The bug's fecal deposits are screened initially to determine the presence
of T. cruzi.
(a) All newly collected insects to be used for xenodiagnosis are first
placed singly in a specimen cup with gauze stretched over the top and filter paper
covering the bottom.
(b) Collect insect fecal deposits as soon as possible after the first
defecation. Mix the feces with a drop of 0.9 percent sodium chloride solution on a slide
and examine it microscopically for metacyclic trypanosomal forms. Multiple checks (at
least three) must be made over a period of time to ensure infection-free bugs. If bugs
do not defecate, they must be given a blood meal from clean laboratory animals.
(c) All bugs found positive must either be destroyed or kept separated
from those which are not infected.
STEP 1: Select bugs that have not had a blood meal for two weeks preceding this test.
STEP 2: Place three bugs, one each in three small ointment tin halves. Secure gauze
over the top of each tin. The tins must have several small holes punched in
STEP 3: Place the tins, gauze-side down on the suspected patient's forearm with tins
clustered together. Wrap a strip of black cloth around the patient's arm
covering the ointment tins and secure.
STEP 4: Instruct the patient to sit or lie very still for at least 30 minutes.
STEP 5: Check the bugs at the end of the allotted time to see if they have had a
sufficient blood meal. That is, check to see if they have a distended
abdomen and have ceased feeding.
STEP 6: Return the bugs to the lab and place each in a large gauze covered ointment
tin. Each tin must have complete information written on it such as the
patient's name, species of reduviid, and date the bug fed on patient. On the
bottom of each tin, place a clean piece of filter paper. Change it daily
STEP 7: Two weeks after feeding, collect the fecal deposits and inspect them for
STEP 8: After at least three successive fecal inspections with negative results, remove
the bug and dissect it under a stereoscope.