Trypanosomiasis is caused by protozoan parasites of the genus Trypanosoma. The document discusses the characteristics, life cycles, transmission, pathogenesis and clinical features of three main species that infect humans: T. brucei gambiense which causes West African sleeping sickness; T. brucei rhodesiense which causes East African sleeping sickness; and T. cruzi which causes Chagas disease. Key points covered include the morphologic forms of the parasites, their multi-host life cycles requiring both human and insect hosts, methods of laboratory diagnosis, and treatment approaches for the different stages of disease.

1. Trypanosomiasis
Mohamed Sinan
Govt Medical College, Calicut

2. • Phylum : Sacromastigophora
• Subphylum : Mastigophora
• Class : Kinetoplastidea
• Order : Trypanosomatida
• Family : Trypanosomatidae

3. General Characteristics
• Members of family Trypanosomatidae live
in the blood and tissues of man and other
vertebrate hosts and in the gut of the
insect vectors. (They are called
hemoflagellates)
• They have a single nucleus, a kinetoplast,
and a single flagellum. Kinetoplast
consists of a deeply staining parabasal
body and adjacent dot-like blepharoplast.
• Nucleus is round or oval and is situated in
the central part of the body.

4. • 4 morphological states (Based on
position/arrangement of flagella)
– Amastigote
– Promastigote
– Epimastigote and
– Trypomastigote.
• Each exists in 2 or more of these 4
morphologic states.

5. Staining :
• For smears of body fluids,
Romanowsky’s Wrights stain, Giemsa
stain, and Leishman’s stain are
suitable. The cytoplasm appears blue,
the nucleus and flagellum appear pink,
and the kinetoplast appears deep red.
• For tissue section, hematoxylin eosin
staining is done for demonstrating
structures of the parasite.

6. T. brucei light microscopy – Giemsa stain

7. T. cruzi in blood smear – giemsa staining

8. • All members of the family have similar
life cycles. They all require an insect
vector as an intermediate host.
• Multiplication in both the vertebrate
and invertebrate host is by binary
fission. No sexual cycle is known.

9. • Family Trypanosomatidae consists of 6
genera
• 2 of them are pathogenic to humans –
– Trypanosoma
– Leishmania

10. Trypanosomes
General Characters
• All members of the genus
Trypanosoma exist in trypomastigote
stage at sometime in their life cycle.
• Some trypanosomes (T. cruzi) assume
amastigote forms in vertebrate hosts.
• They also show polymorphism

11. • Trypanosoma pass their life cycle in 2
hosts –
– vertebrate hosts (definitive hosts)
– insect vectors (intermediate hosts).
• During incubation period the parasite
undergoes development and
multiplication in the vector.
• In the vector, the trypanosomes are
classified into 2 groups according to
mode of development :

12. • €Salivaria (anterior station): The
trypanosomes migrate to mouth parts
of the vectors; Infection is transmitted
by their bite (inoculative transmission).
(e.g. T. gambiense)
• €Stercoraria (posterior station): The
trypanosomes migrate to the hindgut
and are passed in faeces (stercorian
transmission). (e.g. T. cruzi)

13. Trypanosomes Infecting Man
• Trypanosoma brucei complex, causing
African trypanosomiasis (sleeping
sickness)
Subspecies are:
- Trypanosoma brucei gambiense: causing
West African sleeping sickness.
- Trypanosoma brucei rhodesiense: causing
East African sleeping sickness.
• Trypanosoma cruzi, causing South
American trypanosomiasis or Chagas’
disease.
• Trypanosoma rangeli, a nonpathogenic
trypanosome causing human infection in

14. Trypanosoma Brucei Gambiense
(West African Trypanosomiasis)
• First isolated in 1901 by Forde.
• The name Trypanosoma gambiense
was proposed by Dulton, in 1902
• It is endemic in West and Central Africa
• Habitat: They live in man and other
vertebrate hosts. They are parasites of
connective tissue.

15. Morphology
Vertebrate Forms
• In the blood of vertebrate host, T.
brucei gambiense exists as
trypomastigote form, which is highly
pleomorphic
• It occurs as a long slender form; a
stumpy short broad form with
attenuated or absent flagellum; and an
intermediate form.
• The trypomastigotes are about 15–40
μm long and 1.5 – 3.5 μm broad.

