African trypanosomiasis

Question 1

HAT - epidemiology

Answer 1

36 countries in Sub-Saharan Africa

Incidence decreasing - WHO 2004 50,000-70,000 [1995 = 300,000-500,000]

Question 2

HAT - WHO targeted elimination

Answer 2

Annual incidence <1 per 10,000 individuals in 90% of endemic areas, and a global incidence of <2,000 per year

Question 3

HAT - distribution

Answer 3

Primarily disease of rural areas
Mammals [both domestic and wild] are reservoirs for the disease

Chronic = West Africa trypanosomiasis - T brucei gabiense

Acute = East African trypanosomiasis - T brucei rhodesiense

Question 4

HAT - vector

Answer 4

Tsetse fly [Glossina spp]

Riverine environment = Glossina palpalis

Savannah environment = Glossina morsitans

Question 5

HAT - parasite

Answer 5

Trypanosomiasis brucei

Protozoan parasite [kinetoplastid]
Inhabits bloodstream and other tissue spaces - extracellular parasite [compared to intracellular T cruzi]

Evade adaptive immune system by antigenic variation

Question 6

Trypanosomiasis brucei - lifecycle

Answer 6

Tsetse fly takes a blood meal and inject metacyclic trypomastigotes
Injected metacyclic trypomastigotes transform into bloodstream trypomastigotes - carried to other sites
Trypomastigotes multiply by binary fission in various body fluids

Tsetse fly takes a blood meal
Bloodstream trypomastigotes transform into procyclic trypomastigotes in tsetse fly’s midgut - and multiply by binary fission
Transform into epimastigotes and multiply in salivary gland
Undergoes genetic exchange in salivary glands

Question 7

Trypanosomiasis brucei - virulence

Answer 7

Non-human trypanosomes are lysed in human serum [apolipoprotein-L1 carried by TLF complexes]

T b rhodesiense = SRA [serum resistance antigen]

T b gambiense = TgsGP

Question 8

East African HAT [acute/rhodiense] - clinical presentation

Answer 8

Early stage = chancre arises at site of bit 50%

Later stage = parasites invade internal organs including CNS
-Can take 1-4 weeks
Symptoms:
-Severe headaches, sleeping pattern affected, personality changes, impaired function, weight loss, coma and death

Question 9

West African HAT [Chronic/gambiense] - clinical presentation

Answer 9

Early stage:
-Symptoms = lymphadenopathy, splenomegaly, fever, headache, malaise
-Winderbottom’s sing = enlarged posterior cervical LN
-Chancre rarely seen

Late stage = can take months/years
Symptoms:
-Severe hadaches, sleeping pattern affected, personality changes, impaired function, weight loss, coma and death

Question 10

HAT - diagnosis

Answer 10

Microscopy:
-Blood smear
-Blood concentration = microhaematocrit, DEAE anion exchange column
-LP and CSF [elevated WCC]

Serology:
-Card agglutination test for trypanosomiasis [CATT]
-Only for T b gambiense

Molecular:
-PCR, LAMP, ELISA

Question 11

West African HAT [Chronic/gambiense] - treatment

Answer 11

Early:
-Pentamidine IM
-Fexinidazole PO

Late:
-Eflornithine [NECT] IV + nifurtimox
-Fexinidazole PO

Question 12

East African HAT [acute/rhodesiense] - treatment

Answer 12

Early:
-Suramin IV

Late:
-Melarsoprol IV