Seminar 5: Nematodes 1 (Hookworms) Flashcards
List 3 intestinal hookworms for which humans are the main host
- Ancylostoma duodenale
- ancylostoma ceylanicum
- necator americanus
Give 1 intestinal hookworm that’s found in dogs and cats
ancylostoma caninum
T/F
Intestinal hookworms have the 2nd highest global morbidity burden of any parasite
true
Why do hookworms typically live in warm, moist climates?
Because they have a free-living larvae stage, so they require this climate
Ancylostoma spp molts __x in the human small intestine, and can live for up to ___ years in there!
2x
10
Explain the generalized path of a hookworm in the human host
penetrates skin
heart–> lungs –> trachea–> coughed up & reswallowed –> reaches small intestine (attached to intestinal wall)
How is ancylostoma canium transmitted in cats and dogs?
trans mammary transmission (mammary glands)
- accumulate and secrete in milk
Can humans get infected with ancylostoma canium?
Yes, sort of
- the worms can penetrate human skin, but can’t mature. They can only migrate in the sfc of the skin
= cutaneous larvae migrans - Can also be swallowed by humans –> causes eosinophilic enteritis (inflammation of small intestine)
What are the 4 life stages of hookworms?
- egg
- rhabditiform larva
- filariform larva (2x as big)
- adult
How can you tell female vs male hookworms apart?
Males are smaller, and have a blunt end with a “copulatory bursa”
T/F
hookworms generally don’t cause any symptoms
true
except very heavy infections
Describe some symptoms that hookworms can cause
- typically only symptomatic with very heavy infections
- iron deficiency/ blood in stool b/c of blood loss
- ground itch at attachment site
- respiratory issues as it migrates through lungs
- wakana syndrome (nausea etc) if orally ingested
T/F
Hookworms don’t need mechanisms to avoid the host immune system because they’re intracellular
false
they’re extracellular and need strategies to avoid the immune system
Describe the immune response that follows hookworm infection in the human skin
Elicits a rapid response
- Neutrophils (NETS)= white blood cells that the human body releases. These decrease the fitness of the larva and potentially slows migration
BUT - Larva release DNase= degrades DNA of the NETS, reducing number of neutrophils
Give 4 methods of decreasing hookworm spread
- limit time spent barefoot
- don’t use raw feces as fertilizer
- increase sanitation
- deworm pets often
t/f
dogs naturally acquire resistance to subsequent infections of hookworms
true
Is there a current hookworm vaccine for dogs?
No
There was one on the market for ~30 years, but removed because we didn’t know enough about it –> might’ve just been forcing the hookworms to go deeper into skin
Is there a current human vaccine for hookworm?
No, very hard to develop b/c human immunity to infection isn’t great
- there are a few human vaccines in the works though (eg. digestion enzyme APR 1)
What is a nickname of the hookworm? How did it get this nickname?
“the germ of laziness”
- Exhaustion from anemia caused by hookworms was perceived as laziness
- This became a stereotype in the southern US (likely ~40% of the population was infected)
What did the Rockefellers do for hookworm mitigation?
T/F
nematodes are motile
true
Ancylostoma and necator use the “ambusher” strategy for host finding. Describe this
- less motile
- “nictate” when hosts emit cues (larva stand up and ‘wave’ to increase chance of attaching)
Which host finding strategy do strongyloides use?
cruisers
- more motile
Ha. contortus is repelled by the odor of ____ and attracted to _____
explain why for each
sweat
- b/c don’t want to be on the skin
- fresh grass extracts
- b/c want to be consumed by livestock= live on grass
Explain how Ha. contortus can use sensory cues to move around
Phototaxis= moves vertically on plants during grazing periods
Hygrotaxis= move down plants to damp soil when grazers are not out
Skin- penetrating nematodes migrate towards ___ and increase crawling speed.
Do passively-ingested nematodes do this?
heat
no
