1. Blood and Tissue Protozoa
Mark F. Wiser
Department of Tropical Medicine
School of Public Health

2. Protozoa of Blood and Tissues
Organism
Vector
Trypanosoma gambiense and T. rhodesiense
Tse-tse fly
Trypansosma cruzi
Triatomine bugs
Leishmania
Sand flies
Plasmodium
Mosquitoes
Babesia
Ticks
Toxoplasma gondii -

3. Disease Causing Kinetoplastids
African trypanosomes
sleeping sickness
Trypanosoma cruzi
Chagas’ disease
S. and Central America
Leishmania species
leishmaniasis
focal distribution worldwide
Kinetoplast
Nucleus
KT = mitochondrial DNA

5. Disease Course and Symptoms
invasion of blood characterized by irregular fever and headache (acute stage)
T. gambiense can be self-limiting or progressing to a more serious disease (chronic)
includes invasion of lymphatics and CNS
parasites crossing blood-brain barrier result in CNS involvement and nervous impairment
described as meningoencephalitis
increased apathy and fatigue
confusion and somnolence
motor changes including tics, slurred speech, incoordination
convulsions, coma, death

6. Diagnosis and Treatment
Clinical Features
travel or residence in endemic area
irregular fever and enlarged lymph nodes
behavioral changes/mental symptoms
Laboratory Diagnosis
serological tests
demonstration of trypanosomes in blood, lymph node aspirates, cerebral spinal fluid
Early Stage
No CNS involvement
suramin
pentamidine
excellent prognosis
Late Stage
CNS involvement
melarsoprol
eflornithine (resurrection drug)

7. Trypanosoma cruzi and Chagas Disease
Transmitted by triatomine bugs
Inefficient transmission (parasite in feces of bug)
Associated with infestation of houses with triatomines (rural poverty)
Urban transmission associated with blood transfusions
Leading cause of cardiac disease in S. and central America

8. Clinical Course of Chagas
Acute Phase
active infection (1-4 months)
most are asymptomatic (children most likely to be symptomatic)
Indeterminate Phase
10-30 years of latency
seropositive with no detectable parasitemia
Chronic Phase
10-30% of infected exhibit cardiomyopathy
arrhythmias and conduction defects
congestive heart failure
thromboembolic phenomenon

9. Leishmaniasis
focal distribution throughout world, especially tropics and subtropics
new world: southern Texas to northern Argentina
old world: Asia, Africa, middle east, Mediterranean
transmitted by sand flies
new world: Lutzomyia
old world: Phlebotomus
parasite replicates within macrophages of vertebrate host
a variety of disease manifestations

10. Clinical Spectrum of Leishmaniasis
Cutaneous Leishmaniasis (CL)
most common form, relatively benign self-healing skin lesions (aka, localized or simple CL)
Mucocutaneous Leishmaniasis (MCL)
simple skin lesions that metastasize to mucosae (especially nose and mouth region)
Visceral Leishmaniasis (VL)
generalized infection of the reticuloendothelial system, high mortality

12. Diagnosis Treatment geographical presence of parasite
demonstration of parasite in skin lesion or bone marrow
delayed hypersensitivity skin test (cutaneous forms)
serological tests (visceral disease)
Treatment
pentavalent antimonials
amphotericin B (less toxic, expensive)
miltefosine (phase IV, no hospitalization)

13. MALARIA causative agent = Plasmodium species
4 human Plasmodium species
40% of the world’s population lives in endemic areas
primarily tropical and sub-tropical
3-500 million clinical cases per year
million deaths (90% Africa)
increasing problem (re-emerging disease)
resurgence in some areas
drug resistance ( mortality)
P. falciparum
P. vivax
P. ovale
P. malariae

14. Life Cycle transmitted by Anopheles mosquitoes
sporozoites injected with saliva
sporozoites invade liver cells
undergo an asexual replication
,000 merozoites produced
hypnozoites and relapses in Pv and Po

15. Life Cycle merozoites invade RBCs
repeated rounds of asexual replication
6-30 merozoites formed

16. Life Cycle some merozoites produce gametocytes
gametocytes infective for mosquito
fusion of gametes in gut
sporogony on outside of gut wall
asexual replication
sporozoites invade salivary glands

17. Clinical Features due to the blood stage of the infection
no symptoms during liver stage (~ incubation period)
characterized by acute febrile attacks (malaria paroxysms)
periodic episodes of fever alternating with symptom-free periods
manifestations and severity depend on species and host status
acquired immunity
general health
nutritional state
genetics

18. Malaria Paroxysm
paroxysms associated with synchrony of merozoite release
48 or 72 hr cycles
release of antigens, etc
 TNF-
temperature is normal and patient feels well between paroxysms
falciparum may not exhibit classic paroxysms
continuous fever
paroxysms become less severe and irregular as infection progresses

20. P. falciparum expresses ‘knobs’ on the surface of infected erythrocytes. Knobs mediate cytoadherence to endothelial cells.
the knobs are electron dense protuberances found on the erythrocyte membrane of infected cells
these knobs are believed to mediate cytoadherence--or binding to endothelial cells of the capillaries
this results in sequestration of the mature parasites in the deep tissues
This sequestration has two major advantages: 1) metabolic low O2 tensions, and 2) spleen advoidance
this sequestration is also responsible for the increased pathology associated with Pf.
for the remaining lecture I will discuss the molecular and cellular biology of knobs and this process of cytoadherence
lets first look at knobs ….

21. Falciparum Complications
sequestration of Pf-infected erythrocytes
immune evasion
primarily in brain, heart, lungs, and gut
leads to complications
cerebral malaria
consciousness ranges from stupor to coma
convulsions frequently observed
onset can be gradual or sudden
mortality 30-50%

22. metabolic effects, cytokines (eg, TNF-)
Possible
Pathophysiology
cytoadherence 
cerebral ischemia
hypoxia,
metabolic effects, cytokines (eg, TNF-)
coma
death

23. Severe falciparum malaria
potentially high parasitemias
sequestration
complex (and not fully understood) host-parasite interactions

24. Malaria Diagnosis symptoms: fever, chills, headache, malaise, etc.
history of being in endemic area
splenomegaly and anemia as disease progresses
microscopic demonstration of parasite in blood smear (distinguish species)
thick film: more sensitive
thin film: species identification easier
repeat smears every 12 hours for 48 hours if negative
antigen detection ‘dipstick’
ParaSight-F, OptiMal, etc

25. Selected Anti-Malarials

26. Treatment Strategies chloroquine sensitive (all species) chloroquine
CQ + primaquine (vivax/ovale)
chloroquine resistance (or unknown)
Fansidar, mefloquine, quinine, artemisinin derivatives
severe malaria
i.v. infusion of quinine or quinidine (or CQ, if sensitive)
i.v. artemisinin derivatives (if available)