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Intestinal Nematodes > Hookworms > Flashcards

Hookworms Flashcards

1
Q

Hookworms are geohelminths of two main species

A

Ancylostoma duodenale (hooked mouth)
Necator Americans( American murderer)

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2
Q

Epidemiology of hookworms

A

Ancylostoma duodenale ( old world) was prevalent along Mediterranean coast of Europe and Africa and northern India, China and Japan
Necator Americanus ( new world hookworm) was prevalent in central and south America, Central and south Africa Southern India and southern Pacific region
Hookworm disease is prevalent throughout the tropics and subtropics affecting > 900million people

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3
Q

Conditions favoring hookworm infection

A

Presence and dispersal of eggs in soil due to improper sanitation ( open defecation)
Favorable environmental factors ( temperature 23-33° c ) sandy/ loamy soil with sufficient moisture allowing growth of worm in soil
Opportunity for larva to infect people through exposed skin surfaces coming into contact with contaminated soil

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4
Q

Which of the two is more pathogenic ?

A

Ancylostoma duodenale (ancylostomiasis)

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5
Q

Adult worm habitat of ancylostoma duodenale

A

Small intestine mainly the jejunum

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6
Q

T/F:Hookworm is oviparous

A

True

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7
Q

Morphology of A. Duodenale Egg

A

Ovoid or elliptical
Measures 60 by 40um
Colourless, not bile stained.
Is segmented
Surrounded by a thin transparent hyaline shell membrane

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8
Q

A single Ancylostoma duodenale lays ___ eggs daily

A

15000- 30000

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9
Q

Morphology of the adult A duodenale worm

A

Stout cylindrical unsegmented nematodes
Pale pink or greyish white , may appear red due to ingested blood
Body curved(dorsal concave, Ventral convex) with the anterior end constricted and bent in the same direction as the body curvature. Appears like a hook
Has buccal capsule reenforced with chitin carrying 6 teeth
Mouth directed dorsally

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10
Q

Adult A. Duodenale male Is smaller

A

The female is larger

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11
Q

The male A. Duodenale has an umbrella shaped copulatory bursa

A

The female does not

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12
Q

A. Duodenale male genital canal opens into cloaca with anus

A

Female’s vulva opens ventrally @the junction of middle and post 1/3 of the body

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13
Q

A. Duodenale male has two long retractile bristle like copulatory spicules and a single testis

A

Has vagina leading to two coiled ovarian tubes and two uteruses

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14
Q

T/F: the copulatory pair presents a Y shaped appearance

A

True : During copulation the male attaches it’s bursa to the vulva

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15
Q

Less pathogenic

A

Necator Americanus ( Necatororiasis)

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16
Q

Egg morphology

A

Slightly larger but otherwise similar to A. Duodenale

17
Q

Female N. Americanus lays how many eggs

A

6000- 10000

18
Q

Morphology of the adult worm

A

Slightly smaller than A. Duodenale
Anterior end bent in the opposite direction to the body curvature
Have a smaller buccal capsule with 2 pairs of cutting plates
Female vulva is in the middle of the body
Male corpulatory structures fused at the end to form a barbed tip

19
Q

A duodenale male has 2 separate specules.

A

N. Americans male has 2 spicules fused at the tip

20
Q

A. Duodenale female vulva located posteriorly

A

N. Americans female Vulva located anteriorly

21
Q

The life cycle of nematodes:

A

6 stages: egg( embryo) four larval stages( rhabditiform, filariaform) the adult

22
Q

Examples of helminths that require no intermidiate host

A

Ancylostoma duodenale
Necator Americanus
Ascaris lumbricoides.
Truchuris Truchuria
Enterobias vermicularis
Hymenolopis nana

23
Q

Life cycle of hookworms

A
  1. Eggs are passed in stool
  2. Under favourable conditions larvae hatches from eggs in 1 to 2 days to become free living in soil. These rhabditiform larvae feed on bacteria and organic matter in soil
  3. After 5-10 days they become non feeding filariaform ( 3rd stage) that are infective .
  4. On contact with human host they penetrate the skin, and are carried through the veins to the heart and then to the lungs . They penetrate to pulmonary alveoli, ascend the bronchial tree to the pharynx and are swallowed.
  5. The larvae reach the jejunum where they reside and mature into adults. Penetration and attachment to intestinal walls cause blood loss.
24
Q

