Question
19 years old female patient complaints of fever biphasic in nature with severe bone pains in the back and limbs. She had maculo-papular rash and developed haemorrhagic manifestations. Answer the following:
- (a) What is the probable diagnosis. 1 mark(s)
- (b) What is the transmitting vector for this disease. 1 mark(s)
- (c) Discuss the laboratory diagnosis of this disease 4 mark(s)
- (d) List two complications of this disease 2 mark(s)
- (e) Mention the preventive measures to prevent this disease 2 mark(s)
Answer
a) Probable diagnosis: Dengue haemorrhagic fever — biphasic (saddleback) fever, severe bone/joint/muscle pain (“breakbone fever”), maculopapular rash, and haemorrhagic manifestations is classical.
b) Transmitting vector: Aedes aegypti mosquito (a day-biting mosquito; Aedes albopictus is a secondary vector).
c) Laboratory diagnosis
- NS1 antigen — detectable from day 1, before antibody develops, useful for early diagnosis.
- IgM ELISA — becomes positive from about day 5 of illness, indicating recent infection.
- IgG ELISA — the pattern (IgM:IgG ratio) helps distinguish primary from secondary infection.
- RT-PCR — detects viral RNA in the early viraemic phase, also allows serotyping.
- Full blood count — thrombocytopenia and rising haematocrit (haemoconcentration, reflecting plasma leakage) are key supportive laboratory findings.
- Tourniquet test — a simple bedside test for capillary fragility, supporting the diagnosis of haemorrhagic tendency.
d) Two complications
- Dengue Shock Syndrome (DSS) — severe plasma leakage causing circulatory failure/hypotensive shock, a life-threatening emergency.
- Severe haemorrhage — gastrointestinal bleeding or other major bleeding, from thrombocytopenia and vasculopathy.
(Other valid complications: organ impairment — hepatic, cardiac, or neurological involvement.)
e) Preventive measures Mosquito control (source reduction — eliminating stagnant water breeding sites, larvicides, insecticide spraying); personal protective measures (mosquito repellents, protective clothing, bed nets/screens, especially during daytime when Aedes bites); community health education; and, where available, dengue vaccination for select populations in endemic areas.