Human African trypanosomiasis and Leishmaniasis Flashcards
what type of parasite is Kinestoplastida?
parasitic protozoa
which species of Kiestoplastida infect human?
- Leishmania species
2. Trypanosoma species
parts of the kinestoplastida
flagellum, kinetoplast (like cytoplasm) and nucleus
do trypanosome species affect only humans?
no - they cause disease in both man and animals
what species of trypanosomes affect domestic animals?
trypanosoma vivid, trypanosoma congolenesl and trypanosoma brucei brucei
what species of trypanosoma affect humans?
trypanosoma brucei gambiense and trypanosoma brucei rhodesiense
which is the vector which transmits human african trypanosomiasis?
tsetse fly (glossina)
what determines the distribution of african trypanosomiasis?
the vector - tsetse fly vector (genus glossina)
how are trypanosomes transmitted between people?
via the bite of infected tsetse flies
what form of disease cause T. b. gambiense?
causes a chronic form of the disease - it can pass several years between infection and death
- endemic in west and central africa
what form of disease cause T. b. rhodesiense?
causes an acute form of the disease - just weeks between infection and death
- endemic in east and southern africa
how are T. b. gambiense and rhodiense similar?
they are morphologically indistinguishable, but they can be differentiated at the DNA level
what parts of the body do the parasite injected by the tsetse fly infect in the human body?
the blood and lymphatic systems, later the central nervous system and the brain
what do late stages of the african trypanosomiasis disease involve?
brain disorders including changes to sleep wake patterns - sleeping sickness
how do parasites infect the human after an immune response?
when the parasite is injected in the human body, it grows for about a week while the immune system confirms their foreign status and then mounts a fatal antibody response.
some parasites change their coat and can grow while the immune system checks again their status, so they can attack again.
what is the surface of trypanosome covered by?
is covered in a densely packed “variant surface glycoprotein” (Vsg) coat
what do the proteins in the coat covering the trypanosome form?
they form homodimers
how do they form homodimers?
they anchor to the membrane via a glycosyl phosphatidyl inositol (dpi) anchor
what does the protein coat do?
does not restrict access of low molecular weight solutes to the membrane
it prevents complement proteins fixing at the trypanosome’s plasma membrane
how many vsg coats do they express at a time?
they have the potential to express over 1,000 msgs, but express only one at a time with complex gene expression regulation
what does the chemotherapy of human african trypanosomiasis (HAT) depend on?
on 5 drugs
- suramin, pentamidine, mearsoprol, eflornithine and nifurtimox
what are suramin and pentamidine useful for?
useful against early stage disease - before invasion of the CNS
what are melarsoprol and eflornithine useful for?
useful against late stage disease - after CNS invasion
how is eflornithine used?
in combination with nifurtimox
control methods for tsetse flies
insecticide spraying, tsetse trapping and sterile male release
what causes Leishmaniases?
parasitic protozoa of the genus Leishmania
how does leishmania affect the body
parasites of different species affect different parts of the body
types of Leishmaniases
cutaneous, mucutaneous, visceral, post tala-azar dermal syndrome
what do leishmania parasites invade?
they invade macrophages
what do leishmania parasites become after invading the macrophages?
they become amastigote forms proliferating inside macrophages
how are leishmania parasites transmitted?
by tiny bloodsucking sandflies
what animals serve as a reservoir host for leishmaniasis?
dogs - leishmaniasis is zoonotic
stages of leishmaniasis infection ?
- sandfly stages (1, 5,6,7,8,)
2. human stages (2,3,4)
Human stages of leshmaniasis (after biting of sandfly)
- promastigotes are phagocytise by macrophages
- promastigotes transform into amastigotes inside macrophages
- amastigotes multiply in cells (including macrophages) of various tissues
sandfly stages of leishmaniasis
- sandfly takes a blood meal (injects promastigote stage into the skin)
- -human is infected– - sandfly takes a blood meal (ingests macrophages infected with amastigotes)
- ingestion of parasitised cell
- amastigotes transform into promastigote stage in midgut
- divide in midgut and migrate to proboscis
leshmaniasis treatment
- antimony based drugs remain first line (but toxicity and increasing resistance are limiting use)
- amphoteric in B, miltefosine, pentamidine and paromomycin (have variable efficacy depending on species of Leishmania)
leshmaniasis vaccines?
no vaccine currently exists
how is cutaneous leishmaniasis treated?
this form of infection is usually self-healing, followed by roust immunity thus it is possible vaccines will be possible
