Nematodes- infective larvae

Question 1

What are the similarities between Ancylostoma duodenale and Necator americanus?

Answer 1

similar life cycle, infect host by penetrating skin (not orally!)

Question 2

What are the differences between Ancylostoma duodenale and Necator?

Answer 2

A. duodenale can also be transmitted orally and trans-mammary. N. americanus requires a trans-pulmonary stage

Question 3

Where are hookworms found?

Answer 3

North and South America (earliest in Brazil) and Europe +

Question 4

What are the three divisions of the order Strongylida?

Answer 4

Strongyloidea (man hookworms), Trichostrongyloidea (intestinal hookworms in domestic animals), Metasrongyloidea (lungworms in domesticated animals)

Question 5

What are the two hookworm species to cause disease in man and where are they found?

Answer 5

Ancylostoma duodenale Mediterranean, Southeast Asia, Southern America (scattered) Necator americanus Africa, Asia, Europe, predominantly in the Americas and Australia. South & Southwestern US

Question 6

What happens if a larva infects humans?

Answer 6

they can penetrate the skin and cause a localized pathology, but they cannot complete their life cycle

Question 7

Which human hookworm species is larger?

Answer 7

Ancylostoma duodenale is a bit bigger, usually around 0.5-1.5mm

Question 8

What are the characteristics of the eggs?

Answer 8

bluntly rounded, thin shelled, almost indistinguishable between different species, Ancylostoma eggs slightly larger than Necator eggs will not bother to differentiate the species because it is not efficient

Question 9

What feature does the male have to aid with copulation?

Answer 9

copulatory bursa at the anterior end

Question 10

What distinguishing feature do the female worms have?

Answer 10

a vulva near the centre of the body

Question 11

What are the two more common species of hookworms where humans are not the definitive host?

Answer 11

A. braziliense and A. caninum. Cause cutaneous larval migrans, when the larva penetrates the skin and migrates through the body

Question 12

Describe adult hookworm pathology

Answer 12

attach to intestinal wall via bucal capsules and suck blood. heavy infections can leads to chronic iron deficiency anaemia

Question 13

Describe larvae hookworm pathology

Answer 13

Ground itch: allergic rxn at site of penetration common in N americanus infection cough and pneumonitis: may result when larva get into lungs and travel up the trachea

Question 14

What is the most common way humans become infected?

Answer 14

walking barefoot in an infected area

Question 15

Can you become auto-infected from hookworm?

Answer 15

no

Question 16

Describe the path the larva takes after skin penetration

Answer 16

carried in the veins to the heart, then to the lungs, where they penetrate pulmonary alveoli. They ascend up the bronchial tree to the pharynx, and are swallowed. They reach the small intestine and mature into adults. Larva can become dormant after penetrating the skin

Question 17

How can hookworm infection be diagnosed?

Answer 17

microscopic examination of eggs in the stool. to know the genus, the eggs need to be cultured. the two human species can be distinguished microscopically but this is not often done

Question 18

How can hookworm infection be treated?

Answer 18

benzimidazoles: albendazole and mebendazole

Question 19

How do benzimidazoles work?

Answer 19

binds beta-tubulin, so that microtubules cannot be synthesized. affects glucose and other nutrient uptake, leading to immobilization and death

Question 20

When is albendazole effective?

Answer 20

in the intestinal stage and when the larva is migrating under the skin

Question 21

Where are Strongyloides stercoralis (threadworm) found?

Answer 21

tropical and subtropical areas, but also some cases in temperate Southern United States

Question 22

What is the niche of Strongyloides stercoralis?

Answer 22

mucosa of small intestine or free-living

Question 23

Which sex of threadworm is larger?

Answer 23

the female

Question 24

Describe the threadworm eggs

Answer 24

ellipsoid in shape, thin wall containing a larva

Question 25

What drug is used to treat Strongyloides stercoralis infection?

Answer 25

ivermectin interferes with nervous system and muscle function (enhancing inhibitory neurotransmission). Drug binds and activates glutamate-gated chloride channels