helminths

Question 1

Definition
Nematodes
Trematodes
Cestodes

Answer 1

Nematodes – roundworms (filaria)
Trematodes – flukes or flatworms
Cestodes – tapeworms

Question 2

Definitive host

Intermediate host

Paratenic hosts

Accidental/dead end host

Answer 2

Definitive host: parasite reaches maturity or reproduces sexually

Intermediate host: harbour parasites during a development stage

Paratenic hosts: intermediate hosts but parasite does not develop further

Accidental/dead end host: host gets infected but does not contribute to parasite’s ongoing life cycle

Question 3

Enterobius vermicularis type of worm

Answer 3

Pinworm
Threadworm

Question 4

Enterobius vermicularis epidemiology and clinical presentation

Answer 4

scratch bum suck thumb
females lay eggs in perianal region, ingest –> reinfection

• pruritis ani

Question 5

Enterobius vermicularis diagnosis

Answer 5

scotch tape test

Question 6

Trichuris trichiura type of worm

Answer 6

Threadworm

Question 7

Trichuris trichiura epidemiology

Answer 7

Eggs passed in faeces, swallowed, larvae develops into adult in GIT

Question 8

Trichuris trichiura causes?

Answer 8

Bloody stool, rectal prolapse, abd. pain
Trichuris dysentery syndrome: chronic diarrhea w growth retardation

Question 9

Trichuris trichiura diagnosis

Answer 9

Eggs in faeces

Question 10

Ascaris lumbricoides type of worm

Answer 10

large intestinal roundworm

Question 11

Ascaris lumbricoides epidemiology

Answer 11

eggs passed in faeces, swallowed, hatch in duodenum

Question 12

Ascaris lumbricoides causes?

Answer 12

Larvae migrate through mucosa into bloodstream to inf. liver, heart, and lungs
Allergic rxn (asthma, rash)
- eosinophilia

Cough, fever, severe pneumonitis, abd. pain, peritonitis, appendicitis
Mechanical blockage of bile duct, intestine, pancreatic duct

Question 13

Ancylostoma duodenale, Necator americanus type of worm

Answer 13

hookworms

Question 14

Ancylostoma duodenale, Necator americanus epidemiology

Answer 14

soil

Question 15

Ancylostoma duodenale, Necator americanus causes?

Answer 15

Penetrates skin to bloodstream, through heart to lungs, coughed up and swallowed

Hookworm anemia: pale conjunctivae, heart failure

Cutaneous larva migrans/ creeping eruption: by dog hookworm, trapped in skin, unable to traverse human skin, die, inflamm. rxn, itchy for weeks

Question 16

Strongyloides stercoralis epidemiology

Answer 16

Alternation between free-living and parasitic cycles

Adult female in GIT produces eggs, develop into larvae in GIT, exit in faeces

Question 17

Strongyloides stercoralis causes?

Answer 17

Autoinfection cycle
- Some of the larvae produced from eggs in GIT become infectious –> penetrate GIT mucosa/perianal skin, migrate to GIT
- Can persist for decades

Question 18

Strongyloides stercoralis diagnosis?

Answer 18

Microscopy  larvae in faeces and sputum, not very sensitive

PCR

Question 19

Toxocara canis (dog) and catis (cat) mode of transmission and clinical presentation?

diagnosis?

Answer 19

Poorly cooked food

Retinal disease –> blindness (ocular larva migrans)
Heavier inf., many organs involved e.g. brains, liver, lungs = visceral larva migrans
- Fever, eosinophilia, hepatosplenomegaly, pneumonitis, convulsions etc

ELISA

Question 20

Filariae facts

Answer 20

thin, threadlike

deworm your pets

Question 21

Wuchereria bancrofti transmission and causes what?

Answer 21

Mosquito

Lymphangitis: adult worms live in lymphatic vessels

Elephantiasis: overgrowth of skin and sc tissues secondary to chronic lymphedema

Chyluria (milky white urine due to obstruction and local inflamm. of lymph vessels, rupture, urinary fistulae, present in preg./childbirth as well)

Question 22

Brugia malayi type of worm

Answer 22

Malayan filariasis

Symptoms similar to wucheria bancrofti

Question 23

Tropical pulmonary eosinophilia causes what?

Answer 23

Cryptic lymphatic filarial infection  microfilaria almost never seen in blood
Pulmonary sympt. and high eosinophilia
- Cough, wheeze

Do serology

Question 24

Loa Loa causes what?

Answer 24

Loaisis

Worm may pass across conjunctiva (irritation, pain, swelling)
Painful or itchy swellings in sc tissues

Serology

Question 25

Onchocerca volvulus causes what?

Answer 25

river blindness onchocerciasis

do skin snip, examine for motile mf

Question 26

Dracunculus medinensis

Answer 26

Guinea worm

Swallow crustacea containing larvae, penetrate gut wall, subcutaneous tissues, females break through skin to release larvae into water
Blister form and breaks open, pain, swelling, itching, arthritis, systemic sympt.

Immerse ulcer in clean water, remove worm through rolling