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

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 -

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

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

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)

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

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

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

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

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)

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 1.5-2.7 million deaths (90% Africa) increasing problem (re-emerging disease) resurgence in some areas drug resistance ( mortality) P. falciparum P. vivax P. ovale P. malariae

Life Cycle transmitted by Anopheles mosquitoes sporozoites injected with saliva sporozoites invade liver cells undergo an asexual replication 1000-10,000 merozoites produced hypnozoites and relapses in Pv and Po

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

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

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

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

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 ….

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%

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

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

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

Selected Anti-Malarials

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)