Vector-Borne Diseases

VBD Overview & Control - Vector Vanquishers

• Key Vectors: Mosquitoes (Anopheles, Aedes, Culex), Sandflies, Ticks, Fleas.
• Control Pillars - Integrated Vector Management (IVM):
  • Environmental: Source reduction (e.g., draining stagnant water), improved sanitation.
  • Chemical: Insecticides (IRS, LLINs), larvicides (e.g., Temephos).
  • Biological: Larvivorous fish (Gambusia, Guppy), Bacillus thuringiensis israelensis (Bti).
  • Personal Protection: Repellents (DEET), bed nets, screening.

⭐ The National Vector Borne Disease Control Programme (NVBDCP) in India addresses Malaria, Filariasis, Kala-azar, Japanese Encephalitis, Dengue, and Chikungunya through IVM strategies.

Mosquito-Borne I - Malaria & Dengue Duel

• Malaria
  • Vector: Female Anopheles. Agent: Plasmodium (P.f. severe; P.v/o hypnozoites).
  • Sx: Fever cycles, chills, anemia. P.f.: cerebral malaria, blackwater fever.
  • Dx: PBS (smears), RDTs (HRP2/pLDH).
  • Rx: ACTs (P.f.). Chloroquine (sensitive). Primaquine (P.v/o, G6PD test). Severe: IV Artesunate.
  • 📌 Falciparum Fatal.
• Dengue
  • Vector: Aedes (day-biter). Agent: DENV (1-4 serotypes).
  • Sx: High fever, retro-orbital pain, myalgia, arthralgia ("breakbone fever"), rash.
  • Phases: Febrile → Critical (leakage, D3-7) → Convalescent.
  • Warning Signs: Abd pain, vomiting, fluid accumulation, mucosal bleed, lethargy, liver >2cm, ↑HCT & ↓platelets.
  • Severe: DHF (<100k platelets, leakage), DSS (DHF + shock).
  • Dx: NS1 Ag (early), IgM/IgG, PCR.
  • Rx: Supportive. ⚠️ No NSAIDs.

⭐ Tourniquet test: ≥10-20 petechiae/inch² indicates Dengue capillary fragility.

Mosquito-Borne II - Chik, JE, Fila Trio

• Chikungunya (CHIK)

  • Vector: Aedes aegypti, A. albopictus
  • Virus: Togaviridae (Alphavirus)
  • Clinical: Sudden high fever, severe debilitating polyarthralgia (can persist for months/years), maculopapular rash.
  • Diagnosis: IgM ELISA, RT-PCR.

• Japanese Encephalitis (JE)

  • Vector: Culex spp. (esp. C. tritaeniorhynchus)
  • Virus: Flavivirus
  • Reservoir: Pigs (amplifying host), Ardeid birds (e.g., herons).
  • Clinical: Acute Encephalitis Syndrome (AES) - fever, headache, neck rigidity, altered sensorium, seizures, neurological sequelae.
  • Prevention: JE vaccine (e.g., SA 14-14-2 strain).

  ⭐ JE is a leading cause of viral encephalitis and disability among children in Asia.

• Lymphatic Filariasis (LF)

  • Vector: Culex quinquefasciatus (urban), Mansonia spp. (rural), Anopheles spp. (rural).
  • Parasite: Wuchereria bancrofti (~90%), Brugia malayi, B. timori.
  • Clinical: Asymptomatic microfilaremia, acute episodes (adenolymphangitis - ADL, filarial fever), chronic lymphedema/elephantiasis, hydrocele.
  • Diagnosis: 📌 Night blood smear for microfilariae (W. bancrofti shows nocturnal periodicity), ICT for circulating filarial antigen (CFA).
  • Control: Mass Drug Administration (MDA) with DEC + Albendazole.

Other Vectors - Tiny Terrors' Toll

• Sandfly (Phlebotomus argentipes)
  • Kala-azar (Visceral Leishmaniasis): Caused by Leishmania donovani.
  • Features: Prolonged fever, splenomegaly, hepatomegaly, pancytopenia, weight loss.
  • Diagnosis: rK39 strip test, LD bodies in bone marrow/spleen aspirate.
  • Treatment: Miltefosine, Amphotericin B. Vector control: IRS.
• Tick (Haemaphysalis spinigera)
  • Kyasanur Forest Disease (KFD): Flavivirus, "Monkey Fever".
  • Endemic: Karnataka. Transmission: Tick bite, contact with infected monkeys.
  • Symptoms: Biphasic illness - fever, myalgia; then potential hemorrhagic/neurological phase.
  • Prevention: Vaccine, tick control, Personal Protective Equipment (PPE).

  ⭐ KFD is a tick-borne viral hemorrhagic fever primarily reported from Karnataka, India.

• Flea (Xenopsylla cheopis - rat flea)
  • Plague: Caused by Yersinia pestis. Reservoir: Wild rodents.
  • Forms: Bubonic (painful buboes), Septicemic, Pneumonic (highly infectious).
  • Treatment: Streptomycin, Doxycycline. Control: Rodent & flea control.

High‑Yield Points - ⚡ Biggest Takeaways

• Malaria: P. falciparum causes severe disease; NVBDCP manages control.
• Dengue: Aedes vector; four serotypes; monitor for warning signs.
• Chikungunya: Aedes vector; characterized by crippling arthralgia.
• Japanese Encephalitis: Culex vector, pig reservoir; vaccination is preventive.
• Kala-azar: Transmitted by sandflies; presents with splenomegaly, PKDL.
• Lymphatic Filariasis: Culex vector; MDA with DEC and Albendazole is key.
• Scrub Typhus: Trombiculid mite vector; look for a diagnostic eschar.