16. Insect Forms
• In insects, it occurs in 2 forms:
– Epimastigotes
– Metacyclic trypomastigote forms.

17. Antigenic Variation
• Trypanosomes exhibit unique antigenic
variation of their glycoproteins.
• There is a cyclical fluctuation in the
trypanosomes in the blood of infected
vertebrates after every 7–10 days.
• Each successive wave represents a
variant antigenic type (VAT) of
trypomastigote posssesing Variant
Surface Specific Antigens (VSSA) or
Variant Surface Glycoprotein (VSG) coat
antigen.
• A single trypanosome may have 1,000 or

18. Life Cycle
• T. brucei gambiense passes its life
cycle in 2 hosts.
– Vertebrate host: Man, game animals, and
other domestic animals.
– Invertebrate host: Tsetse fly.
• Both male and female tsetse fly of
Glossina species (G. palpalis) are
capable of transmitting the disease to
humans.
• Infective form: Metacyclic

19. • Mode of transmission:
– By bite of tsetse fly
– Congenital transmission has also been
recorded.
• Reservoirs: Man is the only reservoir
host, although pigs and others
domestic animals can act as chronic
asymptomatic carriers of the parasite.

21. Development in Man and Other
Vertebrate Hosts
• Metacyclic stage (infective form) of
trypomastigotes are inoculated into a man
(definitive host) through skin when an
infected tsetse fly takes a blood meal
• The parasite transforms into slender forms
that multiply asexually for 1–2 days before
entering the peripheral blood and lymphatic
circulation.
• These become ‘stumpy’ via intermediate
forms and enter the blood stream.
• It invades the central nervous system in
chronic infection.

22. Development in Tsetse Fly
• In the midgut of the fly, short stumpy
trypomastigotes develop into long,
slender forms and multiply.
• After 2–3 weeks, they migrate to the
salivary glands, where they develop into
epimastigotes, which multiply and fill the
cavity of the gland and eventually
transform into the infective metacyclic
trypomastigotes
• Development of the infective stage within
the tsetse fly requires 25–50 days
(extrinsic incubation period).

24. Pathogenecity and Clinical
Features
• T. brucei gambiense causes African
trypanosomiasis (West African sleeping
sickness).
• The illness is chronic and can persist for
many years.
• There is an initial period of parasitemia,
following which parasite is localized
predominatly in the lymph nodes.
• A painless chancre (trypanosomal
chancre) appears on skin at the site of
bite by tsetse fly, followed by intermittent
fever, chills, rash, anemia, weight loss,

25. • Systemic trypanosomiasis without central
nervous system involvement is referred to
as stage I disease.
• In this stage, there is hepatosplenomegaly
and lymphadenopathy, particularly in the
posterior cervical region (Winterbottom’s
sign).
• Hematological manifestations seen in
stage I include anemia, moderate
leucocytosis, and thrombocytopenia.

26. • Stage II disease involves invasion of
central nervous system. With this, the
‘sleeping sickness’ starts.
• This is marked by increasing headache,
mental dullness, apathy, and day time
sleepiness.
• There is infiltration of the brain & spinal
cord, and neuronal degeneration.

27. • Abnormalities in cerebrospinal fluid
include raised intracranial pressure,
pleocytosis, and raised total protein
concentrations.
• The patient falls into coma followed by
death from asthenia.

28. Trypanosoma Brucei Rhodesiense
(East African Trypanosomiasis)
• It is found in Eastern and Central Africa
• Discovered by Stephans and Fanthan
in 1910 from the blood of a patient in
Rhodesia suffering from sleeping
sickness.
• The principal vector is G. morisitans, G.
palpalis, and G. Swynnertoni

29. Pathogenesis and Clinical
Feature
• T. brucei rhodesiense causes East African
sleeping sickness
• East African trypanosomiasis is more
acute than the Gambian form and appears
after an incubation period of 4 weeks.
• It may end fatally within an year of onset,
before the involvement of central nervous
system develops.
• Pathological features are similar in both
diseases with some variations— Edema,
myocarditis, and weakness are more
prominent in East African sickness.

30. • Lymphadenitis is less prominent.
• Febrile paroxysms are more frequent
and severe.
• There is a larger quantity of parasite in
the peripheral blood.
• €Central nervous system involvement
occurs early.
• Mania and delusions may occur but the
marked somnolence, which occurs in T.
brucei gambiense infection is lacking.

