Seminar 5: Nematodes 1 (Hookworms)

Question 1

List 3 intestinal hookworms for which humans are the main host

Answer 1

• Ancylostoma duodenale
• ancylostoma ceylanicum
• necator americanus

Question 2

Give 1 intestinal hookworm that’s found in dogs and cats

Answer 2

ancylostoma caninum

Question 3

T/F
Intestinal hookworms have the 2nd highest global morbidity burden of any parasite

Answer 3

true

Question 4

Why do hookworms typically live in warm, moist climates?

Answer 4

Because they have a free-living larvae stage, so they require this climate

Question 5

Ancylostoma spp molts __x in the human small intestine, and can live for up to ___ years in there!

Answer 5

2x
10

Question 6

Explain the generalized path of a hookworm in the human host

Answer 6

penetrates skin
heart–> lungs –> trachea–> coughed up & reswallowed –> reaches small intestine (attached to intestinal wall)

Question 7

How is ancylostoma canium transmitted in cats and dogs?

Answer 7

trans mammary transmission (mammary glands)
- accumulate and secrete in milk

Question 8

Can humans get infected with ancylostoma canium?

Answer 8

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)

Question 9

What are the 4 life stages of hookworms?

Answer 9

• egg
• rhabditiform larva
• filariform larva (2x as big)
• adult

Question 10

How can you tell female vs male hookworms apart?

Answer 10

Males are smaller, and have a blunt end with a “copulatory bursa”

Question 11

T/F
hookworms generally don’t cause any symptoms

Answer 11

true

except very heavy infections

Question 12

Describe some symptoms that hookworms can cause

Answer 12

• 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

Question 13

T/F

Hookworms don’t need mechanisms to avoid the host immune system because they’re intracellular

Answer 13

false

they’re extracellular and need strategies to avoid the immune system

Question 14

Describe the immune response that follows hookworm infection in the human skin

Answer 14

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

Question 15

Give 4 methods of decreasing hookworm spread

Answer 15

• limit time spent barefoot
• don’t use raw feces as fertilizer
• increase sanitation
• deworm pets often

Question 16

t/f
dogs naturally acquire resistance to subsequent infections of hookworms

Answer 16

true

Question 17

Is there a current hookworm vaccine for dogs?

Answer 17

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

Question 18

Is there a current human vaccine for hookworm?

Answer 18

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)

Question 19

What is a nickname of the hookworm? How did it get this nickname?

Answer 19

“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)

Question 20

What did the Rockefellers do for hookworm mitigation?

Question 21

T/F
nematodes are motile

Answer 21

true

Question 22

Ancylostoma and necator use the “ambusher” strategy for host finding. Describe this

Answer 22

• less motile
• “nictate” when hosts emit cues (larva stand up and ‘wave’ to increase chance of attaching)

Question 23

Which host finding strategy do strongyloides use?

Answer 23

cruisers
- more motile

Question 24

Ha. contortus is repelled by the odor of ____ and attracted to _____

explain why for each

Answer 24

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

Question 25

Explain how Ha. contortus can use sensory cues to move around

Answer 25

Phototaxis= moves vertically on plants during grazing periods
Hygrotaxis= move down plants to damp soil when grazers are not out

Question 26

Skin- penetrating nematodes migrate towards ___ and increase crawling speed.

Do passively-ingested nematodes do this?

Answer 26

heat

no