitis/chronic carrier state.
(h) Prophylaxis: Typhoid (Vi polysaccharide or Vi-conjugate) vaccine, combined with general public-health measures — safe drinking water supply, proper sanitation/sewage disposal, food hygiene, and identification/treatment or exclusion of chronic carriers (particularly those in food-handling occupations).