31. Laboratory Diagnosis
The diagnosis of both types of African
trypanosomiasis is similar
• Nonspecific Findings
– Anemia and monocytosis.
– Raised ESR due to rise in gamma globulin
levels.
– Reversal of albumin:globulin ratio.
– Increased cerebrospinal fluid (CSF)
pressure and raised cell count and
proteins in CSF.

32. • Specific Findings
– Definitive diagnosis of sleeping sickness
is established by the demonstration of
trypanosomes in peripheral blood, bone
marrow, lymphnode, CSF, and chancre
fluid.

33. Microscopy
• Wet mount preparation of lymph node
aspirates and chancre fluid are used as
a rapid method for demonstration of
trypanosomes.
• These specimen are also examined for
parasites after fixing and staining with
Giemsa stain.
• Examination of Giemsa stained thick
peripheral blood smears reveals the
presence of trypomastigotes

34. • If parasitemia is low, then examination
of concentrated blood smear is a highly
sensitive method.
• Different concentration techniques
employed are buffy coat examination,
differential centrifugation, membrane
filtration, and ion exchange column
chromatography.
• Examination of wet mount and stained
smear of the CSF may also show
trypanosomes

35. Culture
• The organisms are difficult to grow,
hence culture is not routinely used.
However, it can be cultivated in
Weinman’s or Tobie’s medium.
Animal Inoculation
• Inoculation of specimens from
suspected cases to white rat or white
mice is a highly sensitive procedure for
detecting T. brucei rhodesiense
infection.

36. Serodiagnosis
Antibody detection
• Almost all infected have very high levels of
total serum IgM & CSF IgM
• Various serological methods to detect these
antibodies are:
– Indirect hemagglutination (IHA)
– Indirect immunofluroscence (IIF)
– Enzymelinked immunosorbent assay (ELISA)
– Card agglutination trypanosomiasis test (CATT)
– Complement fixation test (CFT)
• Specific antibodies are detected by these
tests in serum within 2–3 weeks of infection.
• Specific antibodies in CSF - demonstrated by

37. Antigen detection
• Antigens from serum and CSF can be
detected by ELISA.

38. Imaging
• CT scan of the brain shows cerebral
edema and MRI shows white matter
enhancement in patients with late stage
CNS involvement

39. Treatment
• In stage I (i.e. No CNS involvement),
pentamidine is the drug of choice for
gambiense HAT and suramin is the drug of
choice for rhodesiense HAT.
• Dose:
– Pentamidine: 3 - 4 mg/kg body weight, IM
daily for 7–10 days.
– Suramin: 20 mg/kgbody weight in a course of
5 injections intravenously, at an interval of 5–
7 days.

40. • In stage II, melarsoprol (MelB) is the
drug of choice, as it can cross the
blood brain barrier.
• Dose: 2–3 mg/kg/day(max. 40 mg) for
3–4 days

41. Prophylaxis
• Control - based on early diagnosis and
treatment of cases to reduce the
reservoir of infection.
• Control of tsetse fly population (most
important preventive measure) by wide
spraying of insecticides, traps, and
baits impregnated with insecticides.
• No vaccine is available.

42. Trypanosoma Cruzi
(Chagas’ Disease)
• It is the causative organism of chagas’s
disease or South American
trypanosomiasis.
History and Distribution:
• Carlos Chagas, investigating malaria,
accidently
discovered T. cruzi
• Zoonotic disease; limited to south and
central America

43. Habitat
• In humans – exist in Amastigote and
trypomastigote forms.
Amastigotes - Intracellular
parasites
- Found in muscular
tissue,nervous tissue and
RE system.
Trypomastigotes - Found in peripheral
blood

44. • In reduviid bugs
– Amastigotes found in midgut
– Trypomastigote present in hindgut and
feces

45. Morphology
Amastigote
Oval body{2-4 micro mtr dia}.it has a
nucleus and kinetoplast.
• Flagellum is absent
• Resembles amastigote of Leishmania
spp, so it is called leishmanial form.
• Multiplication occurs in this stage

46. Trypomastigote
• Non muliplying form.
• In blood, they appear either as long,thin
flagellates{20 μm long} or short stumpy
form {15μm long}
• Posterior end is wedge-shaped
• In stained blood smears, shaped like
‘C’, ’U’ or ‘S’, having a free flagellum of
1/3 length of body

47. Epimastigote Form
Found in insect vector, reduviid bug and
in culture
• It has a kinetoplast adjascent to
nucleus.
• An undulating membrane runs along
anterior half of parasite.
• Divide by binary fission in hindgut of
vector

48. Life Cycle
T.Cruzi passes its life cycle in 2 hosts
Definitive host :Man
Intermediate host(vector):
Reduviid bug or triatomine bugs
Infective form:
Metacyclic trypomastigotes , found in
reduviid bugs
Reservoir host: Armadillo, cat, dog and
pigs.

