NEMATODES Flashcards
(96 cards)
1
Q
General characteristics: • Roundworms, elongated, cylindrical in shape with bilateral symmetry and unsegmented
Have complete digestive system, no circulatory system
- Sensory organs known as chemoreceptors (phasmids)
- Provided with separate sexes although some are parthogenetic or parthogenic (S. stercoralis)
- Female maybe oviparous or viviparous
A
CLASS
NEMATODA
2
Q
Developmental stages (5) of Nematode
A
o Egg
o Larva (1-‐3)
o Adult
3
Q
Intestinal Nematodes: • Classification according to source of infection: SOIL TRANSMITTED HELMINTHES (STH)
A
o Ascaris lumbricoides
o Trichuris trichuria
o Hookworms
o Strongyloides stercoralis
4
Q
CAUSATIVE AGENT: _____________________-
- Largest and most common nematode (roundworm) parasitizing the human intestine
- Common name: giant intestinal roundworm
- Habitat: small intestine •
Diagnostic stage: ova, adult
• MOT: ingestion
A
Ascaris lumbricoides
5
Q
Infective stage of ASCARIASIS?
A
Infective stage: fully embryonated egg
6
Q
Adult
o Freely moving; restless
o Female: 20 to 35 cm;
paired reproductive organ in posterior 2/3
o Male: 15 to 30 cm;
ventrally curved posterior end with two spicules o White, cream or pinkish yellow when fresh
o Head is provided with 3 lips and a triangular buccal cavity (trilobite)
A
ADULT ASCARIS
7
Q
A
Adult
A. lumbricoides:
tri-‐radiate
lips
8
Q
A
Cross-‐section of adult male and female: male-‐ gut, seminal vesicle, testes, vas deferens; female-‐gut, ovaries, uteri
9
Q
Ascaris Eggs:
o Passed in the feces of infected persons
o Either fertile or infertile
o Viability on soils: ____________
A
2 years
10
Q
A
A. Embryonated egg: INFECTIVE STAGE; contains larva inside
11
Q
A
B. Fertilized decorticated egg: DIAGNOSTIC STAGE; has a single mass of germ cells but no outer albuminous mammillated layer
12
Q
A
Fertilized corticated egg: DIAGNOSTIC STAGE;
3 layers:
o outer albuminous mammillated coat
o middle glycogen membrane
o inner lipoidal vitelline layer
13
Q
A
Unfertilized egg: DIAGNOSTIC STAGE;
- elongated in shape,
- contains refractile lecithin granules,
- lacks lipoidal membrane and
- has glycogen layer
14
Q
An ascaris female may produce approximately ________________which are passed with the feces 2 Unfertilized eggs may be ingested but are not infective.
A
200,000 eggs per day,
15
Q
Fertile ascaris eggs embryonate and become infective after_____________, depending on the environmental conditions (optimum: moist, warm, shaded soil).
A
18 days to several weeks 3
16
Q
Between___________ are required from ingestion of the infective eggs of ascaris to oviposition by the adult female.
A
2 and 3 months
17
Q
May cause stunted growth
- Usually no acute symptoms
- High worm burdens may cause abdominal pain and intestinal obstruction
- Migrating adult worms may cause symptomatic occlusion of the biliary tract or oral expulsion •
A
ASCARIS
18
Q
During the lung phase of larval migration, pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis -‐ ____________) • Pneumonia, cough, fever, eosinophilia during larval migration
- Vomiting and abdominal pain (most frequent complaint)
- Biting & pricking of intestinal mucosa may irritate nerve endings and result in intestinal spasm leading to intestinal obstruction and possibly, perforation
- Adult worms usually cause no acute symptoms (10-‐20 worms) -‐Unnoticed unless stool examinatio
A
Loeffler’s syndrome
19
Q
If symptoms occur: -‐
They can be light only -‐______________
Moderate infection: -‐________________
Heavy infections: -‐ Intestinal blockage -‐Impair growth and cognition in children Other symptoms: -‐ Cough
A
Abdominal discomfort
Lactose intolerance
20
Q
Migrating adult worms may cause:
o BilliaryAscariasis §
thru Ampulla Vater §
(+) severe colicky abdominal pain o Acute appendicitis
o Pancreatitis o Peritonitis
o Pulmonary symptoms -‐ Loeffler’s syndrome
A
ASCARIs
21
Q
What are the symptoms during larval migration
A
Pneumonia, cough, fever, eosinophilia during larval migration
- Vomiting and abdominal pain (most frequent complaint)
- Biting & pricking of intestinal mucosa may irritate nerve endings and result in intestinal spasm leading to intestinal obstruction and possibly, perforation
- Adult worms usually cause no acute symptoms (10-‐20 worms) -‐Unnoticed unless stool examination
22
Q
Vomiting and abdominal pain (most frequent complaint) in ascariasis
