Microbiology Cheat Sheet
Filaria, Anaemia & Blood Parasites
Filaria, anaemia and blood parasites for NEET-PG: Wuchereria vs Brugia microfilariae, hookworm iron deficiency, kala-azar rK39, and Leishman-Donovan bodies.
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Filaria, Anaemia & Blood Parasites
Filaria, anaemia and blood parasites for NEET-PG: Wuchereria vs Brugia microfilariae, hookworm iron deficiency, kala-azar rK39, and Leishman-Donovan bodies.
This topic covers lymphatic filariasis and the microbial causes of anaemia, including hookworm, visceral leishmaniasis, and their laboratory diagnosis by blood and marrow examination.
High-yield lines
- Wuchereria bancrofti causes about 90 percent of lymphatic filariasis in India and is transmitted by Culex quinquefasciatus mosquitoes.
- Wuchereria bancrofti microfilariae are sheathed with tail nuclei that do not extend to the tip, and the sheath does not stain with Giemsa.
- Brugia malayi microfilariae have two distinct terminal and subterminal tail nuclei, and the sheath stains pink with Giemsa.
- Night blood collection between 10 PM and 2 AM captures nocturnal microfilarial periodicity, while the filarial antigen card test can be done at any time.
- Chronic filariasis causes lymphoedema, elephantiasis, hydrocele, and chyluria, while tropical pulmonary eosinophilia shows high IgE with microfilariae absent from blood.
- Diethylcarbamazine is the drug of choice for lymphatic filariasis, and doxycycline targets the Wolbachia endosymbiont for macrofilaricidal effect.
- Hookworm (Ancylostoma duodenale and Necator americanus) is the most important helminthic cause of iron-deficiency anaemia through chronic intestinal blood loss.
- Hookworm eggs are thin-shelled, oval, and segmented; species differentiation requires larval culture using the Harada-Mori technique.
- Leishmania donovani causes visceral leishmaniasis (kala-azar) with massive splenomegaly, pancytopenia, and hypergammaglobulinaemia.
- The rK39 immunochromatographic strip test is the field screening test of choice for visceral leishmaniasis in India, with over 95 percent sensitivity.
- Splenic aspirate has the highest sensitivity for visceral leishmaniasis but carries haemorrhage risk, so bone marrow aspirate is safer.
- Amastigotes (Leishman-Donovan bodies) appear within macrophages as small round bodies with a nucleus and rod-shaped kinetoplast on Giemsa stain.
- Parvovirus B19 infects erythroid progenitors via the P antigen, causing transient aplastic crisis in chronic haemolytic states.
- Diphyllobothrium latum, the fish tapeworm, competes for vitamin B12 in the ileum and can cause megaloblastic anaemia.
Mapped competency codes
- MI2.4
- MI2.6
Continue into the full chapter
This summary maps to MI2-cvs-and-blood.
Frequently Asked Questions
How is Wuchereria bancrofti distinguished from Brugia malayi on smear?
W. bancrofti has tail nuclei that do not reach the tip and an unstained sheath, while B. malayi has two discrete terminal tail nuclei and a pink-staining sheath.
When should blood be collected for filariasis?
Between 10 PM and 2 AM to coincide with nocturnal microfilarial periodicity, though the antigen card test works at any time.
What is the field test of choice for visceral leishmaniasis in India?
The rK39 immunochromatographic strip test, with over 95 percent sensitivity and specificity in the Indian subcontinent.
Which parasite is the leading helminthic cause of iron-deficiency anaemia?
Hookworm, through chronic intestinal blood loss from attachment of adult worms to the duodenal and jejunal mucosa.
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