NEMATODES Flashcards
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
CLASS
NEMATODA
Developmental stages (5) of Nematode
o Egg
o Larva (1-‐3)
o Adult
Intestinal Nematodes: • Classification according to source of infection: SOIL TRANSMITTED HELMINTHES (STH)
o Ascaris lumbricoides
o Trichuris trichuria
o Hookworms
o Strongyloides stercoralis
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
Ascaris lumbricoides
Infective stage of ASCARIASIS?
Infective stage: fully embryonated egg
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)
ADULT ASCARIS
Adult
A. lumbricoides:
tri-‐radiate
lips
Cross-‐section of adult male and female: male-‐ gut, seminal vesicle, testes, vas deferens; female-‐gut, ovaries, uteri
Ascaris Eggs:
o Passed in the feces of infected persons
o Either fertile or infertile
o Viability on soils: ____________
2 years
A. Embryonated egg: INFECTIVE STAGE; contains larva inside
B. Fertilized decorticated egg: DIAGNOSTIC STAGE; has a single mass of germ cells but no outer albuminous mammillated layer
Fertilized corticated egg: DIAGNOSTIC STAGE;
3 layers:
o outer albuminous mammillated coat
o middle glycogen membrane
o inner lipoidal vitelline layer
Unfertilized egg: DIAGNOSTIC STAGE;
- elongated in shape,
- contains refractile lecithin granules,
- lacks lipoidal membrane and
- has glycogen layer
An ascaris female may produce approximately ________________which are passed with the feces 2 Unfertilized eggs may be ingested but are not infective.
200,000 eggs per day,
Fertile ascaris eggs embryonate and become infective after_____________, depending on the environmental conditions (optimum: moist, warm, shaded soil).
18 days to several weeks 3
Between___________ are required from ingestion of the infective eggs of ascaris to oviposition by the adult female.
2 and 3 months
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 •
ASCARIS
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
Loeffler’s syndrome
If symptoms occur: -‐
They can be light only -‐______________
Moderate infection: -‐________________
Heavy infections: -‐ Intestinal blockage -‐Impair growth and cognition in children Other symptoms: -‐ Cough
Abdominal discomfort
Lactose intolerance
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
ASCARIs
What are the symptoms during larval migration
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
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
Vomiting and abdominal pain
If symptoms occur: -‐ They can be light only -‐ ______________
Abdominal discomfort
The moderate infection in ascariasis is determined by ___________
Moderate
infection:
-‐Lactose
intolerance
In asacaris Heavy infections: -‐ Intestinal blockage -‐_____________________
Impair growth and cognition in children
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)
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
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
_____________
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
_____________- are useful for individual and mass screening in schools and community; low cost; easy to maintain.
Kato technique & Kato Katz
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
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
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.
Common name: “human whipworm”
Trichuris trichuria
What is the shape of Trichuris eggs?
barrel shape
Where is the natural habitat of Trichuris trichuria?
• Natural habitat: cecum
Does Trichuris trichuria have a pulmonary phase? T or F
• No pulmonary phase
What causes anemia in Trichuris trichuria?
• Blood-‐sucker-‐ may cause anemia
What type of stool do patients with Trichuris have ?
- Watery diarrhea
- Dysentery – bloody stool
What happens when there is hyperinfection in Trichuris patients?
• Hyperinfection: rectal prolapse
What is the diagnostic stage of Trichuris?
• Diagnostic stage: unembryonated egg
What is the infective stage of Trichuris?
• Infective stage: fully embryonated egg •
What is the MOT of Trichuris?
MOT: ingestion
What is the ___________-‐ arrangement of somatic cell in cross section where the cells are small, numerous, and closely packed in a narrow zone
• Holomyarian
A. Adult male T. trichuria
B. Adult male T. trichuria
T. trichuria egg:
50-‐55 x 20-‐25mm;
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
Coiled end with a single spicule and retractile sheath
Male adult worm of Trichuris
Bluntly
rounded
posterior
end
adult Trichuri female egg
Note: bigger than male
What is the life cycle of T. trichuria
The unembryonated eggs are passed with the stool
- 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
- The adult worms are fixed in that location, with the anterior portions threaded into the mucosa.
The females begin to oviposit 60 to 70 days 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.
What is the life span of Adult T.trichuris?
The life span of the adults is about 1 year.
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
• Anterior portion of the worms can cause____________
petechial hemorrhages which may predispose to amebic dysentery *Enterorrhagia-‐ bleeding of the intestines*
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
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
TREATMENT______ what is the Drug of choice of Trichuris infection?
o Contraindications: hypersensitivity and early pregnancy
• Mebendazole
Note
• Albendazole
o Alternative drug
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: Third for Trichuris
T for T
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
What are the two hookworms that infect the humans?
CAUSATIVE
AGENTS:
Ancylostoma
duodenale
and
Necator
americanus
Do hookworms have pulmonary phase?
With
pulmonary
phase
These worms are also **soil-transmitted helmiths. **They are blood-‐sucker (macrocytic hypochromic anemia) attach to the mucosa of the small intestine
hookworms
What is the most common hookworm in the philippines?
• Most common hookworm in the Philippines: Necator americanus
Which hookworm causes deeper injury?
• Deeper injury: Ancylostoma (3-‐4 times blood loss) • Ancylostoma braziliense (cats)
• Ancylostoma caninum (dogs)
Where is the habitat of hookworms?
• Habitat: lumen of small intestine
What is the diagnostic stage of hookworms: egg • Infective stage: filariform larva • MOT: skin penetration
egg
What is the infective stage of hookworms?
• Infective stage: filariform larva
What is the MOT of hookworms?
• MOT: skin penetration
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
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
A. Necator americanus buccal cavity: semilunar cutting plates
Nmemonics: Necator to semiluNar
B. Ancylostoma duodenale buccal cavity: 2 pairs of ventral teeth
C. Ancylostoma caninum buccal cavity: 3 pairs of ventral teeth
Caninum : letter C is the 3rd alphabet : 3 pairs
D. Ancylostoma baziliensis buccal cavity: 2 pairs of ventral teeth (median teeth smaller)
nmemonic : B : 2nd letter in alphabet: Bentral!!
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*
Hookworm rhabditiform larva (L2):
short and stout,
open-‐mouthed, feeding stage
*Should be differentiated from Strongyloides L1 IF found in stool via Harada Mori*
C. Hookworm filariform larva (L3): pointed tail, closed mouth, sheathed, non-‐feeding stage;
INFECTIVE STAGE *Can differentiate N. Americanus and A. duodenale*
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
- 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 with resultant blood loss by the host
- 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.
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.
The normal definitive hosts for these Cutaneous
larval
migrans species are __________.
dogs and cats
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
- 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
- After 5 to 10 days (and two molts) they become filariform (third-‐stage) larvae that are infective
- These infective larvae can survive 3 to 4 weeks in favorable environmental conditions. On contact with the animal 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.
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
- 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.
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
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
Local skin manifestations (‘ground itch’) can occur during penetration by the filariform (L3) larvae
HOOKWORMS
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
__________
- 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
HOOKWORM
o ________________-‐ether concentration
o Increase positive findings
o Recommended for determining whether stool is egg positive/negative
Concentration methods
Culture
o ______________-
o Allow hatching of larva from eggs on strips of filter paper, one end immersed in water
o Identification of filariform larvae
Harada-‐Mori
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
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**
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
• 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
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
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
________________
o examines 1g of feces
o best stool examination for screening foodhandlers
o most useful for detection of protozoan cysts
Formalin Ether Concentration Technique
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
