Vector-borne diseases — A/L Biology

What must I remember about Vector-borne diseases?

• Vector-borne diseases are human illnesses caused by parasites, viruses, and bacteria transmitted primarily by hematophagous arthropod vectors (mosquitoes, sandflies, ticks, fleas).
• Dengue Fever & DHF: Caused by Dengue virus (DENV 1-4, Flavivirus) transmitted by daytime-biting female Aedes aegypti and Aedes albopictus mosquitoes; breeds in clean artificial water receptacles; presents with retro-orbital pain, severe arthralgia, thrombocytopenia, plasma leakage, and circulatory shock.
• Malaria: Caused by Plasmodium protozoa (P. falciparum, P. vivax, P. malariae, P. ovale) transmitted by nocturnal-biting female Anopheles mosquitoes; complex life cycle involving hepatic schizogony, intraerythrocytic cycle causing synchronized paroxysmal fever/chills, and gametocyte transmission.
• Filariasis & Leishmaniasis: Lymphatic filariasis caused by Wuchereria bancrofti nematode transmitted by polluted-water-breeding Culex quinquefasciatus mosquitoes, damaging lymphatic vessels to cause elephantiasis; Leishmaniasis caused by Leishmania donovani transmitted by Phlebotomus sandflies causing cutaneous ulcers or visceral infection.
• Integrated Vector Management (IVM): Rational multi-pronged approach — Environmental management (eliminating standing breeding water containers), Biological control (larvivorous fish Poecilia reticulata and Gambusia affinis, Bacillus thuringiensis israelensis - BTI bacteria), and Chemical control (indoor residual spraying IRS, larvicides, insecticide-treated bed nets ITNs).

Test yourself (1 minute)

1. Mosquito breeding site segregation

   Aedes breeds in small artificial clean water containers (tires, roof gutters, discarded plastic cups); Anopheles breeds in slow-moving unpolluted natural waters (stream margins, paddy fields); Culex breeds in heavily polluted organic wastewater and blocked drains.

2. Sri Lanka's Malaria-free status

   Sri Lanka was certified malaria-free by the World Health Organization (WHO) in 2016 through sustained rigorous active and passive surveillance, though Anopheles vector competence persists.

3. Dengue Shock Syndrome (DSS) pathogenesis

   Antibody-dependent enhancement (ADE) occurs when secondary infection with a heterologous dengue serotype triggers non-neutralizing cross-reactive antibodies that facilitate massive viral entry into monocytes, causing cytokine storm and plasma vascular collapse.

Practise Vector-borne diseases questions today

Source: NIE G.C.E. (A/L) Biology Syllabus & Resource Book, Unit 10

What should I study first?

What comes next?

Next in the syllabus

Where does Vector-borne diseases fit in the syllabus?

Year 2 · Term 3