By Levi Clancy for Student Reader on
First described in 1877, xenodiagnosis is a direct method of diagnosing whether a patient is infected with a particular zoonose.
This method is highly accurate compared to direct microscopy of a patient's blood. As few as 10 Trypanasoma cruzi protozoa may be present per 1mL of blood, though only 1µL can be mounted and viewed at once. Xenodiagnosis is complicated by variable growth of different parasites in different genera and species of vectors.
Non-infected vectors are laboratory-bred, such as Reduviidae for Trypanasoma cruzei or Tsetse Flies for T. brucei.
Laboratory-reared vectors are allowed to feed on a patient in need of diagnosis.
Vectors are allowed to gestate until infectious, such as ~3 weeks for Trypanosoma cruzi or ~2 weeks for T. brucei.
Vectors are examined, such as Reduviid hindguts for Trypanasoma cruzi or Tsetse Fly salivary glands for T. brucei.
If the initially non-infected vector contains the parasite after feeding, then the patient must be infected.