- Biting & pricking of intestinal mucosa may irritate nerve endings and result in intestinal spasm leading to intestinal obstruction and possibly, perforation
- Adult worms usually cause no acute symptoms (10-‐20 worms) -‐Unnoticed unless stool examination
A
Vomiting and abdominal pain
23
Q
If symptoms occur: -‐ They can be light only -‐ ______________
A
Abdominal discomfort
24
Q
The moderate infection in ascariasis is determined by ___________
A
Moderate
infection:
-‐Lactose
intolerance
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In asacaris Heavy infections: -‐ Intestinal blockage -‐\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Impair growth and cognition in children
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Migrating adult worms may cause: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
o BilliaryAscariasis § thru Ampulla Vater § (+) severe colicky abdominal pain
o Acute appendicitis
o Pancreatitis
o Peritonitis
o Pulmonary symptoms -‐ Loeffler’s syndrome • Serious and fatal effects due to erratic migration of adult worms
o May be regurgitated and vomited, escape through nostrils, inhaled into trachea (rare)
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ASCARIS
o less sensitive o 2mg of feces in a drop of NSS on a glass slide with cover slip on top; LPO under microscope
DFS
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ASCARIS
\_\_\_\_\_\_\_\_\_\_\_\_ smear method
o **20-‐60mg of feces**
o Purely qualitative
o Mass examination of feces for diagnosis of Ascaris infection
Kato technique or cellophane thick
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\_\_\_\_\_\_\_\_\_\_\_\_\_
o Modified Kato technique
o Amount of feces to be examined is measured
o Used to quantify number of eggs, therefore a quantitative technique
o Used to determine egg reduction rate (ERR) § Egg count/ gram of feces §
To determine intensity of infection
Kato-‐katz technique
30
\_\_\_\_\_\_\_\_\_\_\_\_\_- are useful for individual and mass screening in schools and community; low cost; easy to maintain.
Kato technique & Kato Katz
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ASCARIS
TREATMENT \_\_\_\_\_\_\_\_\_\_o DRUG OF CHOICE
o **400mg single dose** (**200mg for children \<2yo**)
• Mebendazole
o 500mg single dose
• Pyrantelpamoate
o 10mg/kg single oral dose
**• Ivermectin**
Has recently been shown to be as effective as albendazole **if given at dose of 200ug/kg single dose \*known to be teratogenic, not be given to pregnant women**
• Albendazole
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Geographic Distribution
o Areas with warm, moist climates and are widely overlapping
o Most common in **tropical and subtropical** areas where **sanitation and hygiene are poor**
* Mostly young children (Phil – 80-‐90% risk of public elementary school children)
* Associated with poor personal hygiene, poor sanitation, and in places where human feces are used as fertilizer
* Endemic in Southeast Asia, Aftrica, Cetral and South America
Ascaris
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HOW TO DO PREVENTION & CONTROL IN ASCARIS
* **Avoid ingesting soil** that may be contaminated with human feces
* **Wash hands** with soap and warm water before handling food
* Teach children the importance of washing hands
* Wash, peel, or cook all raw vegetables and fruits before eating, particularly those that have been grown in soil that has been fertilized with manure • Mass chemotherapy done periodically, 1-‐3x a year.
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Common name: **“human whipworm”**
Trichuris trichuria
35
What is the shape of Trichuris eggs?
barrel shape
36
Where is the natural habitat of Trichuris trichuria?
• Natural habitat: cecum
37
Does Trichuris trichuria have a pulmonary phase? T or F
• No pulmonary phase
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What causes anemia in Trichuris trichuria?
• Blood-‐sucker-‐ may cause anemia
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What type of stool do patients with Trichuris have ?
* Watery diarrhea
* Dysentery – bloody stool
40
What happens when there is hyperinfection in Trichuris patients?
• Hyperinfection: rectal prolapse
41
What is the diagnostic stage of Trichuris?
• Diagnostic stage: unembryonated egg
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What is the infective stage of Trichuris?
• Infective stage: **fully embryonated egg** •
43
What is the MOT of Trichuris?