Hookworms become sexually mature adults____ weeks post penetration

A

5-6 weeks

25
Q

What is hypobiosis

A

Some filariaform larvae of A.duodenale following invasion may penetrate the musculature where they remain dormant, resuming development at a later time

26
Q

Modes/ Routes of infection

A
  1. Penetration of skin- bare foot, hands in farmers and miners
  2. Oral transmission- contaminated water, or vegetables or fruits.
  3. Transmammary and transplacental transmission
27
Q

Transmammary transplacental transmission

A

A. Duodenale may be developmentally arrested and reactivated in pregnancy and infect the infant causing Iron deficiency anaemia and potential mortality

28
Q

Clinical manifestations

Symptoms caused by larvae.

A

Ground itch- severe local itching
A rash may develop
Creeping eruption( cutaneous larva migrans)
Respiratory manifestations- bronchitis, bronchopneumonia, and rarely loeefler syndrome

29
Q

Geohelminths

A

Direct life cycle that requires no intermidiate host or vectors
The parasitic infection ocurs through faecal contamination of soil, foodstuffs and water supply
- Ascaris Lumbricoides
- Truchuria trichuris
- Ancylostoma duodenale
- Necator Americanus
-Strongyloides stercoralis

30
Q

List intestinal and filarial worms under acquisition and geoheminths

A

By ingestion
By skin penetration
Acquisition by insect bite

31
Q

By ingestion:

A

EAT
Enterobias vermicularis
Ascaris lumbricoides
Trichuris trichuria
Toxocara canis/catis
Trichinella spiralis- pork

32
Q

Acquisition by skin penetration:

A

SAN
Strongyloides stercoralis
Ancylostoma duodenale
Necator Americanus

33
Q

Acquisition by insect bite

A

LOW
Loa loa
Onchocercha volvulus
Wuchureria bancrofti

34
Q

Describe the causes,clinical features and diagnosis of loeffler syndrome

A

It is a transient respiratory disorder characterized by accumulation of eosinophils in the lungs

Causes- drugs, parasitic infections that transit through the lungs during their lifecycle( ascaris lumbricoides, necator Americanus , Ancylostoma duodenale, Strongyloides stercoralis, Ancylostoma duodenale, Toxocara canis

Clinical features - cough, fever, malaise, wheezing, dyspnea
Diagnosis - mild eosinophilia, elevated IgE parasites and ova in stool, larave in sputum
Migrating opacity in chest x-ray
Treatment: treat parasitic infection

35
Q

Symptoms caused by adult hookworms

A

Microcytic hypocromic anaemia
Dyspnea-
Palpitations
Dizziness
Severe Hookworm anaemia could lead t cardiac failure
GI symptoms
- epigastric pain
- Dyspepsia
- Vomiting and diarrhoea
- Red/ black stool
Protein deficiency
Puffy face , foot anf ankle edema
Stunted growth, delayed puberty, mental dullness in children

36
Q

How does hookworm infection cause anaemia

A

Hookworms vigoursly suck blood for their food
Chronic haemorrhage from punctured sites in the duodenum as the hookworm saliva contains anticoagulant
Deficient absorption of B12 and and folic acid
Depression of haematopoietic system by deficient intake of proteins
Hypochromic anaemia is caused by IDA while dimorphic anaemia is caused by both iron and B12 deficiency

37
Q

Diagnosis

A

Demonstration of characteristic oval segmented eggs-
Adult hookworms my be seen in faeces

Indirect methods-
Blood exams- microcytic hypocromic anaemia with eosinophilia
Stool exam: presence of occult blood and Charcot layden crystal
Chest x-ray may show migrating larvae

38
Q

Treatment

A

When HB is very low anthelmintic drugs- should not be used before correcting the anaemia

Albendazole
Mebendazole
Pyrantel pamoate
Thiabendazole
Bephenium hydroxynaohthoate us active against Ancylostoma but not against necator

39
Q

Prevention and control of disease

A

Proper sanitation - use of latrines
Proper disposal of waste
Avoid using human waste as fertilizer.
Useof footwear and gloves when in contact with the soil to prevent entry through skin
Treatment of patents and carriers
Education and sensitization

Intestinal Nematodes (8 decks)

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