Negative Effects of African
Trypanosomiasis
• (3) Other:
– Presence of tsetse flies have affected the
environment.
• Pesticides!
Negative Effects of African
Trypanosomiasis
• (3) Other:
– Presence of tsetse flies have affected the
environment.
• Pesticides!
– Presence of tsetse flies have affected the
climate.
• Cattle are underweight.
• Many regions have extensive over-grazing.
Negative Effects of African
Trypanosomiasis
• (3) Other:
– Presence of tsetse flies have affected the
environment.
• Pesticides!
– Presence of tsetse flies have affected the
climate.
• Cattle are underweight.
• Many regions have extensive over-grazing.
– Aesthetics.
• How many wild animals can we live with?
American Trypanosomiasis
• Trypanosoma cruzi: Causative agent of
Chagas’ Disease.
• Trypanosoma rangeli: non-pathogenic
species in humans.
T. cruzi
T. rangeli
Transmission
• Transmitted by biting insects in the order
Hemiptera.
Transmission
• Transmitted by biting insects in the order
Hemiptera.
– Family Reduvidae (Assassin bugs, Reduvids,
or Kissing bugs).
Transmission
• Transmitted by biting insects in the order
Hemiptera.
– Family Reduvidae (Assassin bugs, Reduvids,
or Kissing bugs).
– 28 + species however most important are:
•
•
•
•
Triatoma infestans
Triatoma sanguisaga
Panstrongylus megistus
Rhodnius prolixus
• Large up to 34 mm.
• Some species found
on the ground, some
in trees and some in
human dwellings.
• Eggs, are laid and
have 5 nymphal
instars.
Kissing Bug Feeding on a Person
How do People Get Infected?
• Epimastigotes are not found in the salivary
glands, but instead gather in the rectum of the
kissing bugs.
How do People Get Infected?
• Epimastigotes are not found in the salivary glands, but
instead gather in the rectum of the kissing bugs.
• In order to get infected epimastigotes must
come in contact with mucous membranes or
open wound!
•Most of these bugs
usually defecate at the
same time as they are
feeding!
Main Difference From African
Trypanosomiasis
• Trypomastigotes do not persist long in
the circulatory system and they also do
not reproduce there.
Main Difference From African
Trypanosomiasis
• Trypomastigotes do not persist long in the circulatory
system and they also do not reproduce there.
• Instead they move into muscle cells
where they become amastigotes and
reproduce by binary fission.
1) *Epimastigotes
transmitted
through bug
feces.
2) Trypomastigotes
found in the
peripheral blood.
3) Amastigotes
reproduce in
muscle cells.
• In American trypanosomiasis transmission
is Stercorarian or Posterior Station!
Distribution
Primarily in costal areas of US and a few reports
in Texas and Arizona!
Epidemiology
Dogs and
Cats can
serve as
hosts!
Dogs and
Cats can
serve as
hosts!
Chickens
serve as
good blood
source for
bugs!
T. cruzi in North America
• Sow Why don’t people get infected?
Vectors
• Triatoma
gerstaeckeri
• Triatoma
sanguisuga
Vectors
• Feeding habits of T. sanguisuga and T.
gerstaeckeri differ from their Latin
American counterparts.
Vectors
• Feeding habits of T. sanguisuga and T. gerstaeckeri differ
from their Latin American counterparts.
• T. sanguisuga and T. gerstaeckeri are very
cautious and neither will walk completely
onto a host, reducing the chances of
defecating on the host.
Vectors
• Feeding habits of T. sanguisuga and T. gerstaeckeri differ
from their Latin American counterparts.
• T. sanguisuga and T. gerstaeckeri are very cautious and
neither will walk completely onto a host, reducing the
chances of defecating on the host.
• Both T. gerstaeckeri and T. sanguisuga
generally do not defecate while feeding,
reducing fecal contact with the wound even
further.
• So how do the reservoir hosts become
infected?
American Trypanosomiasis
Course of Infection
• There are three phases.
American Trypanosomiasis
Course of Infection
• Phase I. Trypomastigotes in peripheral
circulation.
– Edema at site of bite (often eye and cheek): if
on other area of the body than local
inflammation produces a small red nodule
(Chagoma) which is a swelling of the
regional lymph node.
– Headache, fever, prostration.
American Trypanosomiasis Course of
Infection
Romaña’s Sign
American Trypanosomiasis
Course of Infection
• Phase II. Trypomastigotes enter cells.
– Symptoms of phase I subside or become
absent.
American Trypanosomiasis
Course of Infection
• Phase III. Amastigotes within cells.
– Almost any cell can be invaded; however
they most commonly invade cells of the
reticuloendothelial system in the spleen and
liver, and cardiac, smooth and skeletal
muscles, additionally the nervous system
may be infected.
American Trypanosomiasis
Course of Infection
• Phase III. Amastigotes within cells.
American Trypanosomiasis
Course of Infection
• Phase III. Amastigotes within cells.
– Edema: abnormal accumulation of fluid in
the tissue spaces (cellular level)
– Inflamed lymph glands
– Enlarged spleen and liver (hyperplasia)
Pathology of Trypanosoma cruzi
Chronic phase - occurs
in adults.
Apex of heart usually
becomes very thin.
Impulses into
ventricles are affected.
American Trypanosomiasis
Course of Infection
• Phase III. Amastigotes within cells.
– Heart muscles:
• Fibers separated, inflamed
• Fibers weakened/ myocardial dysfunction
 (irregular heartbeat)
• Invasion of connective tissue which will
cause an enlarged heart
• Nerve ganglia destroyed/ cardiac arrest
Pathology of Trypanosoma cruzi
• Megaesophagus and Megacolon.
Pathology of Trypanosoma cruzi
• Megaesophagus and Megacolon.
• Muscle tone and peristalsis is destroyed.
Pathology of Trypanosoma cruzi
• Megaesophagus and Megacolon.
• Muscle tone and peristalsis is destroyed.
• Organs increase their diameters
greatly.
Pathology of Trypanosoma cruzi
• Megaesophagus and Megacolon.
• Muscle tone and peristalsis is destroyed.
• Organs increase their diameters greatly.
• Victim may not be able to swallow
and dies from starvation.
Pathology of Trypanosoma cruzi
•
•
•
•
Megaesophagus and Megacolon.
Muscle tone and peristalsis is destroyed.
Organs increase their diameters greatly.
Victim may not be able to swallow
and dies from starvation.
• Feces not formed effectively.
Pathology of Trypanosoma cruzi
Diagnosis
• Demonstration of trypanosomes in blood,
but this is very difficult.
• ELISA
• Xenodiagnosis
Xenodiagnosis
Prognosis and Epidemiology
• Not Good!! No effective treatment!
• 12-19 million people infected in the early
1990’s in Central and South America!
• Currently about 25% of people are
infected in Latin America!
Prognosis
• Not all people die from it!
• Children have acute cases and within a
month die.
• Adult infections are more chronic.
– Have shorter life span
– 30% die!