Lecture 8.0 - Other blood parasites Notes Flashcards
Sleeping sickness
African trypanosomiasis
Trypanosomiasis: Trypanosomes are a group of parasitic protozoa belonging to the genus Trypanosoma. These organisms are primarily found in blood and tissue fluids of vertebrate hosts, including humans and other mammals.
The 3rd subspecies, which is an important cause of animal trypanosomiasis
T. brucei brucei,
Name the 2 subspecies that cause human African trypanosomiasis.
- West African/Gambian
trypanosomiasis: riverine forest- provides suitablle environment for viral transmission since its promote survival of tsetse flies, reservoir- HUMAN - East African/Rhodesian trypanosomiasis is a zoonosis; transmission occurs in a savannah environment. Antelopes are major reservoir.
occurs at the
site of the infected tsetse fly bite
trypanosomal chancre
Discuss the features and the 2 stages of East African/Rhodesia trypanosomiasis
- Acute; short incubation period of (1-2 weeks)
Stage 1- haemolymphatic stage:
- myocarditis
- pancytopenia
- multi-organ failure
- ARDS-Acute Respiratory Distress Syndrome
TREAT STAGE 1 WITH SURAMIN
Stage 2: if stage 1 is not treated promptly and patient has
survived:
- meningo-encephalitic stage;
Rapidly fatal if not treated
TREAT SAGE 2 WITH MELARSOPROL
Discuss the features and the 2 stages of West African/gambien trypanosomiasis
- Long incubation period: months to years
- Gradual onset of stage 1 (slow and steady development of symptoms or the progression of a condition over a period of time)
*Typical sign of haemolymphatic stage:
posterior cervical lymphadenopathy
(Winterbottom’s sign)
TREAT STG 1 WITH SURAMIN OR PENTAMIDINE
- Eventually CNS is invaded: stage 2
*Slowly progressive loss of higher brain function, can take years but if untreated,
eventually unrousable coma and death
TREAT STAGE 2 WITH MELASOPROL OR EFLORNITHINE
Manifestations of terminal sleeping sickness
- coma,
- dehydration,
- pneumonia,
- malnutrition,
- bedsores,
- sepsis…..death
Done when checking for trypanosomes in the CSF
that indicate CNS involvement
Lumbar puncture
New drug for treatment of both West and East African trypanasomiasis
Fexinidazole – oral, non-toxic, effective in both types of
disease, all stages
what is the treatment for east african trypnosomiasis (T.B. rhodesiense)
Stage 1 (haemolymphatic): suramin
* Stage 2 (meningoencephalitic): melarsoprol
what is the treatment for west african trypanosomiasis?
West African trypanosomiasis (T. b. gambiense):
* Stage 1: suramin or pentamidine
* Stage 2: melarsoprol or eflornithine (+/- nifurtimox
Drug toxicity following melarsoprol administration
- fatal encephalopathy
- exfoliative dermatitis
Trypanasomiasis control
- Active case detection
- Prompt case treatment
- Insecticide spraying of
breeding sites - prophylactic pentamidine
- Tsetse traps: dark blue
and black cloth attracts
tsetse flies; they are then
killed by insecticides
impregnated in cloth - Release of laboratory-bred
sterile male tsetse flies:
compete with wild males
for females and reduce
population breeding rat
Advice for travellers to risk areas for trypanosomiasis
- Wear light colours, not
dark blue or black - Use insect repellents
- Close car windows
- NB If you get ill – tell the doctor
about that tsetse bite! - Like malaria, East African
trypanosomiasis is an emergency
Filariasis
parasitic disease caused by filarial worms
Name 3 types of filarial worms and the diseases they cause
- Wukhereria bancrofti: Caue lymphatic filariasis, also called elephantosis
- Onchorcerca valvus: omchorceciasis, also known as river blindness
- Loiasis: cause eye worm infection
Lymphatic filariasis
Commonly known as elephantiasis; is a neglected tropical disease caused by infection with parasitic worms known as wukhereria bancrofti.
- Adult worms live in the
lymphatic vessels
Agent of lymphatic
filariasis
Wuchereria bancrofti
*Wuchereria bancrofti is a parasitic nematode (roundworm) responsible for causing lymphatic filariasis, also known as elephantiasis. This parasitic infection is transmitted to humans through the bite of infected mosquitoes, primarily mosquitoes belonging to the genera Anopheles, Culex, and Aedes.
The mosquitos transmitting W. bancrofti
- anopheline
- and culicine mosquitoes
Discuss the Distribution of W. bancrofti
world-wide, in
tropics. Nocturnal periodicity in most places to
suit night-biting mosquitoes, diurnal in S. Pacific.
Irreversible lymphatic
filariasis
elephantiasis
Chyluria
Intestinal lymph fluid in urine due to blockage of abdominal lymphatics, which rupture into renal ducts and divert
the lymph into the urine.
life cycle of wucheria bancrofti, the agent of lymphatic filariasis
- mosquito takes first bite
-infective larvae develop in mosquito - mosquito takes 2nd blood meal
- larvae deposited on skin enter bite wound
- larvae enters lymphatics
- adult mature in lymphatics
- lymphadema/ elephantiasis
- microfilariae enter bloodstream
- peripheral blood
Impact of Wuchereria bancrofti infection on the scrotum
Early hydrocoele due
to blockage of
spermatic cord
lymphatics
what transmits w. bancrofti
anopheline and culicine mosquitoes
Discuss the distribution of onchocerciasis
Mainly West and Central Africa, some small foci in South and Central America
Loiasis
- Calabar
swelling. These are
transient subcutaneous
swellings, often where
the subcutaneous
tissue is thin e.g. over
wrist joint
Vectors of Loa loa
tabanid
flies, e.g. Chrysops species
Vector of Onchocerca volvulus:
blackly (Simulium sp.)
Location of adult worms in onchocerciasis infection
Onchocercal nodules over
bony prominences
Effects of onchocercal on the eye
Early keratitis; proceeds to
uveitis, retinitis and
blindness
What is onchocercal dermatitis?
Allergic reaction
to dead microfilariae, plus secondary bacterial infection from scratching
what are the treatment problems/ contraindications?
- Suramin, melarsoprol: toxic drugs, limited supplies,
prolonged courses required - Adverse reactions: common, may be severe and even fatal
- Some parasite strains are resistant
- Most are ‘orphan’ drugs: not profitable for drug companies
- Supply has improved in the 5 years: WHO provides free
service - Fexinidazole, if clinical trials are successful, promises to