MOT: ingestion
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What is the \_\_\_\_\_\_\_\_\_\_\_-‐ arrangement of somatic cell in cross section where the cells are small, numerous, and closely packed in a narrow zone
• Holomyarian
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A. Adult male T. trichuria
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B. Adult male T. trichuria
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T. trichuria egg:
50-‐55 x 20-‐25mm;
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football-‐shaped,
thick-‐shelled and
with a **pair of polar “plugs”** at each end (bipolar plugs), **(lemon-‐shaped** with **plug like translucent polar prominence)**
Trichuris eggs
49
Coiled end with a single spicule and retractile sheath
Male adult worm of Trichuris
50
Bluntly
rounded
posterior
end
adult Trichuri female egg
Note: bigger than male
51
What is the life cycle of T. trichuria
The unembryonated eggs are passed with the stool
1. In the soil, the eggs develop into a **2-‐cell stage**
2, an advanced cleavage stage
3, and then they **embryonate**
4; eggs become **infective in 15 to 30 days**.
After ingestion **(soil-‐contaminated hands or food**), the eggs **hatch in the small intestine**, and release larvae
5 that mature and establish themselves as adults in the colon . The adult worms (approximately 4 cm in length) **live in the cecum** and **ascending colon**
6. The **adult worms are fixed in that location**, with the anterior portions threaded into the mucosa.
The females begin to **oviposit 60 to 70 day**s after infection. Female worms in the cecum shed between **3,000 and 20,000 eggs per day**.
The life span of the adults is about 1 year.
52
What is the life span of Adult T.trichuris?
The life span of the adults is about 1 year.
53
PATHOGENESIS AND CLINICAL MANIFESTATIONS of T. Trichuris
* Most frequently asymptomatic
* Heavy infections (especially in small children) can cause gastrointestinal problems:
o Abdominal
pain
o Diarrhea
(watery)
o **RECTAL
PROLAPSE**
o Possibly
growth
retardation
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• Anterior portion of the worms can cause\_\_\_\_\_\_\_\_\_\_\_\_
petechial hemorrhages which may predispose to amebic dysentery \*Enterorrhagia-‐ bleeding of the intestines\*
55
The lumen of the appendix may be filled with worms, and consequently irritation and inflammation may lead to appendicitis or granulomas
* The mucosa is hyperemic and edematous
* Symptomatic-‐ infections with \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
over 5 000 T. trichuria eggs per gram of feces
56
What is the diagnostic modality of T.trichuris
DIAGNOSIS]
**Microscopy**
• Because eggs may be **difficult to find in light infections**, a **concentration procedure is recommended** • Because the severity of symptoms depend on the worm burden, quantification (e.g. with the **Kato-‐Katz technique) can prove useful**
57
TREATMENT\_\_\_\_\_\_ what is the Drug of choice of Trichuris infection?
o Contraindications: hypersensitivity and early pregnancy
• Mebendazole
Note
• Albendazole
o Alternative drug
58
EPIDEMIOLOGY
* The **third most common** round worm of humans
* More frequent in areas with **tropical weather** and **poor sanitation practices**, and among children **5 to 15 years old**
* It is estimated that 800 million people are infected worldwide
* This also occurs in the southern United States
Trichuris Trichuria
Note: **T**hird for **T**richuris
T for T
59
What are the factors in Trichuris transmission?
. • Factors affecting transmission are:
o Indiscriminate defecation of children around yards
o Frequent contact between fingers and soil among children at play
o Poor health education
o Poor hygiene
60
What are the two hookworms that infect the humans?
CAUSATIVE
AGENTS:
**Ancylostoma
duodenale**
and
**Necator
americanus**
61
Do hookworms have pulmonary phase?
With
pulmonary
phase
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These worms are also **soil-transmitted helmiths. **They are **blood-‐sucker (macrocytic hypochromic anemia)** attach to the mucosa of the **small intestine**
hookworms
63
What is the most common hookworm in the philippines?
• Most common hookworm in the Philippines: **Necator americanus**
64
Which hookworm causes deeper injury?
• Deeper injury: **Ancylostoma (3-‐4 times blood loss)** • **Ancylostoma braziliense (cats**)
**• Ancylostoma caninum (dogs**)
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Where is the habitat of hookworms?
• Habitat: **lumen of small intestine**
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What is the diagnostic stage of hookworms: egg • Infective stage: filariform larva • MOT: skin penetration
egg
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What is the infective stage of hookworms?
• Infective stage: filariform larva
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What is the MOT of hookworms?
