helminths Flashcards
Definition
Nematodes
Trematodes
Cestodes
Nematodes – roundworms (filaria)
Trematodes – flukes or flatworms
Cestodes – tapeworms
Definitive host
Intermediate host
Paratenic hosts
Accidental/dead end host
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
Enterobius vermicularis type of worm
Pinworm
Threadworm
Enterobius vermicularis epidemiology and clinical presentation
scratch bum suck thumb
females lay eggs in perianal region, ingest –> reinfection
- pruritis ani
Enterobius vermicularis diagnosis
scotch tape test
Trichuris trichiura type of worm
Threadworm
Trichuris trichiura epidemiology
Eggs passed in faeces, swallowed, larvae develops into adult in GIT
Trichuris trichiura causes?
Bloody stool, rectal prolapse, abd. pain
Trichuris dysentery syndrome: chronic diarrhea w growth retardation
Trichuris trichiura diagnosis
Eggs in faeces
Ascaris lumbricoides type of worm
large intestinal roundworm
Ascaris lumbricoides epidemiology
eggs passed in faeces, swallowed, hatch in duodenum
Ascaris lumbricoides causes?
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
Ancylostoma duodenale, Necator americanus type of worm
hookworms
Ancylostoma duodenale, Necator americanus epidemiology
soil
Ancylostoma duodenale, Necator americanus causes?
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
Strongyloides stercoralis epidemiology
Alternation between free-living and parasitic cycles
Adult female in GIT produces eggs, develop into larvae in GIT, exit in faeces
Strongyloides stercoralis causes?
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
Strongyloides stercoralis diagnosis?
Microscopy larvae in faeces and sputum, not very sensitive
PCR
Toxocara canis (dog) and catis (cat) mode of transmission and clinical presentation?
diagnosis?
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
Filariae facts
thin, threadlike
deworm your pets
Wuchereria bancrofti transmission and causes what?
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)
Brugia malayi type of worm
Malayan filariasis
Symptoms similar to wucheria bancrofti
Tropical pulmonary eosinophilia causes what?
Cryptic lymphatic filarial infection microfilaria almost never seen in blood
Pulmonary sympt. and high eosinophilia
- Cough, wheeze
Do serology
Loa Loa causes what?
Loaisis
Worm may pass across conjunctiva (irritation, pain, swelling)
Painful or itchy swellings in sc tissues
Serology
Onchocerca volvulus causes what?
river blindness onchocerciasis
do skin snip, examine for motile mf
Dracunculus medinensis
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