Protozoa Flashcards
Describe the human stages of the leishmania life cycle
Sandfly takes a blood meal
Promastigotes are phagocytised by macrophages
Promastigotes transform into amastigotes inside macrophages
Amastigotes multiply in cells (including macrophages) of various tissues
Describe the sandfly stages of the leishmania life cycle
Sandfly takes a blood meal
Ingestion of parasitised cell
Amastigotes transform into promastigote stage in midgut
Divide in midgut and migrate to proboscis
Sandfly takes a blood meal
Countries with cases of leishmaniasis
India, Bangladesh, Brazil and Sudan
What are the clinical symptoms of leishmaniasis
Anaemia, low white blood cell count and low blood platelet count
What is the possible length of the incubation period of leishmaniasis
1-2 months to 10 years
What are the parasitological methods of diagnosis of visceral leishmaniasis
Seeing amastigotes in aspirated from spleen, lymph node, bone marrow, or liver
Promastigotes in cultures derived from aspirates
This required splenic aspirate - large needle through the abdomen I to the spleen
What is one method used to increase sensitivity of microscopy
By the cultivation of the biopsy specimens this requires specialised aseptic conditions; fume hood, culture expertise etc
What is the antigen detection methods of diagnosis of visceral leishmaniasis
KAtex urine test
Describe the KAtex urine test
Latex agglutination test using latex particles coated with antibodies against leishmania antigen found in urine of VL patients
Non-invasive method
Sensitivity can be between 47 and 95%
Specificity can be between 83 and 100%
Describe the direct agglutination test
DAT test relies on the agglutination of the human antibodies and parasite antigen
During infection with VL antibodies are produced against the surface antigens of the invading parasites
The DAT detects antibodies to the parasite in the blood or serum of patients
The DAT uses a freeze-dries suspension of trypsin-treated, fixed and strained L. Donovani Promastigotes (from a culture)
In the absence of antibodies to leishmania the DAT antigen accumulates at the bottom of the plate to form a blue spot a negative result
If antibodies to leishmania are present, then the antigen remains a pale blue solution to a positive result
What are the pros and cons of a DAT test
Easy to read and does not require any equipment, is considered by many an ideal field test
Reproducibility problems have been observed under field conditions due to thermal instability of the antigen and readying problems
Freeze-dried antigen has helped to solve stability problems
However, tendency to false positives and problems with antigen batch variability
What are the molecular biology used to diagnose visceral leishmaniasis
PCR and NASBA (nucleic acid sequence-based assay)
What causes giardiasis
Giardia duodenal is (flagellated enteric protozoan)
What causes a giardiasis infection occur
By ingestion of cysts in contaminated water, food or faecal-oral route
In the small intestine, excystation releases trophozoites (each cyst produces two trophozoites) that multiply by longitudinal binary fission
They can be free in the gut lumen or attached to the mucosa using a sucking disk
Encysation occurs as the parasites move towards the colon
Cysts passed in the faeces
Parasitological diagnosis of giardiasis
Trophozoites and cysts in stool