• MOT: skin penetration
69
o Small, **cylindrical**, **fusidorm**, **grayish white**
o Female: **9-‐11mm x 0.35mm;**
Male 5-‐9mm x 0.30mm and **posterior end has broad, membranous caudal bursa with rib-‐like rays used for copulation**
o **Head is curved opposite** to the curvature of the body o Buccal capsule – ventral pair of semilunar cutting plates
o More serious concern than A. Duodenale
Necator americanus
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o Slightly larger than N. Americanus
o **Single paired male and female repro organ**
o Head continues in the same direction as the curvature of the body
o Buccal capsule – **2 pairs of curved ventral teeth**
Ancylostoma duodenale
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A. Necator americanus buccal cavity: **semilunar cutting plates**
**Nmemonics: N**ecator to semilu**N**ar
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B. Ancylostoma duodenale buccal cavity: **2 pairs of ventral teeth**
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C. Ancylostoma caninum buccal cavity**: 3 pairs of ventral teeth**
**C**aninum : letter **C** is the **3**rd alphabet : **3 pairs**
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D. Ancylostoma baziliensis buccal cavity: **2 pairs of ventral teeth (median teeth smaller)**
nmemonic : **B : 2nd** letter in alphabet: **B**entral!!
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Hookworm egg: **blunty rounded ends**,
**single thin transparent hyaline shell with blastomeres;**
NOTE :DIAGNOSTIC STAGE \*N. Americanus and A. duodenale are **indistinguishable in this stage\***
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Hookworm **rhabditiform larva (L2**):
short and stout,
open-‐mouthed, feeding stage
\*Should be differentiated from **Strongyloides L1 IF** found in stool **via Harada Mori\***
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C. Hookworm filariform larva (L3): pointed tail, closed mouth, sheathed, non-‐feeding stage;
## Footnote
**INFECTIVE STAGE \*Can differentiate N. Americanus and A. duodenale\***
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What is the life cycle of hookworms?
1 Eggs are passed in the stool , and under favorable conditions (**moisture, warmth, shade**), larvae hatch in 1 to **2 days.** The released rhabditiform larvae grow in the **feces and/or the soil**.
2 After **5 to 10 days** (and **two molts**) they become **filariform (third-‐stage)** larvae that are **infective 3.** These infective larvae **can survive 3 to 4 weeks** in favorable environmental conditions. On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs.
They **penetrate into the pulmonary alveoli**, ascend the bronchial tree to the pharynx, and are swallowed
4. The l**arvae reach the small intestine**, where they **reside and mature into adults**. Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host
5. **Most adult worms are eliminated in 1 to 2 years,** but the **longevity may reach several years**.
Some **A. duodenale larvae,** following penetration of the host skin**, can become dormant** (in the intestine or muscle). In addition, **infection by A. duodenale** may probably also occur by the **oral and transmammary route**. **N. americanus, however, requires a transpulmonary migration phase.**
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The Life Cycle of A. braziliense and A. caninum:
**CUTANEOUS LARVAL MIGRANS** Cutaneous larval migrans (also known as **creeping eruption)** is a **zoonotic infection with hookworm species** that **do not use humans as a definitive host**, the **most common being A. braziliense and A. caninum.**
80
The normal definitive hosts for these Cutaneous
larval
migrans species are \_\_\_\_\_\_\_\_\_\_.
dogs and cats
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The life cycle of cutaneous larval migrans?
The cycle in the definitive host is **very similar to the cycle for the human species**.
Eggs are passed in the stool
1. Under favorable conditions **(moisture, warmth, shade**), **larvae hatch in 1 to 2 days**.
The released rhabditiform larvae grow in the feces and/or the soil
2. After **5 to 10 days** (and **two molts**) they become **filariform (third-‐stage)** larvae that are infective
3. These infective larvae can survive **3 to 4 weeks in favorable environmental conditions.** On contact with the animal host
4. The **larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs.**
They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed.
The larvae reach the **small intestine,** where they **reside and mature into adults.** Adult worms live in the **lumen of the small intestine,** where they attach to the **intestinal wall**.
**Some larvae become arrested** in the **tissues,** and **serve as source of infection for pups** via **transmammary (and possibly transplacental**) routes 5. ***Humans may also become infected when filariform larvae penetrate the skin***
6. With most species, the larvae cannot mature further in the human host, and migrate aimlessly within the epidermis, sometimes as much as several centimeters a day. Some larvae may persist in deeper tissue after finishing their skin migration.
82
What is the pathogenesis of HOOKWORM?
