Xenodiagnosis

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.

Step	Overview
Rearing	Non-infected vectors are laboratory-bred, such as Reduviidae for Trypanasoma cruzei or Tsetse Flies for T. brucei.
Feeding	Laboratory-reared vectors are allowed to feed on a patient in need of diagnosis.
Gestation	Vectors are allowed to gestate until infectious, such as ~3 weeks for Trypanosoma cruzi or ~2 weeks for T. brucei.
Examination	Vectors are examined, such as Reduviid hindguts for Trypanasoma cruzi or Tsetse Fly salivary glands for T. brucei.
Conclusion	If the initially non-infected vector contains the parasite after feeding, then the patient must be infected.