lecture 16- protozoa, kinetoplastids Flashcards
what unique organelle do kinetoplastids have?
kinetoplast
kinetoplast = …
a disk-shaped mass of circular DNA inside a large mitochondrion genome
kinetoplastid DNA is relatively …
abundant
what kind of DNA makes up the kinteoplastid genome?
ktDNA
what organelle is ktDNA within?
the mitochondria
what are the two types of ktDNA?
- maxi-circles: encode several mitochondria genes and are more or less equivalent to the mtDNA
- mini-circles: heterogenous and rapidly evolving; DNA encode guide RNAs responsible for RNA editing
what is true about mRNAs expressed from maxi-circles?
- they require extensive RNA editing, done by several multi-protein complexes with information coming from small guide RNAs (gRNAs)
- gRNAs serve as the template for editing
what can mini-circle DNA be used for?
parasite detection and differentiating isolates
what is the glycosome and its function?
a peroxisome-like organelle in which glycolysis occurs
what are the four major morphological forms found in kinetoplastids that cause human disease?
- trypomastigote
- amastigote
- promastigote
- epimastigote
leishmania
zoonotic protozoan parasites that cause a disease known as leishmaniasis
how is leishmania transmitted?
by the bite of certain species of sandflies
how many species of leishmania infects humans?
21 out of 30 species
different species of leishmania are …
morphologically indistinguishable
L. donovani causes …
visceral leishmaniasis
L. tropica causes ..
cutaneous leishmaniasis
L. braziliensis causes …
mucocutaneous leishmaniasis
how many countries has leishmaniasis been found in?
88 countries
where is L. donovani most prevalent?
Asia and Africa
where is L. tropica most prevalent?
Asia, Africa and Mediterranean
where is L. braziliensis most prevalent?
Central and South America
more than 90% of the world’s cases of visceral leishmaniasis are in …
India, bangladesh, nepal, sudan and brazil
what kind of life cycle does Leishmania acquire?
digenetic life cycle
what are the 2 morphological forms of Leishmania?
- promastigote, found in the sandfly vector
2. amastigote, in the host (humans)
what is the pathology of Leishmaniasis?
pathogenesis is due to an immune reaction to the pathogen, particularly cell mediated immunity
what does a laboratory examination of leishmaniasis mark?
a marked decrease in white blood cells with relative increase in monocytes and lymphocytes, reduced platelets and anemia
in leishmaniasis, …. are extremely elevated in a first infection
IgM and IgG levels
What parts of the body do cutaneous leishmaniasis affect?
- generally self-healing
- skin
- mucous membranes
what parts of the body do visceral leishmaniasis affect?
- fatal
- liver
- spleen
- bone marrow
cutaneous leishmaniasis
- the most common form of leishmaniasis
- characterized by one or more sores/ulcers, papules or nodules on the skin
- organism multiplies locally producing a skin nodule 2-8 weeks after the bite
what species of leishmania causes mucocutaneous leishmaniasis?
L. braziliensis
why is mucocutaneous leishmaniasis so dangerous?
- unlike cutaneous leishmaniasis, it can metastasize causing the lesions to spread to mucoid tissues (oral, pharyngeal and nasal) , which lead to severe deformity
- may occur months to years after original skin lesion
what species of Leishmania cause visceral leishmaniasis?
L. donovani, L. donovani infantum (old world), L. donovani chagasi (new world)
what are the epidemiological features of L. donovani?
affect people of all ages, L. donovani infantum affects young children and infants
…. leishmaniasis is the most severe form of leishmaniasis and may be fatal if left untreated
visceral
patients with … should be considered for visceral leishmaniasis
chronic fever
why is there rarely a local lesion in visceral leishmaniasis?
L. donovani organisms in VL are rapidly eliminated from the site of infection. They localize and multiply in the mononuclear phagocytic cells of spleen, liver, lymph nodes, bone marrow, intestinal mucosa and other organs
symptoms of visceral leishmaniasis
splenomegaly, swollen abdomen, severe muscle wasting, and jaundiced hands
how is leishmaniasis diagnosed?
- evaluation of the history of exposure to sandflies
- biopsy is required
- examination of Giemsa-stained slides of the relevant tissue (most commonly used to detect the parasite)
what is the treatment for Cutaneous/mucocutaneous leishmaniasis?
sodium stibogluconate - antimony containing drug with many serious side effects
what is the treatment for visceral leishmaniasis?
liposomal amphotericin-B - an antifungal medication
-causes severe and potentially lethal side effects
what are ways to prevent leishmaniasis?
