Tissue Worms Flashcards

Question

What causes Lymphatic filiariasis?

Answer 1

Nematode worms: - Wuchereria bancrofti - Brugia malayi

Answer 2

Mosquitos: - Anopheles, Culex, Aedes (Pacific islands) - Mansonia (Brugia malayi)

Answer 3

- 120 million people in 80 countries (40 million disfigured) - 1/3 in India, 1/3 in Africa - Remainder in South Asia, Pacific & Americas

Answer 4

Adult worms live in the lymphatic system (4-6 years) - Producing millions of microfilariae • Cause local inflammation, fibrosis, obstruction (lymphatic filariasis) • Eosinophilia; later, enlargement and thickening of the skin (elephantiasis)

Answer 5

A network of vessels that conveys extracellular tissue fluid. Allows transportation of nutrients to every cell as lymph via the thoracic duct, back to the bloodstream It consists of fine, blind-ended lymphatic capillaries which unite to form lymphatic vessels Vessels have valves to prevent backflow of lymph At various points along these vessels are lymph nodes. Lymph is similar in composition to plasma, but contains less protein, some cells (mainly lymphocytes) • Milky in appearance When lymphatic vessels become inflamed they can sometimes be seen as red streaks in the skin

Answer 6

Mosquito takes blood meal (L3 larvae enter skin) Develop into adults in lymphatic system Adults produce sheathed microfilariae that migrate into lymph and blood channels Mosquito takes blood meal (ingests Microfilariae) Microfilariae shed sheaths, penetrate mosquito’s mid-gut and migrate to thoracic muscles Develop into L1 larvae Develop into L3 larvae Migrate to head and mosquito’s proboscis

Answer 7

* Male – 4 cm long | * Female – 8-10 cm long

Answer 8

Adult worms live in lymphatic system. They produce microfilaria that collectively damage the lymphatic system

Answer 9

Microfilariae travel around the bloodstream at night and hide in the lung capillaries by day

Answer 10

Hydrocoele (enlargement of the scrotum) occurs in 50% of men infected

Answer 11

The standard method for diagnosing active infection is the identification of microfilariae in a blood smear by microscopic examination. The microfilariae that cause lymphatic filariasis circulate in the blood at night (called nocturnal periodicity). Blood collection should be done at night to coincide with the appearance of the microfilariae, and a thick smear should be made and stained with Giemsa or hematoxylin and eosin. For increased sensitivity, concentration techniques can be used. Serologic techniques provide an alternative to microscopic detection of microfilariae for the diagnosis of lymphatic filariasis. Patients with active filarial infection typically have elevated levels of antifilarial IgG4 in the blood and these can be detected using routine assays. Binax® Now® card test can be used to give rapid result, and can be performed by untrained personnel

Answer 12

Albendazole (400mg single dose) • Causes polymerisation of worm β-tubulin and microtubule formation Other drugs can be used: Ivermectin / diethylcarbamazine (DEC) • 150 μg/kg / 6 mg/kg (Single doses) • DEC/Ivermectin used in eradication campaigns • Given for free by manufacturer (They make their money as it is also used to treat animal infections [lice, fleas]) • Doxycycline / Tetracycline can also be used

Answer 13

Both target the microfilariae (MF) - Not adults (Usually combines with albendazole) Ivermectin: - Hyperpolarises Glutamate sensitive chloride channels - Blocks nerve transmission & muscle function in the worm - Paralyses it DEC – Mechanism unknown

Answer 14

River Blindness

Answer 15

Was the world's second leading infectious cause of blindness, particular in: • Africa (30 countries) • Arabian peninsula • Americas Often associated with big river system 120 million people world-wide at risk: • 96% in Africa • 18 million infected • 270 000 blind

Answer 16

* Onchocerca volvulus * Parasitic nematode * Produce microfilariae

Answer 17

Serious visual impairment, including blindness • Microfilariae penetrate the eye • Sets up an immune response damaging the eye ``` Elephantiasis: • Lymphadenitis • Resulting in elephantiasis of genitals - Hanging groin • Damage to inguinal lymph vessel / node • Bubo (buboes) ``` ``` Skin problems • Rashes, lesions, & intense itching • Caused by microfiliariae • Leopard skin (di-pigmentation) • Lizard skin (wrinkled) • Elephant skin (thickened) • Nodules ```

Answer 18

* Simulium spp - Black fly (Buffalo gnat) * Lay eggs in flowing water * Larvae attach to rocks

Answer 19

Blackfly (genus Simulium) takes a blood meal (L3 larvae) enter bite wound Larvae enter subcutaneous tissues Adult worms develop in subcutaneous nodules Adults produce microfilariae: found in skin and lymphatics Blackfly takes a blood meal Microfilariae penetrate blackfly’s mid-gut and migrate to thoracic muscles L1 larvae develop L3 larvae develop L3 larvae migrate to head and blackfly’s proboscis

Answer 20

Nodulectomy • Removes adults therefore reducing number microfilariae released African Programme for Onchocerciasis Control (APOC) • Involves spraying insecticide into breeding sites Donation of Ivermectin (Mectizan) by Merck & Co., Inc • 2 doses 6 months apart repeated every 3 years • Paralyses the microfilariae • Stops progression towards blindness

Answer 21

``` Eradication has looked likely, however: • Recent study from Ghana published in the Lancet 2007 suggested resistance is emerging • Confirmed in 2011 in PloS • Female worms are becoming resistant ```

Tissue Worms Flashcards

(45 cards)