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6. Parasitic diseases
Human african trypanosomiasis
(sleeping sickness)
H um an african trypanosom iasis ( H A T ) is a zoonosis caused b y protozoa
( trypanosom es) , transm itted to h um ans th roug h th e bite of a tsetse fly ( Glossina) .
T ransm ission by contam inated blood transfusion and transplacental transm ission are
also possible.
T h e d isease is found only in sub-Sah aran A frica. T h ere are tw o form s: Trypanosoma
brucei gambiense H A T in w estern and central A frica and Trypanosoma brucei rhodesiense
H A T in eastern and south ern A frica.
Clinical features
Inoculation m ay be follow ed by an im m ed iate local reaction (trypanosom al ch ancre).
T h is ch ancre arises in about 5 0 % of all rh od esiense but rarely in g am biense.
Gambiense HAT
– Incubation lasts from a few d ays to sev eral years.
– T h e first stag e ( h aem olym ph atic stag e) correspond s to th e h aem atog enous and6
lym ph atic d issem ination of th e parasite. Sig ns includ e interm ittent fev er, joint pain,
lym ph ad enopath y ( firm , m ob ile, painless lym ph nod es, m ainly cerv ical) ,
h epatosplenom eg aly and skin sig ns (facial oed em a, pruritus).
– T h e second stag e ( m ening oenceph alitic stag e) correspond s to th e inv asion of th e
central nerv ous system . Sig ns of th e h aem olym ph atic stag e reced e or d isappear and
v arying neurolog ical sig ns prog ressiv ely d ev elop: sensory d isturbances ( d eep
h yperaesth esia), psych iatric d isord ers (apath y or ag itation), d isturbance of th e sleep
cycle (w ith d aytim e som nolence alternating w ith insom nia at nig h t), im paired
m otor
functions ( paralysis, seizures, tics) and neuroend ocrine d isord ers ( am enorrh oea,
im potence).
– In th e absence of treatm ent: cach exia, leth arg y, com a and d eath .
Rhodesiense HAT
T h e first stag e is th e sam e as abov e, but th e incubation period is sh orter (< 3 w eeks),
th e
d isease ev olv es m ore rapid ly and sym ptom s are m ore sev ere. P atients often d ie of
m yocard itis in 3 to 6 m onth s w ith out h av ing d ev eloped sig ns of th e m ening o -
enceph alitic stag e.
In practice, g am biense and rh od esiense H A T can be d ifficult to d ifferentiate: e.g ., th ere
exist cases of acute g am biense infection and oth ers of ch ronic rh od esiense infection.
Laboratory
– D iag nosis inv olv es 3 steps for g am biense H A T (screening test, d iag nostic
confirm ation
and stag e d eterm ination) and 2 steps for rh od esiense H A T (d iag nostic confirm ation
and stag e d eterm ination).
– T h e recom m end ed screening test for T.b. gambiense infection is th e C A T T
( C ard
A g g lutination T est for T rypanosom iasis). It d etects th e presence of specific antibod ies
in th e patient‟s blood or serum .
Human african trypanosomiasis
(sleeping sickness)
H um an african trypanosom iasis ( H A T ) is a zoonosis caused b y protozoa
( trypanosom es) , transm itted to h um ans th roug h th e bite of a tsetse fly ( Glossina) .
T ransm ission by contam inated blood transfusion and transplacental transm ission are
also possible.
T h e d isease is found only in sub-Sah aran A frica. T h ere are tw o form s: Trypanosoma
brucei gambiense H A T in w estern and central A frica and Trypanosoma brucei rhodesiense
H A T in eastern and south ern A frica.
Clinical features
Inoculation m ay be follow ed by an im m ed iate local reaction (trypanosom al ch ancre).
T h is ch ancre arises in about 5 0 % of all rh od esiense but rarely in g am biense.
Gambiense HAT
– Incubation lasts from a few d ays to sev eral years.
– T h e first stag e ( h aem olym ph atic stag e) correspond s to th e h aem atog enous and6
lym ph atic d issem ination of th e parasite. Sig ns includ e interm ittent fev er, joint pain,
lym ph ad enopath y ( firm , m ob ile, painless lym ph nod es, m ainly cerv ical) ,
h epatosplenom eg aly and skin sig ns (facial oed em a, pruritus).
– T h e second stag e ( m ening oenceph alitic stag e) correspond s to th e inv asion of th e
central nerv ous system . Sig ns of th e h aem olym ph atic stag e reced e or d isappear and
v arying neurolog ical sig ns prog ressiv ely d ev elop: sensory d isturbances ( d eep
h yperaesth esia), psych iatric d isord ers (apath y or ag itation), d isturbance of th e sleep
cycle (w ith d aytim e som nolence alternating w ith insom nia at nig h t), im paired
m otor
functions ( paralysis, seizures, tics) and neuroend ocrine d isord ers ( am enorrh oea,
im potence).
– In th e absence of treatm ent: cach exia, leth arg y, com a and d eath .
Rhodesiense HAT
T h e first stag e is th e sam e as abov e, but th e incubation period is sh orter (< 3 w eeks),
th e
d isease ev olv es m ore rapid ly and sym ptom s are m ore sev ere. P atients often d ie of
m yocard itis in 3 to 6 m onth s w ith out h av ing d ev eloped sig ns of th e m ening o -
enceph alitic stag e.
In practice, g am biense and rh od esiense H A T can be d ifficult to d ifferentiate: e.g ., th ere
exist cases of acute g am biense infection and oth ers of ch ronic rh od esiense infection.
Laboratory
– D iag nosis inv olv es 3 steps for g am biense H A T (screening test, d iag nostic
confirm ation
and stag e d eterm ination) and 2 steps for rh od esiense H A T (d iag nostic confirm ation
and stag e d eterm ination).
– T h e recom m end ed screening test for T.b. gambiense infection is th e C A T T
( C ard
A g g lutination T est for T rypanosom iasis). It d etects th e presence of specific antibod ies
in th e patient‟s blood or serum .
