The Geohelminths Flashcards
types of geohelminths
- ascaris lumbricoides: large roundworm
- necator americanus: hookworm
- ancylostoma duodenale: hookworm
- trichuris trichiura: whipworm
- stronglyoides stercoralis
what type of cell is c. elegans?
metazoan, multicellular parasite
developmental stages of phylum nematoda
egg -> L1 -> L2 -> L3 -> L4 -> adult
four moults; L = larvae
where is more prevalent ascaris lumbricoides?
in tropical and subtropical regions and areas with inadequate sanitation
how long can ascaris egg can survive in soil?
for 7 years
why can the egg survive so long in soil?
it has a hard coat - they are highly robust
they stop development at L3 and wait to infect a new person
what does ascaris lumbricoides infect?
the human intestine
how many eggs does a female may produce?
200,000 eggs per day
cycle of infection of ascaris
- eggs swallowed
- larvae hatch
- invade the intestinal mucosa
- carried via the portal
- goes to systemic circulation to the lungs
action of the ascaris in lungs
- they mature further in the lungs (10 to 14 days)
- penetrate the alveolar walls
- ascend the bronchial tree to the throat
- larvae are swallowed
how long do worms live?
1 to 2 years
what activates the eggs?
digestive enzymes
which two places if infected by the worms can cause death?
- in gut - they rupture the gut walls
- bile duct/ pancreatic duct - blocks them and kills the host
- lungs
classes of people more likely to die from ascaris?
people with high IgE and eosinophils
why is there a higher incidence of infections in areas where there are periodic rains?
because the rain liberates the worms from the soil, hence increase the infections
what type of disease is Löffler’s syndrome?
a type I immune hypersensitivity - similar to an allergic reaction
what type of antibodyis associated with Löffler’s syndrome?
IgE, also associated with natural immunity and protection system against macroparasites
human species of hookworms
nectar americanus
ancylostoma duodenale
hookworm cycle
- eggs in faeces (diagnostic stage)
- rhabditiform larva hatches
- filariform larva
- filariform larva penetrates skin (infective stage)
- adults in small intestine
development of hookworm infection
- eggs hatch in 1 to 2 days ( L1) - they are ready to hatch as soon as they are laid
- after 5 to 10 days they become infective - L3
- infective larvae can survive 3 to 4 weeks
- penetrate the skin -> heart -> lungs -> pharynx -> intestine
- most adult worms eliminated in 1 to 2 years, but can survive for several years
where does the hookworms breed?
in the stomach
why do the infected person may die from bleeding?
because the worm moves from side to side and everywhere they go, they bite. hosts then loses blood every time the worm bites them.
how do pigs and humans get infected by trichinella spiralis?
pigs - ingestion of meat scraps or animals
humans - ingestion of undercooked meat (esp. pork)
where does the trichinella spiralis live inside the body?
in the gut, but the superficial layer - doesn’t go to tissues
cycle of trichinella spiralis
- ingestion of undercooked meat
- larva released in the small intestine
- adults in small intestine
- larva deposited in mucosa
- encysted larva in started muscle - larva in a capsule and can’t get rid of it
how does trichinella spiralis kill the cells?
it enters the cell, then the nucleus degrades and the cell finally disappears
