Leishmania Flashcards
neglected tropical disease
leishmania
the Rose of Jericho
Leishmania
leishmania parasite
- single cell
- genus: Leishmania
- flagellate
- Trypanosomatidae family
vector for Leishmania
female sand fly
reservoirs for Leishmania
canines, rodents, humans
visceral leishmaniasis
most severe form of leishmania
often seen in countries with lower standards of healthcare
disease manifestations of leishmania
partly due to parasite = presence of RNA virus in parasite and immune response
life cycle of leishmania
2 stages
- stages in human and stages in sandfly (bio vector)
- human stage = starts after being bitten; sandflies inject saliva after bloodmeal; saliva = inflammation = calls macrophages bc parasites want to be phagocytosed to hitch a ride
- stage of parasite transmitted to humans via sand fly = promastigote
- will transform into amastigotes in macrophages (human stage)
- after bursting = sandfly stage starts; sand fly will ingest macrophages parasite
- amstogotes turn into promastogotes of sandfly
- will divide in midgut and go to proboscis waiting to take another bloodmeal
T or F. Leishmania has a sexual stage
F! not yet identified if there is one
leishmania disease manifestations
cutaneous or mucocutaneous
- L. major, L. tropica, L. aethiopica (most popular)
visceral leishmaniasis
- most severe
- often caused by L. donovani, L. infantum
- Ganges, southern Nepal, Bangladesh, Brazil, etc.
- black sickness, black fever, etc.
T or F. A single species of Leishmania can cause more than one type of syndrome
T! AND a syndrome can be caused by more than one species
it all depends on host-parasite interactions
two types of Leishmania promastigotes
these are in sandfly
- motile
- metacyclic
metacyclic vs motile Leishmania promastigotes
after amastigote stage in humans, motile promastigotes (non-infective insect form) will attach to insect gut, then transform to non-dividing infectious forms (metacyclic promastigotes)
transformation stimulus of Leishmania promastigotes depends on many factors, including…
temperature
risk factors Leishmania
- poor rural housing conditions, cracked walls, earthen floors
- poor sanitation = garbage attracts sandflies and dogs
- lack of accessible medicines
- if there is conflict = hard to perform vector control and movement of troops
- HIV
how to be a good reservoir for leishmaniasis
- Be in close contact with sandflies
- Should be susceptible to the infectious agent
- Should allow replication of the infectious agent to ensure delivery of large numbers to the victim
- Should ideally be the main source of food for the fly
- Disease should develop as a chronic disease giving time for the next transmission season
zoonotic leishmaniasis
rural areas
animals to humans via sandflies (mostly skin manifestations)
anthroponotic leishmaniasis
densely populated areas
- humans to humans and animals via vector (mostly visceral)
how does Leishmania alter the feeding behaviour of sand fly
it makes fly hungrier
- secretes gel-like substance that forms a plug that blocks stomach = allows multiplication of parasites
- nutrient and food doesn’t get through until gel is disturbed
- timing of blood feeding correlated to numbers of metacylic promastigotes (increased biting when numbers of infective parasites increase)
how does Leishmania adapt to 2 different hosts to complete its life cycle?
- STAGE SPECIFIC VIRULENCE DETERMINANTS = PHOSPHOGUCANS
> repeating GalB1, 4Manalpha1-PO4
> membrane bound lipophosphoglycan (LPG) important for delaying macrophage phagosome-lysosome fusion and for attachment/detachment from insect midgut epithelium
> number of repeating units vary in the different functional stages (ex: 15 repats in promastigotes increases to 30 repeats in metacyclic promastigotes, elongation facilitates detachment from gut)
what are phosphoglucans
they are secreted acid phosphatase + phosphoglycan
Leishmania promastigotes characteristics
increased surface glycoprotein GP63 (found on the parasite membrane and aids in internalization of promastigotes)
flagellated
prefers alk pH (sandfly gut)
prefers high glucose conctn
what is GP63
a zinc proteinase
also called leishmaniolysin