PATHOGENESIS AND CLINICAL MANIFESTATION
* **Iron deficiency anemia** (caused by blood loss at the site of intestinal attachment of the adult worms) is the **most common symptom**
* Can be accompanied by **cardiac complications**
* **Gastrointestinal and nutritional/metabolic** • symptoms can also occur
* Local skin manifestations (**'ground itch'**) can occur during **penetration by the filariform (L3) larvae**
* Respiratory symptoms during pulmonary migration of the larvae
* Cutaneous larva migrans
o Also known as **ground itch**
o A migrating larva causes an **intensely pruritic serpiginous track** in the **upper dermis**
o Most common manifestation of zoootic infection with **animal hookworm**
* Less commonly, **larvae may migrate to the bowel lumen and cause an eosinophilic enteritis**
* In some cases of diffuse **unilateral subacute retinitis, single larvae compatible in size to A. caninum have been visualized in the affected**
83
What is the common symptom in hookworm infection?
**Iron deficiency anemia** (caused by blood loss at the site of intestinal attachment of the adult worms) is the most common symptom
84
Local skin manifestations (**'ground itch')** can occur during penetration by the **filariform (L3) larvae**
HOOKWORMS
85
Skin
o Maculopapular lesions and localized erythema due to penetration of filariform larvae
o Ground itch or dew itch especially on dewy morning
• Lungs
o Bronchitis and pneumonitis during larval migration
• Small intestine (maturation site of worm)
o Abdominal pain o Steatorrhea o Diarrhea with blood and much
o Progressive, secondary, microcytic, hypochromic anemia of the IDA type (due to continuous blood loss) o Hypoalbuminemia § due to combined loss of blood, lymph, and protein
HOOKWORM
86
\_\_\_\_\_\_\_\_\_\_
* Other symptoms: exertional dyspnea, weakness, dizziness, lassitude
* Signs: rapid pulse, edema, albuminuria
* Usually chronic moderate or heavy infection; often no acute symptoms
* In general, prognosis of hookworm is good
Cutaneous larval migrans
87
HOOKWORM
o \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_-‐ether concentration
o Increase positive findings
o Recommended for determining **whether stool is egg positive/negative**
Concentration methods
88
Culture
o \_\_\_\_\_\_\_\_\_\_\_\_\_\_-
o Allow hatching of larva from eggs on strips of filter paper, one end immersed in water
o Identification of f**ilariform larvae**
Harada-‐Mori
89
TREATMENT HOOKWORM
• \_\_\_\_\_\_\_\_\_\_\_\_\_\_-
o DRUG OF CHOICE
o Larvicidal and ovicidal
o 400mg **single dose** for adults and \>2y/o
o Not recommended for pregnant women
•
Albendazole
## Footnote
Mebendazole
o 500mg single dose o Not recommended for \<2y/o \*both blocks the uptake of glucose by most intestinal and tissue nematodes
* Pyrantel Pamoate
* Iron supplementation – correction of anemia
* ** In countries where hookworm is common and reinfection is likely, light infections are often not treated**
90
EPIDEMIOLOGY
* \_\_\_\_\_\_\_\_\_\_\_is the second most common human helminthic infection (after ascariasis)
* are worldwide in distribution, mostly in areas with moist, **warm climate**
* Both N. americanus and A. duodenale are found in Africa, Asia and the Americas
* Necator americanus **predominates in the Americas and Australia**
* **Only A. duodenale is found in the Middle East,** North Africa and southern Europe
\*A. duodenale – **prevalent Europe and Southeast Asia** \*N. Americanus– **prevalent Tropical Africa and America**
• Greater in agricultural areas (farmers)
Hookworm
91
• Factors contribute to transmission:
o Eggs and larvae – damp, sandy or friable soil with decaying vegetation; 24-‐32oC
o Fecal population of the soil o Contact between infected soil and skin/mouth
92
Diagnosis of Intestinal Helminth Infections:
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
o worst diagnostic tool for helminthes
o amount: 1-‐2mg of stool
o lack of sensitivity for detection of common worm eggs
o **most useful in detection of intestinal protozoan trophozoites**
• Stool examination/Fecalysis
93
o microscopic examination of a fixed
quantity of fecal material (40-‐50mg)
o enables semi-‐quantitative diagnosis
o based on the number of eggs in feces
o greater egg count=greater number of female worms
o **most useful tool for surveillance of schistosome**
Kato Katz Technique
94
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
o examines 1g of feces
o **best stool examination for screening foodhandlers**
o **most useful for detection of protozoan cysts**
Formalin Ether Concentration Technique
95
What is the treatment hookworms?
Treatment:
* Albendazole (400mg; 200 mg if \<2 years old)
* Mebendazole
* Results:
o Improved iron stores and hemoglobin levels o Improved growth
o Improved food intak
e o Improved cognitive performance
o Reduced incidence of complications
96
