Xenodiagnosis 🦟

Xenodiagnosis

Xenodiagnosis = Xenos (foreign) + diagnosis
  • Indirect method to detect infectious agents
  • Uses vectors (insects/animals) as foreign hosts
  • Vector is allowed to feed on/injected with patient material
  • Later, vector is examined for pathogen presence

For questions:

  • Check if the substance injected/consumed in infected → If yes → Xenodiagnosis

Vectors Used

  • Mosquitoes
  • Ticks
  • Mites
  • Flies
  • Fleas
  • Lice

Examples of Xenodiagnosis

1. Chagas Disease

  • Vector: Reduviid bug (lab-bred)
  • Bug feeds on suspected patient
  • After 4–5 weeks, feces checked for Trypanosoma cruzi

2. Dengue Virus

  • Mosquito species:
    • Aedes aegypti
    • Aedes albopictus
    • Toxorhynchites
  • Mosquito is inoculated with virus
  • Virus multiplies in mosquito organs
  • Used to detect Dengue virus

3. Trichinella spiralis Infection

  • Muscle biopsy from patient fed to lab rats
  • T. spiralis larvae detected in rat muscles

Advantages

  • Useful when microscopic detection is difficult
  • Detects low pathogen load in blood

Other Diagnostic Options (Not Xenodiagnosis)

Option
Method
Use
A
Ligated rabbit ileal loop
Detect ETEC enterotoxins
(no vector infection)
C
Inject hamster with splenic biopsy
Diagnose Leishmaniasis via animal inoculation
D
Intradermal test on guinea pig
Test Corynebacterium diphtheriae toxin
  • Option A: Not xenodiagnosis (rabbit not infected)
  • Options C & D: Animal inoculation/virulence tests, not xenodiagnosis
Answer B
Answer B