49. Mode of transmission
• Man is infected :
ˉ By fecal matter of reduviid bug being
rubbed into bite wound .
ˉ Through contamination of conjunctiva and
other mucous membrane surfaces.
ˉ Congenitally
ˉ By blood transfusion

51. Pathogenicity and Clinical
Features
• Incubation period - 1-2 weeks in man
• Disease manifest in acute and chronic
form.

52. Acute Chagas’ Disease
• Occurs soon after infection. Last for 1-4
months.
• Often seen in children under 2 yrs of
age
• First sign appears with in a week after
invasion.
• Inoculation of parasite in conjunctiva
causes unilateral, painless oedema of

53. • In few patients, there may be
generalised infection with fever,
lymphadenopathy and
hepatosplenomegaly
• Patient may die of acute myocarditis
and meningoencephalitis

54. Chronic Chagas’ Disease
Found in adults and older children
• It become apparent,years or even
decades after the initial infection
• It produces inflammatory
response,cellular destruction,and
fibrosis of muscles and nerves,that
control tone of hollow organs like
heart,oesophagus,colon etc.
• Thus,it can lead to cardiac myopathy
and megaoesophagus and megacolon

55. Congenital Infection
Congenital transmission is possible in
both acute and chronic phase ,causing
myocardial and neurological damage in
the foetus

56. Laboratory Diagnosis
Diagnosis is done by demonstration of
T.cruzi in blood or tissues or by serology
Microscopy
• Microscopic examination of fresh
anticoagulated blood or buffy coat is the
simplest way to see motile organisms
• In wet mount,Trypomastigotes are fainly
visible but their snake- like motion against
RBC’s makes their presents apparent

57. • Trypanomastigotes can also be seen in
thick and thin peripheral blood smear,
stained with Giemsa stain
• Microhematocrit containing acridine
orange as a stain can also be used

58. Culture
Novy, Neal and Nicolle (NNN) medium or
its modifications are used
• Medium is inoculated with blood and
other specimens and incubated at 22-24
deg C
• Fluid from culture is examined
microscopically by 4 th day and then
every week for 6 weeks
• Epimastigotes and Trypomastigotes are
found in culture

59. Animal Inoculation
Blood or CSF is inoculated
intraperitoneally into mice or guinea
pigs

60. • Xenodiagnosis
ˉ Is the method of choice in suspected chagas
disease,if other examinations are
negative,especially during the early phase of
disease onset.
ˉ The reduviid bugs are reared in a
trypanosome-free laboratory and starved for
2 wks, then fed on patients blood.if
trypomastigotes are ingested ,they will
multiply and develope into epimastigotes
and trypomastigotes,which can be found in

61. • Histopathology
ˉ Biopsy examination of lymphnodes and
skeletal muscles and aspirate from
chagoma may reveal amastigotes of
T.cruzi

62. Serology
Consits of antigen detection and antibody
detection
Antigen detection
ˉ ELISA has been developed for detection of
antigen.
ˉ Detected in urine and sera in patients

63. • Antibody detection
Antibodies(IgG)may be detected by the
following tests.
ˉ IHA
ˉ CFT(Machado-Guerreiro test)
ˉ ELISA
ˉ IIF
ˉ Direct agglutination test(DAT)
ˉ Chagas Radio Immune Precipitation
Assay(RIPA)-Highly specific and sensitive
test.

64. • Intradermal test
ˉ Antigen cruzin is used to detect
delayed hypersensitivity
• Molecular diagnosis
ˉ PCR is used to detect trypomastigotes
in blood.

65. Treatment
• No effective specific treatment is
available
• Nifutrimox and benznidazole- used with
some success in both acute and
chronic chaga’s disease,kills only
extracellular form
• Dose- nifutrimox 8-10 mg/kg adult
15mg/kg children
benznidazole 5-10 mg/kg orally
for 60 days

66. Prophylaxis
• Application of insectiside to control the
vector bug.
• Personal protection using insect
repellent and mosquito net.
• Improvement in housing and
environment to eliminate breeding
places of bugs .