Trypanosomiasis Sleeping Sickness David Humber

Trypanosomes of Vertebrates T.corvi Corvids T.cruzi Humans, rodents, marsupials T.brucei spMan, ungulates T.lewisiRodents T.musculisRodents T.microtiVoles T.dionisiiBats T.equiperdum Equids Bone Marrow Heart muscle, autonomic ganglia Blood Lymphoid tissue Heart muscle Genitals SpeciesHostSite

African Sleeping Sickness Ngana South American Sleeping Sickness Chagas Disease

African Sleeping Sickness b Parasite - Trypanosoma brucei ssp Trypanosoma brucei rhodesiense Trypanosoma brucei gambiense b Vector - Tse Tse fly Glossina mortisans (Eastern Africa) Glossina palpalis (Western Africa)

Lecture Topics b The Parasite & Vector b The Life Cycle b Clinical Features b Diagnosis b Epidemiology b Chemotherapy & Control b Vaccination

Taxonomy b Phylum b Sub-Phylum b Class b Order b Genus Mastigophora Sarcomastigophora Zoomastigophora Kinetoplastidae Trypanosoma ? species of mammals, birds, reptiles and amphibians

The Parasite b Polymorphic spindle-shaped b Kinetoplast b Flagella & undulating membrane Trypomastigote Epimastigote

African Trypanosomiasis The Life Cycle HumanTse flyTrypomastigote StumpyMetacyclic IntermediateEpimastigote SlenderTrypomastigote

The Vectors Glossina 22 species - hatchet wing cell Shady habitat (20-30 o C) Viviparous - 12 offspring Diurnal feeders (1mg/sec) Parasite development days

Animal Reservoirs Sub species now thought to be zoonotic Largely ungulates

African Sleeping Sickness b Virulence b Reservoir b Zoonotic b Vector b Distribution Less More Human/animal Less More G.palpalis G.mortisans Western Africa Eastern Africa T.b.gambiense T.b.rhodesiense

Clinical Features Primary chancre - resolves 2-3 weeks Initial symptoms - fever & headaches Day time sleeping Tremors & Convulsions Coma & Death Enlarged cervical lymph nodes (T.b.g) Winterbottoms sign

Diagnosis b Direct microscopy Blood (T.b.r.) Lymph node aspirate (T.b.g.) Lumbar puncture (Late T.b.r. & T.b.g.) b Serology b Animal inoculation

Epidemiology 50 million at risk <20% under surveillance 20,000 new case/year Devastating epidemics 200 endemic foci

Distribution

Chemotherapy b Early stage - most recover Suramin Melasporol Pentamidine b Late stage - upto 5% relapse Only Melasporol –10% encephalitis - 5% fatal

Control Destruction of animal reservoir Vector Control Diagnosis & treatment

Immunology b Antibody b Inteferon

Parasitemia

Variable Surface Glycoprotein 60kd (450aa) glycoprotein (CHO 7-17%) C-terminal anchored in membrane Often as a dimer (alpha helix) Densely clustered 10 7 molecules/parasite Only epitopes in end third of N-terminal exposed Presented as topographical array T-independent antigen

VSG Constant & Variable regions Random rearrangement of N terminal end (2/3) Almost no homology between V VSG’s Except cystein residues S-S bonds Switching not initiated by IR But selected

Production of VSG Gene rearrangement Produces on expression linked copy (ELC) ELC transposed to telomeric end of chromosome - replacing existing gene Displaced gene lost Switch occurs every 10 6 divisions copie of different VSG’s in clone

VSG Specific IR 3-4 days post infection strong IgM response Trypanosome disappear within hours VSG specific IgG appears - not relevant IgM response often >IgG After several cycles VSG abs vanish But abs to invariant ags remain elevated

Trypanosome Elimination Antibody mediated Destruction by Kupffer cells Splenic macrophages minor role (cf malaria) Uptake - C3b - C3bi - direct? C mediated lysis not important Trypanosome destroyed within minutes

Immunoregulation No secondary response to VSG’s unless cured by chemotherapy Failure of 1ry or 2ndry response prior to death Non specific polyclonal activation Suppresser Macrophages Failure of Ag presentation Anti idiotype responses

Resistance and Virulence Spectrum of disease T. brucei sub species Host differences Independant of VSG

Vaccination Effective Antibody response Phagocytosis & killing but Cyclical parasitemia Antigenic variation not predicable