- suppress the reservoir - dogs, rats, gerbils, other small mammals and rodents
- suppress the vector- sandfly, control measures involve house spraying
- prevent sandfly bites
- most important at night
- wear protective clothing
- use insect repellant
- use permethrin treated bed nets
What disease is trypanosomes responsible for?
trypanosomiasis - sleeping sickness
what do trypanosomes mainly infect?
most types of domestic livestock, many wild animals and man
what kind of fly are trypanosomes transmitted in?
tsetse fly, of the genus Glossina
what species of trypanosomes cause West African sleeping sickness
trypanosoma brucei gambiense
what species of trypansomes cause East African sleeping sickness?
trypanosoma brucei rhodesiense
what animal does Trypanosoma brucei brucei infect?
antelopes and other african ruminants (cattle, horses, camels)
what is the disease T. brucei brucei cause?
nagana - a type of sleeping sickness in animals
what is the affect of nagana in African ruminant animals?
reduce the growth rate, milk productivity, and strength of farm animals, leading to eventual death of the infected animals
the trypanosomes of equines and of camels are transmitted not by tsetse flies, but by..
direct blood contact during copulation or by biting insects such as horse flies that probe several animals one after the other
how many cases a year of trypanosomiasis are there?
about 300,000 new cases each year
humans are the main reservoir for what species of trypanosomes?
T. brucei gambiense
who are the main reservoirs for T. brucei rhodesiense?
wild game animals and cattle
how can T. brucei be transmitted in humans?
- mother to child infection
- blood transfusion
- sexual contact (rare)
- laboratories: accidental infections, although this is uncommon
Where is T. b. gambiense found?
central and western Africa
what is the effect of T. b. gambiense infection?
causes a chronic conditions that can extend in a passive phase for months or years before symptoms emerge
what species of T. b. gambiense chronic infection, is responsible for the acute form?
T. b. rhodesiense
where is T. b. rhodesiense found?
southern and eastern Africa
how is the infection of T. b. rhodesiense different from T. b. gambiense?
its infection emerges in a few weeks and is more virulent and faster developing
what is unique about African trypanosome’s life cycle?
the whole life cycle has extracellular stages
how does trypanosoma avoid the host’s immune response?
using antigen variation
what is antigen variation?
the process of a parasite changing its surface protein. in the case of trypanosomes, antigen variation is used by variation of the variant surface glycoproteins (VSGs)
what do Trypanosomes do with the VSGs during antigen variation?
parasite produces and covers its own plasma membrane with VSGs. as host’s antibodies attack the parasite, it changes its expression to the new VSGs and masks itself from the body’s natural defence mechanisms against foreign particles
T. brucei gambiense invades the …
CNS initiating a chronic, sleeping-sickness
T. brucei rhodesiense affect on humans?
rapid weight loss, heart involvement, and death
what is the diagnosis on african trypanosomiasis?
demonstrating trypanosomes by microscopic examination of lymph node aspirates, blood, bone marrow or, in the late stages of infection, cerebrospinal fluid
how are motile trypanosomes found in diagnosis?
using a wet preparation, fixing a smear stained with Giemsa and examined under the microscope
what is the treatment for African Trypanosomiasis?
the drug regimen depends on the infecting species and the stage of infection.
- pentamidine and suramin are used to treat the hemolymphatic stage of West and East African Trypanosomiasis
- Melarsoprol is the drug of choice for late disease with CNS involvement
what is the prevention/control for african trypanosomes?
- attempts to control the tsetse fly vectors
- tracking of wild game animals
- selective breeding of cattle
what is Chagas disease?
caused by the protozoan parasite Trypanosoma cruzi. a zoonotic disease that can be transmitted to humans by blood-sucking triatomine bugs
trypanosoma cruzi can be transmitted through …
- blood transfusions
- organ transplantation
- transplacentally
- lab accidents (rare)
where does chagas disease (american trypanosomiasis) occur?
exclusively in the Americas particularly in poor, rural areas of Mexico, Central America, and South America
what is the vector for Trypanosoma cruzi
the triatomine bug
what is the pathology of infection of american trypanosomiasis?
chagas manifests in all hollow organs. infected individuals typically remain infected for life
what is the most recognized marker of acute Chagas?
the Romana’s sign, which includes swelling of the eyelids on the side of the face near the bite wound or where the bug feces were deposited
what are symptoms like in the early stage of American trypanosomiasis?
symptoms are mild and usually produce no more than local swelling at the site of infection
what happens as American trypanosomiasis progresses?
- serious chronic symptoms can appear, such as heart disease and malformation of the intestines
- if untreated, the chronic disease can be fatal
both … and …. stages are found in humans (American trypanosomiasis)
amastigotes and trypomastigote stages
what is the treatment for American trypanosomiasis (chagas disease) ?
- the drug of choice is benzimidazole
- currently no vaccine
how is American trypanosomiasis prevented/controlled?
- prevention focused on fighting the vector by using sprays and paints containing insecticides and improving housing and sanitary conditions in rural areas
- mosquito nets are recommended
- testing of blood donors since blood transfusion is the second most common transmission route of chagas disease
what protozoan species are kinetoplasts?
Trypanosoma and Leishmania (Flagellata genus)
